In the present work, a method was developed and optimized aiming to determinate the herbicides paraquat (PQ) and diquat (DQ) in human
plasma and urine samples. An initial procedure of chemical reduction of the analytes by adding NaBH4 directly in the buffered samples (pH 8.0)was
performed. This procedure was necessary to convert the quaternary ammonium substances into more volatile compounds for gas chromatographic
analysis. The reduction compounds were extracted with C18 cartridges (solid-phase extraction). Ethyl paraquat (EPQ) was used as internal standard
(IS). Gas chromatography–mass spectrometry (GC–MS) was used to identify and quantify the analytes in selected ion monitoring (SIM) mode.
The limits of detection were 0.05 mg/l for both PQ and DQ. By using the weighted least squares linear regression (1/x