Sample preparation and liquid-chromatographic analysis for tricyclic antidepressants in serum

We report two separate sample-preparation procedures and a "high-pressure" liquid-chromatographic method for quantitating nine tricyclic antidepressant drugs: trimipramine, doxepin, amitriptyline, imipramine, desmethyldoxepin, nortriptyline, desipramine, maprotiline, and protriptyline. The drugs are extracted from 1 mL of serum by a single manual hexane extraction or by using DuPont's PREP I Automated Sample Processor. The drugs from either process are chromatographed on a mu-Bondapak-CN column with a mobile phase of acetonitrile/methanol/Na2HPO4, 5 mmol/L (60/15/25 by vol), pH 7.0, at a flow rate of 2.0 mL/min. Absorbance at 254 nm is linear with drug concentration from 25 to 1000 mg/L for each drug. With the manual extraction procedure the detection limit was 10 mg/L, absolute recovery 20-44%, within-run precision (CV) 10.1%, and run-to-run precision 11.1%. The performance of automated sample extraction was better, with a detection limit of 5 mg/l, absolute recovery 72-97%, within-run precision 6.1%, and run-to-run precision 6.6%.