A rapid and reliable method for the quantitation of tricyclic antidepressants in serum using HPLC-MS/MS

Objective: Here we describe a liquid chromatography-tandem mass spectrometry method for the detection of tricyclic antidepressant drugs (amitriptyline, desipramine, imipramine, and nortriptyline) in serum. Design and methods: Following a protein precipitation from serum and dilution of supernatant with water, these analytes and their internal standards (deuterated versions of each drug) were injected, separated, and eluted from a Hypersil Gold C-18 (50 × 2.1 mm) analytical column with a gradient of water and acetonitrile each with 0.1% formic acid. Analytes were then ionized and detected over a 3.5 minute analysis time by electrospray ionization mass spectrometry with multiple reaction monitoring. Matrix effects were characterized using three methods: post-column infusion, pre- and post-extraction addition of analyte to matrix, and comparison of neet to serum preparations. Results: The inter-day and intra-day coefficients of variation for all compounds were ≤ 12%. The limit of detection for all drugs was < 15 ng/mL and the limit quantitation for all drugs was < 22 ng/mL. Recoveries were between 97 and 131% for all drugs. Patient method comparison and proficiency samples were run with acceptable results. Conclusion: We have developed a specific and sensitive method for rapid quantitation of tricyclic antidepressants in serum, suitable for use in the clinical laboratory.