Analysis for estrogens as environmental pollutants--a review

The approaches to the analysis for estrogen compounds as environmental pollutants are critically reviewed and evaluated on the basis of significant, recent original publications. The importance of sample pretreatment and analyte preconcentration techniques is pointed out, with an emphasis on SPE and on the use of highly selective interactions such as molecular recognition. The hyphenated systems of high-performance gas or liquid chromatography and mass spectrometric techniques are discussed as the basic methods of determination of estrogens in environmental samples. Immunochemical procedures are shown to be useful in semiquantitative screening of estrogen pollutants (e.g. ELISA kits). Classical HPLC and GC with common UV/Vis, fluorescence and electrochemical detection are useful in routine checking on higher pollutant concentrations.

An evaluation of the experimental approaches to detection of small ions in CE

This review points out some important trends in the development of the detection techniques for small ions in CE. On the basis of selected literature references it briefly discusses some general requirements on detection techniques in CE. Various optical measurements, mass spectrometric approaches and electrochemical detection techniques are dealt with. Some specific features of microchip CE separation and detection are pointed out and possibilities of dual detection are mentioned. The principal parameters of the above detection techniques are then briefly compared.

Characterization of substituted polyacetylene microstructure by pyrolysis gas chromatography

A series of substituted acetylenes has been polymerized with WOC14/Ph4Sn metathesis catalyst and [Rh(cod)OMe]2 insertion catalyst, and the thermal degradation of the polyacetylenes prepared has been studied using pyrolysis capillary gas chromatography (Py-GC) with flame ionization and mass spectrometric detection to obtain information on the effect of the catalyst on the head-tail (H-T) isomerism of polyacetylenes (poly(phenylacetylene), poly[(4-methylphenyl)acetylene], poly(benzylacetylene), poly((2-fluorophenyl)acetylene], poly[(3-fluorophenyl)acetylene], and poly[(4-fluoro-phenyl)acetylenel). Cyclotrimers have been found to be the main pyrolysis products in all cases. Direct Py-MS connection was used to determine the temperature profiles of the released pyrolysis products. 1,3,5-Trisubstituted benzenes were found to be the predominant pyrolysis products of the polymers prepared with the insertion catalyst, which proves the presence of long head-to-tail sequences of monomeric units in these polyacetylenes. On the other hand, both 1,2,4- and 1,3,5-trisubstituted benzenes are present in significant amounts in the pyrolysis products of polymers prepared with the metathesis catalyst, which proves the presence of a significant content of the head-to-head (HH) and tail-to-tail (TT) linkages in these isomers of polyacetylenes. Contents of the regular (HT) and inverse (HH-TT) monomer linkages (RML and IML, respectively) in polymer chains were determined from the relative amounts of di-, tri-, and tetrasubstituted benzenes found in the Py-GC products.

Porous polyacrylamide monoliths in hydrophilic interaction capillary electrochromatography of oligosaccharides

Capillary electrochromatography (CEC) of oligosaccharides in porous polyacrylamide monoliths has been explored. While it is possible to alter separation capacity for various compounds by copolymerization of suitable separation ligands in the polymerization backbone, "blank" acrylamide matrix is also capable of sufficient resolution of oligosaccharides in the hydrophilic interaction mode. The "blank" acrylamide network, formed with a more rigid crosslinker, provides maximum efficiency for separations (routinely up to 350,000 theoretical plates/m for fluorescently-labeled oligosaccharides). These columns yield a high spatial resolution of the branched glycan isomers and large column permeabilities. From the structural point of view, some voids are observable in the monoliths at the mesoporous range (mean pore radius ca. 35 nm, surface area of 74 m2/g), as measured by intrusion porosimetry in the dry state.

Monolithic organic polymeric columns for capillary liquid chromatography and electrochromatography

This review briefly summarizes the present state of the preparation and use of capillary monolithic columns for liquid chromatography (LC) and electrochromatography (EC). Most important approaches to the preparation of monolithic stationary phases based on organic polymers are outlined and the properties of the monoliths obtained are compared with those of classical particulate phases. A few selected applications of monolithic columns are shown to demonstrate the most important advantages of monolithic capillary columns. It is concluded that both the monolithic and particulate capillary columns are important and that judicious choice of the type suitable for a particular application requires careful consideration of the purpose of the separation and the properties of the solutes to be separated. Monolithic columns are substantially younger than packed ones and thus will require further theoretical and experimental study to further improve their preparation and to enable reliable prediction of their properties and applicability; nevertheless, they are very promising for the future.

Affinity liquid chromatography and capillary electrophoresis of seminal plasma proteins

Interactions of boar, bull, and human seminal plasma proteins with heparin and phosphorylcholine were studied by affinity LC using heparin immobilized to a Toyopearl support. A step gradient elution from 0.15 to 1.50 M NaCl was employed to elute the seminal plasma proteins. Relative amounts of the heparin-binding fraction of seminal plasma proteins (H+) in seminal plasma of three species were determined. Further on, the fraction of seminal plasma proteins interacting with phosphorylcholine-binding proteins (P+) was evaluated. P+ proteins were not found in human seminal plasma and their highest amount was present in bull seminal plasma. A CE method was developed for separation of seminal plasma proteins. Various capillaries and separation conditions were tested; the best resolution was obtained in a bare-silica capillary, with a micellar system consisting of a 0.02 M borate buffer and 0.05 M SDS pH 10.0. The optimized conditions were applied to the identification of the components in boar plasma.

Preparation and testing of stationary phases and modified capillaries for affinity chromatography and affinity capillary electrophoresis of pepsin

Three stationary phases have been prepared for affinity liquid chromatography isolation and separation of porcine and human pepsin. The phases contain 3,5-diiodo-L-tyrosine (DIT) bound to the supports HEMA BIO VS, HEMA BIO E and EPOXY TOYOPEARL. These phases have been tested on a model sample of porcine pepsin A and applied to human pepsin. Fractions have been collected and the chymase activity determined in selected analyses. For affinity CE, capillaries have been prepared by modifying the wall with 3-aminopropyltriethoxysilane, followed either by direct binding of DIT, or by binding L-tyrosine that was subsequently iodated. The dissociation constant K(d) has been determined for the pepsin-DIT complex from the changes in the electrophoretic mobilities.

Dechlorination ability of municipal waste incineration fly ash for polychlorinated phenols

Pathways of pentachlorophenol dechlorination have been investigated on municipal waste incineration fly ash at 200 degrees C under nitrogen atmosphere. Thermodynamic calculations have been carried out for these dechlorination conditions using the method of total Gibbs energy minimization for the whole system consisting of gaseous components, i.e., chlorinated phenols, phenol, hydrogen chloride and the Cu3Cl3 trimer and of solid Cu2O and CuCl2 components. The effects of water, temperature and of the amounts of the reaction components on the thermodynamic equilibrium have been discussed and the experimental results compared with the calculated thermodynamic data.

Topographical properties of polymer films deposited in capillaries for electrophoretic separations of large organic molecules

Topography and thickness of hydrophilic polymer coatings of fused-silica capillaries for capillary electrophoresis (CE) were investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM), and profilometry. Three hydrogels, poly(2-hydroxyethyl methacrylate) [poly(HEMA)], poly(diethylene glycol monomethacrylate) [poly(DEGMA)], and poly(triethylene glycol monomethacrylate) [poly(TEGMA)], were deposited using two procedures, either by simple physical sorption of the polymers, or by derivatization of the capillary wall surface with glycidyl methacrylate (EPMA) followed by polymerization of the appropriate monomers. The performance of the modified capillaries was tested under CE conditions (decrease in the electroosmotic flow, EOF dependence on pH, separation of milk and standard proteins). It has been found that the most important property of the polymer coating is its thickness, whereas its topography and the degree of its hydrophobicity are less significant. Film deposition by physical adsorption is preferable to polymerization on the derivatized surface.

Some potentialities and drawbacks of contemporary size-exclusion chromatography

The present state of the chromatographic techniques based on differentiation of solutes according to their molecular sizes is briefly surveyed. Attention is centred on high-performance techniques applied to purification and characterization of natural macromolecules, and on discussion of the chromatographic approaches to the determination of the molecular masses and molecular mass distributions of both natural and synthetic polymers. The basic requirements on the selection of the separation system and the experimental conditions are summarized, demonstrated on a few examples and critically evaluated.

The importance of capillary electrophoresis, capillary electrochromatography, and ion chromatography in separations of inorganic ions

The importance of capillary electrophoresis (CE), capillary electrochromatography (CEC), and ion chromatography (IC) in inorganic ion analyses is outlined. Methods for improving the reliability of the CE measurements are briefly described. Selectivity optimization in CE analyses of inorganic cations and anions is discussed. Using the Peakmaster program, CE system peaks (system zones, eigenmobilites) and some important CE parameters, such as effective mobilities, electromigration dispersion, indirect UV, and direct conductivity signals, are predicted and compared with experimental analyses.

Dehalogenation potential of municipal waste incineration fly ash. I. General principles

BACKGROUND, AIMS AND SCOPE

It is well known that the fly ash from filters of municipal waste incinerators (MWI-FA) shows dehalogenation properties after heating it to 240-450 degrees C. However, this property is not general, and fly ash samples do not possess dehalogenation ability at all in many cases. Fly ash has a very variable composition, and the state of the fly ash matter therefore plays the decisive role. In the present paper, the function of important components responsible for the dehalogenation activity of MWI-FA is analysed and compared with the model fly ash.

METHODS

With the aim of accounting for the dehalogenation activity of MWI-FA, the following studies of hexachlorobenzene (HCB) dechlorination were performed: The role of copper in dehalogenation experiments was evaluated for five types of metallic copper. The gasification of carbon in MWI-FA was studied in the 250-350 degrees C temperature range. Five different kinds of carbon were used, combined with conventional Cu(o) and activated nanosize copper powder. The dechlorination experiments were also carried out with Cu(II) compounds such as CuO, Cu(OH)2, CuCl2 and CuSO4. The results were discussed from the standpoint of thermodynamics of potential reactions. Based on these results, the model of fly ash was proposed, containing silica gel, metallic copper and carbon. The dechlorination ability of MWI-FA and the model fly ash are compared under oxygen-deficient atmosphere.

CONCLUSIONS

The results show that, under given experimental conditions, copper acts in the dechlorination as a stoichiometric agent rather than as a catalyst. The increased surface activity of copper enhances its dechlorination activity. It was found further that the presence of copper leads to a decrease in the temperature of carbon gasification. The cyclic valence change from Cu(o) to Cu+ or Cu2+ is a prerequisite for the dehalogenation to take place.

RECOMMENDATION AND OUTLOOK

Thermodynamic analysis of the dechlorination effect, as well as the comparison of dechlorination pathways on MWI-FA and model fly ash, can provide a deeper understanding of the studied reaction.

Proteomics of allergens

The present state of proteomics research is generally outlined and the character of allergenic compounds briefly elucidated. The principles of experimental approaches to isolation, purification, identification and characterization of allergens and to monitoring of their biological activity are described, with emphasis on the most modern methods. Selected examples are given for illustration and important results are summarized in tables.

Modification of capillary electrophoresis capillaries by poly(hydroxyethyl methacrylate), poly(diethylene glycol monomethacrylate) and poly(triethylene glycol monomethacrylate)

Modification of capillary electrophoresis (CE) capillaries by poly(hydroxyethyl methacrylate) (poly(HEMA), poly(diethylene glycol monomethacrylate) (poly(DEGMA) and poly(triethylene glycol monomethacrylate) (poly(TEGMA), was studied. Methods based on physical adsorption of the modifier and on its chemical binding were compared on the basis of the electroosmotic flow (EOF) reproducibility, the EOF dependence on the pH, the symmetry of the peak of positively charged tyramine, the stability of the coating and the separation of standard and milk proteins in the modified capillaries. Reproducible coatings were obtained by chemical binding of the polymers to the capillary walls and by coating with a solution of a polymer, as also demonstrated by the atomic force microscopy.

Effects of electrolyte modification and capillary coating on separation of glycoprotein isoforms by capillary electrophoresis

The capillary electrophoresis (CE) running electrolyte composition was optimized for the separation of selected glycoproteins. A good separation of the ovalbumin (OV) and alpha-acid glycoprotein (AAG) isoforms was achieved in 20 mmol x L(-1) N-(2-hydroxyethyl)piperazine-2'-(2-ethanesulfonic acid) (HEPES) at pH 7.0, in 20 mmol x L(-1) phosphate, pH 7.0, or in 25 mmol x L(-1) borate, pH 7.9. Various ways of suppression of the glycoprotein adsorption onto the capillary wall were compared. Alpha, omega-diamine alkanes and bis(aminoalkyl) amines were added to the CE buffers, the optimized concentration being 1 mmol x L(-1) in 20 mmol x L(-1) phosphate buffer. The OV and AAG isoforms could be separated using all the alpha,omega-diamine alkanes or bis(2-aminoethyl)amine. The length of the alkyl chain in the diaminoalkane did not influence the separation. The separation of the isoforms of pollen allergens was also tested. The effects of modification of the capillary wall by succinyl-poly-L-lysine and hydrophilic CElect-P1 capillary were compared. A decrease in the glycoprotein and protein adsorption resulted in an improved separation of the isoforms.

Dechlorination of polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans on fly ash

Dechlorination of commercial mixtures of polychlorinated biphenyls (PCB) as well as polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) on extracted and non-extracted fly ash obtained from municipal waste incinerator (MWI) was studied in closed systems under nitrogen atmosphere at temperatures of 260 degrees C and 340 degrees C. Decomposition results (given as the difference between PCB or PCDD/F molar amounts before and after the experiment (in %) due predominantly to dechlorination reactions) and detoxification data (expressed similarly but related to toxic PCB and PCDD/F congeners only and given in I-TEQ units) are reported. Detoxification of Delor 105/80T at 260 degrees C and 340 degrees C at a loading of 0.65 wt%, was 99.48% and 100%, respectively. The decomposition of Delor 103 at 340 degrees C and for the loading of 0.75 wt%, corresponded to 99.99%. The detoxification capability of PCDD/Fs on extracted and non-extracted fly ash for loading of 130 and 264 ng/0.4 g of fly ash at 340 degrees C made 96 and 98%, respectively.

Validation of a method for determination of phospholipase A2 and melittin in bee venom preparations by capillary electrophoresis

A method was validated for the determination of the 2 main components of bee venom, phospholipase A2 and melittin, by capillary electrophesis (CE). Optimum resolution and selectivity were attained with a running electrolyte of 150 mM phosphoric acid, pH 1.8. The repeatability and day-to-day reproducibility of the migration times were better than 0.36 and 2.8%, respectively. The repeatability and day-to-day reproducibility of the normalized peak areas were better than 1.3 and 2.6%, respectively. The response of the UV detector at 190 nm was linear over < 2 concentration decades, from 0.05 to 1.5 mg/mL, with correlation coefficients of 0.9994 for phospholipase A2 and 0.9997 for melittin. The limits of detection and quantitation were 4.5 and 15 microg/mL, respectively, for phospholipase A2 and 1.6 and 6 microg/mL, respectively, for melittin. The reproducibility of the measurements with 2 different CE instruments was satisfactory; the mean concentration and relative standard deviation (RSD) values for phospholipase A2 and melittin were 14.4% (RSD, 1.3%) and 51.4% (RSD, 1.1%), respectively, with instrument I; the corresponding values with instrument II were 14.5% (RSD, 2.8%) and 52.3% (RSD, 2.2%). The accuracy was estimated by comparison with a liquid chromatographic (LC) method. Differences between the CE and LC measurements were attributed to irreversible adsorption of the analytes on the LC column. The recoveries of phospholipase A2 and melittin with the CE method were 98.8 and 101.7%, respectively.

A study of the distribution of lead, cadmium and copper between water and kaolin, bentonite and a river sediment

Experiments were carried out to monitor the equilibrium distribution of lead, cadmium and copper between an aqueous phase modelling natural water and a solid phase modelling natural sediment, under varying conditions. The aqueous phase was analysed using ETAAS and differential pulse anodic stripping voltammetry (DPASV), whereas XRD and FTIR were used to study the solid phase. Sorption isotherms at constant pH were measured. Conditional distribution constants were calculated as functions of the pH, the time of equilibration and the amount of solid material. The results obtained stress the need for standardization of the approaches to the study of water-sediment interactions in order to be able to evaluate and compare the extensive data from field measurements and to predict these interactions.

High-performance liquid chromatographic determination of some anthraquinone and naphthoquinone dyes occurring in historical textiles

A reversed-phase HPLC method has been developed for identification and quantitation of nine natural quinone dyes and applied to historical textile fibres. A Purospher RP18e column was used with a convex gradient of methanol in a mobile phase of 0.1 M aqueous citrate buffer (pH 2.5) and spectrophotometric diode-array detection at 270 nm. For identification of alizarin, purpurin and xanthopurpurin, occurring together in the madder plant, an isocratic method was used with a methanol-0.2 M acetate buffer (pH 4.3) (75:25) as the mobile phase. After an acid extraction of textile fibres and the analysis of the extracts, alizarin and purpurin were identified and quantitated in three fibres.

High-performance separations in isolation and characterization of allergens

The present state of the use of separation techniques in the identification and characterization of allergens and in the monitoring of the quality of allergenic preparations is critically surveyed. After a brief summary of the range of problems encountered in obtaining and in the application of allergenic preparations and of the principal physico-chemical properties of allergens, chromatographic and electromigration methods of separation of components of these systems and their combinations with immunochemical procedures are discussed, with selected examples of application to real materials. Emphasis is placed on evaluation of the most important analytical parameters, such as reliability of the results, separation efficiency and resolution, and on the most recent results in the field.

Capillary electrophoresis of cytokinins and cytokinin ribosides

A CE separation of cytokinins and cytokinin ribosides and some other purine and pyrimidine bases has been developed. Two electrolyte systems have been tested: 150 mM phosphoric acid, pH 1.8 and 50 mM sodium dodecylsulphate + 20 mM borate, pH 9.2. The migration times were measured and the effects of the solute structures were discussed. Preliminary experiments with plant extracts have been performed to identify the cytokinins and their ribosides. Both the systems can be used, but 150 mM phosphoric acid is better suited for identification of cytokinins in plant extracts, as the electropherograms are subject to fewer interferences.

Size-exclusion liquid chromatography and capillary electrophoresis of pollen allergens

Allergens from the pollen of Phleum pratense, Dactylis glomerata. Arrhenatherum elatius, Secale cereale, Lolium perrene and Festuca sp. were analysed by size-exclusion chromatography (SEC) and capillary electrophoresis (CE). SEC was used for the determination of the molecular masses of main allergens. A CE method, using either 150 mmol/l phosphoric acid (pH 1.8) or a micellar system consisting of 50 mmol/l sodium dodecyl sulphate-20 mmol/l borate (pH 9.35), was developed as a rapid and efficient alternative to SEC, especially for process control of allergenic preparations. The results obtained by the two methods confirmed similarities in the structures of the studied pollen allergens.

Quantitative structure-chromatographic retention relationship study of six underivatized equine estrogens

Underivatized estrone (ES), equilin (EQ), equilenin (EQN) and their corresponding 17 alpha-diols 17 alpha-estradiol (ESD), 17 alpha-dihydroequilin (DHEQ) and 17 alpha-dihydroequilenin (DHEQN) were separated by TLC, RP-HPLC and capillary GC. Their dipole moments (mu) and Randić's connectivity indices ((1)chi) were determined as parameters of importance for the separation. The number of H atoms was taken as an additive structural parameter of importance for the quantitative structure-chromatographic retention relationship study (QSRR). Principal component analysis (PCA) was applied in order to find similarities and dissimilarities between 9 TLC and 10 RP-HPLC systems. PCA indicated that proton donor-proton acceptor interactions play the most important role for the TLC and RP-HPLC separation. The two-dimensional non-linear map of PC variables showed that the keto-estrogens (ES, EQ and EQN) and the corresponding diols (ESD, DHEQ and DHEQN) form two separate clusters. The relationship between GC retention of equine estrogens characterized by Kováts indices (KI), their (1)chi and mu was expressed by the equation KI/100 = al(1)chi+ b/mu(2) + c. The biological activity of the estrogens was related to log 1/mu(2).

Separation of biologically active peptides by capillary electrophoresis and high-performance liquid chromatography

HPLC and CE have been applied to the separation of some newly synthesized substances, including nonapeptides from the intrachinary region of insulin, insulin-like growth factors I and II (IGF I and II) and some penta- and hexapeptides. All the peptides are satisfactorily separated using a reversed-phase HPLC system with a C18 stationary phase and mobile phases of 20-40% acetonitrile (v/v) and 0.2% trifluoroacetic acid in water (v/v). The best CE separation of IGF I and II has been achieved in a 30 mM phosphate buffer (pH 4-5), whereas 150 mM phosphoric acid (pH 1.8) is optimal for the insulin nonapeptides. The latter electrolyte is also suitable for the CE separation of the hexapeptides, as is a micellar system containing 20 mM borate-50 mM sodium dodecyl sulfate (pH 9.0). Complete CE resolution of the D- and L-forms is possible in a 50 mM phosphate buffer (pH 2.5) containing 10 mM beta-cyclodextrin. UV spectrophotometric detection was used throughout, at wavelengths from 190 to 215 nm. The CE procedures are, in general, preferable to HPLC separations, as they exhibit better separation efficiencies, are faster and consume smaller amounts of analytes and reagents.

High-performance liquid chromatographic determination of creatinine in serum, and a correlation of the results with those of the Jaffé and enzymic methods

A high-performance liquid chromatographic method for the determination of creatinine in control sera is reported, based on its separation from deproteinated serum components on the ion-exchange material HEMA Bio 1000 SB and ultraviolet detection at 230 nm. Groups of eleven to fourteen samples of human serum and several control materials were simultaneously analysed by the Jaffé, enzymic ultraviolet and enzymic peroxidase aminophenazone methods. Another group (52-115 sera) was analysed for correlations with spectrophotometric methods. The precision of the chromatographic method ranges between 2.0 and 1.0% (relative standard deviation) for serum creatinine concentrations of 115.1 to 471 mumol/l, respectively. A very good accuracy was found in analyses of reference materials Kontrollogen-L and -LP. Some results of analyses of the other control sera were higher and the other lower than those obtained by the Jaffé and enzymic methods, because both interferences and enzyme inhibitors were encountered. Correlations between the chromatographic and spectrophotometric methods were good.

High-performance liquid chromatographic determination of cholesteryl esters in the blood of obese children

The serum of obese children and adolescents was analyzed for cholesteryl esters. The test substances were first separated from the sample matrix by solvent extraction and thin-layer chromatography and then resolved in a reversed-phase high-performance liquid chromatographic system involving a Separon SGX C18 column and a mobile phase of 2-propanol-acetonitrile (40:60, v/v), with ultraviolet detection at 206 nm. Cholesterol and 10-cholesteryl esters could be separated and determined within ca. 25 min at a flow-rate of 1 ml/min. The method was applied to a study of the effect of external conditions (physical stress, diet) on the content of cholesteryl esters in a test group of obese boys and girls aged from 13 to 16 years. The analyses have demonstrated that the above conditions do not affect the concentrations of the individual cholesteryl esters, although the total cholesterol concentration decreased significantly after spa treatment.

Gas chromatography-mass spectrometry and high-performance liquid chromatographic analyses of thermal degradation products of common plastics

The thermo-oxidation of five commonly used materials, namely low-density polyethylene, retarded polyethylene, paper with a polyethylene foil, a milk package and filled polypropylene, was studied. Capillary gas chromatography and gas chromatography-mass spectrometry were used to analyze the volatile degradation products, while high-performance liquid chromatography was employed to measure polycyclic aromatic hydrocarbons. The results are discussed from the point of view of toxicity of the products.

Determination of narciclasine in serum by reversed-phase high-performance liquid chromatography: comparison of amperometric, ultraviolet photometric and fluorescence detection

Narciclasine was determined in the blood of mice by reversed-phase high-performance liquid chromatography, using a C18 stationary phase and a mobile phase of methanol-0.025 M potassium dihydrogen phosphate (50:50, v/v) of pH 5.5. Amperometric detection at a carbon fibre array working electrode held at +1.8 V (Ag/AgCl) permitted determination down to concentrations of 10 and 15.4 ng ml-1 (at a signal-to-noise ratio of 2) in aqueous solution and in serum, respectively. Fluorescence detection (excitation and emission wavelengths of 360 and 480 nm, respectively) exhibited somewhat poorer sensitivities for aqueous and serum samples: the respective limits of detection were 25 and 32 ng ml-1 at a signal-to-noise ratio of 2. Both the amperometric and the fluorescence detection were free from interference from blood components, but the fluorescence measurement required a post-column pH adjustment. UV photometric detection at 254 nm exhibited detection limits of 15 and 65 ng ml-1 in aqueous samples and in serum, respectively, and suffered from interferences from blood components that strongly absorbed in the ultraviolet region. All three detection techniques exhibited good linearity and precision.

High-performance liquid chromatographic determination of some polar phospholipids in serum

The experimental conditions have been optimized for high-performance liquid chromatographic determination of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM) in serum. The phospholipids are separated on a silica gel column, using a mobile phase of acetonitrile-methanol-water (100:10:18, v/v), with ultraviolet photometric detection at 200 nm. The limit of detection was 0.2 micrograms (in 20 microliters) for natural phospholipids and 2.5 micrograms for synthetic phospholipids; the relative standard deviation was ca. 5%. An alternative detection is tensammetry at a mercury electrode, at a potential of -1.8 V, with an a.c. current frequency of 60 Hz and an amplitude of 20 mV. The tensammetric detection has an advantage in its independence of the structure of the phospholipids. In measurements without a column (flow-injection analysis), the tensammetric detection also yields a somewhat lower limit of detection than photometry (0.15 micrograms per 20 microliters), but this value increases more than ten times in chromatographic detection. The precision is poorer and is more susceptible to interferences. The method was applied to the determination of the above substances in the blood of obese children, as a function of physical stress and spa treatment. It was shown that physical exercise causes a decrease in the contents of PE and PC in the patients. On the other hand, the spa treatment has no pronounced effect on the phospholipid content in the blood.

High-performance liquid chromatography of s-triazines and their degradation products using ultraviolet photometric and amperometric detection

The chromatographic behaviour of eighteen s-triazine derivatives has been studied in a reversed-phase system with a Separon SIC 18 stationary phase and a mobile phase of aqueous sodium dihydrogenphosphate and methanol. The dependences of the capacity factors on the methanol content, the pH and the ionic strength have been obtained. Ultraviolet photometric detection can generally be used whereas amperometric detection with a carbon-fibre array electrode is useful for selective detection of s-triazine hydroxy derivatives, but with a sensitivity poorer than that of photometric detection. The method has been applied to a study of the photolysis of s-triazines and the effect of the substituents and the pH on the photolysis rate.

High-performance liquid chromatography of azobenzene derivatives with spectrophotometric and electrochemical detection

The chromatographic behaviour of azobenzene and fourteen of its derivatives was studied by reversed-phase high-performance liquid chromatography with a C18 stationary phase. The optimal composition of the mobile phase is 9:1 methanol-0.01 M aqueous sodium dihydrogen phosphate which is 0.0002 M in ethylenediaminetetraacetic acid, with a pH of 4.5. The solutes can be detected spectrophotometrically, voltammetrically or polarographically. Spectrophotometric measurement in the visible range is more sensitive than in the UV range (detection limits of 0.04-0.1 ng at 410 nm compared with 0.3-0.5 ng at 265 nm). Voltammetric detection is highly sensitive for hydroxy and amino derivatives [detection limits 0.02-0.09 ng at +0.8 V (Ag-AgCl)], whereas for other substances the detection limits are a few nanograms. Polarographic detection is the least sensitive [detection limits 4-8 ng at -0.6 V (Ag-AgCl)]. All the calibration graphs exhibit good linearity, but spectrophotometric detection yields a wider linear dynamic range. Voltammetric detection is more precise at low solute concentrations (relative standard deviations of the peak heights 0.5-1.0% and 1.0-1.5% for voltammetric and spectrophotometric detection, respectively, with amounts of solute from 1 to 10 ng).

Operational parameters of voltammetric high-performance liquid chromatographic detectors with copper electrodes and application to a determination of some fodder biofactors

Two versions of an amperometric detector with a copper working electrode have been constructed and tested for high-performance liquid chromatography (HPLC). The performance of the detectors was studied using selected amino acids. The dependence of the detector response on the mobile phase flow-rate was studied in the range common in both macro- and microcolumn HPLC (5 microliter/min to 1.0 ml/min). It has been found that the detection sensitivity generally increases with decreasing flow-rate, i.e., the detector response is governed by the rate of the complexation reaction between the cupric ions and the solutes. This fact makes amperometric detection with a copper electrode especially useful for microcolumn separations. For all 20 amino acids studied, calibration curve parameters and detection limits have been determined; the latter vary from 0.4 to 18 ng in the injected volume. The amino acids can also be sensitively detected in a medium of 0.1-1.0 M ammonia, which is promising for the use of strong anion exchangers in amino acid separations. Choline can also be detected at a copper electrode, with a detection limit of 40 ng. An HPLC method with amperometric detection at a copper electrode has been developed for the determination of lysine, methionine and choline in fodder biofactors.

The effect of s-triazine-type pesticides and chlorinated hydrocarbons on lactate dehydrogenase

The effect of pesticides on nontarget organisms was studied by following their effect on enzymes from these organisms in vitro. s-Triazines substituted in positions 2, 4, and 6 behaved as inhibitors of plant and animal lactate dehydrogenase, acting competitively with respect to the coenzyme. The inhibition constants were of the order of 10(-3) M and the structure of the substituents exerted no pronounced effect on the inhibition type and the value of the inhibition constant. Polycyclic chlorinated hydrocarbons were found to be much stronger inhibitors, with inhibition constants of the order of 10(-5) M. These substances inhibit the reaction catalyzed by lactate dehydrogenase not only by reaction with the enzyme, but also by a probable direct reaction with the coenzyme.

Electrochemical detection in HPLC. Part 2. Applications

The range of applications of electrochemical HPLC detectors is outlined and the most important groups of applications are described. Typical examples of determinations are given in tables.

Determination of some tricyclic neuroleptics by reversed-phase high-performance liquid chromatography with ultraviolet and polarographic detection

The liquid chromatographic behaviour of various neuroleptics from the classes of tricyclic dibenzothiepins, -oxepins, -selenepins and similar substances was studied in an ion-pair reversed-phase system using a C4180 chemically bonded stationary phase and a methanol-water-acetic acid mobile phase. The best separation was attained with 70% methanol, 1.8% acetic acid and water, containing 0.005 M sodium pentanesulphonate, 1.2 X 10(-4) M EDTA and 0.5 g/l Na2SO4. For the detection, an ultraviolet spectrophotometric and a polarographic detector were connected in series. The detection was carried out at 254 nm and at a potential of a dropping mercury electrode of -1.0 V (vs. Ag/AgCl). The UV detector is universal, while the polarographic detector does not respond to compounds simultaneously containing two heteroatoms (O, S) in the central seven-membered ring. The detection limits are of the order of one to tens of nanograms, the polarographic detector being somewhat more sensitive for most of the compounds; the error of the determination is a few per cent. The method was applied to the determination of isofloxythepin and oxyprothepin in pharmaceutical preparations.

High-performance liquid chromatography of biologically important pyrimidine derivatives with ultraviolet--voltammetric--polarographic detection

High-performance liquid chromatographic separation of a number of biologically important pyrimidine derivatives was studied in the reversed-phase system. Good results were obtained using a C18 alkyl-bonded silica column and an aqueous citrate--phosphate mobile phase of pH 3.5. All eluted components are detected with the UV absorbance detector at 254 nm, whereas the voltammetric detector with a polymeric carbon-paste electrode detects only derivatives containing oxidizable functional groups (amino, mercapto) and the polarographic detector with a mercury electrode only those with reducible groups (nitro, aza). The signal of the electrochemical detectors is proportional to the number of electroactive groups in the solute molecule. The use of two or three detectors in series thus improves the resolution of complex mixtures and facilitates identification.