HPLC of trazodone in serum after microscale protein precipitation

Trazodone, an anti-depressant medication, is found in serum in the 500-1000 ng/mL range in patients taking therapeutic doses. Because of this relatively high concentration, it has been possible to devise an HPLC assay system using the rapid, convenient microscale procedure described previously by Lam et al. (Clin. Chem. 26, 963 1980) to prepare the sample for chromatography. To 0.1 mL serum were added 0.1 mL acetonitrile and 10 microL of 10% zinc sulfate in water. The mixture was centrifuged and 50 microL of the clear supernatant was injected into a reversed-phase column which was eluted with 65% 0.05 M potassium phosphate-35% acetonitrile, with detection by ultraviolet absorbance at 210 nm. The trazodone elutes in 6 min, clearly resolved from endogenous interferences. The recovery of trazodone added to serum was better than 90%. Peak height was proportional to concentrations in the serum sample from 125 ng/mL to 3000 ng/mL.