Determination of the amino acid tryptophan and the biogenic amine tryptamine in foods by the heavy atom induced-room temperature phosphorescence methodology

Abstract

Very simple and selective methods are presented to determine the amino acid tryptophan (Trp) and the biogenic amine tryptamine (Tryp), both compounds with an indole-type molecular structure by the methodology named Heavy Atom Induced-Room Temperature Phosphorescence (HAI-RTP) which constitutes the first time that HAI-RTP has been used to detect compounds with non-naphthalenic structures in their molecules. Different variables affecting the phosphorescence signal (heavy atom perturber and sodium sulfite concentration) were carefully studied. The analytical curves give a linear dynamic range of 15-100 ng ml(-1) and a detection limit of 4 ng ml(-1) for Trp and 94-400 ng ml(-1) and 28 ng ml(-1) for Tryp. The methods have been successfully applied to the analysis of complex food matrices such as the presence of tryptophan in yoghurt and tryptamine in bottled beer. A single alkaline hydrolysis to release Trp from yoghurt proteins and two methods for extracting Tryp from beer samples are proposed and optimised. A total Trp content of 374 mg of Trp per kg of yoghurt was quantified by the standard addition method of calibration and a recovery of 90% was obtained for 250 ng ml(-1) of Tryp in spiked non-alcoholic beer samples.

Diferenciação de cervejas usando fosforimetria

“…Trabalhos já descritos anteriormente [3], relatam a fluorescência da riboflavina e a fosforescência em solução na temperatura ambiente da triptamina [4], compostos sempre presentes em cervejas.…”

“…Modificadores de superfície, principalmente surfactantes, têm sido utilizados para melhorar as interações entre o analito, o íon de átomo pesado e o substrato de celulose [3,6]. O surfactante pode melhorar o contato entre o íon de átomo pesado e o analito, amplificando o efeito externo que ocasiona a mudança de multiplicidade do estado excitado.…”

“…O tempo de purga antes da medição do sinal, a velocidade de varredura e a abertura das fendas dos monocromadores foram fixadas de acordo com estudos anteriores [3,6]. Esses resultados indicaram condições experimentais que permitiram o incremento do sinal lí-quido fosforescente e a aquisição dos espectros de fosforescência total.…”

“…Este trabalho indica a correspondência das bandas observadas na cerveja com as bandas observadas para a riboflavina. Em relação a fosforimetria aplicada a análise de cervejas Cañabate-Diaz e colaboradores [3] relatam o seu uso na determinação de triptamina em amostras de cerveja.…”

Rapid Determination of Total Tryptophan in Yoghurt by Ultra High Performance Liquid Chromatography with Fluorescence Detection

“…The TRP levels reported in this study are also of the same order of magnitude as those reported by Posati and Orr [45] on similar commercial samples. Furthermore, Cañabate-Díaz et al [46] evaluated the total TRP content in commercial yoghurts, but they reported slightly higher levels (374 mg/kg) by using a completely different method based on heavy atom-induced room temperature phosphorescence.…”