No abstract

Rotationally resolved electronic spectra of three different conformers of 5-methoxytryptamine were recorded in a molecular beam. 5-Methoxy substitution reduces the number of observed conformers to three compared to seven that have been reported for tryptamine. Quantum chemical calculations indicate that anti-rotamers of the methoxy-group are more stable relative to the syn-forms. Two gauche structures (Gpy(in) and Gph(in)) of the ethylamino group with respect to the indole chromophore were found to be less stable than the other seven. The lowest electronically excited state has been identified as the (1)L(b) one for all observed conformers which was confirmed by quantum-chemical calculations. Based on the comparison of rotational constants obtained from fits using evolutionary algorithms with those from calculations, the three observed conformers were determined to be the Gpy(up), Gph(up), Gpy(out) ethylamino side-chain conformations.

Hydroperoxides are formed as the primary product during lipid oxidation, being analyzed as the peroxide value to detect the degradation level of oils and fats. As an alternative to the classical titration method according to Wheeler, a 1 H-{ 31 P} decoupled NMR method is developed using triphenylphosphine (TPP) as a tagging agent. TPP reacts with peroxides to form TPP oxides. The quantification of the peroxide value is performed by comparing the amount of reacted TPP oxide and non-reacted TPP. This approach eliminates the requirement for an additional internal standard. Low-oxidized oils (peroxide value < 3 meq/kg) and high-oxidized oils with peroxide values of 150 meq/kg are precisely quantified with an relative standard deviation (RSD) of 4.90% and 0.16%, respectively. A total number of 108 oil samples are examined using the newly-developed 1 H-{ 31 P} decoupled NMR method, indicating the applicability for vegetable oils and krill oils. Practical Applications: The developed NMR method is applicable for the determination of the peroxide value in vegetable, marine and krill oils presenting a powerful alternative for the Wheeler titration method.