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P. S. Fedotov V. A. Kronrod T. A. Maryutina B. Ya. Spivakov 《Journal of Analytical Chemistry》2002,57(1):24-30
A mathematical model was developed which describes the behavior of various liquid systems in a rotating coil column used for liquid countercurrent chromatography. The conditions of retaining the liquid stationary phase were described in detail for hydrophobic (rapidly settling) systems. Various forces that act on liquids in the column were considered. An equation was derived for the steady-state retention process. Mathematical expressions were obtained, which make it possible to estimate the stationary-phase volume retained in a column with consideration for the physicochemical properties of the liquid system in use, the rate of column rotation, and the main design parameters of the planet centrifuge. This volume directly affects the column capacity and separation efficiency and it is crucial for choosing liquid systems and experimental conditions. 相似文献
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The high performance liquid chromatography of polymers under limiting conditions of adsorption (LC LCA) separates macromolecules, either according to their chemical structure or physical architecture, while molar mass effect is suppressed. A polymer sample is injected into an adsorption-active column flushed with an adsorption promoting eluent. The sample solvent is a strong solvent which prevents sample adsorption. As a result, macromolecules of sample elute within the zone of their original solvent to be discriminated from other, non-adsorbing polymer species, which elute in the exclusion mode. LC LCA sample recovery has been studied in detail for poly (methyl methacrylate)s using a bare silica gel column and an eluent comprised toluene (adsorli) and tetrahydrofuran (desorli). Sample solvent was tetrahydrofuran. It was found that a large part of injected sample may be fully retained within the LC LCA columns. The amount of retained polymer increases with decreasing packing pore size and with higher sample molar masses and, likely, also with the column diameter. The extent of full retention of sample does not depend of sample volume. An additional portion of the injected desorli sample solvent (a tandem injection) does not fully eliminate full retention of the sample fraction and the reduced recovery associated with it. The injected sample is retained along the entire LC LCA column. The reduced sample recovery restricts applicability of many LC LCA systems to oligomers and to discrimination of the non-adsorbing minor macromolecular components of complex polymer mixtures from the adsorbing major component(s). The full retention of sample molecules within columns may also complicate the application of other liquid chromatographic methods, which combine entropic and enthalpic retention mechanisms for separation of macromolecules. 相似文献
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When a two-phase column consisting of paraffin oil and silicon oil is placed in an otherwise air-filled, horizontal glass capillary, the column starts moving spontaneously. Silicon oil displaces paraffin oil, which in its turn displaces air at atmospheric conditions; a stable film of silicon oil is left at the receding silicon oil/air meniscus. The driving force for the motion is the difference in capillary pressure at the free interfaces. However, the column moves considerably more slowly than predicted by the driving forces; it appears that the forces resisting the motion at the moving liquid/liquid/solid line are much larger than one would expect on the basis of the interfacial tension and the viscosities of the two phase system. Some considerations are made on the relationship of the theory of Fowkes to our system. Also, a method for measuring low interfacial tensions between immiscible liquids is proposed. 相似文献
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采用高效液相色谱法,对以甲酸铬、4-氯-2-氨基苯酚和2-萘酚为原料合成反应产物单偶氮染料进行分析,以体积比为80∶16∶3∶1的乙腈-水-乙酸-三乙胺为流动相,C18柱为固定相,紫外检测器检测波长为313nm。实验探讨了色谱柱、流动相及pH值等因素对分离效果的影响,确定了最佳色谱条件。该法对甲酸铬、4-氯-2-氨基苯酚、2-萘酚、反应中间体及单偶氮染料的检出限(S/N=3)分别为0.30、0.12、0.17、0.21、0.05g·L-1,这五种组分回收率为95.9%~102.5%,相对标准偏差(RSD)为0.65%~4.16%。该方法简便快速,准确度高,可用于实际生产质量控制分析。 相似文献
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The capability of dynamic phase mixing in a two-phase liquid system in a rotating coiled column, which is used to separate substances in liquid countercurrent chromatography, was studied. The effects of the hydrodynamic conditions of the chromatographic process and the physicochemical properties of the two-phase liquid systems now in use on the efficiency of phase mixing in a rotating coiled column were found. A new approach to creating a concentration gradient in the stationary phase was proposed. The following three modes of mixing stationary-phase regions within a column were found: the formation of a stable reagent concentration gradient within the rotating coiled column, the slow mixing of zones, and the complete mixing of zones.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 4, 2005, pp. 404–411.Original Russian Text Copyright © 2005 by Maryutina, Rakcheev. 相似文献
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采用高效液相色谱法测定磷酸三甲苯酯中游离甲酚的含量.利用高效液相色谱外标法对试样进行分离、检测,获得最佳色谱条件.结果表明,最佳色谱条件:C18色谱柱(250 mm×4.6 mm×5μm),流动相为甲醇∶水(体积比为8∶2),流速1.0 mL/min,紫外检测器,检测波长280 nm,柱温35℃,等度洗脱,进样量10μL.方法的加标回收率为95.9%~98.9%,相对标准偏差为1.02%~2.55%,具有操作简便、快捷、准确度高的特点. 相似文献
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《液相色谱法及相关技术杂志》2012,35(1):95-109
Abstract A general procedure has been developed for the analysis of 8 different insect growth regulators (IGRs) by using reversed-phase high-performance liquid chromatography with gradient solvent systems. The method has been used to identify and separate 8 insect growth regulators from a mixture of the standards. The method has been evaluated with different column conditions and under different solvent systems. Best resolution was obtained by using a double column and methanol/water gradient system. 相似文献
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T. A. Maryutina S. N. Ignatova B. Ya. Spivakov I. A. Sutherland 《Journal of Analytical Chemistry》2003,58(8):762-767
The effect of hydrodynamic parameters and the specific features of instrument design on the efficiency of substance separation in countercurrent liquid chromatography (CCC) was studied using a constant retention factor of the stationary phase in the column. The study was conducted with the separation of benzyl alcohol and p-cresol in a two-phase liquid system heptane–ethyl acetate–methanol–water (1.4 : 0.6 : 1 : 1) in as an example. It was shown that the peak resolution is improved with an increase in the rotational speed of the column and a decrease in the flow rate of the mobile phase. The best peak separation was attained using columns for which the ratio of the column rotation radius to the radius of column revolution was 0.615. It was shown that countercurrent chromatography allows the separation of substances with low partition constants (K < 1) in dilute solutions. The volume of the test sample may be up to 15% of the total volume of the chromatography column. 相似文献
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Focusing can be obtained in liquid thermal cycling zone adsorption by significantly increasing the temperature of the hot feed. To prevent boiling column pressure is raised. This method for concentrating dilute fluids was studied using the simulation package ADSIM. The systems studied were ethanol-water on silicalite and toluene-n-heptane on silica gel. Substantial concentration of dilute feeds while producing a pure solvent product were obtained. This research highlights the need for equilibrium data for liquid adsorption systems at elevated temperatures and pressures. 相似文献
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在未使用离子对试剂和高盐缓冲液条件下,采用亲水性C_(18)反相液相色谱柱,以甲醇-水体系为流动相,建立了面粉及面粉制品中乙二胺四乙酸二钠含量的高效液相色谱测定方法。样品采用水溶液提取,在超声辅助下与三氯化铁反应生成稳定的衍生产物,用三氯甲烷净化衍生产物。采用高效液相色谱法以pH 4.0甲醇-水溶液(10∶90,体积比)为流动相,亲水性C_(18)反相液相色谱柱为固定相,260 nm波长下测定面粉及面粉制品中乙二胺四乙酸二钠含量。乙二胺四乙酸二钠的质量浓度在1.0~50.0 mg/L范围内呈良好的线性关系,其相关系数为0.999 6,检出限为3.0 mg/kg,定量下限为10.0 mg/kg。面粉样品添加浓度在10.0~200 mg/kg范围内,加标回收率为95.0%~103%,相对标准偏差为4.0%~6.3%,可满足面粉及面制品中乙二胺四乙酸二钠的快速检测和定量分析要求。 相似文献
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When a gas is sparged into an aqueous solution of surfactant in a column, a froth layer is formed above the layer of liquid. If water is injected into the rising column of froth at a particular position, two distinct layers are formed in the froth: a wet layer below the injection plane, and a dry layer above it. In this study, a phase coexistence analysis was performed on the three-layer system. Predictions from the governing drift-flux equation were compared, using two different representations of the drainage terms, which had one and two adjustable parameters, respectively. The analysis was used to predict liquid fractions and superficial liquid velocities for the wet and dry froth zones. These were compared to experimental measurements performed with a laboratory froth column. Both versions of the analysis were in good agreement with experiment. That with the single-parameter drainage term (derived from the Richardson-Zaki equation) was marginally superior. Theoretical predictions of the liquid fraction and overflow rate from the dry froth layer are supported by the data. Considerable convective motions were observed in the wet froth layer, driven by differences in density between the entering wash liquid and the surrounding froth. 相似文献
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《液相色谱法及相关技术杂志》2012,35(2):237-249
Abstract A theoretical and practical study of recycling technique is developped for preparative liquid chromatography. The optimal cycle number, nopt, is determined for the separation of two solutes in such a way that the resolution between the second peak of cycle (n-1) and the first one of cycle n is equal to the resolution between the peaks of cycle n. A simple relationship is propounded to determine nopt which only depends on retention volumes and external volume, but it does not depend on band spreading. With this recycling technique it is shown that the maximum injection volume under optimal recycling conditions is greater than nopt times the maximum injection volume for one cycle. So the use of recycling can be opportune and beneficial to increase the throughput in preparative liquid chromatography. 相似文献
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Polar columns used in the HILIC (Hydrophilic Interaction Liquid Chromatography) systems take up water from the mixed aqueous–organic mobile phases in excess of the water concentration in the bulk mobile phase. The adsorbed water forms a diffuse layer, which becomes a part of the HILIC stationary phase and plays dominant role in the retention of polar compounds. It is difficult to fix the exact boundary between the diffuse stationary and the bulk mobile phase, hence determining the column hold-up volume is subject to errors. Adopting a convention that presumes that the volume of the adsorbed water can be understood as the column stationary phase volume enables unambiguous determination of the volumes of the stationary and of the mobile phases in the column, which is necessary for obtaining thermodynamically correct chromatographic data in HILIC systems. The volume of the aqueous stationary phase, Vex, can be determined experimentally by frontal analysis combined with Karl Fischer titration method, yielding isotherms of water adsorbed on polar columns, which allow direct prediction of the effects of the composition of aqueous–organic mobile phase on the retention in HILIC systems, and more accurate determination of phase volumes in columns and consistent retention data for any mobile phase composition. The n phase volume ratios of 18 columns calculated according to the new phase convention strongly depend on the type of the polar column. Zwitterionic and TSK gel amide and amine columns show especially strong water adsorption. 相似文献
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单滴液相微萃取-高效液相色谱法测定水中二甲戊乐灵农药残留 总被引:6,自引:1,他引:6
应用单滴液相微萃取(SD-LPME)技术建立了水体中二甲戊乐灵农药的高效液相色谱(HPLC)分析方法.研究了不同的萃取条件(萃取剂、体积、萃取时间、搅拌速度、温度等)及测定条件对检测二甲戊乐灵的影响,确定了最佳萃取条件:环己烷作萃取剂,萃取剂体积5 μL,液滴体积2 μL,搅拌速度350 r/min,35 ℃条件下萃取35 min.应用此方法测定了自来水和太湖水样中的二甲戊乐灵农药残留,相对标准偏差(RSD)在2 5%~3.4%(n=6)之间;回收率为88.0%~99.8%. 相似文献
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《Analytical letters》2012,45(13):2060-2070
Abstract A method for separation of three antidepressants, maprotiline, desipramine, and moclobemide, by reversed-phase high-performance liquid chromatography (RP-HPLC) was developed and validated. To find optimal conditions and estimate the impact of individual parameters on the separation, a complete set of 23 interdependent relationships of the mobile phase composition, temperature, and the volume flow rate were examined. Full separation of the investigated components from a laboratory mixture was achieved on a Supelcosil LC-18 (120 mm × 4.6 mm, 5 µm) column, using two solvent systems, 3% ammonium ion in water/ethanol and acetonitrile, and alternating isocratic gradient–isocratic elution modes. Relevance of the proposed method for therapeutic drug monitoring is anticipated. 相似文献
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Summary The influence of the alcohol content of the mobile phase and water, acetic acid and aniline as mobile phase additives on the
generation and shape of two additional changes of the streaming current, generated inside the liquid chromatography column
by injection of any sample and recorded before the responses of retained solutes, was studied in a normal-phase system using
silica gel as the stationary phase. The mobile phases were based on a n-heptane-1-propanol mixtures. Under the same conditions
the relationships between the column interparticle volume, the column void volume and the total liquid volume in the column
and the retention volumes of these two streaming current responses, having the form of chromatographic peaks, were studied.
The column void volume was identified with the retention volume of n-octane. The total liquid volume in the column (column
hold-up) was calculated from the weight loss of the column wetted with water at first and then dried in nitrogen stream.
The retention volume of the first streaming current response equals the column interparticle volume disregarding the mobile
phase composition. If the 95∶5 n-heptane-1-propanol mobile phase contains water up to 80% of its saturated concentration (up
to 0.114% by vol.), the retention volume of the second response agrees with the total volume of the liquid in the silica gel
column, with a precision better than 2%. At a higher relative water saturation the retention volume of the second response
increases, while the column void volume decreases. Both changes are explained by the spontaneous formation of a highly polar
stagnant liquid in the pores of the silica gel. 相似文献