取污染区沉积物，除去其中的异杂物后充分混匀。称取混匀样品10.00 g，加入适量经过在400℃烘烤4 h的无水硫酸钠并充分混合拌匀，研磨成细粒状。将此样品全部装入滤纸套筒中，并置于索氏提取器中，加入体积比为1：1的正己烷-丙酮混合溶液250 mL，在回流速率为10次·h^-1条件下提取8~12 h （一般可采取多个样品同时提取过夜的操作方式）。收集所有提取液，混匀后将经活化处理的铜片置于此提取液中4~6 h除去硫化物。过滤除去沉淀，滤液浓缩后经以硅酸镁为载体的固相萃取柱净化。用体积比为9：1的正己烷-丙酮混合溶液15 mL洗脱固相萃取柱，收集洗脱液经浓缩至1.0 mL后，供色谱分离及测定。在此测定溶液中存在20种有机氯农药（OCPs）及7种多氯联苯（PCBs）共27种化合物。待测物在非极性一维TG-35MS色谱柱上按其沸点规律分离后，流出液经调制器聚焦后迅速升温（调制周期为4 s）并送入极性二维DB-1色谱柱按被测物的极性差异分离。两柱的组合达到上述27种化合物的良好分离。采用电子捕获检测器对27种化合物进行检测。上述27种化合物的质量浓度均在1.0~200.0 μg·L^-1内与其对应的峰面积之间呈线性关系，其检出限（3.14s）为0.017~0.087 μg·kg^-1。按标准加入法进行回收试验，测得回收率为72.0%~96.3%，测定值的相对标准偏差（n=6）为2.1%~11%。

Sediment from riverbank of polluted area was collected and after picking out those impurities (i.e. branches, leaves, stones etc.) which were mixed up in, it was mixed thoroughly and ready to be used as analytical sample. 10.00 g of the sample were taken and mixed thoroughly with an appropriate amount of anhydrous Na₂SO₄, which has been baked at 400℃ for 4 h beforehand, and then ground to fine powdery state. The powder mixture was loaded completely into a sleeve made of filter paper, and the sleeve was replaced into the Soxhlet extractor, and extracted with 250 mL of a mixed solution of n-hexane and acetone with the volume ratio of 1:1 for 8-12 h at a refluxing rate of 10 times perhour (the authors propose to arrange the soxhlet extraction overnight in batches, by automation). The extracts were collected, combined and mixed thoroughly. A pre-activated copper sheet was placed into the combined extract for 4-6 h to eliminate sulfide by precipitation of sulfide on the copper sheet. The solution mixture was then filtered, and the filtrate was concentrated to a smaller volume and purified by passing through SPE column packed with Florisil. The analytes were adsorbed on SPE column and were eluted from the column by 15 mL of a mixed solution of n-hexane and acetone with the volume ratio of 9:1. The eluate was collected and evaporated to a definite volume 1.0 mL in which 27 compounds[i.e. 20 organochlorine pesticides (OCPs) and 7 polychloro-biphenyls (PCBs)] were contained and be further separated and determined with ECD. In the 2-dimensional gas chromatography separation, 2 chromatographic columns, i.e. the non-polar column (TG-35MS, the 1 st D) and the polar column (DB-1, the 2nd D) were used in combination. Among the 27 compounds, non-polar compounds were separated according to their differences in boiling points on the 1st D-column; the eluate from which was modulated by focusing to elevate its temperature rapidly (with gap of modulation of 4 s) and introduced into 2nd D-column through which the analysts with differences in polarities were separated. Good separation of the 27 compounds was attained by this arrangement. Linear relationships between values of mass concentration of the 27 compounds and their respective peak areas were found in the same range of 1.0-200.0 μg·L^-1; with their detection limits (3.14 s) in the range of 0.017-0.087 μg·kg^-1. Test for recovery was made by standard addition method, the results of recovery were found ranged from 72.0% to 96.3%, and values of RSDs (n=6) were found in the range from 2.1% to 11%.