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Analytical and Bioanalytical Chemistry (v.357, #3)

Outlook for the development of theoretical foundations for the physical methods of analysis by G. I. Ramendik (pp. 233-240).

The separation between fundamental and applied aspects of analytical chemistry has been studied as a whole and pertaining to physical methods of analysis in particular. Definition of physical methods is given and the role physicists play in the development of these methods is determined. Signal generation processes during analyses based on secondary radiation being emitted by a sample has been studied in general. Physical and instrumental factors have been singled out in equations which give the dependence of the analytical signal on the concentration of an analyte. A quasi-equilibrium approach to the description of generating an analytical signal is proposed. Using this approach we have succeeded, for the first time, in creating a general theoretical basis for various methods of element mass spectrometric analysis using plasma ion sources. Procedures for quantitative analysis without making use of Reference Materials were also developed.The following algorithm is proposed as the next stage in the process of developing the general theoretical basis for physical methods of analysis:1. Formalism of a quasi-equilibrium model to be used for revealing the major processes responsible for generating an analytical signal.2. A detailed analysis of the processes revealed; physical foundations of these methods of analysis to be taken into consideration. Physics is the most fundamental and all-inclusive of the sciences. In fact, physics is the present-day equivalent of what used to be called natural philosophy, from which most of our modern science arose. R.P. Feynmann

Outlook for the development of theoretical foundations for the physical methods of analysis by G. I. Ramendik (pp. 233-240).

The separation between fundamental and applied aspects of analytical chemistry has been studied as a whole and pertaining to physical methods of analysis in particular. Definition of physical methods is given and the role physicists play in the development of these methods is determined. Signal generation processes during analyses based on secondary radiation being emitted by a sample has been studied in general. Physical and instrumental factors have been singled out in equations which give the dependence of the analytical signal on the concentration of an analyte. A quasiequilibrium approach to the description of generating an analytical signal is proposed. Using this approach we have succeeded, for the first time, in creating a general theoretical basis for various methods of element mass spectrometric analysis using plasma ion sources. Procedures for quantitative analysis without making use of Reference Materials were also developed.Formalism of a quasi-equilibrium model to be used for revealing the major processes responsible for generating an analytical signal.A detailed analysis of the processes revealed; physical foundations of these methods of analysis to be taken into consideration.

Selection of internal standards for quantitative analysis by matrix-assisted laser desorption-ionization (MALDI) time-of-flight mass spectrometry by William R. Wilkinson; Arkady I. Gusev; Andrew Proctor; Marwan Houalla; D. M. Hercules (pp. 241-248).

The selection of an appropriate internal standard (IS) for quantification by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is critical for the successful application of quantitative MALDI. Selection of the IS depends on the chemical similarity of the analyte and IS and the mass separation of the analyte and IS as a function of instrumental peak resolution. For the quantification of bovine insulin, a series of internal standards including horse heart cytochrome C, bovine insulin chain B, des-pentapeptide human insulin, and des-octapeptide porcine insulin was investigated. Des-pentapeptide human insulin was found to be the most appropriate internal standard (relative standard deviation of the standard curve slope=2.99%, correlation coefficient=0.988 in the range of 0.5–0.4 μmol/L). Two methods for measuring of the MALDI signal intensity were evaluated, direct peak integration following subtraction of a linear background and non-linear least squares curve fitting. The results obtained with these methods were equivalent.

The selection of an appropriate internal standard (IS) for quantification by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is critical for the successful application of quantitative MALDI. Selection of the IS depends on the chemical similarity of the analyte and IS and the mass separation of the analyte and IS as a function of instrumental peak resolution. For the quantification of bovine insulin, a series of internal standards including horse heart cytochrome C, bovine insulin chain B, des-pentapeptide human insulin, and des-octapeptide porcine insulin was investigated. Des-pentapeptide human insulin was found to be the most appropriate internal standard (relative standard deviation of the standard curve slope = 2.99%, correlation coefficient = 0.988 in the range of 0.5-0.4 μmol/L). Two methods for measuring of the MALDI signal intensity were evaluated, direct peak integration following subtraction of a linear background and non-linear least squares curve fitting. The results obtained with these methods were equivalent.

A possible steady state kinetic model for the atomization process during flame atomic spectrometry: Application to mutual atomization interference effects between group I elements by M. F. Zaranyika; Peter Makuhunga (pp. 249-257).

A possible steady state kinetic model for the atomization process during flame atomic spectrometry is presented. It takes into account the relative rates of (a) thermal dissociation of analyte and interferant metal salts, (b) recombination of counter atom and analyte and interferant atoms, (c) charge transfer between analyte and interferant species, and (d) ion/electron collisional de-ionization. The model predicts a law of mass action type of the thermal dissociation constant in agreement with the currently accepted p-LTE theory. Expressions are derived for the analyte ground state population in the absence and presence of an interferant metal in terms of the rate constants for thermal dissociation of analyte and interferant salts, recombination of counter atom and analyte and interferant atoms, charge transfer between analyte atoms and interferant metal ions and collisional de-ionization, and α and β, the fractions of analyte ions undergoing charge transfer and collisional de-ionization, respectively. The estimation of α and β, and of the various rate constants is discussed. Data are presented showing that the predictions of the model are consistent with the observed interference effects.

Studies on a new cleaning procedure for PFA-surfaces by M. Schuster; S. Ringmann; R. Gärtner; X. Lin; J. Dahmen (pp. 258-265).

An easy to perform procedure is presented for cleaning PFA (“Perfluoroalkoxy”) molds, especially for demanding and large scale applications. The leaching of PFA-vessels with diluted aqueous solutions of hydrogen peroxide, ammonia and triethanolamine (TEA) reveals cleaning effects comparable to the effectiveness of more hazardous procedures, such as leaching with concentrated nitric acid or with cleaning solutions containing hydrofluoric acid. The method is suitable even for demanding applications in the field of semiconductor production. Differential thermal desorption analysis (DTDA) gave no hints on chemical “carry over” effects of the organic ligand from pre-cleaned PFA molds to wafer surfaces. Furthermore, the results of TXRF-studies on Si-wafers have opened up promising prospects for the employment of TEA in wafer cleaning technology itself. The Fe deposition on Si-wafer surfaces from Fe-spiked SC-1-type cleaning solutions can evidently be suppressed for Fe concentrations up to 0.1 mg/l by the addition of TEA in 10⁴-fold excess.

Studies on a new cleaning procedure for PFA-surfaces by M. Schuster; S. Ringmann; R. Gärtner; X. Lin; J. Dahmen (pp. 258-265).

Pure graphite as a reference material for the determination of trace elements – an interlaboratory collaborative study by W. Bögershausen; R. Cicciarelli; B. Gercken; E. König; V. Krivan; R. Müller-Käfer; J. Pavel; H. Seltner; J. Schelcher (pp. 266-273).

Seven synthetic graphite powders of different grade of purity were analyzed by means of INAA, WDXRF, EDXRF, DC-OES directly and using ICP-MS, ICP-OES, ETAAS and FAAS in combination with various sample preparation techniques. On the basis of a statistical evaluation of the results obtained, for the trace elements Al, Ca, Cr, Cu, Fe, Mn and Ni, reference values were established and, for the elements As, Co, Mg, Mo, Pb, Sb, Si, Sr, Ti, V, Zn and Zr, informative values are given. The analyzed reference materials are commercially available.

Pure graphite as a reference material for the determination of trace elements — an interlaboratory collaborative study by W. Bögershausen; R. Cicciarelli; B. Gercken; E. König; V. Krivan; R. Müller-Käfer; J. Pavel; H. Seltner; J. Schelcher (pp. 266-273).

Determination of tin in marine sediment slurries by electrothermal atomic absorption spectrometry using palladium-magnesium nitrate as chemical modifier by P. Bermejo-Barrera; Carmen Barciela-Alonso; Consuelo González-Sixto; Adela Bermejo-Barrera (pp. 274-278).

A method was optimized for the determination of tin in slurries of marine sediment samples using palladium-magnesium nitrate as chemical modifier and Triton X-100 (0.1%) surfactant as stabilizer. To obtain a complete pyrolysis of the slurry sample, two charring steps were used, the first at 480 °C and the second at 1300 °C. The precision and accuracy of the method were studied using the Reference Material PACS-1 (marine sediment) from National Research Council Canada. The detection limit (LOD) was 57.6 μg kg^-1. The method was applied to the determination of tin in marine sediment samples from the Galicia coast.

Determination of tin in marine sediment slurries by electrothermal atomic absorption spectrometry using palladium-magnesium nitrate as chemical modifier by Pilar Bermejo-Barrera; Carmen Barciela-Alonso; Consuelo González-Sixto; Adela Bermejo-Barrera (pp. 274-278).

A method was optimized for the determination of tin in slurries of marine sediment samples using palladium-magnesium nitrate as chemical modifier and Triton X-100 (0.1%) surfactant as stabilizer. To obtain a complete pyrolysis of the slurry sample, two charring steps were used, the first at 480 °C and the second at 1300 °C. The precision and accuracy of the method were studied using the Reference Material PACS-1 (marine sediment) from National Research Council Canada. The detection limit (LOD) was 57.6 μg kg⁻¹. The method was applied to the determination of tin in marine sediment samples from the Galicia coast.

New human hair certified reference material for methylmercury and trace elements by J. Yoshinaga; Masatoshi Morita; Kensaku Okamoto (pp. 279-283).

A new human hair certified reference material (NIES CRM No. 13) for mercury speciation and trace element analysis was prepared at the National Institute for Environmental Studies (NIES), Environmental Agency of Japan. Scalp hair from Japanese males, which is identical with the original material for the previous human hair CRM (NIES CRM No. 5), was used. Special attention was paid to reduce contamination from a grinding vessel during the preparation procedure. A newly-prepared ceramic/Teflon disc mill was used for cryogenic grinding of the hair. 1,000 bottles (3 g each) were produced after sieving and blending of the hair powder. Certified values for total mercury and methylmercury, as well as other trace elements of toxicological and nutritional significance (antimony, cadmium, copper, lead, selenium, and zinc), were determined based on analyses from extensive collaborations. Reference values for 12 elements (aluminium, arsenic, barium, calcium, cobalt, iron, magnesium, manganese, silver, sodium, sulfur and vanadium) were also given.

New human hair certified reference material for methylmercury and trace elements by Jun Yoshinaga; Masatoshi Morita; Kensaku Okamoto (pp. 279-283).

A new human hair certified reference material (NIES CRM No. 13) for mercury speciation and trace element analysis was prepared at the National Institute for Environmental Studies (NIES), Environmental Agency of Japan. Scalp hair from Japanese males, which is identical with the original material for the previous human hair CRM (NIES CRM No. 5), was used. Special attention was paid to reduce contamination from a grinding vessel during the preparation procedure. A newly-prepared ceramic/Teflon disc mill was used for cryogenic grinding of the hair. 1, 000 bottles (3 g each) were produced after sieving and blending of the hair powder. Certified values for total mercury and methylmercury, as well as other trace elements of toxicological and nutritional significance (antimony, cadmium, copper, lead, selenium, and zinc), were determined based on analyses from extensive collaborations. Reference values for 12 elements (aluminium, arsenic, barium, calcium, cobalt, iron, magnesium, manganese, silver, sodium, sulfur and vanadium) were also given.

Investigation of potential-sensitive fluorescent dyes for application in nitrate sensitive polymer membranes by Gerhard J. Mohr; Frank Lehmann; Ralf Östereich; Ivana Murkovic; O. S. Wolfbeis (pp. 284-291).

The applicability of various potential-sensitive dyes (PSD) for optical sensing of anions is reported. Specifically, nitrate-responsive polymer membranes have been developed which are composed of a plasticized polymer, an anion exchange catalyst, and a fluorescent dye. On exposure to nitrate, the fluorescence intensity of such membranes increases, while the wavelengths of the excitation and emission maxima remain virtually unchanged. The membranes typically are 2–4 μm thick and exhibit highest sensitivity to nitrate in the 2 to 200 mgl^–1 range. Signal changes on exposure to 100 mmol/l nitrate can be as high as +300%. The detection limit is 0.2 mgl^–1. The cationic PSD octadecyl acridine organe was tested in combination with a tin-organic and an indium-organic anion carrier rather than with tridodecylmethylammonium chloride, but both carriers were found to display no improved selectivity.

The applicability of various potential-sensitive dyes (PSD) for optical sensing of anions is reported. Specifically, nitrate-responsive polymer membranes have been developed which are composed of a plasticized polymer, an anion exchange catalyst, and a fluorescent dye. On exposure to nitrate, the fluorescence intensity of such membranes increases, while the wavelengths of the excitation and emission maxima remain virtually unchanged. The membranes typically are 2–4 μm thick and exhibit highest sensitivity to nitrate in the 2 to 200 mgl⁻¹ range. Signal changes on exposure to 100 mmol/1 nitrate can be as high as +300%. The detection limit is 0.2 mgl⁻¹. The cationic PSD octadecyl acridine organe was tested in combination with a tin-organic and an indium-organic anion carrier rather than with tridodecylmethylammonium chloride, but both carriers were found to display no improved selectivity.

In-situ characterization of thin polymer films for applications in chemical sensing of volatile organic compounds by spectroscopic ellipsometry by Karin Spaeth; G. Kraus; Günter Gauglitz (pp. 292-296).

Polymer coatings are applied in many kinds of chemical sensors. The interaction with organic vapours changes the physical properties of the coating material. For optical sensors, changes in the coating volume and the complex refractive index are most important. Spectroscopic ellipsometry has been applied for the first time to the in-situ characterization of thin poly(dimethylsiloxane) films in contact with tetrachloroethene, toluene and cyclohexane vapours. The differences in bulk refractive index between organic solvent and polymer are large for toluene and tetrachloroethene and both effects were studied separately. Cyclohexane has a bulk refractive index very close to the investigated poly(dimethylsiloxane) films. Therefore the calculation of the volume fraction of the analyte in the mixture phase with the polymer is subject to large errors for vapour concentrations below 5000 ppm.

In-situ characterization of thin polymer films for applications in chemical sensing of volatile organic compounds by spectroscopic ellipsometry by Karin Spaeth; Gerolf Kraus; Günter Gauglitz (pp. 292-296).

Reagentless amperometric biosensor highly sensitive to hydrogen peroxide based on the incorporation of Meldola Blue, fumed-silica and horseradish peroxidase into carbon paste by H. Liu; Zhanen Zhang; Yubo Fan; Miao Dai; Xiaolin Zhang; Jianjun Wei; Zunan Qiu; Hongbin Li; Xinxin Wu; Jiaqi Deng; Deyao Qi (pp. 297-301).

A reagentless amperometric sensor highly sensitive to H₂O₂ has been prepared by incorporating fumed silica, horseradish peroxidase (HRP) and Meldola Blue into carbon paste. The efficient mediating ability to shift electrons between HRP and the carbon paste electrode via Meldola Blue was investigated by cyclic voltammetric and amperometric measurements. Reproducibility, response time, detection limit, selectivity and effects of applied potential, temperature and pH on the response of the sensor are reported. The high sensitivity of the sensor with a detection limit of 0.1 μmol/l arose from the high efficiency of the bioelectrocatalytic reduction of hydrogen peroxide via HRP and Meldola Blue. The dependence of the Michaelis-Menten constant on the applied potential and the mediator concentration has been investigated and the results are presented.

Reagentless amperometric biosensor highly sensitive to hydrogen peroxide based on the incorporation of Meldola Blue, fumed-silica and horseradish peroxidase into carbon paste by Haiying Liu; Zhanen Zhang; Yubo Fan; Miao Dai; Xiaolin Zhang; Jianjun Wei; Zunan Qiu; Hongbin Li; Xinxin Wu; Jiaqi Deng; Deyao Qi (pp. 297-301).

A reagentless amperometric sensor highly sensitive to H₂O₂ has been prepared by incorporating fumed silica, horseradish peroxidase (HRP) and Meldola Blue into carbon paste. The efficient mediating ability to shift electrons between HRP and the carbon paste electrode via Meldola Blue was investigated by cyclic voltammetric and amperometric measurements. Reproducibility, response time, detection limit, selectivity and effects of applied potential, temperature and pH on the response of the sensor are reported. The high sensitivity of the sensor with a detection limit of 0.1 μmol/1 arose from the high efficiency of the bioelectrocatalytic reduction of hydrogen peroxide via HRP and Meldola Blue. The dependence of the Michaelis-Menten constant on the applied potential and the mediator concentration has been investigated and the results are presented.

Amperometric methylene blue-mediated sensor highly sensitive to hydrogen peroxide based on a composite membrane of regenerated silk fibroin and poly-vinyl alcohol as immobilization matrix for horseradish peroxidase by H. Liu; Jianghong Qian; Yongcheng Liu; Tongyin Yu; Jiagi Deng; Deyao Qi (pp. 302-307).

Horseradish peroxidase (HRP) was effectively entrapped in a novel composite membrane of poly-vinyl alcohol and regenerated silk fibroin, and IR was employed to provide a useful insight into the structure of the composite membrane. A methylene blue-mediated sensor highly sensitive to hydrogen peroxide was constructed, which was based on the immobilization of HRP in the composite membrane. Cyclic voltammetry and amperometric measurement were utilized to demonstrate the feasibility of electron communication between immobilized HRP and a glassy carbon electrode in the bioelectrocatalytic reduction of hydrogen peroxide via methylene blue. Performance and characteristics of the sensor were evaluated with regard to response time, detection limit, selectivity, and dependence on temperature and pH as well as operating and storage stability. The sensor possesses a variety of characteristics including high sensitivity, rapid response time and a low detection limit of 0.1 μmol/L.

Amperometric methylene blue-mediated sensor highly sensitive to hydrogen peroxide based on a composite membrane of regenerated silk fibroin and poly-vinyl alcohol as immobilization matrix for horseradish peroxidase by Haiying Liu; Jianghong Qian; Yongcheng Liu; Tongyin Yu; Jiagi Deng; Deyao Qi (pp. 302-307).

Horseradish peroxidase (HRP) was effectively entrapped in a novel composite membrane of poly-vinyl alcohol and regenerated silk fibroin, and IR was employed to provide a useful insight into the structure of the composite membrane. A methylene bluemediated sensor highly sensitive to hydrogen peroxide was constructed, which was based on the immobilization of HRP in the composite membrane. Cyclic voltammetry and amperometric measurement were utilized to demonstrate the feasibility of electron communication between immobilized HRP and a glassy carbon electrode in the bioelectrocatalytic reduction of hydrogen peroxide via methylene blue. Performance and characteristics of the sensor were evaluated with regard to response time, detection limit, selectivity, and dependence on temperature and pH as well as operating and storage stability. The sensor possesses a variety of characteristics including high sensitivity, rapid response time and a low detection limit of 0.1 μmol/L.

Novel dissolution procedure using a mixture of manganese dioxide and hydrochloric acid for the matrix-independent determination of gold by P. Chattopadhyay; M. Mistry (pp. 308-313).

A mixture of manganese dioxide and hydrochloric acid has been used for the accurate and precise determination of gold in various gold-bearing matrices. Results of intermethod comparison studies, F-test on variances, Mann-Whitney U-test, Spearman rank correlation and regression analyses are presented. The recommended method can be applied to a quality control programme and for the evaluation of reference materials. Various standard reference materials (SRM) of diverse matrices have been examined to check the validity of the method and the results were found to be in very good agreement with the certified data. Sample decomposition is straight forward [1–10 g sample (roasted at 600–700 °C)+5 g of MnO₂+30 mL of 2 mol/L HCl]. Gold is coprecipitated with potassium tellurite using tin (II) chloride solution. The precipitate is extracted into toluene and finally stripped back into aqua-regia solution for final nebulization into an air-acetylene flame for atomic absorption spectrophotometry. The method is very simple and easily adaptable, and more convenient than conventional methods involving aqua regia or a hydrobromic acid-bromine water mixture.

Novel dissolution procedure using a mixture of manganese dioxide and hydrochloric acid for the matrix-independent determination of gold by P. Chattopadhyay; M. Mistry (pp. 308-313).

A mixture of manganese dioxide and hydrochloric acid has been used for the accurate and precise determination of gold in various gold-bearing matrices. Results of intermethod comparison studies, F-test on variances, Mann-Whitney U-test, Spearman rank correlation and regression analyses are presented. The recommended method can be applied to a quality control programme and for the evaluation of reference materials. Various standard reference materials (SRM) of diverse matrices have been examined to check the validity of the method and the results were found to be in very good agreement with the certified data. Sample decomposition is straight forward [1–10 g sample (roasted at 600–700 °C) + 5 g of MnO₂ + 30 mL of 2 mol/L HCl]. Gold is coprecipitated with potassium tellurite using tin (II) chloride solution. The precipitate is extracted into toluene and finally stripped back into aqua-regia solution for final nebulization into an airacetylene flame for atomic absorption spectrophotometry. The method is very simple and easily adaptable, and more convenient than conventional methods involving aqua regia or a hydrobromic acidbromine water mixture.

Determination of Hf, Sc and Y in geological samples together with the rare-earth elements by N. Lihareva; Michel Delaloye (pp. 314-316).

A method is described for the determination of Hf, Sc and Y simultaneously with the REE in geological materials. An earlier method for REE separation from major elements was studied with the aim to apply it also to the determination of Hf, Sc and Y. Sample decomposition was carried out by melting with LiBO₂. The method involves separation and concentration stages, using the cation-exchange resin DOWEX AG 50W-X8. Matrix elements were eluted with 2 mol/l HCl, whereas 6 mol/l HNO₃ with oxalic acid and 8 mol/l HNO₃ were used to elute the elements to be determined. Some of the matrix elements could not be completely removed. This effect as well as the recovery rates of the determined elements were investigated. The measurements were performed by ICP-AES. Spectral interferences were also tested.

Determination of Hf, Sc and Y in geological samples together with the rare-earth elements by Nadejda Lihareva; Michel Delaloye (pp. 314-316).

A method is described for the determination of Hf, Sc and Y simultaneously with the REE in geological materials. An earlier method for REE separation from major elements was studied with the aim to apply it also to the determination of Hf, Sc and Y. Sample decomposition was carried out by melting with LiBO₂. The method involves separation and concentration stages, using the cation-exchange resin DOWEX AG 50W-X8. Matrix elements were eluted with 2 mol/1 HCl, whereas 6 mol/1 HNO₃ with oxalic acid and 8 mol/1 HNO₃ were used to elute the elements to be determined. Some of the matrix elements could not be completely removed. This effect as well as the recovery rates of the determined elements were investigated. The measurements were performed by ICP-AES. Spectral interferences were also tested.

Improvement of an old spectrophotometric method for the microdetermination of ascorbic acid by the use of a micellar medium by P. B. Issopoulos; Sofia E. Salta (pp. 317-320).

₃]²⁺. Whereas the initial method is carried out in an aqueous solution, the improved one employs an aqueous micellar medium formed by the cationic surfactant cetylpyridinium bromide (CPBR). The λmax in both methods is the same, i.e. 510 nm. The mean apparent molar absorptivity (ɛ) and Sandell’s sensitivity (Ss) were calculated as ɛ=2.10×10⁴ Lmol^-1 cm^-1 and Ss=8.37 ng cm^-2 for the initial procedure, and ɛ=2.62×10⁴ Lmol^-1 cm^-1 and Ss=6.72 ng cm^-2 for the improved one. The regression line equation for the improved method was: A=1.487×10^-1C −1.415×10^-2 (r=0.9998). The accuracy and the precision of the improved method were investigated and the conclusions were satisfactory. The results obtained for ASCA by both the described method and an official one, were statistically compared by means of the Student’s t-test and by the variance ratio F-test; and no significant difference was observed.

Improvement of an old spectrophotometric method for the microdetermination of ascorbic acid by the use of a micellar medium by Prodromos B. Issopoulos; Sofia E. Salta (pp. 317-320).

A long known indirect method for the spectrophotometric determination of the ascorbic acid (ASCA) has been improved. The initial method, as well as the improved one is based on the same coupled redox-complexation reaction between Fe(III) and ASCA, the resulting Fe(II) reacts with o-phenanthroline (o-Phen) to form the well-known orange-red coloured ferroin chelate complex [Fe(II)-(o-Phen)₃]²⁺. Whereas the initial method is carried out in an aqueous solution, the improved one employs an aqueous micellar medium formed by the cationic surfactant cetylpyridinium bromide (CPBR). The λmax in both methods is the same, i.e. 510 nm. The mean apparent molar absorptivity (ε) and Sandell’s sensitivity (Ss) were calculated as ε = 2.10 × 10⁴ Lmol⁻¹ cm⁻¹ and Ss = 8.37 ng cm⁻² for the initial procedure, and ε = 2.62 × 10⁴ Lmol⁻¹ cm⁻¹ and Ss = 6.72 ng cm⁻² for the improved one. The regression line equation for the improved method was: A = 1.487 × l0⁻¹C −1.415 × 10⁻² (r = 0.9998). The accuracy and the precision of the improved method were investigated and the conclusions were satisfactory. The results obtained for ASCA by both the described method and an official one, were statistically compared by means of the Student’s ttest and by the variance ratio Ftest; and no significant difference was observed.

Application of ion exclusion chromatography (IEC) for the determination of sugar and carboxylic acids in hydrolysates from carbohydrate containing residues by H. P. Bipp; K. Fischer; D. Bieniek; A. Kettrup (pp. 321-325).

The oxidation of carbohydrate containing biomass residues by nitric acid yields several organic acids, especially sugar acids. To improve existing methods for the separation of such substance combinations by ion exclusion chromatography, the influence of temperature and eluant (proton) concentration on the retention behaviour and separation of 31 analytes belonging to substance groups like sugar acids, lactones, hydroxy-, mono- and polycarboxylic acids was checked with a Merck cation exchange column “Polyspher OA-HY”. By a combination of two chromatographic parameter sets the chromatographic versatility could be enhanced. The developed chromatographic method is a useful tool for the analytical characterisation of organic acids in hydrolysates of biomass residues.

The oxidation of carbohydrate containing biomass residues by nitric acid yields several organic acids, especially sugar acids. To improve existing methods for the separation of such substance combinations by ion exclusion chromatography, the influence of temperature and eluant (proton) concentration on the retention behaviour and separation of 31 analytes belonging to substance groups like sugar acids, lactones, hydroxy-, mono- and polycarboxylic acids was checked with a Merck cation exchange column “Polyspher OA-HY”. By a combination of two Chromatographic parameter sets the Chromatographic versatility could be enhanced. The developed Chromatographic method is a useful tool for the analytical characterisation of organic acids in hydrolysates of biomass residues.

Determination of phenolic compounds in waste water by solid-phase micro extraction by M. Möder; S. Schrader; U. Franck; P. Popp (pp. 326-332).

The solid-phase micro extraction technique (SPME) using a polyacrylate coated fibre has been examined with the aim to determine phenolic components in strong contaminated waste water. Considering the high contents and the great variety of accompanying organic material, the feasibility of SPME-GC-MS analysis has been tested. In this connection the influence of matrix components on the SPME results are discussed. EPA-604 phenols and some other phenolic components have been sampled by a polar fibre under standard conditions and in original waste water. The effects of defined concentrations of humic acids and surfactants on the recovery of phenols have been studied. The influence of other organics, e.g. hexachlorocyclohexane isomers, on the recoveries of phenols are discussed. Finally, a comparison between results of a liquid-liquid extraction and SPME describes the performance of SPME regarding the phenol analysis of strong-loaded water.

Determination of phenolic compounds in waste water by solid-phase micro extraction by M. Möder; S. Schrader; U. Franck; P. Popp (pp. 326-332).

Monitoring degradation processes of explosives by HPLC analysis with UV- and amperometric detection by Kathrin Spiegel; T. Welsch (pp. 333-337).

The impact of spilled explosives, their by-products and degradation products on human beings and the environment has been recognised as a serious problem at areas of existing and former ammunition plants. In nature, aerobic and anaerobic degradation processes of explosives and their accompanying compounds yield polar contaminants with relatively high water solubilities. Most are potentially carcinogenic and mutagenic. An HPLC method applying UV-detection for nitroaromatic compounds and amperometric detection for aminoaromatic and phenolic compounds was used for monitoring the degradation of explosives in a polluted groundwater sample under natural conditions. Analysis was performed by direct injection of aliquots of the sample after exposition to daylight for different periods of time.

Monitoring degradation processes of explosives by HPLC analysis with UV- and amperometric detection by Kathrin Spiegel; Thomas Welsch (pp. 333-337).

Determination of theophylline in serum by high performance liquid chromatography/mass spectrometry with atmospheric pressure chemical-ionization (APCI HPLC/MS) by F. Susanto; H. Reinauer (pp. 338-344).

A method for the determination of theophylline (TH), without derivatization, in serum by isotope dilution mass spectrometry using labelled [1, 3-¹⁵N₂-2-¹³C]theophylline (LTH) as internal standard is described. After deproteinization, the analyte is directly injected into a high performance liquid chromatography – mass spectrometer operating with atmospheric-pressure chemical-ionization (APCI HPLC/MS). The concentrations of TH in sera measured by APCI HPLC/MS are compared with results from gas chromatography – isotope dilution mass spectrometry (GC-ID/MS), high performance liquid chromatography (HPLC) and fluorescence polarization immunoassay (FPIA). The accuracy, precision and recovery of the APCI HPLC/MS and GC-ID/MS methods are discussed. The coefficient of variation (CV) determined from duplicate samples was less than 2%. The detection limit was 10 ng/ml at a signal-to-noise ratio of 3:1.

A method for the determination of theophylline (TH), without derivatization, in serum by isotope dilution mass spectrometry using labelled [1,3-¹⁵N₂-2-¹³C]theophylline (LTH) as internal standard is described. After deproteinization, the analyte is directly injected into a high performance liquid chromatography — mass spectrometer operating with atmosphericpressure chemical-ionization (APCI HPLC/MS). The concentrations of TH in sera measured by APCI HPLC/MS are compared with results from gas chromatography — isotope dilution mass spectrometry (GC-ID/MS), high performance liquid chromatography (HPLC) and fluorescence polarization immunoassay (FPIA). The accuracy, precision and recovery of the APCI HPLC/MS and GC-ID/MS methods are discussed. The coefficient of variation (CV) determined from duplicate samples was less than 2%. The detection limit was 10 ng/ml at a signal-to-noise ratio of 3:1.

Acoustically levitated droplets – a new tool for micro and trace analysis by E. Welter; B. Neidhart (pp. 345-350).

First experiences with the technique of acoustical levitation of droplets in the field of analytical and atmospheric chemistry are reported. Acoustical levitation enables the contactless handling of solid and liquid microsamples. This avoids adsorption of analyte at and desorption of contaminants from container walls especially for liquid samples. Common experiments of sample preparation procedures were conducted in levitated drops like liquid/liquid extractions, solvent exchange, and analyte enrichment by evaporation of the solvent. A first approach was made to use acoustical levitation for the simulation of atmospheric chemistry situations.

Acoustically levitated droplets — a new tool for micro and trace analysis by E. Welter; B. Neidhart (pp. 345-350).

Determination of iron and lead by flame atomic absorption spectrometry after preconcentration with sepiolite by A. R. Türker; Hüseyin Bagˇ; Baki Erdogˇan (pp. 351-353).

By using a new adsorbent (sepiolite) an adsorption-elution and atomic absorption spectrometric method has been developed for the preconcentration and determination of Fe and Pb. Recoveries of the analytes were 82 ± 3% for Fe and 91 ± 2% for Pb at 95% confidence level. For Cu it was only 5 ± 1%. The recovery of iron could be increased to about 97 ± 1% by complexing with EDTA, the recovery of copper only to 57 ± 2%. The optimised method was applied to the determination of lead in metal materials (e.g. brass).

Determination of iron and lead by flame atomic absorption spectrometry after preconcentration with sepiolite by A. Rehber Türker; Hüseyin Bağ; Baki Erdoğan (pp. 351-353).

By using a new adsorbent (sepiolite) an adsorptionelution and atomic absorption spectrometric method has been developed for the preconcentration and determination of Fe and Pb. Recoveries of the analytes were 82 ± 3% for Fe and 91 ± 2% for Pb at 95% confidence level. For Cu it was only 5 ± 1%. The recovery of iron could be increased to about 97 ± 1% by complexing with EDTA, the recovery of copper only to 57 ± 2%. The optimised method was applied to the determination of lead in metal materials (e.g. brass).

Determination of N-n-alkyl-dimethylmorpholines and their metabolites by high resolution GC/MS by H. Klöppel; H. Jürling (pp. 353-355).

An analytical method is described to determine simultaneously cis/trans N-n-alkyl-dimethylmorpholines and their metabolites, the 4-(ω-carboxy-n-alkyl) cis/trans-2,6-dimethylmorpholines by pyrolytic alkylation and high resolution GC/MS in aqueous systems and sediments. The substances in the sediment phase were analyzed by GC/MS after extraction with methanol and water, substances in the water phase could be directly determined by GC/MS. The analytical procedure also allows the determination of further carboxylic acids in complex aqueous systems.

Determination of N-n-alkyl-dimethylmorpholines and their metabolites by high resolution GC/MS by H. Klöppel; H. Jürling (pp. 353-355).

Field determination of molybdenum in soils by S. Chikhalikar; K. S. Patel (pp. 355-356).

A new procedure for the field characterization of the available amount of molybdenum in soil extract is described. It is based on the preconcentration of the Mo(V)-SCN^– complex into toluene solution of N-octylacetamide (OAA) and subsequent heating of the extract for ≈ 10 min at 60° C over a water bath. The molar absorptivity of the complex is (3.50) × 10⁴ 1 mole^–1 cm^–1 at λ_max 470 nm. The detection limit of the method is 4 ppb Mo. It provides a significantly increased tolerance limit for iron (up to 1000 ppm) and is applicable to the field characterization of Mo in soil extracts.

Field determination of molybdenum in soils by S. Chikhalikar; K. S. Patel (pp. 355-356).

A new procedure for the field characterization of the available amount of molybdenum in soil extract is described. It is based on the preconcentration of the Mo(V)-SCN⁻ complex into toluene solution of N-octylacetamide (OAA) and subsequent heating of the extract for ≈ 10 min at 60° C over a water bath. The molar absorptivity of the complex is (3.50) × 10⁴ 1 mole^-1 cm^-1 at λ_max 470 nm. The detection limit of the method is 4 ppb Mo. It provides a significantly increased tolerance limit for iron (up to 1000 ppm) and is applicable to the field characterization of Mo in soil extracts.

Determination of trigonelline in green and roasted coffee from single column ionic chromatography by María J. Martín; F. Pablos; M. Angel Bello; A. Gustavo González (pp. 357-358).

Trigonelline can be determined in green and roasted coffee extracts by a ion chromatographic method on a single column filled with polybutadiene-maleic acid (PBDMA) coated on silicia, 2 mmol/L aqueous HCl (pH 3) as eluent and UV detection at 254 nm. The merits of the new method are investigated.

Determination of trigonelline in green and roasted coffee from single column ionic chromatography by María J. Martín; Fernando Pablos; M. Angel Bello; A. Gustavo González (pp. 357-358).

Trigonelline can be determined in green and roasted coffee extracts by a ion Chromatographic method on a single column filled with polybutadiene-maleic acid (PBDMA) coated on silicia, 2 mmol/L aqueous HC1 (pH 3) as eluent and UV detection at 254 nm. The merits of the new method are investigated.

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Analytical and Bioanalytical Chemistry (v.357, #3)

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Analytical and Bioanalytical Chemistry (v.357, #3)