Risk assessment of chlorpyrifos on rice and cabbage in China

Chlorpyrifos is a widely used organophosphorus insecticide in agricultural pest control. To understand the residue behavior of chlorpyrifos and to evaluate the dietary risk of chlorpyrifos residue in food in China, a number of residue studies were conducted on rice and cabbage. The supervised trial median residues (STMRs) for rice and cabbage were less than 0.010 and 0.227 mg kg⁻¹, respectively. Only 7.4% and 13.3% of acceptable daily intake (ADI) (0–0.01 mg kg⁻¹ bw) of chlorpyrifos is occupied by dietary daily intake to the Chinese adult and children, respectively, due to the consumption of rice and cabbage. These results on risk assessment were consistent with that of JMPR. Incorporation of market survey residue data gave a 5-fold reduction in the estimated exposures to chlorpyrifos. Concerning the acute exposure, the national estimated short-term intake (NESTI) represents 0.077% and 10.6% for rice and cabbage, respectively, of the acute reference dose (ARfD) (0–0.1 mg kg⁻¹ bw). The application of chlorpyrifos at the recommended dose on rice and cabbage is unlikely to pose any public health issues if it is applied according to the good agricultural practices (GAPs) established by each country.     

残根残冠的保存治疗与修复的临床效果分析

目的探讨残根残冠经根管治疗与冠修复后的临床治疗效果。方法选择2008～2010年在门诊收治的274颗残根残冠为研究对象,经根管治疗后行桩核冠修复,随访观察6个月～3年,分析其临床疗效。结果经6个月～3年随访,274颗患牙中244颗修复成功(89.1%),30颗牙失败(10.9%),其中16颗牙根出现不同程度的松动,8颗出现龈瘘,4颗因牙周炎拔牙,2颗核桩因继发龋脱落。结论在严格选择适应证的前提下,残根、残冠经完善根管治疗与冠修复后可达到满意的临床治疗效果。     

Dissipation of fuphenthiourea residues in rice and field ecosystem after seed soaking application

An analytical method with SPE or matrix solid-phase dispersion clean-up procedure on PSA followed by HPLC-DAD was established for determination of fuphenthiourea residues in rice, water and soil. At three concentration levels (0.05, 0.5 and 5 mg kg⁻¹), recoveries were in the range of 61.2-82.7%, with a RSD less than 13%. The LOQ of this method was 0.005, 0.02 and 0.01 mg kg⁻¹ for the water, soil and rice samples, respectively. Fuphenthiourea was applied in supervised ?eld trials at GAP conditions during rice seeding. It was found that under field conditions, the dissipation half-lives of fuphenthiourea were 0.8 d in the water and 24.8 d in the soil. At harvest, no detectable residues (<LOD) were found in the various samples.     

Analysis of Imazaquin in Soybeans by Solid-phase Extraction and High-performance Liquid Chromatography

An analytical method for the determination imazaquin residues in soybeans was developed. The developed liquid/liquid partition and strong anion exchange solid-phase extraction procedures provide the effective cleanup, removing the greatest number of sample matrix interferences. By optimizing mobile-phase pH water/acetonitrile conditions with phosphoric acid, using a C-18 reverse-phase chromatographic column and employing ultraviolet detection, excellent peak resolution was achieved. The combined cleanup and chromatographic method steps reported herein were sensitive and reliable for determining the imazaquin residues in soybean samples. This method is characterized by recovery >88.4%, precision <6.7% CV, and sensitivity of 0.005 ppm, in agreement with directives for method validation in residue analysis. Imazaquin residues in soybeans were further confirmed by high performance liquid chromatography-mass spectrometry (LC-MS). The proposed method was successfully applied to the analysis of imazaquin residues in soybean samples grown in an experimental field after treatments of imazaquin formulation.     

人体四肢正常动、静脉纵向残余应变与应力-应变关系

目的：探讨人体四肢正常动,静脉的纵向残余应变特性和应力－应变关系,以及对临床修复血管损伤时方法选择的影响。方法;以人体正常血管标本为研究对象,通过血管拉伸试验及检测血血管纵向伸长率,获取四肢正常的,动,静脉纵向残余应变及应力－应变变化规律。     

Analysis of uranium in the insoluble residues after decomposition of soil samples by various techniques

A comparison of different dissolution techniques for determination of uranium in soil samples was made. Conventional wet dissolution with mixtures of HNO₃, HClO₄ and HF acids, microwave dissolution using HNO₃ and HF, and alkaline fusion with Na₂CO₃ and Na₂O₂ were evaluated. For testing the effectiveness of the dissolution procedures, two reference materials and six soil samples from the surroundings of a former uranium mine were investigated. It was observed that the content of uranium in the residues determined by INAA represents a significant contribution to its total concentration in the sample, especially in the case of microwave dissolution.     

广州市售农产品中灭多威残留量的测定

目的:应用高效液相色谱法监测广州市售农产品中灭多威残留量并分析其存在的农药卫生问题.方法:采用高效液相色谱法,以C18色谱柱、以甲醇:水(V/V)=1:1混合液为流动相,用紫外检测器,在235nm波长下测定吸收值.结果:广州市售多种农产品中灭多威残留量,灭多威在市场来源样品中的检出率为42.86%,在超市来源样品中的检出率为33.33%,总样品检出率为37.50%,检出量为0.45～7.88 mg/kg.结论:选用方法精密、准确、回收率高;灭多威作为高毒杀虫剂,在广州市售农产品中的残留问题仍然比较严重.     

灭多威在土壤中降解规律的研究

本文对灭多威在土壤中的降解规律进行了研究。结果表明，灭多威在土壤中的降解符合动力学一级反应，按推荐量施药，灭多威在土壤中降解较迅速，降解半衰期为５．０４天，施药后第１５天，灭多成在土壤中的降解率为９７．７％，施药量与残留量呈正相关，相关系数为０．９９９８。提示：按推荐量施药，灭多成对土壤污染较轻。     

土壤中丙溴磷含量测定及残留动态研究

目的：弄清田间喷洒丙溴磷后在土壤中的残留及降解规律。方法：采用GC—FPD法测定田间喷洒丙溴磷后，不同天数丙溴磷在土壤中的残留量。结果：丙溴磷在土壤中的最低检出浓度为0．04mg／kg。加标回收率在95．2％--98．7％范围内，变异系数3．4％--4．5％。按推荐量施药，丙溴磷在土壤中降解符合一级动力学，半衰期为1．09d。施药后13d丙溴磷在土壤中降解率为98．3％。结论：测定方法简便、快速、准确、实用。丙溴磷在土壤中的降解较迅速，对土壤污染较轻。     

Sodium dehydroacetate levels in chicken tissues

Sodium dehydroacetate (Na-DHA), which has preservative and antimicrobial effects, is used as food and feed additive. However, there is little information on the Na-DHA levels in foods derived from animals fed Na-DHA. In this study, an HPLC-based method with methanol and 0.02% ammonium acetate (31:69, v/v) as the mobile phase was developed to determine Na-DHA residues in chicken muscle, liver, kidney, and skin fat tissues. Forty-eight yellow-plumage broiler chickens were administered 200 mg/kg Na-DHA in their feed for 30 d and sacrificed at different time points. In this study, the limit of detection was 0.08 mg/kg and the limit of quantification was 0.2 mg/kg. The residue concentration of Na-DHA in chicken tissues was <0.7 mg/kg. The elimination half-times of Na-DHA were 5.86 d for kidney tissues, 6.02 d for liver tissues, 8.88 d for muscle tissues, and 10.38 d for skin fat tissues. The residue levels of Na-DHA were lower than dehydroacetic acid in chicken tissues in our previous work, implying less risk of Na-DHA residue in chicken tissues compared to its acid.