Hydroxyl groups spectrophotometric methods

The oxidation may be performed at pH 5.0 by addition of an aqueous solution of sodium metaperiodate. The reaction is allowed to proceed in the dark at 4 °C and after 24 hours the excess periodate is destroyed by the addition of ethylene glycol. The aims in periodate oxidation are to elucidate the number of neighbouring hydroxyl groups by estimating the number of moles of periodate consumed and to determine the structure of the moiety remaining after the reaction. The amount of periodate used in the reaction may be determined in several ways, including titrimetric and spectrophotometric methods. 

Although spectrophotometric detection is generally acceptable, electrochemical detection seems to be more appropriate for the analysis of -agonists, due to the presence on the aromatic part of their molecule of oxidizable hydroxyl and amino groups. This method of detection has been applied in the determination of clenbuterol residues in bovine retinal tissue with sufficient sensitivity for this tissue (478). 

Another technique which has much potential in analysis, but which to date has had only limited use, is the formation of radioactive derivatives of non-radioactive compounds for quantitation by radiocounting. A radiolabeled reagent is used to form the derivative. This approach has been of use in combination with chromatography. The advantage of this technique is that it avoids problems of sample background which are often associated with spectrophotometric methods. The 14C-methylation of carboxylic acids and the 14 C-acetylation of hydroxyl groups have been studied [39,40]. These methods are quantitative and the sensitivity is dependent on the activity of the radioactive group added to the molecules. The radioactive derivatization of lipids has been reviewed [41]. 

Study of the ECL based on Ru(bpy)3 revealed that luminescence intensity of monohydric alcohols decreased as alkyl chain length of the molecules increased while increase in the number of hydroxyl groups in a molecule leads to enhancement in limiinescence intensity for polyhydric alcohols [120]. Moreover, electrochemical redox potentials, PL, and relative ECL-FIA studies were described for polyamine dendrimers functionalized with electrochemiluminescent polypyridyl Ru(II) complexes, synthesized through the complexation of dendritic polypyridyl hgands to Ru(II) complexes [121]. The adaptability of the newly fabricated thin-layer electrochemical flow cell for amperometric and ECL measurements combined with FI method is demonstrated. This detection is followed by spectrophotometric detection for determination of bromide using the fabricated ceU [122]. 

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