Preconcentration of heavy metal impurities from water on chromatographic paper

An attempt is made to employ the previously proposed method for preconcentration of nonvolatile impurities as a narrow zone on a TLC plate or on chromatographic paper for extraction of heavy metals from potable water. The method is based on vigorous evaporation of a volatile matrix (water) induced by a stream of hot air. The degree of preconcentration was determined using ICP MS analysis for lead, cobalt, and zinc. The concentrations of impurities increased by a factor of more than 200 over a period of 20–30 min. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1399–1400, August, 2000.     

A review of advances in two-dimensional thin-layer chromatography

Although there are many simple thin-layer chromatography (TLC) separations, many more are complex and involve more than a few components, that means having to use special high-performance TLC (HPTLC) plates or microspotting or banding devices to increase its resolving power if developing in only one direction. However, adding a second development to perform two-dimensional TLC (2D TLC) allows even better resolution of complex samples. This is because different modes of chromatography are being invoked by the use of one stationary phase with two mobile phases, bilayer plates, graft TLC, or multidimensional TLC. This paper is a review of recent applications that have benefitted from using 2D TLC in its various forms. They were chosen for their variety of sample types as well as the unique choices of plates and/or mobile phases made by the researchers to yield improved separations.     

固相微萃取-气相色谱联用技术测定柠檬酸中的有机挥发性杂质

利用顶空固相微萃取．气相色谱联用技术(HS-SPME-GC)，以100μm聚二甲基硅氧烷(PDMS)萃取头分析柠檬酸中的5种有机挥发性杂质，并对萃取温度、吸附时间、解吸时间和盐析作用进行了研究。结果显示，该方法具有较好的精密度和较宽的线性范围，样品加标回收率92．4％-103．5％，检出限完全满足美国药典USP23对柠檬酸中有机挥发性杂质的限量要求。     

固相微萃取-气相色谱法测定食品添加剂中有害有机挥发杂质

建立了固相微萃取（SPME）-气相色谱法（GC）测定食品添加剂中有害有机挥发杂质：二氯甲烷、三氯甲烷、苯、三氯乙烯和1、4-二n恶烷的方法。以聚二甲基硅氧烷（PDMS）涂层的萃取纤维萃取糖精钠、柠檬酸、苯甲酸钠溶液中的待测组分。以HP-5毛细管柱为分离柱，火焰离子化检测器（FID）定量测定。优化了固相微萃取条件：萃取纤维、萃取方式、萃取温度、平衡时间、pH及电解质浓度等。在优化的试验条件下，进行了方法的检出限、精密度、回收率试验。5种组分的回收率在97．3％～103．9％之间。     

Preconcentration of samples in sandwich tanks for continuous thin-layer chromatography

It is demonstrated that horizontai sandwich tank with two cover plates can be used to preconcentrate sample solutions. Narrow sharply-defined starting zones are obtained just outside the smaller cover plate when the series of spots of the sample solution are applied on the thin layer and predeveloped with a volatile solvent. After evaporation of the solvent, the whole area of the TLC-plate is covered with two plates and developed with a suitable solvent.     

Optimization of reversed-phase ion-pair chromatography by over-pressurized thin-layer chromatography III. Over-pressurized thin-layer chromatography using 10-camphor sulfonic acid as ion-pair reagent

Summary The use of over-pressurized thin-layer chromatography in ion pair system using acidic type pairing reagent has been studied. The most important aspect when reversed phase ion-pair TLC system is used to apply a suitable procedure for pre-treatment of the sorbents. Because of the acidic type of ion pair reagents cannot be bounded to the surface of the layer by immersion or pre-development with the reagent solution, double coating technique was used for the pre-treatment, the plate was firstly immersed in an ethanolic solution of cetrimide, then the immersion has been repeated by an ethanolic solution of acidic ion pair reagent. The necessary coating of the sorbents can be achieved by this technique. To find the optimal conditions for reversed phase ion pair TLC separation of organic amines, 10-camphor sulfonic acid as reagent, different aliphatic, aromatic amines and diamines and heterocyclic nitrogen compounds, respectively as model compounds were selected. The dependence of the selectivity and efficiency of the separation on the sorbents, on the concentrations of reagents (cetrimide and camphor sulfonic acid) applied for both immersion and in the eluent were investigated in detail. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Displacement and spacer displacement chromatography. Alteration of spot profile in displacement thin-layer chromatography

Summary Migration of spots in displacement development was investigated using a planar stationary phase. The effects of the presence or absence of the additive substances in the carrier were demonstrated when these compounds also played a role in the competition for the binding sites of the stationary phase; however, they were not members of the displacement train.In the case of displacement chromatography, compounds A+B are well separated but located very closely to each other. Using a spacer (C) in the sample, the peaks or spots of A and B are aparted by C and their virtual separation is increased.When compounds A+B were displaced by each other as well as by the displacer, the presence of the additive compound C in the carrier (carrier-spacer) can transfer an otherwise displaced component (A) into the so-called overloaded elution region of the chromatogram. At the same time the additive compound C does not unconditionally reduce the performance of displacement chromatography.Presented at the 17th International Symposium on Chromatography, September 25–30, 1988, Vienna, Austria.     

Complexation of nitrostyrenes with soluble β-cyclodextrin polymer studied by reversed-phase thin-layer chromatography

Cyclodextrin complexation decreases the apparent lipophilicity of hydrophobic guest molecules. A higher complex stability results in a larger decrease of lipophilicity as determined by reversed-phase thin-layer chromatography. The method was applied to study the complex formation of 33 nitrostyrene derivatives with a water soluble cross linked -cyclodextrin polymer (weight average molecular weight: 4300). The substituents in thepara position of the benzene ring had a higher impact on the complex stability than those in themeta andortho positions. The substituents on the alkyl side chain influenced the complex stability to the same extent as those on the benzen ring.     

Sample stacking for determination of aromatic acid impurities by microemulsion electrokinetic chromatography

In this study, a sample stacking step coupled with microemulsion electrokinetic chromatography (MEEKC) was used to detect and analyze nine aromatic acids (benzoic acid (BA), isophthalic acid (IPA), terephthalic acid (TPA), p-toluic acid (p-TA), 4-carboxylbenzaldehyde (4-CBA), trimesic acid (TSA), trimellitic acid (TMA), o-phthalic acid (OPA), and hemimellitic acid (HMA)) which are common impurities produced during aromatic acid synthesis. First, the presence of both acid and water plugs at the front of the capillary improved the reproducibility in retention time and peak intensity of the tested analytes in the stacking method. Second, the pH and the electrolyte type of acidic plug and sample matrix were found to be the predominant influences on the aromatic acid stacking. The detection limits of these aromatic acids were reduced to the range of 0.00007-0.00032 μg mL⁻¹ by this optimal sample stacking step. This proposed on-line concentration MEEKC method was able to detect trace levels of aromatic acid impurities in commercial aromatic acid products that were not previously possible by the normal MEEKC method. Furthermore, these results in comparison with our previous studies on sample stacking MEEKC method indicated that all acidic species were concentrated by this simple stacking procedure. The sensitivity enhancement, however, was highly dependent on the types of functional groups present in the structures of analytes, and the enhancement was in the order of first the compounds carrying both carboxy and hydroxy groups (e.g. phenolic acid), followed by carboxylic acid compounds (e.g. aromatic acid), and then phenol compounds (e.g. polyphenol).     

万古霉素及其杂质的亲水作用色谱分析

目前,万古霉素色谱分析方法主要为反相色谱法,该法分离万古霉素及其杂质时,存在极性选择性不足以及所使用的流动相体系与质谱兼容性差等问题。基于亲水作用色谱(HILIC)对糖肽类物质的色谱保留和极性选择性,本文选取万古霉素及其常见杂质为对象,考察了HILIC固定相、流动相组成比例、缓冲盐添加剂浓度和pH值等色谱条件,对万古霉素及其主要杂质进行了HILIC分离方法研究。确立了以Click XIon色谱柱为固定相,以甲酸铵为流动相添加剂的亲水作用色谱条件,实现了万古霉素及主要杂质的分离,为万古霉素类化合物的分离提供了新的途径。     

气相色谱法检测工业用乙二醇纯度及杂质

以Rtx-624色谱柱（30 m×0.32 mm×1.8 μm）为分析柱进行分析，采用校正面积归一化法，建立了检测工业用乙二醇纯度及其中有机杂质的气相色谱分析法。该法可检测传统乙烯法制得的乙二醇中固有杂质二乙二醇、三乙二醇和1，3-二氧杂烷-2-甲醇，同时也适用于检测草酸酯加氢法制得的乙二醇中的新杂质（1，2-丁二醇、1，4-丁二醇、1，2-己二醇、碳酸乙烯酯等）。结果表明，该法具有良好的重复性和较高的检测灵敏度，检出限最低可达0.0002%（质量分数），回收率在91.2%~105.4%之间。该法在乙二醇生产控制、产品检测、市场贸易等过程中具有良好的应用前景。     

Optimization of a scanning densitometer for fluorescence detection in high performance thin-layer chromatography

Conditions for maximizing resolution and signal-to-noise ratios in fluorescence scanning densitometry of separations obtained by high performance thin-layer chromatography are described. Resolution was found to be independent of most instrument parameters with a small decrease observed at wide slit widths. Signal was found to be markedly dependent on experimental parameters such as slit width, slit height, sensitivity setting, and the time constant of electronic filters. For recording chromatograms a slit width of 1.00 mm, a slit height slightly greater than the spot diameter, a low sensitivity setting (50 mV), electronic filtering, and a scan rate of 24 or 48 mm min^?1 are commensurate with minimum recording time and maximum sample detectability without incurring a significant decrease in resolution.     

Validated stability-indicating densitometric thin-layer chromatography: application to stress degradation studies of minocycline

A simple, stability-indicating high-performance thin-layer liquid chromatographic (HPTLC) method for analysis of minocycline was developed and validated. The densitometric analysis was carried out at 345 nm using methanol-acetonitrile-isopropyl alcohol-water (5:4:0.5:0.5, v/v/v/v) as mobile phase.The method employed TLC aluminium plates pre-coated with silica gel 60F-254 as the stationary phase. To achieve good result, plates were sprayed with a 10% (w/v) solution of disodium ethylene diaminetetraacetic acid (EDTA), the pH of which was adjusted to 9.0. Compact spots of minocycline were found at R_f = 0.30 ± 0.02. For proposed procedure, linearity (r = 0.9997), limit of detection (3.7 ng spot⁻¹), recovery (99.23-100.16%), and precision (% R.S.D. ≤ 0.364) was found to be satisfactory. The drug undergoes acidic and basic degradation, oxidation and photodegradation. All the peaks of degradation products were well resolved from the pure drug with significantly different R_f values. The acidic and alkaline degradation kinetics of minocycline, evaluated using this method, is found to be of first order.     

The use of vacuum in thin-layer chromatography with a forced flow of the mobile phase on plates with covered polymer layer

A new version of TLC with a forced flow of the mobile phase has been suggested. The variant involves the use of a TLC plate, the sorption layer on which is covered with a polymer film, and evacuation as an additional driving force for the mobile phase. The advantages of the new method were analyzed; the velocity coefficient of the movement of the mobile phase front was found to be linearly dependent on the rarefaction at the end of the plate.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1143–1146, May, 1996.     

顶空气相色谱法测定化妆品中15种挥发性有机溶剂残留

建立了化妆品中15种挥发性有机溶剂残留的顶空气相色谱测定方法。样品经60 ℃、30 min静态顶空后,采用气相色谱-氢火焰离子化检测器进行检测,外标法定量。加标回收试验结果表明: 15种挥发性有机溶剂残留平均回收率为62.8%～116%,相对标准偏差均小于5%。方法的检出限为0.09～0.68 mg/kg。该方法可有效克服基体干扰,一次进样可同时分离和测定化妆品中15种挥发性有机溶剂,准确灵敏,简单快速,适用于化妆品中挥发性有机溶剂残留的检测。     

Separation of salbutamol and six related impurities by packed column supercritical fluid chromatography

Summary A rapid separation of salbutamol sulphate and six related impurities: 5-formyl-saligenin, salbutamol ketone, salbutamol bis ether, isopropyl salbutamol, desoxysalbutamol sulphate and salbutamol aldehyde, has been achieved by employing packed column supercritical fluid chromatography. The effects of temperature, pressure, additive concentration and identity on retention have been studied. The use of a basic additive is necessary in order to elute the compounds and improve the peak shape. The best results were obtained by using a diol column and a gradient of modifier (methanol with 0.5% of n-propylamine).     

棒状薄层色谱-氢火焰离子探测仪检测老化沥青的四组分

沥青老化过程中四组分(饱和分、芳香分、胶质和沥青质)会发生变化,分析沥青在老化过程中四组分的变化有助于揭示沥青的老化机理,科学指导沥青材料的工程应用。分别采用薄膜烘箱试验(TFOT)、压力老化容器(PAV)试验和紫外光(UV)老化试验对沥青进行老化,利用棒状薄层色谱-氢火焰离子探测仪(TLC-FID)检测沥青老化前后的四组分,研究了扩展液组成对沥青四组分测定结果的影响,并与溶剂沉淀及色谱柱法(Corbett法)测定结果进行了对比。通过线性拟合分析了TLC-FID法与Corbett法检测老化沥青四组分的相关性。结果表明,采用二氯甲烷配制沥青溶液,以正庚烷为第一扩展液、甲苯/正庚烷(80:20, v/v)为第二扩展液、甲苯/乙醇(55:45, v/v)为第三扩展液,并利用TLC-FID方法检测老化沥青的四组分较为合适。该方法对于沥青四组分的分析及沥青老化机理的研究具有重要意义。