Discrimination of Human Insulin and its Analogs by Flow Injection Analysis with Mass Spectrometry

Although insulin therapy is recognized as an effective treatment for diabetes, it can lead to serious side effects and medical accidents. Since living organisms contain many foreign components, the separation of these components by liquid chromatography (LC) is essential for the identification of insulin preparations. However, it is difficult to conclude that separation by LC is indispensable because multiple components are unlikely to be mixed in a sample obtained from a vial or syringe needle. Therefore, the introduction of flow injection analysis (FIA), in which samples are analyzed with the column removed, can potentially eliminate the sample separation process and reduce analysis time. In addition, tandem mass spectrometry (MS/MS), which allows detailed analysis, requires expensive equipment, and some facilities only allow analysis by single mass spectrometry (MS). The discriminatory ability of each analysis method should also be clarified. Here, we examined the analysis time and discriminatory ability using a combination of FIA, MS, and MS/MS. The results showed that FIA reduced the analysis time, FIA-MS could not discriminate when the molecular weights of the samples were the same or similar, and FIA-MS/MS could discriminate between different amino acid sequences. FIA-MS has limitations in discrimination, whereas FIA-MS/MS is considered an analytical method that can shorten the analysis time and discriminate formulations.