蔬菜样品被切成小段,分取10.00 g,和10 mL乙腈涡旋混合1 min。加入4.0 g无水硫酸镁和1.0 g氯化钠,涡旋振荡1 min,离心5 min。分取上清液1 mL,分别加入100 mg无水硫酸镁、75 mg C₁₈,涡旋1 min,离心2 min。上清液过0.22 μm滤膜,滤液流经高效液相色谱仪,在ZORBAX SB-C₁₈色谱柱上以体积比45∶55的乙腈-水体系进行等度洗脱。结果显示:除虫脲和灭幼脲的质量浓度均在0.1~5.0 mg·L^-1内与其对应的峰面积呈线性关系,检出限(3S/N)分别为0.007,0.02 mg·kg^-1;对混合标准溶液进行6次重复测定和6 d连续测定,除虫脲和灭幼脲峰面积的相对标准偏差分别为0.83%,1.6%(日内精密度试验)和2.5%,1.8%(日间精密度试验);以结球甘蓝、菠菜、花椰菜为基质进行3个浓度水平的加标回收试验,回收率为87.4%~104%和75.3%~98.1%。方法用于以上3种共15份蔬菜样品的分析,仅在1个花椰菜样品中检出了除虫脲,检出量(0.014 mg·kg^-1)低于相关国家标准规定的残留限量(1 mg·kg^-1)。

After the vegetable samples were cut into small pieces, an aliquot (10.00 g) was taken and mixed with 10 mL of acetonitrile by swirling for 1 min. Anhydrous magnesium sulfate (4.0 g) and sodium chloride (1.0 g) were added, the mixture was whirled for 1 min, and centrifuged for 5 min. An aliquot (1 mL) of the supernatant was taken, and 100 mg of anhydrous magnesium sulfate together with 75 mg of C₁₈ was added, respectively. After whirling for 1 min and centrifuging for 2 min, the supernatant was passed through a 0.22 μ m filter membrane. The filtrate was introduced into high performance liquid chromatograph, and targets were separated on ZORBAX SB-C₁₈ column with acetonitrile-water system at volume ratio of 45:55 under isocratic elution. As shown by the results, the mass concentrations of diflubenzuron and chlorbenzuron were linearly related with their corresponding peak areas in the range of 0.1-5.0 mg·L^-1, with detection limits (3S/N) of 0.007, 0.02 mg·kg^-1, respectively. Six repeated determinations and 6 d continuous determinations on the mixed standard solution were made, and RSDs of the peak areas of diflubenzuron and chlorbenzuron were 0.83%, 1.6% (for intra-day precision test) and 2.5%, 1.8% (for inter-day precision test), respectively. Test for the spiked recovery was made at the 3 concentration levels with cabbage, spinach and cauliflower as matrices, giving recoveries in the range of 87.4%-104% and 75.3%-98.1%. The proposed method was applied to the analysis of 15 samples of three kinds of vegetables, and diflubenzuron was detected in one cauliflower sample, and the detection amount (0.014 mg·kg^-1) was lower than the residue limit (1 mg·kg^-1) stipulated in relevant national standards.