LC Determination of Trace Amounts of Phenoxyacetic Acid Herbicides in Water after Dispersive Liquid-Liquid Microextraction

Dispersive liquid-liquid microextraction (DLLME) for extraction and preconcentration of phenoxyacetic acid herbicides in water samples is described. After adjusting the pH to 1.5, the sample was extracted in the presence of 10% w/v sodium chloride by injecting 1 mL acetone as disperser solvent containing 25 mu L of chlorobenzene as extraction solvent. The effect of parameters, such as the nature and amount of extraction and disperser solvents, ionic strength of the sample, pH, temperature and extraction time were optimized. DLLME was followed by LC for the determination of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-methyl phenoxyacetic acid. The method had good linearity and a wide linear dynamic range (0.5-750 mu g L(-1)) with a detection limit of 0.16 mu g L(-1) for both the PAAs, making it suitable for their determination in water samples.