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Hollow fibre-liquid phase microextraction of basic drugs from dried dried blood spots
Dvořák, Miloš ; Miková, B. ; Šlampová, Andrea ; Kubáň, Pavel
Hollow fibre-liquid phase microextraction (HF-LPME) was applied for rapid and efficient extraction of basic drugs from dried blood spots (DBS). Basic drugs from DBS were first extracted into 10 mM NaOH solution, which acted as the HF-LPME donor solution, and simultaneously the neutralized drugs were transferred across the HF and preconcentrated in 10 mM HCl acceptor solution inside the HF lumen. Mixture (1:1, v:v) of 1-ethyl-2-nitrobenzene and dihexyl ether was used for impregnation of the porous HF membrane. Analytes in the acceptor solution were injected directly from the HF into capillary electrophoresis instrument for further separation, detection and quantification. Repeatability of the hyphenated analytical system ranged from 9.8 to 13.8 % (RSD) and enrichment factors of 52 – 78 were obtained for model basic drugs spiked to DBS extracts at a concentration level of 0.1 mg/L.
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Capillary electrophoresis with contactless conductivity detection for rapid determination of meldonium in urine
Šlampová, Andrea ; Kubáň, Pavel
A simple, rapid and cheap capillary electrophoresis-capacitively coupled contactless\nconductivity detection (CE-C4D) method for determination of meldonium (MEL) in\nurine samples was developed. Sample pretreatment was minimized to dilution of urine\nsamples with DI water and MEL was determined by CE-C4D in background electrolyte\nconsisting of 2 M acetic acid (pH 2.3) in ng mL−1 to mg mL−1 concentration range.\nSample-to-sample analysis time was less than 4 min, limit of detection and\nquantification was 0.015 and 0.05 μg mL−1, respectively, and the method showed\nexcellent linearity (r2 ≥ 0.9998), recovery (97.6–99.9%) and intraday as well as interday\nrepeatability (RSD ≤ 4.7%).
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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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