Development and method validation for testing formaldehyde in resin

Abstract

Center of Measurement and Standard Accreditation, Faculty of Science, Prince of Songkla University routinely provides testing specification of synthetic resins. This study aimed to develop and validate an in-house method for determining formaldehyde in resin glue. The method involved distillation of the resin glue to release formaldehyde and reacting it with cyanide which led to a cyanohydrin reaction in alkaline conditions. Then, the amount of formaldehyde was determined by the titration method. The results of the method validation showed that, for the amount of formaldehyde in resin glue, the Limit of Detection (LOD) was 0.31 %w/w.  The theoretical and practical limits of quantitation (LOQ) were 0.32 %w/w and 5 %w/w, respectively. By adding formaldehyde standard into resin glue (spiked samples) at low (5 %w/w), medium (15 %w/w), and high (30 %w/w) concentration levels, it was found that the method’s accuracy passed the acceptance criteria at the concentration of 5 %w/w (in the range of 95-102%) and at the concentrations of 15 and 30 %w/w (in the range of 98-101%), respectively.  Thus, all accuracy tests passed the acceptance criteria. Likewise, the precision tests were performed by repeating the tests on the same day (Repeatability) and at different days and times (Reproducibility). It was found that all tests passed the acceptance criteria with the Relative Standard Deviation (%RSD) not exceeding 10%. Therefore, the developed method for testing the amount of formaldehyde in resin glue and its method validation can be used as a laboratory method for testing formaldehyde in resin glue and is in accordance with the objectives of the experiment. In the near future, this approach could lead to method development for formaldehyde determination in other resin glues.