Nanocrystalline cellulose (NCC) was prepared from microcrystalline cellulose (MCC) by acid hydrolysis.It was observed that the diameter of NCC particles mainly distributed over 30～50 nm by transmission electron micro...Nanocrystalline cellulose (NCC) was prepared from microcrystalline cellulose (MCC) by acid hydrolysis.It was observed that the diameter of NCC particles mainly distributed over 30～50 nm by transmission electron microscope (TEM).The crystal form and degree of crystallinity were detected by X-Ray diffraction.The results showed that NCC and MCC have the same crystal form of cellulose I,and that the reactions mainly occurred in the amorphous region of MCC during the acid hydrolysis process.The thermal behavior of NCC in different pH conditions was characterized by differential scanning calorimetry (DSC).The consequences indicate that the thermal stability of NCC distinctly decreased by contrast with the thermal stability of MCC,and that the thermal stability of NCCs in alkali conditions was higher than that of NCCs in acid conditions.The specific surface area distinctly increased with sharp decreasing of the particle size of NCC.This induced the end carbons and active groups of surface of NCC to increase sharply,therefore caused the thermal stability of NCC to distinctly abate.That NCC has very strong adsorption affinity is the cause of the obvious difference of thermal behavior of NCC in different pH.In acid conditions the surface of NCC adsorbed a great lot of H^+,which induced the cellulose chains of surface of NCC to decompose at low temperature catalyzed by H^+.When adding sodium hydroxide solution,on one hand the H^+ of surface of NCC was neutralized; on the other hand,the cellulose chains of low molecular weight were dissolved in sodium hydroxide solution and the defects of surface of NCC rearranged and stable structure formed.These factors improved the thermal stability of NCC in alkali conditions.展开更多
建立了氧瓶燃烧-离子色谱电导检测法测定格列喹酮主环物中水合氯醛含量的方法。采用氧瓶燃烧法,使格列喹酮主环物中水合氯醛的有机氯转化为无机氯,经氢氧化钠水溶液吸收后转化为氯离子。通过对流动相、流速、柱温的考察,确定优化后的离...建立了氧瓶燃烧-离子色谱电导检测法测定格列喹酮主环物中水合氯醛含量的方法。采用氧瓶燃烧法,使格列喹酮主环物中水合氯醛的有机氯转化为无机氯,经氢氧化钠水溶液吸收后转化为氯离子。通过对流动相、流速、柱温的考察,确定优化后的离子色谱方法为：以TSKgec Super IC-Anion HS阴离子色谱柱为分离柱;以7.5 mmol/L Na HCO3-1.1 mmol/L Na2CO3为流动相;柱温40℃;流速1.0 m L/min;检测器为电导检测器。方法学验证结果表明：该方法的专属性良好,各杂质离子峰均不干扰Cl-色谱峰的检测;精密度良好（RSD≤2.0%）;Cl-浓度在0.025~0.080 mg/L范围内线性关系良好（r=0.999 9）;检出限为0.01μg/L,定量下限为0.05μg/L;加标回收率为92.9%~103.4%,相对标准偏差（RSD）为6.4%。该方法简便、有效,能够准确检测格列喹酮主环物中水合氯醛的含量。展开更多
文摘Nanocrystalline cellulose (NCC) was prepared from microcrystalline cellulose (MCC) by acid hydrolysis.It was observed that the diameter of NCC particles mainly distributed over 30～50 nm by transmission electron microscope (TEM).The crystal form and degree of crystallinity were detected by X-Ray diffraction.The results showed that NCC and MCC have the same crystal form of cellulose I,and that the reactions mainly occurred in the amorphous region of MCC during the acid hydrolysis process.The thermal behavior of NCC in different pH conditions was characterized by differential scanning calorimetry (DSC).The consequences indicate that the thermal stability of NCC distinctly decreased by contrast with the thermal stability of MCC,and that the thermal stability of NCCs in alkali conditions was higher than that of NCCs in acid conditions.The specific surface area distinctly increased with sharp decreasing of the particle size of NCC.This induced the end carbons and active groups of surface of NCC to increase sharply,therefore caused the thermal stability of NCC to distinctly abate.That NCC has very strong adsorption affinity is the cause of the obvious difference of thermal behavior of NCC in different pH.In acid conditions the surface of NCC adsorbed a great lot of H^+,which induced the cellulose chains of surface of NCC to decompose at low temperature catalyzed by H^+.When adding sodium hydroxide solution,on one hand the H^+ of surface of NCC was neutralized; on the other hand,the cellulose chains of low molecular weight were dissolved in sodium hydroxide solution and the defects of surface of NCC rearranged and stable structure formed.These factors improved the thermal stability of NCC in alkali conditions.
文摘建立了氧瓶燃烧-离子色谱电导检测法测定格列喹酮主环物中水合氯醛含量的方法。采用氧瓶燃烧法,使格列喹酮主环物中水合氯醛的有机氯转化为无机氯,经氢氧化钠水溶液吸收后转化为氯离子。通过对流动相、流速、柱温的考察,确定优化后的离子色谱方法为：以TSKgec Super IC-Anion HS阴离子色谱柱为分离柱;以7.5 mmol/L Na HCO3-1.1 mmol/L Na2CO3为流动相;柱温40℃;流速1.0 m L/min;检测器为电导检测器。方法学验证结果表明：该方法的专属性良好,各杂质离子峰均不干扰Cl-色谱峰的检测;精密度良好（RSD≤2.0%）;Cl-浓度在0.025~0.080 mg/L范围内线性关系良好（r=0.999 9）;检出限为0.01μg/L,定量下限为0.05μg/L;加标回收率为92.9%~103.4%,相对标准偏差（RSD）为6.4%。该方法简便、有效,能够准确检测格列喹酮主环物中水合氯醛的含量。
