Phenolic acid liquid chromatography

This technique is based on the same separation mechanisms as found in liquid chromatography (LC). In LC, the solubility and the functional group interaction of sample, sorbent, and solvent are optimized to effect separation. In SPE, these interactions are optimized to effect retention or elution. Polar stationary phases, such as silica gel, Florisil and alumina, retain compounds with polar functional group (e.g., phenols, humic acids, and amines). A nonpolar organic solvent (e.g. hexane, dichloromethane) is used to remove nonpolar inferences where the target analyte is a polar compound. Conversely, the same nonpolar solvent may be used to elute a nonpolar analyte, leaving polar inferences adsorbed on the column. 

Kafil, J. B. and Last, T. A., Liquid chromatography with voltammetric detection for quantitation of phenolic acids,. Chromatogr., 348, 397, 1985. 

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. 

G. Shui and L.P. Leong, Separation and determination of organic acids and phenolic compounds in fruit juices and drinks by high-performance liquid chromatography. J. Chromatogr.A 977 (2002) 89-96. 

High-performance liquid chromatography (HPLC) techniques are widely used for separation of phenolic compounds. Both reverse- and normal-phase HPLC methods have been used to separate and quantify PAs but have enjoyed only limited success. In reverse-phase HPLC, PAs smaller than trimers are well separated, while higher oligomers and polymers are co-eluted as a broad unresolved peak [8,13,37]. For our reverse-phase analyses, HPLC separation was achieved using a reverse phase. Cl8, 5 (Jtm 4.6 X 250 mm column (J. T. Baker, http //www.mallbaker.com/). Samples were eluted with a water/acetonitrile gradient, 95 5 to 30 70 in 65 min, at a flow rate of 0.8 mL/min. The water was adjusted with acetic acid to a final concentration of 0.1%. All mass spectra were acquired using a Bruker Esquire LC-MS equipped with an electrospray ionization source in the positive mode. 

Many nonvolatile and thermally labile allelochemicals can be well separated by liquid chromatography (LC). Identification of the separated components on-line by mass spectrometry (MS) is of great value. Fused-silica LC columns of 0.22 mm ID packed with small-particle material are used in the described LC/MS system. The shape of the column end allows direct connection to a electron impact ion source of a magnetic sector mass spectrometer. Separations by LC are reported and LC/MS mass spectra are shown for monoterpenes, diterpene acids, phenolic acids and cardiac glycosides. The LC/MS system provides identification capability and high-efficiency chromatography with a universal detector. 

In the last years, the use of comprehensive liquid chromatography has been greatly increased and it has been widely used to separate and characterize various complex samples, such as biomolecules [10-15], polymers [16,17], lipids [18-21], essential oils [22], acidic and phenolic compounds [23-28], pharmaceuticals and traditional medicines [29-31], etc. Comprehensive LC has been reviewed by several authors [32-37]. 

Schieber, A., Keller, P., and Carle, R., Determination of phenolic acids and flavonoids of apple and pear by high-performance liquid chromatography, J. Chromatogr. A, 910, 265, 2001. 

Wulf, L.W. and Nagel, C.W., Analysis of phenolic acids and flavonoids by high-pressure liquid chromatography. J. Chromatogr. 116, 271, 1976. 

Lunte, C.E., Wheeler, J.F., and Heineman, W.R., Determination of selected phenolic acids in beer extract by liquid chromatography with voltametric-amperometric detection. Analyst 113,95,1988. 

Shakya, R., Navarre, D. A. (2006). Rapid screening of ascorbic acid, glycoalkaloids, and phenolics in potato using high-performance liquid chromatography. J. Agric. Food Chem., 54, 5253-5260. 

Torres, A.M., Mau-Lastovicka, T., and Rezaaiyan, R. 1987. Total phenolics and high-performance liquid chromatography of phenolic acids of avocado. J. Agric. Food Chem. 35 921-925. 

Reversed-phase chromatography is the most popular mode of analytical liquid chromatography for phenolic compounds. In most cases, the reported systems for the separation of phenolics and their glycosides in foods are carried out on reversed-phase chromatography on silica-based Cl8 bonded-phase columns. Occasionally, silica columns bonded with C8 were applied in the analysis of phenolic acid standards and coumarins (7), and C6 columns for the analysis of ferulic acid in wheat straw (8). 

Post-column derivatization of carbohydrates has been described for liquid chromatography and UV detection by heat treatment [46], acid treatment [47] and reaction with phenol-sulfuric acid [48,49]. These methods have been applied to the analysis of sugars in body fluids and in wood products. The procedures are only suitable for low-speed liquid chromatography. 

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