High-performance liquid chromatography-diode array detector analysis

GC—gas chromatography HCA—hierarchical cluster analysis HELP—heuristic evolving latent projections HHM—horse heart myoglobin HPLC—high performance liquid chromatography HPLC-DAD—high performance liquid chromatography-diode array detector... 

In the last twenty years, many of the developed and validated high performance liquid chromatography methods with conventional diode array or fluorescence detectors (DAD, FLD) were improved and substituted by new hyphenation with mass spectrometric instrumentation and/or NMR, especially for the analyses of raw materials derived from Natural sources. The main goal of this coupling is achieved by improvement of selectivity and sensitivity of new instrumental configurations [7], Furthermore, with these configurations it is possible to obtain, in only one analysis, the complete chemical structure elucidation, identification and quantification of targeted compounds. 

R. A. de Zeeuw, J. P. Franke, and M. Bogusz, High performance liquid chromatography with a multichannel diode-array spectro-photometric detector in systematic toxicological analysis. In Analytical Methods in Forensic Chemistry (M. H. Ho, ed.), Ellis Horwood, New York, 1990, p. 212. 

Zavitsanos, P., and Goetz, H. (1991). The practical application of diode array UV-visible detectors to high-performance liquid chromatography analysis of peptides and proteins. In High-Performance Liquid Chromatography of Peptides and Proteins Separation, Analysis,... 

Quantitahve analysis of reaction mixtures was performed by high-performance liquid chromatography (HPLC) and a diode array ultraviolet detector, as reported elsewhere [5, 6, 17]. 

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... 

High-performance liquid chromatography is performed using a Hewlett-Packard 1090 chromatograph equipped with a ternary-solvent delivery system, an autoinjector with a 0 -20- u.L injection loop, an oven compartment, and a diode-array UV detector. An ELS detector (Alltech Associates, Deerfield, IL) is connected in series to the UV detector. Hexane, 2-propanol, and water were used for the analysis of nonionic surfactants. Water and tetrahydrofuran (THF) are used for the analysis of anionic surfactants. No preliminary sample preparation is used other than dilution. The nonionic surfactants are diluted 1 40 (v/v) with hexane. The anionic surfactants (alkyl ether sulfates and synthetic and petroleum sulfonates) are diluted 1 20 (v/v) with water-THF (50 50). The calcium sulfonate surfactants were diluted 1 20 (v/v) with a THF-38% hydrochloric acid solution of pH 1. Hydrochloric add is required to prevent salt precipitation by converting any excess water-insoluble caldum carbonate into water-soluble calcium chloride. All diluted samples are... 

With high-performance liquid chromatography (HPLC), this kind of analysis may be performed on-line by use of a diode array detector, i.e., a detector that measures absorbance over a range of wavelengths simultaneously so that a UV spectrum can be acquired from every point on the chromatogram. Alternatively, material corresponding to various peaks can be collected and their UV absorbance measured individually in a UV spectrophotometer. 

Zhang, L., Xu, L., Xiao, S.-S. et al. (2007). Characterization of flavonoids in the extract of Sophora Jlavescens Ait. by high-performance liquid chromatography coupled with diode-array detector and electrospray ionization mass spectrometry. Journal of Pharmaceutical and Biomedical Analysis, 44, 1019-1028. 

High-performance liquid chromatography (HPLC) is the most suitable technique to determine phenolic compounds in water using UV or diode-array detection (DAD) [23-29] or electrochemical detection (ECD) [30-33] but, although amperometric detection is more sensitive than UV detection, a preconcentration step is necessary in both cases to achieve the low levels allowed in real samples. LC nowadays is often the choice over GC, as it is more suitable for aqueous samples and as no derivatization step is needed for phenolic compoimds. The online coimection between SPE and the HPLC column is fairly straightforward this approach appears very suitable for the analysis of these compounds. However, the conventional ultraviolet (UV) detector is much less sensitive than most of... 

Abbreviations DAD, diode array detector FIC, flow injection chromatography FIA-SPE-MEKC, flow injection analysis-solid phase extraction-micellar electro kinetic chromatography HPLC-FI-CH, high performance liquid chromatography-flow injection-chemiluminescence FI-CH, flow injection-chemiluminescence detection FIPCE, high performance capillary electrophoresis LOD, limit of detection LOQ, limit of quantitation SIC, sequential injection chromatography. 

Note A amperometry BI bead injection CL chemiluminescence F fluorescence FAT flow analysis technique HPLC/DAD high-performance liquid chromatography with diode array detector LOD detection limit MCFIA multicommutated flow injection analysis MPFS multipumping flow systems MSFIA multisyringe FIA P potentiometry RSD relative standard deviation SF sampling frequency SFA stopped-flow analysis SP spectrophotometry. 

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