凝胶渗透色谱-气相色谱-离子阱质谱法测定桔梗原药和当归提取物中101种农药残留

建立了凝胶渗透色谱（GPC）-气相色谱-离子阱质谱同时检测桔梗原药和当归提取物中101种农药残留的分析方法。方法采用乙腈超声辅助提取桔梗原药和当归提取物,浓缩提取液至近干后用乙酸乙酯-环己烷（1∶1, v/v）复溶,采用凝胶渗透色谱法（选取40 cm长、内径20 mm的凝胶渗透色谱柱）对样品进行净化,弃去前段含脂类、色素等杂质的流出液,收集17~30 min洗脱液并旋转蒸发浓缩至近干,甲苯1 mL定容上机。选用DB-5MS毛细管色谱柱分离待测物,通过离子阱质谱实现对101种农药残留的高效检测。方法通过优化前处理条件和离子阱二级质谱参数,有效降低了复杂中药基质对待测化合物的干扰,最大限度提高了样品中农药的定量准确性和回收率,101种农药3水平添加的平均回收率为58.3%~108.9%,每个添加水平10次独立重复测定的相对标准偏差为0.4%~16.5%,检出限（LOD）范围为0.2~40.0 μg/kg,可满足当前韩国、日本、欧洲规定的最大残留限量（maximum residue limits, MRLs）要求。方法具有操作简单快速、灵敏度高、重复性好等特点,凝胶渗透色谱技术的应用克服了固相萃取小柱净化容量不足的弊端,离子阱技术的应用可以进一步排除共流出基体杂质的干扰,提高定量和定性的准确性,检测效果优于常用的气相色谱-质谱法,是对中药中同时分析多种农药残留检测方法的有益补充。     

Development of an Organic Dye-Conjugated β-Diketonate-Europium Complex Luminescence Probe for Discrimination and Detection of Intracellular Biothiols

Small molecular biothiols, cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play important roles in organisms, and their concentration levels are indicative of some human diseases. Herein we report an organic dye-conjugated β-diketonate-Eu³⁺ complex, [Eu(NBD-keto)₃(DPBT)] (NBD-keto: 7-nitro-2,1,3-benzoxadiazole (NBD)-conjugated to 1,1,1,2,2-pentafluoro-5-phenyl-3,5-pentanedionate through a “O” ether bond; DPBT: 2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine), which acts as a unique luminescent probe for detecting and discriminating biothiols. [Eu(NBD-keto)₃(DPBT)] itself is not luminescent due to intramolecular interactions between NBD and β-diketonate-Eu³⁺ moieties. Upon reaction with biothiols, the β-diketonate-Eu³⁺ complex [Eu(keto)₃(DPBT)] is generated, which emits long-lived red emission at 610 nm. Meanwhile, three biothiol-substituted NBD derivatives that exhibit different luminescence behaviors, green emissive (short-lived) NBD-NR (R=Cys or Hcy) at 540 nm and non-luminescent NBD-SR (R=GSH), are also generated. These luminescence response behaviors allow time-gated and steady-state luminescence modes to be combined for detecting total biothiols and discriminating GSH and Cys/Hcy. Using this probe, the quantitative detection and discrimination of GSH and Cys/Hcy in lysis solutions of HeLa cells were realized, which revealed the potential of the probe for biomedical applications.     

Comparison of two sample preconcentration strategies for the sensitivity enhancement of flavonoids found in Chinese herbal medicine in micellar electrokinetic chromatography with UV detection

Two on-column preconcentration techniques named stacking with reverse migrating micelles (SRMM) and anion selective electrokinetic injection and a water plug-sweeping with reverse migrating micelles (ASIW-sweep-RMM) were used and compared for concentration and separation of flavonoids in Chinese herbs using reverse migration micellar electrokinetic chromatography (RM-MEKC). The optimal background electrolyte (BGE) used for separation and preconcentration was a solution composed of 20mM phosphoric acid (H(3)PO(4))-100mM sodium dodecyl sulfate (SDS)-20% (v/v) acetonitrile (ACN) buffer (pH 2.0), the applied voltage was -15kV. To achieve reasonable results of the two techniques, the conditions which affected preconcentration were examined. A comparison of used techniques with normal hydrodynamic injection (5s), concerning enhancement factors and limits of detection (LODs) was presented. Under the optimum stacking conditions, about 27-37- and 45-194-fold improvement in the detection sensitivity was obtained for SRMM and ASIW-sweep-RMM, respectively, compared to usual hydrodynamic sample injection (5s). The LODs (S/N=3) for SRMM and ASIW-sweep-RMM in terms of peak height, can reach down to 1.15 x 10(-2) microg/ml for hesperetin and 2.4 x 10(-3) microg/ml for nobiletin, respectively. Finally, the amounts of the six flavonoids in extract of Fructus aurantii Immaturus were successfully determined using ASIW-sweep-RMM. The six analytes were baseline separated with sample matrix under the optimum ASIW-sweep-RMM conditions and the experimental results showed that preconcentration was well achieved after the dilution of sample solutions.     

A general synthesis of substituted formylpyrroles from ketones and 4-formyloxazole

A novel two-step synthesis of substituted 2-formylpyrroles is described. Aldol adducts of ketones and 4-formyloxazole undergo a dehydration/oxazole hydrolysis/cyclization cascade on sequential treatment with MsCl/Et3N and aqueous NaOH to yield 5-substituted and 4,5-disubstituted 2-formylpyrroles. The methodology was extended to an N-benzyl thiazolium salt.     

TVD格式在燃料蒸气云爆炸场数值模拟中的应用

本文采用了有限差分方法——TVD格式(Total Variation Diminishing,A.Harten,1983)对燃料蒸气云爆炸产生的二维轴对称爆炸场进行了数值模拟。爆炸波超压和运动轨迹的数值计算值与实验结果吻合得相当好。     

用电热引燃法测定空气成分

空气成分测定的演示实验,采用以红磷做燃烧耗氧剂,用密封式电热引燃,可彻底克服传统实验在操作时的忙乱感,减少实验误差。     

Squeezing of Phonons in Photon-Phonon Interaction via Anti-Stokes Light

A model of the photon-phonon interaction via anti-Stokes light has been proposed to investigate the squeezing properties of phonon mode. The behavior of initial anti-Stokes light with complex statistics has been studied. It is shown that the squeezing of phonon mode can appear under certain conditions.     

Behaviour of Prompt Gamma-Ray Emission in ColdFission of 252Cf

The behaviour of prompt γ-ray emission in the cold fission of ²⁵²Cf was investigated experimentally using a four-parameter correlation technique. A twin gridded ionization chamber was employed to detect the fission signals and to determine the fragment emission angles, and a φ10cm×10cm NaI(T1) detector was used to record the γ-ray energies. The result shows that the angular distribution coefficient of γ-rays emitted in cold fission is twice as large as that in the normal fission.The fact that in the cold fission the number of γ-rays emitted from the light fragments is approximately three times as large as that from the heavy ones can not be explained satisfactorily so far.