Determination of carbon bound non-exchangeable (CBNE) hydrogen isotope ratios in starch by Microwave Assisted Hydrolysis (MAH) and GC-CrAg/HTC-IRMS

Polysaccharides, e.g. starch, are the most abundant biopolymers on earth. They are long chain monosaccharides linked by glycosidic bonds and are playing different important roles in plants such as energy storage (e.g. starch and glycogen) structure and growth (e.g. cellulose and pectin).The determination of carbon bound non-exchangeable (CBNE) hydrogen isotope ratios in polysaccharides are of great interest in a broad range of research areas, as they contain intrinsic information about the metabolic pathway and geographical origin of the plant, derived from water incorporated during photosynthesis. Measuring non-exchangeable hydrogen isotope ratios in starch is challenging using methods such as the dual water-equilibration technique, which are labour intensive and open to a certain degree of contention of over equilibration times, temperatures, proportions of exchangeable hydrogen and fractionation factors. We report on a new approach, to determine non-exchangeable hydrogen isotopes in starch, after hydrolysis of the biopolymer into monosaccharides followed by conversion into volatile trifluoroacetamide (TFA) derivatives and analysis by GC-CrAg/HTC-IRMS.

This new methodology (Figure.01) is rapid and simple compared to current available methods and should allow CBNE hydrogen isotope analysis to be more easily and widely used.