Identification of starch and determination of its botanical source in ancient manuscripts by MEKC–DAD and LDA

Abstract

A simple and rapid Micellar Electrokinetic Capillary Chromatography method with UV diode-array detection (MEKC–DAD) has been developed for the identification of the two starch polysaccharides, amylopectin and amylose, in ancient manuscripts. Moreover, a linear discriminant analysis (LDA) has been used in order to determine the botanical source of the starch (wheat, maize or rice). The reason to develop this method is that starch has been used throughout history in paper manufacture as glue and sizing agent.The LDA was applied to the amylopectin/amylose ratio using the area and height data recorded.The separation was performed in an extended path-length fused-silica capillary (‘bubble capillary’) of 36cm in length and 50μm i.d.. The running buffer was composed of 20mM sodium acetate, 1.2mM I2, 7.2mM KI, and 50mM sodium dodecyl sulphate (SDS) at pH6. The potential applied was 22kV in positive polarity, the temperature was 25°C, and the detection was performed at 560nm. Injection of the samples was performed at 20mbar for 2s.An artificial ageing test was carried out in the three types of starch in order to determine the effect of the temperature, relative humidity and irradiance on this compound. The procedure was performed in an ageing chamber according to the ISO 5630-3:1996 and 11341:2004 standards.The methods were applied to samples from manuscripts preserved in the Historic Archive of the University of Granada and the Royal Chancellery Archive of Granada (Spain).