Validation method and proficiency test for the determination of free and hydrolysed formaldehyde

Abstract

Formaldehyde resins are usually used in the textile industry to prevent wrinkling, as well as for conservation of textile artifacts. The International Agency for Research on Cancer (IARC) classified formaldehyde as carcinogenic to humans. There are several regulations regarding the amount of formaldehyde found in textiles, for example Oeko-Tex Standard 100, REACH and European Ecolabel. In the present work, a spectrophotometric method for quantitative determination of free and hydrolyzed formaldehyde extracted through partial hydrolysis by using aqueous extraction was developed and validated. The method is in conformity with SR EN ISO 14184-1:2012 standard. The results of the validation parameters are 0.0117 mg/l for detection limit and 0.039 mg/l for quantification limit. The working field was proved to be linear in 0.15 µg CH2O/ml – 6.00 µg CH2O/ml range with a correlation coefficient of 0.999977. Furthermore, the recovery parameter value is 89.80%. Selectivity was determined in relation to acetic anhydride and the spectrophotometric method was proven to be selective for the quantitative determination of formaldehyde. Besides the validation method, a control diagram has been constructed by measuring a solution of known concentration 10 times. The selected concentrations are 0.16 mg/l and 0.75 mg/l. These solutions are measured before the actual samples. To ensure the accuracy of the results, our laboratory participated to a proficiency test conducted by ASQUAL. The z-score obtained was 0.38 and the number of participating laboratories was 13.