Abstract

Recycled chrome tanning liquors containing formate as masking agent have to be accurately fortified between cycles to ensure consistent results. Up to now, residual formate concentrations have been guessed at because there has been no easy, quantitative assay for formate in such recycle liquors. This work derives a suitable gas chromatographic method which measures formate directly using thermal conductivity detection. Temperature and pH are shown to affect the elution profile and it was found best to separate formate on a Poropak N column from a filtered (0.45/µm) solution at a pH<2 and oven temperature of 160^oC. Unknown formate concentrations are read off directly from a linear, standardised graph. The measurements were shown to be quantitative and the method easy to perform.