Determination of sulfophenyl carboxylic acids in agricultural groundwater samples by CE with ultraviolet absorption detection

An analytical method for the determination of six sulfophenyl carboxylic acids, namely (p-sulfophenyl)acetic, 2-(p-sulfophenyl)propionic, 2-(p-sulfophenyl)butyric, 3-(p-sulfophenyl)butyric, 4-(p-sulfophenyl)butyric, and 5-(p-sulfophenyl)valerianic acid, in agricultural irrigation water samples was developed. It involves an SPE procedure, an on-line preconcentration normal stacking mode and subsequent separation and determination using CE with UV detection (CE-UV). p-Sulfobenzoic acid was used as internal standard. The compounds were separated with an uncoated capillary and a 25 mM ammonium acetate/acetic acid buffer solution (pH 5.5) with 2-propanol (30% v/v) and 0.75 mM CTAB. Analyses were run at -25 kV, 25 degrees C, and 100 s of hydrodynamic injection with UV detection at 225 nm. Quantification limits found ranged between 4 and 6 ng/mL. The proposed method was validated using a recovery assay. It was satisfactorily used for the determination of these compounds in groundwater samples to track down the biodegradation of linear alkylbenzene sulfonates in an agricultural soil from the fertile plain of Granada (Spain).