Quantitative liquid-chromatographic technique for the simultaneous assay of tricyclic antidepressant drugs in plasma or serum.

A quantitative "high-pressure" liquid-chromatographic assay for tricyclic antidepressant drugs in plasma or serum is described in which amitriptyline, nortriptyline, imipramine, desipramine, doxepin, and desmethyldoxepin are separated with a 10-micrometer particle size silica column and a methanol/NH4OH/NH4NO3 solvent system. The drugs and two internal standards are extracted with hexane/isoamyl alcohol, the solvent layer is evaporated at 40 degrees C, and the drugs are detected at 254 nm. Drug concentrations are linear with absorbance from 25 to 1000 micrograms/L; within-assay and between-assay CVs are less than or equal to 10%.