Abstract:
Sulfonamides (SAs) are frequently used as feed additives to prevent and treat animal diseases because of their low cost, high stability and strong hydrophilicity. However, the incomplete adsorption of SAs in the living body makes them excreted in the form of derived products or original structures. These excrements can bring serious pollution in soil when being used as manures. Therefore, more and more attention has been paid for the detection of antibiotics in organic fertilizer in recent years. In this study, a method for the simultaneous determination of 14 kinds of sulfonamide antibiotics in organic fertilizers by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed. The samples were purified and concentrated by MCX solid phase extraction column after mixing with extraction solution. Methanol, ammonium acetate (10 mmol/L) and formic acid aqueous solution (0.1%, mass fraction) were used as mobile phases. The samples after pretreatment were separated by gradient elution and analyzed qualitatively under UHPLC-MS/MS multi-reaction monitoring mode. The effects of different kinds of extraction solvents on extraction efficiency during pretreatment were compared. When acetonitrile/acetic acid (volume ratio: 80/20) was used as the extraction solvents, the average recovery of 14 sulfonamide antibiotics was 53.78%—90.29%. Box-Behnken design, a kind of responsive surface methodology, was used to optimize the three parameters of buffer volume, buffer pH and oscillation time to enhance the average recovery of 14 sulfonamide antibiotics. Under the optimal extraction conditions (6.15 mL Na
2EDTA-Mcllvaline buffer, pH 3.0 and 20 min of the oscillation time), the average recovery of 14 antibiotics was 69.31%—76.39%. The relative standard deviation (RSD) of the optimized pretreatment method was less than 3.04%, which indicated that the method had good reproducibility and could be applied to the determination and analysis of actual samples.