Determination of quetiapine in human plasma by LC-MS/MS and its application in a bioequivalence study

A selective, sensitive and simple high performance liquid chromatography tandem mass spectrometric (HPLC-MS/MS) method for determining quetiapine in human plasma was developed and validated. One-step protein precipitation with acetonitrile was used to pretreat plasma samples. Carbamazepine was used as internal standard. An automated liquid handling workstation with 96-well protein precipitate plate was used to facilitate the process. The chromatographic separation was achieved on a Waters Xbridge C₁₈ column (3.5μm, 2.1mm×50mm). Gradient elution was set with a mobile phase of acetonitrile/water (containing 10mM ammonium acetate and 0.1% formic acid).The flow rate was 0.4mL/min and total analytical run time was 3min. The analysis was conducted using a triple quadrupole tandem mass spectrometer with an electrospray ionization source operating in positive ion mode. The multiple reaction monitoring of transition were m/z 384.2→253.1 for quetiapine and m/z 237.0→194.0 for carbamazepine, respectively. The linear concentration range for the standard curve of quetiapine was 0.5-400ng/mL for a 5μL injection of the pretreated sample (original plasma sample, 50μL). The intra-day and inter-day accuracy and precision were all less than 15%. The method was successfully used in a bioequivalence study comparing two quetiapine extended-release tablets in Chinese volunteers.