Aim In the present study a RP-HPLC method was developed and validated toinvestigate the stability of baicalin aqueous solution. Methods The influences of temperature and pHon the stability of baicalin aqueous solution...Aim In the present study a RP-HPLC method was developed and validated toinvestigate the stability of baicalin aqueous solution. Methods The influences of temperature and pHon the stability of baicalin aqueous solution were investigated by classic homoiothermicacceleration test, and the pH for the most stable solution was determined. Results The time whenbaicalin suffered 10% loss was found to be 18.1 h, and the degradation activation energy of baicalinwas 79.1 kJ·moL^(-1) . The pH at which baicalin is most stable is 4.28. Conclusion The temperatureshould be kept at a lower level and the pH should be adjusted to near that for the most stablesolution in the production of baicalin preparations.展开更多
The stability and reactivity of nanomaterials are of crucial importance for their application, but the long-term effects of stability and reactivity of nanomaterials under practical conditions are still not well under...The stability and reactivity of nanomaterials are of crucial importance for their application, but the long-term effects of stability and reactivity of nanomaterials under practical conditions are still not well understood. In this study, we first established a comprehensive strategy to investigate the stability of a highly reactive nanomaterial from the viewpoint of reaction kinetics with ultrathin tellurium nanowires （TeNWs） as a model material in aqueous solution through an accelerated oxidation process. This allowed us to propose a new approach for the design and synthesis of other unique one-dimensional nanostructures by a chemical transformation process using the intermediate nanostructures ＂captured＂ during the dynamic oxidation process under different conditions. In essence, the oxidation of ultrathin TeNWs is a gas-solid reaction which involves liquid, gas and solid phases. It has been demonstrated that the oxidation process of ultrathin TeNWs in aqueous solution can be divided into three stages, namely oxygen limiting, ultrathin TeNWs limiting and mass transfer resistance limiting stages. The apparent oxidation kinetics for ultrathin TeNWs is approximately in accord with a first order reaction kinetics model and has an apparent activation energy as low as TeNWs are thermodynamically unstable 13.53 kJ.mol^-1, indicating that ultrathin However, the unstable nature of ultrathin TeNWs is actually an advantage since it can act as an excellent platform to help us synthesize and design one-dimensional functional nanomaterials--with special structures and distinctive properties--which are difficult to obtain by a direct synthesis method.展开更多
文摘Aim In the present study a RP-HPLC method was developed and validated toinvestigate the stability of baicalin aqueous solution. Methods The influences of temperature and pHon the stability of baicalin aqueous solution were investigated by classic homoiothermicacceleration test, and the pH for the most stable solution was determined. Results The time whenbaicalin suffered 10% loss was found to be 18.1 h, and the degradation activation energy of baicalinwas 79.1 kJ·moL^(-1) . The pH at which baicalin is most stable is 4.28. Conclusion The temperatureshould be kept at a lower level and the pH should be adjusted to near that for the most stablesolution in the production of baicalin preparations.
文摘The stability and reactivity of nanomaterials are of crucial importance for their application, but the long-term effects of stability and reactivity of nanomaterials under practical conditions are still not well understood. In this study, we first established a comprehensive strategy to investigate the stability of a highly reactive nanomaterial from the viewpoint of reaction kinetics with ultrathin tellurium nanowires （TeNWs） as a model material in aqueous solution through an accelerated oxidation process. This allowed us to propose a new approach for the design and synthesis of other unique one-dimensional nanostructures by a chemical transformation process using the intermediate nanostructures ＂captured＂ during the dynamic oxidation process under different conditions. In essence, the oxidation of ultrathin TeNWs is a gas-solid reaction which involves liquid, gas and solid phases. It has been demonstrated that the oxidation process of ultrathin TeNWs in aqueous solution can be divided into three stages, namely oxygen limiting, ultrathin TeNWs limiting and mass transfer resistance limiting stages. The apparent oxidation kinetics for ultrathin TeNWs is approximately in accord with a first order reaction kinetics model and has an apparent activation energy as low as TeNWs are thermodynamically unstable 13.53 kJ.mol^-1, indicating that ultrathin However, the unstable nature of ultrathin TeNWs is actually an advantage since it can act as an excellent platform to help us synthesize and design one-dimensional functional nanomaterials--with special structures and distinctive properties--which are difficult to obtain by a direct synthesis method.
