Verification of spectrophotometry method for free formaldehyde analysis in leather

Method verification of free formaldehyde analysis in leather has been carried out with reference to ISO/TS 17226:2003 – Leather – Chemical Test – Determination of Formaldehyde Content. This test used snow-white goat leather samples and used a colorimetric method with a spectrophotometer instrument. The verification parameters used were linearity, Limit of Detection (LOD), Limit of Quantitation (LOQ), precision and accuracy. The free formaldehyde content obtained was 54.4365 ± 2.1077 mg/kg with the largest contributor to uncertainty measurement was the repetition of analysis (precision). The linearity test was using a calibration curve with a range concentration of 0 – 3 µg/mL and showed a linear result (R² = 0.9993). The Limit of Detection (LOD) and Limit of Quantitation (LOQ) were 0.0967  µg/mL and 0.3223  µg/mL. Precision was measured using the repeatability method and resulted in %RSD was smaller than 2/3 CV Horwitz (1.86 > 5.85). Accuracy was determined by calculating the %recovery of the spike matrix. The test result showed good accuracy because they were in the range of 80 – 120%. All method verification parameters of tested showed conformity with the range of standards so that the laboratory can show good performance in free formaldehyde analysis of leather.