High performance liquid chromatography - Quantitative nuclear magnetic resonance - High performance liquid chromatography for purity measurement of human insulin

Development of a potential primary method for protein quantification via electrospray differential mobility analysis

Accurate protein quantification is the basis for establishing the metrological traceability of in vitro diagnostics or drug products. In this study, we established and validated a potential primary method for protein quantification based on electrospray-differential mobility analysis coupled with a condensation particle counter (ES-DMA-CPC). The analytical performance of this method was assessed using the certified reference material NIMCmAb, and the uncertainty of measurement was evaluated. The method was applied to the quantification of three other protein reference materials and one highly purified protein, including myoglobin, bovine serum albumin, IgG monoclonal antibody, and one highly purified fibrinogen, with a molecular weight range between 17 kDa and 340 kDa. In addition, when compared with isotope dilution mass spectrometry (IDMS) and UV‒VIS spectrophotometry approaches, the ES-DMA-CPC method showed good agreement with IDMS method for the quantification of these protein reference materials. Our proposed method provided an accurate quantification of proteins, especially those with large molecular weights. Moreover, our method could be a potential primary method for protein quantification and serve as a complement to IDMS method.

Development of a human insulin certified reference material with SI-traceable purity

A human insulin (hINS) certified reference material (CRM) was developed by the National Institute of Metrology (NIM). Three milligrams of purified solid hINS was packed into a brown sealed tube. The candidate material was identified by de novo sequence using mass spectrometry and Edman degradation methods. The content of insulin-related impurities, aggregation, moisture, volatile organic compounds (VOCs), anions, and ignition residues was also determined. Both mass balance (MB) and amino acid analysis-based isotope dilution mass spectrometry (AAA-IDMS) were used for the certified value assessment, which was determined to be (0.857 ± 0.024) g/g. The certified value was validated by liquid chromatography-circular dichroism spectroscopy (LC-CD) and quantitative nuclear magnetic resonance (qNMR) methods, which were in good agreement. No inhomogeneity was observed during a homogeneity examination. A stability examination showed that the CRM was stable for at least 12 months when stored at - 70 °C, and for 7 days when stored at 4, 25, or 40 °C. The CRM is expected to be used as a primary calibrator for matrix insulin CRM development and for quality control in biopharmaceutical production and clinical diagnostics.