Determination of the number-average molecular weight of polysaccharides by end-group reduction with borohydride-t

The reduction with sodium borohydride-t of a series of maltose oligosaccharides yields products whose residual radioactivity (after deduction of a blank) has a linear dependence on degree of polymerisation. The procedure has been extended to measure the average degree of polymerisation (or alternatively M_n) of hydrolysed amyloses. For this purpose, it is necessary to use a washing procedure to remove a radioactive impurity in the sodium borohydride. The method should be applicable to measurement of number-average molecular weights of any polysaccharide which has a reducing end-group.