The invention relates to a method for assaying the teichoic acids present,
most commonly in residual form, in a preparation of Gram+ bacterial
antigens. This method requires, first of all, a controlled hydrolysis
with hydrofluoric acid at a temperature of less than or equal to
40.degree. C., in order to release the oligosaccharides specific for
teichoic acids. The assaying of the specific oligosaccharides can then be
carried out by various techniques, in particular by high performance
chromatography coupled with pulsed amperometric detection (HPAEC-PAD).
The method according to the invention can in particular be used to assay
the residual amounts of teichoic acids present in preparations containing
capsular polysaccharides of Streptococcus pneumoniae, which may be useful
as vaccines.