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串联微柱在超临界流体色谱中的应用 总被引:3,自引:0,他引:3
得力于气相和液相色谱的进步,一种新的色谱技术,超临界流体色谱(SFC)异军突起,而各种柱技术又推动了这种技术的发展速度。在SFC中开管柱和填充柱都在使用,且各具特色。但除了单位柱长具有较大的压降、柱子使用长度受到限制外,填充柱显示出更多的优点。 微柱,即填充石英毛细管柱,内径小于1mm。它以弹性石英毛细管作为柱管,管内填充色谱填料。微柱的细内径和固有的高渗透性使其兼有填充柱和 相似文献
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在内径小于1毫米的毛细管中填充颗粒状的固定相,是一种新型的气相色谱柱。Halasz和Heine在内径0.3毫米,1米长的玻璃毛细管中填装了25毫克颗粒直径为0.10—0.15毫米的Al_2O_3。在柱温为70℃,流速为13毫升/分(1大气压)的情况下,可使甲烷、乙 相似文献
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采用中孔SBA-15棒状硅胶颗粒填充毛细管柱用于毛细管电色谱(CEC)分离。这一亚微米材料直径为400 nm并具有沿相同方向伸展的高度有序、均一的圆柱形中孔。棒状的特殊形态使得填充柱的通透性良好,简化了尺寸微小的CEC柱的填充过程。修饰后的棒状SBA-15填充毛细管柱成功应用于反相和离子交换电色谱分离非极性和极性样品,获得了较高柱效(140000理论塔板/m)。流速3.2cm/min时获得最低理论塔板高度为7.1 mm。范迪米特曲线说明了SBA-15孔结构的传质阻力特征。分别以芳香酸、人参、天麻提取物为样品,对亚微米固定相毛细管电色谱柱加以评价。该固定相显示出了较高的分离能力,为纳米材料在色谱固定相中的应用提供了一个新的思路。 相似文献
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毛细管气相色谱用固定液的进展 总被引:4,自引:2,他引:2
一、前言 自从1979年弹性石英毛细管柱问世之后.毛细管气相色谱得到了迅速的发展。以毛细管柱代替填充柱的趋势日益明显.特别是1983年大内径厚液膜毛细管柱的发展和应用使这种趋势更加肯定了。当然目前在国内填充柱气相色谱仍在例行分析中占主导地位,但是随着毛细管色谱技术在国内的进一步发展,填充柱会逐步地被毛细管柱所取代。 相似文献
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Kanatyeva AY Viktorova EN Korolev AA Kurganov AA 《Journal of separation science》2007,30(17):2836-2842
Low capacity anion exchangers for IC have been prepared by modification of nonporous uniformed silica MICRA microbeads and by modification of the organic polymeric monolithic matrixes prepared in situ in quarz capillary. Due to the small particle size (1.5 microm) high-performance adsorbents were prepared allowing to obtain up to 190,000 tp/m. However, the column possesses a very high back-pressure and can be used in a short length up to 50 mm only to meet the requirements of conventional chromatographic equipment. An analysis of a test mixture of seven anions was completed within 3 min with a back column pressure of about 350 bar (HETP of about 5.5 microm, where HETP is the height equivalent to the theoretical plate). Monolithic capillary columns provide lower efficiency per column unit length than MICRA columns; however, they can be used at a longer length because of their low flow resistance. Monolithic column of ca. 40 cm length has workable pressure below 10 bar and allows separation of a five anions test mixture within less than 10 min. A better efficiency of monolithic column (HETP approximately 75 microm) can be achieved at reduced flow rates when the analysis time is not a critical parameter. 相似文献
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The influence of the degree of coverage of a silica surface with bonded C18 alkyl chains on the mass transfer mechanism in RPLC was investigated. Five packing materials were used, prepared with the same batch of silica particles (5 microm diameter, 90 A average pore size): one column was packed with the silica derivatized by trimethylchlorosilane (TMS) (C1, 3.92 micromol/m2), and the other four with the silica first derivatized with octadecyl-dimethyl-chlorosilane (C18, 0.42, 1.01, 2.03, and 3.15 micromol/m2), and then endcapped with TMS. A solution of methanol and water (25/75, v/v) was used as the mobile phase. The experimental HETP curves were acquired for each column by measuring the first moment and the second central moment of phenol and correcting them for the influence of the temperature increase due to the heat generated by the friction of the stream against the bed. The different kinetic parameters of the mass transfer in these packed chromatographic columns were identified (longitudinal diffusion, eddy diffusion, film mass transfer, and transparticle mass transfer) and quantified by fitting the experimental data to a new general HETP equation recently derived [F. Gritti, G. Guiochon, Anal. Chem., in press (AC-060203R).]. The agreement was excellent and allowed the comparison of the kinetic parameters among the six columns used. The highest column efficiency measured at conventional or fast flow rates (>0.5 ml/min) is obtained for the most retentive column, which has a surface coverage of 2.03 micromol/m2. The smallest HETP measured is as low as 10 microm, only twice the average particle diameter dp, due to the large contribution of surface diffusion (90%) to the particle effective diffusivity. However, no significant difference was observed between the efficiencies of the columns packed with C1 and C18 derivatized silica. 相似文献
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A. A. Korolev V. E. Shiryaeva T. P. Popova A. A. Kurganov 《Journal of Analytical Chemistry》2011,66(2):184-188
The effect of relative pressure on the efficiency of an open capillary column in gas chromatography was studied. It was shown
that the relative pressure was not the only parameter determining the column efficiency. The pressure drop in the column is
an additional parameter. At high values of relative pressure, the pressure drop in the column becomes determining for the
column efficiency. The smallest value of a height equivalent to a theoretical plate (HETP) is achieved at the minimum values
of the pressure drop and the relative pressure, which is accompanied by a decrease in the optimal flow rate of the carrier
gas and an increase in the time of determination. The maximum improvement in the column efficiency is determined by the column
properties and can exceed 12.5%, that is, the value predicted by Cramers for open capillary columns. 相似文献
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Summary For the first time gas chromatographic characteristics of fused-silica capillary micro-packed columns consisting of two segments (i.e., serial columns) and packed with two different particle size fractions of the same sorbent have been investigated. The height equivalent to a theoretical plate (HETP) and the specific separation number vs. carrier gas velocity dependence has been studied. The expediency of empolying serial columns in which the segment containing the finer sorbent fraction is located near the column outlet has been theoretically and practically expalined. Serial columns with such an arrangement of the two segments show a better performance from the view point of efficiency and mass transfer coefficient. 相似文献
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Motokawa M Ohira M Minakuchi H Nakanishi K Tanaka N 《Journal of separation science》2006,29(16):2471-2477
Monolithic silica capillary columns were successfully prepared in a fused silica capillary of 530 microm inner diameter and evaluated in HPLC after octadecylsilylation (ODS). Their efficiency and permeability were compared with those of columns pakked with 5-microm and 3-microm ODS-silica particles. The monolithic silica columns having different domain sizes (combined size of through-pore and skeleton) showed 2.5-4.0-times higher permeability (K= 5.2-8.4 x 10(-14) m2) than capillary columns packed with 3-mm particles, while giving similar column efficiency. The monolithic silica capillary columns gave a plate height of about 11-13 microm, or 11 200-13 400 theoretical plates/150 mm column length, in 80% methanol at a linear mobile phase velocity of 1.0 mm/s. The monolithic column having a smaller domain size showed higher column efficiency and higher pressure drop, although the monolithic column with a larger domain size showed better overall column performance, or smaller separation impedance (E value). The larger-diameter (530 microm id) monolithic silica capillary column afforded a good peak shape in gradient elution of proteins at a flow rate of up to 100 microL/min and an injection volume of up to 10 microL. 相似文献
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Pressure drop analysis in commercial CIM disk monolithic columns is presented. Experimental measurements of pressure drop are compared to hydrodynamic models usually employed for prediction of pressure drop in packed beds, e.g. free surface model and capillary model applying hydraulic radius concept. However, the comparison between pressure drop in monolith and adequate packed bed give unexpected results. Pressure drop in a CIM disk monolithic column is approximately 50% lower than in an adequate packed bed of spheres having the same hydraulic radius as CIM disk monolith; meaning they both have the same porosity and the same specific surface area. This phenomenon seems to be a consequence of the monolithic porous structure which is quite different in terms of the pore size distribution and parallel pore nonuniformity compared to the one in conventional packed beds. The number of self-similar levels for the CIM monoliths was estimated to be between 1.03 and 2.75. 相似文献
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Unger KK Kumar D Grün M Büchel G Lüdtke S Adam T Schumacher K Renker S 《Journal of chromatography. A》2000,892(1-2):47-55
Classical silica technology has reached its limit with respect to an ultimate minimum particle size of about 2 microm in diameter. Here, a novel process is presented which allows one to synthesize porous silica beads and control their particle diameter in situ, within the range of 0.2-2.0 microm. As a result, no sizing is required and losses of silica are avoided. Furthermore, the process enables one to control in situ the pore structural parameters and the surface chemistry of the silica beads. Even though surface funtionalized silicas made according to this process can principally be applied in fast HPLC the column pressure drop will be high even for short columns. In addition, the column efficiency, expressed in terms of the theoretical plate height is about H-2d(p) in the best case and limited by the A and C term of the Van Deemter equation. In other words the gain in total plate number when using 1-2 microm silica beads in short columns is minimal as compared to longer columns packed with 5 microm particles. Capillary electrochromatography (CEC) as a hybrid method enables the application of micron size as well as submicron size particles. This consequently enhances column efficiency by a factor of 5-10 when compared to HPLC. The use of short CEC columns packed with submicron size silicas provides the basis for fast and efficient miniaturized systems. The most significant feature of CEC as compared to HPLC is that the former allows one to resolve polar and ionic analytes in a single run. An alternative method for miniaturization is capillary electrophoresis (CE) which generates extremely high efficiencies combined with fast analysis. Its application, however, is limited to ionic substances. 相似文献
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The influence of the aspect ratio, rho (rho = column diameter/particle diameter), on column parameters such as efficiency, retention factors and flow resistance was studied in both high-performance liquid chromatography and capillary electrochromatography with packed capillary columns. In order to compare the true efficiencies of different columns, a procedure to account for external band broadening was applied. High efficiencies (reduced plate height h approximately 2) were obtained with capillary columns with internal diameters of 150-, 100-, and 75-microm, packed with 10-microm particles. In contrast to previous reports in the literature, no significant improvements in efficiency or flow resistance were observed when the aspect ratio of such columns was decreased. Our observations suggest that the wall effect in these types of columns is not significant. When the aspect ratio was decreased by increasing the particle size, a decrease in reduced plate height was observed. However, the results of flow resistance measurements showed that the latter effect should be attributed to differences in packing and particle batch quality rather than to differences in the aspect ratio. 相似文献
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Nobuo Tanaka Hisashi Nagayama Hiroshi Kobayashi Tohru Ikegami Ken Hosoya Norio Ishizuka Hiroyoshi Minakuchi Kazuki Nakanishi Karin Cabrera Dieter Lubda 《Journal of separation science》2000,23(1):111-116
Two types of monolithic silica columns derivatized to form an ODS phase, one prepared in a fused silica capillary (SR‐FS) and the other prepared in a mold and clad with an engineering plastic (poly‐ether‐ether‐ketone) (SR‐PEEK), were evaluated. The column efficiency and pressure drop were compared with those of a column packed with 5‐μm ODS‐silica particles and of an ODS‐silica monolith prepared in a mold and wrapped with PTFE tubing (SR‐PTFE). SR‐FS gave a lower pressure drop than a column packed with 5‐μm particles by a factor of 20, and a plate height of 20 μm at a linear velocity below 1 mm/s. SR‐PEEK showed higher flow‐resistance than the other monolithic silica columns, but they still showed a minimum plate height of 8–10 μm and a lower pressure drop than popular commercial columns packed with 5‐μm particles. The evaluation of SR‐FS columns in a CEC mode showed much higher efficiency than in a pressure‐driven mode. 相似文献
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Fabrice Gritti Irene Leonardis Jude Abia Georges Guiochon 《Journal of chromatography. A》2010,1217(24):3819-3843
The recent development of new brands of packing materials made of fine porous-shell particles, e.g., Halo and Kinetex, has brought great improvements in potential column efficiency, demanding considerable progress in the design of chromatographic instruments. Columns packed with Halo and Kinetex particles provide minimum values of their reduced plate heights of nearly 1.5 and 1.2, respectively. These packing materials have physical properties that set them apart from conventional porous particles. The kinetic performance of 4.6 mm I.D. columns packed with these two new materials is analyzed based on the results of a series of nine independent and complementary experiments: low-temperature nitrogen adsorption (LTNA), scanning electron microscopy (SEM), inverse size-exclusion chromatography (ISEC), Coulter counter particle size distributions, pycnometry, height equivalent to a theoretical plate (HETP), peak parking method (PP), total pore blocking method (TPB), and local electrochemical detection across the column exit section (LED). The results of this work establish links between the physical properties of these superficially porous particles and the excellent kinetic performance of columns packed with them. It clarifies the fundamental origin of the difference in the chromatographic performances of the Halo and the Kinetex columns. 相似文献