HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETECTION OF RESIDUAL FORMALDEHYDE IN A HEPATITIS-A VACCINE BY USE OF HYDRALAZINE

An assay was developed that is capable of detecting levels of residual formaldehyde in viral vaccine dosage formulations to 0.01 mug/mL. The assay employs incubation of dosage formulation suspensions with hydralazine hydrochloride under mildly acidic conditions and elevated temperatures. Formaldehyde present is derivitized to yield s-triazolo-[3,4-a]-phthalazine. Selectivity of the assay is enhanced by performing reverse phase HPLC after the reaction, and monitoring elution of the fluorescent product. The presence of insoluble aluminum hydroxide in dosage formulations does not affect formaldehyde recovery. The assay was used to determine formaldehyde levels in dosage formulations and in in-process samples of a newly developed Hepatitis A vaccine.