Easy Protocol for Making at Home E-Sinapinic Acid Good Matrix for Neutral and Sulfated Carbohydrate MALDI-MS Analysis

MARÍA LAURA SALUM; TOBIAS SCHMIDT DE LEÓN; ROSA ERRA-BALSELLS

Analytical methods

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2015 p. 8478 - 8483

1759-9660

Since the introduction of 3,5-dimethoxy-4-hydroxycinnamic acid (SA) and α-cyano-4-hydroxycinnamic acid as matrices successful application of matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) started. Cinnamics can exist as two different geometric isomers, the E- and Z-forms. Commercial available cinnamics currently used as matrices are E-cinnamics; they do not perform well in general for carbohydrate analysis. Recently, Z-cinnamic acids properties as matrices were studied and compared with those of the corresponding E-isomer. For the analysis of neutral/sulfated carbohydrates the outstanding performance for Z-SA was demonstrated. As synthesis of the pure Z-cinnamic acids requires several steps and manipulation of some no friendly chemicals (i.e., bad smelling organic amines, toxic compounds, organic solvents, etc.), here we describe a convenient new one-pot protocol to prepare in situ, in the methanolic solution of commercial E-acid (i.e., E-SA), the Z- + E- mixture by photoisomerization (UVB irradiation); then, only is required the addition of water to the irradiated solution to be ready as matrix stock solution for MALDI experiments. This ?photo-made at home? matrix performs for carbohydrate analysis similarly as the corresponding Z-acid does. The results here described show that this novel protocol is a tool of choice for direct, rapid and sensitive detection of neutral and sulfated carbohydrates without any tedious Z-cinnamic acid preparation and isolation.