Comparison of gas chromatography and immunoassay methods in measuring the distribution of dieldrin in rainbow trout tissues.

Studies have been conducted to determine the distribution of dieldrin in various tissues of rainbow trout when exposed to several dieldrin concentrations. Medium sized fish with an average weight and length of 195.4 +/- 30.5 g and 25.7 +/- 1.4 cm, respectively, were placed in groups of 6 in 300 L tanks containing purified and aerated water and maintained at 10 degrees C. Following an acclimatization period of 10 days, each group of fish was exposed to one of four dieldrin concentrations ranging from 50 to 80 ppb. After 24 hours, the fish were taken out of the tanks and sacrificed. The brain, gills, liver, muscles and skin were collected from each fish. Dieldrin was extracted from each tissue using SPE techniques and analyzed by both gas chromatography (GC) and enzyme linked immunosorbent assay (ELISA). Results of analyses by the two techniques were highly correlated. The results also showed that liver and skin tissues had the highest level of dieldrin residues. In comparing the means of the six fish samples, it was found that liver or skin contained about 1.5-fold the level in brain, about 4.0 fold the level in muscles and about 6.5 fold the level in gills. Immunoassay proved to be as reliable an analytical tool as gas chromatography in this case.     

耕地质量监测中合理样本量配置及不确定性分析——以陕西省宝鸡市为例

耕地质量监测样本量的优化配置对降低成本,实现可持续土地资源监测与利用有重要指导价值。以陕西省宝鸡市为例,采用2018年耕地质量监测数据,运用传统统计学和地统计学方法,探讨耕地质量监测中土壤监测指标的合理样本量及不确定性。研究表明：样本变异性大小与样本量的关系并不是绝对的。样本代表性评价方法和地统计学方法较Cochran方法能有效降低样本的不确定性;样本代表性评价法适用性更广,但研究结果缺乏稳定性;地统计学方法的适用性存在局限性,可降低中等变异性指标的不确定性,但对低、高变异性指标适用性较低。中等变异性指标宜采用地统计学方法确定合理样本量;低、高变异性指标宜采用代表性评价方法确定合理样本量。     

DDT residues in Lebanese soils

The present study was conducted to evaluate the levels of residual DDT in Lebanese soils. A total of 113 surface soil samples were collected for analysis from three major agricultural regions in the country: Mount Lebanon, Beqa'a valley and the coastal plain. The values of residual DDT in soils ranged between 0 and 1190 ng g(-1). The majority of the analyzed soil samples were free or contained very low concentrations of DDE. Only two surface soil samples, which were collected from urban areas with high human activities, contained relatively high concentrations of residual DDT. The levels of residual DDT in all of the analyzed soil samples were within the permissible limits for agricultural soils.     

Comparison of gas chromatography and immunoassay methods for analysis of total DDT in calcareous soils

Three different calcareous soil samples from Lebanon were analyzed for total DDT pesticide residue using GC and ELISA methods. Two experiments were conducted on three different calcareous soil samples. In each experiment, triplicates of 5 gm soil samples were each fortified with standard solutions of DDE to reach concentrations of 0, 5, 25, 50, 100 and 200 ng g(-1) and allowed to equilibrate at room temperature for 6 hours. Each sample was then extracted with 25 mL of 90% methanol by shaking in glass bottles on a mechanical shaker for 16 hours. The bottles were allowed to stand for 30 minutes and aliquots were taken from the clear supernatant for analyses without further cleanup. The total DDT in the extract was measured in triplicate by GC and ELISA. The results indicated that the two methods were highly correlated (R = 0.955-0.994). Differences in soil properties did not affect the accuracy of the detection limits of ELISA. Immunoassay technique can be used for rapid and accurate measurement of total DDT residues in mineral calcareous soils in Lebanon.