Wiadomości Chemiczne, 2004, Vol. 58
Wydział Chemii UJ, ul. Ingardena 3, 30-060 Kraków
Rapid development of different electronic devices was initiated by the discovery of semiconductor-based switch - a transistor in 1948 by J. Bardeen, W.H. Brattain and W.B. Shockley. All electronic devices are based on semiconductor components ever since. Growing demand for bigger memorics and faster processors requires smaller and smaller transistors and other componcnts. Soon the integration scale of elcctronic components will reach the physical limits and further speeding up will not be possible. The only solution of the crisis is application of single molecules and molecular systems for data acquisition, storage, transfer and processing.
There are numerous chemical systems capable of performing logical operations, some of them have already found practical applications. Carbon nanotubes, semiconductor nanocrystals (quantum dots), organic polymers and other supramolecular assemblies can be a basis for construction of chemical switches and logic gates. These devices, however, are chemical versions of traditional semiconductor devices, as the operational principles are imported directly from solid state electronics.
This paper deals with several different approaches towards chemical computing. A large variety of other chemical systems can be used for computing purposes. Some of them are extremely complex (like Aviram-Ratner type devices) and require advanced organic syntheses, other are very simple, like organic dyes and simple transition metal cornplexes. Despite substantial difference in chemical structure, the reactivity of these systems can be described using common language: the Boolean logic.
Any chemical system, which exists in at least two different forms of different optical or electrochemical properties and can be switched with some chemical or physical stimuli (light, redox potential, pH, specific substrate) can be treated as a molecular switch. If the logic structure of the switch is more complex (i.c. there are several different states or several switching stimuli) the system forms a logic gate. The principles of operation of chemical logic gates are identical with those of clectronic logic gates. The input and output signals may have only two values: 0 (OFF, FALSE) or 1 (ON, TRUE). Output signal is a Boolean function of input signals. The basic logic gates are: YES, NOT, OR, NOR, AND, NAND, EX-OR and EX-NOR.
Even the simplest molecular system can exhibit complex logic behaviour, it depends mostly on specific chemical reactivity of the system, proper assignment of the input and output parametcrs and imagination of the experimenter. Some systems are complex enough to emulate not only single gates, but also much larger computing circuits of multilayer parallel architecture. At the same time these systems are closely related to quantum computers: they can be considered as supetposition of different logic gates. Although many of these systems are very impractical, they are guidelines leading to new powerful technologies.
Centrum Badań Molekularnych I Makromolekularnych Polskiej Akademii Nauk
ul. Sienkiewicza 112, 90-363 Łódź, firstname.lastname@example.org
Various techniques are available for the investigation of the solid state. Among them X-ray powder diffraction (XRPD) is a very powerful and widely analytical tool to study powder properties. We can obtain many informations from XRPD:
Zakład Chemii Bionieorganicznej, Wydział Chemii Uniwersytetu im. A. Mickiewicza
ul. Grunwaldzka 6, 60-780 Poznań, email@example.com
The supramolecular chemistry is one of the most intensely developed fields of contemporary chemistry. Supramolecular chemistry may be defined as "chemistry beyond the molccule", bearing on the organized entities of higher complexity that result from association of two or more chemical species hold together by intermolecular forces . Self-assembly involves the direct and spontaneous formation of a closed superstructure or polymer from a mixture of components (organic ligands, salts crystals, and sometimes molecules of solvents). The product exhibits a notable thermodynamic and kinetic stability and its components should contain all the information necessary for a correct assembly to occur. Self-assembly has recently been achieved in many types of organic and inorganic systems [2-I 1]. The inorganic self-assembly involves spontaneous generation of well-defined metallo-supramolecular architectures from mixtures of organic ligands and metal ions. This latter approach has proven particularly successful for the generation of a wide spectrum of architectural topologies such as for example, inorganic double [12-15], triple [16-20] and quadruple  helicates [22-25], rotaxanes [26-29], clusters [30-35], racks [36, 37], ladders [38, 39], cages [40-47], wheels [48, 49], grids [50-90] etc., based on ligand design and the application of suitable coordination geometries for the assembling system. Among them, there is an increasing interest in grid-type complexes, based on ligands containing oligopyridine type of sites and a various d-metal ions. The grids are the thermodynamically most stable motif when metal ions of octahedral coordination geometry are combined with a planar ligand containing tridentate binding sites. Such compounds may exhibit novel physical and chemical properties with interesting and useful potential applications in supramolecular engineering, nanotechnology, biomedical inorganic chemistry, biological catalysis, and in the area of sensors. Transistors incorporating complexes containing cobalt ion bonded to polypyridyl ligands have been reported recently, which is expected to be important in molecular electronics and in the study of the physics of nanoscale systems  The structure of grid-type complexes depends strongly on the ligand substituent, the ligand conformation, the metal ion, the counterion, the solvent, and the reaction conditions.
The paper has been prepared on the basis of literature in the field and results of my own studies. The main contribution is a deseription of synthesis and characterization of the grid-type complexes, taking into regard their untypical properties and structure.
150-525 Wrocław, ul. Gliniana 23/17
2Wydział Chemii Uniwersytetu Wrocławskiego, ul. F. Joliot-Curie 14, 50-383 Wrocław
Polychlorinated biphenyls (PCBs) belong to the family of POPs (Persistent Organic Pollutants) which WHO (World Health Organization), EPA (Environment Protection Agency) and other prestigious institutions pronounced to be a very serious health hazard to humans and animals. It appears, however, that this pronouncement is without solid support in published scientific papers.
PCBs were commercially produced since 1929 for use in electrical capacitors and transformers. It is estimated that a total of 1.5 million tons were made until the production was terminated worldwide in late 1970s. About one half of the produced amount is contained in electrical equipments which are still in use while the other half entered the environment.
The presence of detectable concentrations of PCBs and their persistence in air, water and in living organisms raised concerns that human and animal health may be adversely affected. Health considerations stimulated a very intense research activity which continues unabated from 1966 with the objective of finding evidence of harmful properties of PCBs. Such evidence has not been found yet apart from some minor effects which are without serious consequences.
PCBs appear to be quite harmless chemicals even when handled without proper care. This is evident from the fact that there was no single human death although several cases of poisoning by PCBs were reported. The most publicized are the accidents in Japan and Taiwan which affected about 3000 victims. However, the most serious effects were reversible dermal lesions. The most recent case of accidental poisoning occured in Belgium in 1999. The brouhaha in media was enormous although no human health effects were evident.
The case of PCBs is just another example of chemophobia instigated by irresponsible enviromentalists.
The three decades of PCB research resulted in enormous improvements in the analysis of trace contaminants. It is now possible to detect and quantitate each of the over one hundred PCB congeners present at concentrations in the ppb range. There are 209 PCB congeners with different numbers and positions of chlorine atoms.
This article is based on a thorough search of the literature from late 1960th to the present. Unfortunately it was impossible to read all papers on PCBs in the environment because over three hundred articles are published every year. We took care, however, to learn and present the views of scientists who firmly believe that PCBs are very harmful as well as of those who do not think so. We were able to discover some very drastic examples of papers with unfounded conclusions.
*Part I: Wiad. Chem. 2003, 57, 671
Wydział Chemii Uniwersytetu Wrocławskiego, ul. F. Joliot-Curie 14, 50-383 Wrocław
1Pracownia Chemii Plazmy, Wydział chemii, Uniwersytet Warszawski, ul. Pasteura 1, 02-093 Warszawa
2Zakład Podstaw Inżynierii Materiałowej, Wydział Inżynierii Materiałowej, Politechnika Warszawska, ul. Wołoska 141, 02-507 Warszawa
3Zakład Materiałów Konstrukcyjnych i Funkcjonalnych, Wydział Inżynierii Materiałowej, Politechnika Warszawska, ul. Wołoska 141, 02-507 Warszawa
Carbon is a unique material and the research results have taken the subject forward in many new directions in recent years. In addition to the fullerenes, a new allotropic form of carbon discovered in 1985 and produced in macroscopic amount in 1990, carbon nanotubes were found by Iijima in 1991 in a cathode deposit, formed during DC arcing of graphite anode. Since their discovery, the latter ones have captured the imagination of physicists, chemists and materials scientists alike. They are attracted to carbon nanotubes because of their extraordinary electronic and mechanic properties. Further egzo- and endohedral functionalization of fullerenes resulted in a new class of compounds and heterofullerenes were also produced by substitution of carbon atoms in a cage by other (mostly boron and nitrogen) atoms. Recently new intriguing forms of nanocarbous have been also discovered including carbon onions, encapsulates, filled nanotubes, `peapods', etc. In this review these nanocarbons are presented with the emphasis on production techniques and formation mechanisms, structure characterization and the future fields of application. While carbon are, laser ablation and CCVD (Catalytic Chemical Vapor Deposition) are the main techniques to produce these species, they are also formed under quite ditferent experimental conditions which are presented. When one browses through the carbon literature, some other new forms of spheroidal nanocarbons (e.g. nanoflasks, nonohorns, nanofoams...) also crop up again and again and a brief discussion is given here of these most recently discovered nanostructures.
Instytut Chemii, Akademia Świętokrzyska w Kielcach, ul. Chęcińska 5, 25-020 Kielce
One of the main goals of supramolecular chemistry is to use bowl-shaped molecules to recognize a substrate on the basis of size, shape, functionality and electrostatic profile. Design and investigation of molecules which are capable to form well defined, functional supramolecular structures has attracted considerable interest during the last three decades. This concept was borrowed from biological systems where the process of molecular recognition is central to the chemistry of life.
Among the molecules possessing the suitable shape and properties, there is a class of polycyclic mocromolecules-the resorcarenes. They have the cavities, whose geometries depend on the molecular structure, and the walls of these cavities contain active sites, which serve for the substrate binding. Availability of many active sites makes such a molecule a suitable platform for the synthesis of many new types of resorcarenes.
The synthesis of compounds of type l, derived from resorcinol and aldehydes, has already been described very carly but the structures of such a compound were confirmed by Erdtman et. al. in 1968 by crystallographic analysis [5-8]. The non-planar structure of resorcarenes makes it possible for them to exist in several different conformations. Resorcarenes can be prepared in high yield in a one-step procedure with neither template nor high dilution effects. In most cases, the mineral acids are applied as the catalysts for condensation of polyhydroxyphenols (i.e. pyrogallol or resorcinol) or the derivatives thereof with aldehydes [ 11-13]. However, preparations of these macrocycles making use of Lewis acids [ 14-19] or bases  as catalysts are known also. The effective method of controlling the spatial structure and physico-chemical properties of resorcarenes consists in: modification of the aldehyde type used, introduction of the substituent ortho to the hydroxy groups, and functionalization of the OH groups. The electrophilic substituents such as bromo or diazo group can be readily introduced at the ortho position [24, 25]. However, the most freduently employed electrophilic substitution in resorcarenes in the Mannich reaction [26-33]. Depending on the type and amounts of the reactants, one can obtain the aminomethyl [24, 30], oxazine  or oxazolidine  derivatives. In turn, the hydroxy groups of resorcarenes can be functionalized in several ways, by:
The last of the above approaches leads to the synthesis of cavitands which are in turn employed in the synthesis of the double resorcarenes, named carcerands and carcaplexes [66-88].
The presented paper is a continuation of work published in Wiadomości Chemiczne in 1997. Now, we present the development of methods for the synthesis of different derivatives of resorcarenes described in literature till now. The second part will concetrate on complexation properties of resorcarenes and the third part on their applications.
Katedra Chemii Akademii Rolniczej we Wrocławiu, ul. Norwida 25, 50-375 Wrocław
Although the majority of enzymatic hydroxylation reactions is catalysed by monooxygenases , dehydrogenases also play an important role in many reactions of this type. For example, dehydrogenases take part in hydroxylation of alifatic acids or nicotinic acid and its analogues . These reactions are important for degradation, biosynthesis and metabolism processes. Also, enzymic hydroxylation has been succesfully applied to the synthesis of L-carnitine, which is pharmacologically important compound. Another synthetic application involves enantioselective hydroxylation of isobutyric acid, where the proper catalyst species selection may lead to each enantiomer of the product selectively. Both enantiomers of b-hydroxyisobutyric acid are known as valuable chiral synthons for synthesis of many biologically active compounds, i.e. drugs, vitamins and others. The mechanism of alifatic compounds hydroxylation is well known - all the steps have been well documented. The reaction described were carried out by means of induced enzymes.
The proof of dehydrogenases mediation in hydroxylation of N-heterocyclic substrates is the fact, that the oxygen in hydroxyl group derives from water, not from the air.
Some of these reactions proceed quantitatively, affording very clean products. The reaction that found practical application of considerable importance is the hydroxylation of nicotinic acid (being precursor of a new generation insccticide) and its analogues.
It is highly probable that the microbial hydroxylation of this type can find application in transformations of so called "enewable resource" (i.e. nicotine) in order to obtain important biologically active products.
1Katedra Chemii Nieorganicznej I Analitycznej,
2Katedra Biochemii i Biotechnologii,
Wydział Chemiczny, Politechnika Rzeszowska, Al. Powstańców Warszawy 6, 35-959 Rzeszów
Derivatization is a modern method used in both organic and inorganic analytical chemistry. Application of derivatization to determine trace quantity of compounds requires very sensitive detection techniques. That combined with separation of analyzed compounds, makes the chromatographic systems like GC (gas chromatography) and HPLC (high performance liquid chromatography) especially useful in the analysis [1-2].
There are mainly three routes in trace analysis of derivatized compounds . One can obtain derivative before performing a column separation (pre-column technique), which can be done both inside or outside chromatographic apparatus, or after column separation (post-column technique). The third method is based on dcrivatization reaction taking place simultaneously with column separation and requires special column filling which is resistant to derivatization reagents.
There are several methods used to obtain derivatized compounds suitable for chromatographic methods [4-6]. Acylation adapted to determine traces of amphetamine, methamphetamine and their metabolites allows lowering the detection level to 1 ppb . Very important part of derivatization methods in trace analysis is a determination of heavy metals via sodium tetraalkylborate alkylation with AED detection (atomic emission detection). Organometallic traces can be derivatized with tetraborate salts with AAD detection (atomic absorption detection) . Less known methods like condensation and esterification are also very useful with suitable detector. For example, determination of ketones and aldehydes via derivatization with pentafluorophenylhydrazine allows to lower detection level down to 10-'4 mol . Esterification of fatty acids with 9-(2-hydroxyethyl)carbazole performed on HPLC column gives full separation of esters with detection limit being around 45 fmol .
Zakład Farmakologii i Toksykologii, Państwowy Instytut Weterenaryjny, Państwowy Instytut Badawczy, Al. Partyzantów 57, 24-100 Puławy
In the last few years solid-phase extraction (SPE) has become the most often used preconcentration technique for trace analysis. In SPE with most commercial sorbents, many components of complex samples are co-extracted, so additional clean-up is usually needed before the chromatographic analysis is made. However, specific SPE materials avoid this problem by providing a selective extraction. So far, the most selective phases used for SPE are based on immunoaffinity (IAC). The high selectivity and low stability of immunosorbents and the fact that is difficult and expensive to obtain biological antibodies are reason that IACs are used less widely for many different compounds [56, 57]. An alternative technology, using molecularly imprinted polymers (MIPs), is currently being extensively evaluated. Table 1 compares characteristics of molecularly imprinted polymer, immunoaffinity and conventional SPE columns.
As depicted in Figure 1, MIPs are made in situ by copolymerization of functional monomeres and crosslinking monomeres in the presence of the print molecule, called the template that after extraction leaves its molecular impression on the surface as the polymer forms around it [39, 30]. The examples of most commonly used monomers are presented in Figure 2 and Figure 3, respectively.
Table 2 provides an overview of examples of applications of SPE that incorporate molecularly imprinted polymer technology for extracting drugs and pollutants from different matrices.
Besides SPE, MIPs have been applied as selective sorbents in several analytical techniques, including liquid chromatography [12-18], capillary electrophoresis, electrochromatography [19-23], as immunoassay and sensors [24-28].
50-525 Wrocław, ul. Gliniana 23/17
Dioxins as a class of chemical compounds were defined with consideration of their biological properties rather than structure of molecules. Their structures are quite diverse and include all chlorinated dibenzodioxins and dibenzofurans as well as some chlorinated biphenyls. The common feature of several (but not all) dioxins is their pronounced toxicity to animals. The best known and most toxic is the 2,3,7,8-tetrachlorodibenzodioxin, simply referred to as dioxin or TCDD.
Dioxins are produced by virtually all industrial processes involving organic matter and chlorine at elevated temperatures. In the past the incineration of communal wastes was a particularly important source of dioxin but gases emitted by modern waste incinerators do contain less TCDD than ambient air.
For many years it was believed that dioxins are man-made compounds without natural sources but that belief was disproved by the discovery of TCDD in forty million years old clay deposits. Evidence is mounting that forest fires and burning of coal, wood and peat in domestic hearths are the most important sources of dioxins. A dioxin-free world is not possible because man has little control over forest fires and there is no way to curtail the burning of dioxin-producing fuels in homes, partricularly in poor countries.
Dioxins are in our bodies and around us. The fat of humans not exposed to large concentrations of dioxins contains TCDD at concentrations of several pg/g. The dioxin levels in the air are at the level of several pg/m3. Concentrations larger by orders of magnitude are in soils around the world and in sediments and sewage sludges.
Dioxins in human bodies are derived from the food we eat. The concentrations in food vary within wide limits, from less than 1 pg/g in vegetables to more than 100 pg/g in some fishes. There are scientists who express grave concern over possible harmful effects of dioxins in food but scientific evidence demostrates that such concerns are totally unfounded. After all the dioxins were on our planet since the beginning of mankind and even before and nobody was ever able to provide evidence of their harmfulness. On the contrary, there are many examples of highly exposed industrial workers who suffered no adverse effects although their blood contained several hundred times more dioxins than the blood of the general population.
It is commonly believed that TCDD is the most toxic man-made compound, is highly carcinogenic and presents a very serious risk to human health. These are unfounded beliefs without any support by scientific evidence. The only demonstrated dioxin-related human disease is chloracne, a skin disease associated with heavy exposure to TCDD. In some cases chloracne persists for one or two years but never threatens the life of victims. Medicine knows of no case of human death due to dioxins. This simple fact strongly contradicts the belief that dioxins are deadly poisonous to humans.
Wydział Chemii Uniwersytetu Wrocławskiego, ul. F. Joliot-Curie 14, 50-383 Wrocław
Instytut Chemii Nieorganicznej i Metalurgii Pierwiastków Rzadkich im. Włodzimierza Trzebiatowskiego, Politechnika Wrocławska, Wydział Chemiczny, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław
In the paper life and work of Professor Aleksander Bogacz has been presented. Professor Aleksander Bogacz received his M.Sc. in chemistry in 1957, Ph.D. in chemical sciences in 1964. He became a professor of chemical sciences in 1989.
The work achievement of Professor in the field of thermodynamic properties and transport properties of ionic liquids: molten salts (mainly uranium(IV) halide -alkali metal halide and lanthanide(III) halide - alkali metal halide mixtures) and slags has been shown. The results of his research were applied in copper metallurgy and they were used for elaboration of metallic lanthanides and their alloys obtaining technology.
A series of papers by F. Freund and his collaborators concerning the defect structure of water and/or carbon dioxide doped magnesium oxide is reviewed. The model of defect structure has been used to explain high temperature emission of water vapour, hydrogen and oxygen as well as some hydrocarbons from such preparations. According to the authors similar effects may also occur in the case of CaO or SiO2 and silicates. The possibility of abiotic formation of hydrocarbons in the earth's crust is discussed.
Zakład Radiochemii, Instytut Chemii I Techniki Jądrowej, ul. Dorodna 16, 03-195 Warszawa, firstname.lastname@example.org
Astatine, element 85, is the heaviest halogen. The first synthesis of' 211At was performed by Corson by irradiation of 209Bi target with a-particles. Most of the chemical studies have been done using this isotope. Astatine is one of the most difficult clements to study from a chemical point of view, and our knowledge of its compounds is rather incomplete compared to what we know about other elements. For this there are several reasons, especially that the astatine have very short-lived isotopes which make it impractical to obtain weighable amounts of the element. Therefore, chemical studies of astatine can be performed only with very low concentrations - concentrations much less than the impurity levels commonly present in an experimental system. Radionuclide 211At has been newly discovered within development of nuclear medicine, because it has a lot of diserable and advantageous properties, that are required in cancer therapy. It's potential application was recognized due to the radiotoxicity associated with emission of a particle and that of its daughter 211Po.
This review presents current knowledge about chemistry of astatine, especially its inorganic chemistry (e.g. valence states, anionic complexes of astatine with halogenides and pseudohalogenides ions etc.). Moreover, information is given about synthesis of some organic compounds of astatine. Special attention was paid on labelling of biologically active molecules with 211At and their potential applications in nuclear medicine.
Katedra Chemii Organicznej, Wydział Chemii, Uniwersytet Gdański, ul. Sobieskiego 18, 80-952 Gdańsk
Peptides, as neurotransmitters, neuromodulators and hormones take part in a number of physiological processes and thus are of enormous medical interest. However, the use of peptides as drugs is limited for example by degradation by proteases or poor bioavailability. One of the solutions of these problems seems to be application of peptidomimetics - compounds that act as substitutes for peptides in their interaction with receptors and can show higher metabolic stability, better bioavailability and longer duration of action [1?3].
Azapeptides, peptide analogs in which a-CH group of one or more amino acid residues in the peptide chain is replaced by a nitrogen atom, have proved to be a class of useful peptidomimetics (Figure 1) .
Azaamino acids provide unique conformational and configurational properties to the peptide chain which are caused by loss of asymmetry connected with a-carbon and free rotation around Ca-C' bond in the amino acid residue. According to the position of azaamino acid residue in the sequence, azapeptides can adopt different kinds of secondary structures and particularly - b-turns [6?8, 10?20].
This review presents different methods of azapeptide synthesis, either in solution (Figure 3) or on solid-phase [4, 21?36].
Isoelectronic replacement of the a-CH group by nitrogen atom leads to some changes in the direct neighbourhood of the pseudoamide bond, which influence the biological activity of the azaanalogs of the natural substances. Azapeptides were synthesized and tested as analogs of hormones [39?42] as well as inhibitors of different types of enzymes [43?60]. Especially worth noting is application of azapeptides as protease inhibitors. Incorporation of the azaamino acid residue in the P1 position of an enzyme substrate allows the formation of an acyl-enzyme complex and on the other hand deactivates the complex toward nucleophilic attack of a water molecule in the last step of peptide bond hydrolysis (Figure 11).
In last years azapeptidic compound ? ReyatazTM (Atazanavir, BM-232632) has been discovered which seems to be a promising drug in the treatment of AIDS as it acts by blocking the activity of HIV-1 protease (Figure 13) [58?60].
Wydział Chemii, Uniwersytet Warszawski, ul. Pasteura 1, 02-093 Warszawa
It is known that both the nature and structure of a metal have a great influence on electrochemical processes. Interpretation of a mechanism of electrochemical reactions that occur on polycrystalline electrodes is often complicated because of their heterogeneous structure consisting of randomly distributed monocrystals on the surface. To avoid this problem, electrodes with well defined surfaces are commonly used in electrochemical experiments.
In this paper, effects of the surface structure of a metallic electrode on properties of the double layer of the metal/solution interface, electrosorption and also on the electrochemical reactions has been reviewed. The presented data refer mainly to the basic planes of monocrystalline electrodes of face-centered cubic system.
In first three chapters problems of the double layer structure of monocrystalline electrodes, the correlation of the potential of zero charge and work function, and the competition of a substrate and water molecules in the electrosorption process in relation to the hydrophilicity of metals are discussed.
In chapters 4 and 5 the influence of the surface structure on the adsorption of organic molecules, strongly and weakly interacting with the electrode surface, is reviewed. It was shown that the surface concentration of adsorbate depends not only on the number of adsorption sites (assumed as the surface atom density) but also on the geometry of adsorbed molecule as well as on the kind and size of the supporting electrolyte anions. The latter play a very important role when the interaction of an adsorbed molecule and a metal is weak. Chapter 6 concerns the role of the electrode surface structure in the hydrogen ion discharge and also underpotential deposition of ions.
The relationship between electrocatalytic properties of an electrode and its surface structure is presented in chapter 7. The kinetics of oxidation of methanol and formic acid at different planes of the platinum electrode and various products of the reduction of carbon oxide on copper monocrystalline electrodes are given as examples.
Wydział Chemii, Uniwersytet Wrocławski, ul. F Joliot-Curie 14, 50-383 Wrocław
This paper is a short review of a spin-crossover phenomenon in complexes of iron(II). This phenomenon is related to the thermally induced transition between a diamagnetic low spin ground state (LS or S=0) and the excited paramagnetic high spin state (HS or S=2). Numerous compounds switch from a stable electronic state to another state in a reversible and detectable fashion in response to an appropriate and controllable external perturbation. This transition is accompanied by a strong thermochromism between rose and white colors. In certain cases, a hysteresis effect is accompanying this transition, which confers a memory effect to the system. The potential applications of spin transition (ST) molecular materials in the field of display and data processing has led to intensive studies of this phenomenon in the last ten years. For this purpose the compounds need to show a large thermal hysteresis, with the middle of the hysteresis loop falling as close as possible to room temperature. To achieve this goal iron(II) ST molecular materials are designed and synthesized as polymers in order to increase intermolecular interactions. In this paper some polymers based on 1,2,4-triazole derivatives are described because of their bridging nature leading to a strong cooperativity. The influence of various parameters, namely type of counter ion, R substituent in 4- position in the triazole ring, number of noncoordinated lattice water molecules, on the structure and ST regime of Fe(II)-1,2,4-triazole polymers is depicted. Some of the compounds presented might be of potential use as the electronic displays or switches.
Wydział Chemii Uniwersytetu Wrocławskiego, ul. F. Joliot-Curie 14, 50-383 Wrocław
Zakład Chemii Kwantowej, Wydział Chemii, Uniwersytet Mikołaja Kopernika, ul. Gagarina 7, 87-100 Toruń
The hydrogen bond, X-H···Y, is usually characterized as a relatively weak interaction involving the X-H bond (where X is an element with the electronegativity greater than that of H) and a region with high electron density (e.g. lone electron pairs of highly electronegative element Y or a π-electron system) [2-5, 8, 17-21, 27-52]. The interaction is believed to have predominantly electrostatic origin and is possibly accompanied by some charge transfer between X-H and Y. In the conventional picture of hydrogen bonding, there is attractive interaction between the region of high electron density (Y) and the polarized proton donor X-H bond that causes an elongation of the X-H bond and a concomitant decrease of its stretching frequency (red shift). This effect can be also reinforced by electron density transfer from the proton acceptor (Y) to the proton donor molecule. The direction of this transfer is primarily to the σ* antibonding orbital of the X-H bond and consequently causes a weakening of this bond. The X-H bond in the X-H···Y system undergoes elongation and its stretching frequency is lowered. The red shift of the X-H stretching frequency is seen as the most important manifestation of the hydrogen bonding.
However, in some cases it occurs that on complexation the X-H bond shortening and a concomitant stretching frequency shift to higher values (blue shift) may also take place. There are many experimental and theoretical evidences that this unconventional behaviour is more widespread than originally thought [75-79, 84-86, 96-101, 106-109]. Since for this kind of interaction the three main features of the classical hydrogen bond (elongation of X-H, red shift, and IR intensity increase) are all in opposite direction, this new type of bonding (interaction) is commonly referred to as improper, blue-shifting H-bond.
In this review several examples of the existence of the improper, blue-shifting hydrogen bonds are presented and the magnitude of the complex interaction energies, changes of bond lengths, and blue shifts are examined. To facilitate the understanding and meaning of diverse theoretical results, references to computational methods in use, are added. Particular attention is given to methods and theoretical ideas used in calculations for hydrogen-bonded systems.
Wydział Chemii Uniwersytetu Jagiellońskiego, Zakład Chemii Ogólnej, ul. Ingardena 3, 30-060 Kraków
Semifluorinated n-alkanes (SFA), of the general formula F(CF2)m-(CH2)nH (abbreviated as FmHn) consist of a linear hydrocarbon segment linked to a fluorocarbon chain. These two units are highly incompatible, what arises from a very different physical and mechanical properties of hydrogenated and perfluorinated hydrocarbons. The presence of two opposing segments within one molecule makes semifluorinated alkanes a very interesting class of compounds, which show a particular behavior in bulk and at interfaces. Their highly asymmetric structure, arising from the incompatibility of the both constituent parts, results in surface activity of these molecules (so-called primitive surfactants) when dissolved in organic solvents, and allows for the Langmuir monolayer formation if spread at the air/water interface, despite of the absence of polar group. Since 1984, semifluorinated alkanes have been subject to many studies concerning their structure and physicochemical properties in bulk phase (solid and liquid) and at interfaces (oil/water; air/water). The present article reviews the results obtained so far.
Katedra Chemii Farmaceutycznej Collegium Medicum Uniwersytetu Jagiellońskiego, ul. Medyczna 9, 30-688 Kraków
This review attempts to briefly summarize the recent development in the study of γ-aminobutyric (GABA) receptors, and their ligands. The search on compounds with agonistic and antagonistic properties of GABA receptors, the structure activity relationships, and therapeutic prospects of GABA receptors ligands was also described. GABA is the major inhibitory neurotransmitter in the brain [1-6], and influences neurons via a large number of receptor subtypes which are grouped on the basis of their pharmacology under three major classes of receptors: GABAA, GABAB, and GABAC. GABAA and GABAC receptors are ligand gated ion channels, while GABAB receptors are G-protein coupled receptors [7-10]. These receptors, especially GABAA receptors, are involved in neurological and psychiatric disorders, and are therapeutic targets in certain diseases. Several different binding sites on GABAA receptors were proposed, these include agonist sites [11-14], which also recognize competitive antagonists , and many positive or negative modulators sites [16-20]. GABAA receptors are modulated by benzodiazepines [21-26], barbiturates, neurosteroides , klomethiazol [28, 29], anesthetics [30-33], ethanol , some insecticides , furosemide , Zn2+ iones , and sites for other compounds [38-40]. Some ligands of GABAB and GABAC receptors are also presented [41-44].
1*Katedra Chemii, SGGW w Warszawie, ul. Nowoursynowska 159C,
2Instytut Chemii, Wojskowa Akademia Techniczna w Warszawie, ul. Kaliskiego 3, 00-908 Warszawa
In 1933 adamantane was isolated from petroleum of Czechoslovakia by Landa . Its unique structure is reflected in highly unusual physical and chemical properties. For example this hydrocarbon has extraordinary high melting point 269oC. It was also shown that the bromination is an ionic process; it is catalyzed by Lewis acids and not by peroxides or light. Adamantane possesses a unique rigid, but strain-free ring system, composed of three fused chair cyclohexane rings. The other source of adamantane derivatives are organic syntheses including cyclization and rearrangement of hydrocarbons. Also, it was found that 1-adamantanol refluxed with trifluoroacetic acid and respective heterocycles yielded N-adamantylated compounds .
Particularly the biological properties of adamantane derivatives are very interesting. The most known of clinical use is the antiviral drug 1-amnoadamantane (amantadine) [7-11]. In the presented paper only antimicrobial, antiviral as well as anticancer agents are described. Novel ester imides synthesised from trimellitic acid chloride and 1-adamantanol, 2-adamantanol, 1-adamantanemethanol or 1-adamantaneethanol, were tested as antimicrobial compounds [16-18]. Some of these derivatives showed significant activity. The incorporation of L-alanine and L-phenylalanine aw well as ω-amino acids into the phthalimide moiety as N-substituents, leads to strong antimicrobial activity against Staphylococcus aureus strains.
A variety of 5'-N-phtaloyl-3'-azido-2',3'-dideoxythymidine derivatives has been synthesised and evaluated for their activity against HIV-1 and HIV-2 . Most of the AZT derivatives showed antiviral activity in the lower micromolar concentration range. It should be notice that all these compounds were inactive against HIV in thymidine kinase-deficient cells, pointing to the compounds' requirement to release free AZT to afford antiviral efficacy.
Tumor necrosis factor-alpha, so-called TNF-α, is a cytokine produced by numerous cell types among which monocytes/macrophages play a major role [29-40]. Investigation of the biological properties of TNF-α, in vitro as well as in vivo models, has revealed that this cytokine has both beneficial and unfavourable effects. In this context, it is interesting to search for new drugs working as stimulators or inhibitors of TNF-α production. It was found that N-(adamant-1-yl)monothiophthalimide and N-(adamant-2-yl)monothiophthal-imide showed over 200% enhancing of cytokine production, while some other imides were inhibitors.
The known drug bropirimine is orally active immunomodulator that stimulates production of TNF-α and other cytokines and is now under phase II clinical trials for treatment of bladder carcinoma . The inspiration for us was the search for bropirimine adamantane analogues . The synthesis of adamantylated pyrimidines was based on the Traube reaction of 3-(adamantan-1-yl)-3-oxopropionic acid ethyl ester with urea, thiourea, guanidine as well as acetamidine, respectively. Then the compounds obtained were converted into respective bromo-, thio- and S-alkyl derivatives. The significant anticancer and antimicrobial properties of [2-(6-adamantan-1-yl-2-methylpyrimidin-4-ylsulfanyl)ethyl]dimethylamine were found.
Katedra Chemii, Akademia Rolnicza we Wrocławiu, uj. Norwida 25, 50-375 Wrocław. E-mail: email@example.com
Many natural terpenoids include in their structure a gem-dimethylcyclohexane ring. Such compounds are often isolated from plants or animals, where they fulfil different functions. Compounds a with gem-dimethylcycloxehane ring have been found in many marine algaes molluscs. These compounds show different biological properties, for example antibiotic [10, 66, 67, 79], cytotoxic [15, 16], fungicidal , inhibiting HIV . Similar properties are also found in compounds isolated from plants growing in different places on Earth, plants which for many years have been known and used in tradicional medicine as antidote against different diseases [24-27, 36-46, 72-74]. These discoveries are very important for people searching for new and effective medicines against old and new diseases. For example some compounds with a gem-dimethylcyclohexane ring show an inhibitory effect on not yet curable cancers [50-57, 81].
The compounds with a gem-dimethylcyclohexane ring which occur in plants or animals have an affect not only on humans, but also on other plants or animals. Such affect can be observed in both marine and terrestial organisms [59-61, 71]. In our times very safe and effective crop protection is a very important problem. Because of this people try to find natural compounds which can produce desirable biological effects. Compounds with a gem-dimethylcycloxehane ring found in some plants can act as natural herbicides [22, 23]. Some of these compounds can also work as deterrents against insect pests. These deterrents affect the insects' sense of taste and prevent them from eating, which finally makes them die despite the abundance of food [28-33].
Politechnika Wrocławska, Instytut Chemii i Technologii Nafty i Węgla, ul. Gdańska 7/9, 50-344 Wrocław. E-mail: firstname.lastname@example.org
Aerogels are solid, organic (carbon) and inorganic porous materials of the exceptional properties such as very large specific surface area, low bulk density, low thermal and electric conductivity and superporous structure, obtained by sol-gel process. Numerous potential applications of aerogels as catalysts and catalyst supports, adsorbents, sensors, insulators, Cherenkov detectors and many others attract attention of many research laboratories. This review demonstrates selected routes to obtain organic and carbon aerogels. A special attention is given to the materials obtained by polycondensation of resorcinol with formaldehyde (RF aerogels). Some basis of the sol-gel processes as well as the influence of solvent on gelation time and shrinkage of the RF aerogels is presented. In the next part of the review the effect of the base preparation parameters i.e., resorcinol to formaldehyde (R/F) molar ratio and resorcinol concentration in solvent on textural properties on the final aerogel is discussed. Sol section of this paper is finished with information on the effect of catalyst concentration on particle size and shrinkage. Gel section contains informations about gelation time and aerogel properties dependence on it. Further sections are focused on drying step of the obtained gel, often found as the most important for the sake of final product characteristics. The reason why the drying step is so important is that solvent must be removed without destroying the gel matrix. Solvent removal methods are described with some principles of supercritical (low- and high-temperature) and freeze drying. Product obtained after supercritical or freeze drying step is called aerogel or cryogel respectively. Finally the effect of carbonization parameters on the carbon aerogels properties is described. Effect of other organic aerogel precursors such as cresol, phenol, furfural, melamine, PVC, MDI used in the sol-gel process of the preparation procedure of organic and carbon aerogels is described. Finally, selected technical applications of the carbon aerogels are presented.
Katedra Chemii Nieorganicznej i Analitycznej, Wydział Chemiczny,
Politechnika Rzeszowska, Al. Powstańców Warszawy 6, 35-959 Rzeszów
Flavonoids belong to a large group of natural compounds of substantial biological activity. Some examples are rutin and hesperidin which are widely used in medical treatment. Recent growing interest in these compounds comes of their possible application as natural antioxidant protecting against harmful action of free radicals. Moreover, flavonols could complex metal cations and some of them are used as analytical reagents [6-8]. The major reason for limited application of flavonoids is their weak solubility in water.
Sulfonic derivatives of flavonoids due to the presence of sulfonic group in the molecule are well soluble in water. They form complexes with metal ions like their mother compounds and the complexation range is significantly wider than bioflavonoids. It in proposed to use quercetin-5'-sulfonic acid (QSA) (1) and sodium salt of morin-5'-sulfonic acid (NaMSA) (6) as new reagents in spectrophotometric determination of metals [18, 19]. Some of the compounds of Al, Ga and In with quercetin-5'-sulfonic acid and sodium salt of morin-5'-sulfonic acid show strong luminescence and for this reason can be used in laser technology. It has been found that sulfonic derivatives of quercetin could be an effective antidote against heavy metals - Hg(II), Cd, Pb(II) and as reported [37, 38] sodium salt of quercetin-5'-sulfonic acid (2) is a particularly active one. Sulfonic derivatives of quercetin, morin and chrysin, exhibit also the activity in different biological systems. It is supposed that sulfonic derivatives of flavonoids could have greater practical application than their mother compounds.
Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław
Instytut Inżynierii Chemicznej, Politechnika Wrocławska, ul. Norwida 4/6, 50-373 Wrocław
Attractive features of biological systems include versatility, substrate selectivity, regio-, chemo-, and enantioselectivity as well as catalysis at ambient temperatures and pressure. However, the challenge facing bioprocesses is cost competitiveness with existing chemical process assets. The current expansion of industrial biocatalysis can be attributed to recent progress in molecular biology, advanced instrumentation, and engineering. Novel catalyst formulation based on technology such as directed evolution and enzyme immobilisation, has resulted in improved types of highly active and stable biocatalysts.
In industrial biotransformations the immobilisation of enzymes on/in support is often chosen to enhance the stability and to simplify the biocatalyst recovery. The main purpose of this paper is to present a general picture of the immobilization techniques that is organised according to the two categories of methods, i.e., conventional methods (Part 1) and immobilisation in membrane reactors (Part 2).
The intention of the first part is outline the common procedures that span from binding on carrier materials to incorporation into in situ prepared matrix in which binding forces vary between weak adsorption and covalent binding. Although the development of suitable immobilisation protocol often follows empirical guidelines, some general rules to facilitate proper applications are also presented. Immobilisation of enzymes means a deliberate restriction of the mobility of the enzyme, which can also affect mobility of the solutes. Thus it is mandatory to have basic knowledge of the essential contribution of the chemical forces and the physicochemical interactions during heterogeneous catalysis that is also discussed. Finally, the technological developments in the field of immobilised biocatalysts are presented that show possibility of a wide and more economical exploitation of enzymes in industry, medicine, and in the monitoring devices like the biosensors.
Instytut Inżynierii Chemicznej, Politechnika Wrocławska, ul. Norwida 4/6, 50-373 Wrocław
Biocatalysis involves the enzyme-promoted transformations of a substrate into useful product in either a homogeneous or heterogenous system. The separation of reactants from products and the recovery and reuse of the catalyst from the reaction mixture is an important step that significantly decreases the cost of the process. Membrane reactors constitute an attempt to integrate catalytic conversion, product separation and/or concentration, and catalyst recovery into a single operation unit that lowers the overall cost of final product.
In an enzyme membrane reactor biocatalyst is immobilized within the reaction vessel or on/in a membrane (catalytic membrane). The paper shows two possibilities for immobilization of enzymes:
1 - localization of the soluble biocatalyst in a certain defined region of space of a membrane reactor; e.g. a volume of a reactor and separation unit or in lumen/shell side of ultrafiltration unit;
2 - adsorbed, deposited or bound (physically, via affinity ligand or by covalent attachment) to the surface of a membrane or entrapped within pores or material of the membrane.
Arguments counting for membrane supported or soluble enzymes are also presented. Reactors with soluble biocatalyst in a volume of a membrane reactor seem be suited to carry out complex enzymatic transformations, involving several enzymes and cofactor regeneration. Membrane reactors with catalytic membranes are particularly appropriate for nonconventional media such as organic-aqueous two-phase systems and for production of biosensing elements of enzyme electrodes. It is therefore the intention of the paper to outline the common immobilization methods and technologies to facilitate proper applications of enzymes immobilized in a membrane reactor.
ul. Włościańska 18/43, 01-710 Warszawa
The professional activity of professor Janina Świetosławska-Żółkiewska (1910-2003) was connected with promoting spectroscopic techniques in analytical chemistry. She had organized the Laboratory of Technical Physics at the Instritute of Chemical Industry. Her particular activity centered on organizing curses and seminars, where the analysys, both from industry and from the universities and scientific institutes could discuss recent achievements in anatytical chemistry. She had developed new spectrometric analytical procedures, wrote important monographs and put lot of effort in education of young chemists in spectrometry. Within 25 years she was a member of thr Presidium of the Commission (later the Committee) on Analytical Chemistry of the Polish Academy of Sciences. In cosideration of her merits in the field of analytical chemistry and of her outstanding personality, professor Janina Świętosławska - Żółkiewska was awarded the first Wiktor Kemula medal founded by the Polish Chemical Society.
Zakład Chemii Kwantowej, Wydział Chemii, Uniwersytet Mikołaja Kopernika, ul. Gagarina 7, 87-100 Toruń
The conventional hydrogen bonds, X-H···Y, are believed to arise due to the attractive interaction between the polarized proton donor (X-H) bond and the region of high electron density Y. This leads to the elongation of the X-H bond and the concomitant decrease of its stretching frequency (red shift). This effect can be further reinforced by electron density transfer from the proton acceptor (Y) to the proton donor molecule. The direction of this transfer is primarily to the σ* antibonding orbital of the X-H bond and consequently causes its weakening. The X-H bond in the X-H···Y system undergoes elongation and its stretching frequency is lowered. The red shift of the X-H stretching frequency is seen as the most important manifestation of the hydrogen bonding.
In some cases, however, the complexation may lead to its shortening with the concomitant stretching frequency shift to higher values (blue shift). For this kind of interaction the three main features of the classical hydrogen bond (elongation of X-H, red shift, and IR intensity increase) are all in opposite direction and for this reason this new type of bonding (interaction) is commonly referred to as the improper, blue-shifting H-bond.
In Part II of this review different theories, which attempt to explain the origin of the blue shift, are discussed. Particular attention is given to the role of electrostatic interactions and charge transfer between interacting molecules. According to recently proposed models it is believed that the blue shift is mostly caused by the electrostatic interaction and is possibly enhanced by some intermolecular charge transfer from the proton acceptor molecule to remote parts of the proton donor. This is followed by the reorganization of the electron density distribution and structural changes in the whole proton donor molecule [12, 13]. Some other ideas and theories, which expose the role of the balance between electrostatic attraction and Pauli repulsion, are also discussed. Within these models there are no fundamental differences in the bonding characteristics of the red-shifting and blue-shifting H-bonded complexes; the blue shift is seen rather as an accidental result of the balance between different contributions to the interaction energy [6, 23].
Instytut Chemii, Akademia Podlaska, ul. 3 Maja 54, 08-110 Siedlce
This review is a continuation of our effort to measure systematically the rate constants for thermal electron capture by bromo-, chloro- and fluoroethans in the mixtures with carbon dioxide using the electron swarm method. All the experimental data show that only two-body reactions occur. The linear dependence of the rate constants (log k) on the electron polarizabilities of the attaching center has been found.
Theoretical analysis using PM3 semiempirical method with a commercial HyperChem program were performed and the structure of neutral molecule and its negative ion has been calculated. These results have been compared with the molecular characteristics and thermal electron capture rate constants.
Wydział Chemii, Uniwersytet im. A. Mickiewicza, ul Grunwaldzka 6, 60780 Poznań
Lactones, being derivatives of hydroxy carboxylic acids, represent a special group of intramolecular esters. A large number of biologically important natural products are derivatives of chiral y- and 8-lactones. In addition, these commonly encountered compounds, due to their high reactivity, are valuable synthetic intermediates.
Lactones are particularly susceptible to nucleophilic attack. As a consequence, the cleavage of the lactone ring is a commonly used process in laboratory synthesis of organic compounds and in industry. Cleavage of lactones may be effected under variety of reaction conditions including reagents, catalysts, solvents and temperature. The chemoselectivity observed in these reactions allows selective reactions of multifunctional compounds, very often of rather complicated structure.
The enhanced reactivity of lactones toward nucleophiles makes hydrolysis their most investigated reaction. The ring cleavage occurs under basic (alkali metal hydroxides or alkoxides, tertiary amines) or acidic (Bronsted or Lewis acids) conditions. The effective cleavage of the lactone ring occurs also in reactions with nitrogen nucleophiles, which include ammonia, primary and secondary amines and hydrazine derivatives, as commonly used reagents. Sulphur and selenium derivatives are prepared in reactions of lactones with S- and Se-nucleophiles. The effective nucleophilic reducing agents include metal hydrides, of which lithium aluminium hydride is the most frequently used reagent. Other reducing agents like sodium borohydride and other complex boron hydrides have also been reported.
Reductive cleavage of lactones under catalytic hydrogenation conditions and with the aid of complex reducing systems are discussed. The metaloorganic reagents effectively cleave lactones, while a new carbon-carbon bonds are formed.
Since the literature concerning transformations of lactones is enormous, in this review the selected examples are included to demonstrate usefulness of lactone cleavage reactions for diverse synthetic purposes.
Instytut Chemii i Technologii Organicznej, Wydział Inżynierii i Technologii Chemicznej, Politechnika Krakowska, ul. Warszawska 24, 31-155 Kraków
Biologically active naphthoquinones are secondary metabolites of many plants. Juglone (5-hydroxy-1,4-naphthoquinone) is a naturally occurring naphthoquinone forming (with derivatives) the more interesting extractable substance of the roots, leaves and green skin of walnut (Juglandeceae) (Tab.1). Its allelochemicals properties can be used for weed control in agrochemistry (natural pesticide) [2-5]. In Poland it is present in widespread Juglans regia.
Analytical procedures for plant extracts [15-31], methods of synthesis  and chemical properties of juglone [20-26] have been described. Extractive and chromatographic methods (TLC, HPLC) were investigated for the preparation and determination of juglone in natural raw materials [29, 32]. Methods of synthesis and use of the chemical modification of juglone have been investigated by many workers [33-38].
Juglone and its derivatives have a wide spectrum of applications in folk medicine [10, 14, 20], cosmetology [54-58], pharmacology [38, 59-61] and agroecosystems protection [47-50]. Many articles and patents demonstrated a variety of potential exploitations for juglone, for example, to prepare antiviral and antifungal naphthoquinone derivatives, in skin-colouring preparation and in hair dyes.
Oxidative properties and formation of active semi-quinone radical, determined biological activity of juglone. Juglone inhibits the germination and growth of certain species of plants [42, 43]. Inhibits RNA polymerase II transcription in vitro and microsomal H+-ATPase activity [46, 45]. Exhibits cytotoxic activity against some human tumours and inhibit HIV-1 reverse transcription [51, 52]. It is a potent antimutagen with respect to mutagenicities induced by 2-nitrofluorene and 1-nitropyrene .
Laboratorium Wirusologii Molekularnej i Chemii Biologicznej, Centrum Biologii Medycznej PAN, ul. Lodowa 106, 93-232 Łódź
Polyhedral clusters containing boron, alone or in combination with other elements, have been know for nearly a century and intensive studies of their structures, bonding, and reactivity have been under way for more than half that period. Carboranes are boron cage system in which one or more carbon atoms belong as an integral part to an electron-delocalized borane framework. The term "carboranes" includes both closed polyhedral and open-cage structures. Polyhedral carboranes of general formula C2Bn-1Hn have been characterized from n=2 to n=12. One of the most striking features of the carboranes is the capability of the two carbon atoms and ten boron atoms to adopt the icosahedral geometry in which the carbon and boron atoms are hexacoordinate. This feature of the icosahedral structure gives rise to the unusual properties of these molecules and their derivatives.
Because of their unique physical and chemical properties, carboranes have been used to prepare catalysts, radiopharmaceuticals, polymers and an assortment of coordination compounds and materials for nanotechnology. The medicinal chemistry of carboranes is centered on their use in boron neutron capture therapy of tumors (BNCT).
1Katedra Chemii Analitycznej, Wydział Chemiczny, Politechnika Warszawska,
ul. Noakowskiego 3, 00-664 Warszawa
2Centralny Ośrodek Badawczo-Rozwojowy Opakowań, ul. Konstancińska 11, 02-942, Warszawa
In 1994 new legislation (Directive 94/62/EC ), limiting the level of the most toxic heavy metals (Cr(VI), Cd, Hg and Pb) in packaging materials to 100 mg kg-1 (as a total amount) was introduced in the European Union. The Directive has become the basis for corresponding legislation acts in the EU member and candidate countries, including Poland [13-16]. These events have focused the attention of the scientists to the necessity of development of methods suitable for the examination of enormous amounts and a variety of packaging materials for trace amounts of elements (ng g-1, μg g-1) that can occur in such materials.
Papers, paperboards and plastics make the basis of packaging materials used. Traces of toxic substances in such materials can origin from contaminants occurring in various substrates (e.g. wood pulp, polymers), from numerous additives (e.g. catalysts, thermal stabilizers, adhesives, lubricants, antioxidants, pigments, printing inks) used in the production process as well as from process water and process equipment. A discussion of packaging materials produced as well as sources of toxic elements is presented in the paper in detail.
Analytical methods for the determination of traces of various elements (chromium, cadmium, lead, mercury, arsenic, antimony, molybdenum, barium, copper and zinc) in packaging materials developed by the authors have been described. Digestion procedures used for the transformation of the analytes from materials of various matrices (polymer (polyethylene, polypropylene, polystyrene, poly(ethylene terephthalate)), paper and paperboard) into solution are presented in Table 1. The application of modern analytical technique, inductively coupled plasma-time of flight-mass spectrometry (ICP-TOFMS), to the detection of the elements has been described. The ICP-TOFMS technique offers detection limits (DLs) suitable for the determination of a range of elements that can occur in packaging materials. The technique offers multi-element capability, selectivity, possibility of simultaneous isotope determinations, extremely high data-acquisition speed (quasi-simultaneous measurement of all masses extracted from the plasma ion source), high ion transmission and high sample throughput [34, 35]. Data for the isotopes used for the detection of the analytes as well as the detection and quantification limits achieved by the authors are given in Table 2. Results for the level of the elements determined in four groups of packaging materials examined, I and II: of polymer matrices intended for food- and non-food-packagings, respectively, and III and IV: of paper and paperboard matrices (for food- and non-food-packagings, respectively) have been given in Table 3. Mass spectra of some materials chosen from particular examined groups are presented in Fig. 2.
Instytut Chemii, Uniwersytet Opolski, ul. Oleska 48, 45-052 Opole, e-mail: Piotr.Wieczorek@uni.opole.pl
Derivatives of amino acids are known from their great biological relevance, for example can be used as pharmaceuticals, crop protection substances or food additives. In significant number of cases such substances show their biological potency only as single enantiomer. Therefore, one of the most important conditions during their production is to ensure their high optical purity. Generally, two routes to accomplish this goal are considered to be most effective. The first one is to synthesize enantiomers with the support of chiral catalyst introduced into the reaction mixture. The second approach involves the preparation of racemic mixture and in final step to separate it into single enantiomers. Considering the separation the most popular methods are enantiomers crystallization in the form of diastereoisomeric salts and chromatographic separation of racemates with application of chiral stationary phases. However, despite of their very extensive use, those methods possess several drawbacks and limitations. Among them, the most inconvenient are large use of solvents and expensive, chiral substances acting as agents responsible for the enantioseparation. Additionally, in case of chromatography some problems with non-linearity of the chromatographic process can take place. Therefore, the study on alternative ways of achieving the efficient separation of enantiomers is carried out in many laboratories. In this review, the very promising methods of the stereoisomers separation namely extraction and membrane techniques are presented and discussed. In case of extraction the examples of classical liquid - liquid extraction as well as aqueous - aqueous extraction and solid phase extraction application for amino acids enantiomers and their derivatives separation are described. The special attention is paid on the use of membrane techniques. The brief overview of applications of different membrane processes for the same purpose including the use of chiral polymer membranes, molecularly imprinted membranes, achiral membranes with chiral agents (solution free or immobilized) and liquid membranes is also presented. Finally, the examples of preparative scale processes, in which extraction and membrane techniques were used, are also discussed to show their applicability for the production of amino acids and their derivatives with high amounts and optical purity.
Wydział Chemii, Uniwersytet Warszawski, ul Pasteura 1, 02-093 Warszawa
The porphyrin molecules contain four pyrrole rings linked via methane bridges. They are tetradentate ligand, in which the space available for the coordinated metal ion has a maximum diameter of approximately 3.7 Å. Porphyrins and their complexes with metal ions play important role in several biological as well as catalytic systems. They are involved in dioxygen transport and storage, photosynthesis or electron transfer.
Due to strong complexing properties and catalytic behaviour, porphyrins and metaloporphyrins have found numerous applications in analytical chemistry. Several porphyrins become useful as the high sensitive chromogenic reagents. The stable complexes between transition metals and porphyrin ligands enable coordinating interaction with additional ligands above and below the molecule plane, so these compounds are used as components of membranes of ion selective electrodes in potentiometry and voltammetry. Several porphyrins find applications as optical sensors and biosensors. Due to the mixed mechanism of interaction between porphyrin macrocycle and various solutes, porphyrins find interesting applications as stationary phases in HPLC for separation of aromatic carboxylates, sulfonates, polycyclic aromatic hydrocarbons, fullerenes as well as amino acids and peptides. In capillary electrophoresis these compounds found application as the derivatizing agents. Porphyrins could be also used as a modifier in solid phase extraction technique or the selective ligands for enrichment of some transition metals.
Instytut Chemii Nieorganicznej, ul. Sowińskiego 11, 44-101 Gliwice
*Instytut Chemii i Technologii Nieorganicznej, Politechnika Śląska, ul. Krzywoustego 6, 44-100 Gliwice
On the base of literature the problems concerning the interlaboratory and interlaboratory systems of quality control and assurance for analytical laboratories were discussed. The special attention was given on the role of certified reference materials (CRMs) in validation methods.
A Certified Reference Material (CRM) is a RM accompanied by a certificate, one or more of whose properties are certified by a procedure that establishes its traceability to an accurate realization of the unit in which the property values are expressed (according to ISO Guide 30).
Certified reference materials fulfill various purposes in laboratories: calibration of equipment, verification of accuracy of results, aids in methods or performance improvement where necessary, daily quality control and achievement of traceability to the basic units. CRMs serve in inorganic trace element as means of transferring measurement quality. When talking about subjects such as certified reference materials and their role in trace analysis, very importance is quality assurance. Quality Assurance (QA) in analytical chemistry is the name denoting the sum of procedures used to ascertain that results of analytical measurements are good enough for their intended purpose. It needs to be understood that QA is composed of two essential components: Quality Control and Quality Assessment. The importance of traceability in this system was also discussed.
Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław
T. Cukierda, Last changes: