Evaluation of perfluorooctanoic acid purity based on potentiometric titration

Reliable purity evaluation of perfluorooctanoate (PFOA), surfactants, is desired for accurate quantification because purity is essential for the preparation of calibration solutions. To meet this requirement, homogenized PFOA monohydrate was prepared for the improvement of repeatability, and was diluted in aqueous NaOH for measures of poor solubility on titration analyses, which is commonly used for purity evaluation of chemicals. Purity based on the titration technique was determined by subtracting the mass fractions of impurities related to PFOA analyzed by using a LC/MS from those of purity expressed as acids analyzed by neutralization potentiometric titration using a potentiometric titrator. To validate the obtained result, another analytical result based on the mass balance technique was obtained by subtracting the mass fractions of every impurity. From the results in this study, this titration technique can help evaluating the reliable purity of analytes similar to PFOA.