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Abstract
There are a range of applications that require the measurement of multiple drugs such as urine analysis, drug determination in water, and screening for drug contamination on surfaces. Some of the procedures used such as enzyme-linked immunosorbent assay (ELISA) are simple but can only determine one drug at a time, and others such as GC-MS or LC-MS are complex, time-consuming, and expensive. In this study, fluorescence covalent microbead immunosorbent assay (FCMIA) was investigated as a simple method for the measurement of multiple drugs simultaneously in three matrices: diluted urine, water, and on surfaces. Five different drugs of abuse or their metabolites (methamphetamine, caffeine, benzoylecgonine (a metabolite of cocaine), tetrahydrocannabinol (THC), the active ingredient in marijuana, and oxycodone) were studied over the range 0–15 ng/ml. There was no measureable cross-reactivity among the drugs at the concentrations studied. Urine dilutions from 1/50 to 1/2.5 were studied and dilutions less than 1/20 had a significant effect on the methamphetamine assay but limited effects on the benzoylecgonine and oxycodone assays and almost no effect on the THC assay. For assays performed in 1/20 urine dilution, water, and diluted surface sampling buffer, least detectable doses (LDD) were 1 ng/ml or less for the drugs. Surfaces spiked with drugs were sampled with swabs wetted with surface sampling buffer and recoveries were linear over the range 0–100 ng/100 cm2 surface loading for all drugs. FCMIA has potential to be used for the measurement of multiple drugs in the matrices studied.