Search

Carbon nanotube(CNT)–alginate gel beads were used as a novel stationary phase for the separation and purification of natural products in an open glass column. The objective of this study is to find a new packing material which can improve the separation efficiency and resolution in preparative or semi-preparative liquid chromatography. Four types of CNTs were evaluated for their adsorption and desorption capability of various natural compounds. Langmuir and Freundlich isotherms were used to correlate the solute affinity of CNTs towards alkaloids at different temperatures, and the Langmuir isotherm fit better. Static adsorption and desorption tests indicated that multi-walled carbon nanotube(MWCNT)-1 was suitable to separate alkaloids of Dature metel L. MWCNT-1 was then bonded to alginate carrier to form gel beads, which further improved the separation. Under gradient elution, the purity of atropin and anisodamine reached 83.6% (weight of atropin/weight of dry eluent) and 90.5%, respectively, which were 7.9-fold and 11.2-fold to those in control samples. The recovery yields were 88.2% and 89.2%, respectively. Therefore, alginate-supported CNTs gel beads can serve as an excellent liquid chromatographic packing material.

Earnings are a summary of operation results of enterprises over a specific period of time. Since it plays an indispensable role in stakeholders' decision-making process, the research of its quality has become one of the key topics concerned by accounting scholars. This article employs earnings persistence as a proxy for the quality of earnings, using empirical methods for a comparative analysis of earnings volatility, volatility of cash flow from operations, accruals and the extreme degree of earnings, which are usual factors that affect earnings persistence. Furthermore, this article sorts these factors according to their explanatory power, and finds earnings volatility ranked first.