Determination of 4 Sulfonamides in Environmental Water Samples by Capillary Electrophoresis Combined with Hollow Fiber Membrane Liquid Phase Microextraction

Water sample was centrifuged for 10 min at a rate of 3 000 r·min^-1, and the supernatant was taken and filtered surcessively through filters of 0.45 and 0.22 μm. Acidity of the filtrate was adjusted to pH 4.5 by addition of KH₂PO₄. The 4 sulfonamides in the filtrate were separated by hollow fiber membrane liquid phase microextraction under the following conditions:① extractant:n-octanol; ②acceptor phase:24 μL of 150 mmol·L^-1 NaOH solution; ③ donor phase:18 mL of pH 4.5 sample solution; ④ time of extraction:60 min; ⑤ stirring rate during extraction:300 r·min^-1, and determined by capillary electrophoresis under the following conditions:① operating voltage:20 kV; ② time and pressure of sample introduction:5 s, 3.447 kPa; ③ detection on cathodic side at the wavelength of 254 nm and temperature of 25℃; ④ buffer solution:30 mmol·L^-1 borax solution of pH 7.60. Linear relationships between values of peak area and mass concentration of the 4 sulfonamides were found in the same range of 5.0 to 1 000 μg·L^-1, with detection limits (3S/N) of 1.17 (SM₂), 0.84 (SM₁), 0.73 (SD) and 1.27 μg·L^-1 (SMZ), and enrichment factors between 105 and 393. In analysis of substantial samples by the proposed method, 2 sulfonamides were detected in aquaculture water and 1 sulfonamide was detected in domestic sewage. Values of recovery obtained by standard addition method were in the range of 82.3% to 99.4%, and RSDs (n=5) were in the range of 0.39%-6.6%.