Analysis of four antidepressants in plasma and urine by gas chromatography-mass spectrometry combined with sensitive and selective derivatization.

A sensitive and selective method was developed for simultaneous determination of four antidepressants (ATDs) in plasma and urine samples by gas chromatography- mass spectrometry (GC-MS) based on an N-nitrosation reaction. In this study, fluoxetine (Flu), nortriptyline (Nor), maprotiline (Map), and paroxetine (Paro) were first derivatized with sodium nitrite to appropriate N-nitrosamines under acidic condition, then the derivatives were easier to detect by GC-MS. The derivatization conditions including the amount of hydrochloric acid, the amount of sodium nitrite, reaction temperature, reaction time and the extraction reagents were optimized. Under the optimal conditions, the limit of detections (LODs) and limit of quantitations (LOQs) were in the range of 0.04-1.38 μg L-1 and 0.14-4.62 μg L-1, respectively. Low, medium, and high concentrations of antidepressants were added in plasma and urine samples, spiked recovery ranged from 85.88%-110.34% for plasma and 80.64%-113.07% for urine, respectively. The derivatization reaction was very quickly, only 5 min was needed for the reaction process, in addition, the proposed method exhibited superior sensitivity and selectivity, it showed sufficient advantages for determination of Flu, Nor, Map, and Paro in plasma and urine of patients.