Amine determination

On the basis of the obtained results simple, reliable and express methods of aliphatie amines determination in natural objeets, food stuffs and teehnologieal mixtures have been offered. 

T.J. Castilho, M. del P.T. Sotomayor, and L.T. Kubota, Amperometric biosensor based on horseradish peroxidase for biogenic amine determinations in biological samples. J. Pharmaceut. Biomed. Anal. 37, 785-791 (2005). 

Substitution patterns, especially that of the diazotized aromatic amine, determine the color of a pigment to some extent but empirical data do not lead to unambiguous conclusions as to the exact influence of a particular substituent on the shade. The problem is intricate, since the substitution pattern also has a bearing on the size and orientation of a pigment molecule and therefore on its crystal structure, including all the interactions associated with it. 

TABLE 10. Equilibrium acidities of aromatic amines determined by the H method in H2O/DMSO and pure DMSO... 

Attention should be paid to the appearance of spurious peaks in the fragmentation patterns of amines determined by GC-MS, when the analytes came into contact with methanol or ethanol as solvents. Thus, for example, Schiff bases may be formed on condensation of a primary amine with traces of formaldehyde or acetaldehyde present in the solvent. Although the peaks of such product may be unresolved in the chromatogram, they may appear as ions with mass increments of +12 or +26 in the mass spectrogram, complicating the identification of the analyte, as was the case with some amphetamine drugs99. 

A similar study was carried out using a different set of synthetic dyes. The chemical structures of the dyes are listed in Fig. 3.62. The decomposition products were separated in an ODS column (250 X 4 mm i.d. particle size 7 /tm) using an isocratic mobile phase composed of methanol-water (45 55, v/v). The flow rate was 1.2 ml/min. The contents of aromatic amines determined by spectrophotometric and HPLC methods are compiled in Table 3.24. It was established that spectrophotometry can be used for the exact determination of the amines but it is inadequate for their separation. RP-HPLC proved to be a valuable method for the analysis of this class of decomposition products [131],... 

CONTENT OF AROMATIC AMINES DETERMINED BY SPECTROPHOTOMETRIC AND HPLC METHODS... 

Several analytical techniques including capillary electrophoresis, thin layer chromatography (TLC), GC, lEC, and HPLC, have been proposed for the determination of biogenic amines in various foods. Among these, RP-HPLC is considered the most suitable one. HPLC methods used for amine determination usually involve two steps amine extraction from the matrix and analytical determination. Depending on the complexity of food matrix and the selectivity of the final analytical determination, a further purification step may be necessary prior to the analytical determination. To ensure adequate sensitivity, a derivatization step is generally required before injection [282]. 

According to some recent literature, typical conditions for biogenic amine determination are precolumn derivatization with Dnsl-Cl followed by separation on C8 or C18 column with gradient elution with mobile phases consisting of water or phosphate buffer and acetonitrile (or methanol) or postcolumn derivatization with OPA and gradient elution with mixtures of sodium acetate buffer and methanol (or acetonitrile). In the latter case, a counterion (such as hexanesulfonic or octansulfonic acid) is usually added in the mobile phase. 

A fast and simple analytical method for amine determination is still not available, but reversed-phase HPLC is usually considered the most suitable technique for this analytical purpose. 

The pathway of the Kabachnik-Fields reaction depends on the nature of the substrates. The amine and hydrophosphoryl compound form a complex in which either one of the partners may react with the carbonyl compound. Often, the basicity of the amine determines the reaction pathway. Weakly basic amines such as anilines, which can act as proton donors, favour the formation cf an imine, whereas alkylamines such as cyclohexylamines do not form imines ... 

Catechol Amines, Determination of (Weil-Malherbe). Supp. 119... 

Analysis of biogenic amines, individually or simultaneously, is important because of their potential to be applied as indicators of food spoilage or authenticity. The two main problems encountered with amine determination in food products in general, and especially in wine, are the complexity of the matrix and their low... 

The data collected by Goethals on the kp/k ratio in the polymerization of cyclic amines (determined from Eq. (153) permits to show (Fig. 16) that there is a linear relationship between In (kp/kf) and the effective volume of substituents. These volumes were calculated according to Ref. 262. Thus, although the linearity itself has little importance, this dependence is in good agreement with the discussed earlier influence of substituents on the rate constants of termination and fuopagation. 

Catecholamines. The quantitative determination of dopamine and noradrenaline in tissue samples of 0.1-10 mg at levels in the order of 0.5 pmol has been described [84]. These methods are based on extraction, formation of the pentafluorpropionyl derivatives, and the use of the homologues, a-methyidopamine and a-methylnoradrenaline as internal standards in SIM. Higher sensitivity than obtainable with fluorimetric or enzymic assays is reported [462J. Applications have been to amine determination in specific regions of rat brain [84] and to measurement of heart ventricle concentrations [463]. A combination of assays of this type with the use of synthesis inhibitors or radioisotope labelled precursors allows direct estimation of brain amine turnover in animals. 

Reduction to Amines. Place 100 mg of the unknown in a reaction tube, add 0.2 g of tin, and then—in portions—2 mL of 10% hydrochloric acid. Reflux for 30 min, add 1 mL of water, then add slowly, with good cooling, sufficient 40% sodium hydroxide solution to dissolve the tin hydroxide. Extract the reaction mixture with three 1-mL portions of ether, dry the ether extract over anhydrous sodium sulfate, wash the drying agent with ether, and evaporate the ether to leave the amine. Determine the boiling point or melting point of the amine and then convert it into a benzamide or acetamide as described under 4. Primary and Secondary Amines p. 587. 

The modified polymer was assayed for reactive amines and thiols using fluo-rescamine and 5,5 -dithiobis(2-nitrobenzoic acid) (Ellman s reagent), respectively. For amine determination, a 10-mg/mL solution of fluorescamine in... 

The activities of various alkanolamines have been examined in conjunction with the 2-(2-chlorophenyl)-4,5-diphenylimidazolyl radical and benzophenone. In the case of the former the ability of the radical to abstract a hydrogen atom from the amine determines the extent of the cure while for benzophenone it is the degree of hydrogen atom abstraction, and hence cure is the same. Polymeric and monomeric sensitisers have been compared and the influence of initiator... 

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