Abstract: A simple,rapid method for sample preparation for in situ determination of formaldehyde in water-soaked foodstuffs was developed.The advantage of this method is that the sample pretreatment and the color reaction can be finished simultaneously.The protein and the fatty compounds in the sample are precipitated by zinc acetate and potassium ferrocyanide,then the chromogenic reaction of acetylacetone with formaldehyde released from the sample in weak-acid medium and boiling bath takes place immediately.Various experimental parameters were studied and optimized,so the analysis of each sample can be completed in 10 min. More than 100 kinds of practical samples were analyzed.The results were in good agreement with those obtained by the standard method,and the relative errors of determined values were less than 5% if the formaldehyde concentrations were more than 10 mg/kg.The background concentration of formaldehyde in practical samples and the standard for judging samples containing spiking formaldehyde were studied.The determined values less than 10 mg/kg were regarded as the background concentration of formaldehyde in samples,and the determined values more than 20 mg/kg were regarded as the evidences that the samples contained spiking formaldehyde.

Key words: Water-soaked foodstuffs, Formaldehyde, Fast sample pretreatment, In situ determination