Characterising Technical Cashew Nut Shell Liquid using Maldi-ToF MS

Abstract

Background: Various techniques have been applied for detecting anacardic acid, cardanol, cardol, and 2-methylcardol and their degrees of unsaturation in a complex mixture of a highly corrosive cashew nut shell liquid found in the cashew (anacardium occidentale) nut shells. However, very little has been reported on the applicability of matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry for the same. The aim of this paper is to report the application of this technique for identifying those components in technical cashew nut shell liquid obtained by a hot-roasting process. Methods: The cashew nut shell liquid analyte was diluted in acetone before adding a matrix of 2,5- dihydroxybenzoic acid, which contained acetone in a volumetric ratio of 1:2. This was followed by doping the analyte with either sodium or silver trifluoroacetate. Results: The mass spectra obtained by both sodium trifluoroacetate and silver trifluoroacetate dopants revealed existence of well-resolved peaks ascribed to cardanol and cardol in the analyte. It was further observed that the peaks corresponding to 2-methyl cardol and anacardic acid in the analyte could only be detected by using sodium trifluoroacetate dopant. The results have further revealed the possibility of the material to contain traces of other components between 0.3 and 23%. Peaks associated with those components may have been overlapped with peaks ascribed to the phenolic components. Conclusion: The results therefore suggest that this technique may be applicable for characterising the composition of technical cashew nut shell liquids when proper sample preparation is done and appropriate solvents, dopants and matrices are used. Keywords: Anacardic acid, cardanol, cardol, 2-methyl cardol, Maldi-ToF, saturation.