GLC determined the presence of sulfotep, a toxic contaminant in chlorpyrifos formulations (Tak and Chlorfos 48% EC), as well as the effect of different temperatures (25, 35, and 45), direct sunlight, and UV-rays on the stability of chlorpyrifos a.i and sulfotep content in the formed products. The levels of sulfotep in Tak and Chlorfos, measured in micrograms, were 50.01 and 63, respectively. In addition, when exposed to high temperatures, chlorpyrifos a.i. in all tested formulations became unstable (450C). In contrast, sulfotep, is relatively stable. After 336 hours of exposure to 450C, the loss percentage of the active ingredient (a.i) for the chlorpyrifos formulations Tak and Chlorfos was 99 and 99.3 %, respectively, while the loss percentage of sulfotep was 9.998 and 7.08 % for Tak and Chlorfos, respectively. The data showed that direct sunlight was more successful than UV-rays in degrading chlorpyrifos in their tested formulations Tak and Chlorfos with a loss percentage of 79 and 81 % after 48 hours of direct sunlight exposure, respectively. After 48 hours of exposure to direct sunlight, Tak and Chlorfos lost 9.80 and 7.41 % of their sulfotep, respectively. On the contrary, Tak and Chlorfos lost 50 and 51 % of chlorpyrifos (a.i) in their tested formulations after 24 hours of UV exposure, respectively, and lost 6.92 and 5.81 % of sulfotep after 24 hours of UV exposure, respectively.