Determination of illicit drugs in urie samples using carboxylic multi-walled carbon nanotubes as immobilized stationary phase in capillary electrochromatography

PERALTA, CECILIA MARIANA; LANARO, VERONICA M; MARTINEZ, LUIS DANTE; STEGE, PATRICIA W; SOMBRA, LORENA LUJÁN

Rosario

Congreso; 2da Reunión Internacional de Ciencias Farmacéuticas; 2012

Determination of illicit drugs in urine samples using carboxylic multi-walled carbon nanotubes as immobilized stationary phase in capillary electrochromatography   Peralta CM1,3, Lanaro VM3, Martinez LD2,3, Stege PW2,3, Sombra LL2,3   1Área de Química Física, 2Área de Química Analítica, Universidad Nacional de San Luis. Chacabuco y Pedernera. 5700 San Luis. 3Instituto de Química de San Luis (INQUISAL), Argentina.   Introduction The definition of doping is the administration of illegal drugs with the intention of altering the physical performance, in either positive or negative sense [1]. For horse races is a requirement that the horse should not be declared as a participant if in their tissues, body fluids or excretions there is any prohibited substances or its metabolite in higher levels than the normal. The aim of the present study was to demonstrate the facility of OT-CEC (Open tubular capillary electrochromatography) method to separate illicit drugs. The determination of abused drugs (carvedilol, procaine, caffeine, amiloride, ephedrine, clenbuterol and piroxicam) were developed using capillary electrochromatography (CEC) with a stationary phase of carbon nanotubes (c-MWNTs) immobilized into a fused-silica capillary [2].   Materials and methods A Beckman P/ACE MDQ instrument (Beckman Instruments, Fullerton, CA, USA) equipped with a diode array detector and a data handling system comprising an IBM PC and P/ACE System MDQ Software was used. Carboxylated multi-wall carbon nanotubes (c-MWNTs) have been immobilized into a fused-silica capillary to form a stationary phase for CEC. With the purpose of enrichment and sample clean-up we used a simple method as liquid-liquid extraction. A mixture of Chloroporm/Methanol (90:10) was used as the extract phase. Then the extract (organic phase) was evaporated to dryness and the residue was reconstituted with 1 ml of water.   Results We have investigated the electrophoretic features of the c-MWNT immobilized fused-silica capillary by covalent modification of the inner surface of the capillary. The optimization of the experimental conditions has been accomplished by the traditional method of one-at-a-time. The peak areas and migration times were used to evaluate the extraction efficiency, and separation/quantification efficacy under different experimental conditions. The separation obtained with the OT-CEC was compared with the one obtained with CZE under the same electrophoretic conditions. Results indicated good capillary efficiencies and improved electrophoretic separation. The coating of the capillary with MWCTs allowed the separation of the analytes with high resolution, with less band-broadening and without distortion of the baseline. The interactions between the analytes and the MWCTs resulted in an increase of the migration time. Moreover and as expected, we could not achieve a good separation of the analytes with a fused silica capillary. Under the optimum conditions determined in the current work, seven abuse drugs could be separated in less than 25 min. This simple CEC method allowed recognition and quantification of the most common abused drugs in urine racehorse?s samples.   Conclusions The OT-CEC procedure developed here for the simultaneous analysis of seven abused drugs was precise, reproducible, and sensitive. The advantages of this method include simplicity with high selectivity, identification and quantification in the separation of the drugs besides to low cost and efficiency by using MWCTs as a stationary phase. We can conclude that the applicability for monitoring and quantification of abused drugs used in urine samples for this method has been demonstrated. The potential of CEC method was shown performing the analysis of urine samples spiked with the studied compounds after an appropriate extraction procedure. The positive results obtained proved the applicability of CEC technique in toxicology analysis.   References 1- World Anti-doping Agency, www.wada-ama.org. 2-Sombra, L.; Moliner-Martínez,Y.; Cárdenas, S.; Valcárcel, M.; Electrophoresis 2008, 29, 3850?3857. # Corresponding author. Tel +54 2652 425385,  lsombra@unsl.edu.ar