测定有机溶剂中的微量水分——卡尔·费休法的改进

对于有机溶剂中微量水分的测定,卡尔·费休法(以下称KF法)是常用的方法之一。目前一些结晶有机化合物,如己内酰胺和一些高聚物粉末中微量水分的测定利用KF法也获得较好的效果。但是,有机物中水分含量低于100ppm时,由于KF试剂同水反应缓慢而造成终点的不明确,产生较大的误差,在测定极性有机溶剂中微量水分时尤其如此。为此,许多工作者对KF法作了改进。Archer和Jeater提出,应用N-乙基哌啶化合物作为KF试剂和水反应的催化剂,并设计了极化电极的pH计体系来确定滴定的终点,得到较好的结果。Климова等人改进了KF法的测定仪器,使之微量化,并采用二甲基甲酰胺来代     

微量水份的测定——毫库仑电量法

有机或无机物质中微量水份的测定一般沿用卡尔费休滴定法。此法适用面广,被是认为经典方法,但操作冗繁,易引入人工误差。电量法是利用电量发生器,使电解液(由有机溶剂和已与水作用过的卡尔费休试剂组成)在恒定电位或电流下,把试剂中的氢碘酸氧化成碘,碘再与样品中的水份反应。这样就取代了经典法中的滴定手续,免除了空白值和滴定误差,也毋需标定试剂的浓度,简化了操作步骤,提高了准确性。我们试验了恒电流的电量法。根据卡尔费休反应的当量关系和法拉弟电解定律,从电解     

卡尔费休滴定法测定液体推进剂混胺燃料中水分

液体推进剂混胺燃料中作为主要组分存在的三乙胺使其显示较高的碱性,对用卡尔费休滴定法测定其水分含量时产生干扰。提出了在试样的甲醇滴定介质中加入一定量的乙酸,保持液体混胺试样和乙酸的体积比小于或等于3比5,达到使滴定介质的酸度控制在最佳pH范围5～6之间。经此操作,由三乙胺的高碱度引起的干扰可消除。对已知水分含量的混胺试样按方法进行分析,算得其水分测定值的相对标准偏差(n=12)为2.1%。取不同批号的混胺试样7件,按方法进行分析并用标准气量法对结果进行校核。两种方法测定结果的相对偏差在-0.023%～0.033%之间。又根据t-检验法的结果认定,两方法所得测定值之间不存在显著差异。     

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。     

微量的残留量分析方法研究——苹果中有机磷及粉锈宁等农药的残留量测定

微量的残留量分析方法为采用系列小型仪器及微量技术,较之常量法省工作面、省时间、省劳力、省试剂。 苹果中残留量的测定,如以丙酮或甲醇提取农药,对水分及水溶性提取物如糖分,色素等可用二氯甲烷分配除去,再通过活性炭、硅藻土及硅镁吸附剂的混合层析柱进行净化;也可不净化直接进行色谱测定。作者根据文献对上述二种方法进行了改进及研究,采用GC—NPD选择性检测器、外标峰高法,对七种农药在苹果中的残留量进行了测定。     

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 　　　…     

间二氯苯纯度的测定

通过测定间二氯苯中的杂质含量得到间二氯苯的纯度。分别采用高效液相色谱法(HPLC–UVD)和气相色谱法(GC–FID)测定间二氯苯中主要杂质邻、对二氯苯的含量,结果表明两种方法所得杂质含量一致;用高效液相色谱法(HPLC)测定间二氯苯中杂质苯的含量,卡尔费休(Karl Fischer)法测定水分含量,热重法(TGA)进行灰分测定,电感耦合等离子体质谱(ICP–MS)法测定无机杂质含量。最终确定间二氯苯的纯度为99.60%,扩展不确定度为0.03%(k=2)。该方法测定结果准确可靠,具有可溯源性。     

热脱附-气相色谱法测定无机材料中微量水分

1　引　　言目前 ,国内外水分测定的方法很多 ,如热分析失重法、吸收法和卡尔·费休法等。气相色谱法具有分析速度快、灵敏度高的特点 ,常用于液体中的水分测定 ,而在固体中测定水分含量尚未见报道。本实验采用热解吸与气相色谱法结合 ,成功用于固体材料中微量水分和无机化合物中的结晶水的测定 ,并对解吸时间、温度和载气流速等条件做了研究。2　实验部分2 .1　仪器与试剂　GC 16A气相色谱仪 ,热导池检测器 (TCD) ,PYR 2A裂解器 (日本岛津公司 )。色谱柱 :0 .6m× 0 .32mmporaparkN不绣钢填充柱。碳酸钙 (分析纯 )、膨润土、活性白土…     

PAR光度法测定奶粉中锌

锌是人体内必需的微量元素之一,体内锌的缺乏常会引起某些疾病。人体内的锌需要通过食品得到补充和加强。因此,对食品中微量锌的测定日益受到人们的关注。测定食品中微量锌的标准方法为原子吸收光谱法和双硫腙比色法,这两种方法分别具有仪器昂贵、操作烦琐、操作条件不易掌握、重复性差等缺点。近年来光度法测锌的报道渐多。     

卡尔费休法测定丁醛中微量水分

卡尔费休法被广泛用于液体、固体、气体中水分含量的测定，经典的卡尔费休滴定剂由碘、吡啶、二氧化硫和甲醇配制而成，由于大多数样品可溶于甲醇，且甲醇可以使滴定终点指示灵敏、可靠，因此通用的卡尔费休滴定选用甲醇作为溶剂，但是甲醇与含有活泼羰基的醛酮类物质会生成缩醛和缩酮，导致含水量测定偏差大，因此在滴定中需选用专用的溶剂。市场上有多种牌号的醛酮专用溶剂，某些含卤醇类试剂如2-氯乙醇、三氟乙醇能抑制缩醛或缩酮的生成，适用于配制测定含醛或酮样品的卡尔费休试剂，所以醛酮试剂的溶剂大多由2-氯乙醇和三氯甲烷配制而成，国家标准中提到用乙二醇甲醚代替甲醇配制的卡尔费休试剂，可用于含活泼羰基的化合物中水分的测定，试剂的稳定性也得到改善。     

基于凝固点下降的高纯有机物纯度定值技术研究进展

介绍凝固点测量方法的研究进展。阐述了凝固点下降技术用于高纯有机物纯度定值的基本原理和适用条件,详细介绍了静力学方法和动力学方法这两种凝固点的测量方法,并介绍了两种方法在纯度定值方面的应用情况,且对两种方法的特点进行了对比,展望了凝固点下降纯度定值技术的发展趋势。     

测压法测定水中BOD的方法研究

对测压法（连续耗氧量一呼吸计量法）测定水中BOD的方法进行了研究。分别用测压法和传统方法测定了标准溶液和实际样品的BOD值,结果表明,测压法测定BOD具有生化效率高、操作简单、测试方便的优点,可连续测定BOD值并储存测量数据。测压法测定的BOD值更能表征水体可生化降解性,与传统法的测定结果有较好的可比性。     

An automated FTIR method for the routine quantitative determination of moisture in lubricants: An alternative to Karl Fischer titration

An accurate primary Fourier transform infrared (FTIR) method for the determination of moisture in mineral and ester based lubricants has been developed based on the extraction of moisture into dry acetonitrile. FTIR evaluation of acetonitrile extracts from new and used lubricants as well as common lubricant additives and contaminants which might co-extract indicated that phenolic constituents interfered significantly with moisture measurements. By measuring moisture at 3676 cm⁻¹ on the shoulder of the asymmetric OH stretching band, spectral interferences from extracted phenolic constituents were minimized. The spectra of calibration standards (0-2100 ppm), prepared by gravimetric addition of water to dry acetonitrile, were recorded in a 1000-μm CaF₂ transmission flow cell and produced linear standard curves having an S.D. of ∼±20 ppm. Lubricant sample preparation involved the vigorous shaking (20 min) of a 1:1.5 (w/v) mixture of lubricant and dry acetonitrile, centrifugation to separate the phases, acquisition of the FTIR spectrum of the upper acetonitrile layer, and subtraction of the spectrum of the dry acetonitrile used for extraction. A Continuous Oil Analyzer and Treatment (COAT^®) FTIR system was programmed to allow the automated analysis of acetonitrile extracts, and the methodology was validated by analyzing 58 new and used oils, independently analyzed by the Karl Fischer (KF) method. Linear regression of FTIR versus KF results for these oils produced a linear plot with a between-method S.D. of ±80 ppm. As implemented on the COAT^® system, this FTIR method is capable of analyzing 72 acetonitrile extracts/h and provides a high-speed alternative to the KF titrimetric procedures for the determination of water in lubricants.     

双波长代数,图解法测定三元混合物各组分的研究

某混合物物含三种组分，且均与某试剂作用，根据吸光度及化学计量比推知三组分的总含量后，不需分离，按一定规则选取两个波长，测其吸光度，用朗伯－比尔定律及代数法，图解法，可获得三元混合物各组分含量。     

Multidetermination of PCBs and pesticides by use of a dual GC column-dual detector system

Summary A new gas chromatographic method involving the use of two capillary columns, a switching valvue and electron capture-nitrogen-phosphorus detection, and allowing up to four retention characteristics per component to be obtained is reported.The proposed method was applied to the analysis for 123 compounds (13 PCBs and 110 pesticides), the determination limits and optimal measuring ranges of which are reported.The performance of the method was checked by analysis of certified standards and spiked samples, and was applied to the determination of the analytes in various water samples.     

ICP-SSEA 法测定铸铝合金中8种元素

将固体进样装置与电感耦合等离子体发射光谱仪(ICP-SSEA)联用，采用固体进样，直接测定铸铝合金中的铜、铁、镁、锰、镍、钛、硅、锌等元素含量。研究表明，该法与火花光谱法比较，具有很宽的的动态范围，测量精度和普通化学分析方法相当，同时又有火花光谱分析的速度。能满足工厂冶炼控制的要求。     

A two‐step method for rapid characterization of electroosmotic flows in capillary electrophoresis

The measurement of electroosmotic flow (EOF) is important in a capillary electrophoresis (CE) experiment in terms of performance optimization and stability improvement. Although several methods exist, there are demanding needs to accurately characterize ultra‐low electroosmotic flow rates (EOF rates), such as in coated capillaries used in protein separations. In this work, a new method, called the two‐step method, was developed to accurately and rapidly measure EOF rates in a capillary, especially for measuring the ultra‐low EOF rates in coated capillaries. In this two‐step method, the EOF rates were calculated by measuring the migration time difference of a neutral marker in two consecutive experiments, in which a pressure driven was introduced to accelerate the migration and the DC voltage was reversed to switch the EOF direction. Uncoated capillaries were first characterized by both this two‐step method and a conventional method to confirm the validity of this new method. Then this new method was applied in the study of coated capillaries. Results show that this new method is not only fast in speed, but also better in accuracy.     

Assessment and assurance of quality in water measurement by coulometric Karl Fischer titration of petroleum products

The precise and accurate determination of water in petroleum products—gasoline, diesel oil and aromatic hydrocarbons—is of significant importance for their normal functional and operational characteristics for economics as well as in meeting international requirements. The standard method ISO 12937 for the measurement of water by the coulometric Karl Fischer titration method was subject to within-laboratory assessment. Thereby it was established that the analytical procedure could not always be relied upon, especially when low levels of water were determined. The aim of this work is to assess each stage of the test procedure depending on the particular problems defined by the samples, using high-reactive Karl Fischer reagents and coulometric cells with and without a diaphragm, and to indicate the major factors causing the uncertainty. A reduced combined uncertainty was achieved by modifying the sample preparation step, the administration of the moisture in the coulometric cell, and sample injection manipulation. Experiments showed that the cell without the diaphragm ensures lower and uniform uncertainty of the measurements in the range of 0.01 to 10 mg H₂O in comparison to the cell with a diaphragm and therefore is more appropriate for the determination of low water levels in the petroleum products. A procedure that utilized a mixture of the reagent and toluene (10:6) was able to resolve the problem of two phases of formation and reduced conductivity of the reagent in direct titration of diesel oils. The results suggest that the modified procedure ensures relative expanded uncertainty equal to or less than 2.0% (n=5, confidence interval close to 95%) and 99.4% recovery for petroleum products investigated in repeatability conditions.     

Determination of Herbicide Difenzoquat Methyl Sulfate in Citruses and Baby Juices by Kinetic‐Spectrophotometric Method and HPLC Method

The purpose of this paper is to present a new kinetic‐spectrophotometric method which involve inexpensive equipment and which can be applied by all analyst who have to determine difenzoquate methyl sulfate (DFQ) residues in citruses and baby juices. The method is based on the inhibited effect of DFQ on the oxidation of sulfanile acid (SA) by hydrogen peroxide in phosphate buffer in presence Cu(II) ion. The reaction was monitored spectrophotometrically by measuring the increase in absorbance of the reaction product at 370 nm. The proposed inhibited method permits determination of DFQ over the range 0.36 to 1.80 μg/mL and 1.80 to 7.20 μg/mL, with quantification limit of 0.184 μg/mL. The relative standard deviations are 0.73‐2.90% for the concentration interval of DFQ 1.80‐0.36 μg/mL. The method was successfully applied to determination of DFQ residues in citruses and baby juices. The HPLC method is used to verify the results. The results obtained for the same samples by the two methods are quite comparable.