Dual signal insight: field-efficient qualitative/quantitative detection of sulphamethazine in raw milk

Abstract

A novel lateral flow assay (LFA) was developed by introducing magnetic beads with colloidal gold nanoparticles (AuMB) to LFA test strips for the qualitative and quantitative detection of sulphamethazine (SM2) in raw milk. In the proposed assay, test samples are qualitatively judged yes (positive) or no (negative) on the basis of naked-eye signals from the colloidal gold and fluorescence quenching is used to quantitatively determine the level of SM2 in positive samples. Results indicated that the threshold concentration for determining whether a test sample is positive or negative is 5 ng/mL. The limit of detection and linear range of the proposed AuMB–LFA for quantitative detection were 0.39 and 0.5–200 ng/mL, respectively, and its recovery for detecting SM2 in raw milk was 97.4–110.2%. The developed AuMB–LFA provides novel insights into efforts to maintain a balance between the efficient screening of targets in large samples and saving time and money.