牛肝标准物质中氯含量的定值方法研究

针对基体标准物质中氯含量的准确定值问题,采用高温燃烧水解-离子色谱法和干灰化-电位滴定法对牛肝标准物质中的氯含量进行了测定。对两种方法的前处理和测定条件进行了优化,实验结果表明两种方法的测定结果一致,测定结果的相对标准偏差分别为0.7%和1.1%。采用NIST牛肝标准物质(SRM1577c)对两种方法进行了验证,两种方法的测定结果与标准值相符。对两种方法测定结果的不确定度进行了评定,氯测定结果的相对扩展不确定度(k=2)分别为1.6%和2.2%。两种方法测定牛肝中氯含量都准确可靠,能够满足标准物质定值的要求。     

浅谈余氯分析仪的校准

分析了水中游离氯及总余氯测定方法的现状,从余氯测定仪校准规范的检测对象、量值溯源、方法原理等方面进行了分析探讨,对实际操作中曲线标定、干扰物消除和方法优化提出建议,对计量检定机构对余氯分析仪开展校准工作有一定的指导意义。     

氟氯测定仪计量校准方法探讨

氟氯测定仪是用于煤炭或其它可燃物质中氟元素、氯元素指标的仪器,测试结果是火电厂、煤矿、钢厂、石化等行业必须的参数指标。氟氯测定仪目前并没有可依据的检定规程或校准规范等技术性文件。本文根据其仪器结构特点和工作原理提出了容易操作且可靠的校准方法,分别对其控温性能和测量性能等指标进行计量校准,校准结果具有较好的溯源性和可比性。     

AG—80环氧树脂无机氯含量化学分析方法

对ＡＧ－８０环氧树脂无机氯含量测定的离子选择电极法和改进了的电位滴定法进行了对比。试验结果指出，改进了的电位滴棕经离子造反电极法准确度高，操作程序简便，大大提高了工作效率。     

燃烧氧化偶联离子色谱法检测甲醇中有机氯

本文提出采用燃烧氧化偶联离子色谱法测定甲醇中有机氯含量的新方法。方法先用离子色谱法直接定量甲醇中无机氯含量,再用离子色谱法测量甲醇中所含的总氯在燃烧氧化过程生成的Cl_2、HCl、气态的无机氯化合物被I吸收生成的Cl~-来定量甲醇中总氯含量。由测得的总氯含量和无机氯含量,计算得甲醇中有机氯含量。实验结果表明该方法经济、简单、准确、灵敏。     

固原地区青龙山石灰岩中氯元素的测定方法试验

采用粉末压片法制样,以石灰岩、白云岩及碳酸盐岩石等国家一级标准物质和部分自制参考物质为标准样品,建立了适合青龙山石灰岩中氯元素的分析方法;用X射线荧光光谱仪对青龙山石灰岩中氯元素的含量进行测定,使用理论a系数和经验系数相结合的方法校正基体效应。该方法制样简单,分析速度快,精度高,能代替繁琐的化学分析法方法。方法精密度〈2．0％．     

氯离子在有机涂层中的渗透及涂层失效过程的电化学阻抗谱研究

采用渗透实验和电化学阻抗谱(EIS)分别研究了氯离子在氟碳涂层游离膜中的渗透规律以及不同温度、不同溶液对复合涂层体系耐蚀性能的影响.渗透实验结果表明:氯离子在氟碳涂层游离膜中的扩散存在一个时间临界点.在临界点之前,氯离子在游离膜两侧浓差作用下迅速达到动态平衡;在临界点之后,氯离子在游离膜中的扩散则呈线性增加趋势,并且氯...     

A new method of determining chlorine kinetic isotope effects

Two methods have been used to measure the chlorine leaving group kinetic isotope effect for the S(N)2 reduction of benzyl chloride to toluene by sodium borohydride in DMSO at 30.000 °C. The reaction was monitored by titrating the unreacted borohydride ion. One method involved determining the chlorine isotope effect using the classical IRMS method, which requires the conversion of the chloride ions into gaseous methyl chloride that is analyzed in an isotope ratio mass spectrometric analyses (Hill, J. W.; Fry, A. J. Am. Chem. Soc. 1962, 84, 2763. Taylor, J. W.; Grimsrud, E. P. Anal. Chem. 1969, 41, 805.). Two different measurements using this method yielded isotope effects of k(35)/k(37) = 1.007?19 ± 0.000?19 and 1.007?64 ± 0.000?19. The second method was a new technique where the ratio of the chlorine isotopes was obtained by fast atom bombardment mass spectrometry on the silver chloride recovered from the reaction, i.e., from the first step in the classical procedure. Therefore, the new method is much simpler and avoids the time-consuming preparation, purification, and recovery of the gaseous methyl chloride. Although the experimental error is larger (k(35)/k(37) = 1.008?03 ± 0.00?10 and 1.008?02 ± 0.000?65) when the new technique is used to analyze the silver chloride samples from the same set of experiments that were used to measure the isotope effect by the classical method, the chlorine isotope effect found by the two methods is identical within experimental error. This large chlorine kinetic isotope effect indicates there is considerable C(α)-Cl bond rupture in the S(N)2 transition state.     

海淤泥烧结中的物理化学变化及机理分析

本文以江苏省连云港海淤泥为原料,研究其烧结过程中可溶性盐特别是氯元素含量的变化情况。结果表明:海淤泥中含量较高的离子为Cl~-、Na~+和SiO_4~-,当温度高于600℃时Na~+含量急剧减小,到1000℃时仅剩0.1‰;当温度高于600℃时Cl~-含量也急剧减少,到900℃时几乎降为零。对1000℃烧结的海淤泥进行X射线荧光光谱(XRF)测试表明,氯元素已经消失,机理可能是以氯化氢状态逸出。研究发现烧结温度在1000℃以上时可溶性盐含量极低,能够消除对海淤泥烧结建材的顾虑。     

均匀设计法优选低温等离子体改性阳离子交换膜耐氯氧化性能

利用离子交换膜构建双膜三室电积生产金属钴是一种新的绿色湿法冶金工艺。目前市场上普通的非均相阳离子交换膜应用于该工艺时易被阳极生产的次氯酸氧化而造成膜性能下降,影响工艺效果,因此提高离子交换膜的耐氯性能是该工艺的核心技术。通过均匀试验设计,对阳离子交换膜进行低温等离子体改性,选用聚偏氟乙烯(PVDF)为接枝溶液,以期在膜表面产生高键能的含氟键官能团保护层,改善离子交换膜的耐氯氧化性能。利用活性氯浸泡法模拟实际应用中的强氧化环境,以氯离子泄漏率为表征指标,利用软件SPSS 23对均匀试验数据进行回归分析,得到实验数据显著性回归方程(R2=0.972);通过对方程系数进行t检验,挑选出影响最为显著的四个因素——等离子体放电电流强度、放电时长、接枝浓度、接枝时长;最后采用反演结合等值线图方法对方程进行寻优,预测得到的优化改性参数为:放电电流6A,放电时长5min,接枝液浓度8%,接枝时长60min。最终的验证试验表明,改性后离子交换膜的氯离子泄漏率较原膜降低了57.56%,膜的耐氯氧化性能大幅提高。     

Effects of mechanical activation and chlorine ion on nanoparticle forsterite formation

This paper reports the positive effects of chlorine ion on the forsterite formation rate. The influence of mechanical activation of talc and magnesium carbonate mixture on the formation of forsterite structure was studied in the presence of chlorine ion. Mechanical activation increased the contact surface area of the reacting phases as a consequence of intensively reduced particle size, which is very important in the case of diffusion-controlled reactions. Besides, the presence of chlorine ion affected the forsterite formation rate following annealing. The single-phase nanostructure forsterite powder with a crystallite size of about 20 nm was obtained by 5 h of mechanical activation and subsequent annealing at 1000 °C for 2 min in the presence of the chlorine ion.     

Major factors affecting the isotopic measurement of chlorine based on the Cs2Cl+ ion by thermal ionization mass spectrometry

The factors that affect isotopic measurement of chlorine based on Cs2Cl+ ion by thermal ionization mass spectrometry were studied. Graphite is essential for the emission of Cs2Cl+ ion from CsCl. No Cs2Cl+ ions are detected in the absence of graphite on the filament. The emission of Cs2Cl+ ion and the measured 37Cl/35Cl ratio were affected by different varieties of graphite, the pH value of the sample solution, and impurities in the solution. High-precision isotopic measurement of chlorine based on Cs2Cl+ ion is achieved only by using graphite with a perfect crystal structure. The measured 37Cl/35Cl ratios were much higher, and even the emission of Cs2Cl+ ion becomes impossible when pH values of the sample solution were higher than 6, corresponding to the presence of excess Cs. The measured 37Cl/35Cl ratios were higher when SO4(2-) and NO3- anions were present. The results show that the measured 37Cl/35Cl ratios are weakly related to the amount of chlorine on filament in a range from 1 to 500 microg.     

Chlorination byproducts, their toxicodynamics and removal from drinking water

No doubt that chlorination has been successfully used for the control of water borne infections diseases for more than a century. However identification of chlorination byproducts (CBPs) and incidences of potential health hazards created a major issue on the balancing of the toxicodynamics of the chemical species and risk from pathogenic microbes in the supply of drinking water. There have been epidemiological evidences of close relationship between its exposure and adverse outcomes particularly the cancers of vital organs in human beings. Halogenated trihalomethanes (THMs) and haloacetic acids (HAAs) are two major classes of disinfection byproducts (DBPs) commonly found in waters disinfected with chlorine. The total concentration of trihalomethanes and the formation of individual THM species in chlorinated water strongly depend on the composition of the raw water, on operational parameters and on the occurrence of residual chlorine in the distribution system. Attempts have been made to develop predictive models to establish the production and kinetics of THM formations. These models may be useful for operational purposes during water treatment and water quality management. It is also suggested to explore some biomarkers for determination of DBP production. Various methods have been suggested which include adsorption on activated carbons, coagulation with polymer, alum, lime or iron, sulfates, ion exchange and membrane process for the removal of DBPs. Thus in order to reduce the public health risk from these toxic compounds regulation must be inforced for the implementation of guideline values to lower the allowable concentrations or exposure.     

Novel oxidative electrophilic coupling reactions of phenoxazine derivatives with MBTH and their applications to spectrophotometric determination of residual chlorine in drinking water and environmental water samples

Novel, sensitive and rapid spectrophotometric methods, using phenoxazine (PNZ), 2-chlorophe-noxazine (CPN) and 2-trifluoromethylphenoxazine (TPN) as chromogenic reagents for the determination of residual chlorine are proposed. The methods are based on the reduction of chlorine by an electrophilic coupling reagent, 3-methyl-2-benzothiazoline hydrazono hydrochloride hydrate (MBTH) in mild hydrochloric acid medium and subsequent coupling with PNZ, CPN or TPN. The blue color formed in the reaction showed maximum absorbance at 680–690 nm and obeyed Beer's law over the range 0.1–2.2 μg ml⁻¹. The molar absorptivity values with PNZ, CPN and TPN were 2.80 × 10⁴, 2.67 × 10⁴ and 1.91 × 10⁴ l mol⁻¹ cm⁻¹ and Sandell's sensitivity values were 0.028, 0.027 and 0.028 μg cm⁻² respectively. The proposed methods were successfully applied in the determination of residual chlorine in drinking water and environmental water samples. The performance of proposed methods was evaluated in terms of Student's t-test and variance ratio F-test which indicated the significance of proposed methods over the standard spectrophotometric method.     

Mass spectrometer characterization of halogen gases in air at atmospheric pressure

We have developed a new interface for a commercial ion trap mass spectrometer equipped with APCI capable of real-time measurements of gaseous compounds with limits of detection on the order of pptv. The new interface has been tested using the detection of Br2 and Cl2 over synthetic seawater ice at atmospheric pressure as a model system. A mechanical pump is used to draw gaseous mixtures through a glass manifold into the corona discharge area, where the molecules are ionized. Analysis of bromine and chlorine in dry air show that ion intensity is affected by the pumping rate and the position of the glass manifold. The mass spectrometer signals for Br2 are linear in the 0.1-10.6 ppbv range, and the estimated 3sigma detection limit is 20 pptv. The MS signals for Cl2 are linear in the 0.2-25 ppbv range, and the estimated 3sigma detection limit is 1 ppbv. This new interface advances the field of analytical chemistry by introducing a practical modification to a commercially available ion trap mass spectrometer that expands the available methods for performing highly specific and sensitive measurements of gases in air at atmospheric pressure.     

Determination of fluorine in inorganic substances (Overview)

This is a review of physical and chemical methods of determination of fluorine in inorganic substances which have been published in the last decade. Promising new indirect variants of molecular absorption spectrometry are presented, as well as widely applied methods of ion chromatography, potentiometry with fluoride selective electrode, and others.     

The control of the electrical conductivity of germanium vanadate glasses by the admixture of chlorine during preparation

The electrical conductivity of germanium vanadate glasses depends on the relative concentrations of V⁴⁺ and V⁵⁺ ions. It is found that by adding VCl₃ to the melt when the glass is formed, the added chlorine which acts as an oxidizing agent alters the ratio of concentration of vanadium ions and thus the conductivity. The optical absorption coefficients and d.c. conductivities of germanium vanadate glasses are measured as functions of VCl₃ content. It is found that the activation energy for conductivity increases with chlorine content, the increase of the activation energy corresponding to the change in optical gap energy. It is considered therefore, that the principle of the addition of a strong oxidizing agent to the glass to alter the reduced valency ion ratio may have general application in the control of electrical conductivity in transition metal ion glasses.     

Determination of 36Cl in nuclear waste from reactor decommissioning

An analytical method for the determination of 36Cl in nuclear waste such as graphite, heavy concrete, steel, aluminum, and lead was developed. Several methods were investigated for decomposing the samples. AgCl precipitation was used to separate 36Cl from the matrix elements, followed by ion-exchange chromatography to remove interfering radionuclides. The purified 36Cl was then measured by liquid scintillation counting. The chemical yield of chlorine, as measured by ICPMS, is above 70% and the decontamination factors for all interfering radionuclides are greater than 10(6). The detection limit of this analytical method for 36Cl is 14 mBq. The method has been used to determine 36Cl in heavy concrete, aluminum, and graphite from the Danish DR-2 research reactor.     

Determination of unbiased selectivity coefficients using pulsed chronopotentiometric polymeric membrane ion sensors

A new procedure for the determination of selectivity coefficients of neutral carriers using pulsed chronopotentiometric ion selective sensors (pulstrodes) is established. Pulstrode membrane which lacks an ion-exchanger suppresses the zero current ion flux, allowing a Nernstian response slope for even highly discriminated ions. Unlike previously developed methods, unbiased selectivity remains unaltered even with the exposure to the primary ion solution for prolonged time. Studies with potassium-, silver-, and calcium-selective electrodes reveal that pulstrodes yield the same or slightly favorable unbiased selectivity coefficients than reported earlier. In contrast to alternative methods for the determination of unbiased selectivity, this technique offers a unique simplicity and reliability. Therefore the new procedure promises to be a valuable additional tool for the characterization of unbiased selectivity coefficients for the ISEs.     

Application of quantitative neutron activation analysis to the study of the cement-chloride reaction

Instrumental neutron activation analysis using a Ge(Li) detector has been used for the determination of chlorine bound in the hydration of portland cement. Results obtained are in agreement with data published by other investigators.