CONTENTS & ABSTRACTS

In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Chemistry

Volume 53 No. 2 June 2004

Capillary electrophoretic monitoring of microbial growth: determination of organic acids; 51–64

Marina Kudrjashova, Heli Tahkoniemi, Kati Helmja, and Mihkel Kaljurand

Abstract. Capillary electrophoresis (CE) with indirect UV detection was used for determination of organic acids produced by microorganisms in a liquid medium. The microbial culture broth has a complex composition including organic metabolites and a large amount of mineral salts. Analysis of such samples is troublesome. However, in the benzoate background electrolyte with addition of cetyltrimethylammonium bromide (CTAB), organic acids were successfully separated without a significant peak distortion due to the matrix effect. This electrolyte system was applied for a study of solubilization of mineral phosphates by rhizosphere fungi. It was demonstrated also that a background electrolyte containing pyridine-2,6-dicarboxylic acid as a complexing reagent and CTAB allows simultaneous determination of organic acids and metal cations in one electrophoretic run. This electrolyte composition provides a basis for more sophisticated application of CE: monitoring the consumption of heavy metals by bacterial culture.

Speciation of chromium using wide-bore capillary electrophoresis with electrothermal atomic absorption spectrometry detection; 65–74

Ruth Kuldvee, Aleksei Zaidentsal, Anu Viitak, Maili Treumann, and Mihkel Kaljurand

Abstract. The development of a new method for chromium speciation using capillary electrophoresis–electrothermal atomic absorption spectrometry (CE–ETAAS) is described. For that purpose a simple capillary electrophoresis device enabling simultaneous separation and concentration of different chromium species has been designed and constructed. The device proved suitable for separating Cr(III) and Cr(VI) in aqueous samples. The sample amounts were sufficient for off-line collection and subsequent off-line detection with ETAAS. The influence of sample and background electrolyte pH values on the analytes’ separation and recovery was investigated. The separation time and sample zone length were optimized. The limit of detection for both analytes was 1 ng/mL. RSD of the experiments was about 10%.

Natural and synthetic apatites as sorbents for Cd²⁺ and Cr³⁺ ions from aqueous solutions; 75–90

Merike Peld, Kaia Tõnsuaadu, and Villem Bender

Abstract. The sorption of Cd²⁺ and Cr³⁺ ions from aqueous solutions was investigated on different natural and synthetic apatites. The sorption of Cd²⁺ depends mainly on the apatite specific surface area, it increases with an increase in magnesium and a decrease in carbonate content, reaching 20 and 74 mmol per 100 g of natural and synthetic apatite, respectively. The sorption of Cr³⁺ ions reaches 250 mmol/100 g and depends substantially on the apatite magnesium content, the effect of the specific surface area is less important. The sorption of cadmium proceeds mainly by an ion-exchange mechanism, in the case of chromium also a dissolution–precipitation mechanism is involved.