Quantification of 3‑chloro-7‑hydroxy-4-methylcoumarin (CHMC) in urine as a biomarker of coumaphos exposure by high-performance liquid chromatography-fluorescence detection (HPLC-FLD).

The organophosphate pesticide coumaphos is used to control Cattle Tick Fever carried by multiple species of ticks and is a known hazard for workers treating livestock. The USDA Cattle Fever Tick Eradication Program requires regular blood draws to measure depressed cholinesterase levels as biomarkers of effect of long-term coumaphos exposure, however, the gap between blood draws may miss intermittent high exposures. Urine biomonitoring can supplement blood draws, offering personnel a sensitive and cost-effective method to monitor short-term exposures. Our objective was to improve and validate a previously published method to analyze the coumaphos metabolite 3‑chloro-7‑hydroxy-4-methylcoumarin (CHMC). Urine samples were hydrolyzed with glucuronidase and then extracted prior to analysis with high-performance liquid chromatography-fluorescence detection. Calibration curves were linear over a wide CHMC range (0.49 - 250.07 ng/mL) with a method detection limit of 0.06 ng/mL. This research will help establish an accessible urine biomonitoring method for assessing coumaphos exposures.•The modified bioanalytical method maintained high sensitivity and specificity while reducing duration of the sample treatment steps and the chromatographic program.•Method validation tests followed the acceptance criteria guidelines in the NIOSH Manual of Analytical Methods.•CHMC levels were measured in workers exposed to coumaphos during livestock treatment.