Methods for sample preparation of the s-triazine herbicides and their degradation productsrnin environmental water samples using supported liquid membrane (SLM) has beenrndeveloped. The herbicide compounds were selectively extracted from the flowing donorrnsolution into a porous polytetrafluoroethylene (PTFE) membrane impregnated with 11-rnundecane, di-II-hexylether alone or with 25% 6-undecanone and 50% of II-undecane. Afterrndiffusion through the hydrophobic membrane the s-triazine herbicide compounds werernirreversibly trapped into acidic acceptor phase of lower pH. The Effects of differentrnexperimental variables governing the efficiency of the extraction process have beenrnthoroughly studied and optimized. These include the pH of both the donor and acceptorrnsolutions, donor flow rate, ionic strengths and the analyte trapping conditions.rnFurthelIDore, the conditions for attaining maximum emichment factor fi'om the membranernextraction have been investigated.rnSelectivity of the membrane technique developed was compared with one of thernmost frequently used technique for sample preparation of organic pollutants, solid phasernextraction (SPE) in off-line mode. It was observed that the chromatograms obtained usingrnthe SLM methodology were cleaner, indicating the good selectivity of the extractionrnmethod. The liquid membrane serves as a barrier for interfering compounds, and neutralrnmolecules may not be emiched. The limit of detection for the extracts using SLMrntechnique was also comparable to that of the SPE. The possibility of determining thernextraction efficiency, and thus the emichment factor, fi'om the donor waste was alsorninvestigated. The results obtained from both the acceptor concenh'ate and the donor wasternagreed well, which in turn indicated efficient permeation through the liquid membranernthereby giving minimum memory effects.