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61.
高效液相色谱内标法分离和测定植物中的单糖 总被引:5,自引:0,他引:5
建立了一种以 β 吲哚乙酸为内标物 ,用高效液相色谱内标法直接分离和测定植物中游离糖的新方法。木糖、果糖、葡萄糖、蔗糖、麦芽糖、乳糖和棉子糖的分离在 18min内完成 ;检出限分别达到 1 8μg ,2 3μg ,2 7μg ,1 8μg ,3 5 μg ,4 1μg和 4 3μg ,线性范围为 5 μg/L~ 75 0 μg/L。研究了流动相中乙腈的浓度、pH值对分离 7种糖和 β 吲哚乙酸的影响。方法用于枣和苹果样品的测定并进行回收率试验 ,结果为木糖、果糖、葡萄糖、蔗糖的 5次测定的回收率分别为 97 4%~ 10 2 1% ,97 3%~ 10 1 8% ,98 7%~ 10 2 2 % ,97 7%~ 10 2 5 %,。 相似文献
62.
为了揭示微空心阴极放电的放电机理,利用流体模型研究了矩形微空心阴极放电的时间和空间分布特性。在氩气环境下计算得到了压强为1.3×10~4Pa时电流、电势、电场、电子和离子密度等随时间的发展变化。结果表明,整个放电过程分为四个阶段,即预放电阶段、电场由轴向向径向转换阶段、电流缓慢增长向空心阴极效应过渡阶段和稳态放电阶段。稳态放电时出现明显的空心阴极效应,阴极位降区存在很高的径向电场和较高的电子平均能量,而负辉区径向电场很弱,电子平均能量较低,电子和离子密度峰值出现在负辉区,二者数值基本相等,而在阴极位降区离子密度远高于电子密度。 相似文献
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66.
J. -J. Ma 《Journal of Structural Chemistry》2013,54(6):1145-1150
Two new solvated benzohydrazone derivatives N′-(4-hydroxy-3-nitrobenzylidene)-3-methylbenzohydrazide-methanol-water (2/1/1) 2(C15H13N3O4)·CH3OH·H2O (1) and N′-(4-dimethylamino-benzylidene)-3-methylbenzohydrazide methanol monosolvate C17H19N3O·CH3OH (2) are prepared and characterized by elemental analysis, 1H and 13C NMR, and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic space group P21/c with unit cell dimensions a = 17.084(2) Å, b = 12.706(1) Å, c = 15.412(1) Å, β = 113.207(1)°, V = 3074.1(4) Å3, Z = 4, R 1 = 0.0567, and wR 2 = 0.1209. Compound 2 crystallizes in the monoclinic space group P21/n with unit cell dimensions a = 15.058(1) Å, b = 6.658(1) Å, c = 17.211(2) Å, β = 94.189(2)°, V = 1720.8(3) Å3, Z = 4, R 1 = 0.0611, and wR 2 = 0.1594. X-ray diffraction indicates that the asymmetric unit of 1 contains two independent benzohydrazone molecules, one methanol and one water molecules. The asymmetric unit of 2 contains one benzohydrazone molecule and one methanol molecule. Benzohydrazone molecules of the compounds display trans configurations with respect to the C=N double bonds. The crystal structures of the compounds are stabilized by hydrogen bonds and weak π...π interactions. 相似文献
67.
运用量子化学微扰理论MP2和密度泛函B3LYP方法, 采用6-311++G(d,p)基组, 对H2O, H2S与双卤分子XY (XY=F2, Cl2, Br2, ClF, BrF, BrCl)形成的卤键复合物进行构型全优化, 并计算得到了这些体系的分子间相互作用能. 利用电子密度拓扑分析方法对卤键复合物的拓扑性质进行了分析研究, 探讨了该类分子间卤键的作用本质. 结果表明, 形成卤键后, 作为电子受体的双卤分子X—Y键长增长, 振动频率减小. 复合物体系中的卤键介于共价键与离子键之间, 偏于静电作用成分为主. 相似文献
68.
Determination of triazine herbicide residues in water samples by on-line sweeping concentration in micellar electrokinetic chromatography 总被引:1,自引:0,他引:1
Shuai Hua Zhang Yuan Yuan Yang Dan Dan Han Chun Wang Xin Zhou Xiao Huan Zang Zhi Wang 《中国化学快报》2008,19(12):1487-1490
A new method for the determination of atrazine, simazine and prometryn in water samples by on-line sweeping concentration technique in micellar electrokinetic chromatography (MEKC) was developed. Various parameters affecting sample enrichment and separation efficiency were systematically studied. Compared with the conventional MEKC method, up to 60-200-fold improvement in concentration sensitivity was achieved in terms of peak height by using this sweeping injection technique. The compound strychnine was used as the internal standard for the improvement of the experimental reproducibility. The limits of detection (S/ N = 3:1) for atrazine, simazine and prometryn were 9, 10 and 0.5 ng mL-1, respectively. This method has been successfully applied to the analysis of atrazine, simazine and prometryn in lake, steam and ground water. 相似文献
69.
A method for the determination of metolcarb and diethofencarb in apples and apple juice is developed using solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC). The experimental conditions of SPME, such as the kind of extraction fiber, extraction time, stirring rate, pH of the extracting solution, and desorption conditions are optimized. The SPME is performed on a 60 microm polydimethylsiloxane/divinylbenzene fiber for 40 min at room temperature with the solution being stirred at 1100 rpm. The extracted pesticides on the SPME fiber are desorbed in the mobile phase into SPME-HPLC interface for HPLC analysis. Separations are carried out on a Baseline C18 column (4.6 i.d. x 250 mm, 5.0 microm) with acetonitrile-water (55/45, v/v) as the mobile phase at a flow rate of 1.0 mL/min, and photodiode-array detection at 210 nm. For apple samples, the method is linear for both metolcarb and diethofencarb in the range of 0.05-1.0 mg/kg (r > 0.99), with a detection limit (S/N = 3 ) of 15 and 5 microg/kg, respectively. For apple juice, the method is linear for both metholcarb and diethofencarb over the range of 0.05-1.0 mg/L (r > 0.99) with the detection limit (S/N = 3 ) of 15 and 3 microg/L, respectively. Excellent recovery and reproducibility values are achieved. The proposed method is shown to be simple, sensitive, and organic solvent-free, and is suitable for the determination of the two pesticides in apples and apple juice. 相似文献
70.
A new method for the enrichment of Strychnos alkaloids in biological samples via liquid-phase microextraction (LPME) based on porous polypropylene hollow fibers combined with on-line sweeping in micellar electrokinetic chromatography (MEKC) was developed. Strychnos alkaloids were first extracted from urine sample which was adjusted to alkaline conditions (0.5 mol l(-1) NaOH). The unionized analytes were subsequently extracted into 1-octanol impregnated in the pores of hollow fibers, and then into an acidic acceptor solution (100 mmol l(-1) H3PO4) inside the hollow fiber. The extract was analyzed directly by on-line sweeping in MEKC. In the method, the compound berberine was used as the internal standard (I.S.) for the improvement of the experimental reproducibility. The calibration curve was linear over a range of 20-200 ng ml(-1) for both strychnine and brucine in human urine sample, with a correlation coefficient of 0.996 and 0.997, respectively. The detection limits (S/N=3:1) for strychnine and brucine were 1 and 2 ng ml(-1), respectively. The LPME-sweeping method has been successfully applied to the analysis of strychnine and brucine in real urine sample, indicating that LPME-sweeping-MEKC is a promising combination for analysis of basic drugs present at low levels in some biological matrices. 相似文献