Development of indirect competitive ELISA for detection of fluoroquinolone residues

To develop a multidetermination immunoassay for fluoroquinolone(FQs) residues,an indirect competitive ELISA was developed with the polyclonal antibody against ciprofloxacin(CPFX pAb) produced from rabbits which immunized with FQs conjugated BSA.This method was sensitive and had a linear detection range from 0.2 ng/mL to 376 ng/mL(R2=0.943),with IC50 and LOD values of 8 ng/mL and 0.1 ng/mL.The antibody exhibited high sensitivity to FQs,and the IC50 values to enrofloxacin,norfloxacin and pefloxacin were 7.3 ng/mL,10.6 ng/mL,and 13.2 ng/mL,respectively.The optimized detecting condition indicated that the concentrations of NaOH and methanol in dilute solution was less than 10% and 30%.When the ciprofloxacin,enrofloxacin,norfloxacin and pefloxacin in milk were at highest concentrations of 5 ng/mL,20 ng/mL and 50 ng/mL,the recoveries were ranged from 93% to 108%,96% to 110%,92.5% to 104%,and 93% to 102%,respectively.