Brunk S D
Toxicology Department, Baptist Regional Laboratories, Memphis, Tennessee 38105.
J Anal Toxicol. 1988 Sep-Oct;12(5):290-1. doi: 10.1093/jat/12.5.290.
A case of a false negative THC metabolite confirmation by GC/MS is presented. A urine specimen testing positive by the EMIT d.a.u. Cannabinoid 100-ng assay was subjected to confirmation by a GC/MS procedure designed to detect the methyl derivative of 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH). No methylated THC-COOH was found. Analysis of the specimen by the TOXI-LAB Cannabinoids TLC procedure yielded a positive confirmation. Subsequent work-up of the specimen revealed a high concentration of ibuprofen, which is shown to interfere with the methylation of THC-COOH. Reanalysis of the specimen by GC/MS with an increased amount of methylating reagent yielded a positive result.
本文介绍了一例通过气相色谱/质谱法（GC/MS）对四氢大麻酚（THC）代谢物进行假阴性确证的案例。一份经EMIT d.a.u.大麻素100 ng检测呈阳性的尿液标本，采用旨在检测11-去甲-δ9-四氢大麻酚-9-羧酸（THC-COOH）甲基衍生物的GC/MS程序进行确证。未发现甲基化的THC-COOH。采用TOXI-LAB大麻素薄层色谱法（TLC）对该标本进行分析，结果确证为阳性。对该标本的后续检查发现了高浓度的布洛芬，结果表明布洛芬会干扰THC-COOH的甲基化。使用增加量的甲基化试剂通过GC/MS对该标本进行重新分析，结果呈阳性。
