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A simple, sensitive, and accurate stability-indicating analytical method has been developed and validated using ultra high performance liquid chromatography. The developed method is used to evaluate the related substances of eplerenone (EP). The degradation behavior of EP under stress conditions was determined, and the major degradants were identified by ultra high performance liquid chromatography with tandem mass spectrometry. The chromatographic conditions were optimized using an impurity-spiked solution, and the samples, generated from forced degradation studies. The resolution of EP, its potential impurities, and its degradation products was performed on a Waters UPLC BEH C18 column (50 × 2.1 mm, 1.7 μm) by linear gradient elution using a mobile phase consisting of 10 mmol/L ammonium acetate adjusted to pH 4.5, methanol and acetonitrile. A photo-diode array detector set at 245 nm was used for detection. The flow rate was set at 0.3 mL/min. The procedure had good specificity, linearity (0.02-3.14 μg/mL), recovery (96.1-103.9%), limit of detection (0.01-0.02 μg/mL), limit of quantitation (0.03-0.05 μg/mL), and robustness. The correction factors of the process-related substances were calculated. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the low-boiling fraction (LBF) of bio-oil was used as feed stock. LBF is a very complex mixture, and the three groups in LBF: acids, aldehydes and phenols, are primarily responsible for deterioration in the quality. The upgrading reactions were carried out over Pt/Al2(SiO3)3, Pt/C or Pt/MgO in supercritical methanol. It is demonstrated that supercritical condition can greatly facilitate the esterification process, and after 6h reaction, all the acids can be converted into esters even without adding any catalyst. The total amount of the three groups left in products was much less exhibited on Pt supported on active carbon and MgO in the presence of hydrogen. By investigating the model reactions, the relations between the representative compounds and major products were identified, and the conversion scheme of the upgrading reactions is proposed. [Copyright &y& Elsevier]