微波加热法测定粮食中的水分

采用微波加热法测定粮食中的水分，测定条件是：微波功率700w、加热时间8min。测定结果的标准偏差为0．023％～0．047％(n=5)。该方法操作简便，分析时间短，分析结果准确、可靠。     

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 　　　…     

自动电位滴定法测定果汁的总酸及果汁酸度的变化规律

以鲜榨菠萝汁为样品,建立了测定果汁总酸的自动电位滴定法。测定结果表明,鲜榨菠萝汁样品中的总酸含量为3.60g/L,变异系数为0.053%,回收率为99.7%～99.9%,该方法适用于果汁中总酸量的快速测定。对样品保存过程中酸度变化的研究表明,时间、温度、水分是影响酸度变化的主要因素。     

中空纤维膜液相微萃取-高效液相色谱测定有机化合物正辛醇/水分配系数

提出了一种中空纤维膜液相微萃取-高效液相色谱直接测定有机化合物正辛醇/水分配系数的新方法,并用该方法测定了不同脂溶性有机化合物的正辛醇/水分配系数。由于中空纤维膜液相微萃取有机萃取剂用量很少,故能显著提高萃取时的传质速度,缩短萃取时间。正辛醇装入中空纤维膜内,在萃取过程中,正辛醇相和水相不会形成乳化层。萃取完成后,可直接取出正辛醇相的样品进行分析,lgK测定能在30 m in内完成。本研究对6种化合物进行了测定,测定结果用文献报道值和经典摇瓶法进行了验证。表明方法快速、准确、样品消耗量少。     

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。     

微波谐振腔微扰技术检测造纸法再造烟叶水分

研究了基于微波谐振腔微扰技术检测造纸法再造烟叶水分的方法.用最小二乘法探讨了不同微波测量参数与造纸法再造烟叶水分含量的校准模型,并将检测结果与标准烘箱法进行了比较.研究表明:该方法的测量误差小于0.4%,检测的响应速度仅为 0.1 ms.     

乙酸酐水解反应可应用于化学实验的脱水操作

乙酸酐水解反应需酸催化或加热的条件下引发,为放热反应,产物内能低,反应完全.因而可除去体系中以氢键结合的水分、吸附水分及溶液、溶胶中的游离水分.乙酸酐不易与无机组分反应,其水解产物乙酸及产生的乙酸盐容易溶解分离.该脱水方法温和,操作简便,可在实验中灵活应用.笔者在制备无水FeSO4和土壤硅酸盐分析中应用,效果明显.     

遗传算法结合神经网络用于傅里叶变换红外光谱法测定航空润滑油中水分

采用傅里叶变换红外光谱法测定了航空润滑油中的水分,通过遗传算法(GA)优化选取有效波数点,用误差反向传播神经网络(BP-ANN)进行水分预测计算。模型的预测相关系数为0.957,预测标准偏差为0.022。随机抽取某型航空润滑油样品进行预测并对预测结果进行配对t检验,结果表明:红外光谱定量分析结果与标准方法测定值没有显著性差异,模型可以用于该型在用航空润滑油水分含量现场快速检测。     

一种测定氯乙酸产品中水分的方法

1　引　　言　　氯乙酸是一种重要的化工中间体 ,该产品的质量分析目前普遍采用国标法 (化学法 )分析 ,由于该方法的终点显色灵敏度差 ,分析的重现性不好及误差较大 ,且分析时间长 (约 1 5～ 2 0ｈ) ,因此许多单位都在研究其更快、更好的分析方法 ,气相色谱法就是重点研究之一 ,目前有直接法和间接法两种 :直接法对仪器的损害严重 ,操作温度也高 ,不宜采用。间接法地仪器损害小 ,操作温度低 ,但如用内标法 ,分析操作麻烦 ,分析时间较长 ;若用修正面积归一法 ,虽操作简单 ,分析时间短 (约 15～ 2 0ｍｉｎ) ,但受产品中水分含量的影响较大 (…     

水分活度仪的校准

根据水分活度仪的工作原理和计量特性,利用溴化锂、氯化锂、乙酸钾、氯化镁、碳酸钾、溴化钠、碘化钾、氯化钠、氯化钾、硫酸钾饱和溶液作为标准物质,研究制订一种简单、准确、可靠的水分活度仪校准方法。对于不具备温度控制功能的水分活度仪,环境温度每变化10 ℃,乙酸钾、溴化锂、溴化钠饱和溶液的水分活度值变化分别可达6.67%、6.25%、5.38%。故环境温度控制对校准结果有重要影响。而环境相对湿度在20%～90%、大气压在80～106 kPa对冷镜露点法或电容法水分活度仪的校准结果几乎没有影响。该方法利用可溯源至国家湿度标准的精密露点仪测量值代替饱和盐溶液文献值,测量不确定度为0.002～0.006(k=2),解决了饱和盐溶液文献值无法溯源或不确定度较大等问题。     

二(口恶)英类化合物分析研究进展

介绍了同位素稀释气相色谱与质谱联用和生物检测法测定二恶英类化合物的研究进展，概述了国际通用的二恶英类标准分析方法体系，综述了我国二恶英类化合物分析的研究现状并对我国开展二恶英类分析检测提出了建议和展望。     

仪器分析标准物质

简述仪器分析标准物质的重要性及我国发展现状，指出了仪器分析标准物质研制中存在的问题。以光谱分析标准物质为例，介绍了仪器分析标准物质研制的特点，光谱分析标准物质的均匀性是研制的关键，其标准不确定度应由定值分析产生的标准不确定度、块状样品间的不均匀性产生的标准不确定度及块状样品内部的不均匀性产生的标准不确定度组成。     

洁净钢痕量分析最新进展

评述了当前钢铁痕量分析的一些成果和应用前景：炉前及连铸现场临线快速分析新技术;超痕量氧、氮、碳、硫的高精度检测;各种夹杂分析方法的组合改进和适用场合;精炼过程中夹杂物在线和临线分析技术的开发;钢中极微细析出相的鉴定和分离定量。     

Hydrocarbons and fuels analyses with the supersonic gas chromatography mass spectrometry--the novel concept of isomer abundance analysis

Hydrocarbon analysis with standard GC-MS is confronted by the limited range of volatile compounds amenable for analysis and by the similarity of electron ionization mass spectra for many compounds which show weak or no molecular ions for heavy hydrocarbons. The use of GC-MS with supersonic molecular beams (Supersonic GC-MS) significantly extends the range of heavy hydrocarbons that can be analyzed, and provides trustworthy enhanced molecular ion to all hydrocarbons. In addition, unique isomer mass spectral features are obtained in the ionization of vibrationally cold hydrocarbons. The availability of molecular ions for all hydrocarbons results in the ability to obtain unique chromatographic isomer distribution patterns that can serve as a new method for fuel characterization and identification. Examples of the applicability and use of this novel isomer abundance analysis (IAA) method to diesel fuel, kerosene and oil analyses are shown. It is suggested that in similarity to the "three ions method" for identification purposes, three isomer abundance patterns can serve for fuel characterization. The applications of the Supersonic GC-MS for engine motor oil analysis and transformer oil analysis are also demonstrated and discussed, including the capability to achieve fast 1-2s sampling without separation for oil and fuel fingerprinting. The relatively fast analysis of biodiesel is described, demonstrating the provision of molecular ions to heavy triglycerides. Isomer abundance analysis with the Supersonic GC-MS could find broad range of applications including petrochemicals and fuel analysis, arson analysis, environmental oil/fuel spill analysis, fuel adulteration analysis and motor oil analysis.     

Miniaturized Method for Chemical Oxygen Demand Determination Using the PhotoMetrix PRO Application

The analysis of chemical oxygen demand (COD) plays an important role in measuring water pollution, but it normally has a high ecological price. Advances in image acquisition and processing techniques enable the use of mobile devices for analytical purposes. Here, the PhotoMetrix PRO application was used for image acquisition and multivariate analysis. Statistical analysis showed no significant difference in the results compared to the standard method, with no adverse effect of the volume reduction. The cost of analysis and waste generation were reduced by one third, while the analysis time was reduced by one fifth. The miniaturized method was successfully employed in the analysis of several matrices and for the evaluation of advanced oxidation processes. The AGREE score was improved by 25% due to miniaturization. For these reasons, the miniaturized PhotoMetrix PRO method is a suitable option for COD analysis, being less hazardous to the environment due to reductions in the chemicals used and in waste generation.     

Multivariate pattern recognition of petroleum-based accelerants by solid-phase microextraction gas chromatography with flame ionization detection

A novel method has been developed for the extraction, analysis and identification of petroleum-based fuels using solid-phase microextraction with analysis by GC-FID. Multivariate data analysis is employed to simplify these data allowing for more accurate classification. Principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA) are explored for their effectiveness in establishing accelerant groupings based on the current and previous ASTM International guidelines. The SIMCA models developed for the previous and current ASTM system were 98.5% and 97.2% accurate in unknown sample class prediction. SPME in conjunction with multivariate data analysis is a new approach in accelerant sampling and classification.     

DART-Orbitrap MS: a novel mass spectrometric approach for the identification of phenolic compounds in propolis

This is the first direct analysis in real-time mass spectrometry (DART-MS) study of propolis and a first study on the analysis of bee products using high-resolution DART-MS (DART-HRMS). Identification of flavonoids and other phenolic compounds in propolis using direct analysis in real-time coupling with Orbitrap mass spectrometry (DART-Orbitrap MS) was performed in the negative ion mode for minimizing the matrix effects, while the positive ion mode was used for the confirmation of selected compounds. Possible elemental formulae were suggested for marker components. The duration of one sample analysis by DART-MS analysis lasted ca. 30 s, and all benefits of high-resolution mass spectrometry were used upon data processing using the coupling of DART with the Orbitrap mass spectrometer. The possibility for scanning analysis of dried propolis extract spots on a planar porous surface was investigated in the heated gas flow of the DART ion source with adjustable angle. As an independent method, the approach of scanning analysis is of high interest and of future potential for confirmation of the results obtained from liquid sample analysis. Scanning analysis is highly promising for further development in the bioanalytical field due to the convenience of the storage and transportation of dried sample spots.     

Nonaqueous capillary electrophoresis in pharmaceutical analysis

This review presents different solvents and electrolytes commonly used as BGEs in NACE for the analysis of pharmaceutical compounds. Most NACE applications carried out since 1998 for the analysis of compounds of pharmaceutical interest are presented in four tables: (i) analysis of drugs and related substances, (ii) analysis of chiral substances, (iii) analysis of phytochemical extracts and (iv) analysis of drugs in biological fluids. These selected examples are used to illustrate the interest in NACE versus conventional aqueous CE.     

Voltammetric methods for speciation analysis of trace metals in natural waters

Trace metals play an important role in the regulation of primary productivity and phytoplankton community composition. Metal species directly affects the biogeochemical cycling processes, transport, fate, bioavailability and toxicity of trace metals. Therefore, developing powerful methods for metal speciation analysis is very useful for research in a range of fields, including chemical and environmental analysis. Voltammetric methods, such as anodic stripping voltammetry (ASV) and competing ligand exchange-adsorptive cathodic stripping voltammetry (CLE-AdCSV), have been widely adopted for speciation analysis of metals in different natural aquatic systems. This paper provides an overview of the theory of voltammetric methods and their application for metal speciation analysis in natural waters, with a particular focus on current voltammetric methods for the discrimination of labile/inert fractions, redox species and covalently bound species. Speciation analysis of typical trace metals in natural waters including Fe, Cu, Zn, Cd, and Pb are presented and discussed in detail, with future perspectives for metal speciation analysis using voltammetric methods also discussed. This review can elaborate the particular knowledge of theory, merits, application and future challenge of voltammetric methods for speciation analysis of trace metals in natural waters.     

Environmental trace-element analysis using a benchtop total reflection X-ray fluorescence spectrometer.

Total reflection X-ray fluorescence (TXRF) analysis is an established technique for trace-element analysis in various types of samples. Though expensive large-scale systems restricted the applications in the past, in this study the capability of a benchtop system for trace elemental analysis is reported. The suitability of this system for the mobile on-site analysis of heavy metal contaminated soils and sediments is reported as well as the possibilities and restrictions of TXRF for additional applications, including trace-element analysis of water, glass and biological samples.