Ionic‐liquid‐based ultrasound/microwave‐assisted extraction of 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one and 6‐methoxy‐benzoxazolin‐2‐one from maize (Zea mays L.) seedlings

We evaluated an ionic‐liquid‐based ultrasound/microwave‐assisted extraction method for the extraction of 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one and 6‐methoxy‐benzoxazolin‐2‐one from etiolated maize seedlings. We performed single‐factor and central composite rotatable design experiments to optimize the most important parameters influencing this technique. The best results were obtained using 1.00 M 1‐octyl‐3‐methylimidazolium bromide as the extraction solvent, a 50°C extraction temperature, a 20:1 liquid/solid ratio (mL/g), a 21 min treatment time, 590 W microwave power, and 50 W fixed ultrasonic power. We performed a comparison between ionic‐liquid‐based ultrasound/microwave‐assisted extraction and conventional homogenized extraction. Extraction yields of 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one and 6‐methoxy‐benzoxazolin‐2‐one by the ionic‐liquid‐based ultrasound/microwave‐assisted extraction method were 1.392 ± 0.051 and 0.205 ± 0.008 mg/g, respectively, which were correspondingly 1.46‐ and 1.32‐fold higher than those obtained by conventional homogenized extraction. All the results show that the ionic‐liquid‐based ultrasound/microwave‐assisted extraction method is therefore an efficient and credible method for the extraction of 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one and 6‐methoxy‐benzoxazolin‐2‐one from maize seedlings.     

NixZry(x:y=1∶2或2∶1)团簇的量子化学研究

根据化学键理论和拓扑学原理,设计了非晶态团簇NixZry(x:y=1∶2 或2∶1, x+y≤9)的几十种可能的构型,并应用量子化学从头算方法对它们的几何构型进行了优化,分析比较了这些构型的能量和稳定性。结果表明对于NixZry(x:y=1∶2)低对称性的平面构型最稳定,而NixZry(x:y=2∶1)三棱柱构型最稳定。这可能是由于两者外层价电子的数量差异所致： Zr仅有4个价电子,较适宜配位数低的平面构型,而Ni（4s23d8),更适宜立体构型。     

A New 6,7-Seco-Ent-Kaurane Diterpenoid from Isodon eriocalyx Var. laxiflora

Isodon eriocalyx var. laxiflora C. Y. Wu & H. W. Li, is a perennial herb naturally growing in the southern area of Yunnan province. In our continuing studies1 on its leaves collected from Xishuanbana prefecture, a new 6,7-seco-ent-kaurane diterpenoid, named laxiflorin E (1), together with two known 6,7-seco-ent-kaurane diterpenoids2, eriocalyxin A (2) and laxiflorin C (3), was isolated. Their structures were established by spectroscopic analysis. Compound 1, obtained as colorless rhombus…     

A New Triterpene from Cephalomappa sinensis

Cephalomappa sinensis (Chun et How) Kosterm belongs to the family Euphorbiaceae. It is distributed in southwest and west of Guangxi Zhung Autonomous Region1. Its fresh leaves are used as feeding stuff for cattle, horse, and sheep and can make them strong1. Chemical constituents of this species have not been reported previously. In our research, a new triterpene was isolated from the ethanolic extract of its roots. Compound 1 was obtained as colorless needles, mp 235-237(C. The EI-mass sp…     

Three New C21 Steroidal Glycosides from the Roots of Cynanchum komarovii Al.Iljinski

Three new C21 steroidal glycosides named komaroside A, komaroside B, komaroside C were isolated from the ethanolic extract of the roots of Cynanchum komarovii Al.Iljinski(Asclepiadaceae), their structures were determined by physiochemical and spectroscopic analysis.     

固相萃取富集-高效液相色谱法测定烟草和烟草添加剂中的重金属元素

研究了用固相萃取富集,高效液相色谱法测定烟草及烟草添加剂中镍、铜、锡、铅、镉、汞的方法。样品用微波消化后,消化液中镍、铜、锡、铅、镉、汞用四 (对氨基苯基) 卟啉[T (p AP)P]柱前衍生,用C18固相萃取小柱萃取富集镍、铜、锡、铅、镉、汞的T (p AP)P络合物,富集倍数为50倍;然后用甲醇和丙酮(均含0.05mol·L-1的pH10.0四氢吡咯 乙酸缓冲)为流动相进行梯度洗脱,WatersXterraTMRP18(3.9mm×150mm)为色谱柱,用二极管矩阵检测器检测。镍、铜、锡、铅、镉、汞的检出限分别为42,38,82,60,50和25ng·L-1。RSD为2.1%～2.8%,标准回收率为95%～103%。该方法用于测定烟草及烟草添加剂中的痕量镍、铜、锡、铅、镉、汞,结果满意。     

一个计算百分含量的公式

本文提出一个计算被测元素百分含量的公式。它确切、直观地反映了被测元素的浓度在标准系列浓度范围,超过甚至大大超过高、低标浓度时试液与空白的关系。我们引入关系常数n使三种关系在公式中直观地体现出来。     

ICP-AES可变浓度法测定PtIr和PdIr系列合金中的次成分Ir及杂质元素

本工作采用不称准样和不准确稀释的可变浓度的ICP-AES法,测定了PtIr_(5·30),PdIr_(5·30)系列合金中的次成分Ir和十二个杂质元素。Pt基和Pd基对待测元素的影响,采用等效浓度差减法进行校正。方法简便、快速、准确,并能节省大量的铂和钯。     

黄磷电炉用硅石的X荧光光谱快速分析

本文选择了硫酸钡为粘合剂,使其高含量硅石能直接粉末压样,应用于黄磷电炉中间控制成份分析,结果满意。     

ICP-MS测定三七中铬、砷、汞、镉和铅的测量不确定度的评估

合理评估ICP-MS测定三七中铬、砷、汞、镉、铅的测量不确定度,对测试方法的每一步骤进行不确定度的分析评估.