The Application Of Open Ionization Mass Spectrometry In Drug Inspection

Mass spectrometry,with its specificity,sensitivity,high-speed and label-free properties has become a popular tool for qualitative and quantitative analysis.However,its development was obstructed by the closed ionization environment and complicate pretreatment process.In recent years,ambient ionization(AI)mass spectrometry has been widely reported and it allows the rapid analysis of samples or objects in the open environment with little or no prior preparation,which greatly promotes the application in real-time and high throughput screening.Dissolution is the key parameter to evaluate the preparation process and the correlation in vivo and in vitro of the oral solid dosage forms.Especially for bioequivalence exemption of generic drugs,it is very important to determine the dissolution in vitro.But for some medicines with low ultraviolet absorption and small dosage preparations,it is difficult to establish an effective method to determine its dissolution profile.In this thesis,we installed a paper spray ionization(PSI)source on a mass spectrometer to explore the application of PSI-MS in drug dissolution test for the first time.PSI-MS is compatible with the inorganic salts and suitable for the determination of very low dosage with no or minimal sample pretreatment.Good linearity of Enalapril maleate,Quinapril hydrochloride and Benazepril hydrochloride were achieved throughout the concentration ranges with the corresponding deuterium labelled compounds as the internal standard.Enalapril maleate tablets dissolution results from PSI-MS were consistent with those from traditional HPLC method indicating that the established new method can be used for the determination of dissolution.Analyzing time were within couple of seconds.It is currently impractical to totally quantify analytes with all isotopically labelled internal standards.Owing to the high costs of many deuterium reagents,it's essential to explore the utilization of non-isotopically labelled internal standards in PSI-MS.We studied the application of finasteride impurity?as the internal standard in PSI-MS,the structure and property of which was similar to the analytes to successfully measure the dissolution content of finasteride tablets.The results from PSI-MS are similar to those from HPLC.The non-isotopically labelled internal standards are suitable for accurate dissolution determination by PSI-MS,which expanded the application of PSI-MS in the determination of dissolution.Amyloid ?-protein(A?)is an important component of senile plaques in Alzheimer's disease(AD)and considered as a potential target for the treatment of AD.Some studies have shown that ginsenoside can delay AD presuming that its action may be by non-covalent interactions between ginsenoside and A?.Previously,there was no effective means to determine the binding of non-covalent interactions,nor can we elucidate the mechanism of ginsenoside.Cold spray ionization(CSI)provides a stable solvation-ionization at low temperature and preserves the weak non-covalent interaction in the solution,which is expected to provide a powerful means to study non-covalent drug-protein complexes.The established new method with CSI-MS provided insights into the non-covalent interaction of ginsenosides with A? for the first time.The binding group of ligands,the relative binding affinities for complexes and stoichiometries could be obtained by direct and competition experiments,which elucidated the possible mechanism of ginsenosides to alleviate AD by interfering with the aggregation of A? at the molecular level and provided strong technical support for the characterization of non-covalent interactions and the development of Alzheimer's disease drugs.