气体中微量油分析方法研究

对GJB 3403—98气体中微量油分析方法存在的不足进行了分析,对技术指标、标准物质、冷源、流速、取样量、油含量单位进行了探讨,并以实验证明了用冷凝富集-紫外分光光度法测定氦气、氮气、空气中微量油含量的可行性。方法改进后可以提高氮气、氦气、空气等气体中油含量分析的可靠性。     

电子气体中水分检测方法

介绍冷镜式露点法、阻容法、电解法、转化法、卡尔·费休库仑法、光学法、石英晶体振荡法的检测原理、特点和应用。冷镜式露点法适用于大多数无特殊性质的气体中水分的检测;阻容法响应快,适合在线检测;电解法操作简便、精度高、成本低;转化法针对性强,样品量小;卡尔·费休库仑法检测限低、精度高;光学法检测限低,且适合腐蚀性、有毒气体中的水分检测;石英晶体振荡法具有量程宽的优势,应用广泛。     

一种与微机联用的气体体积传感器

一种与微机联用的气体体积传感器王苏文，朱小松（南京师范大学化学系，２１００１４）（南京师范大学物理系，２１００２４）随着计算机的迅速发展，人们在化学实验领域中正越来越多地使用计算机［１］。在化学实验中许多被测的物理量，如温度、压力、体积等都是非电量，...     

高中生对气体体积理解的调查研究

以问卷和访谈的形式对高中生在对气体体积的理解上存在的问题进行分析,发现学生倾向于使用宏观和符号(公式)分析问题,在微观认识上存在缺陷,并受到原有知识和经验的严重影响,并提出2点教学建议。     

唾液中大麻毒品液相小体积提取HPLC检测

建立了小体积液相提取HPLC测定唾液中大麻类毒品含量的方法。在pH=4缓冲溶液中,加入1mL含大麻标准品的家兔唾液试样,用0.5mL氯仿超声振荡提取5min,4000r/min离心10min,取下层液体挥干,用1mL乙腈溶解后进行HPLC分析。唾液中四氢大麻酚(THC)、大麻二酚(CBD)、大麻酚(CBN)、四氢大麻酚酸的检出限(3S/N)分别为16ng、10ng、11ng、10 ng,标准曲线线性范围分别为0.32μg/μL～3.20μg/μL、0.10μg/μL～1.00μg/μL、0.11μg～1.10μg/μL、0.20μg/μL～2.00μg/μL。平均回收率均在95%～105%之间。相对标准偏差(n=6)均在3%以内。     

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。     

库仑滴定法测定六氟磷酸锂中微量水分

基于与卡尔-菲休试剂的反应用库仑滴定法测定了六氟磷酸锂中的微量水分.对同一试样的不同进样量(0.5～5.0 mL 共 10 份)按所提出方法对其水分进行了测定,所得结果在26.3～27.9 μg·g-1 之间,平均值为 27.4μg·g-1,相对标准偏差为 0.72%.     

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。     

唾液中苯丙胺类毒品的液相小体积萃取GC/MS-SIM检测

建立了一种便捷的唾液中4种毒品(苯丙胺(AM)、甲基苯丙胺(MAM)、3,4-(亚甲二氧基)苯丙胺(MDA)、3,4(亚甲二氧基)-甲基苯丙胺(MDMA))的液相小体积超声提取-气相色谱/质谱-选择离子检测分析方法并考察了小体积萃取溶剂和体积对萃取效果的影响.该方法用100μL环己烷对唾液中的毒品进行提取,直接抽取提取液用气相色谱/质谱-选择离子(GC/MS-SIM)检测,获得良好线性,相对标准偏差在15%内,准确性均在80%～120%之间,最小检测限可达0.1μg/mL.该方法灵敏、简便、快速,可用于缴获毒品及嫌疑吸毒者人体生物检材中苯丙胺类毒品的分析.     

Calibration method for the infrared-spectrometric trace gas analysis

Summary A simple and versatile calibration method for the infrared spectrometric trace analysis of gases and vapours is described. A dynamically operating set-up consisting of a capillary dosage system and a dilution unit with a set of micro-orifices was used for producing exactly known small volume fractions of trace constituents in gas mixtures. The infrared absorption measurements were performed using a Fourier transform spectrometer equipped with a long-path gas cell. Absorption coefficients of selected vibrational-rotational bands obtained by a linear least-squares fit around the threshold limit values are reported for NH₃, SO₂, CCl₄ and 1,4-dioxane as examples of trace constituents in air.

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Methode zur Kalibrierung in der infrarotspektrometrischen Spurenanalyse von Gasen

Zusammenfassung Ein vielseitig einsetzbares einfaches Kalibrierverfahren für die infrarotspektrometrische Spurenanalytik von Gasen und Dämpfen wird beschrieben. Zur Realisierung genau bekannter kleiner Volumenanteile von Spurenkomponenten in Gasmischungen diente eine nach dem dynamischen Prinzip arbeitende Apparatur, bestehend aus einem Capillardosierer und einer Verdünnungseinheit mit Mikroblenden. Zur Messung der Infrarotabsorption wurde ein Fourier-Transform-Spektrometer mit Langweggasküvette verwendet. Für NH₃, SO₂, CCl₄ und 1,4-Dioxan als Beispiele für Spurenkomponenten in Luft werden die mit Hilfe einer linearen Ausgleichsrechnung im Bereich der MAK-Werte erhaltenen Absorptionskoeffizienten ausgewählter Schwingungs-Rotationsbanden angegeben.

     

Correlation of gas solubilities in water and methanol at high pressure

A random—nonrandom—mixture equation for the Helmholtz energy of a fluid mixture is shown to correlate the solubility of inert and acidic gases in water and methanol quite accurately at pressures up to 300 bar. Further, the calculated Henry's law constants of the gases in water show good agreement with experimental data.The gas solubility models is a modification of our previous model. It contains three binary interaction parameters, one in the reduced density term and two in the attractive terms. When the nonrandom parameter vanishes the model reduces to the classical mixing rule. The model correlates vapour—liquid equilibria in binary and ternary hydrocarbon—methanol systems quite accurately.The results of the correlation are compared with results obtained using the classical van der Waals quadratic mixing rule. The random—nonrandom model is, in all cases, superior to the van der Waals model. Finally, a comparison of computer time consumption for the two models is given.     

Accurate analysis of trace earthy-musty odorants in water by headspace solid phase microextraction gas chromatography-mass spectrometry

A simple and sensitive method was developed for the simultaneous separation and determination of trace earthy-musty compounds including geosmin, 2-methylisoborneol, 2-isobutyl-3-methoxypyrazine, 2-isopropyl-3-methoxypyrazine, 2,3,4-trichloroanisole, 2,4,6-trichloroanisole, and 2,3,6-trichloroanisole in water samples. This method combined headspace solid-phase microextraction (HS-SPME) with gas chromatography-mass spectrometry and used naphthalene-d(8) as internal standard. A divinylbenzene/carboxen/polydimethylsiloxane fiber exposing at 90°C for 30 min provided effective sample enrichment in HS-SPME. These compounds were separated by a DB-1701MS capillary column and detected in selected ion monitoring mode within 12 min. The method showed a good linearity from 1 to 100 ng L(-1) and detection limits within (0.25-0.61 ng L(-1)) for all compounds. Using naphthalene-d(8) as the internal standard, the intra-day relative standard deviation (RSD) was within (2.6-3.4%), while the inter-day RSD was (3.5-4.9%). Good recoveries were obtained for tap water (80.5-90.6%), river water (81.5-92.4%), and lake water (83.5-95.2%) spiked at 10 ng L(-1). Compared with other methods using HS-SPME for determination of odor compounds in water samples, this present method had more analytes, better precision, and recovery. This method was successfully applied for analysis of earthy-musty odors in water samples from different sources.     

牡蛎中痕量有机氯农药残留量的分析方法研究

建立了同时测定牡蛎中16种有机氯农药残留量的前处理方法和气相色谱分析方法。在100℃的温度条件下,用加速溶剂提取（ASE）提取样品中的有机氯农药,用凝胶渗透色谱（GPC）结合Florisil柱净化,以RTX-5MS毛细管色谱柱分离、ECD检测器测定。结果表明,样品的加标回收率（n=3）为81％～110％,方法检出限为0．2～0．7ng／g,样品检测的相对标准偏差为2．9％～15．2％。     

Liquid gas techniques for GC trace analysis

Liquid gases (LG), i.e. low boiling compounds with vapor pressures below 5 bar at room temperature, are introduced as solvents for trace analyses. A system for preparin, diluting and handling LG solutions safely and conveniently in 5 to 500 μl amounts was developed as well as a syringe for direct injection of μl-LG samples into capillary GC. Even technical grade LG are of high purity. GC/FID of LG solutions (starting at ?60°C) allows the separation of volatile traces from the solvent peak: e.g., dichloromethane can be measured in the picogram range.     

Quantitative analysis of trace bulk oxygen in silicon wafers using an inert gas fusion method.

This paper describes a method for removing oxide film from the surface of silicon wafers using an inert gas fusion impulse furnace and precise determination of bulk oxygen within the wafer. A silicon wafer was cut to about 0.35 g (6 x 13 x 2 mm) and dropped into a graphite crucible. The sample was then heated for 40 s at 1300 degrees C. The wafer's oxide film was reduced by carbon and removed as carbon monoxide. The treated silicon sample was taken out of the graphite crucible and maintained again with the holder of the oxygen analyzer. The graphite crucible was then heated to 2100 degrees C. The treated silicon sample was dropped into the heated graphite crucible and the trace bulk oxygen in the wafer was measured using the inert gas fusion infrared absorption method. The relative standard deviations of the oxygen in silicon wafer samples with the removed surface oxide film were determined to be 0.8% for 9.8 x 10(17) atoms/cm3, and 2.7% for 13.0 x 10(17) atoms/cm3.     

Instrumental method for the determination of trace elements in water samples by neutron activation analysis

Thermal neutron activation analysis and a large-volume high-resolution Ge(Li) gammaray spectrometer, connected on-line to a DEC PDP 8/L computer, have been used to measure the concentrations of Na, Sc, Cr, Fe, Co, Ni, Zn, As, Se, Br, Rb, Ag, Sb, Cs, W and Hg in some Italian subsurface water samples. The instrumental method requires neither a chemical separation technique nor a pre- or post-concentration of the trace elements to be detected. As a consequence, this method eliminates many inherent errors associated with chemical determinations. The technique is sensitive, precise and particularly suitable for routine analysis of many trace elements at both natural and pollution levels in water samples. The interferences due to fast neutron (n, p) and (n, α) reactions are not appreciable, with the only exception of the⁵⁴Fe(n, p)⁵⁴Mn and⁵⁸Ni(n, p)⁵⁸Co reactions. Losses of volatile, elements, e. g. As, Br and Hg, during irradiation proved to be negligible.     

A continuous preconcentration/extraction method for organic trace analysis by capillary gas chromatography

Summary A slightly modified steam distillation-extraction device is described for the continuous extraction and preconcentration of organic traces in aqueous samples, prior to capillary G.C.-analysis. The quantitative performance, both theoretically and practically, is studied using phenols as the test substances. The final recovery is determined by the flow-ratio of the water and the extracting solvent and by the extraction coefficient. The process is found to be highly reproducible even at low concentration levels (ppb’s). Using 30 ml. samples with a concentration of 30 ppb (1:10^9), 100 % recoveries are obtained for the phenolic substances studied, with a relative standard deviation of about 3 %, both for methylene chloride and ethylacetate as the extracting solvents. Using methylene chloride as the extracting solvent, for phenol a maximum recovery of 80 % was obtained. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Fast gas chromatography and its use in trace analysis

There is revived interest in the development and implementation of methods of faster GC. The paper summarises the advantages of faster GC analysis, general approaches to faster GC method development and practical aspects of fast gas chromatography with the utilisation of open tubular capillary columns with the stress on trace analysis. There are a number of ways to take the advantage of the improved speed of analysis by faster GC. Numerous options exist for pushing the speed of capillary gas chromatography (CGC) analysis. The scope of this paper is also to give an overview of the present state of faster GC instrumentation which is already available for trace analysis. The practicality of fast CGC is a function of sample preparation and the matrix interferences and how they affect the resultant resolution that may be achieved. Researchers have demonstrated the applicability of fast GC to trace and ultratrace analysis of volatile and semivolatile compounds also with narrow bore columns and difficult sample matrices (such as food, and soil extract). The main development of faster GC methods has been observed in the field of environmental analysis. Practical applications are presented. Both optimised sample preparation and experimental conditions for faster GC are the future perspective of trace analysis.