高效液相色谱梯度洗脱中弱溶剂的在线净化

利用一个在线净化预柱减少了高压梯度洗脱中由于试剂纯度不够造成的基线噪音。预柱的位置在溶剂泵Ａ和流动相混合器之间,由一个六通阀来控制。在线净化结果良好,有效地除去了空白梯度色谱图中的杂质峰,提高了梯度洗脱的分离重现性。该方法对开展梯度洗脱有实用价值。     

基于离子液体的静态顶空气相色谱技术

综述了近年来离子液体作为顶空溶剂静态顶空气相色谱法或气相色谱质谱法联用技术在挥发性成分的样品前处理中的研究进展,主要是其在药物、食品、空气等样品中的挥发性成分包括有机溶剂残留、活性成分、基因毒性杂质、农药残留等的顶空分析研究与应用和有机溶剂残留顶空分析的理论研究,并探讨了离子液体作为顶空溶剂的静态顶空气相色谱技术存在的问题和未来发展方向。     

UltiMate 3000 DGLC双三元液相色谱的反梯度补偿技术

反梯度补偿技术是指在色谱柱后进入检测器前加入另一与分析时溶剂组成相同但比例相反的溶剂,使进入检测器的有机溶剂浓度保持不变,从而使雾化条件更加稳定一致,提高检测效果。当使用基于雾化机理的检测器(如电雾式检     

长效氧化铝柱的研制及评价

]使用国产中性氧化铝经磨细、沉降筛选后可以制备成高效液体色谱柱：对苯、萘、苊及菲等化合物的分离度可以用氧化铝的含水量来控制。为克服长期存在的氧化铝色谱柱寿命短、活性易变的缺点,实验测定了不同溶剂中含水量与氧化铝含水的等温吸附曲线;并在此基础上,采用等水溶剂阶梯梯度洗脱法,可以良好地分离不同环数的芳烃,并保持柱性能长期不变。     

微电脑控制的高效液相色谱梯度淋洗装置

高效液相色谱对复杂样品进行分析时,往往会遇见样品中各种物质的保留时间分布很广的现象。溶剂梯度淋洗技术为解决这一问题开辟了一条有效的途径。溶剂梯度淋洗可用二个恒流泵来实现,其中一个输送强溶剂,另一个输送弱溶剂,并使其混合起来,在分析过程中,强溶剂流速不断提高,弱溶剂流速不断降低。目前有两种方法可用于控制泵的流速:一是用数字脉冲电路,但它的梯度淋洗时间不长,且只能进行线性梯度淋洗,可供实验选择的条件相当有限;二是用微电脑进行梯度淋洗控制,能进行任意长短时间和形状的梯度淋洗,这为高效液相色谱分离条件的最优化创造了有利条件。     

大口径毛细管气相色谱检查药物中残留溶剂的方法研究

 以药物合成中常用的 16种有机溶剂为研究对象 ,建立了用大口径毛细管柱检查残留有机溶剂的气相色谱法 ,并考察了不同极性的色谱柱及不同提取溶剂对分离与检测的影响。实验表明 ,根据原料药合成中可能存在的残留溶剂 ,选用适当的提取溶剂 ,采用大口径毛细管气相色谱法检查 ,可获得较满意的结果。     

锂离子电池电解质盐LiBF4的制备新方法及表征

详细介绍了一种锂离子电池电解质盐LiBF4的全新制备方法乙腈溶剂法。制备过程采用氟硼酸钠加热分解产生BF3,BF3和LiF在CH3CN溶剂中反应,经过滤冷却结晶得到产物。其中中间产物BF3的制备过程采用GC-MS-SIM法监测,确定条件为氟硼酸钠在500℃下加热3h。粗品LiBF4经有机溶剂提纯后,通过红外和XRD检测手段定性,用原子吸收和离子色谱检测手段定量,证明产物LiBF4杂质含量少,并通过热分析证实其热稳定性优于LiPF6,整套实验方法优势明显。     

胰岛素反相制备色谱的方法开发

以胰岛素反相制备色谱方法的开发和优化为目标,通过考察色谱保留参数、峰展宽及样品流出曲线的浓度分布等色谱参数,对流动相梯度、色谱填料、载样量等色谱条件进行了优化,并建立了胰岛素制备色谱峰参数的描述方法。结果表明,所建立的方法可快速筛选出最适于胰岛素分离的色谱条件(包括流动相梯度及分离填料),即流动相中的强洗脱溶剂(有机相)需采取缓梯度窄区间的变化条件,筛选出的分离填料需具备峰向两侧展宽且展宽程度较小、样品最高浓度居中分布的特点。将方法用于实际胰岛素粗品的纯化制备,获得了杂质去除效果好、胰岛素纯度高的产品。该法为胰岛素反相色谱纯化制备方法的快速建立提供了指导,具有较强的实用价值,同时为发展大分子化合物的制备色谱方法提供了参考。     

梯度液相色谱中梯度曲线变形对色谱峰宽的影响

在梯度液相色谱中,溶剂混合以及轴向扩散等因素会使梯度曲线发生变形,而这在阶梯梯度以及高斜率的线性梯度中表现得尤为明显。本文探讨了这种梯度曲线变形对色谱峰宽的影响。首先以C18色谱柱为固定相,甲醇-水为流动相,联苯和苯乙酮为样品,测得不同线性梯度和阶梯梯度条件下的色谱峰。然后以205 nm为检测波长,记录相应条件下未接色谱柱时甲醇的响应值,得到柱入口处的梯度曲线。接着根据所设定的梯度条件以及柱入口处测得的梯度曲线,分别计算相应情形中色谱峰宽的理论值,将其与实验值进行了比较。研究结果表明,梯度曲线的变形会对色谱峰宽产生影响。当将这种影响考虑在内后,理论值与实验值更为吻合。     

色谱/质谱法鉴定回收氯代烷烃中的杂质组分

在生产头孢霉素过程中要使用大量氯代烷烃(二氯甲烷、1,2-二氯乙烷),由于这些溶剂比较昂贵,又因为生产过程中带进杂质,影响溶剂的回收,所以鉴定其杂质组成,对制定回收工艺实为必要。本文简述了GC/MS法鉴定溶剂1,2-二氯乙烷中杂质组分的过程。 实验部分 (一)溶剂的前处理 分别用酸性和碱性水洗涤溶剂,以除去溶剂中的无机杂质。 (二)CC/MS条件 1.GC部分 色谱仪:Varian 3700型色谱仪;色谱柱:SE-54毛细管柱,长25m,内径0.25mm;汽化室温度:120℃;柱温:40℃(?)100℃。     

The influence of organic sample solvents on the separation efficiency of basic compounds under strong cation exchange mode

This study investigated the influence of organic sample solvents on separation efficiency of basic compounds under strong cation exchange (SCX) mode. The mixtures of acidic aqueous solution and organic solvent such as acetonitrile, ethanol, methanol and dimethyl sulfoxide (DMSO) were tested as sample solvents. For later-eluting analytes, the increase of sample solvent elution strength was responsible for the decrease of separation efficiency. Thus, sample solvents with weak elution strength could provide high separation efficiencies. For earlier-eluting analytes, the retention of organic sample solvents was the main factor affecting separation efficiency. Weakly retained solvents could provide high separation efficiency. In addition, an optimized approach was proposed to reduce the effect of organic sample solvent, in which low ionic solvent was employed as initial mobile phase in the gradient. At last, the analysis of impurities in hydrophobic drug berberine was performed. The results showed that using acidic aqueous methanol as sample solvents could provide high separation efficiency and good resolution (R > 1.5).     

Retention prediction of a set of amino acids under gradient elution conditions in hydrophilic interaction liquid chromatography

The analysis of amino acids presents significant challenges to contemporary analytical separations. The present paper investigates the possibility of retention prediction in hydrophilic interaction chromatography (HILIC) gradient elution based on the analytical solution of the fundamental equation of the multilinear gradient elution derived for reversed‐phase systems. A simple linear dependence of the logarithm of the solute retention (ln k) upon the volume fraction of organic modifier (φ) in a binary aqueous‐organic mobile is adopted. Utility of the developed methodology was tested on the separation of a mixture of 21 amino acids carried out with 14 different gradient elution programs (from simple linear to multilinear and curved shaped) using ternary eluents in which a mixture of methanol and water (1:1, v/v) was the strong eluting member and acetonitrile was the weak solvent. Starting from at least two gradient runs, the prediction of solute retention obtained under all the rest gradients was excellent, even when curved gradient profiles were used. Development of such methodologies can be of great interest for a wide range of applications.     

Elution mechanism of polypeptides in reversed-phase liquid chromatography based on the critical threshold of organic solvent to induce abrupt change in adsorption capacity to the column packing

Adsorption capacity of polypeptides to the column packing in a solution containing multiple organic solvents was found to be expressed by means of an fn value, which is the sum of the ratios of the content of each organic solvent in the solution to the critical content of each organic solvent to cause abrupt change in the adsorption capacity, and to change abruptly at the point where the fn value becomes 1. Additionally, our results indicate that each polypeptide is eluted by the eluent containing a specific organic solvent content regardless of gradient elution rate in reversed-phase liquid chromatography, and that total organic solvent content in the eluent containing polypeptides is equal to the critical content. Considering the power law relationship between the retention times and the gradient elution rates, our results suggest that the elution of each polypeptide in reversed-phase liquid chromatography is mainly controlled by abrupt change in the adsorption capacity induced by change in the organic solvent content of the eluent during a gradient elution process, and that the abrupt change repeats across the critical threshold while a polypeptide moves through the column, and as a result, each polypeptide is concentrated in the eluent with the critical threshold.     

Separation and determination of metals as complexes of 1-nitroso-2-naphthol-6-suiphonic and 2-nitroso-1-naphthol-6-sulphonic acids. II. Liquid chromatography on c18 bonded and copolymer stationary phases

An ion-pair Chromatographic system for the separation of copper(II), palladium(II), iron(III) and cobalt(III) as ion-associates of their l-nitroso-2-naphthol-6-sulphonate and 2-nitroso-l-naphthol-6-sulphonate anionic complexes with organic ammonium compounds and inorganic cations has been studied. Isocratic and gradient elution methods were used, and the effects of column material, organic and aqueous modifiers, and pH of the eluent on the retention were examined. The elution time for the metal complex anions depends on the eluent, the proportion of organic solvent in the mobile phase, the pH of the eluent and the extraction coefficient of the compounds. The compounds were identified photometrically with a diode-array detector at wavelengths of 229, 254, 260, 298, 320 and 400 nm. The detection limits for the metals are at the ng/ml level.     

Direct extraction of urinary analytes from undeveloped reversed-phase thin layer chromatography plates using a solvent gradient combined with on-line electrospray ionisation ion mobility-mass spectrometry

The direct extraction of urinary analytes deposited on reversed-phase thin-layer chromatography (RP-TLC) plates is demonstrated using a solvent gradient extraction procedure without prior chromatographic development. The surface sample probe TLC-MS interface used for the gradient extraction is compared to direct loop injection into the electrospray ion source for biofluid profiling. The gradient elution is shown to enhance ion intensities, as urinary salts are eluted in aqueous formic acid in the early part of the gradient reducing ion suppression. The retention of urinary components on the C18 RP-TLC plate was confirmed by monitoring analyte responses with, and without, an aqueous wash phase prior to the solvent gradient extraction. The use of gradient elution allows fractionation of the complex biological matrix as a result of differential retention of urine components on the undeveloped RP-TLC plate. The direct gradient analysis of TLC plates has also been combined with ion mobility-mass spectrometry to further resolve the complex urinary profile and identify co-eluting compounds.     

Micellar and aqueous‐organic liquid chromatography using sub‐2 μm packings for fast separation of natural phenolic compounds

The objective of the present work was to investigate the chromatographic behavior of natural phenolic compounds in micellar and aqueous‐organic LC using a short column packed with 1.8 μm particles. Firstly, the effect of ACN and SDS on elution strength and selectivity was examined by isocratic submicellar (0–30% ACN/5% 1‐butanol/1–6 mM SDS) and micellar (0–30% ACN/5% 1‐butanol/40–60 mM SDS) systems. The varied concentrations of two modifiers in the mobile phases revealed different eluting power. Then, the application of organic modifier gradient was discussed in both submicellar and micellar LC using mobile phases of 4 mM SDS/5% 1‐butanol or 50 mM SDS/5% 1‐butanol containing ACN gradient from 0 to 30%, respectively. For micellar system, the separation was found to be better in gradient than isocratic elution. Additionally, the sensitivity of aqueous‐organic LC was examined. The mobile phase was a mixture of ACN and water employing gradient elution at a flow rate of 0.5 mL/min, with analysis time below 9 min. It was found that separation efficiency was significantly better compared with micellar LC. Besides, the aqueous‐organic LC has been applied to separation of various phenolic compounds in Yangwei granule or Radix Astragali samples.     

Development of a solid phase extraction procedure for HPLC-DAD determination of several angiotensin II receptor antagonists in human urine using mixture design

The optimisation of a solid phase extraction procedure involves several variables whose influence has been widely studied. However, in most cases, only process variables are taken into account. In this work, the influence of those process variables together with the fact of using mixtures of solvents during the elution step of the solid phase extraction of four angiotensin II receptor antagonist drugs has been studied. Since the influence on the extraction efficiency of several process variables were simultaneously tested, a D-optimal design was constructed. The composition of the elution solvent (a mixture of methanol, acetonitrile, ethanol and acetone at different proportions from 0 to 100% each solvent), the percentage and pH of the buffer solution added to the urine samples at the beginning of the extraction procedure; the percentage of the organic component and the volume of the washing solution, the drying time and the volume of the elution solvent were the studied variables. The chromatographic separation was carried out by gradient elution mode with 0.026% trifluoroacetic acid (TFA) in the organic phase and 0.031% TFA in the aqueous phase using an Atlantis dC18, 100 mm × 3.9 mm I.D. chromatographic column at a flow rate of 1 mL/min and a column temperature of 35 ± 0.2 °C. For detection a diode array detector set at 232 nm was used. The extraction procedure for spiked human urine samples was developed using C8 cartridges, phosphate buffer pH 6.8 as conditioning agent, a drying step of 10 min, a washing step with methanol-phosphate buffer (20:80, v/v) and methanol as eluent. Recovery percentages obtained: 84% for eprosartan, 74% for telmisartan, 74% for irbesartan and 89% for valsartan allow the determination of these drugs concentration levels in urine.     

Theoretical Aspects of Gradient Reversed-Phase High Performance Liquid Chromatography of Styrene – Butylacrylate Block Copolymers

Butylacrylate – styrene co-polymers prepared by atom transfer radical polymeratization were separated on an octadecyl silica column by gradient elution with tetrahydrofuran in water, up to the molar masses 10,000. In reversed-phase high performance liquid chromatography (RP-HPLC), the retention of macromolecules is affected very significantly even by change of a few tenths of per cent of the organic solvent in the aqueous-organic mobile phase. Therefore, gradient elution was used for the determination of the parameters of the equations describing the effects of the mobile phase on the retention behaviour of synthetic polymers. The retention parameters of homopolymers and copolymers were calculated from the gradient data using two retention models. The retention behaviour of the copolymers was described using the experimental gradient retention data for homopolymers.     

Comparison between the isocratic and gradient retention behaviour of polypeptides in reversed-phase liquid chromatographic environments.

The isocratic and gradient elution behaviour of beta-endorphin and glucagon, two polypeptides known to exist in amphipathic alpha-helical conformations in lipophilic environments, have been examined under reversed-phase high-performance liquid chromatographic (RP-HPLC) conditions with low pH, aquo-acetonitrile mobile phases. The effects of changes in the volume fraction, psi, of the organic solvent modifier and temperature, T, on the magnitudes of the S and log k(o) values of these two polypeptides, obtained from the plots of logarithmic capacity factor (log k') vs. psi using isocratic elution conditions have been determined. These data have then been compared to the corresponding S and log k(o) values, obtained from the plots of logarithmic median capacity factor (log k) versus the median volume fraction of the organic solvent modifier (psi) derived from the linear gradient elution data, using the same n-butyl silica sorbent and related aquo-acetonitrile mobile phase conditions. As apparent from these studies, substantial differences occur in the temperature-dependent trends and magnitudes of the corresponding S and S values, or the log k(o) and log k(o) values, when these parameters are derived from experimental data acquired by these two different elution methods. Moreover, when gradient elution data for beta-endorphin and glucagon are utilised, the extrapolated values of the intercept and slope of the plots of log k vs. 1/T (corresponding to an apparent change in the median enthalpy of association, deltaH(o)assoc, or an apparent change in the median entropy of association, deltaS(o)assoc) substantially deviated from the values obtained for the thermodynamic parameters, deltaH(o)assoc and deltaS(o)assoc, derived from the log k' vs. 1/T plots using the corresponding isocratic data. These findings thus have important implications for biophysical and thermodynamic investigations when gradient elution data are employed to assess the molecular basis of the interaction of polypeptides with non-polar ligates.