Electrical and magnetic properties of Mn–Ni–Zn ferrites processed by citrate precursor method

Mn_xNi_0.5−xZn_0.5Fe₂O₄, (x=0.05, 0.1, 0.2, 0.3, 0.4) ferrites synthesized by the citrate precursor method are investigated in the present work. Compositional variation of AC resistivity is studied and values up to 10³ times greater than those for samples prepared by the conventional ceramic method are observed. It is found that resistivity decreases with increase in Mn concentration except for x=0.3, where it shows a rise. Frequency variations of both dielectric constant and relative loss factor (rlf) are reported in the present work. It is observed that dispersion in dielectric constant is greatly influenced by the Mn concentration. Possible mechanisms contributing to these properties are discussed. Hysteresis properties are also reported.     

响应面优化超声辅助酶法提取辣椒红色素研究

以铁皮辣椒为原料,在单因素实验的基础上,选择超声功率、乙醇浓度、超声时间、酶用量进行四因素三水平的Box-Benhnken买验,利用Design-Expert 8.0软件进行响应面分析.响应面法优化结果表明,在超声功率434W、乙醇浓度75.5％、超声时间76.3 min、酶用量4 mg的条件下,辣椒红色素的提取效果最...     

基于QuEChERS-GC-MS/MS法同时测定猕猴桃中15种有机磷农药残留

建立改良的QuEChERS方法结合气相色谱-三重四极杆串联质谱（GC-MS/MS）法同时检测猕猴桃中15种有机磷农药残留的分析方法。样品前处理采用改进的QuEChERS方法,乙腈-乙酸乙酯（1∶1,V/V）作为提取溶剂,经100 mg乙二胺-N-丙基硅烷（PSA）、200 mg十八烷基硅烷键合硅胶（C18）、40 mg石墨化碳黑（GCB）、300 mg无水硫酸镁固相分散净化,用GC-MS/MS法在多反应监测（MRM）模式下分析检测,内标法定量。结果表明,15种有机磷农药在质量浓度0.05～1.00 μg/mL范围内线性关系良好,相关系数R2均＞0.998,方法检出限为0.001 2～0.326 5 μg/kg,定量限为0.004～1.088 μg/kg;其平均加标回收率为76.95%～101.2%,精密度试验结果的相对标准偏差（RSD）（n=6）为0.21%～10.05%。该方法具有净化效果好、重复性强、灵敏度高等优势,适用于猕猴桃样品中多种农药残留的同时检测。