High performance liquid chromatography , lead analysis

High performance liquid chromatography (Chapter 4) which is displacing conventional column chromatography (Chapter 6) has found numerous applications in the analysis of organic compounds, also metal organic compounds of mercury, tin, arsenic, manganese copper and lead. It has fewer applications in the determinations of anions and cations. 

J. Szpunar, P. Pellerin, A. Makarov, T. Doco, P. Williams, B. Medina, R. Lobinski, Speciation analysis for biomolecular complexes of lead in wine by size-exclusion high-performance liquid chromatography D inductively coupled plasma mass spectrometry, J. Anal. Atom. Spectrom., 13 (1998), 749D754. 

Reversed-phase high-performance liquid chromatography (RP-HPLC) is the usual method of choice for the separation of anthocyanins combined with an ultraviolet-visible (UV-Vis) or diode-array detector (DAD)(Hebrero et al., 1988 Hong et ah, 1990). With reversed-phase columns the elution pattern of anthocyanins is mainly dependent on the partition coefficients between the mobile phase and the Cjg stationary phase, and on the polarity of the analytes. The mobile phase consists normally of an aqueous solvent (water/carboxylic acid) and an organic solvent (methanol or acetonitrile/carboxylic acid). Typically the amount of carboxylic acid has been up to 10%, but with the addition of a mass spectrometer as a detector, the amount of acid has been decreased to as low as 1 % with a shift from trifluoroacetic acid to formic acid to prevent quenching of the ionization process that may occur with trifluoroacetic acid. The acidic media allows for the complete displacement of the equilibrium to the fiavylium cation, resulting in better resolution and a characteristic absorbance between 515 and 540 nm. HPLC separation methods, combined with electrochemical or DAD, are effective tools for anthocyanin analysis. The weakness of these detection methods is a lack of structural information and some nonspecificity leading to misattribution of peaks, particularly with electrochemical... 

Problems are often found in many analytical methods due to the complex nature of the mixture and the lack of adequate detection means, thus leading to poor quantitation techniques. For the routine separation of a broad range of surfactants, high-performance liquid chromatography (HPLC) appears to be the most cost-effective [7-18]. Ultraviolet (UV) and fluorescence detectors are commonly used in HPLC analysis of surfactants because of their compatibility with separation techniques requiring gradient elution. However, these detectors have two inherent limitations (a) the detector response is dependent on molecular structure (i.e., degree of aromaticity and type of substitution) and (b) only species with a chromophore can be detected. To overcome those limitations, postcolumn reaction detectors, based on extraction of fluorescent ion pairs, were introduced for on-line detection of alkylsul-... 

The increasing need for identification of low-level (0.1%) impurities has lead to the development of specific methods for microgram amounts of analyte and for mixture analysis, and now key among these methods is the hyphenation of NMR to separation techniques such as high performance liquid chromatography (HPLC). LC/NMR is now such a widespread technique that a separate section is devoted to this topic. 

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