Simultaneous detection of ofloxacin and lomefloxacin in milk by visualized microplate array.

Analytical method for simultaneous detection of ofloxacin and lomefloxacin in milk by visualized microarray immunoassay without the need of time-consuming or complex pre-treatment steps was reported. A 96-well microplate was used as solid support, in which ofloxacin antigen and lomefloxacin antigen were immobilized, respectively. After immobilization, a mixture of standard solutions containing the analytes or samples and relevant antibodies were added to the array reaction areas, then added silver nanoparticles (AgNPs) labeled secondary antibody (goat anti-mouse IgG). Silver enhancement technique was applied to amplify the detection signals, which produced black image on array spots visible with naked eyes. The signals were detected with a microarray scanner; therefore the analyte residues could detect quantitatively by standard calibration curve. Ofloxacin and lomefloxacin dynamic range were all from 0.05 ng/mL to 12.8 ng/mL. The calibration curve of ofloxacin was calculated as: y = − 0.3446x + 0.4287, r = 0.9849. The calibration curve of lomefloxacin was calculated as: y = − 0.3055x + 0.4797, r = 0.9927. The spike recovery were within 80–130%, and RSD were less than 15%. The limits of detection (LOD) were estimated to be 0.24 ng/mL (ofloxacin) and 0.35 ng/mL (lomefloxacin) (n = 3, 3SD). [ABSTRACT FROM AUTHOR]