NMR Detects Contaminants In Heparin

To help regulators spot contaminated vials of the blood thinner heparin, researchers have developed a nuclear magnetic resonance method that exposes any additive in a sample of the drug (Anal. Chem., DOI: 10.1021/ac301428d). In each batch of heparin, the polysaccharide’s structure varies slightly because manufacturers extract it from pig intestines, says Timothy R. Rudd of the Ronzoni Institute, in Milan. As a result, regulators can’t monitor the drug’s purity on the basis of a single structure. Instead they rely on its anticoagulant activity. To devise a more precise test, Rudd created an NMR-based description of heparin, which would include signals unique to pig heparin and would delineate how those signals change from batch to batch. He and his colleagues defined heparin’s unique NMR signals as those whose intensities varied together from sample to sample. By comparing the chemical shifts and intensities of signals between sets of heparin spectra, the researchers established how much heparin’s signals vary naturally. In heparin samples spiked with sheep and cow heparin, which differ only slightly from pig heparin, the researchers used the definition to detect contaminant levels as low as 1%.