Abstract:

A method for the determination of 14 sulfonamide residues in shrimps by high performance liquid chromatography coupled with post-column derivatization was established. The sulfonamide residues were extracted with ethyl acetate after adding sulfapyridine as internal standard. The extracts were vacuum-concentrated and reverse-extracted by 2 mol/L hydrochloric acid solution for clean-up, and then the hydrochloric acid solution was defatted with n-hexane. The solution after filtration was blended with a mixed solution of methanol, acetonitrile and 3.5 mol/L sodium acetate solution (5:5:20, v/v/v). The sulfonamides were separated on a C₁₈ column by RP-HPLC and on-line derivatized with a fluorescamine and detected with a fluorescence detector. The standard addition method was used for quantitative analysis. The parameters of post-column derivatization system, such as concentration of fluorescamine solution, velocity of reagent solution and reaction temperature, were optimized. The calibration curves of the method showed good linearity in the range of 5-200 μg/L. The limits of quantification (LOQ, S/N=10) were 1.0-5.0 μg/kg for the 14 sulfonamides. The recoveries were 77.8%-103.6% in the spiked range of 1.0-100.0 μg/kg in shrimps with the relative standard deviations of 2.9%-9.1% (n=6). The results indicated that the method is sensitive, efficient and more accurate. It is suitable for the simultaneous determination of the 14 sulfonamide residues in shrimps.

Key words: fluorescamine, fluorescence detection, high performance liquid chromatography (HPLC), post-column derivation, residues, shrimps, sulfonamides