Improvement of chlorophyll identification in foodstuffs by MALDI ToF/ToF mass spectrometry using 1,5-diaminonaphthalene electron transfer secondary reaction matrix

• Published in: Analytical and bioanalytical chemistry Vol. 407; no. 21; pp. 6369 - 6379
• Main Authors: Calvano, Cosima Damiana, Ventura, Giovanni, Cataldi, Tommaso R. I, Palmisano, Francesco
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-08-2015; Springer; Springer Nature B.V
• Subjects: 2-Naphthylamine - analogs & derivatives; 2-Naphthylamine - chemistry; Acids; Algae; Analytical Chemistry; Biochemistry; Biotransformation; Byproducts; Cations; Characterization and Evaluation of Materials; Chemical properties; Chemical reactions; Chemistry; Chemistry and Materials Science; Chlorophyll; Chlorophyll - analysis; Chlorophylls; chloroplasts; Chromatography; color; desorption; Electron transfer; Electron transport; Electrons; Food Analysis - methods; Food Science; Food testing; foods; Fragmentation; High-Resolution Mass Spectrometry in Food and Environmental Analysis; Identification and classification; Ionization; Laboratory Medicine; Lasers; leaves; Mass spectrometry; Methods; Monitoring/Environmental Analysis; Observations; Pigments; Plant Leaves - chemistry; Plant Oils - analysis; Processed foods; Research Paper; Scientific imaging; Seeds; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; Sunflower Oil; tea; Tea - chemistry; Time-of-flight mass spectrometry; vegetable oil; Vegetable oils; Vegetables; Vegetables - chemistry; Italy; High-resolution MS; Matrices; Foodstuffs; Tandem MALDI-ToF MS; Electron transfer matrices; Chlorophylls
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-015-8728-9

Chlorophylls (Chls) are important pigments responsible for the characteristic green color of chloroplasts in algae and plants. In this study, 1,5-diaminonaphthalene (DAN) was introduced as an electron transfer secondary reaction matrix for the identification of intact chlorophylls and their derivatives, by matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS). DAN was proved to drastically outperform conventional matrices such as α-cyano-4-hydroxycinnnamic acid, dithranol, antracene, and even terthiophene, since loss of the metal ion and fragmentation of the phytol–ester linkage are negligible. Absence of significant fragmentation of radical cations of Chls a and b at m/z 892.529 and 906.513, respectively, makes MALDI MS capable of following natural degradation of intact porphyrin-based pigments whose initial steps are just represented by demetalation and dephytylation. Chl by-products, such as pyropheophytins, have been identified in dried tea leaves showing the potential of MALDI MS to follow chlorophyll biotransformation occurring in processed foodstuffs. Finally, preliminary results show the potential of MALDI MS to detect illegal vegetable oil re-greening practices.