and was held for 2 min for re-equilibration. The eluents were monitored by UV detection at a wavelength of 299 nm for chlorpyrifos and at 290 nm for TCP. The chromatographic analysis was performed at ambient temperature. Each sample replicate was injected three times to determine the average peak area. The percentage degradation of the compounds was calculated as the difference between the peak areas of the experimental and control samples, where the peak area of the control was used as the 100% point of reference.