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Polymer inclusion membranes open new way in practical use of in-line coupling of microextraction to CZE
Pantůčková, Pavla ; Kubáň, Pavel ; Boček, Petr
Polymer inclusion membranes (PIMs) have several important features, i.e., PIMs are dry and non-porous membranes, which can be prepared ahead of use and stored without noticeable deterioration in extraction performance. In-line coupling of microextractions across PIMs to commercial capillary zone electrophoresis (CZE) instrument has been demonstrated in this contribution. Purpose-made microextraction devices with PIMs were applied, which ensured complete automation of the entire analytical procedure. Practical 169 applicability of the hyphenated analytical method was demonstrated on direct extraction, injection, CZE separation and quantification of formate (the major metabolite in methanol poisoning) in clinical samples.
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Considerations on electrolysis in electromembrane extraction of basic drugs
Šlampová, Andrea ; Kubáň, Pavel ; Boček, Petr
Electrolysis may significantly affect composition and pH values of non-optimized acceptor solutions and have fatal consequences on quantitative EME results for weak and medium strong analytes. Acceptor solutions consisting of high concentrations of weak acids have therefore been proposed as suitable operational solutions for electromembrane extraction (EME) of selected basic drugs. 500 mM formic acid efficiently eliminated the electrolytically produced OH– ions, offered constant pH and thus long-term EME performance and was easily compatible with subsequent analytical methods. Maximum EME recoveries ranged from 66 to 89% and were constant between 40 and 80 min of EME and no back-extraction of the analytes into donor solutions was observed.
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Electrolysis in electromembrane extractions. Effects on extraction performance for substituted phenols
Šlampová, Andrea ; Kubáň, Pavel ; Boček, Petr
Electrolysis was shown to play a significant role in electromembrane extraction (EME) performance. Alkaline acceptors, prepared as 1 – 10 mM CsOH solutions, suffered from electrolytic reactions during EMEs of substituted phenols and their pH values decreased by more than 8 units after 40 min of EMEs at 50 V. As a consequence, serious deterioration of EME performance was observed for weak and medium-strong acidic phenols due to their compromised ionization and their subsequent back-extraction into organic phase and donor solution. Application of acceptor solutions consisting of high concentrations of weak bases (e.g. 500 mM ethanolamine) ensured similar initial pH conditions as for the alkali-metal hydroxide based solutions, moreover, significantly better tolerance to electrolysis-induced effects was obtained. Stable pH of acceptor solutions was achieved as well as an improved EME performance for all analytes over the entire extraction period.
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