In this note, a determination method for paraquat and diquat using HPLC is described. Paraquat and diquat, which are quaternary ammonium herbicide widely used in the world, are also toxic to human being. Their concentration in urine or serum after ingestion is determined for accurate prognosis.
To determine the concentration in physiological sample, purification by solid-phase extraction is required before HPLC analysis. However, it is difficult to obtain good recovery with C18 cartridge because alkaline solution, in which paraquat and diquat is unstable, should be used to retain the compounds to the solid-phase.
Strong cation-exchange type is also not desirable because solution containing high concentration of salt has to be used for elution from the solid-phase. If the eluted sample is injected into an HPLC system without any dilution or desalting, peak shape often gets worse owing to the salt.
In this note, MonoSpin PBA, which has carboxylate group for weak cation-exchange mode, was used. As a result, excellent recoveries were obtained from urinary sample with simple procedures.