Chemiluminescent Detection of Gatifloxacin Residue in Milk

Abstract

An indirect competitive chemiluminescent enzyme-linked immunosorbent assay (CL-ELISA) for detection of gatifloxacin residue in milk was developed in this study. Compared with conventional colorimetric ELISA using the same antibody, the developed CL immunoassay shows a significant improvement in sensitivity and detectability with an IC₅₀ of 0.4 ng mL⁻¹ and a detection limit of 0.001 ng mL⁻¹ and thus is suitable to be used as a highly sensitive screening method to detect and regulate illegal use of gatifloxacin in food and food products. The test kit was applied to detect milk samples spiked by gatifloxacin, and satisfactory results were obtained.

Keywords:

• Antibody
• chemiluminesence
• drug residue
• gatifloxacin
• immunoassay

Acknowledgments

This research was supported by the National Natural Science Foundation of China (No. 20675048), National High-Tech Research and Developmental Program of China (863 Program, Nos. 07AA10Z435 and 2007AA06A407), and National Basic Research Program of China (973 Program, No. 2007CB936602).

Notes

^a IC₅₀ value (ng mL⁻¹) was a competitor concentration where the chemiluminescent intensity was decreased in half as compared to that of the absorbance value of no competitor.

^b Cross-reactivity was determined by comparing the concentration of an analyte required to produce B/B ₀ = 50%. Results were expressed as a percentage relative to the figure for gatifloxacin.

^a Interassay variation was determined by five replicates on five different days.

^b Intra-assay variation was determined by five replicates on a single day.

^c LC-MS variation was determined by five replicates on three different days.

^d RR represents recovery rate.