超临界CO2在泥岩生物标志物分析中的应用与索氏抽提技术的实验对比

应用超临界萃取/气相色谱-质谱技术测定泥岩中的正构烷烃、藿烷,其有机地化参数与经典索氏抽提基本相符.该方法样品用量少,且高效、快速、无污染和危险,适用于有机地球化学研究中稀少地质样品生物标志化合物及一些分子标志物的分析检测工作.     

土壤样品挥发性有机物定量分析时基体的选择及处理研究

采用传统的索氏抽提、超声萃取、振荡器提取、快速溶剂萃取(ASE)以及微波萃取等方法对不同的基体土进行了对比处理及P&T-GC-MS(吹扫捕集-气相色谱质谱联用仪)检测分析. 实验数据表明: 用索氏抽提可以获得洁净基体土. 比较而言, 石英砂处理效果更好. 3种替代物在石英砂中的回收峰面积较高, 可得到较低的方法检出限.     

催化加氢热解/气相色谱-质谱研究沉积物中生物标志物

针对地质体中高演化沉积有机质,应用催化加氢热解/气相色谱-质谱方法测定了干酪根中以共价键结合的生物标志物。结果表明,实验样品的催化加氢热解产物收率明显高于二氯甲烷（DCM）索氏抽提,产物色谱图中饱和烃的峰形、保留时间和质谱特征与索氏抽提峰形基本一致;对比两种方法产物中饱和烃主要指标甾烷m/z 217和藿烷m/z 191表明,经过加氢还原,干酪根分子网络中共价键结合着两种生物标志物分子骨架得到印证,为催化加氢热解提取沉积物中生物标志物的方法可靠性提供了依据。催化加氢热解/气相色谱-质谱技术是一种对研究高演化沉积有机质中生物标志化合物有独特作用的有效分析手段。     

超声-微波协同萃取装置用于土壤中多环芳烃的分析

本研究将开放式微波和直接超声波振荡两种不同的能量方式相结合,研制出超声-微波协同萃取装置。通过萃取土壤中微量多环芳烃(PAHs),对方法和仪器的可行性进行了初步评价。结果表明,在60 mL二氯甲烷-正已烷(1∶1,V/V)的混合萃取剂,100 W微波辐射功率(超声振动功率固定为50 W),萃取9~10m in,土壤中多环芳烃回收率达86.6%,相对标准偏差约4.0%。与索氏抽提、高压密闭和开放式微波等萃取方法相比,本方法具有样品容量大,萃取时间短,萃取效率受样品中含水量和溶剂极性影响小等优点。     

超声-微波协同萃取分离、气相色谱-质谱联用测定土壤中多环芳烃

建立了常温常压条件下超声-微波协同萃取分离、气相色谱-质谱法（GC-MS）测定土壤样品中微量多环芳烃的方法,结果表明：在土壤含水量和无机盐质量分数分别为10％和6％时,以正已烷-二氯甲烷（1＋1）混合溶液40mL作萃取溶剂,采用100W微波辐射功率（超声振动功率固定为50W）萃取9min,模拟土壤样品中多环芳烃平均回收率可达86．9％,其相对标准偏差为3．6％;通过与索氏抽提、高压密闭微波和开放式微波、直接超声波和间接超声波等萃取方法相比,证明此方法具有样品容量大、萃取时间短、萃取效率高、重现性好等优点。     

两相溶剂萃取黄连木籽油制备生物柴油

以黄连木籽为原料,采用乙醇/异己烷两相不互溶溶剂对其进行萃取处理.考察了乙醇／异己烷体积比、萃取温度和萃取时间对萃取过程的影响.通过实验确定最佳的萃取条件为,黄连木仁粉50 g,乙醇异己烷总体积300 mL,乙醇/异己烷体积比为50∶50,萃取温度40℃,萃取时间30 min.在此条件下,黄连木籽油出油率达到99.5％...     

一种简单的抽提法

一种简单的抽提法王荣民张海涛何玉凤王云普（西北师范大学化学系兰州７３００７０）固体物质的抽提，一般是在所谓的索氏（Ｓｏｘｈｌｏｔ）抽提器中进行的。我们在实验过程中发现使用现成的磨口索氏抽提器有诸多不便：首先，索氏抽提器的成套性不好，这是因为索氏抽提器...     

超声微波协同萃取-气相色谱法测定土壤中邻苯二甲酸酯类化合物

研究了超声微波协同萃取-气相色谱测定土壤中的邻苯二甲酸酯类化合物。考察了萃取溶剂、微波功率、萃取时间等因素对回收率的影响,得到了最佳萃取条件为:以正己烷/丙酮(1∶1)为萃取剂,溶剂用量为60 mL,微波辐射功率为100 W(超声功率固定为50 W),萃取12 min。该条件下,模拟土样中酞酸酯的平均回收率可达92.5%。方法的检出限为0.05~0.16 mg/kg,相对标准偏差(RSD)5.8%。与直接超声、开放式微波萃取法相比,此法具有明显的优势。方法用于实际土样的测定,所得结果与索氏抽提的结果相当。     

基于磁性纳米材料的固相萃取技术研究新进展

<正>由于实际样品中待测物的含量往往较低,且基质复杂,所以在进行定量分析时往往需要对样品进行前处理,以达到减小干扰组分、浓缩富集待测组分以适于特定检测分析目的的需要,因此样品前处理技术是整个分析过程中最关键的一环。传统的样品前处理方法如液液萃取、索氏抽提、振荡提取、固相萃取等存在样品需要量较大、萃取时间长、使用大量     

食品包装材料中13种增塑剂的毛细管气相色谱法测定

建立了索氏提取、固相萃取净化浓缩、毛细管气相色谱法测定塑料食品包装材料中13种增塑剂的方法.优化了固相萃取淋洗剂、洗脱剂和洗脱剂体积等参数.样品经正己烷索氏提取后,用硅胶小柱净化浓缩.以正己烷-甲苯为淋洗剂,2 mL乙酸乙酯为洗脱剂.过滤后的洗脱液用气相色谱仪分析.结果显示,13种增塑剂在0.1～1000 mg/L范围...     

ICP-AES测定铀污染土壤植物中铀的研究

采用电感耦合等离子体发射光谱(ICP-AES)对铀污染土壤植物中铀的测定方法进行了研究.在λU385.958 nm处,选择了仪器的最佳工作条件,考察了酸度和常见共存元素对测定的干扰情况,并且对比了干灰化消解和湿式消解对测定的影响.研究发现2%硝酸溶液为最佳介质,干扰离子对测定没有显著影响,干灰化消解比湿式消解得彻底.在选定条件下,方法检出限为0.18 mg·L-1,测定下限为0.61 mg·L-1,5.0000 mg·L-1的铀标准溶液的相对标准偏差RSD(n=10)为0.81%,方法回收率为96.2%～106.2%.该方法操作简单,快速.结果表明,用ICP-AES测定铀污染土壤植物样品中的铀是可行的.     

测定血清中Na 含量不确定度的评定

对血清中Na离子含量的测量不确定度进行评定。不确定度的来源主要包括Na离子标准工作液的配制过程、血清样品的定容消化制备、标准曲线拟合、钠离子各分量不确定度的合成等引入的不确定度计算出各分量的不确定度,通过合成得到测量结果的合成不确定度、扩展不确定度及测试结果的报告形式。     

Interpretation of inorganic arsenic metabolism in humans in the light of observations made in vitro and in vivo in the rat

The toxicity of inorganic trivalent arsenic for living organisms is reduced by in vivo methylation of the element. In man, this biotransformation leads to the synthesis of monomethylarsonic (MMA) and dimethylarsinic (DMA) acids, which are efficiently eliminated in urine along with the unchanged form (As_i). In order to document the methylation process in humans, the kinetics of As_i, MMA and DMA elimination were studied in volunteers given a single dose of one of these three arsenicals or repeated doses of As_i. The arsenic methylation efficiency was also assessed in subjects acutely intoxicated with arsenic trioxide (As₂O₃) and in patients with liver diseases. Several observations in humans can be explained by the properties of the enzymic systems involved in the methylation process which we have characterized in vitro and in vivo in rats as follows: (1) production of As_i metabolites is catalyzed by an enzymic system whose activity is highest in liver cytosol; (2) different enzymic activities, using the same methyl group donor (S-adenosylmethionine), lead to the production of mono- and di-methylated derivatives which are excreted in urine as MMA and DMA; (3) dimethylating activity is highly sensitive to inhibition by excess of inorganic arsenic; (4) reduced glutathione concentration in liver moderates the arsenic methylation process through several mechanisms, e.g. stimulation of the first methylation reaction leading to MMA, facilitation of As_i uptake by hepatocytes, stimulation of the biliary excretion of the element, reduction of pentavalent forms before methylation, and protection of a reducing environment in the cells necessary to maintain the activity of the enzymic systems.     

Production of radicals in the ozonolysis of propene in air

Radical production in the ozonolysis of propene in air was monitored directly by a peroxy radical chemical amplification (PERCA) instrument at room temperature (298±2 K) and atmospheric pressure (1×105 Pa). The ozonolysis reactions were conducted in a flow tube under pseudo-first-order conditions for ozone. The decay in ozone was calculated based on reaction time tr and effective rate constant keff (keff = k1[C3H6]0)) for the ozone-propene reaction. The total radical yields relative to consumed ozone were d...     

Kinetics of dehydration in chelates of quinones involved in photosystem-II

The solid-state deaquation of thetrans- andcis-oximates of lawsone (I) and phthiocol (II) with cobalt(II) was investigated by means of non-isothermal thermogravimetry. The modes of deaquation during the thermolyses of hydrated oximates of (I) and (II) with compositions CoL₂·2H₂O were compared. The weight lossvs. temperature data were treated by using the Coats and Redfern relations. The kinetic data support a rearrangement-type mechanism for the deaquation of the oximate of phthiocol. TheE _a values for both the ligands and water molecules were found to be 23 kJ/mol.

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Zusammenfassung Mittels nichtisothermer Thermogravimetrie wurde die Dehydratation der trans- und cis-Kobalt(II)-oximate von Lawson (I) und Phthiokol (II) untersucht. Die Arten der Dehydratation während der Thermolyse der hydratierten Oximate von (I) und (II) mit der Zusammensetzung CoL₂·2H₂O wurden verglichen. Bei der Auswertung der Massenverlust-Temperatur-Daten wurden Coats-Redfern Beziehungen angewendet. Die kinetischen Daten bekräftigen einen Umlagerungsmechanismus für die Dehydratation des Oximates von Phthiokol. DieE _a Werte betragen sowohl für die Liganden als auch für Wasser etwa 23 kJ/mol.

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- - (I) (II) . I II CoL₂ · 2₂ . -. . _a , 23 · ^–1

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Use of matrix-modifiers in atomic-absorption determination of chromium in argillites

The direct atomic-absorption determination of chromium in argillites, without preliminary concentration and separation, has been studied. A map of selective flame zones for determining Cr in argillites has been designed. An express method for determining Cr in Estonian argillites has been suggested.     

Effect of vibration in processes of structure formation in polymers

It was shown that the strength characteristics of the samples produced from thermoplastics (low density polyethylene, polyamide 6, Armamid, and polyethylene terephthalate) increase as a result of short vibration treating with a frequency close to that of natural vibrations of the structural elements.