Capillary electrochromatography with a neutral monolithic column for classification of analytes and determination of basic drugs in human serum

Abstract

Capillary electrochromatography (CEC) using a neutral hydrophobic polymer-based monolithic column has been developed for classification of analytes based on their acidity and charges of group. The monolithic columns were prepared by in situ copolymerization of lauryl methacrylate and ethylene dimethacrylate without any charged monomers in the reaction mixture. The ionic analytes will only be driven by their electrophoretic mobilities and were separated on the basis of their differences in electrophoretic mobility and in hydrophobic interaction with the stationary phase. Only negatively or positively charged analyte (acid or basic) migrated toward detection window in a single run by applying negative or positive voltage. The CEC system was also applied for the analysis of basic drugs in human serum by internal standard method using acidic running buffer. The sample of human serum spiked with basic drugs was directly injected after a simple sample pretreatment. The calibration curves with regression coefficients (0.9995-0.9997) in the range of 0.318-80 microg/mL were obtained with the limits of detection being below 0.15 microg/mL. The intra- and inter-day precisions, determined as relative standard deviations, were less than 4.21%.

Ecstasy Analysis by Monolithic Materials-Capillary Electrochromatography

“…43 Therefore, only positively charged and neutral monolithswerefurtherinvestigated.Thesealsoareconsidered aspartoftheoptimizationstepsforthesemonolithsinproviding shortmigrationtimesandgoodseparationefficiency.…”

“…[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] These materials usually require ionizable functional groups in order to generate the electroosmoticflow(EOF)drivesthemobilephaseandanalytes through the capillary column. 43 However these ionized functional groups can sometimes cause poor efficiencies and asymmetric peaks because of the interactions between the charged surface of the stationary phase and ionic samples. [43][44][45] Therefore, in some case the uncharged (neutral) monolith columnwaspreferred.…”

“…43 However these ionized functional groups can sometimes cause poor efficiencies and asymmetric peaks because of the interactions between the charged surface of the stationary phase and ionic samples. [43][44][45] Therefore, in some case the uncharged (neutral) monolith columnwaspreferred.…”

“…[43][44][45] Inviewofthis,positivelychargedmonolithsshouldhavebetter, howevertherepulsionbetweenthechargedanalytesandcharged stationaryphasemayaffecttheseparationefficiency. 46,47 Using neutralmonoliths,thehydrophobicinteractionbetweencharged analytes and neutral stationary phase may also be lost and influence the separation efficiency.…”

“…46,47 Using neutralmonoliths,thehydrophobicinteractionbetweencharged analytes and neutral stationary phase may also be lost and influence the separation efficiency. 43,48 Therefore, the performanceofbothcharged(negativeandpositive)andneutral monolithcolumnswereinvestigatedfortheanalysisofMDMA and its metabolite, MDA (since MDA usually reported both in ecstasytabletsfromsomeregionsandinbiologicalsample),by capillary electrochromatography. The one monolith that provided the highest efficiency with shortest analysis time was then selected for validation and the analysis of ecstasy tablets (MDMA)anditsmetabolitesinurinesamples.…”