Rapid and simple pretreatment of human body fluids using electromembrane extraction across supported liquid membrane for capillary electrophoretic determination of lithium

Abstract

Electromembrane extraction was used for simultaneous sample cleanup and preconcentration of lithium from untreated human body fluids. The sample of a body fluid was diluted 100 times with 0.5 mM Tris solution and lithium was extracted by electromigration through a supported liquid membrane composed of 1-octanol into 100 mM acetic acid acceptor solution. Matrix compounds, such as proteins, red blood cells, and other high-molecular-weight compounds were efficiently retained on the supported liquid membrane. The liquid membrane was anchored in pores of a short segment of a polypropylene hollow fiber, which represented a low cost, single use, disposable extraction unit and was discarded after each use. Acceptor solutions were analyzed using capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C(4) D) and baseline separation of lithium was achieved in a background electrolyte solution consisting of 18 mM L-histidine and 40 mM acetic acid at pH 4.6. Repeatability of the electromembrane extraction-CE-C(4) D method was evaluated for the determination of lithium in standard solutions and real samples and was better than 0.6 and 8.2% for migration times and peak areas, respectively. The concentration limit of detection of 9 nM was achieved. The developed method was applied to the determination of lithium in urine, blood serum, blood plasma, and whole blood at both endogenous and therapeutic concentration levels.

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.…”

“…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.…”

“…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.…”

“…24 Selecting the organic solvent as SLM in EME is still based on trial and error and more research should be directed to fundamental understanding on how to select the SLM for certain applications.…”