Determination of the binding situation of pyridine in xylan sulfates by means of detailed NMR studies

Abstract Xylan sulfate is an important drug to treat interstitial cystitis. Production of the drug by sulfation of the polysaccharide with a sulfating agent like chlorosulfuric acid and pyridine–SO 3 complex in pyridine may lead to products containing pyridine‐based impurities. Xylan sulfate containing nitrogen is investigated by different NMR measurements in order to clarify the binding situation of pyridine. The detailed NMR studies allow the conclusion that the pyridine‐based impurities are covalently bonded to the reducing end group. Furthermore, the NMR spectroscopic investigation indicates that the side reactions occur at shorter polymer chains only

X-Nuclei NMR Self-Diffusion Studies in Mesoporous Silica Foam and Microporous MOF CuBTC

A standard X-observe NMR probe was equipped with a z-gradient coil to enable high-sensitivity pulsed field gradient NMR diffusion studies of Li+ and Cs+ cations of aqueous salt solutions in a high-porosity mesocellular silica foam (MCF) and of CO2 adsorbed in metal-organic frameworks (MOF). The coil design and the necessary probe modifications, which yield pulsed field gradients of up to ±16.2Tm−1, are introduced. The system was calibrated at 2H resonance frequency and successfully applied for diffusion studies at 7Li, 23Na, 13C and 133Cs frequencies. Significant reductions of the diffusivities of the cations in LiClac and CsClac solution introduced into MCFs are observed. By comparison of the diffusion behavior with the bulk solutions, a tortuosity of the silica foam of 4.5 ± 0.6 was derived. Single component self-diffusion of CO2 and CH4 (measured by 1H NMR) as well as self-diffusion of the individual components in CO2/CH4 mixtures was studied in the MOF CuBTC. The experimental results confirm high mobilities of the adsorbed gases and trends for diffusion separation factors predicted by MD simulations