Abstract
The present study was concluded to throw light on detection of thiobencarb and penoxsulam residues in some fresh water fish. The examined fish samples were collected randomly from different farms in Kafr El Sheikh Governorate, Egypt at the time as fresh samples (50 of each Tilapia and Cat fish samples), The samples were placed in plastic bags then transferred to the laboratory without undue delay in an ice box and subjected to analysis by HPLC for the detection of Thiobencarb penoxsulam residues in each species. Then, Studying the effect of heat treatment (boiling and grilling) on higher and lower limits of herbicides residues in examined samples and calculate the reduction percent. The results of analysis revealed that the mean of thiobencarb residues were 0.298 ±0.242 ppb in Tilapia samples and the percent of accepted samples were 42.9 and by applying heat on these residues the reduction occur in boiling by 88.09% and in grilling by 75.17%.While, the mean of thiobencarb residues were0.089±0.122ppb in Cat fish, the percent of accepted samples were 44 and by applying heat on these residues the reduction occur in boiling by 88.07% and in grilling by 78.81%. On the other hand the mean of penoxsulam residues were 0.251±0.279 ppb in Tilapia samples and the percent of accepted samples were 50 by applying heat on these residues the reduction occur in boiling by 100% and in grilling by 75.48%.While the mean of penoxsulam residues were 0.124±0.181ppm in Cat fish, the percent of accepted samples were 48.1 and by applying heat on these residues the reduction occur in boiling by 100% and in grilling by 75.54%.

Key words: Thiobencarb residues , penoxsulam residues,HPLC,Nile Tilabia fish,Cat fish.