A novel approach for determination of paraquat based on dried blood spot (DBS) extraction and UHPLC-HRMS analysis

Paraquat is an effective herbicide chemical but a highly toxic compound for humans and animals. The measurement of paraquat concentration in blood is important to clinic or forensic practice. Herein, a method has been developed for the analysis of paraquat in human blood using dried blood spot (DBS) extraction and subsequent UHPLC-HRMS analysis. Three droplets (100 μL each) of blood were spotted on the Whatman® FTA classic card and then let dry by microwave irradiation (1200 W) for 5 min to prepare DBS. An 8 mm diameter punch was removed from the center of DBS and extracted with 190 μL of mobile phase (20 mM ammonium acetate with 0.1% formic acid and 5% acetonitrile in ultra-pure water) and 10 μL of internal standard (paraquat-d8, 100 ng/mL). After ultrasonic treatment for 10 min, the tube was centrifuged, and the supernatant was then filtered by 0.2 μm membrane and injected into the UHPLC-HRMS system. The method was validated considering the following parameters: selectivity, LOD and LLOQ, linearity, precision, accuracy. The method showed satisfactory linearity in the range of 1-1000 ng/mL, with high determination coefficient (0.9986). LOD was 0.5 ng/mL, and LLOQ was 1 ng/mL. Selectivity, intra and inter day precision and accuracy were acceptable. The validated method was then applied to authentic blood samples and has proved to be a simple, fast and reliable procedure for the determination of paraquat in blood.