微波消化-氢化物发生原子吸收光谱法测定鳗鱼中的汞

对微波消化一氢化物发生原子吸收光谱法测定鳗鱼中的汞进行了研究。采用HNO3-H2O2消化体系，利用微波消化样品，以硼氢化钠为还原剂，用氢化物发生原子吸收光谱法测定鳗鱼中的汞。在最佳微波消化条件和测定条件下，线性范围为0～40．0μg／L，检出限为0．02μg／L，测定结果的相对标准偏差为2．3％-3．6％，回收率为93．2％-101．0％。     

微波消解-ICP-AES法测定茶叶中微量元素

在微波消解器中,以ＨＮＯ３－ＨＣｌＯ４分解茶叶,然后用ＩＣＰ－ＡＥＳ法测定样品溶液中的Ｂａ,Ｃａ,Ｃｕ,Ｆｅ,Ｍｎ,Ｐｂ,Ｚｎ,本法简便快速,污染少,回收率为９０．２％￣１０６．３％,相对标准偏差为１．７％￣６．２％。     

间接紫外光度法测定食品添加剂乳酸亚铁中Fe^3^＋含量

基于Ｆｅ＾３＾＋能将抗坏血酸量氧化的特性，通过测定反庆前后体在紫外区２４５ｎｍ处吸光度值的差值，间接测定样品中Ｆｅ＾３＾＋的含量。试验结果表明，Ｆｅ＾３＾＋含量在０－２００μｇ／２５ｍＬ范围内服从比耳定律。应用于乳酸亚铁样品中Ｆｅ＾３＾＋含量的测定，回收率为９７．３％－１０１．７％，相对标准偏差为０．８％－２．７％。测定结果与标准方法基本一致。     

微波消解-分光光度法测定催化裂化原料中铁和镍

采用微波消解技术处理催化裂化原料，用分光光度法测定样品中的铁和镍。详细考察了微波消解消化剂的种类和用量，消解时间，消解压力和消解功率对消解效果的影响，确定了最佳微波消解程序。将微波消解技术与常规分光光度法结合测定催化裂化原料中的铁和镍，与常压溶样方法测定结果相吻合。该方法的相对误差小于0．9％，相对标准偏差(n=5)小于2．7％，两种样品制备方法的加标回收率均在95．2％～102．4％之间。实验结果表明：该方法简便、快速、准确、节省试剂、无环境污染，在催化裂化原料质量检测方面切实可行。     

单柱离子色谱法测定过热器管垢和锅炉垢中铁、镁和钙的含量

首先用碱熔融法分解试样,然后加抗坏血酸将试液中的Ｆｅ３＋还原为Ｆｅ２＋,再用离子色谱法测定试液中的Ｆｅ２＋,Ｍｇ２＋和Ｃａ２＋。采用Ｓｈｉｍ－ｐａｃｋＩＣ－Ｃｌ阳离子交换柱分离样品离子,以０．２５ｍｍｏｌ／Ｌ乙二胺－０．５０ｍｍｏｌ／Ｌ柠檬酸（ｐＨ４．５０）为流动相,以ＣＤＤ－６Ａ电导检测器检测,使被测组分得到满意的分离和检测。Ｆｅ,Ｍｇ和Ｃａ的加标回收率均在９０％以上。测定结果与原子吸收光谱法测定结果相近。     

空气－C_2H_2火焰原子吸收光谱法测定中草药（鸦胆子、补骨脂）中的铁、锰

用空气－Ｃ２Ｈ２火焰原子吸收光谱法测定了中草药（鸦胆子、补骨脂）中的Ｆｅ、Ｍｇ含量，讨论了测定条件，结果令人满意，方法的回收率：Ｆｅ９８．２０％～１０４．９％，ＣＶ＝１．０６％～１．０７％，Ｍｎ９９．４％～１０１％，ＣＶ＝０．５２％～１．９４％。     

氢化物发生原子荧光光谱法测定污泥中的砷

用氢化物发生原子荧光光谱法测定污泥中的砷.分别用微波消解、湿法消解两种方法处理污泥样品，微波消解效果优于湿法消解，在最佳实验条件下，砷的检出限为0.04μg/L，回收率为94．2％～104.8％，测定结果的相对标准偏差为2．22％～4．23％。     

空气—C2H2火焰原子吸收光谱法测定中草药（鸦胆子,补骨脂）中…

用空气－Ｃ２Ｈ２火焰原子吸收光谱法测定了中草药中的Ｆｅ、Ｍｇ含量，讨论了测定条件，结果令人满意，方法的回收率：Ｆｅ９８．２０％－１０４．９％，ＣＶ１．０６％－１．０７％，Ｍｎ９９．４％－１０１％，ＣＶ＝０．５２％－１．９４％。     

微波消解-冷原子吸收光谱法测定烤鳗中的总汞

本文采用密封微波消解技术处理样品,对烤鳗样品一次性进行微波消化,然后用氢化物发生-冷原子吸收光谱法测定烤鳗中的总汞,回收率均在80％～95％之间。方法简便、快速、准确,用于烤鳗样品中汞含量的测定,结果满意。     

测定天然和栽培缬草根金属元素的微波和干灰化消解-FAAS法

采用微波消化法和马弗炉干灰法处理天然和栽培缬草根样品，火焰原子吸收光谱法连续测定样品中金属元素，分别检出12种和11种元素，其中Zn、Cu、Fe、Co、Mn、Ni、Cr为生命必需微量元素；两种样品各用两种消化法处理，测得金属元素及含量有差异，干灰法操作简单，但消化温度高、时间长、易挥发、元素容易损失，使检测值偏低；而微波消化法简便、省时、损失减少；两种消化法的加标回收率分别为95％-100％和96％-105％。     

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。     

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.     

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.     

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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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...     

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.