Effect of Ca2+ on the 1H NMR chemical shift of the methyl signal of oversulphated chondroitin sulphate, a contaminant in heparin.

Abstract The chemical shift of the methyl signal of oversulphated chondroitin sulphate (OSCS) is dependent on the type and concentration of the counterion. When OSCS is present as a contaminant in heparin sodium, the reported methyl 1 H chemical shift is 2.15 ± 0.02 ppm. In this report, a value of 2.18 ± 0.01 ppm is reported for the OSCS in the presence of Ca 2+ . The chemical shift of the methyl signal of pure OSCS varies linearly from 2.13 ppm to 2.18 ppm with increasing amounts of Ca 2+ , until reaching the saturation point of four Ca 2+ ions per OSCS disaccharide unit, which contains four sulphate groups (a 1:1 ratio between sulphate groups and Ca 2+ ). This Ca 2+ effect can be used for OSCS identification as well as to facilitate quantification.