Validation of Methods on Formalin Testing in Tofu and Determination of 3,5-diacetyl-dihydrolutidine Stability by UV-Vis Spectrophotometry

Formalin is a food preservative that is prohibited by the government, but the abuse of these chemicals is still widely found. The presence of formalin can be detected by using a typical reagent that can ensure the presence of formaldehyde qualitatively and quantitatively. This research was conducted to validate the method of determining formalin in tofu by using Nash reagent in UV-Vis spectrophotometry. The addition of Nash reagent will lead to the formation of diacetyldihydrolutidin complex. The study was performed by stability test of deacetyldihydrolutidine complex against time and pH. Validation of methods for formalin testing in tofu with diacetyldihydrolutidine by UV-Vis spectrophotometry. The results showed that 3,5-diacetyl-dihydrolutidine complex is stable at pH of 7 and stable in the range of 70-120 minutes. The validation shows that the method gives good precision and accuracy of 83.78%. The method has the limit of detection of 1.3681 mu g/mL, limit of quantification of 4,5603 mu g/mL, and the estimated uncertainty of measurement of 1.30 mu g/mL. The test showed that the tofu contained formalin 3.09 +/- 1.30 mu g/mL. These values provide information that this method can be used as a procedure for the determination of formalin on tofu.