Screening of sulfonamides in waters based on miniaturized solid phase extraction and microplate spectrophotometric detection

A simple and cost-effective screening method for determination of sulfonamides in water is proposed. For this, micro-solid phase extraction based on polystyrene divinylbenzene sulfonated (SDB-RPS) disks was coupled to microplate analysis. Extraction was performed in parallel for up to four samples, and the elution procedure was performed by soaking the SDB-RPS disk in 1 mL of methanol + 0.1% (v/v) ammonia. Miniaturized spectrophotometric determination under microplate format was based on the chromogenic reaction between sulfonamides and p-dimethylaminocinnamaldehyde in organic medium. Several aspects were evaluated, including the derivatization reaction conditions, sample loading rate, and eluent composition using sulfamethoxazole as model compound. Detection of other sulfonamides (sulfadiazine, sulfaquinoxaline, sulfamerazine, sulfanilamide, sulfamethazine, sulfametizole, sulfadimethoxine, sulfapyridine and sulfacetamide) was also evaluated, providing values for limit of detection between 2 and 11 mu g L-1 for a sample volume of 100 mL. The proposed method was successfully applied to different types of water, providing a sample throughput of 5.3 samples per hour, making it a suitable, cost effective and environmental friendly approach for screening purposes.