Development of LC-MS/MS analytical method for the rapid determination of Diquat in water and beverages

This study aimed to develop simple, fast, and sensitive methods for the determination of diquat (DQ) in various matrices such as water and beverages. For water, direct injection was tested first, however, the sensitivity of the incurred samples were too low and couldn't possibly achieve the targeted limit of quantification. Hence, dilution with "weaker" injection solvents were tested, and the final conditions involved the dilution of water with acetonitrile (0.4 % ammonium hydroxide) which increased the sensitivity by more than ten times. Nevertheless, the beverages samples needed further treatment to achieve acceptable spiked recovery. The final conditions involved extraction using the aforementioned solvent, followed by heating and partitioning. Both of the methods satisfied the validation requirements, with an average recovery ranging from 85.9 to115 % and associated relative standard deviation (RSD %) within the range 3-8. Further applications on real samples were done to test the levels of contamination.