A sensitive immunochromatographic assay using colloidal gold–antibody probe for rapid detection of pharmaceutical indomethacin in water samples

One-step membrane-based competitive immunochromatographic assay using colloidal gold–antibody probe for rapid detection of indomethacin (IDM) in water samples was developed. A positive reaction as a result of the remaining gold–antibody conjugate combining with antigen coated on the membrane was obvious by visual detection. Under optimal conditions, the visual detection limit was found to be 0.1 ng mL−1, which was about 10–1000 times lower than those in published literatures, demonstrating the high sensitivity of the assay. The stability test indicated the immunochromatographic strips could be used for 8 weeks at room temperature without significant loss of activity. Real water samples were detected by the assay and confirmed by enzyme-linked immunosorbent assay. The assay time for indomethacin detection was less than 10 min, suitable for rapid testing on-site.