Liquid chromatography Subject

If maltenes are subjected to liquid chromatography (see 2.1.2.4) the components eluted by the more polar solvents are called resins. Their composition, once again, depends on the procedure used. 

Liquid chromatography is preceded by a precipitation of the asphaltenes, then the maltenes are subjected to chromatography. Although the separation between saturated hydrocarbons and aromatics presents very few problems, this is not the case with the separation between aromatics and resins. In fact, resins themselves are very aromatic and are distinguished more by their high heteroatom content (this justifies the terms, polar compounds or N, S, 0 compounds , also used to designate resins). 

Very little in the way of advances has occurred since 1971 in the applications of ultraviolet or infrared spectroscopy to the analysis of fluonnated organic compounds Therefore, only gas-liquid chromatography, liquid chromatography, mass spectrometry, and electron scattering for chemical analysis (ESCA) are discussed The application of nuclear magnetic resonance (NMR) spectroscopy to the analysis of fluonnated organic compounds is the subject of another section of this chapter... 

It is the intent of this chapter to introduce the analyst to some of the more common procedures that have been established for sample preparation. It is impossible to cover such a subject comprehensively in a single chapter and it will still be necessary for the analyst to seek support from the literature when faced with unusual samples. Fortunately, analytical LC methods have been reported in the literature for over two decades and it is highly likely that a publication exists describing a particular analysis of interest or one very similar to it. The journals that are recommended for reference are the Journal of Liquid Chromatography, the Journal of Chromatography, the Journal of Chromatographic Science, The Analyst and Analytical Chemistry. 

Using high performance liquid chromatography plus GC-MS and a compart-mental model, the absorption of p-carotene was estimated as 22% (17.8% as intact P Carotene and 4.2% as retinoids) after ingestion of a single high dose of p-carotene-d8 (40 mg) in oil by one adult subject. This value was close to the 9 to 17% values obtained in earlier human lymph cannulation studies using radioisotopes. ... 

In Chapter 31 we stated that any data matrix can be decomposed into a product of two other matrices, the score and loading matrix. In some instances another decomposition is possible, e.g. into a product of a concentration matrix and a spectrum matrix. These two matrices have a physical meaning. In this chapter we explain how a loading or a score matrix can be transformed into matrices to which a physical meaning can be attributed. We introduce the subject with an example from environmental chemistry and one from liquid chromatography. 

Crop material is homogenized with acetonitrile-water (9 1, v/v). The crop extract is centrifuged and an aliquot is rotary evaporated to a small volume. The sample is subjected to a Cig solid-phase extraction (SPE) cleanup procedure. The concentrated eluate is subjected to liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis. 

The concentrated eluate is subjected to high-performance liquid chromatography (HPLC) analysis. 

Plant materials are homogenized with methanol. Hexythiazox residue is extracted with hexane and then transferred to acetonitirile by liquid-liquid partitioning. The acetonitirile is removed by rotary evaporation and the sample is cleaned up using Florisil PR column chromatography. The concentrated eluate is subjected to high-performance liquid chromatography (HPLC) analysis. 

The remainder of this section deals primarily with selectivity optimization in isocratic liquid chromatography and with gradient elution Before entering these subjects proper, however, a discussion of the relevant chromatographic properties of solvents is in order as a framework for the intuitive selection of the preferred solvent or solvent mixtures for selectivity optimization. 

Breithaupt, D. E., P. Weller et al. (2004). Comparison of plasma responses in human subjects after the ingestion of 3R.3R -xeaxanthin dipalmitate from wolfberry (Lycium barbarum) and non-esterified 3R,3R -zeaxanthin using chiral high-performance liquid chromatography. Br. J. Nutr. 91(5) 707-713. 

Lee [73] studied the stability of miconazole on dry heating in vegetable oils. Miconazole was stable when subjected to dry heat (160 °C for 90 min) in either peanut or castor oil as determined by high performance liquid chromatography analysis. Thus, ophthalmic preparations of miconazole can be prepared in peanut or castor oil with dry heat sterilization without the loss of the drug due to degradation. The procedure also facilitates quick and easy dissolution of the drug in the oil base. 

HPLC) for phenolic acids analysis. When procedure (ii) was applied, the ion-exchange resin was separated from the methanol phase and eluted with three 40 ml aliquots of 80% methanol. The resin bead eluates were evaporated to dryness and subjected to spectrophotometry (Shimadzu UV 160 spectrophotometer) for total phenolics and high-performance liquid chromatography (HPLC) for phenolic acids analysis. 

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