[Determination of valproic acid by on-line coupled capillary isotachophoresis with capillary zone electrophoresis with conductometric detection]. / Stanovení kyseliny valproové pomocí on-line spojení izotachoforézy a kapilární zónové elektroforézy s vodivostní detekcí.

The paper aimed to test suitable conditions for the determination of VPA in serum using the ITP-CZE method with conductometric detection. It attempted to find whether for the method described by Olvecká et al. it is possible to use a similar procedure of sample preparation as for the gas chromatographic method which is routinely employed for the assessment of VPA in serum. A 200 rl sample of serum was extracted with 200 rl of acetone and after centrifugation 200 rl of the upper layer was withdrawn and supplemented with demineralized water to make 10 ml. When a microsyringe is used for dosing, consumptions of serum can be reduced up to 5 rl, which is advantageous mainly for therapeutic drug monitoring in children. The length of analysis was 20 minutes. The method was linear within the range of 20-400 mg/l, which includes the therapeutic range of VPA (50-100 mg/l). The detection and quantification limits were 2.5 and 8.5 mg/l, respectively. The variation coefficients were below 10% in all three concentrations (30, 70 and 120 mg/l). The new method was compared with the method of gas chromatography by means of the Passing-Bablok regression analysis and both methods were found to give identical results.

Analysis of the active components of silymarin.

Silymarin is an antihepatotoxic substance isolated from fruits of Silybum marianum. Possibly due to their antioxidant and membrane stabilizing properties, the compounds have been shown to protect different organs and cells against a number of insults. The content and composition of main silymarin components (silybin, isosilybin, silydianin and silychristin) in various pharmaceuticals were analysed using HPLC and newly developed capillary zone electrophoresis method. Antioxidant properties expressed as total antioxidant status (TAS) of silymarin components were studied. Results of TAS were correlated with electropherograms and chromatograms.

New configuration in capillary isotachophoresis-capillary zone electrophoresis coupling.

The paper surveys possible configurations of a coupling capillary column operating in various electromigration modes. Special attention is given to capillary isotachophoresis-capillary zone electrophoresis (cITP-CZE) coupling and its description from the theoretical point of view. Computer simulations of separation are presented and compared with experiments. Further, we propose a new configuration of electrolyte systems in cITP-CZE coupling, which offers a possibility to perform complex analyses of micro- and macro-constituents in one run. The electrolyte system is verified by practical experiments for both anionic and cationic modes of analysis. The advantages and disadvantages of the new combination are discussed.

Determination of fumaric acid in apple juice by on-line coupled capillary isotachophoresis-capillary zone electrophoresis with UV detection.

An on-line coupled capillary isotachophoresis-capillary zone electrophoresis (cITP-CZE) method for the determination of the fumaric acid content in apple juice is presented. A clear separation of fumaric acid in real samples is achieved within 20 min. The leading, terminating and background electrolyte of the employed system consist of 10 mM HCl+beta-alanine+5 mM beta-cyclodextrin+0.05% hydroxypropylmethylcelullose (HPMC), pH 3, 10 mM citric acid and 20 mM citric acid+beta-alanine+5 mM beta-cyclodextrin+0.1% HPMC, pH 3.3, respectively. The linearity, recovery, repeatability and detection limit of the developed method are 25-1000 ng/ml, 1.07%, 95.4+/-3.5 (+/-s)% and 10 ng/ml, respectively. Low laboriousness (no sample pretreatment), sufficient sensitivity and low running cost are the important attributes of the cITP-CZE method which was successfully applied to analyses of real samples of apple juices.

Application of isotachophoresis in food analysis.

This review summarizes possibilities of capillary isotachophoresis for the determination of important analytes in food. The emphasis is on quantitative determinations in real food samples. This article covers papers published from 1980 to 1999.

Isotachophoretic determination of creatinine in meat and meat products.

A capillary isotachophoretic method (CITP) to determine the creatinine concentration in meat and meat products is described. A clear separation of the creatinine from other components of an acidic extract of sample was achieved within 20 min. Method characteristics (linearity, accuracy, precision and detection limit) were determined. The developed method was successfully applied to analyze real samples and to determine creatinine and creatine content (indirect determination after acidic hot extraction) in meat and meat products.

Isotachophoretic determination of 3-methylhistidine.

A capillary isotachophoretic (cITP) method to determine the concentration of 3-methylhistidine (3-MeHis) in meat and meat products is described. A clear separation of the 3-MeHis from histidine, 1-methylhistidine and other components of acidic sample hydrolyzate was achieved within 20 min. Method characteristics (linearity, accuracy, precision and detection limit) were determined. Low laboriousness, sufficient sensitivity and low running cost are the important attributes of cITP method. The developed method was successfully applied to analyses of real samples and used for the determination of lean meat content in meat and meat products.

Application of capillary isotachophoresis and capillary zone electrophoresis to the determination of inorganic ions in food and feed samples.

The purpose of this review is to summarise critically the possibilities of capillary isotachophoresis and capillary zone electrophoresis for the determination of inorganic ions in food and feed samples. This article covers papers published since 1977.

Trace determination of iron in water at the microgram/l level by on-line coupling of capillary isotachophoresis and capillary zone electrophoresis with UV detection of the EDTA-Fe (III) complex.

The determination of iron in water at the trace level by on-line coupled capillary isotachophoresis and capillary zone electrophoresis (CITP-CZE) with a commercial column coupling device is described. Iron is determined as the negatively charged complex with EDTA which is highly UV-absorbing and thus enables photometric detection at 254 nm. The analyses are performed using 10 mmol/l HCl + 20 mmol/l L-histidine + 0.1% hydroxypropylmethyl cellulose (pH 6.0), 5 mmol/l MES, and 25 mmol/l MES + 10 mmol/l bis-tris-propane (pH 6.6) which served as leading, terminating and background electrolyte, respectively. Samples are acidified with HNO3, diluted and EDTA added (to a final concentration of 10(-4) mol/l) prior to CITP-CZE analysis. The detection limit of Fe(III) is 10 micrograms/l, and is given by the chemical noise due to the impurities of the chemicals used enriched by the ITP preconcentration step. The precision of the CE measurement, expressed by the relative standard deviation, is about 3% (at the 400 micrograms/l level); the recovery is between 80 and 115% depending on the iron concentration level (40-400 micrograms/l).

Time course of formation of inositol phosphates during enzymatic hydrolysis of phytic acid (myo-inositol hexaphosphoric acid) by phytase determined by capillary isotachophoresis.

Capillary isotachophoresis with conductivity detection was applied to the investigation of the hydrolytic decomposition of phytic acid (myo-inositol hexaphosphoric acid) by phytase, and for the formation of the reaction products as a function of time. The quantitation of all analytes (besides phytic acid the mono- to penta-phosphorylated inositols and orthophosphate) can be carried out using two different buffer systems.

Determination of 4-methylimidazole in caramel color by capillary isotachophoresis.

A method for the determination or 4-methylimidazole in caramel color, based on cationic separation of the sample by capillary isotachophoresis, is described. No pretreatment of the sample is necessary and the detection limit was found to be 5 ppm.