Vera Pacakova

Reliability of Carotenoid Analyses: A Review

This review critically discusses the most important properties of techniques applied to analyses for carotenoids and their impact on the reliability of the analytical results. The emphasis is placed on modern methods and the most recent references. Examples of analytical procedures illustrate the characteristics of experimental approaches to carotenoid analyses but no systematic survey of applications is given. Carotenoids are characterized chemically and their occurrence and functions in organisms are outlined. The principal implications of the (bio)chemical properties of carotenoids for the selection of an appropriate analytical procedure and for optimisation of the experimental conditions are dealt with. Various aspects of pre- treatment and preconcentration of analytical samples are discussed, emphasizing modern approaches, such as microwave-assisted extraction or supercritical fluid extraction; the problems connected with chromatographic purification of carotenoids and with the obtaining of reliable standard materials are also dealt with. The approaches to determination of carotenoids involving high-performance separations are evaluated, emphasizing the importance of high performance liquid chromatography (HPLC) and capillary electrochromatography (CEC); of the detection techniques, spectrophotometry in ultraviolet and visible region (UV/VIS spectrophotometry), electrochemistry, thermal lens spectrometry (TLC), mass spectrometry (MS), nuclear magnetic resonance (NMR), and some aspects of vibrational spectrometry are primarily discussed.

Analysis for estrogens as environmental pollutants – A review

The approaches to the analysis for estrogen compounds as environmental pollutants are critically reviewed and evaluated on the basis of significant, recent original publications. The importance of sample pretreatment and analyte preconcentration techniques is pointed out, with an emphasis on SPE and on the use of highly selective interactions such as molecular recognition. The hyphenated systems of high-performance gas or liquid chromatography and mass spectrometric techniques are discussed as the basic methods of determination of estrogens in environmental samples. Immunochemical procedures are shown to be useful in semiquantitative screening of estrogen pollutants (e.g. ELISA kits). Classical HPLC and GC with common UV/Vis, fluorescence and electrochemical detection are useful in routine checking on higher pollutant concentrations.

Optimization of a GC‐MS/MS Method for the Analysis of PCDDs and PCDFs in Human and Fish Tissue

This paper outlines the possibilities of selectivity and sensitivity enhancement in measuring PCDD/F congeners using an ion trap GC-MS/MS. The pressure of the collision gas and the collision energy were optimized. The modified GC-MS/MS method was applied to the determination of PCDDs and PCDFs in human and fish tissues. Limits of quantification were about 1 pg/g of fat for all seventeen 2378 PCDD/Fs tested (starting amount of fat, 2 g).

Electrochemical detector for high-performance liquid chromatography

Abstract A voltammetric detector has been developed for high-performance liquid chromatography, based on a three-electrode system with a platinum tubular working electrode. The detector has a small volume (about 1 μl) and has been used in the d.c. and differential pulse polarographic (DPP) modes. Its function was tested using various organic compounds, e.g. , phenol, ascorbic acid and uric acid. The detection limit is about 0.5 ng, the linear dynamic range is at least five orders of magnitude of concentration and the measurements exhibit good reproducibility. The d.c. and DPP methods of detection were about equally sensitive and the reproducibilities of the peak areas were similar, but the d.c. peak height exhibited better reproducibility than that of the DPP peaks. The detector was used in the separation of the catecholamines adrenaline, noradrenaline, dopamine and l -dopa in a reversed-phase system. It was found that nanogram amounts can be detected, with narrow and symmetrical peaks.

An ion-exchange separation of metal cations on a C-18 column coated with dodecylsulphate.

The retention mechanism was studied for the cations of the alkaline earth metals and Zn(2+) Ni(2+), Co(2+), Cd(2+) and Bi(3+) on a C(18) column permanently coated with sodium dodecylsulphate, with aqueous mobile phases containing cupric chloride or sulphate, or cerous nitrate. The dependencies of the logarithm or the capacity ratio on the logarithm of the eluent concentration were linear, demonstrating that ion-exchange was the predominating separation mode; the slopes of these dependencies were in good agreement with the values predicted from the ion-exchange theory. Indirect UV photometric detection yielded limits of detection (LOD) of 21, 44, 120 and 275 ng in the volume injected, 20 mul, for Mg(2+), Ca(2+), Sr(2+) and Ba(2+), respectively, with the 10(-2)M copper(II) chloride mobile phase; the respective LOD values decreased to 0.8, 1.6, 3.0 and 6.7 ng with the 5 x 10(-4)M cerium(III) nitrate eluent. The method was found to be primarily suitable for determination of the alkaline earths and was applied to analyses of surface and mineral waters.

Analysis of estrogens and estrogen mimics in edible matrices—A review

This review provides a brief survey of the biological effects of selected endocrine-disrupting compounds that are formed after internal exposure of organisms. Further, the present analytical methods available for the determination of these compounds in foodstuffs are critically evaluated. The attention is primarily devoted to the methods for sample pretreatment, which are the main source of errors and are usually the most time-consuming step of the whole analysis. This review is focused on selected natural and synthetic estrogens, estrogen conjugates, and chemical additives used in the plastic industry that can act as estrogen mimics.

Critical evaluation of microextraction pretreatment techniques - Part 1: Single drop and sorbent-based techniques

Sample pretreatment techniques or preconcentration constitute a very important step before the analysis of environmental, clinical, pharmaceutical, and other complex samples. Thanks to extraction techniques it is possible to achieve higher method sensitivities and selectivities. Miniaturization microextraction methods make them more environmentally friendly and only small amounts of samples are required. In the past 30 years, a number of microextraction methods have been developed and used and are documented in thousands of articles. Many reviews have been written focusing on their use in specified professional fields or on the latest trends. Unfortunately, no uniform nomenclature has been introduced for these methods. Therefore, this review attempts to classify all the essential microextraction techniques and describes their advantages, disadvantages, and the latest innovations. The methods are divided into two main groups: single drop and sorbent-based techniques according to the type of extraction phase.