Standard Specification
Standardized analytical protocols establish the chromatographic procedure for extracting and quantifying hexavalent chromium compounds present in finished leather goods and footwear materials. Within leather processing supply chains, iso 17075-2 specifies high-performance liquid chromatography with ion exchange columns and photometric detection to replace older colorimetric diphenylcarbazide methods. Leather specimens undergo extraction in an alkaline phosphate buffer solution at pH seven point five to eight point zero without causing oxidation of trivalent chromium.
The filtered extract passes through an analytical ion chromatography column where hexavalent chromium separates cleanly from interfering tannins and synthetic retanning agents. Post-column derivatization with 1,5-diphenylcarbazide forms a colored complex measured at five hundred and forty nanometers. Eliminating colorimetric matrix interferences prevents false-positive results in heavily dyed leathers.
Chromatographic Extraction
Degreased leather pieces shake within nitrogen-purged phosphate buffer solutions for three hours to leach soluble hexavalent chromium into the aqueous phase. Nitrogen gas blankets the extraction vessel to prevent ambient oxygen from converting trivalent chromium into hexavalent species during liquid agitation. The extract undergoes microfiltration through polytetrafluoroethylene membrane syringe filters to remove suspended solids and collagen fibrils before auto-sampler injection.
Separation takes place across an anion-exchange stationary column that retains chromate anions while organic matrix components elute to waste. Derivatization occurs inside a heated reaction coil immediately prior to photometric measurement, ensuring reproducible color development.
Detection Boundary
The method maintains a formal quantification threshold of zero point five milligrams per kilogram of dry leather weight. Samples yielding signals below this threshold are certified as non-detectable under European and global product safety frameworks.
Regulatory Consequence
Tannery shipments fail European REACH compliance whenever leather items reveal hexavalent chromium above the three milligrams per kilogram legal threshold for skin-contact items. Footwear manufacturers reject whole leather hides upon receiving adverse laboratory reports, shifting storage and disposal costs back to the tanning facility. Vegetable tannins and fatliquors occasionally oxidize during intense heat drying, generating trace hexavalent chromium on warehouse shelves.
Laboratory verification under this chromatographic standard shields downstream brands from product recalls and legal liability.
