GC Determination of Methamidophos in Water

GC was applied to the determination of methamidophos in water. The water sample (50.00 mL) was evaporated to near dryness by rotary evaporator and extracted thrice with 5 mL of ethyl acetate in each extraction. The extracts were combined and concentrated to 1 mL in an evaporation tube. The solution was separated on HP-1701 capillary column and detected by FPD. Linear relationship between values of peak area and mass concentration of methamidophos was kept in the range of 0.050-1.00 mg·L-1 with detection limit (3S/N) of 0.001 mg·L-1. Tests for recovery were made by standard addition method at 3 concentration levels, giving values of recovery and RSD′s (n=5) in the ranges of 84.0%-91.2% and 3.4%-5.9% respectively.