一种直热式快速气相色谱快速升温装置的设计

用大电流脉冲直接加热不锈钢毛细管柱, 将脉冲间隔调整到正好使柱管局部完成热平衡, 用快速PID技术控制脉冲频率和宽度, 设计了一种直热式快速升温装置. 该装置最高升温速率可达到5 ℃/s, 升温范围 40~150 ℃, 程序升温线性相关系数大于0.9996, 最大功耗74 W, 加热平均功耗小于50 W, 在34 s内完成nC8~nC17 10种正构烷烃的分离, 保留时间重复精度误差RSD在0.22%~0.55％之间, 降温和平衡时间仅为30 s. 与常规气相色谱仪相比, 该装置分析挥发性和半挥发性有机物速度可提高20倍以上, 专用于快速气相色谱仪.     

Fast Temperature Programming in Gas Chromatography using Resistive Heating

The features of a resistive-heated capillary column for fast temperature-programmed gas chromatography (GC) have been evaluated. Experiments were carried out using a commercial available EZ Flash GC, an assembly which can be used to upgrade existing gas chromatographs. The capillary column is placed inside a metal tube which can be heated, and cooled, much more rapidly than any conventional GC oven. The EZ Flash assembly can generate temperature ramps up to 1200°/min and can be cooled down from 300 to 50°C in 30 s. Samples were injected via a conventional split/splitless injector and transferred to the GC column. The combination of a short column (5 m×0.25 mm i. d.), a high gas flow rate (up to 10 mL/min), and fast temperature programmes typically decreased analysis times from 30 min to about 2.5 min. Both the split and splitless injection mode could be used. With n-alkanes as test analytes, the standard deviations of the retention times with respect to the peak width were less than 15% (n = 7). First results on RSDs of peak areas of less than 3% for all but one n-alkane indicate that the technique can also be used for quantification. The combined use of a short GC column and fast temperature gradients does cause some loss of separation efficiency, but the approach is ideally suited for fast screening as illustrated for polycyclic aromatic hydrocarbons, organophosphorus pesticides, and triazine herbicides as test compounds. Total analysis times – which included injection, separation, and equilibration to initial conditions – were typically less than 3 min.     

Separation of D-lysergic acid diethylamide derivatives using micellar electrokinetic capillary chromatography

By adjusting column temperature and applied electric field, a fast separation in micellar electrokinetic capillary chromatography was developed for the separation of D-lysergic acid diethylamide derivatives. A baseline separation of nine derivatives was accomplished with a run time of less than 12 min by utilizing elevated column temperature (60 degrees C) and an applied electric field of 387 V/cm. The number of plates generated per unit time for the separations completed at elevated temperatures was significantly higher when compared to separations at the same applied electric field but at lower temperatures (20 degrees C).     

Rapid column heating method for subcritical water chromatography

A novel resistive heating method is presented for subcritical water chromatography (SWC) that provides higher column heating rates than those conventionally obtained from temperature-programmed gas chromatography (GC) convection ovens. Since the polarity of water reduces dramatically with increasing temperature, SWC employs column heating to achieve gradient elution. As such, the rate at which the mobile phase is heated directly impacts the magnitude of such gradients applied in SWC. Data from the current study demonstrate that the maximum column heating rate attainable in a typical SWC apparatus (i.e. using a GC convection oven) is around 10 degrees C/min, even at instrument oven settings of over three times this value. Conversely, by wrapping the separation column with ceramic insulation and a resistively heated wire, the column heating rates are increased five-fold. As a result, elution times can be greatly decreased in SWC employing gradients. Separations of standard alcohol test mixtures demonstrate that the retention time of the latest eluting component decreases by 35 to 50% using the prototype method. Additionally, solute retention times in this mode deviate by less than 1% RSD over several trials, which compares very well to those obtained using a conventional GC convection oven. Results suggest that the developed method can be a useful alternative heating technique in SWC.     

Fast capillary GC using a low thermal mass column oven for the determination of residual solvents in pharmaceuticals

A low thermal mass column oven was used for fast capillary GC analysis (high throughput) of residual solvents in pharmaceutical products. A dedicated capillary column, 20 m L x 180 microm ID x 1 microm DB-624 was programmed from 35 degrees C (30 s) to 150 degrees C at 100 degrees C/min and to 250 degrees C (30 s) at 200 degrees C/min, resulting in a total GC cycle time of less than 4 min. Complete separation of a target 20-component mixture was achieved, while method performance in terms of repeatability, sensitivity, and linearity was maintained in comparison to the generic method currently applied in our laboratories.     

High throughput liquid chromatography with sub-2 microm particles at high pressure and high temperature

In this study, ultra performance liquid chromatography (UPLC) using pressures up to 1,000 bar and columns packed with sub-2 microm particles has been combined with high temperature mobile phase conditions (up to 90 degrees C). By using high temperature ultra performance liquid chromatography (HT-UPLC), it is possible to drastically decrease the analysis time without loss in efficiency. The stability and chromatographic behavior of sub-2 microm particles were evaluated at high temperature and high pressure. The chromatographic support remained stable after 500 injections (equivalent to 7,500 column volumes) and plate height curves demonstrated the capability of HT-UPLC to obtain fast separations. For example, a separation of nine doping agents was performed in less than 1 min with sub-2 microm particles at 90 degrees C. Furthermore, a shorter column (30 mm length) was used and allowed a separation of eight pharmaceutical compounds in only 40s.     

高效毛细管电泳法检测牛奶中的青霉素中间体以及3种青霉素类药物

建立了高效毛细管电泳(HPCE)同时检测牛奶中青霉素类抗生素中间体6-氨基青霉烷酸(6-APA)以及3种青霉素类药物青霉素钾(PEN)、氨苄青霉素(AMP)和阿莫西林(AMO)的方法。利用正交实验设计,对HPCE中的缓冲液离子浓度和pH值、分离电压、分离温度等分离条件进行了优化。结果表明: 在采用40 mmol/L磷酸二氢钾-20 mmol/L硼砂缓冲体系(pH 7.8)、分离电压为28 kV、分离温度为30 ℃的电泳条件下,4.5 min内可以实现上述4种青霉素类药物的快速分离检测。各组分在1.56～100 mg/L范围内有良好的线性,相关系数(r2)为0.9979～0.9998,加标回收率为84.91%～96.72%,相对标准偏差(RSDs)为1.11%～9.11% (n=6)。该方法简便、快速,可以应用于市售牛奶中4种青霉素类药物的快速检测。     

Investigation of high-speed gas chromatography using synchronized dual-valve injection and resistively heated temperature programming

High-speed temperature programming is implemented via the direct resistive heating of the separation column (2.3m MXT-5 Silicosteel column with a 180 microm I.D. and a 0.4 microm 5% phenyl/95% dimethyl polysiloxane film). Resistive temperature programming was coupled with synchronized dual-valve injection (with an injection pulse width of 2 ms), producing a complete high-speed gas chromatography (GC) system. A comparison of isothermal and temperature programmed separations of seven n-alkanes (C(6) and C(8)-C(13)) shows a substantial improvement of peak width and peak capacity with temperature programming. The system was further implemented in separations of a mixture of analytes from various chemical classes. Separations of the n-alkane mixture using three different temperature programming rates are reported. A temperature programming rate as high as 240 degrees C/s is demonstrated. The method for determination of temperature programming rate, based on isothermal data, is discussed. The high-speed resistive column heating temperature programming resulted in highly reproducible separations. The highest rate of temperature programming (240 degrees C/s) resulted in retention time and peak width RSD, on average, of 0.5 and 1.4%, respectively, for the n-alkane mixture. This high level of precision was achieved with peak widths-at-half-height ranging from 13 to 36 ms, and retention times ranging from 147 to 444 ms (for n-hexane to n-tridecane).     

Evaluation of use of a very short polar microbore column segment in high-speed gas chromatography analysis

Very fast GC analyses are commonly carried out by using 10 m x 0.1 mm id capillaries. In order to achieve rapid elution times (1-3 min), the latter are operated under suboptimum conditions. The present research is focused on the evaluation of use of a 0.1 mm id polar column segment (2 m), operated under near-to-optimum conditions, in very fast GC analysis. The results attained are compared with those derived from using a 10 m microbore column in very fast GC experiments. Prior to method development, the effects of gas velocity, temperature program rate, and sample amounts on analytical performance were evaluated. Following these preliminary applications, a complex lipidic sample, cod liver oil, was subjected to rapid separation (approximately 2.1 min) on the 10 m capillary through the application of a 50 degrees C/min temperature rate and a 130 cm/s gas velocity. The same matrix was analyzed on the 2 m capillary using the same temperature program rate and range, but with a close-to-ideal linear velocity. The results observed were of interest, as the separation was achieved in less time (1.45 min) with improved peak resolution. Finally, both methods were validated in terms of retention time and peak area repeatability, LOQ, and linearity.     

高效液相色谱法测定淀粉及淀粉制品中的顺丁烯二酸与顺丁烯二酸酐总含量

建立了基于高效液相色谱(HPLC)测定淀粉及其制品中顺丁烯二酸和顺丁烯二酸酐总含量的方法。通过优化得到最佳样品前处理条件为乙醇体积分数5%,超声时间10 min。色谱分离检测的最佳分析条件为:流动相:甲醇-1‰磷酸(2∶98),色谱柱:Plastisil ODS C18(250 mm×4.6 mm,5μm),检测波长214 nm,流速1.0 mL/min,柱温30℃。该方法对顺丁烯二酸的定量下限为5.0 mg/kg,线性范围为0.25～100 mg/L,相关系数为0.999 7,平均加标回收率为88%～89%,相对标准偏差(n=5)小于2%,能够满足实际检测需要。     

Fast HPLC method for the determination of glimepiride, glibenclamide, and related substances using monolithic column and flow program

This work presents a fast method for the simultaneous separation and determination of glimepiride, glibenclamide, and two related substances by RP LC. The separation was performed on a Chromolith Performance (RP-18e, 100 mm x 4.6 mm) column. As mobile phase, a mixture of phosphate buffer pH 3, 7.4 mM, and ACN (55:45 v/v) was used. Column oven temperature was set to 30 degrees C. The total chromatographic run time was 80 s. This was achieved using a flow program from 5 to 9.9 mL/min. Precisions of the interday and the intraday assay for both retention times and peak areas for the four analyzed compounds were less than 1.2%. The method showed good linearity and recovery. The short analysis time makes the method very valuable for quality control and stability testing of drugs and their pharmaceutical preparations.     

Application of programmable temperature vaporisation injection with resistive heating-gas chromatography flame photometric detection for the determination of organophosphorus pesticides

The combination of a programmable temperature vaporisation (PTV) injector with resistive heating GC (RH-GC), a form of fast GC, has been applied to the analysis of organophosphorus (OP) pesticides. The PTV injector was optimised in the 'at-once' solvent vent mode for the injection of ethyl acetate (10-40 microL) or ACN (10 microL). The short RH-GC column (5 m x 0.25 mm ID) with fast temperature ramps (up to 153 degrees C/ min) allowed the separation of a total of 20 OP pesticides in less than 6 min. Average recoveries between 67 and 119% were obtained for pesticides spiked at 0.01 mg/kg into apple and pear matrix. Extraction of orange juice with ACN provided higher recoveries (92-104%) for methamidophos, acephate and omethoate compared to ethyl acetate (62-73%). Results for analysis of OP pesticides in samples containing incurred residues were in good agreement with those obtained using GC-MS. The overall method was rapid, allowing 20 samples to be analysed in 4 h.     

万古霉素键合手性固定相高效液相色谱法直接分离泰妥拉唑对映体

利用反相高效液相色谱法在大环抗生素类手性固定相万古霉素键合手性固定相(Chirobiotic V)上直接分离了泰妥拉唑对映体。考察了缓冲溶液的种类、浓度和pH值,有机改性剂的种类和浓度,柱长和柱温等对手性分离的影响。优化后的色谱条件为:Chirobiotic V色谱柱(150 mm×4.6 mm,5 μm),流动相为0.02 mol/L 醋酸铵缓冲液(pH 6.0)-四氢呋喃(体积比为93∶7),流速为0.5 mL/min,柱温为20 ℃,检测波长为306 nm。在此条件下泰妥拉唑对映体达到了基线分离,分离度达1.68;对映体保留时间的相对标准偏差分别为0.48%和0.49%(n=6),峰面积的相对标准偏差分别为0.45%和0.55%(n=6)。所建立的手性分离方法具有简便快速及重复性好等优点。     

Kinetic plot method as a tool to design coupled column systems producing 100,000 theoretical plates in the shortest possible time

The present paper reports on the possibility to use the kinetic plot method (KPM) to select and design the best possible system to achieve a given number (100,000) of theoretical plates for a pharmaceutical test mixture, using the information obtained from a series of single column performance measurements of sub-2microm and supra-2microm porous shell particles conducted at three different temperatures and using mixtures of acetonitrile and 0.1% formic acid in water as the mobile phase. Because the KPM involves an extrapolation to different column lengths, the quality of the design was subsequently verified by coupling several columns to achieve the optimal total column length and run the actual analysis at the calculated optimal flow rate. The prediction error was generally better than 10%, with a slightly better prediction for t(0) and N than for the retention time t(R). The sub-2microm and the porous shell particle coupled column systems achieve the 100,000 plates about equally fast, despite the fact that the former were used at 1000bar and the latter only at 600bar. The high temperature operation (80 degrees C) yielded the fastest separation in both cases, allowing to reach 100,000 plates for a component eluting at k'=2.5 in only about 15min.     

Fast analysis by gas-liquid chromatography. Perspective on the resolution of complex fatty acid compositions

Separation of fatty acids as methyl ester (FAME) derivatives has been carried out using short and highly polar capillary column developed for fast gas-liquid chromatography (GLC) applications. The GLC parameters have been optimized in order to achieve separation of FAME ranging from 4:0 (butyric acid) to 24:1 in less than 5 min. Milk fat that has by far the most complex fatty acid composition among edible fats and oils has been used to optimize the method. The volume of the oven has been reduced in order to allow for a heating rate of 120 degrees C/min and to rapidly cool-down to the initial temperature (50 degrees C) of the GLC program. The GLC conditions developed are not suitable to achieve separation of positional and geometrical isomers of octadecenoic acid but are useful to perform separation of major fatty acids in milk fat. The conditions developed could be used to analyze edible fats and oils or biological samples such as plasma or red blood cell lipids. The results confirmed that short and highly polar fast columns operating under optimal conditions could be used to separate the fatty acids in various matrices.     

A direct resistively heated gas chromatography column with heating and sensing on the same nickel element

Nickel clad or nickel wired fused silica column bundles were constructed and evaluated. The nickel sheathing or wire functions not only as the heating element for direct resistive heat, but also as the temperature sensor, since nickel has a large resistive temperature coefficient. With this method the temperature controller is able to apply power and measure the temperature simultaneously on the same nickel element, which can effectively avoid the temperature overshoot caused by any delayed response of the sensor to the heating element. This approach also eliminates the cool spot where a separate sensor touches the column. There are some other advantages to the column bundle structure: (1) the column can be heated quickly because of the direct heating and the column's low mass, shortening analysis time. We demonstrate a maximum heating rate of 13 °C/s (800 °C/min). (2) Cooling time is also short, increasing sample throughput. The column drops from 360 °C to 40 °C is less than 1 min. (3) Power consumption is very low – 1.7 W/m (8.5 W total) for a 5 m column and 0.69 W/m (10.4 W total) for a 15 m column when they are kept at 200 °C isothermally. With temperature programming, the power consumption for a 5 m column is less then 70 W for an 800 °C/min ramp to 350 °C. (4) The column bundle is small, with a diameter of only about 2.25 in. All these advantages make the column bundle ideal for fast GC analysis or portable instruments. Column efficiencies and retention time repeatability have been evaluated and compared with the conventional oven heating method in this study. For isothermal conditions, the column efficiencies are measured by effective theoretical plate number. It was found that the plate number with resistive heat is always less than with oven heat, due to uneven heat in the column bundle. However, the loss is not significant – an average of about 1.5% for the nickel clad column and 4.5% for the nickel wired column. Separation numbers are used for the comparison with temperature programming, with results similar to those observed for isothermal conditions. Retention time repeatability for direct heat were 0.010% RSD for isotheral and 0.037% RSD for temperature programming, which is similar to those obtained by oven heat. Applications have been demonstrated, including diesel and PAH analysis.     

Thermal stability of poly[1‐(trimethylsilyl)‐1‐propyne] and the gas chromatographic stationary phase based on it

The thermal stability of poly[1‐(trimethylsilyl)‐1‐propyne] is investigated by heating the capillary column with this polymer as the stationary phase with the subsequent separation of the test mixture of light hydrocarbons. It is shown that heating of the column up to 130°C does not cause a decrease in efficiency or in the retention time of solutes. A further increase in temperature results in both decrease in column efficiency and sorbate retention. However, a decrease in column retentivity goes in one way for all the tested hydrocarbons. At the same time, the efficiency of the column is changed to a lesser degree for methane and ethane up to the temperature of polymer degradation, while for propane, butane, and iso‐butane the difference is rather sharp. The most expressed decrease in efficiency was found for iso‐butane: the column efficiency for this sorbate versus temperature of heating had two stages. The diffusion coefficients for sorbates in the polymeric phase were also evaluated and the sharp decrease in their values was found after the column heating.     

丙烯腈中微量杂质的毛细管色谱法分析

提出了一种分析丙烯腈中微量杂质的大孔径ＯＶ－１０１和ＯＶ－１７ＳＣＯＴ串联柱及毛细管进样系统。结果表明串联柱具有寿命长和分离效率高的特点,定量分析误差小于４％。     

Responses of enantioselective characteristics of imidazolinone herbicides and Chiralcel OJ column to temperature variations

Temperature affects not only the chromatographic characteristics of solute but may also alter the conformation of the stationary phase. However, temperature influences on enantioseparation of solute and conformation of chiral stationary phase (CSP) are seldom considered simultaneously. In this study, three temperature programs, a conventional heating procedure, a cyclic van't Hoff program, and a step-temperature program, were employed to evaluate temperature effects on enantioseparation of five imidazolinone herbicides on Chiralcel OJ column and the conformational state of the stationary phase. The van't Hoff plots of retention factor (k'), distribution constant (K) and separation factor (alpha) for imazapyr (1), imazapic (2), imazethapyr (3), and imazamox (4) were linear within 15-50 degrees C. Nonlinear van't Hoff plots of alpha were observed for imazaquin (5) with mobile phase of n-hexane (0.1% TFA)-2-propanol at 70/30 or 60/40 (v/v). The large molecular size of imazaquin (5) and van't Hoff plots of alpha were therefore more sensitive at detecting conformational changes of the stationary phase. Small but irreversible conformational changes occurred at 5-10 degrees C with the solvent ratio of 60/40. During the cyclic van't Hoff program, reversible conformational changes were observed at >or=15 degrees C. A switch was even visible at about 25 degrees C with the solvent ratio of 60/40 during the re-cooling cycle. The cyclic van't Hoff temperature program showed that using OJ column may yield satisfactory results at 15-50 degrees C but not at 相似文献   

A low thermal mass fast gas chromatograph and its implementation in fast gas chromatography mass spectrometry with supersonic molecular beams

A new type of low thermal mass (LTM) fast gas chromatograph (GC) was designed and operated in combination with gas chromatography mass spectrometry (GC-MS) with supersonic molecular beams (SMB), including GC-MS-MS with SMB, thereby providing a novel combination with unique capabilities. The LTM fast GC is based on a short capillary column inserted inside a stainless steel tube that is resistively heated. It is located and mounted outside the standard GC oven on its available top detector port, while the capillary column is connected as usual to the standard GC injector and supersonic molecular beam interface transfer line. This new type of fast GC-MS with SMB enables less than 1 min full range temperature programming and cooling down analysis cycle time. The operation of the fast GC-MS with SMB was explored and 1 min full analysis cycle time of a mixture of 16 hydrocarbons in the C(10)H(22) up to C(44)H(90) range was achieved. The use of 35 mL/min high column flow rate enabled the elution of C(44)H(90) in less than 45 s while the SMB interface enabled splitless acceptance of this high flow rate and the provision of dominant molecular ions. A novel compound 9-benzylazidanthracene was analyzed for its purity and a synthetic chemistry process was monitored for the optimization of the chemical reaction yield. Biodiesel was analyzed in jet fuel (by both GC-MS and GC-MS-MS) in under 1 min as 5 ppm fatty acid methyl esters. Authentic iprodion and cypermethrin pesticides were analyzed in grapes extract in both full scan mode and fast GC-MS-MS mode in under 1 min cycle time and explosive mixture including TATP, TNT and RDX was analyzed in under 1 min combined with exhibiting dominant molecular ion for TATP. Fast GC-MS with SMB is based on trading GC separation for speed of analysis while enhancing the separation power of the MS via the enhancement of the molecular ion in the electron ionization of cold molecules in the SMB. This paper further discusses several features of fast GC and fast GC-MS and the various trade-offs involved in having powerful and practical fast GC-MS.