Routine monitoring of antibiotics in water and wastewater with a radioimmunoassay technique

Antibiotics are one of a group of pharmaceutical compounds that have been found in lakes and streams throughout the world and the occurrence of these compounds in the environment has raised concerns regarding the toxicity to aquatic organisms and the emergence of strains of antibiotic-resistant bacteria. The objective of this study was to assess the use of a relatively simple coupled solid-phase extraction (SPE)/radioimmunoassay (RIA) method for screening and/or monitoring tetracycline (TC) and sulfonamide (SA) compounds in water. Cross-reactivity of TCs and SAs was used to determine the specificity of the assays. The results indicate that TC, oxytetracycline (OTC), chlortetracycline (CTC) of the investigated 5 TCs, and sulfamethazine (SMT), sulfamethoxazole (SMX), sulfadimethoxane (SDM) and sulfathiazole (STZ) of the investigated 6 SAs in water matrix cross-react to a similar degree within each family in RIA and SPE/RIA. Water samples were collected across a watershed in northern Colorado in addition to the influent and effluent of a wastewater treatment plant. SPE/RIA analysis of these samples was compared with SPE/liquid chromatography (LC)-mass spectrometry (MS) quantification of 5 TC and 6 SA compounds. Results of the study indicate that SPE/RIA can be an effective technique for monitoring antibiotic compounds in waters suspected to be contaminated with these compounds. The coupled method provides a sufficiently low detection limit (0.05 μg/L) to screen large sample sets at environmentally relevant concentrations. The method provides a semi-quantitative composite measurement of similar compounds in an antibiotic family without complex and expensive analytical equipment.