Development and Validation of Liquid Chromatography-Tandem Mass Spectrometry Method for Simultaneous Determination of Tramadol and Its Phase I and II Metabolites in Human Urine

Abstract

Tramadol (TD) has been prescribed frequently in many countries for more than 40 years, but there is a risk of its misuse and trafficking. As a result, drug analysis has numerous legal and socially relevant implications, making it an essential part of modern analytical chemistry. Thus, the method for the detection of TD and its phase I and phase II metabolites in human urine has been developed and validated using a rapid and efficient approach combining liquid chromatography-tandem mass spectrometry (LC-MS/MS) with electrospray ionization. The sample preparation was best performed using dispersive liquid–liquid microextraction. Analysis was performed using an HyPRITY Cl8 column, and isocratic elution with methanol: water (35:65) with 0.2% formic acid was used. TD and its metabolites were detected at 264.2 (TD/M0) with a base peak at 58.2, 250.3758 (M1), 250.3124 (M2), 236.3976 (M3), 222.5361 (M4), and 236.4475 (M5) m/z peaks. TD showed linearity between 0.1 and 160 ng/mL (R2 = 0.9981). The accuracy ranged from 95.56 to 100.21% for the three concentration levels, while the between- and within-day RSD ranged from 1.58 to 3.92%. The absolute TD recovery was 96.29, 96.91, and 94.31% for the concentrations of 5, 50, and 150 ng/mL, respectively. TD’s phase I metabolites, M1–5 along with nine phase II metabolites, such as sulfo- and glucurono-conjugated metabolites, oxidative TD derivatives, and sulfo-conjugated metabolites were also identified in the urine samples. The pharmacokinetics and metabolism data given provide information for the design of possible future research disorders, evaluating drug mechanism and neurotoxicity and for the effective application screening of TD.