HPLC-MS/MS Determination of 7 Disperse Dyes in Printing and Dyeing Wastewater with Separation by Bi-Aqueous Phase Extraction Using n-Propanol and Ammonium Sulfate as Extraction System

5.00 mL of the wastewater sample were taken and extracted ultrasonically for 21 min by bi-aqueous phase extraction with extractant system composed of 200 μL of n-propanol and 2.75 g of (NH₄)₂SO₄. After centrifuging for 5 min, 50 μL of the upper organic phase was taken and evaporated to dryness by N₂-blowing. The residue was dissolved with 100 μL of CH₃CN-H₂O (7+3) mixture, and the solution was then separated by HPLC using Zorbax Eclipse XDB-CN column as stationary phase and a mixture of 0.1% (φ) formic acid solution and acetonitrile (3+7) was used as mobile phase for elution. MS/MS with ESI, MRM was adopted for determination of the 7 disperse dyes. As shown by the results, linear relationships between values of peak area and mass concentration of the 7 disperse dyes were found in definite ranges, with detection limits (3S/N) in the range of 3.3-57 ng·L^-1. Test for recovery by standard addition method was made using wastewater from printing and dyeing process as matrix, giving results in the range of 80.0%-116%, and RSDs (n=5) ranged from 1.2% to 10%.