Determination Of Sulfonamide Residues In Milk By High Performance Liquid Chromatography-Chemiluminescence Method

Sulfonamides (SAs), such as sulfaguanidine (SGD), sulfadiazine (SDZ), sulfathiazole (STZ) and sulfamethazine (SMZ), can drastically inhibit the chemiluminescence (CL) intensities generated in both Ag(III)-Luminol and Ni(IV)-Luminol systems. Based on these observations, a novel method of high performance liquid chromatography (HPLC) coupled with CL detection was established. Both the Ag(III)-Luminol and Ni(IV)-Luminol CL systems were employed as detectors, and the performances of the two detecting systems were compared. After separated by HPLC, four SAs reacted with Ag(III)-Luminol and Ni(IV)-Luminol CL system, respectively. Chromatographic conditions were as follows: reversed. phase C-18 column (250 mm. 4.6 mm, 5 mu m), gradient elution, and 0.1% (V/V) formic acid. methanol as mobile phase with flow rate of 1 mL/min. CL conditions were as follows: [Ag(III)] = 1.4 x 10(-4) mol/L (in 0.12 mol/L NaOH); [Ni(IV)] = 1.5 x 10(-5) mol/L (in 0.12 mol/L NaOH); [Luminol] = 1.2 x 10(-7) mol/L; and flow rate = 1.0 mL/min. Under the optimal conditions, the detection limits of Ag(III) Luminol CL system were 0.15, 0.96, 1.10, 1.50 mu g/mL for SGD, SDZ, STZ, and SMZ, respectively, and the recovery were 81. 0% - 101. 5%. Comparatively, the detection limits of Ni(IV) Luminol CL system were 1.5, 17.2, 16.8 mu g/mL for SGD, SDZ and STZ, and the recoveries was 83.9% - 110.8%. The result showed that the Ag(III) Luminol CL system had a much better performance. The method was applied to the determination of the residues of the above four SAs in milk with satisfactory results.