离子色谱法测定磷石膏中水溶性氟离子和氯离子

为更好的满足磷石膏综合利用对高效分析手段的需要，采用离子色谱法测定磷石膏中水溶性氟离子与氯离子含量。与传统方法相比，方法操作简便，测定结果一致。对方法进行了验证，得出水溶性氟离子方法检出限为0.0004%、精密度为5.3%,氯离子方法检出限为0.0002%、精密度为6.4%,加标回收率均在80%～100%之间。方法的检出限低、准确度高，可供检测一线参考。     

高效液相色谱法同时测定克百威、福美双和萎锈灵

目的:建立高效液相色谱法同时测定克百威、福美双和萎锈灵的含量。方法:试样用甲醇溶解,采用等度洗脱的方法,以甲醇-乙腈-水为流动相,同时对萎锈灵、克百威和福美双进行分离,外标法定量。结果:测定克百威的方法线性相关系数为0.9997,变异系数为1.34%,平均回收率为100.7%;测定福美双的方法线性相关系数为0.9998,变异系数为1.50%,平均回收率为99.4%;测定萎锈灵的方法线性相关系数为0.9998,变异系数为1.42%,平均回收率为101.2%。结论:方法满足农药产品含量分析的要求,可同时测定克百威、福美双和萎锈灵的含量。     

氟离子选择电极法测定土壤中水溶性氟化物和总氟化物含量

采用氟离子选择电极法测定土壤中水溶性氟化物和总氟化物。结果表明,氟化物含量在5～500μg范围内具有良好的线性关系(>0.999),水溶性氟化物方法检出限为0.5 mg/kg,相对标准偏差(RSD,n=6)为3.8%～6.7%,总氟化物方法检出限为43 mg/kg,相对标准偏差(RSD,n=6)为4.0%～4.2%,满足标准方法的测定要求。有证标准物质RMU044和RMU045测定结果均在标准范围内,水溶性氟化物相对误差为-3.3%～-2.4%,相对标准偏差为4.0%～4.7%,总氟化物相对误差为0.9%～1.3%,相对标准偏差为1.0%～2.2%。实际样品加标回收率试验时,水溶性氟化物平均加标回收率为100%,总氟化物的平均加标回收率为94%,该实验方法重现性好,准确度高,操作简单。     

30%噻嗪·毒死蜱水乳剂的高效液相色谱分析

采用ODS2–C18反相色谱柱,用高效液相色谱外标法测定30%噻嗪·毒死蜱水乳剂含量。噻嗪酮方法的相关系数为0.9998,标准偏差为0.1075,变异系数为1.74%,平均回收率为99.8%;毒死蜱方法的相关系数为0.9998,标准偏差为0.1817,变异系数为0.75%,平均回收率为99.6%。     

碳纤维水洗液中碳酸氢铵的测定方法研究

优选了碳纤维水洗液中碳酸氢铵含量的检测波长,建立了碳纤维水洗液中碳酸氢铵的紫外分光光度检测方法。样品以水为溶剂,以207 nm为紫外检测波长,采用外标法定量。检测结果显示:在0.15%～1.5%时具有良好的线性关系,相关系数(r)为0.999 7。最低检出限LOD为0.093%,定量检出限LOQ为0.115%。该方法回收率为99.8%～104.8%,RSD为2.208%～3.606%。该方法简便、快速,能满足碳纤维水洗液中碳酸氢铵的测定要求。     

土壤中邻苯基苯酚含量的测定

建立使用加压萃取-气相色谱/质谱联用仪测定土壤中邻苯基苯酚含量的方法。邻苯基苯酚经过冻干、萃取、净化、浓缩、定容,气相色谱分离、质谱检测。研究结果显示:该方法对邻苯基苯酚的线性范围为0.5～20μg/mL,相关系数为0.9995,检出限为0.003 mg/kg;空白基底加标回收率为79.0%～96.4%,标准偏差为3.2%～5.1%;基体加标回收率为75.2%～93.1%,标准偏差为1.6%～4.5%。该方法准确、高效,可满足土壤中邻苯基苯酚的检测要求。     

一种快速测定土壤中重金属元素的方法确认

通过优化试验的关键步骤得到一种快速准确测定土壤中重金属元素铬、铅、镍、铜、锌的方法,对该方法进行确认。结果表明：采用该方法测定重金属元素的检出限为1.40～7.30 mg/kg,精密度为1.64%～5.10%,低浓度平均加标回收率为91.2%～106.4%,高浓度平均加标回收率为93.9%～108.6%。该方法检测效率高、精密度好、检出限低、回收率高,可用于土壤中重金属污染的监控与快速溯源。     

SPE-GC-MS联用测定饮料中尿烷

采用固相萃取法对多种饮料中尿烷进行定量分析。结果表明该方法测得尿烷的回收率为平均回收率为92.0%～104%,方法精密度为0.92%,相对标准偏差RSD为1.9%,检出限为2.5 g/L。该测定方法灵敏度高,准确度好,可用于质量控制。     

吡蚜酮在水稻植株、大米和土壤中残留量的测定方法研究

建立了吡蚜酮在水稻植株、大米和土壤中残留量的液相色谱定量检测方法。样品经乙腈提取,过SPE C18小柱净化,高效液相色谱(UV)测定,吡蚜酮的最小检测量为5×10-10 g,在植株、大米和土壤中最低检出浓度均为0.05 mg/kg。水稻植株中吡蚜酮的添加回收率为88.76%～103.9%,变异系数为7.63%～9.29%;大米中吡蚜酮的添加回收率为90.49%～91.38%,变异系数为3.43%～4.62%;土壤中吡蚜酮的添加回收率为90.24%～91.40%,变异系数为3.32%～5.15%。方法的线性范围在0.05～10 mg/L,方程y=4533.7 x+15302,相关系数0.9984。该方法的准确度和灵敏度均符合农药残留的分析要求。     

气相色谱法测定甲烷的方法研究

建立了毛细管气相色谱测定甲烷的方法:采用毛细管柱恒温测定,氢火焰离子化检测器(FID)检测甲烷气体的含量。结果表明:低浓度甲烷的线性范围分别为0.00100%～0.0201%,高浓度甲烷的线性范围分别为0.0201%～2.01%;低浓度甲烷回收率为91.0%～103%,高浓度甲烷回收率为98.1%～108%;低浓度甲烷RSD为2.07%～5.71%,高浓度甲烷RSD为1.16%～5.34%。该方法迅速简便,适用于甲烷气体的测定。     

Numerical determination of fluid-to-particle mass and heat transfer coefficients in packed bed reactors

A method based on particle-resolved CFD is built and validated, to calculate the fluid-to-particle mass and heat transfer coefficients in packed beds of spheres with different tube-to-particle diameter ratios (N) and of various particle shapes with N = 5.23. This method is characterized by considering axial dispersion. The mass and heat transfer coefficients increase by 5%–57% and 9%–63% after considering axial dispersion, indicating axial dispersion should be included in the method. The mass and heat transfer coefficients are reduced as N decreases. The catalyst particles without inner holes show higher mass and heat transfer coefficients than the ones with inner holes, because of unfavorable fluid flow in inner holes. The bed of trilobes has the highest mass and heat transfer coefficients, being 85% and 95% higher than the one of spheres. This work provides a versatile method and some useful guidance for the design of packed bed reactors.     

Gas permeability of copolypeptide membranes composed of γ-methyl L-glutamate and γ-benzyl L-glutamate

Membranes of copoly(γ-methyl L -glutamate, γ-benzyl L -glutamate) (PMBLG) as well as the related homopolymer membranes were prepared, and permeabilities of oxygen, nitrogen, argon, and carbon dioxide were measured in the 0–70°C temperature range. The values of permeability coefficients and solubility coefficients of the copolymers were smaller than those of permeability coefficients and solubility coefficients of the two homopolymers for every gas studied. The diffusion coefficients of the gases showed a minimum at around 25 mole % benzyl glutamate. The temperature at a maximum of tan δ spectra for the membranes showed a maximum at around 25 mole % benzyl glutamate. The Arrhenius plots of diffusion coefficients and solubility coefficients for PMBLG, which contained 50 and 71 mole % benzyl glutamate, showed a break at about 50 and 40°C, respectively. This permeation behavior is explained by assuming a unique interaction between methyl glutamate and benzyl glutamate side chains.     

非共沸混合物微通道内流动沸腾特性

引言 近30年来,工程技术的发展正朝微型化迈进,微型结构冷却技术在微电子、航天航空、生物医药和微型换热器等高新技术领域得到越来越多应用,由于沸腾换热是一种高强度的换热方式,微型通道内的流动沸腾换热特征的研究变得越来越重要.     

Influence of nanoparticle concentrations on flow boiling heat transfer coefficients of Al2O3/R141b in micro heat exchanger by direct metal laser sintering

Al2O3/R141b+Span-80 nanorefrigerant for 0.05 wt.% to 0.4 wt.% is prepared by ultrasonic vibration to investi-gate the influence of nanoparticle concentrations on flow boiling heat transfer of Al2O3/R141b+Span-80 in micro heat exchanger by direct metal laser sintering.Experimental results show that nanoparticle concentrations have significantly impact on heat transfer coefficients by homogeneity test of variances according to mathemat-ical statistics.The heat transfer performance of Al2O3/R141b+Span-80 nanorefrigerant is enhanced after adding nanoparticles in the pure refrigerant R141b.The heat transfer coefficients of 0.05 wt.%,0.1 wt.%,0.2 wt.%,0.3 wt.% and 0.4 wt.% Al2O3/R141b+Span-80 nanorefrigerant respectively increase by 55.0%,72.0%,53.0%,42.3% and 39.9% compared with the pure refrigerant R141b.The particle fluxes from viscosity gradient,non-uniform shear rate and Brownian motion cause particles to migrate in fluid especially in the process of flow boiling.This mi-gration motion enhances heat transfer between nanoparticles and fluid.Therefore,the heat transfer performance of nanofluid is enhanced. It is important to note that the heat transfer coefficients nonlinearly increase with nanoparticle concentrations increasing.The heat transfer coefficients reach its maximum value at the mass concentration of 0.1% and then it decreases slightly.There exists an optimal mass concentration corresponding to the best heat transfer enhancement. The reason for the above phenomenon is attributed to nanoparticles deposition on the minichannel wall by Scanning Electron Microscopy observation.The channel surface wettability increases during the flow boiling experiment in the mass concentration range from 0.2 wt.% to 0.4 wt.%.The channel surface with wettability increasing needs more energy to produce a bubble.Therefore,the heat transfer coefficients decrease with nanoparticle concentrations in the range from 0.2 wt.% to 0.4 wt.%.In addition,a new correlation has been proposed by fitting the experimental data considering the influence of mass concentrations on the heat trans-fer performance.The new correlation can effectively predict the heat transfer coefficient.     

Z-藁本内酯在超临界CO_2中无限稀释扩散系数的测定与计算

在温度305.15~323.15 K、压力10~18 MPa范围内,采用Taylor峰扩展法测定了Z-藁本内酯在超临界CO2中的无限稀释扩散系数。结果表明,扩散系数范围在(2.75~5.55)×10-8m2/s之间,并随温度升高而增大,随压力和超临界CO2密度增大而减小,当温度和压力一定时,改性剂乙醇含量的增加能促进扩散系数缓慢增大。分别采用修正的Wilke-Chang、Scheibel、Lusis-Ratcliff、Reddy-Doraiswamy、He-Yu-Su模型预测了Z-藁本内酯的扩散系数,与实验测定值对比表明,平均绝对偏差分别为9.352%、9.356%、9.354%、9.360%和10.444%,均能很好的预测Z-藁本内酯在超临界CO2中的无限稀释扩散系数。     

42％噻嗪·毒死蜱乳油液相色谱分析

建立了在同一色谱条件下测定混剂中毒死蜱和噻嗪酮含量的方法。采用250mm×4．6mm（i．d．）Inertsil ODS-3柱分离,以甲醇＋水为流动相,在230nm紫外检测波长下,经保留时间定性确证,峰面积外标法进行定量分析。结果表明,毒死蜱与噻嗪酮的线性相关系数分别为0．9994和0．9999;变异系数分别为0．35％和0．49％;平均回收率分别为99．42％和99．37％。     

Nanofiltration for the Recovery of Low Molecular Weight Polysaccharides and Polyphenols from Winery Effluents

A wide range of nanofiltration membranes are investigated for the fractionation of a winery effluent and recovery of the polysaccharides of low molecular weight and of the polyphenols. Permeation experiments were carried out with three laboratory-made cellulose acetate membranes and two commercial membranes: NF270 membrane supplied by Filmtec Corp., Minneapolis, MN (USA) and ETNA01PP membrane supplied by Alfa Laval, Nakskov, Denmark. The five membranes were characterized by the rejection coefficients to a set of reference solutes and evaluated in terms of the rejection coefficients to polysaccharides, polyphenols, conductivity and total organic carbon. The rejection coefficients to polyphenols were overall lower than the ones to polysaccharides, meaning that the polyphenols permeate preferentially through all the membranes. Among these membranes, the NF270 membrane displayed the highest rejection coefficients for all parameters evaluated, with rejections in the order of 93.8% and 99% for polyphenols and polysaccharides, respectively. On the other hand, the ETNA01PP membrane presented the lowest rejection coefficients: around 27% to polyphenols and 72% to polysaccharides.     

A gas holdup model for cocurrent air-water-fiber bubble columns

A gas holdup model is developed for cocurrent air-water-fiber bubble column flows using the drift-flux model. The model coefficients are estimated using a nonlinear least square method and systematically acquired experimental data. The model correlates gas holdup with superficial gas and liquid velocity, and fiber type and mass fraction. The model reproduces most experimental data within ±10% error and all but 3 of the 3839 experimental data points within ±15% error. It also accurately predicts air-water bubble column gas holdup data; these data were not used in estimating the model coefficients. The physical implications of the model coefficients are also discussed.     

嘧菌酯·戊唑醇悬浮剂超高效液相色谱定量分析

建立了在同一色谱条件下测定混剂中嘧菌酯和戊唑醇含量的超高效液相色谱法。采用ACQUITY UPLC BEH C18 1.7μm 2.1×50mm(i.d.)柱分离,以甲醇+水为流动相,在225 nm紫外检测波长下,经保留时间定性确证,峰面积外标法进行定量分析。结果表明:嘧菌酯与戊唑醇的线性相关系数分别为0.9999和0.9999;变异系数分别为0.46%和0.40%;平均回收率分别为99.34%和99.40%。     

R404A在水平内螺纹管中的冷凝传热研究

经过实验与理论对比,研究了R404A在外径9.52 mm内螺纹管内局部平均冷凝换热系数。采用Cavallini纯工质与混合工质关联式分别计算的冷凝换热系数,最大偏差不到4%。在工程计算R404A内螺纹管内冷凝换热系数时,可将其以纯质来对待。分析比较Cavallini,Yu-Koyama和Kaushink-Azer关联式,各自的理论预测值和实验结果相比,表明Cavallini关联式的预测精度最高,其标准偏差为7.76%。因此Cavallini关联式对于R404A在管内的冷凝换热预测有较好的适用性。研究结果对R404A冷凝器的工程设计及其优化具有一定的参考意义。