Determination of nortriptyline in human serum by fully automated solid-phase extraction and on-line high-performance liquid chromatography in the presence of antipsychotic drugs.

A fully automated on-line method for determination of nortriptyline in human serum was developed using an ASPEC XL (Gilson) solid-phase extraction apparatus in combination with high-performance liquid chromatography. Solid phase extraction was performed on cyanopropyl cartridges. HPLC was carried out using a C18 column with a mobile phase of acetonitrile-0.01 M triethylamine (34:66 v/v) buffer, pH 3.0. UV detection was at 242 nm. The Inter-day CV% was <5%. Comparison with liquid-liquid extraction of serum from patients treated with nortriptyline showed good agreement. Studies of analytical interference from coadministered psychoactive drugs revealed that only imipramine and a methotrimeprazine metabolite interfered.