Proficiency testing for determination of formaldehyde in leather in China

Formaldehyde can cause serious health hazards to human body. A proficiency testing scheme (CNCA-15-A09) for the determination of formaldehyde in leather was organized involving 162 laboratories in China. The test materials were prepared by adding melamine formaldehyde syntans to a blank sheepskin during tanning process. The tanning was identical to the real production process to assure the representativeness of test materials. The histograms of results for formaldehyde in the leather samples illustrated that the data sets approximated closely to the normal distribution. The mean value was in good agreement with the median value. Hence the assigned values of test materials for proficiency assessment were derived directly from the reported results of laboratories, and the measurement performance for determining formaldehyde in leather were assessed using robust z-scores. And the distribution characteristics of different preparation approaches for formaldehyde stock solution showed that it could greatly influence the process and results of analysis.