| Abstract
| - A simple, sensitive, and specific liquid chromatography−tandem mass spectrometry (LC−MS/MS) method for determining urinary creatinine was developed and used to evaluate 24 h urine samples collected during an exposure study. Urine (1 µL) was diluted with methanol and then directly applied to LC−MS/MS. Under electrospray ionization (ESI) conditions, the transition molecules of creatinine and creatinine-d3 were observed at m/z 114 > 44 and m/z 117 > 47, respectively. The retention time of creatinine was 0.59 min. The linear range was 1−2000 ng/mL, with a detection limit in urine of 1 ng/mL. LC−MS/MS and colorimetric end-point methods were significantly associated (R2 = 0.8785, p< 0.0001). The LC−MS/MS method to determine creatinine in 24 h urine samples had shorter retention times, was more sensitive, reliable, reproducible, simple, selective, and used a smaller sample size than other LC−MS/MS or commercial methods.
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