水分测定仪的分类及其主要应用

随着科学研究的发展和生产技术的进步,水分的定量分析已被列为各类物质理化分析的基本项目之一,作为各类物质的一项重要的质量指标。根据不同形式试样中的不同水分含量提出了测定水分的不同要求。水分测定可以是工业生产的控制分析,也可是工农业产品的质量签定;可以从成吨计的产品中测定水分也可在实验室中仅用数微升试液进行水分分析;可以是含水量达百分之几至几十的常量水分分析,也可是含水量仅为百万分之一以下的痕量水分分析等。水分分析方法一般可分为两大类,即物理分析法和化学分析法。经典水分分析方法已逐渐被各种水分分析方法所代替,目前市场上存在的水分测定仪主要有卡尔·费休水分测定仪、红外水分仪、露点水分仪、微波水分仪,以及一些专用水分仪。这些仪器测定方法操作简便、灵敏度高、再现性好,并能连续测定,自动显示数据。国外的水分测定仪在精度、稳定性等方面有着一定的优势,但价格昂贵,使国内的一些实验室、企业无法承受。近年来国内的许多仪器厂商加强了对水分测定仪的研究和实践,取得了十分明显的效益,使国产水分测定仪的各项技术向国际水准靠拢,能够满足一般实验室和企业生产的需要。(中国化工仪器网)水分测定仪的分类及其主要应用     

电极水分对磷酸铁锂电池性能的影响

通过库仑法水分测试仪标定不同水分含量（0.3‰ ~ 0.7‰）的磷酸铁锂正极片,将其制备成软包型锂离子电池,对其电化学循环性能、倍率性能、交流阻抗进行了测试. 结果表明,不同水分含量极片制备的电池循环性能及倍率性能与电极水分含量有密切关系,水分含量在0.4‰ ~ 0.5‰之间时循环性能最优,水分含量超过0.6‰时电化学性能衰减严重,电池的内阻和电化学反应阻抗明显增加. 将循环200周后的软包电池进行拆解,分别使用激光粒度仪、XRD、SEM对循环后磷酸铁锂正极片进行微观形貌分析,发现水分含量超过0.6‰时极片表面发生颗粒破裂现象. XRD晶相分析表明,随着水分含量的升高,衍射峰晶面的位置有所偏移,但主要衍射峰的位置基本相同,晶型并未发生改变.     

取样量对润滑油中微量水分检测结果的影响

研究取样量对润滑油中微量水分测定结果的影响。基于卡尔·费休滴定法,在选定的测量条件下,用发生电极为有隔膜的自动库仑水分仪对基础油、有机热载体油、压缩机油、膨胀机油等新油和发动机油、汽轮机油、涡轮机油、压缩机油、齿轮油、液压油、导热油、船用油、电器绝缘油、风动工具油、金属加工油等在用油在0.1~2.0 g内各取9组不同质量的样品进行测定,得到了润滑油中微量水分准确测定所需的取样量。实验结果表明,新油取样量大于1.0 g,在用油取样量在1.0~1.5 g范围内,可以准确测定润滑油中微量水分含量。测定结果的相对标准偏差为0.83%~3.51%(n=10),样品加标回收率为95.0%~103.0%。在选择的取样量下,该方法具有良好的精密度、准确度,可连续测定多个样品,满足测定需求。     

气相色谱法测定有机肥料中的水分

建立气相色谱法测定有机肥料中水分含量的方法。样品在N,N-二甲基甲酰胺中超声提取,采用porapad-Q多孔高分子小球不锈钢填充柱(1 m×4 mm,177~250μm)为分离色谱柱,加入甲醇作为内标物,以热导检测器检测,内标法定量。结果表明,样品提取液中水的含量在0.00~77.85 mg/g范围内与色谱峰面积呈良好的线性关系,相关系数为0.9996。样品测定结果的相对标准偏差为0.79%~3.98%(n=7),加标回收率为95.3%~101.3%。该方法准确度高,重现性好,适用于有机肥料中水分含量的定量分析。     

卡尔费休法快速测定碳酸氢铵中水分

国家标准中碳酸氢铵水分的测定采用 GB/T3559- 1 992的量气管法 ,由于该方法对电石的粒度 ,保存时间均有严格要求 ,对整个装置的密封性要求很高 ,并且要同时测定试验时的温度与压力 ,操作起来不方便。因此 ,本文尝试用卡尔费休法测定碳酸氢铵中水分的含量。1　方法原理在碳酸氢铵样品的甲醇溶液中滴加卡尔费休试剂时 ,由于样品中有水分存在 ,会发生下列反应 :2 H2 O + I2 + SO2 2 HI+ H2 SO4 ( 1 )反应 ( 1 )进行后 ,生成了氢碘酸与硫酸 ,则会发生下述副反应 :NH4 HCO3 + HI NH4 I+ H2 O + CO2 ( 2 )NH4 HCO3 + H2 SO4 　　　…     

有机溶剂中微量水分的测定

绕丹宁与水在有机溶剂中发生诱导荷移反应，产生吸收光谱移动且吸收峰增大。基于此，优化了实验条件，建立了一种快速、简便、灵敏的测定有机溶剂中微量水分的新方法。甲醇、醋酸溶剂中的水分含量分别在3％-10％（φ）、0～4％（φ）范围及乙醇、1-丙醇、丙酮、乙酸乙酯溶剂中水分含量在0～5％（φ）范围内与吸光度（A）呈线性关系。其相关系数分别是0．9992、0．9996、0．9992、0．9982、0．9990和0．9995。使用本方法测定了灯用酒精中水分含量，结果令人满意。     

小体积常压气体中微量水分分析方法研究

本文在卡尔·费休库仑法的基础上建立了一套独特的分析系统和相应的分析方法,用以分析常温常压下小体积气体中微量水分。通过检测高纯氮气中的微量水分考核了方法的精密度,分析数据的实验标准偏差U<10%;通过分析空气中的水分含量验证了方法的准确度,空气中水分的测量值与计算值在误差范围内一致。小体积常压气体中微量水分的卡尔.费休分析方法的建立,对分析贮存环境气体内水分变化规律及采取有效措施控制封装气体内水分含量,建立较干燥的贮存环境具有指导作用。     

化学药品中水分测定方法的探讨

以泰瑞米特钠为例进行水分的实验测定,涉及卡尔费休氏、干燥失重、热重分析、单晶X射线衍射、元素分析和动态水分吸附分析等方法,可引导学生加强对药物中水分的理解,培养学生对药物中水分的研究思路。     

卷烟主流烟气气相水分的捕集及气相色谱法测定

提出了用剑桥滤片捕集烟气粒相物,以异丙醇和乙醇为吸收液、两级碰撞捕集器串联捕集烟气气相物,用气相色谱法测定主流烟气粒相和气相水分含量的方法。试验结果表明:线性范围为0.8～6.0g.L-1,相对标准偏差(n=5)小于2.5%之间,回收率为93.46%～106.15%。采用该法对7种卷烟主流烟气中粒相和气相水分进行测定,烟气总水分含量为6.77～9.43mg.支-1,其中气相水分约占总水分的65%～75%,表明气相水分是研究卷烟品质的重要参数。     

现场水分测定器的测试精度试验

现场测定机械用油中水分含量通常用ＧＢ８０３０－８７润滑油现场俊俏地。该方法读压力表数值的时间不定,人为因素大,测试结果不稳。文中对该测试方法的操作步骤及读数方法作了改进,使测定水分的时间缩短、精度提高。     

Opto-thermal Moisture Content and Moisture Depth Profile Measurements in Organic Materials

Opto-thermal transient emission radiometry(OTTER) is a infrared remote sensing technique, which has been successfully used in in vivo skin moisture content and skin moisture depth profiling measurements. In present paper, we extend this moisture content measurement capability to analyze the moisture content of fruit (tomato. grape, etc. ) skins, and to study the relationship between fruits ripening process and their sur-face moisture and moisture depth profiles.     

Moisture permeation of clothing

The manner in which the wetting and drying behavior of a textile fabric depends upon the properties of the fibers comprising it is of both practical and theoretical significance. The consumer is justifiably interested in the relationship of fiber content to such serviceability criteria as wicking, solubility, wettability, and speed of drying. At the same time, the extent to which the drying of textiles conforms with or departs from theory is of scientific interest, particularly if noteworthy distinctions in behavior among fabrics can be related to intrinsic fiber properties or geometry of the textile structure. This work was undertaken to answer some practical questions about fiber-fabric-water relationships. Especially of interest was the extent to which rate of fabric drying might depend upon (a) fiber moisture regain, and (b) speed of capillary migration. These and other aspects of the general problem were examined in the light of pertinent theory in connection with appropriate practical findings. This revised version was published online in July 2006 with corrections to the Cover Date.     

低分子量N-羧丁酰壳聚糖的合成及其吸湿保湿性

低分子量N-羧丁酰壳聚糖的合成及其吸湿保湿性;低分子量壳聚糖;低分子量N-羧丁酰壳聚糖;吸湿性;保湿性     

Moisture effects in lithium-doped polyimide films

The interaction of lithium-doped polyimide films with water has been investigated. Contact angle and water absorption/desorption measurements have been performed to obtain an idea of the hygroscopic nature of these lithium-doped films. Contact angles were found to decrease as the amount of surface lithium increased. Film water content was also found to increase as the weight percent of total lithium content in the film increased. This phenomenon has been used to rationalize the electrical resistivity–temperature profile of certain lithium films which display an increase in electrical resistivity upon drying.     

Moisture adsorption of glucomannan and xylan hemicelluloses

Wood and wood materials are highly sensitive to moisture in the environment. To a large extent this relates to the hygroscopicity of wood hemicelluloses. In order to increase our understanding of the effects of moisture sorption of the major wood hemicelluloses, glucomannan and xylan, model experiments using films of amorphous konjak glucomannan and rye arabinoxylan were conducted. Moisture-induced expansion and stiffness softening were characterized using dynamic mechanical testing. Both hemicelluloses showed a threshold around 5 % of moisture content above which swelling increased whereas the modulus decreased by more than 70 %. FTIR spectra, using H₂O and D₂O, indicated that even at high RH about 15 % of the hydroxyl groups were not accessible to hydrogen exchange by D₂O. For xylan both hydroxyl groups were found to exchange in the same manner while for the glucomannan the O(6)H group seemed to be the most accessible.     

Moisture variations in brine-salted pasta filata cheese

A study was made of the moisture distribution in brine-salted pasta filata cheese. Brine-salted cheeses usually develop reasonably smooth and predictable gradients of decreasing moisture from center to surface, resulting from outward diffusion of moisture in response to inward diffusion of salt. However, patterns of moisture variation within brine-salted pasta filata cheeses, notably pizza cheese, are more variable and less predictable because of the peculiar conditions that occur when warm cheese is immersed in cold brine. In this study, cold brining resulted in less moisture loss from the cheese surface to the brine. Also it created substantial temperature gradients within the cheese, which persisted after brining and influenced the movement of moisture within the cheese independently of that caused by the inward diffusion of salt. Depending on brining conditions and age, pizza cheese may contain decreasing, increasing, or irregular gradients of moisture from center to surface, which may vary considerably at different locations within a single block. This complicates efforts to obtain representative samples for moisture and composition testing. Dicing the entire block into small (e.g., 1.5 cm) cubes and collecting a composite sample after thorough mixing may serve as a practical sampling approach for manufacturers and users of pizza cheese that have ready access to dicing equipment.     

甲醇中微量水分标准物质的研制

用无水甲醇试剂研制了甲醇中微量水分标准物质,对研制的标准物质量值进行了均匀性和稳定性检验。结果表明,该标准物质均匀性良好,其量值在一年内无显著变化,具有较好的稳定性。采用与国家一级标准物质比较法进行定值,研制的甲醇中微量水分标准物质的定值结果为0.103%,相对扩展不确定度为3%(k=2)。该标准物质满足卡尔·费休水分测定仪检定校准的要求。     

Highly Conductive MXene Film Actuator Based on Moisture Gradients

MXene (Ti₃C₂T_x) is a new 2D material with both hydrophilicity and high electrical conductivity, and it has shown promise in smart electronic devices. Reported herein is a homogeneous MXene film actuator with high electrical conductivity triggered by moisture gradients. The actuator is highly sensitive to moisture and undergoes deformation, with the maximum bending angle as high as 155° at a relative humidity difference of 65 %. Several analysis methods show that the humidity drive and large deformation of the MXene film occur in situ by asymmetric expansion of the bilayer structure. The combination of deformation and electrical conductivity makes this film applicable to flexible excavators, electrical switches, and other fields, applications that are difficult to achieve directly by using other 2D materials. More importantly, this work further expands the new application range of MXene materials and provides new opportunities for building the next generation of high‐conductivity smart actuators.     

Moisture diffusion into epoxy adhesive: testing and modeling

Moisture diffusion into epoxy adhesive is investigated through utilizing complete fluid immersion tests in distilled water. Apparent diffusivity for each specimen is determined by two methods, one using the diffusion data at early times (at low loading) and the other using the data at large times (close to the saturation point). The results of the two methods are quite different, indicating that diffusivity is concentration dependent. The apparent diffusivity values obtained through the method using the early data points are about twice those obtained through the method utilizing the data points at large diffusion times. Variance of diffusivity with concentration is also considered as the third method of analysis to determine the concentration dependency. A good agreement is observed between the resultant Fickian model solved numerically and the experimental data. The latter result appears to indicate a change in the excess volume of mixing during the sorption process.