Comparative study of the determination of peroxomonosulfate, in the presence of other oxidants, by capillary zone electrophoresis, ion chromatography, and photometry.

Several methods for quantitative determination of peroxomonosulfate in detergents, in the presence of other oxidants, have been investigated. The photometric technique applied was based on the well-known starch-iodine reaction. The oxidizing agent was quantified by determining the amount of iodine produced. The influence of other oxidants present was examined. Ion analysis was performed by capillary zone electrophoresis (CZE) and ion chromatography (IC). Because peroxomonosulfate in detergents is always accompanied by sulfate, the main goal was to separate the sulfur species without causing the decomposition of the unstable peroxomonosulfate ion. The sulfur species could be separated within less than 4 min by CZE with a pyromellitic acid electrolyte at pH 3.5 to 5.0. Sulfate and peroxomonosulfate were separated by IC within 11 min by use of a phthalic acid mobile phase at pH 3.0. The peroxomonosulfate content was determined by calibration. The calibration plot was linear from 5 to 50 microg mL(-1) SO5(2-) for IC and from 7.3 to 182.3 microg mL(-1) SO5(2-) (corresponding to 20 to 500 microg mL(-1) triple salt) for CZE.

Voltammetric trace analysis of DNA and RNA.

A voltammetric determination of DNA/RNA is described. The new aspect is the use of the extracellular endonuclease Serratia marcescens in the sample preparation. Using this enzyme it is possible to determine DNA/ RNA with a detection limit of 2-5 pg/mL. This satisfies the requirements of the WHO and the FDA.

Sulfur speciation by capillary zone electrophoresis: conditions for sulfite stabilization and determination in the presence of sulfate, thiosulfate and peroxodisulfate.

Capillary zone electrophoresis (CZE) was used for the separation of the sulfur species SO3(2-), SO4(2-), S2O(3-) and S2O8(2-). Using an electrolyte system with 9.5 mmol L(-1) potassium chromate as UV-absorbing probe and 1 mmol L(-1) diethylenetriamine (DETA) as electroosmotic flow modifier, various possibilities for the stabilization of sulfite and electrophoretic separation of the sulfur anions were investigated. By adding 5% propanol as a stabilizer to both the working electrolyte and the sample solution, a good stabilization for sulfite and a separation of the sulfur anions in a short analysis time (4 min) was achieved. The advantages by using propanol instead of other stabilizers often used in analytical techniques are discussed. The electrophoretic separation of the sulfur anions was optimized with respect to the pH of the working electrolyte and concentration of the electroosmotic flow modifier (DETA). The detection limits achieved for SO3(2-), SO4(2-), S2O3(2-) and S2O8(2-) were 0.35, 0.25, 0.78 and 0.80 mg L(-1), respectively.

[Chemometric evaluation of in vitro studies of bioavailability of zinc in selected foodstuffs and menus]. / Chemometrische Auswertung von in-vitro-Untersuchungen zur Bioverfügbarkeit des Zinks in ausgewählten Lebensmitteln und Menüs.

Using simulated digestion-juices for extraction of 31 foodstuffs and 4 menues, 7 variables were subjected to measuring various polarographic parameters as well as determining antagonists of zinc absorbtion, and were evaluated by chemometric methods. Correlations between the different variables were determined by factor analysis, and 4 factors were extracted. By means of cluster analysis it was established whether similarities between the 31 foodstuffs and 4 menues are existing. The resulting division into groups of bioavailability (high, medium, small) was compared with references based on in vivo methods. A high agreement was established. The found clusters were characterized by discriminance analysis allowing an arrangement of further foodstuffs into different groups of bioavailability.

Solid-phase extraction of the chromium(III)-diphenylcarbazone complex prior to ion-pair chromatography and application to geological samples.

A method for the pre-treatment of acid samples prior to ion chromatography is described. In a strong acid medium, Cr(VI) oxidizes diphenylcarbazide, the resulting products forming a stable complex which can be transferred in a methanolic medium by solid-phase extraction using polyethylene as sorbent. This methanolic sample solution can be injected directly into a chromatographic system with a silica-based column. The separation and determination of the chromium complex can be performed by HPLC-using a mobile phase of 15% (v/v) acetonitrile containing 1 mmol/L tetrabutyl ammonium hydroxide (TBAH). The detection limit is estimated to be 2 microg/L chromate and the linear range is at least 0.05-2 mg/L chromate.

Speciation of Cr(III) and Cr(VI) and separation of common anions by ion pair chromatography with trans-1,2-diaminecyclohexane-N,N,N',N'-tetraacetic acid.

A reversed phase ion pair chromatographic method for the simultaneous determination of Cr species and common anions on a C(18)-bonded stationary phase was developed by using acetonitrile-water (2:98 v/v) containing 1.0 mM tetrabutylammonium hydroxide and 0.5 mM trans-1,2-diaminecyclohexane-N,N,N',N'-tetraacetic acid (DCTA) at pH 6.5 as mobile phase and UV-detection at 210 nm. Chromatographic parameters were optimized for separation of Cr(III)-DCTA complex, chromate and other anions. The detection limits were found as 8 ng/ml for Cr(III) and 35 ng/ml for Cr(VI). Under the optimum conditions, most other ions did not interfere. The method can be applied to separate a number of common anions simultaneously with the separation of Cr(III) and Cr(VI).

Immobilized enzymes as tools in food analysis.

A lot of publications described the possibilities of using selective enzymatic reactions in analysis, but not much authors described applications for the analysis of real samples. In this paper important publications, which described different applications in food analysis, are reviewed. In the first section the use of biosensors for food analysis, in the second section the combination of immobilized enzymes and flow injection analysis and in the last section the use of immobilized enzymes in combination with HPLC are described. Most of the applications described used enzymes for the determination of sugars mainly glucose, but also methods for the determination of inhibitors in foods are described.

[Analysis of element species and the question of the bioavailability of calcium from different types of bread]. / Beitrag der Elementspeziesanalytik zur Frage der Bioverfügbarkeit von Calcium aus unterschiedlichen Brotsorten.

In NaCl and NaCl/HCl extracts from 11 kinds of bread and flour the calcium ion concentrations in comparison to the total calcium contents were determined by a calcium-selective electrode. Crisp-breads showed the slowest values of extractable calcium and calcium ion concentrations in the extracts. Differentiated investigations on calcium binding in the neutralized extracts were carried out with a view to studying calcium resorption in the duodenum. Correlations with the phytic acid contents have shown that other degradation products also take part in the re-binding of calcium. By these investigations the contribution of element speciation to the evaluation of calcium bioavailability has been shown by the analytical methodology and the results of application.

[Determination of aluminum traces in dialysis concentrates]. / Aluminium-Spurenanalyse in Dialysekonzentraten.

To determine traces of aluminium in dialyse concentrates trouble free and accurate by atomic absorption spectrometry a special procedure of enrichment was developed. The aluminium chromazurol S complex is adsorbed selectively at polyethylene powder whereby the disturbanced matrix (KCl) is separated. After elution by a 0.3% ethanolic solution of nitric acid the determination of aluminium is carried out by the graphite oven (flameless) atomic absorption spectrometry. All used materials have to be cleaned carefully. The determination limit for aluminium is 5 micrograms/l dialyse concentrate (the IUPAC commended limit is 15 micrograms/l).

[Ion chromatographic analysis of cations and anions in mineral water]. / Ionen-chromatographische Analyse von Kationen und Anionen in Mineralwässern.

For the simultaneous analysis of the cations Li, Na, K, Ca, and Mg as well as Mn and the anions hydrogen carbonate, chloride, sulfate and nitrate, silica gel- and polymer-based ion exchange materials with conductivity and spectrophotometric detection combined with a post-column derivatization system (PAR-Zn-EDTA for Ca, Mg, Mn) and also an ion-pair system with RP-18 phase were compared with a view to their application to mineral water samples. It is possible to determine Li, Na, and K in such samples with or without the suppressor technique using polymer columns. A polybutadiene maleic acid silica gel cation exchanger material makes feasible simultaneous analysis of alkaline and earth alkaline metals. Ca, Mg, and hydrogen carbonate, chloride, sulfate and nitrate are analyzed in less than 16 min using a silica gel anion exchanger with EDTA as the eluent. To stay within the linear range of the calibration function it is necessary to perform two injections in different dilutions (between 1:4 and 1:500) due to the different concentration ratios. For the analysis of manganese above 100 micrograms/L a system with the cation exchanger Partisil SCX and the eluent ethylenediamine/oxalate with post-column derivatization is used. The sample pretreatment is done by reduction with thiosulfate. A total of 15 different mineral waters were analyzed with all the systems and the results were compared with those of reference methods (AAS, potentiometry), showing good conformity.

[Food chemistry and technology aspects of nickel-deficient nutrition in endogenously-induced allergic contact eczemas]. / Lebensmittelchemische und -technologische Aspekte zur nickelarmen Ernährung bei endogen bedingten allergischen Kontaktekzemen.

With reference to endogenous nickel contact dermatitis, the quantity of nickel resorbed is dependent on the individual capacity for absorption, the element species of nickel in the food matrix and the total nickel content in the food. As the content of nickel varies widely in individual foods, it is difficult to make any definite dietary recommendations. The wide fluctuation in the nickel content of vegetable food stuffs is due to variations in the composition of soil. This means the availability of nickel to plants is not constant. The fluctuating content of nickel in the soil also has a heavy influence. Nickel contamination can be considerable when food is prepared in the usual way. The danger of nickel contamination during industrial preparation of food has not yet been fully explored. In tests for endogenous nickel contact eczema, organic nickel should be used. Another way is to administer a diet containing only defined minute amounts of nickel.

[A new HPLC procedure for cyclamate in food with pre-chromatographic derivatization]. / Neues HPLC-Verfahren für Cyclamat in Lebensmitteln mit prä-chromatographischer Derivatisierung.

A high-pressure liquid chromatography (HPLC) procedure for the detection of cyclamate in liquid and solid samples is presented, which depends on oxidation and the reaction of cyclohexylamine with o-phthaldialdehyde to form a condensation product. The results of the HPLC analysis, using an RP-C 18 separation system with UV detection at 242 nm are reported. Contents, from 2 to 400 mg/l, can be detected in less than 2 h (HPLC analysis within 20 min) with relative standard deviations of 4%. Only for cucumber infusions were incomplete recoveries of 68% obtained.

Kinetic studies on nitrite and nitrate in rats by ion-pair chromatography.

A highly sensitive and specific ion-pair chromatographic method is presented for the simultaneous determination of nitrite (NO2-) and nitrate (NO3-) in plasma. The detection limits are 2 mumol NO2-/l and 8 mumol NO3-/l with recovery rates of 98-99%. The applicability of this method to clinical medicine is demonstrated using NO2- -loaded rats as a biological model: following intravenous infusion or intragastric application of NO2-, blood levels of NO2-, NO3- and methemoglobin are measured during 2-64 min. The kinetic data obtained reflect the complex metabolism of NO2- and NO3- in living organisms.

[Differential analysis of the binding forms of iron in various plant foodstuffs]. / Differenzierte Analytik zu den Bindungsformen des Eisens in verschiedenen pflanzlichen Lebensmitteln.

In fourteen plant foodstuffs of various composition a differentiation of iron contents according to water soluble, in ethylacetate extractable, in labile contents and iron(II) or Fe(III) species in the water extract are carried out by the spectrophotometric Ferrozine method. High water-soluble labile iron parts and high iron(II) contents were found in fruit, high complexed parts in the water extract and ethylacetate extractable iron contents in protein rich foodstuffs. The iron total contents are situated between 1 and 90 ppm, the water soluble parts amount to 6 up to 60% of the total content according to the foodstuffs.