High-purity water obtained by a Milli-Q purification system (Millipore, Bedford, MA) was used throughout the study. Amitryptiline, citalopram, clomipramine, N-desmethylclomipramine, dothiepin, fluoxetine, imipramine, mianserin, mirtazapine, nortryptiline, paroxetine, sertraline, trimipramine and venlafaxine (1 mg/mL) and deuterated internal standards (IS), clomipramine-D 3 and trimipramine-D 3 (100 µg/mL), were purchased from Cerilliant (Round Rock, Texas, USA). Methanol (MeOH, gradient grade) and ethyl acetate were supplied by Merck (Darmstadt, Germany).
Standards stock solutions of each drug, prepared in MeOH at 1 mg/mL, were stored at -20ºC. Standards solutions of the mixtures of all compounds at 5 mg/L were prepared by appropriate dilution of the stock solutions in MeOH. Single or multiple drug working solutions were prepared by accurate dilution of the previous solution in MeOH.
Clomipramine-D 3 and trimipramine-D 3 were added before completing the volume with MeOH, leading to final concentrations of 5 mg/L.
Standards stock solutions of each drug, prepared in MeOH at 1 mg/mL, were stored at -20ºC. Standards solutions of the mixtures of all compounds at 5 mg/L were prepared by appropriate dilution of the stock solutions in MeOH. Single or multiple drug working solutions were prepared by accurate dilution of the previous solution in MeOH.
Clomipramine-D 3 and trimipramine-D 3 were added before completing the volume with MeOH, leading to final concentrations of 5 mg/L.