Table I. Analyses of Consecutive Urine Catches Following Marijuana Smoking for Cannabinoids by GC/MS and Emit d.a.u. Assay

To the Editor: The United States Department ofTransportation procedures for workplace drug-testing programs authorize the collection of "split " urine specimens (1). If the split sample method is employed, the donor urinates into a single collection container, and the collection site person, in the presence of the donor, pours the specimen i to two specimen bottles. The specimens are sealed and shipped to the laboratory for drug testing. The process is designed to produce identical specimens that, upon analysis, would produce quivalent results. For comparison with the split method of collection, we questioned if consecutively collected specimens would differ in drug content between catches. Our working hypothesis was that there would be no difference in drug concentration in consecutively collected specimens. To test his hypothesis, we arranged for subjects who had provided informed consent and were participating in a controlled study of the excretion pattern of cannabinoid metabolites, tocollect sequential urine specimens. The subjects were instructed to begin urine collection, halt micturition when they had produced sufficient volume (approximately 30mL), change their container, and proceed. Up to four consecutive urine catches were collected at one time. Samples were collected in this manner just prior to smoking marijuana, nd throughout the day following drug administration on three different test days. Th