Liquid chromatographic technique

F. Enri and R. W. Erei, Two dimensional column liquid chromatographic technique for resolution of complex mixtures , ]. Chromatogr. 149 561-569 (1978). 

J. A. Apffel, T. V. Alfredson and R. E. Majors, Automated on-line multi-dimensional high performance liquid chromatographic techniques for the clean-up and analysis of water-soluble samples , J. Chromatogr. 206 43-57 (1981). 

Castillo M, Domingues R, Alpendurada MF, et al. 1997. Persistence of selected pesticides and their phenolic transformation products in natural waters using off-line liquid solid extraction followed by liquid chromatographic techniques. Anal Chim Acta 353 133-142. 

The reason for this lies not least in the increasing instrumentalization and delibei automation of all those processes which were earlier particularly subject to eri (Fig. 2). Modem high performance thin-layer chromatography (HPTLC) is no Ion inferior to other liquid chromatographic techniques with respect to precision and s sitivity (Fig. 3) [6]. 

ESI-MS is the most successful method of coupling a condensed phase separation technique to a mass spectrometer. Because the input to ESI is a liquid, electrospray serves as an interface between the mass spectrometer and liquid chromatographic techniques, including SEC and CE (capillary electrophoresis). In LC-MS the flow-rate should lie in the range recommended for the HPLC pump and the mass spectrometer (typically 0.001 -l.OmLmin-1). Recent advances in (nano)electrospray technology include the development of the use of very low solvent flow-rates (30 to 1000nLmin-1) [130,131],... 

Hurst, W.J., Martin, R.A. Jr, Tarka, S.M. Jr. and Hall, G.D., Authentication of cocoa in maya vessels using high performance liquid chromatographic techniques, J. Chromatography, 466,279,1989. 

Complex polymers are distributed in more than one molecular property, for example, comonomer composition, functionality, molecular topology, or molar mass. Liquid chromatographic techniques can be used to determine these properties. However, one single technique cannot provide information on the correlation of different properties. A useful approach for determining correlated properties is to combine a selective separation technique with an information-rich detector or a second selective separation technique. 

Kilz, P., Pasch, H. (2000). Coupled liquid chromatographic techniques in molecular characterization. In Encyclopedia of Analytical Chemistry Meyers, R.A., editor. J. Wiley Sons, Chichester. 

Hydrogen donors are, however, not the only important components of solvents in short contact time reactions. We have shown (4,7,16) that condensed aromatic hydrocarbons also promote coal conversion. Figure 18 shows the results of a series of conversions of West Kentucky 9,14 coal in a variety of process-derived solvents, all of which contained only small amounts of hydroaromatic hydrocarbons. The concentration of di- and polyaromatic ring structures were obtained by a liquid chromatographic technique (4c). It is interesting to note that a number of these process-derived solvents were as effective or were more effective than a synthetic solvent which contained 40% tetralin. The balance between the concentration of H-donors and condensed aromatic hydrocarbons may be an important criterion in adjusting solvent effectiveness at short times. 

May, W. E., Wasik, S. P., Freeman, D. H. (1978a) Determination of the aqueous solubility of polynuclear aromatic hydrocarbons by a coupled-column liquid chromatographic technique. Anal. Chem. 50, 175-179. 

As can be seen in Table 3, a wide range of analytes derivatized with different labels have been detected using the POCL reaction. Most of these applications have employed flow injection or liquid chromatographic techniques. An area of growing interest is the combination of capillary electrophoresis with chemiluminescence. Several strategies have been used to detect analytes with fluorescent... 

The selection of detection techniques capable of providing detection improvements has been a principal issue of research. A wide range of methods applied to meet detection limitations in CE have been taken mainly from liquid chromatographic techniques with only minor modifications, including ultraviolet (UV) absorption, fluorescence, mass spectrometry, conductivity, and electrochemistry principles. 

Durand G, Bouvot V, Barcelo D (1992) Determination of trace levels of herbicides in estuarine waters by gas and liquid-chromatographic techniques. J Chromatogr 607(2) 319-327... 

Trace amounts of cyanide in blood cells may be determined using a liquid chromatographic technique with fluorescence detection (Sano et al. 1992). The blood cells are extracted and derivatized prior to chromatography. The detection limit is 2 ng/mL. Recovery is acceptable (>80%), and precision is good (<15%RSD) (Sano et al. 1992). 

Liquid chromatographic techniques have been frequently employed for the separation and identification of the toxic decomposition products of synthetic dyes. Thus, the amount of aromatic amines formed from azo dyes in toys has been determined. The chemical structures of the dyes included in the investigation are listed in Fig. 3.60. The dyes were... 

The efficacy of chemical and photochemical decolourization of dyes in the effluent of textile factories has been proved many times. However, in the majority of cases these methods are relatively expensive and the solid catalysator used for the oxidation sometimes presents a new problem for environmental protection. Microbiological methods are less expensive, the dyes are decomposed to small organic and inorganic molecules which can be taken up by micro-organisms as carbon and nitrogen sources. Also, in the case of microbiological decomposition of dyes, liquid chromatographic techniques can be... 

Various liquid chromatographic techniques have been frequently employed for the purification of commercial dyes for theoretical studies or for the exact determination of their toxicity and environmental pollution capacity. Thus, several sulphonated azo dyes were purified by using reversed-phase preparative HPLC. The chemical strctures, colour index names and numbers, and molecular masses of the sulphonated azo dyes included in the experiments are listed in Fig. 3.114. In order to determine the non-sulphonated azo dyes impurities, commercial dye samples were extracted with hexane, chloroform and ethyl acetate. Colourization of the organic phase indicated impurities. TLC carried out on silica and ODS stationary phases was also applied to control impurities. Mobile phases were composed of methanol, chloroform, acetone, ACN, 2-propanol, water and 0.1 M sodium sulphate depending on the type of stationary phase. Two ODS columns were employed for the analytical separation of dyes. The parameters of the columns were 150 X 3.9 mm i.d. particle size 4 /jm and 250 X 4.6 mm i.d. particle size 5 //m. Mobile phases consisted of methanol and 0.05 M aqueous ammonium acetate in various volume ratios. The flow rate was 0.9 ml/min and dyes were detected at 254 nm. Preparative separations were carried out in an ODS column (250 X 21.2 mm i.d.) using a flow rate of 13.5 ml/min. The composition of the mobile phases employed for the analytical and preparative separation of dyes is compiled in Table 3.33. 

Based on the nature of separation, the peak capacity of the separation system is much higher than in liquid chromatographic techniques. 

Wang, X. and Song, H. Determination of octanol-water partition coefficients of organic pollutants by using the dynamic coupled-column liquid chromatographic technique, Trans. Tianjin Univ, 2(l) 59-63, 1996. 

Liquid-chromatographic techniques have been useful for studying the mode of action of various polysaccharide-degrading enzymes. Rapid and quantitative, l.c. end-product analysis has been used to study the action... 

---