Direct determination of unconjugated HVA in human plasma filtrates by HPLC coupled with dual‐electrode coulometric electrochemical detection

We report a procedure for the rapid determination of unconjugated homovanillic acid (HVA) in human plasma by cartridge filtration followed by direct injection into an isocratic HPLC system coupled with dual‐electrode coulometric electrochemical detection. Sample preparation is rapid and more than 72 samples can be studied in 24 h using an automated HPLC system. The intra‐ and interassay precisions of the assay equal or exceed previously reported methods. While this methodology has been employed to study plasma free HVA, the concept of the technique may be applicable to other compounds, as well as different assay procedures, to greatly decrease sample preparation time.