High-performance liquid chromatographic determination of cocaine and benzoylecgonine by direct injection of human blood plasma sample into an alkyl-diol-silica (ADS) precolumn

Abstract

A column-switching high-performance liquid chromatographic method with UV detection for the determination of cocaine (COC) and benzoylecgonine (BZE) in human blood plasma samples is described. The method uses an alkyl-diol-silica ADS-C18 extraction precolumn. A 50- micro L plasma sample was introduced to the ADS precolumn in order to separate the analytes from proteins and endogenous compounds. The fraction containing COC and BZE was back-flushed and transferred to an Alltech mixed-mode C(18)/cation-exchange analytical column for final separation. The validation of the method revealed quantitative recoveries from 95.0 to 99.0% for COC at three different concentrations (0.5, 1.0 and 2.0 micro g mL(-1)), and from 96.0 to 99.0% for BZE at the same concentration levels with coefficients of variation <4.00% (n=5). The detection limit (signal to noise ratio (S/N)>3) was 0.03 micro g mL(-1) for all the compounds with an injection volume of 50 micro L. However, it was possible to enhance the sensitivity further by injecting larger plasma volumes, up to 200 micro L, at the same optimal conditions. The overlap of sample preparation, analysis and reconditioning of the extraction column, increase the overall sample throughput to 5 samples h(-1). The developed method has been applied to human blood plasma samples from subjects suspected of cocaine abuse.

Restricted access materials and large particle supports for on-line sample preparation: an attractive approach for biological fluids analysis

“…An octadecyl analytical column coupled to a pre-column packed with large particles was also found suitable for the simultaneous analysis of methadone and its primary metabolite in plasma [182]. Octyl [26,49], phenyl [55,108], cyano [97,152], mixed-mode [69] and carbonaceous [94] analytical columns coupled to different extraction pre-columns were also suitable for the analysis of several compounds in biological matrices. Recently, Zeng et al [184] developed a column-switching method using an Oasis HLB coupled to a monolithic column for the analysis of a drug cocktail in plasma.…”

“…The ADS column can tolerate up to 80-100 ml of plasma [50,53,54]. The LiChrospher ADS-RP was able to achieve the direct analysis of pharmaceutical compounds in several biological matrices such as plasma [49,50,53,[55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73], serum [42,43,[74][75][76][77][78][79], urine [60,75,76,78,80], microdialysate [81,82], saliva [64], liver homogenate [49], intestinal aspirates [76], cell cultures [68,83], bronchial secretions [74], milk [84] and tissue [67].…”

Determination of cocaine and benzoylecgonine by direct injection of human urine into a column-switching liquid chromatography system with diode-array detection

“…In this way, Larsen and colleagues [26] published a procedure for the determination of COC and BZE in urine using a cyano precolumn in a column switching system. On the other hand, we have reported [27] a method for the quantification of these analytes in human blood plasma samples using switching devices with an extraction precolumn packed with restricted access material. In that case, the high protein content of the blood samples forced the use of this type of precolumns that are very expensive for a routine analysis.…”

Tropane alkaloid analysis by chromatographic and electrophoretic techniques: An update

“…The method was then applied for the determination of atropine in plasma after intravenous administration to hospitalised patients. Similarly, a column-switching method for the determination of cocaine and benzoylecgonine in human blood plasma samples was developed [136]. A 50-l plasma sample was introduced to an alkyl-diol-silica ADS-C18 extraction precolumn.…”