Hydroxy groups analytical determination

It should not be assumed that hydroxy fatty acids are biologically inactive. Hydroxy fatty acids are chemotactic and vasoactive. Such fatty acids could perturb phospholipids in membranes. For instance, cardiolipin containing hydroxy-linoleic acid does not support the electron transport coupled to ATP production of the mitochondrion. 5-Hydroxy de-canoic acid is a well-known inhibitor of the K -ATP channel. Isoprostanes, trihydroxy oxidation products of arachi-donic acid, are vasoconstrictors (76). 13-Hydroxy linoleic acid (13-HODE) is a lipoxygenase-derived metabolite that influences the thromboresistant properties of endothelial cells in culture (77). However, there is some doubt about the tme nature of these hydroxy-fatty acids generated by the cells, as there are several GSH- and NADPH-dependent pathways that can immediately reduce hydroperoxy- to hydroxy-fatty acids. Furthermore, the reduction step of the analytical method would have converted the hydroperoxy- to a hydroxy-group. Nevertheless, much work remains to be done to determine the relative contribution of hydroperoxy- and hydroxy- to the biological effects of fried fat, and in particular their role in endothelial dysfunction and activation of factor VII. There have been earlier suggestions that a diet rich in lipid peroxidation products may lead to atherosclerosis and CHD (34,78). 

The colorless, vacuum-distillable liquid [(2,2-dimethylpropanoyl)oxy]diethyl-borane (2,2-dimethylpropanoyl = pivaloyl) is a catalyst for the introduction of diethylboryl groups onto the oxygen atoms of hydroxy compounds using tri-ethylborane, Diethylborylations of hydroxy compounds have both preparative " and analytical (determination of the ethane value EZ ) uses. [(2,2-Dimethylpropanoyl)oxy]diethyIborane is itself a reagent for preparing aldol-condensation products" and for determining analytical pivalate values (PZ) of H-acidic compounds. ... 

Hydroxy derivatives or phenolics are frequent target for method development using carbon paste electrodes based either on direct oxidation of hydroxy group on an aromatic ring or on enzyme-based reactions with the final determination of the product of the enzymatic reaction involved. The reason lies both in their usual ease of oxidation and in their relatively frequent occurrence as hydroxy derivatives of aromatic hydrocarbons form the base of various biologically active organic compounds used as disinfectants, pharmaceuticals, herbicides, and pesticides. CPE and CPE modified with humic acids were used for the determination of pentachloro-phenol. With modified electrode lower determination limit was reached due to better accumulatiOTi of the analyte. Formation of a quinone-Uke compound during... 

Advances have been achieved in recent years, such as the use of CL reagents as labels to derivatize and sensitively determine analytes containing amine, carboxyl, hydroxy, thiol, and other functional groups and their application in HPLC and CE [35, 36], the synthesis and application of new acridinium esters [37], the development of enhanced CL detection of horseradish peroxidase (HRP) labels [38], the use of immobilization techniques for developing CL-based sensors [39-42], some developments of luminol-based CL in relation to its application to time-resolved or solid-surface analysis [43], and the analytical application of electrogenerated CL (ECL) [44-47], among others. 

Several lactic acid derivatives were used by Gessner et al. for the determination of the enantiomeric purity of flavor substances such as chiral alcohols from natural sources. Diastereomeric 0-acetyl-, propionyl-, and hexanoyllactic acid esters of the chiral alcohols were separated by GLC (155). A report from the same laboratories described characterization of several chiral aroma substances that are S-lactones. The lactones were hydrolyzed to the corresponding hydroxy acids, and the acid moiety was esterified to the isopropyl ester. The remaining hydroxyl group was esterified with (R)-2-phenylpropionic add chloride or [30], and the diastereomeric derivatives were separated using preparative silica gel LC. The derivatives were also separated on an analytical scale by GLC (156). 

HPLC-FD [368,369,375,376,381] and also HPLC-MS [372,382] are quite helpful chromatographic techniques for the determination of hydroxyl-PAHs. The GC method for hydroxy-PAHs requires the utilization of a time-consuming derivatization step in order to decrease the polarity of the analytes and so reduce the peak-tailing in the chromatograms [371,373,377,378]. The derivatization reaction is commonly a silylation reaction, where active hydrogens of hydroxyl PAHs are replaced by trimethylsilyl (TMS) groups. The most... 

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