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Elimination of Fluconazole Interference in Gas Chromatography/Mass Spectrometric Confirmation of Benzoylecgonine, the Major Metabolite of Cocaine Using Pentafluoropropionyl Derivative

NCJ Number
164342
Journal
Journal of Forensic Sciences Volume: 41 Issue: 3 Dated: (May 1996) Pages: 511-513
Author(s)
A Dasgupta; C Mahle; J McLemore
Date Published
1996
Length
3 pages
Annotation
Fluconazole interferences in a urine specimen positive for benzoylecgonine, the major metabolite of cocaine, is a serious problem; this article reports on an attempt to eliminate these interferences by using a different derivative of benzoylecgonine, the pentafluoropropionyl derivative.
Abstract
Benzoylecgonine is usually confirmed after derivatization by gas chromatography/mass spectrometry to demonstrate cocaine abuse. Recently, Wu et al. showed that fluconazole coelutes with benzoylecgonine after conversion to trimethylsilyl analogs and causes false-negative results in the confirmation test; however, fluconazole did not interfere with the screening assay when using a enzyme multiplied immunoassay technique. The study shows that by converting benzoylecgonine to the corresponding pentafluoropropionyl derivative, the interference of fluconazole can be completely eliminated. The pentafluoropropionyl derivative of benzoylecgonine eluted at 14.7 minutes, and the derivatized fluconazole eluted at 15.6 minutes. The mass spectral fragmentation pattern of derivatized benzoylecgonine was distinctively different from the mass spectral features of derivatized fluconazole in both electron ionization and chemical ionization mode of operation of mass spectrometers. The quantitation of benzoylecgonine in positive urine specimens was not affected when the specimens were supplemented with 50 mg/mL of fluconazole. 2 figures, 1 table, and 11 references

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