Electro membrane extraction combined with capillary electrophoresis for the determination of amlodipine enantiomers in biological samples

Abstract

Electro membrane extraction as a new microextraction method was applied for the extraction of amlodipine (AM) enantiomers from biological samples. During the extraction time of 15 min, AM enantiomers migrated from a 3 mL sample solution, through a supported liquid membrane into a 20 μL acceptor solution presented inside the lumen of the hollow fiber. The driving force of the extraction was 200 V potential, with the negative electrode in the acceptor solution and the positive electrode in the sample solution. 2-Nitro phenyl octylether was used as the supported liquid membrane. Using 10 mM HCl as background electrolyte in the sample and acceptor solution, enrichment up to 124 times was achieved. Then, the extract was analyzed using CD modified CE method for separation of AM enantiomers. Best results were achieved using a phosphate running buffer (100 mM, pH 2.0) containing 5 mM hydroxypropyl-α-CD. The range of quantitation for both enantiomers was 10-500 ng/mL. Intra- and interday RSD (n=6) were less than 14%. The limits of quantitation and detection for both enantiomers were 10 and 3 ng/mL respectively. Finally, this procedure was applied to determine the concentration of AM enantiomers in plasma and urine samples.

Electromembrane Extraction from Biological Fluids

“…This has been verified experimentally in several EME papers, 10,20,[23][24][25]27,29,[31][32][33][34] where recoveries have been found to increase with increasing voltage up to a certain level. The latter point out that extraction is limited by other factors than the voltage at high voltages, and deviations from Eq.…”

“…Several other publications have also addressed EME of different basic drugs, including amlodipine enantiomers, 20 mebendazole, 21 amphetamine, 22 methamphetamine, 22 3,4-methylenedioxymethamphetamine, 22 3,4-methylenedioxyethamphetamine, 22 methylbenzodioxolybutanamine, 22 levamisole, 23 lithium, 24 naltrexone, 19 and nalmefene. 19 In these applications either NPOE, 20,21 1-octanol, 24 NPOE mixed with DEHP, 19 or NPOE mixed with tris-(2-ethylhexyl) phosphate (TEHP) 22,23 were used as SLM, and extractions were accomplished with voltages in the range 75 -250 V from acidic sample to acidic acceptor solution.…”

“…EME therefore provides very fast extractions as compared to HF-LPME. 20,34 The principal reason for this is that analytes are transferred by electro-kinetic migration across the SLM in EME as compared to passive diffusion in HF-LPME. The consumption of organic solvent is low, and typically only 10 to 20 μl of solvent is used per Fig.…”

“…18 Several of the developed EME methods have been validated, and have provided acceptable results from human plasma, whole blood, urine, saliva, and breast milk. 10,[17][18][19][20][21][22][23][24][25]28,31,32 Typically, the EME methods have provided linear calibration curves over 2 decades (r 2 > 0.99) 22,24 and with repeatability values in the range 2 -10% RSD. 22,24 One example of validation results are reported in Table 1 for naltrexone and nalmefene in human plasma and urine.…”

Use of voltammetry for in vitro equilibrium and transport studies of ionisable drugs

“…Gradually, the group improved the method by decreasing the voltage to values as low as 1 V DC [50] and developing an on-chip device for online UV-vis and HPLC detection of electrically extracted drugs [51]. While this method is suitable for quantitative extraction of molecules across the membrane and promising for quick analysis of complex samples, such as urine or blood [52][53][54], the relatively high applied voltage and absence of supporting electrolyte in the membrane present a problem for theoretical explanation of the ionised drug transfer. The fundamental understanding of electrochemically induced transfer across SLMs stems from electrochemistry at ITIES, as discussed in previous sections, and the connection between the two inspired researchers to extend the know-how to systems with two liquid|liquid interfaces, where a small voltage (usually below 500 mV DC) is applied.…”