Aqueous phase hexylchloroformate derivatization and solid phase microextraction: determination of benzoylecgonine in urine by gas chromatography-quadrupole ion trap mass spectrometry.
A derivatization/solid phase microextraction (SPME) method for the determination of benzoylecgonine in urine was developed. The derivatization is conducted directly in 1 mL of urine while sonicating for 3 min with 12 microL of hexyl chloroformate and 70 microL of a mixture containing acetonitrile:water:hexanol:2-dimethylaminopyridine (5:2:2:1 v/v), yielding benzoylecgonine hexyl ester (BHE) as the product. After the 3 min period, an aliquot of 250 microL is transferred to a vial for SPME. After the desired extraction time the 100 microns polydimethylsiloxane SPME fiber was transferred to the GC-MS for separation and analysis with a quadrupole ion trap mass spectrometer. The hexyl chloroformate derivatization and SPME procedures were optimized for compatibility and sensitivity. The method was found linear for 0.10 to 20.0 micrograms/mL (r2 = 0.999) of benzoylecgonine in urine using benzoylecgonine-d3 as an internal standard (1.5 micrograms/mL). Intra-day precisions were 8.8 and 6.8% RSD for 0.30 microgram/mL and 17 micrograms/mL benzoylecgonine standards in urine (n = 6), respectively. Inter-day precision (n = 3) were < or = 3.3% RSD, indicating good reproducibility. A detection limit of 0.03 microgram/mL (S/N = 3) was achieved, thus making the SPME method a simplified alternative to SPE for GC-MS confirmation after EMIT tests for benzoylecgonine which have a cutoff of 0.30 microgram/mL. Quantitative results by SPME and SPE of two clinical urine specimens known positive for cocaine by EMIT were in excellent agreement. Benzoylecgonine was detected by the derivatization/SPME method in 22 out of 22 other urine specimens known positive for cocaine.
Hall
B J
BJ
Department of Chemistry and Biochemistry, University of Texas at Austin, USA.
Parikh
A R
AR
Brodbelt
J S
JS
D002138:Calibration; D003042:Cocaine / Q000031:analogs & derivatives* / Q000652:urine; D005561:Formates; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006801:Humans; D013287:Illicit Drugs / Q000652:urine*; D008956:Models, Chemical; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D005561:Formates; D013287:Illicit Drugs; C083354:chlorocarbonic acid; C005618:benzoylecgonine; D003042:Cocaine