Simultaneous quantitative determination of paracetamol and its glucuronide conjugate in human plasma and urine by liquid chromatography coupled to electrospray tandem mass spectrometry: application to a clinical pharmacokinetic study.

A specific, sensitive and rapid method based on high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) was developed for the simultaneous determination of paracetamol (APAP) and its glucuronide conjugate (PG) in human plasma and urine. Plasma samples were precipitated with the mixture of acetonitrile and propylene glycol (90:10, v/v) solution and urine samples were diluted with the mobile phase, which were used to isolate the analytes from biological matrices followed by injection of the extracts onto a C(18) column with isocratic elution. Detection was carried out on a triple quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode using positive electrospray ionization (ESI(+)). The method was validated over the concentration range of 10-30,000 ng/mL and 100-6000 ng/mL for APAP in human plasma and urine as well as 10-15,000 ng/mL and 200-60,000 ng/mL for PG in human plasma and urine, respectively. Inter- and intra-run precisions of APAP and PG were less than 15% and the accuracy was within 85-115% for both plasma and urine. The average extraction recoveries were 93.1% and 89.1% for APAP, and 93.7% and 92.3% for PG in human plasma and urine, respectively. The linearity, recovery and stability were validated for APAP and PG in human plasma and urine. The method proved to be simple, robust and time efficient.