Paraquat quantification in deposits from drinking water networks

Abstract

The aim of this work was to develop an expeditious analytical methodology to evaluate the paraquat (PQ) contamination level in deposits from drinking water networks. To the best of our knowledge, no other study has focused on this matter, which is of crucial importance, for instance, to obtain a fast response after a suspicion of contamination (emergency situation). Three deposits representative of those typically found in drinking water networks were used: two iron-based – S2 and S3, and a calcium rich one – S4. The analytical method consists of an easy and fast extraction step, using a saturated ammonium chloride solution, followed by direct injection in a high performance liquid chromatograph with a diode array detector (HPLC-DAD). A matrix-matched calibration was performed for paraquat, in the range of 5 to 193 μgPQ per g deposit, and a limit of detection of 0.1 μgPQ per g deposit was reached. The good percentages of recovery (90–101% on average) and the low relative standard deviations observed for the PQ–S3 system (3, 4 and 2% for 20, 80 and 160 μgPQ per g deposit, respectively) enable a reliable quantification of paraquat, even at the lowest contamination levels. The developed analytical methodology can also be extended for diquat and also proved to be suitable for paraquat quantification in other types of deposits.