Determination of residual trifluoroacetate in protein purification buffers and peptide preparations by ion chromatography.

Trifluoroacetate (TFA) is commonly used in a variety of pharmaceutical applications. Because of its toxic nature, it is important to reliably measure the effective removal of TFA. We developed an ion chromatography (IC) method to determine the concentration of residual TFA in samples found in the pharmaceutical industry. A high-capacity anion-exchange column was used to separate trace trifluoroacetate from an excess of chloride, phosphate, and other anions without the need for sample preparation. TFA was detected by suppressed conductivity. A method with four KOH eluent step changes was optimized and reproducibly executed using automated generation of the KOH eluent. We used this method to determine TFA in the following samples: a phosphate-buffered saline (PBS), an acetate-buffered saline containing protein, and a commercial peptide. The method detection limits for TFA in these samples were all less than 90 ng/ml.