取鱼塘水样4 L于5 000 mL烧瓶中，加入混合内标溶液[含0.5 mg·L^-1普罗迪芬盐酸盐（SKF525A）和2 mg·L^-1苯巴比妥]100 μL。另取由4种常用填料C₈、C₁₈、GDX403及X-5，按1：2：1：8的质量比混合组成的新型吸附剂6 g，置于甲醇10 mL中浸泡活化并过滤，将经活化的吸附剂加入于上述水样中，于振摇器上振荡1 h，经减压过滤，在所收集的固相吸附剂（包括其所吸附的农药）以及滤纸中，加入无水硫酸镁5 g和苯及乙酸乙酯各100 mL，振荡萃取10 min，通过1.0 μm滤膜过滤，取滤液并吹氮蒸发至近干，用甲醇溶解残渣并定容其体积为1.0 mL。将此溶液通过0.22 μm滤膜过滤，取滤液按所选择仪器工作条件进行超高效液相色谱-串联质谱法（UPLC-MS/MS）分析。上述预富集中所用新型吸附剂对所测定的常见农药进行固相萃取富集时，各农药中有11种的回收率大于90.0%，全部试验农药的平均回收率达82.0%。色谱分离中，选用IntertSustain C₁₈柱为固定相，以不同比例的（A）0.1%（体积分数）甲酸的20 mmol·L^-1乙酸铵溶液，或（A'）不加甲酸的20 mmol·L^-1乙酸铵溶液，和（B）乙腈或（B'）甲醇的混合液作为流动相，按3种不同的程序进行洗脱。在此条件下，所测定的农药和2种内标的保留时间在0.53~9.81 min之间。在质谱分析中，选择正、负离子2种电离模式和多反应监测（MRM）模式进行测定，用内标法定量。所测农药中17种农药的线性范围在0.005~0.5 μg·L^-1之间，其余4种农药的线性范围在0.01~0.5 μg·L^-1之间，检出限（3S/N）为1~5 ng·L^-1之间。以加标方法进行准确度试验，根据测得质量浓度和理论质量浓度的比值得到的结果在92.5%~106%之间，测定值的相对标准偏差（n=6）为1.3%~9.7%（日内）和2.5%~13%之间（日间）。

Four liters of fish-pond water sample were collected and placed into a 5 000 mL flask, and 100 μL of mixed internal standard solution (containing 0.5 mg·L^-1 of SKF525A and 2 mg·L^-1 of phenobarbital) were added. A mixture of 4 fillers, namely C₈, C₁₈, GDX403 and X-5, was prepared by mixing the 4 compounds by the mass ratio of 1:2:1:8, and 6 g of the mixture were taken and activated by soaking in 10 mL of methanol. After filtration, the activated mixed filler was added to the sample solution as adsorbent, and the mixture was shaked for 1 h with a shaker. After filtration, the solid adsorbent with the adsorbed pesticides and together with the filter paper was taken and extracted by shaking for 10 min with 100 mL each of benzene and ethyl acetate after adding 5 g of anhydrous magnesium sulfate. The mixture was then filtered through 1.0 μm filtering membrane. The filtrate was collected and evaporated to near-dryness by N₂-blowing. The residue was taken up and made its volume to 1.0 mL with methanol. The solution was filtered through 0.22 μm filtering membrane, and the filtrate was used for UPLC-MS/MS analysis under the optimized instrumental conditions. The use of mixture of the 4 filler as the adsorbent for enrichment of the pesticides improved the separation by giving an average recovery of 82% for the pesticides determined with averages above 90.0% for 11 pesticides. In the UPLC separation, InertSustain C₁₈ column was used as stationary phase, and 3 elution programmes were adopted using mixtures of (A) 20 mmol·L^-1 ammonium acetate solution containing 0.1% (volume fraction) formic acid of (A') 20 mmol·L^-1 ammonium acetate solution (without formic acid) and (B) acetonitrile of (B') methanol in various ratios as mobile phases. Under the prescribed elution programmes, retention times for the 21 pesticides together with the 2 internal standards were found in the range from 0.53 to 9.81 min. In MS/MS analysis, ESI with positive and negative ion modes and MRM mode were adopted. Internal standard method was used for quantification. Linearity ranges found were in the ranges from 0.005-0.5 μg·L^-1 for 17 among the 21 pesticides, and from 0.01-0.5 μg·L^-1 for the remainder. Dection limits (3S/N) found were in the range of 1-5 ng·L^-1. Test for accurary was made by standard addition method, giving results in the range of 92.5%-106% according to the ratio between determined mass concentration and the theoretical mass concentration. Values of RSDs (n=6) found were ranged from 1.3%-9.7% (intra day) and from 2.5%-13% (inter day).