Trace level determination of perfluorinated compounds in water by direct injection

A new, fast LC–MS/MS method for the determination of perfluorinated surfactants in water samples by direct injection without pre-concentration is reported. The current method requires only 4 min to analyze nine perfluoroalkyl compounds in a single analytical run. Standard addition and internal standard quantification were used to determine the level of some perfluorinated carboxylic and sulfonic acids, including perfluorooctanoic sulfonate (PFOS) and perfluorooctanoic acid (PFOA), in Great Lakes water samples. Statistically significant differences were observed between the results obtained using different quantification methods. A relatively small difference between the PFOS values obtained with the standard addition method, with and without peak area normalization, clearly indicates that standard addition is the best quantification method when mass-labeled standards are not available. Based on the paired t-test statistical analysis, the concentrations calculated using external standardization were the least accurate, with the highest mean difference from the standard addition calculated values. Both PFOS and PFOA were present at less than 10 ng l−1 in all Great Lake samples. Higher levels were detected in tributaries of Lake Ontario and effluents from sewage treatment plants.