LC,MS^n and LC-MS/MS studies for the characterization of degradation products of amlodipine

In the present study,comprehensive stress testing of amlodipine（AM） was carried out according to International Conference on Harmonization（ICH） Q1A（R2） guideline.AM was subjected to acidic,neutral and alkaline hydrolysis,oxidation,photolysis and thermal stress conditions.The drug showed instability in acidic and alkaline conditions,while it remained stable to neutral,oxidative,light and thermal stress.A total of nine degradation products（DPs） were formed from AM.which could be separated by the developed gradient LC method on a C18 column.The products formed under various stress conditions were investigated by LC-MS/MS analysis.The previously developed LC method was suitably modified for LC-MS/MS studies by replacing phosphate buffer with ammonium acetate buffer of the same concentration（pH 5.0）.A complete fragmentation pathway of the drug was first established to characterize all the degradation products using LC-MS/MS and multi-stage mass（MS^n） fragmentation studies.The obtained mass values were used to study elemental compositions,and the total information helped with the identification of DPs.along with its degradation pathway.

Force degradation behavior of glucocorticoid deflazacort by UPLC：isolation,identification and characterization of degradant by FTIR,NMR and mass analysis

In this investigation,sensitive and reproducible methods are described for quantitative determination of deflazacort in the presence of its degradation product.The method was based on high performance liquid chromatography of the drug from its degradation product on reverse phase using Acquity UPLC BEH C18columns（1.7 urn,2.1 mm ×150 mm） using acetonitrile and water（40：60 V/V） at a flow rate of 0.2 mL/minute in UPLC.UV detection was performed at 240.1 nm.Deflazacort was subjected to oxidative,acid,base,hydrolytic,thermal and photolytic degradation.The drug was found to be stable in water and thermal stress,as well as under neutral stress conditions.However,forced-degradation study performed on deflazacort showed that the drug degraded under alkaline,acid and photolytic stress.The degradation products were well resolved from the main peak,which proved the stability-indicating power of the method.The developed method was validated as per ICH guidelines with respect to accuracy,linearity,limit of detection,limit of quantification,accuracy,precision and robustness,selectivity and specificity.Apart from the aforementioned,the results of the present study also emphasize the importance of isolation characterization and identification of degradant.Hence,an attempt was made to identify the degradants in deflazacort.One of the degradation products of deflazacort was isolated and identified by the FTIR,NMR and LC-MS study.

Degradation Behavior of Zn-Cu Stents with Different Coatings in Sodium Chloride Solution

The Zn0.6Cu wires are fabricated into stents for the potential biodegradable application of nasal wound healing.The degradation behavior of Zn0.6Cu stents in 0.9 wt%NaCl at 36.5℃ is evaluated.It shows that the untreated Zn0.6Cu stent experiences severe crevice corrosion with acceleration and autocatalytic effects within the micro-cracks and ruptures at 4.67±1.15 d,with the average corrosion rate of 0.28 mm y^(-1).Fortunately,the anodic polarization(AP)+hydrothermal(H)conversion coating,consisting of ZnCO_(3),Zn(OH)_(2) and ZnO,could inhibit the crevice corrosion significantly by reducing the cathode/anode ratio,extending the rupture time up to 16.50±2.95 d,with the average corrosion rate of 0.14 mm y^(-1).This research indicates that the biodegradable Zn-based stent has some potential applications in nasal wound recovery area.