Analysis of Organophosphorus Pesticides in Whole Milk by Solid Phase Microextraction Gas Chromatography Method

Solid phase microextraction (SPME) was used for the extraction of residual coumaphos and dichlorvos in whole milk. The residues were analyzed by capillary gas chromatography equipped with nitrogen phosphorus detector (GC-NPD). A manual SPME holder with a 100-μm polyacrylate fiber was used. The optimized conditions for extraction by SPME method were: sample agitation, absorption temperature of 30°C, absorption time of 40 min, desorption time of 10 min, and sample volume was 16.0 mL in the vial. Under these conditions, the calibration graphs were linear in the range of 0.17 μgL^?1 to 1.75 μgL^?1 for coumaphos and 0.69 μgL^?1 to 6.90 μgL^?1 for dichlorvos. Precision was good with RSD values of 13% for coumaphos and 14% for dichlorvos. The detection limits (LOD) were 0.060 μgL^?1 for dichlorvos and 0.052 for coumaphos. The quantification limits (LOQ) were 0.086 μgL^?1 for dichlorvos and 0.066 μgL^?1 for coumaphos. The results obtained in this study suggest that SPME is a suitable technique for residual pesticide analysis of milk. The data demonstrate that particular OP pesticides used in dairy farming in the region of Minas Gerais were found to contaminate cow whole milk, and the residues are not removed by treating the milk by boiling.     

利用某尾矿制备纳米SiO2

采用固相熔融法从尾矿中提取SiO2,利用超声辅助化学沉淀法制备纳米SiO2。分别研究了NaOH与尾矿质量比、反应温度、反应时间对SiO2提取率的影响,以及溶解水量、HCl浓度、终点pH、超声波功率和超声波频率对纳米SiO2性能的影响,研究表明,当NaOH与尾矿的质量比为1.4∶1,温度为325℃时灼烧25 min后用100 mL水溶解,滴加1.6 mol/LHCl酸化沉淀,终点pH调至8.5,在超声功率100 W,超声频率28 Hz的条件下,尾矿中SiO2提取率达到98.0%,产物中SiO2含量为98.40%,平均粒度为18 nm,得到的产品符合国家标准。     

Microwave/SPME method to quantify pesticide residues in tomato fruits

A new analytical method using focused microwave-assisted extraction (FMAE), coupled with solid phase micro-extraction (SPME), has been elaborated to determine 25 pesticides used in tomato cultivation. Microwave energy was used for a fast and controlled heating of solvent to selectively extract compounds. Calibration curves were plotted from blank tomato samples spiked at different concentrations with standards. A linear response was obtained between 10 and 1000 μ g/Kg for pyrethroids and between 0.1 and 5000 μ g/Kg for other compounds. For all studied substances, the resulting correlation coefficient (r²) was greater than 0.99. Limits of detection (LOD) and quantification (LOQ) were measured lower than 8 and 25 μ g/Kg, respectively. The relative standard deviation (RSD) was determined below 15% for all pesticides. Field incurred tomato samples were used to validate the new FMAE/SPME method. Observed analysis results by using this technique were in good agreement compared to those obtained by two accredited trading laboratories using traditional methods. Four tomato samples, bought in a local market, were also tested with the FMAE/SPME method.     

气液两相旋流喷嘴雾化特性

为提高烟尘净化用喷嘴的雾化性能,提出一种气液两相旋流喷嘴,用CFX软件对该喷嘴内部流场模拟的结果表明,强烈的气旋作用使液流呈环状,使气液混合流在达到喷嘴末端时易于破碎成雾。在实验室条件下,利用Winner313型喷雾激光粒度分析仪对喷嘴进行了雾化粒度测定,分析发现雾滴中位径与气液比的关系呈幂函数衰减,这一规律将有助于在工程应用时确定喷嘴工况。     

SMBR内气液两相流三维CFD模拟

应用CFD软件Fluent对浸没式膜生物反应器(submerged membrane bioreactor,SMBR)内气液两相流进行数值模拟研究,重点考查曝气系统的改变对气液两相流态的影响,并结合PIV实验验证模拟结果,从而为反应器的优化设计及膜污染的控制提供理论依据。模拟结果表明,SMBR内曝气强化了气液两相紊动,膜表面液相速度沿反应器高度增加且形成循环流动,有利于膜面污染物的脱落;反应器内气含率分布不均匀,出现死区,不利于微生物的生长;经实验验证,模拟结果吻合良好。     

SO42-/SnO2 -Fe2O3-硅藻土固体酸催化剂的制备及其对染料废水的催化处理

以硅藻土为载体,采用溶胶-凝胶法引入金属氧化物SnO₂和Fe₂O₃,制备了二元氧化物复合型SO₄^2-/SnO₂-Fe₂O₃-硅藻土固体酸催化剂。利用该催化剂与H₂O₂构成非均相类Fenton试剂氧化体系,催化H₂O₂产生氧化能力极强的·OH,用于处理实际翠蓝废水和模拟亚甲基蓝废水。催化剂的最佳制备条件为：H₂SO₄溶液的浓度3 mol/L,浸渍时间2.0 h,焙烧温度550 ℃,焙烧时间3.5 h,焙烧方式为随炉升降温。实验结果表明：采用在最佳工艺条件下制得的催化剂,处理实际翠蓝废水COD去除率可达79.5%、脱色率达99.6%;处理模拟亚甲基蓝废水COD去除率可达83.1%、脱色率达99.6%。     

甲苯在典型土壤中的迁移性能

采用一维土柱装置模拟非水相液体(NAPLs)在我国两种典型土壤(北京潮土与湖南红壤)中的垂向迁移过程,以甲苯为例研究了其在两种土壤中的迁移性能;采用XRD技术测定土壤的矿物组成。实验结果表明,当潮土和红壤孔隙率均为45%时,甲苯在潮土中的迁移速率和最终迁移距离均显著高于在红壤中。甲苯在潮土中的阻滞系数(Rf=18.9)小于在红壤中(Rf=26.5),表明红壤对甲苯的吸附阻滞作用强于潮土。XRD表征结果显示,红壤中粒径小的黏粒含量较高,具有较多的黏土矿物,对甲苯具有更强的吸附阻滞能力,致使甲苯在红壤中垂向迁移速率小,最终迁移距离较短。     

我国营养体产业发展及种植业结构调整

本文根据我国气候的基本特征,提出了发展营养体产业是高效利用我国土地资源和气候资源的有效途径的观点,比较了营养体产业和传统农业在光能利用和产量等方面的差别,指出了营养体产业和技术关键是科学利用Ｓ－型生长曲线。     

基于磁性多壁碳纳米管的涡旋辅助分散基质固相萃取-高效液相色谱检测水中双酚A

针对分散基质固相萃取中吸附剂与液相难以彻底分离等问题,合成磁性多壁碳纳米管作为吸附剂,结合液相色谱检测,建立了基于涡旋辅助磁性分散基质固相萃取检测水中双酚A的分析方法。磁性多壁碳纳米管与液相可以实现简便、彻底的分离,省略分散基质固相萃取中的过滤或离心步骤。在优化条件下,方法检出限为0.02μg/L,线性范围为0.05~10μg/L(r=0.999 2)。将该方法用于实际水样的分析,相对回收率为89.6%。     

高效液相色谱法测定地下水中洛克沙胂

地下水水样经磷酸二氢钾提取后,用MAX固相萃取小柱对其净化、浓缩,再用高效液相色谱仪测定样品中的洛克沙胂。对色谱条件进行优化,使该方法在0.500 mg/L~10.0 mg/L范围内线性良好,方法检出限为0.047μg/L。空白加标样6次测定结果的RSD为5.3%,空白水样的3个质量浓度水平的加标回收率为79.8%~88.8%。将该方法用于测定6个地下水实际样品中洛克沙胂,其中1个被检出,测定值为0.42μg/L。