pH-Sensitive Polymer Matrix with Immobilized Indicator Ion Pairs

A new sensor material for monitoring pH in aqueous solutions is described. It is based on lipophilic ion pairs consisting of an anionic pH indicator Bromocresol Green and a quaternary ammonium cation cetyltri-methylammonium. The ion pairs are homogeneously distributed inside the plasticized PVC membrane. The change of pH in an aqueous solution causes the change of optical property of the indicator immobilized on the plasticized PVC membrane. The plasticized PVC membrane is sensitive in a pH range from 4.0 to 6.0.

Determination of N-Methylcarbamate Pesticides in Vegetables by Solid-phase Extraction and Pressurized Capillary Electrochromatography

Capillary electrochromatography （CEC） is a hybrid technique that couples the good selectivity of high-performance liquid chromatography （HPLC） and the high separation efficiency of capillary electrophoresis （CE）. Both charged and uncharged compounds can be separated effectively using CEC. In some cases, however, the bubbles that generated in the capillary column in pure CEC performed on commercial CE instruments will cause unstable current and even disrupt the separation when the concentration of buffer is very high. By applying pressure on the electrochromatographic separation via a micro-HPLC pump, pressurized capillary electrochromatography （ pCEC ） combines two driving factors of the electroosmotic flow （EOF） and the pressure flow, thereby increasing the speed and the selectivity of separation and suppressing the bubble formation. Moreover,

高效液相色谱质谱联用技术同时测定青风藤生物碱的方法

目的:建立高效液相色谱质谱联用(HPLC-MS)测定青风藤中生物碱的方法。方法:以70%乙醇进行索氏提取,HPLC-MS分析方法定性,HPLC分析方法定量。色谱条件为反相色谱柱Agilent ZORBAX SB-C18(5μm,3.0mm×250mm),柱温:30℃,进样量:10μL,流动相甲醇(A)-5mmol/L醋酸铵缓冲液(B)=55∶45(V∶V),流速:0.5mL/min,进行线性梯度洗脱。结果:在最佳的分离条件下,5种生物碱在25min内得到很好的分离效果,且适用于青风藤中青藤碱和木兰花碱的定量分析。经测定,所购青风藤药材中青藤碱和木兰花碱的含量分别为6.11和3.22mg/g。结论:本研究建立的HPLC-MS方法具有回收率高、重现性好等优点,适用于青风藤中生物碱含量的测定。