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

M. L. SALUM; T. SCHMIDT DE LEON; R. ERRA-BALSELLS; R.; ERRA BALSELLS

Analytical Methods

Royal Chemical Society

Lugar: London; Año: 2015 vol. 7 p. 8478 - 8483

1759-9660

Since the introduction of 3,5-dimethoxy-4-hydroxycinnamic acid (SA) and a-cyano-4-hydroxycinnamic acidas matrices, the 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. Thecommercially available cinnamics currently used as matrices are E-cinnamics; they do not perform well ingeneral for carbohydrate analysis. Recently, Z-cinnamic acid properties for matrices were studied andcompared with those of the corresponding E-isomer. For the analysis of neutral/sulfated carbohydratesthe outstanding performance for Z-SA was demonstrated. As the synthesis of pure Z-cinnamic acidsrequires several steps and the manipulation of some not friendly chemicals (i.e., bad smelling organicamines, toxic compounds, organic solvents, etc.), here we describe a convenient new one-pot protocol toprepare in situ, in a methanolic solution of commercial E-acid (i.e., E-SA), a Z- + E- mixture byphotoisomerization (UVB irradiation); then, the only step required is the addition of water to the irradiatedsolution to become ready as a matrix stock solution for MALDI experiments. This ?photo-made at home?matrix performs carbohydrate analysis with similar results to the corresponding Z-acid. The results hereshow that this novel protocol is a tool of choice for the direct, rapid and sensitive detection of neutral andsulfated carbohydrates without any tedious Z-cinnamic acid preparation and isolation