毛细管柱气相色谱法测定花生油中脂肪酸甲酯

采用毛细管柱气相色谱法测定油脂中7种脂肪酸甲酯的含量,选用HP-INNOWAX毛细管色谱柱(1 μm,30 m×0.53 mm),氢火焰离子化(FID)检测器,进样口温度250℃,柱温220℃,检测器温度280℃,载气流量128 mL·min-1的色谱条件,以保留时间定性,面积归一法定量.按所提的方法测定了花生油标样中7种脂肪酸甲酯的含量,测得结果与标准值相符合,测定值的相对标准偏差在0.1%～5.6%之间.     

气相色谱法检测乙醇胺混合液中二乙醇胺的含量

利用毛细管气相色谱法对乙醇胺混合液中二乙醇胺的含量进行测定,采用SE-54毛细管色谱柱,程序升温及氢火焰离子化检测器对样品进行检测。进样口温度为250℃,检测器温度为300℃,以N2为载气,邻苯二甲酸二甲酯(DMP)为内标物。该方法的相关系数为R=0.9994,变异系数为0.1184%,平均回归率为99.7%。方法可用于二乙醇胺含量的测定。     

超纯氧中ppb级一氧化碳、氮、乙烷的预浓缩气相色谱分析

〕研究了氦离子化鉴定器（HID）气相色谱与预浓缩技术相结合的方法,测定超纯氧等气体中痕量一氧化碳、氙、乙烷。此法既提高了方法的灵敏度,又克服了常温下痕量杂质与主组分分离的困难。本工作对影响方法灵敏度、准确度的诸因素进行了考察,并选择了最佳条件。文中叙述了最大浓缩样品量的选取原则及方法,还介绍了一种新的制取标样的方法和装置。本方法采用13X分子筛浓缩柱,浓缩温度为-78℃,脱附温度为150℃;色谱柱为φ4×600毫米不锈钢管,内装1克60-80目13X分子筛（室温）;以5个9的超纯氦为载气,流速40毫升／分;鉴定器为300毫居的氚钪靶为放射源;极化电压为315伏;进样量为300毫升;吹扫气量为100毫升。氧中一氧化碳、氙、乙烷的最小可检知浓度分别为1,0.5,1ppb。平均相对偏差一般不大于10%。每分析一次样品的时间约为25分钟。     

气相色谱微体积热导检测器测量氙

气相色谱微体积热导检测器(μTCD)是与毛细管柱相连的浓度型检测器。为提高-TCD测量氙的能力,研究了色谱进样条件、分离条件和检测条件对氙响应影响。结果表明,当柱流量为1.5mL/min,1.0mL样品完全进样所需最短时间为0.4min;等量氙响应值随着柱流量的增加而增大,与色谱柱温度无关;在流量比(q)等于2.3时,等量氙响应值达到最大(0.98-V.s/hPa);且当q=2～3时,其均值为0.97-V.s/hPa;相对标准偏差(RSD)为1.2%。     

气相色谱法测定胰酶中的丙酮溶剂残留量

采用气相色谱测定了胰酶中残留的丙酮溶剂,并通过外标法定量分析其含量。气相色谱条件为:氢火焰离子化检测器(FID),DMF作为溶剂,DM-WAX色谱柱(30 m×0.53 mm×1μm),载气为氮气,进样口温度为200℃,检测器温度为300℃,柱温采取程序升温。气相色谱法检测丙酮的加标回收率为92.5%～98.0%,检出限(3S/D)为0.05μg/mL。     

气相色谱法测定聚异丁烯丁二酸酐中游离酸酐

建立气相色谱法测定聚异丁烯丁二酸酐中马来酸酐含量的方法。样品用有机溶剂萃取后进色谱柱分离。色谱柱采用HP-FFAP极性毛细管柱（30 m×0.32 mm,0.25μm）,载气为高纯氮气,分流比为1∶40,进样口温度为240℃,采用程序升温方式,初始温度为50℃,以10℃/min的速率升温至230℃,保持10 min,氢火焰离子化检测器温度为260℃。马来酸酐的质量分数在0～0.40%范围内与色谱峰面积线性良好,相关系数大于0.999。样品加标回收率为96.72%～99.35%,测定结果的相对标准偏差为1.172%～1.949%(n=6)。该方法操作简便、快捷、准确度高,可以满足实际生产需求。     

超纯氧中ppb级一氧化碳、氙、乙烷的预浓缩气相色谱分析

研究了氦离子化鉴定器(HID)气相色谱与预浓缩技术相结合的方法,测定超纯氧等气体中痕量一氧化碳、氙、乙烷。此法既提高了方法的灵敏度,又克服了常温下痕量杂质与主组分分离的困难。本工作对影响方法灵敏度、准确度的诸因素进行了考察,并选择了最佳条件。文中叙述了最大浓缩样品量的选取原则及方法,还介绍了一种新的制取标样的方法和装置。本方法采用13X分子筛浓缩柱,浓缩温度为-78℃,脱附温度为150℃;色谱柱为φ4×600毫米不锈钢管,内装1克60—80目13X分子筛(室温);以5个9的超纯氦为载气,流速40毫升/分;鉴定器为300毫居的氘抗靶为放射源;极化电压为315伏;进样量为300毫升;吹扫气量为100毫升。氧中一氧化碳、氙、乙烷的最小可检知浓度分别为1,0.5,1pp)。平均相对偏差一般不大于10％。每分析一次样品的时间约为25分钟.     

气相色谱法测定大气中氪和氙

设计了一套测定气体的可调压进样装置,提出了气相色谱法-脉冲放电氦离子化检测器测定大气中氪和氙的含量。通过采用低温分离、柱程序升温及高效吸气柱消除了样品中基体气体对氪、氙测定的干扰。氪和氙的检出限(3S/N)分别为11 pg和24 pg。     

基质效应对有机磷农药测定的影响及其解决方法

该文以液液萃取-气相色谱法探讨了基质对乐果、甲基对硫磷、马拉硫磷和对硫磷4种有机磷测定的影响以及解决方法.研究表明,气相色谱法测定有机磷农药的过程中基质效应显著存在,其基质增强比例为1.01 ～3.46.基质效应由基质种类及含量、有机磷农药种类及浓度等因素决定,同时与萃取溶剂、测定条件(如衬管、进样口温度等)有关.不同萃取溶剂对有机磷农药的萃取效率不同,但均存在基质增强效应;当进样口温度为260 ℃时,可最大程度降低基质在衬管中的残留,且不造成有机磷农药的分解;衬管则应首选带玻璃棉的.实际样品/标准样品的交替进样方式可以降低基质效应强度,但难以达到回收率要求,而校正因子校正法及分析保护剂法则是降低或消除基质效应的可行办法.     

气相色谱-火焰光度检测器法测定高炉煤气和焦炉煤气中硫化物的含量

通过优化柱温、载气流量、光电倍增管极化电压、氢气和空气流量比(氢空比)、检测器温度等条件,提出了气相色谱-火焰光度检测器(FPD)法测定高炉煤气中硫化氢、羰基硫,以及焦炉煤气中硫化氢、羰基硫、二硫化碳、甲硫醇、甲硫醚、乙硫醇、噻吩、二甲基二硫的含量。样品经不同程序稀释后,采用气相色谱仪分析。在分析高炉煤气时,以GDX-502色谱柱为固定相,在柱温60℃、载气流量30 mL·min^-1、光电倍增管极化电压900 V、氢气流量80 mL·min^-1、氢空比1:0.67、检测器温度160℃条件下检测。在分析焦炉煤气时,以HF-Sulfur色谱柱作固定相,在柱程序升温条件下检测(除进样体积,其他条件和高炉煤气的一致)。结果显示：高炉煤气、焦炉煤气中的各组分质量浓度的自然对数值均在一定范围内和对应的响应值的自然对数值呈线性关系。高炉煤气中两种组分的检出限为0.56～0.87 mg·m^-3,相对误差(标准气体)为-4.6%～0.88%,测定值的相对标准偏差(RSD,n=5)为0.22%～2.4%;焦炉煤气中8种组分的检出限为0.71...     

Development of ambient sampling chemi/chemical ion source with dielectric barrier discharge

The development of a new configuration of chemical ionization (CI)‐based ion source is presented. The ambient air containing the gaseous sample is sniffed into an enclosed ionization chamber which is of sub‐ambient pressure, and is subsequently mixed with metastable species in front of the ion inlet of the mass spectrometer. Metastable helium atoms (He*) are used in this study as the primary ionizing agents and are generated from a dielectric barrier discharge (DBD) source. The DBD is powered by an AC high‐voltage supply and the configuration of the electrodes is in such a way that the generated plasma is confined within the discharge tube and is not extended into the ionization chamber. The construction of the ion source is simple, and volatile compounds released from the bulky sample can also be analyzed directly by approaching the sample to the sampling nozzle. When combined with heated nitrogen or other desorption methods, its application can also be extended to non‐volatile compounds, and the consumption for helium can be kept minimum solely for maintaining the stable discharge and gas phase ionization. Applications to non‐proximate sample analysis, direct determination of active ingredients in drug tablets and the detection of trace explosive such as hexamethylene triperoxide diamine are demonstrated. Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis of low levels of oxygen, carbon monoxide, and carbon dioxide in polyolefin feed streams using a pulsed discharge detector and two PLOT columns

A gas chromatography (GC) method is developed for rapid analysis of polyolefin feed streams for the catalyst poisons CO, CO(2), and O(2). The method uses an HP MoleSieve column in parallel with a CP-PoraPLOT Q column and a pulsed discharge detector (PDD). Detection limits for each of the potential poisons are between 50 and 250 ppb. For a 10-ppm standard, the precision of the method was +/- 4.2% for oxygen, +/- 7.8% for carbon dioxide, and +/- 2.0% for carbon monoxide. In addition to the polyolefin feed stream, nitrogen and hydrogen feed streams are also analyzed. In each case, sampling is observed to be a critical issue, with air contamination of the sample cylinder often the limiting step in determining the true level of oxygen. It is also noted that large amounts of argon are present in the standards when nitrogen is used as a balance gas. Because the trace oxygen peak partly coelutes with the larger argon peak, it is suggested that helium be used as the balance gas for all standards. This general experimental arrangement should be effective when applied to feed streams for other polymers as well.     

Gas chromatographic determination of helium in neutron-irradiated beryllium oxide

A method has been developed for the determination of helium produced during neutron irradiation of beryllium oxide ((9)Be + n --> (8)Be + 2n; (8)Be --> 2(4)He). The sample is dissolved by refluxing in a sulphuric acid-phosphoric acid mixture in an argon atmosphere. After the sample has completely dissolved, the released helium is transferred to a gas sampling bulb by means of a Toepler pump. An activated charcoal trap cooled by liquid nitrogen is used to separate helium from argon. The helium is determined by gas chromatography using a 20-ft Linde 5A molecular sieve column.     

Stability test and improvement of hydrogen analyzer with trace reduction detector

We previously developed an analyzer able to detect hydrogen concentrations of less than 50 cm3/1000 m3. The analyzer uses a carrier gas purifier and a low temperature separation column to remove impurities preventing measurement of low concentrations from the carrier and sample gases. It uses a trace reduction detector with a mercuric oxide bed to detect the concentration of hydrogen based on the reduction reaction of mercuric oxide with hydrogen. We have now evaluated the performance of the analyzer by carrying out a series of tests that measured the spectrum peak and the retention time. We used three sample gases with hydrogen concentrations of 5, 20, and 50 cm3/1000 m3 in nitrogen dilution gas. The measured peak was stable (it was within a relative standard deviation of less than 10%), and there was a linear relationship between the peak and hydrogen concentration. However, the retention time gradually shortened as the measurements were repeated. The shortening was reduced by warming the low temperature separation column used in the analyzer; it was not observed when we used a hydrogen sample gas diluted by helium instead of nitrogen. Using nitrogen as a dilution gas apparently shortens the retention time. We thus added an MS-5A separation column and a thermal conductivity detector. The nitrogen and hydrogen in the sample/carrier gas are separated, and the nitrogen is efficiently removed by switching the pass line to a release line after the hydrogen has been sent to the low temperature separation column. An analyzer using this "after-cut method" was able to stably measure infinitesimal hydrogen concentrations and was not affected by nitrogen in the sample gas.     

High resolution gas chromatographic determination of permanent gases with a helium ionization detector

The capability of the helium ionization detector (HID) to operate in connection with capillary columns for trace gas analyses has been evaluated. Two different capillary columns were considered: a PLOT fused silica column with molecular sleve and a thick film WCOT glass column with PS-255. The determination of trace impurities in gases can be achieved with evident advantages over classical adsorption columns, even using a split injection system. Direct on-column injections also have been investigated with promising results.     

Peculiarities of gas chromatographic analysis of 6N4 volatile hydrides using a helium ionization detector operated in the ionization amplification mode

A pneumovacuum circuit of a Tsvet-800-2 gas chromatograph with a helium ionization detector (HID) in the ionization amplification mode is proposed for controlling limiting trace impurities in ammonia, arsine, monosilane, and phosphine of grade 6N4. The conditions for the preparation and reliable operation of the chromatograph with the HID are systematized. The effect of an additive of (0.0–17.6) × 10^–4 mol % of hydrogen in the carrier gas of the detector on the polarity of its signal on the impurities of oxygen and nitrogen at a level of (0.5–20.0) × 10^–5 mol % is studied. Methods are proposed for eliminating systematic errors in the determination of the concentration of oxygen and nitrogen in the range from 0.5 × 10^–5 to 1 × 10^–3 mol % in 6N4 volatile hydrides, caused by “counter” impurities in the carrier gas, the mechanism of the heteropolar sensitivity of the HID, and irreversible chemical reactions of oxygen traces with phosphine and products of its decomposition on a CaA–ShM zeolite in a separating column of a chromatograph. Gas chromatography analysis of ammonia, arsine, monosilane, and phosphine of grade 6N4 was carried out.     

Micro and trace determination of oxygen in organic compounds

Samples are pyrolyzed over carbon in helium doped with chloropentane, which enhances the liberation of the oxygen. The carbon monoxide formed is determined by gas chromatography. A modification of a Carlo Erba CHN+O Elemental Analyzer is described, and results of micro and trace determinations in organic and inorganic compounds are reported. Basic reactions in this method for oxygen determination are discussed.     

Separation of mixtures of permanent gases and light hydrocarbons on spherical carbon molecular sieves by gas-solid chromatography

Summary Experimental results are presented on the application of Carbosieve S (Supelco) and Spherocarb (Analabs) spherical carbon molecular sieves for the gas chromatographic separation of mixtures of permanent gases and C₁–C₃ hydrocarbons using a single column or two columns in series. At a programmed temperature of 35–300°C, good separation of the sample components was obtained when using helium as the carrier gas. When hydrogen was used as the carrier gas and the analysis was carried out under isothermal conditions the elution sequence of oxygen and nitrogen reversed as the temperature was increased. This behaviour was observed within a temperature range of 35–225°C for Carbosieve S, and within a temperature range of 35–300°C for Spherocarb.     

气相色谱法测定丙烯中的微量氧

用气相色谱法分析丙烯中的微量氧。先将液态丙烯汽化成气态,用气体进样阀将气态丙烯样品进样到气相色谱仪中,由5A分子筛填充柱进行分离,用TCD检测器检测,外标法定量。标准气体测定结果的相对标准偏差不大于1.076%(n=5),丙烯样品中氧含量的检出限为1.0mL/m3。用该方法对实际丙烯样品进行了分析。