PREVENTION OF TRICYCLIC ANTIDEPRESSANT ADSORPTION LOSS WITH DIETHYLAMINE DURING SOLVENT EVAPORATION

The authors evaluated the adsorption loss of tricyclic antidepressants in analytical procedures with solvent extraction and evaporation. In standard procedures with the use of triple solvent extraction between alkalinized and acidified samples before chromatographic analysis, the adsorption loss was more significant with the demethylated metabolite s. As much as 50% adsorption loss can occur; this irreversible loss ca n be accounted for entirely during the solvent evaporation step. Becau se of differential adsorption loss among parent drugs, metabolites, an d internal standards, the analytical methods usually had wide within-d ay and day-to-day variations. The authors found that the addition of a s little as 0.05% diethylamine to the extract before evaporation compl etely eliminated the adsorption loss of amitriptyline-nortriptyline, i mipramine-desipramine, and doxepin-desmethyldoxepin, with subsequent i mprovement in procedure performance. This simple modification can be a dopted readily by all laboratories that use solvent extraction and sub sequent chromatographic analysis of tricyclic antidepressants.