Determination of Free Formaldehyde in Leather Chemicals

Abstract

Formaldehyde is widely used in the synthesis of various leather chemicals due to its high reactivity and low cost. It is probably introduced into leather when applying the chemicals to processing, and then released during storage and use of leather, which may pose a potential risk to human health. Existing method for determining formaldehyde in leather is helpless to deal with the complicated chemicals. In this study, a method was optimized for determination of free formaldehyde in leather chemicals based on ISO 27587. A 0.5-2.0 g sample of leather chemical (formaldehyde could range from 1.25 to 1250 mg/kg) was heated at 90 oC in nitrogen atmosphere. The released formaldehyde was purged at a flow rate of 300 mL/min for 30 min, captured and derivatized using a bubble absorption tube containing 2,4-dinitrophenylhydrazine absorption solution, and then detected by HPLC-diode array detector. The recovery rate of formaldehyde standard solution was 91.0% with relative standard deviation (RSD) of 4.87% in seven times repeated trials. The repeated determinations of aldehyde tanning agents showed the formaldehyde recoveries higher than 90% and RSD lower than 7%, indicating the accuracy and precision of the method. Powdery amino resins were determined to contain a tiny amount of free formaldehyde using this method. However, it should be noted that hydrolyzed formaldehyde will be formed when the amino resins were dissolved in water and used in retanning, leading to the potential for bringing leather with high content of formaldehyde.