Vlastimil Kuban

Current trends in isolation, separation, determination and identification of isoflavones: A review

Isoflavones are natural substances which elicit a number of physiological effects in living organisms. The substances are synthesized in plant tissues as protective agents against biotic stress (i. e. bacterial infection). Isoflavones are also an important dietary constituent in human nutrition. Modern trends in studies of isoflavones in plant materials and foodstuffs and procedures for chemical analyses of isoflavones in human body fluids and plant tissues are discussed in this review. Highly effective extraction and purification techniques, i. e. solid-phase extraction, accelerated-solvent extraction, and Soxhlet extraction, are presented. Latest procedures in chromatographic separation of isoflavones that apply different types of sorbents are described. Immunochemical analysis, electrochemical sensing of isoflavones, and spectrometric and other analytical techniques and their applications are also mentioned. Special attention is paid to the highly selective and sensitive technique of mass spectrometry and its application for identification of isoflavones and their glucosides in plants. Studies of interactions of isoflavones with cell receptors and a number of biologically active substances such as DNA and proteins are described. The review does not intend to give a complete overview of the topics considered but rather to present modern and most recent methods used in studies of isoflavones.

Liquid chromatographic/electrospray mass spectrometric determination (LC/ESI-MS) of chelerythrine and dihydrochelerythrine in near-critical CO2 extracts from real and spiked plasma samples

Two polar benzo[c]phenanthridine alkaloids, chelerythrine (CHE) and dihydrochelerythrine (DHCHE), were extracted at 35 degrees C and 10MPa (15MPa for real samples) from real and spiked plasma samples with acceptable recoveries (95.1% and 81.0%, respectively) using near-critical CO(2) modified with aqueous (1:1, v/v) methanol. The alkaloids were quantified by a liquid chromatographic/electrospray mass spectrometric (LC/ESI-MS) method on a Zorbax SB-CN column (75mmx4.6mm, 3.5mum particle size) using methanol (organic phase) and 50mM ammonium formiate (aqueous phase) as a mobile phase. A linear gradient 0-1min, isocratic at 60% organic phase (v/v); from 1.0 to 7.0min, 60-71% organic phase (v/v); from 7.0 to 18.0min, 71-60% organic phase (v/v) was applied. The limit of detection was 1.22ng (3.50pmol) for CHE and 0.95ng (2.72pmol) for DHCHE per 1ml of the sample. The linearity of the calibration curves was satisfactory as indicated by coefficients of determination 0.9979 and 0.9995 for CHE and DHCHE, respectively. Repeatability and intermediate precision (average R.S.D.s) were 1.0-1.5%, accuracy was in the range 99.7-100.3%. Average recovery was 100.1% for both, standard solutions and spiked plasma extracts. Three samples of real rat plasma were extracted and analysed to test the method.

Determination of thallium in aqua regia soil extracts by ICP-MS.

In our study the method for the determination of Tl by ICP-MS was optimized. Both isotopes, 203 Tl and 205 Tl, were used for the measurement. Lutetium at a concentration 0.4 mg L -1 was used as an internal standard. Soil extracts were measured after dilution (1+4 with the solution of lutetium 0.5 mg L -1 ). Several soils from the International Soil Exchange Programme (WEPAL) were analyzed for the comparison of the results. For all tested samples the achieved results were in a good agreement with the results reported by WEPAL. A detection limit 1.2 μg kg -1 was achieved for the samples. The method was used for the determination of thallium in soils collected in the national monitoring programme (200 sites) and in the monitoring programme of the contaminated areas (27 sites). Topsoil and subsoil were sampled on each site and analyzed separately (454 samples were analyzed). The median value for the tested soils was 0.25 mg/kg, lower and upper quartiles 0.19 and 0.32 mg kg -1 respectively, 10 th and 90 th percentiles 0.16 and 0.41 mg kg respectively and the maximum value was 2.83 mg kg -1 .Abstract In our study the method for the determination of Tl by ICP‐MS was optimized. Both isotopes, 203Tl and 205Tl, were used for the measurement. Lutetium at a concentration 0.4 mg L‐1 was used as an internal standard. Soil extracts were measured after dilution (1+4 with the solution of lutetium 0.5 mg L‐1). Several soils from the International Soil Exchange Programme (WEPAL) were analyzed for the comparison of the results. For all tested samples the achieved results were in a good agreement with the results reported by WEPAL. A detection limit 1.2 μg kg‐1 was achieved for the samples. The method was used for the determination of thallium in soils collected in the national monitoring programme (200 sites) and in the monitoring programme of the contaminated areas (27 sites). Topsoil and subsoil were sampled on each site and analyzed separately (454 samples were analyzed). The median value for the tested soils was 0.25 mg/kg, lower and upper quartiles 0.19 and 0.32 mg kg‐1 respectively, 10th and 90th percentiles 0.16 and 0.41 mg kg‐1 respectively and the maximum value was 2.83 mg kg‐1.

Analytical methods and quality assurance

In our study the method for the determination of Tl by ICP-MS was optimized. Both isotopes, 203 Tl and 205 Tl, were used for the measurement. Lutetium at a concentration 0.4 mg L -1 was used as an internal standard. Soil extracts were measured after dilution (1+4 with the solution of lutetium 0.5 mg L -1 ). Several soils from the International Soil Exchange Programme (WEPAL) were analyzed for the comparison of the results. For all tested samples the achieved results were in a good agreement with the results reported by WEPAL. A detection limit 1.2 μg kg -1 was achieved for the samples. The method was used for the determination of thallium in soils collected in the national monitoring programme (200 sites) and in the monitoring programme of the contaminated areas (27 sites). Topsoil and subsoil were sampled on each site and analyzed separately (454 samples were analyzed). The median value for the tested soils was 0.25 mg/kg, lower and upper quartiles 0.19 and 0.32 mg kg -1 respectively, 10 th and 90 th percentiles 0.16 and 0.41 mg kg respectively and the maximum value was 2.83 mg kg -1 .Abstract In our study the method for the determination of Tl by ICP‐MS was optimized. Both isotopes, 203Tl and 205Tl, were used for the measurement. Lutetium at a concentration 0.4 mg L‐1 was used as an internal standard. Soil extracts were measured after dilution (1+4 with the solution of lutetium 0.5 mg L‐1). Several soils from the International Soil Exchange Programme (WEPAL) were analyzed for the comparison of the results. For all tested samples the achieved results were in a good agreement with the results reported by WEPAL. A detection limit 1.2 μg kg‐1 was achieved for the samples. The method was used for the determination of thallium in soils collected in the national monitoring programme (200 sites) and in the monitoring programme of the contaminated areas (27 sites). Topsoil and subsoil were sampled on each site and analyzed separately (454 samples were analyzed). The median value for the tested soils was 0.25 mg/kg, lower and upper quartiles 0.19 and 0.32 mg kg‐1 respectively, 10th and 90th percentiles 0.16 and 0.41 mg kg‐1 respectively and the maximum value was 2.83 mg kg‐1.