用离子选择性电极法测定烟用聚丙烯丝束滤棒成型水基胶中的氨氮

通过对比分析,选择氨气敏电极法快速测定烟用聚丙烯丝束滤棒成型水基胶中的氨氮含量,考察了该方法的测定条件及影响因素。结果表明：①氨气敏电极具有很高的选择性,在强碱性条件下,采用EDTA作掩蔽剂,几乎所有无机离子对测定无影响;②部分挥发性胺对测定有明显干扰,表面活性剂含量低于0.1%时无干扰;③最优条件下方法的定量限0.67μg/mL,回收率96.1％～104.9％,RSD<4％。     

烟用水基胶中柠檬酸三丁酯和乙酰柠檬酸三丁酯的GC/MS测定

为测定烟用水基胶中的柠檬酸三丁酯(TBC)和乙酰柠檬酸三丁酯(ATBC),分别用正己烷、环己烷、乙醚、异辛烷进行了萃取烟用水基胶中TBC和ATBC试验,并采用气相色谱-质谱(GC/MS)/选择离子监测(SIM)法测定了烟用水基胶中的TBC和ATBC。结果表明:①以正己烷为萃取溶剂,0.3 g胶样中加入2 mL水,萃取体积10 mL,振荡30 min萃取效果较好。②方法线性关系良好,线性相关系数均大于0.99;TBC和ATBC的检出限分别为0.26和0.20μg/mL;回收率和RSD分别为96%~107%和3.93%~4.12%。该方法适用于烟用水基胶中TBC和ATBC的测定。     

微波消解-石墨炉原子吸收光谱法测定水基胶中的铅和砷

建立了测定烟用水基胶中铅(Pb)和砷(As)的微波消解-石墨炉原子吸收光谱方法,并采用该方法测定了烟用水基胶中Pb和As的含量.结果表明:在优化条件下,Pb和As分别在0～ 50和0～ 20 μg/L范围内,工作曲线的线性相关系数、方法的检出限、相对标准偏差及回收率依次分别为0.9992和0.9995,0.075和0....     

直接进样-石墨炉原子吸收光谱法测定聚丙烯丝束滤棒成型胶粘剂中的砷与铅

建立了测定聚丙烯丝束滤棒成型胶粘剂中As与Pb的稀释直接进样-石墨炉原子吸收光谱法。结果表明:样品稀释20倍、增加120℃的干燥程序能有效避免样品在石墨炉中爆沸,提高分析的精密度;As与Pb的相对标准偏差(RSD)均小于5%,回收率分别为93.5%~104.0%和94.0%~105.3%,检出限分别为0.537μg/L与0.567μg/L。该方法适用于水乳型聚丙烯丝束滤棒成型胶粘剂中As与Pb的测定。     

连续流动分析法快速测定烟用水基胶中的甲醛

为了控制烟用水基胶中甲醛的含量,利用甲醛与间苯三酚在碱溶液中反应生成不稳定橙色化合物的最大吸收峰位于474 nm的原理,建立了连续流动分光光度法快速测定烟用水基胶中甲醛含量的方法。结果表明:该方法的相对标准偏差和回收率分别为1.30%和92.75~102.54%。该方法具有操作简单,准确、快速,可利用已有的氯模块等优点,适合于烟用水基胶中甲醛含量的测定。     

提高烟用醋酸纤维丝束质量稳定性

烟用醋酸纤维丝束质量的稳定性,不仅仅指烟用醋酸纤维丝束的各项质量指标(例如卷曲能、断裂强度、卷曲数、总旦、单旦、外油等等分质量指标)的稳定性,更重要的是表现在用醋酸纤维丝束所制成的滤棒的吸阻稳定性。吸阻稳定性是醋酸纤维丝束质量稳定性的综合反映。但是滤棒的吸阻稳定性,还与滤棒吸阻与丝束品种匹配,制作滤棒的成型机种类、成型机工况、工艺条件、操作水平、环境条件,滤棒本身的圆周SD(标准方差)值,补丝器形状补丝气压气速等等有很大关系。本文仅对喷丝帽的喷丝孔形状、摆丝结束到打包开始的时间长短、提高丝束卷曲能测试精度…     

离子色谱法测定卷烟主流烟气中氨含量的方法改进

为准确测定主流烟气中的氨含量,对离子色谱(IC)测定方法进行了改进,并采用该方法测定了59种卷烟在ISO和加拿大卫生部(Health Canada,HC)深度抽吸条件下主流烟气中的氨含量.结果表明:①烟气样品经捕集、萃取和石墨化炭黑柱(GCB)净化后,以甲基磺酸(MSA)为淋洗液,采用CS16阳离子交换柱分离.②在0～1 μg/mL范围内,线性相关系数为0.9992,方法检出限为0.0067 μg/mL,相对标准偏差为2.8％ ～ 4.5％,回收率为96％ ～ 104％.③HC深度抽吸条件下卷烟主流烟气中NH4+含量是ISO抽吸条件下的173％ ～ 378％.改进后的测定方法较好地解决了样品溶液不稳定、色谱系统易被污染的问题.     

连续流动分析法测定烟用有机肥中的氯离子含量

为了快速检测烟用有机肥中的氯含量,研究了烟用有机肥样品的前处理条件和连续流动法测定烟用有机肥中氯含量的回收率、精确度,并与硝酸银滴定法的测定结果进行了比较.结果表明:①适宜的前处理条件为称样量0.3g,提取溶剂50 mL去离子水,振荡萃取时间60 min;②方法的平均回收率为100.7％～103.0％,相对标准偏差0.31％～5.40％;③该方法的测定结果与硝酸银滴定法无显著性差异.     

热解析冷原子吸收光谱法测定烟用材料中总汞

采用热解析冷原子吸收光谱汞直接测量法测定了烟丝、滤棒、包装材料、香精和接装纸等烟用材料样品中的总汞含量.结果表明:①汞的检出限0.038 μg/kg;回收率97.6%～103.0%;RSD 0.59%～2.47%;测量范围0～1000 μg/L;②直接测量结果略高于消化处理的样品,与消解-原子荧光光谱(AFS)法无明显差异;③所测烟用材料样品中的总汞含量为0.48～97.16 μg/kg.该法适用于批量烟用材料样品中总汞含量的快速分析.     

烟用水基胶中二甘醇二苯甲酸酯的气相色谱-质谱联用法测定

分别采用正己烷、环己烷、乙醚、异辛烷进行了烟用水基胶中二甘醇二苯甲酸酯萃取实验,并采用选择离子监测模式下的气相色谱-质谱联用法测定其含量.实验结果表明:以正己烷为萃取溶剂,胶样中加入1 mL水,萃取体积10 mL,振荡40 min时萃取效果较好;测定方法线性相关系数为0.999 4,检出限为0.04μg/mL,RSD为4.98%、回收率为97%~101%.     

烟草中氨的连续流动测定

采用连续流动法测定了烟草中氨的含量,其最优化测定条件为波长660 nm,流通池光径长度50 mm,采用在线渗析处理.在此条件下氨的回收率为96.5%～106.5%,CV＜6%,说明此方法适合于烟草中氨含量的测定.     

Potential of tannin extracts as resorcinol replacements in cold cure thermoset adhesives

Blends of phenol resorcinol formaldehyde (PRF) resin with tannin obtained from bark offers the potential to minimise the quantity of resorcinol required in conventional two pot, cold set PRF wood adhesives. In the presence of ammonia, both quebracho and radiata pine bark extracts, resorcinolic and phloroglucinolic type tannins respectively, showed accelerated adhesive cure behaviour with formaldehyde, in a similar manner to PRF adhesive Greenweld technology for modifying glued timber processing rates. Segregation of pine bark components established that only tannin-containing fractions exhibited accelerated adhesive cure behaviour. Results from adhesive testing indicated adhesive blends of quebracho extract and PRF resin failed to attain satisfactory bond strength at full cure. Of the pine bark components, only a pure tannin fraction produced acceptable bond strength when blended with PRF (3:1). The study indicated pine bark extract can be substituted into PRF adhesives and adhesive cure rate accelerated using ammonia. However, extracts containing crude tannin or carbohydrate materials in adhesive blends led to inferior adhesives.     

连续流动-水杨酸盐分光光度法测定葡萄酒及 葡萄汁中氨氮含量

目的利用连续流动分析仪建立以水杨酸-次氯酸盐比色法为基础的葡萄酒和葡萄汁中氨氮的分析方法。方法葡萄汁及葡萄酒样品经过滤后直接进样,试样与试剂在蠕动泵的推动下进入化学反应模块,在密闭的管路中连续流动,并按特定的顺序和比例混合、反应,显色完全后进入流动检测池进行光度检测。结果氨氮标准溶液利用12%乙醇溶液配制线性范围为0~60 mg/L,相关系数(r2)大于0.999;方法检出限(LOD)为0.015mg/L。在低、中、高三个浓度水平添加下,样品氨氮回收率范围为90.0%~96.8%,相对标准偏差(n=6)均小于1%。结论该方法灵敏度高,重复性好,操作简便,适用于大批量葡萄酒和葡萄汁中氨氮含量的检测。     

连续流动分析法测定烟草中的氨

建立并验证了采用连续流动分析法(CFA)测定烟草中的氨含量。连续测定的RSD<2%,13个实验室共同实验的重复性和再现性值分别为:r=0.0477x+0.0043(R2=0.930)和R=0.0698x+0.0246(R2=0.980)。不同水平试验的回收率>98%,平均回收率99.7%。分别与HPLC和IC法比较,t检验结果表明CFA与2方法之间均无显著性差异。      

Measurement of dielectric properties of pumpable food materials under static and continuous flow conditions

ABSTRACT:  Continuous flow microwave sterilization is an emerging technology that has the potential to replace the conventional heating processes for viscous and pumpable food products. Dielectric properties of pumpable food products were measured by a new approach (under continuous flow conditions) at a temperature range of 20 to 130 °C and compared with those measured by the conventional approach (under static conditions). The food products chosen for this study were skim milk, green pea puree, carrot puree, and salsa con queso . Second-order polynomial correlations for the dependence of dielectric properties at 915 MHz of the food products on temperature were developed. Dielectric properties measured under static and continuous flow conditions were similar for homogeneous food products such as skim milk and vegetable puree, but they were significantly different for salsa con queso , which is a multiphase food product. The results from this study suggest that, for a multiphase product, dielectric properties measured under continuous flow conditions should be used for designing a continuous flow microwave heating system.     

MODELING OF TEMPERATURE PROFILES UNDER CONTINUOUS TUBE-FLOW MICROWAVE AND STEAM HEATING CONDITIONS

Mathematical models were developed based on perfectly mixed flow (PMF), piston flow with heat diffusion (PFHD) and laminar flow (LF) approaches to predict liquid temperature history under continuous tube‐flow microwave and steam heating conditions. Two helical glass coils placed inside domestic microwave ovens (one coil in each of the two 700 W capacity ovens) or in a steam cabinet were used for heating and a spiral condenser at the exit was used for cooling. Transient and steady state mean temperatures of the fluid were experimentally measured at the exit and were compared with predictions from the mathematical models for both systems. The residence time, velocity distribution as well as temperature profiles, along the radius and the length of the tubes, were computed using the models. The PFHD and the LF models better described temperature profiles during the initial transient period, while the PMF model shovsed a better agreement with experimental data during steady staie conditions. The occurrence of secondary turbulence in the helical coil (associated with high Dean numbers) was believed to be responsible for reducing the radial temperature gradients and achieving close to “perfectly mixed piston flow” situation. A relatively larger temperature gradient across the radius was observed under microwave heating conditions than under steam heating conditions. The time‐temperature effects were integrated to predict the lethality at selected temperatures and flow rates for both continuous‐flow thermal processing.     

利用液化天然气余冷与氨供冷的低温制冷系统性能对比

目的:对比研究利用液化天然气(LNG)余冷和氨供冷的低温制冷系统性能。方法:利用MATLAB建立两个系统的热力学和经济学模型,在基本参数下,选择适合LNG低温制冷系统的工质质量分数,同时分别改变冷间温度和制冷量,对两系统的热经济性进行对比分析。结果:随着乙二醇质量分数增加,LNG质量流量、系统功耗、蓄冷量增加,制冷系统性能系数(COP)减小,而乙二醇质量流量不变;随着冷间温度的升高,系统COP增大,而工质质量流量、功耗随之降低。同样,随着制冷量的增大,质量流量、功耗均升高,而氨低温制冷系统COP不变,LNG低温制冷系统COP增加,在5~20 kW时LNG低温制冷系统COP低于氨低温制冷系统,而20~30 kW时相反。经济性能对比表明:LNG低温制冷系统的投资费用远低于氨低温制冷系统。结论:在相同工况下,利用LNG余冷的低温制冷系统的热力学性能和经济学性能优于传统的氨低温制冷系统。     

Relationship between ruminal ammonia and nonprotein nitrogen utilization by ruminants. II. Application of published evidence to the development of theoretical model for predicting nonprotein nitrogen utilization.

Results from published experiments dealing with several aspects of nitrogen utilization by ruminants were used to test the concept of zero utilization of nonprotein nitrogen under conditions where more ammonia (greater than 5 mg ammonia nitrogen/100 ml) is in the rumen than can be converted to microbial protein. Results from experiments where the flow of non-ammonia nitrogen to the abomasum of sheep was measured indicate that when urea was the source of supplemental nitrogen, a constant quantity of amino acids reached the abomasum for all rations ranging from 10 to 23% crude protein. From growth studies, addition of nonprotein nitrogen to low protein, high energy rations caused an improved rate of gain. Additions of nonprotein nitrogen to rations resulting in predicted ruminal ammonia concentrations greater than 5 mg ammonia nitrogen/100 ml rumen fluid were without benefit. From lactation studies, nonprotein nitrogen supplementation did not improve milk production if the ration contained more than 12.5% crude protein prior to supplementation or if the predicted ruminal ammonia concentration was greater than 4 mg ammonia nitrogen/100 ml rumen fluid. The importance of the amino acid requirement of the animal as well as the composition of the ration in designing and evaluating nitrogen supplementation studies is discussed.     

Modifikation der Holzoberfläche zur Verbesserung der Verleimung

The surface of beech and spruce wood was modified using 10% ammonia solution before gluing with a PVA-c adhesive. Contact surfaces were levelled by sawing or planing and then activated with NH₄OH. The roughness of the modified surfaces has been measured. The wetting behaviour of sawed, planed and modified surfaces was determined as well as the various correlations between wetting, bonding, strength, penetration of adhesive, and spread of the bonding strength.