3. 1. Matrix effect assessment The response of the detector system to certain pesticide may be affected by the presence of co-extractives from th sample 12,21-23]. These matrix-effects may be observed as a increase or decrease in response, compared with those produce by solvent solutions of the analyte. The effect of the matri can be variable and unpredictable in the occurrence of measu able effects. The matrix effect on the detectors (ECD and NPD)