A method of testing for discerning substitution of carbohydrate ester includes the step of providing a predetermined amount of a solution. Further, the method also includes adding ammonium hydroxide and sodium borohydride to the solution. The method also includes the step of transferring the solution to an ammonium ion exchange cartridge and collecting the eluate from the cartridge. Also included in the method is the step of analyzing the sample in a mass spectrometer to produce a mass spectrum. Further, the method includes calculating the amu of phosphate and sulfate substitution of the ion and comparing it to the actual amu of the found ion.