Simultaneous Determination of HFBA-Derivatized Amphetamines and Ketamines in Urine by Gas Chromatography-Mass Spectrometry

A single analytical protocol using solid-phase extraction, derivatization with heptafluorobutyric anhydride, and gas chromatography-mass spectrometry can simultaneously measure amphetamine, methamphetamine, MDA, MDMA, MDEA, ketamine, and norketamine in urine. With a 1-mL sample, detection limits range from 15 to 70 ng/mL, and upper limits reach 6000–8000 ng/mL. Precision and accuracy are high, with within-day and between-day coefficients of variation ≤4.95% and accuracy between 96.0% and 110.7% for most analytes. Testing on 107 previously positive urine samples showed good agreement with earlier methods, enabling a single confirmation test for samples screening positive for amphetamines, ketamine, or both.

Study at a glance

Abstract

To facilitate the analysis of targeted drugs under high sample volume testing environment, an extraction, derivatization and gas chromatographic-mass spectrometric analysis method was developed for simultaneously determination of amphetamine (AMP), methamphetamine (MAMP), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyethylamphetamine (MDEA), ketamine, and norketamine in urine. This method utilized solid-phase extraction in conjunction with derivatization using heptafluorobutyric anhydride (HFBA) as the derivatization reagent. Using a 1-mL sample, the limits of quantitation achieved for the analysis of AMP, MAMP, MDA, MDMA, MDEA, ketamine, and norketamine were 25, 15, 60, 60, 70, 25, and 30 ng/mL, respectively. Upper limits of quantitation were 8000 ng/mL for all amphetamines and 6000 ng/mL for ketamine and norketamine. Except for dehydronorketamine (DHNK), within-day and between-day precisions (as expressed in CV%) for quality control samples were ≤ 3.1% and ≤ 4.95%, respectively. Except DHNK, the within-day accuracy ranged between 96.0% and 110.7% and the between-day accuracy ranged between 96.9% and 108.7%. A group of 107 urine samples previously determined to contain the target analytes were analyzed by this new approach. Quantitative data produced by both methods agreed well. With this new approach, we were able to use a single analytical protocol to conduct the confirmation test for samples that preliminarily tested positive (by immunoassay) for amphetamines, ketamine, or both.