Separator liquid, chromatographic

By connecting a liquid chromatograph to a suitable mass spectrometer through an interface and including a data system, the combined method of LC/MS (sometimes written HPLC/MS) can be used routinely to separate complex mixtures into their individual components, identify the components, and estimate their amounts. The technique is widely used. 

The electrospray source can be coupled directly to a liquid chromatographic (LC) column so that, as components of a mixture emerge from the column, they are passed through the source to give accurate mass data. As an example, a mixture of the peptides shown in Figure 40.8(a) was separated by LC and accurately mass-analyzed by ES. 

A sample to be examined by electrospray is passed as a solution in a solvent (made up separately or issuing from a liquid chromatographic column) through a capillary tube held at high electrical potential, so the solution emerges as a spray or mist of small droplets (i.e., it is nebulized). As the droplets evaporate, residual sample ions are extracted into a mass spectrometer for analysis. 

Chlorooctane (14 9 g, 0 I mol), potassium fluoride dihydrate (47 g, 0 5 mol), hexadecyltributylphosphonium bromide (5 1 g, 0 01 mol), and water (30 mL) are mixed in an autoclave equipped with a magnetic stirrer and heated to 160 °C (bath temperature) for 7 h After this time gas-liquid chromatographic analysis (10% Carbowax 20M on Chromosorb) shows a 95% conversion to a mixture of 1-fluorooctane (82%), octenes (6%), and 1-octanol (7%) The organic layer is separated, washed with water, washed with concentrated sulfuric acid, washed once again with water, dried over calcium chloride, and distilled to give 10 g (77%) of ] -fluorooctane... 

Current interest is, however, mainly in the coupling of HPLC and TLC, to which considerable attention has been devoted for the solution of difficult separation problems. Since Boshoff et al. (39) first described the direct coupling of HPLC and TLC, several papers (40-43) have been published describing the on-line coupling of liquid chromatographic methods and PC, usually with different interfaces, depending on the first technique applied. If PC is used as the second method, all the MD methods discussed above can be applied to increase the separating power. 

The experiment described illustrates the application of ion chromatography (Section 7.4) to the separation and determination of the following anions Br", Cl , NO3 and N02 It may be readily extended to include other anions, such as F , H2PC>4, and SO -. The experiment is based on the Waters ILC Series Ion/Liquid Chromatograph which does not require the use of a suppressor column. 

Equation (1) merely states that the general distribution law applies to the system and that the adsorption isotherm is linear. At the concentrations normally employed in liquid chromatographic separations this will be true. 

Another useful standard Is SRM 1647, priority pollutant polynuclear aromatic hydrocarbons (in acetonitrile). It can be used to calibrate liquid chromatographic Instruments (retention times. Instrument response), to determine percent recoveries, and to fortify aqueous samples with known PAH concentrations. Figure 8 Illustrates the HPLC separation and UV detection (fluorescence is also used extensively) for the 16 priority pollutants. 

Adachi, T. and Nakatsukasa, M., High-performance liquid chromatographic separation of betalains and their distrihution in Portulaca grandiflora and related species, Ztschr. Pflanzenphysiol., 109, 155, 1983. 

Hyvarinen, K. and Hynninen, P.H., Liquid chromatographic separation and mass spectrometric identification of chlorophyll b allomers, J. Ghromatogr. A, 837, 107, 1999. 

Lancaster, RE. and Lawrence, J.F., High-performance liquid chromatographic separation of carminic acid, and P-bixin, and a- and 13-norbixin, and the determination of carminic acid in foods, J. Chromatogr. A, 732, 394, 1996. 

Recently a new method was developed for the complete liquid chromatographic separation and diode array detection of standard mixtures of the 14 most frequently used synthetic colorants. Protocols for RP-HPLC - " and IP-HPLC techniques have been extensively described and the techniques were compared with micellar electrokinetic capillary chromatography, - which has been shown to be suitable for the analysis of synthetic colorants. 

Figure 9 shows the result of injecting 10 gA of the total low molecular weight fraction from GPC 1 (Column Code A2) into GPC 2 (Column Code Bl). With this column code, GPC 2 is performing as a High Performance Liquid Chromatograph (HPLC). Separation is based upon solubility (i.e. composition differences) rather than upon molecular size. Methyl methacrylate monomer was used as a reference and added to the solution injected into GPC 1. Concentrations of n-butyl methacrylate, styrene and conversion are readily calculated from the peak areas and initial concentrations. 

The strong selectivity of A A -dialkyl A-benzoylthiourea toward platinum metals has been favorably exploited to determine noble metals (Rh, Pd, Pt, and Au) in samples of ore and rocks by graphite fnmace atomic absorption spectroscopy (GFAAS) and UV detection after liquid chromatographic separation on silica HPTLC plates [23]. The results are presented in Table 14.3. 

Wise SA, Chesisr SN, Hertz HS, Hilpert LR, and May WE (1977) A chemically bonded amino-silane stationary phase for the high-performance liquid chromatographic separation of polynuclear aromatic compounds. Anal Chem 49 2306-2310. 

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