Determination of Steroids in Milk Powder and Birds'' Feces by High Performance Liquid Chromatography Coupled with Evaporative Light Scattering Detector
高效液相色谱/挥发激光散射检测器测定奶粉和鸟粪中的甾体化合物

In this paper, a new, simple and rapid method for the analysis of steroids by reversed-phase high performance liquid chromatography (HPLC) coupled with evaporative light scattering detector (ELSD) is presented. A good resolution of the 12 steroids is obtained within 35 min with a gradient elution using a binary mobile phase composed of methanol and water. The analytical column used was 2.0mm x 150mm, packed with BDS (particle size 5microm) and the mobile phase flow rate was 0.2mL/min. Nebulizer gas flow rate and drift tube temperature, the two critical parameters for determining the reproducibility and signal-to-noise ratio of ELSD were 2.00mL/min and 95 degrees C, respectively. The response of the ELSD was non-linear as a result of basic light-scattering principles, the calibration curve by plotting lnY vs lnX (Y, X stand for peak area and concentration, respectively) shows a good linearity in the range of 5-50mg/L with a correlation coefficient higher than 0.99 for individual steroid and with relative standard deviation less than 6.92%. This method has been applied to the determination of steroids in milk powder and birds' feces, solid phase extraction on reverse phase bonded C18 (5mL/500mg) was used to treat the samples efficiently. The recoveries of the steroids were between 84.0%-102.8%.