Extraction with Simultaneous Degradation

Sample preparation of human milk depends strongly on the vitamins in qnes-tion and limits the number of different vitamins that can be analyzed simultaneously [87-89]. Sample preparation was carried out under subdued light and on ice to protect the analytes from degradation. Targeted vitamins were extracted by water and methanol after several dilution, centrifugation, dryness, and filtration steps. The nonpolar constituents of the matrix were then extracted with diethyl ether [90]. 

In order to study simultaneously the behaviour of parent priority surfactants and their degradation products, it is essential to have accurate and sensitive analytical methods that enable the determination of the low concentrations generally occurring in the aquatic environment. As a result of an exhaustive review of the analytical methods used for the quantification within the framework of the three-year research project Priority surfactants and their toxic metabolites in wastewater effluents An integrated study (PRISTINE), it is concluded that the most appropriate procedure for this purpose is high-performance (HP) LC in reversed phase (RP), associated with preliminary techniques of concentration and purification by solid phase extraction (SPE). However, the complex mixtures of metabolites and a lack of reference standards currently limit the applicability of HPLC with UV- or fluorescence (FL-) detection methods. 

The approach of Casiot et al. [21] was soon accepted and followed in the held of Se speciation. Wrobel et al. [91] applied a bacterium (Arthrobacter luteus) derived lysing enzyme mixture added with PMSF to study the intermediary molecules of Se metabolism of Se-enriched yeast without proteolysis. In order to tailor the cell wall degrading mechanism to the samples under test, Michalke et al. [77] used bacterial lisozyme and pronase E, either alone or in combination, for the Se speciation of Se-enriched lactic acid bacteria. Independent and simultaneous experiments were carried out with the two enzymes, thus achieving outstanding total Se-extraction efficiency (85-105 percent) with the sole application of pronase E and relatively low chromatographic recovery (8-12 percent) (still... 

A rapid, automated procedure for single-step and simultaneous extraction of cocaine and 11 related compounds was developed by Lewis et al. [95]. Fluid and tissue specimens were extracted using an automated SPE system (Zymark Rapid-Trace) with a Bond Elute-Certify I cartridge. Samples were derivatized with pentafluoro-propionic anhydride/2,2,3,3,3-pentafluoro-l-propanol prior to GC-MS analysis. The method allowed differentiation between smoking crack and intranasal/intravenous cocaine use and was able to elucidate whether ethanol and cocaine were used simultaneously. Another way to determine cocaine in biological matrices is to measure its metabolites and/or degradation products. MEG is produced when... 

Edlund described a method for simultaneous determination of morphine, 6-0-acetyl morphine and codeine in human plasma or blood. The samples were buffered to pH 9 and extracted on silica columns, cleaned by extraction and finally acylated with pentafluoropropionic anhydride. The derivatives formed were separated on a glass capillary column (25 m by 0.36 mm I.D., coated with OV-1) at 220°C. The falling needle injection and electron capture detection were used. Although degradation of the solutes was observed, the degradation observed was very reproducible, so that quantitative analyses could be carried out in spite of the degradation. The author recommended regular control and calibration in order to obtain reliable results. 

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