HPLC Analysis of Drugs in Saliva on Zodiac HST RP Column

The detection of three drugs—dextromethorphan, amitriptyline, and trimipramine—in saliva was carried out using mixed-mode chromatography on the Zodiac HST RP reversed-phase anion-exchange column. No sample preparation was necessary, as salivary proteins were excluded from retention under the applied conditions and eluted in the void volume due to a cation-exclusion effect. At the current mobile phase pH, both the column surface and proteins are positively charged, preventing interaction.

The mobile phase—comprising acetonitrile, water, and formic acid—is fully compatible with LC/MS detection. This robust and selective method is suitable for analyzing hydrophobic basic drugs in complex biofluids with minimal sample handling.