Simultaneous Quantification of Cocaine, Amphetamines, Opiates and Cannabinoids in Vitreous Humor

Abstract

A GC-MS method for simultaneous analysis of cocaine (COC), amphetamines (AMPs), opiates, cannabinoids and their metabolites in vitreous humor (VH) was developed and fully validated. VH samples were extracted using solid phase extraction and injected into the GC-MS, using a selected ion monitoring mode. Linearity ranged from 10 to 1000 ng/mL; the exception was anhydroecgonine methyl ester (AEME), for which linearity ranged from 10 to 750 ng/mL. Inter-assay imprecision lay from 1.2 to 10.0%, intra-assay imprecision was <10.4% for all the analytes and accuracy ranged from 95.6 to 104.0%. An limit of quantitation for all drugs was 10 ng/mL and recoveries ranged from 70.4 to 100.1% for basic and neutral compounds; the acid compounds had poor recovery--<40%. The validated method was applied to 10 VH samples taken from individuals whose blood had screened positive for drugs of abuse. All the individuals screened positive for COC in the blood (seven samples) also had positive results in VH; COC concentration ranged from 30.81 to 283.97 ng/mL (mean 186.98 ng/mL) and benzoylecgonine concentration ranged from 11.47 to 460.98 ng/mL (mean 133.91 ng/mL). It was also noticed that, in five cases, cocaethylene was detected. AEME was also quantified in one case. The use of AMP detected by blood analysis was confirmed in the VH of one individual (24.31 ng/mL). However, samples taken from three individuals whose blood tested positive for carboxy-tetrahydrocannabinol presented negative results. The results demonstrated that VH is a suitable alternative biological sample to determine COC, AMPs, opiates and their metabolites.