Analysis of free and bound formaldehyde in squid and squid products by gas chromatography–mass spectrometry

Formaldehyde can be added illegally as a food preservative in addition to the endogenous formaldehyde that naturally occurs in aquatic products. In this study, formaldehyde was derivatized from 2,4-dinitrophenylhydrazine and analyzed using gas chromatography–mass spectrometry to investigate free and reversibly bound formaldehyde in 10 squid and squid products. The results were compared to those obtained by high-performance liquid chromatography (HPLC). The limit of detection was 2.0 mg/kg. The total concentrations of free and reversibly bound formaldehyde were, on average, higher than the free formaldehyde concentration by 26.6 mg/kg. Free formaldehyde made up, on average, 39% of total free and reversibly bound formaldehyde. The sum of the concentrations of free and reversibly bound formaldehyde was, on average, higher than the free formaldehyde concentration by 19.3 mg/kg in the HPLC method. Free formaldehyde made up an average of 39% of total free and reversibly bound formaldehyde in the HPLC method. The use of gas chromatography–mass spectrometry to detect formaldehyde in aquatic products allowed confirmation through retention time and molecular mass information. The monitoring of free formaldehyde in aquatic products and proper control of the manufacturing process could help to reduce the formaldehyde level in shredded squid products. Finally, exposure to formaldehyde from consumption of shredded squid was estimated: it was less than 0.2 mg/kg, which is the oral reference dose suggested by the US Environmental Protection Agency.