Applications of enzyme-catalysed reactions in trace analysis-III Determination of silver and thiourea by their combined inhibition of invertase

Thiourea has been found to enhance the inhibition of invertase by silver ions. The effect is applied to the determination of 1–5 × 10⁻⁷ M silver and of 10⁻⁷–10⁻⁸ M thiourea. A mechanism is suggested for the enhancement.     

Applications of enzyme-catalysed reactions in trace analysis-VI Determination of mercury and silver by their inhibition of yeast alcohol dehydrogenase

The inhibition of yeast alcohol dehydrogenase is applied to the determination of 2-200 ng of mercury(II) and 1-100 ng of silver. The enzyme, when used to catalyse the oxidation of ethanol, or the reverse reaction, is equally sensitive to inhibitors.     

Applications of enzyme-catalysed reactions in trace analysis-VII Determination of lead and indium by their inhibition of isocitrate dehydrogenase

The inhibition of isocitrate dehydrogenase by lead, indium and calcium has been studied. Methods for the determination of 0.024-1 mug of lead and indium, based on this inhibition, are outlined. Lead may be separeted from some interfering ions by extraction with tributyl phosphate in isobutyl methyl ketone, before application of the enzymic reaction.     

Applications of enzyme-catalysed reactions in trace analysis-IV Determination of beryllium and zinc by their inhibition of calf-intestinal alkaline phosphatase

Methods are described for the determination of beryllium (18-90 ng) and zinc (0.6-6 mug), based on their inhibition of calf-intestinal alkaline phosphatase.     

Applications of enzyme-catalysed reactions in trace analysis-II Determination of cyanide, sulphide, and iodine with invertase

Methods are described for the determination of cyanide (10⁻⁸–10⁻⁵M and sulphide (10⁻⁷–10⁻⁵ M) based on the de-inhibitory effect of these ions on invertase inhibited by mercury(II) or by silver. Iodine (0.1–3 μg) may be determined by its inhibition of invertase.     

Applications of enzyme-catalysed reactions in trace analysis-V Determination of zinc and calcium by their activation of the apo-enzyme of calf-intestinal alkaline phosphatase

The activation of the apo-enzyme of calf-intestinal alkaline phosphatase by zinc in the presence and absence of magnesium 4 x 10(-4)M) is applied to the determination of 6-65 ng and 65-650 ng of zinc, respectively. The activation of the apo-enzyme by calcium in the presence of 1.4 x 10(-7)M zinc is used to determine 1-4 mug of calcium. The mechanism of the re-activation effects is discussed.     

Limitations in the analytical use of invertase inhibition for the screening of trace mercury content in environmental samples.

The possibility of screening the mercury(II) content in real environmental samples based on inhibition of the activity of dissolved invertase has been examined. The extent of inhibition was measured with an amperometric glucose biosensor with glucose oxidase immobilized on a membrane. Data concerning the stability and reproducibility of measurements are provided. The effects of heavy metals on the inhibition of invertase, together with that of common anions such as chloride, nitrate and sulfate are reported. The determination of mercury using this procedure has been carried out in samples of natural and waste water samples of various origins already analyzed by ICP-AES, by spiking ppb levels of mercury(II). Differences in the inhibiting effect of the samples and in the recoveries were found and are discussed.     

Determination of mercury(II) by invertase enzyme inhibition coupled with batch injection analysis

The determination of mercury(II) ions at the trace level by inhibition of the invertase enzyme-catalysed hydrolysis of sucrose into glucose and fructose coupled to electrochemical batch injection analysis was investigated using two approaches. In the first, the glucose produced was detected by injection of 100 microliters samples into the batch injection cell containing a platinum electrode modified by immobilised glucose oxidase. In the second, the glucose and fructose present in injected samples were oxidised directly at a copper-modified glassy carbon electrode. The experimental parameters were optimised and the degree of enzyme inhibition by mercury(II) ions under both conditions was measured. Mercury concentrations in the ng ml-1 range were determined by these two techniques with low sample and reagent consumption. Comparison is made between the two methods and perspectives as a screening test for field application are indicated.     

阻抑动力学光度法测定痕量尿素

研究了在酸性介质中,痕量尿素对NO2-催化KBrO3氧化维多利亚绿G的阻抑作用,通过测量617 nm处吸光度的变化,建立了测定痕量尿素的阻抑动力学光度分析的新方法。在最佳实验条件下,测定尿素的线性范围为0.0~0.14mg/L,检出限为5.0×10-6g/L。对2.0μg/25 mL进行10次平行测定的相对标准偏差为2.8%。并试验了共存离子对催化反应的影响,常见的离子均不干扰测定。方法可用于废水中痕量尿素的测定。     

阻抑-褪色光度法测定痕量间苯二酚

在NH3 NH4Cl介质中 ,间苯二酚能阻抑Fe(Ⅲ )为催化剂 ,邻菲罗啉为活化剂的过氧化氢氧化甲酚红的褪色反应。研究了该反应的最佳条件和动力学参数。建立了一种测定痕量间苯二酚的新方法。方法检出限为 3 5× 1 0 - 4 g·L- 1 ,测定范围为 0 .30mg/L～ 7.0mg/L ,方法可用于废水中间苯二酚的测定     

Determination of trace impurities in high-purity reagents by mercury thin-film anodic-stripping voltammetry

Summary The use of an amalgamated silver-wire electrode, providing a relatively large rate of film area to volume of mercury, seems to present several advantages over the use of the hanging mercury drop electrode (HMDE) for the determination of trace impurities by anodic-stripping voltammetry (ASV). Peak resolution and sensitivity have both been improved by use of the mercury thin-film electrode (MTFE). Preparation, conservation and treatment of the electrode are simple, requiring brief etching of a silver wire with dilute nitric acid, followed by rinsing, drying and direct amalgamation with mercury. The MTFE is stored in mercury, the excess of which is wiped off before use; it is cleaned by anodic-stripping electrolysis at positive potentials. Under these conditions, ASV produces reproducible peak-heights, with excellent dependence on electrolysis time and concentration of impurities. Samples containing nanogram quantities or less of the impurities of interest, are analysed by a four-step procedure: (1) prolonged pre-electrolysis of the supporting electrolyte,in situ in the voltammetric cell, on an auxiliary MTFE; (2) ASV of the supporting electrolyte on a cleaned MTFE; (3) ASV after the dissolution of the sample; (4) ASV after the addition of standards. The method is suitable for the estimation of traces of Zn(II), Cd(II), Tl(I), Pb(II), Sb(III) and Cu(II) in various high-purity reagents. Most impurities have been adequately determined at the 10^–9–10^–8 M level by the regular procedure, and at the 10^–10–10^–9 M level may be determined if the preconcentration (electrolysis) time and rates of potential sweep are increased. The only disadvantage of the method is that the overvoltage of hydrogen evolution is lower for the MTFE than the HMDE.

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Zusammenfassung Die Verwendung einer amalgamierten Silberdrahtelektrode mit einer im Vergleich zum Quecksilbervolumen großen Oberfläche bietet offenbar verschiedene Vorteile bei der Bestimmung von Spurenbeimengungen durch Anodic-stripping Voltammetry (ASV) gegenüber einem hängenden Quecksilbertropfen (HMDE). Peakauflösung und Empfindlichkeit wurden mit Hilfe der Quecksilberdünnschicht-Elektrode (MTFE) verbessert. Herstellung, Aufbewahrung und Behandlung solcher Elektroden sind einfach; sie erfordern eine kurze Anätzung eines Silberdrahtes mit verd. Salpetersäure, Spülung, Trocknung und Amalgamierung mit Quecksilber. Diese Elektroden werden in Quecksilber aufbewahrt, dessen Überschuß vor der Verwendung weggewischt wird. Sie werden durch Anodic-stripping-Elektrolyse bei positivem Potential gereinigt. Unter diesen Bedingungen gibt ASV reproduzierbare Peakhöhen, die zu der Elektrolysezeit und der Konzentration der Beimengungen in gutem Abhängigkeitsverhältnis stehen. Proben, die Nanogrammengen solcher Beimengungen enthalten, werden nach einem Vierstufenverfahren analysiert: 1. verlängerte Vorelektrolyse des Trägerelektrolyten mittels einer Hilfs-MTFE im Voltammetriegefäß; 2. ASV des Trägerelektrolyten mit einer gereinigten MTFE; 3. ASV nach Auflösung der Probe; 4. ASV nach Zugabe der Standards. Die Methode eignet sich zur Bestimmung von Spuren Zn(II), Cd(II), Tl(I), Pb(II), Sb(III) und Cu(II) in verschiedenen hochreinen Reagenzien. Die meisten dieser Verunreinigungen wurden in der Größenordnung 10^–9 bis 10^–8 M mit Hilfe des regulären Verfahrens bestimmt. In der Größenordnung 10^–10 bis 10^–9 M können sie bei Verlängerung der Anreicherungszeit (elektrolytisch) und Erhöhung des Potentialbereichs bestimmt werden. Der einzige Nachteil des Verfahrens ist, daß die Überspannung zur Wasserstoffentwicklung geringer ist als mit dem hängenden Quecksilbertropfen.

     

大体积进样-原子荧光光谱法 测定海水中痕量汞

海洋中的汞在生物体内会转化为毒性高的甲基汞,影响海洋生物体的健康,进而威胁到人类的健康。同时,由于汞元素的记忆效应,使其会残留在光谱仪器设备中,影响仪器空白值和参数设置,以及测量结果的准确性和可靠性。海水中的汞含量处于超痕量水平,其分析检测是目前的难点之一。本文研究了一种大体积进样-原子荧光光谱法测定海水中痕量汞的方法,考察了不同前处理方式、酸的种类、还原剂浓度和原子化方式对检测的影响,并针对性利用烷基汞验证了不同条件下的检测结果,对方法进行了改进和验证,并对不同海域的海水进行了检测。实验结果表明：采用大体积进样,用盐酸代替硫酸,检测低浓度样品结果更准确;用甲基汞、乙基汞加标和低浓度还原剂对比验证过硫酸钾消解前处理时室温消化24h和加热煮沸1min两种消解方式,两种方式的加标回收率均接近100%;测量不同海域海水样品平行性好,结果准确,该方法对不同海域海水具有普遍适用性。     

Determination of trace amounts of mercury in rock samples

Summary A precise and accurate method is described for the measurement of ng quantities of mercury in inorganic samples such as rock, mineral ores and soil. The mercury is distilled from pulverized samples and collected on a silver gauze absorber. The mercury is then rapidly desorbed from the silver element using heat, and it is carried by gas entrainment into the measuring cell of an ultraviolet absorption analyzer. Readout of the mercury content can be made by measurement of peak heights on a strip chart recording, but more elegantly and accurately by the digital printout from a GC integrator. Calibration of the instrumental assembly, by injection of measured quantities of saturated mercury vapor, is simple, rapid and accurate.

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Zusammenfassung Eine genaue Methode zur Bestimmung von Nanogrammengen Quecksilber in anorganischem Material wie Gesteinen, Erzen und Bodenproben wurde beschrieben. Aus den gepulverten Proben wird das Hg abdestilliert und auf einem Silberdrahtnetz gesammelt. Dann wird es rasch durch Erwärmen desorbiert und mit einem Gasstrom in die Meßzelle eines UV-Ab-sorptionsgerätes geleitet. Die Ermittlung des Quecksilbergehaltes kann aus der Peakhöhe eines Schreibers, besser mit dem Digitalzähler eines GC-Integrators erfolgen. Die Eichung des Gerätes durch Einleiten gemessener Mengen von gesättigtem Quecksilberdampf ist einfach rasch und genau.

     

银纳米粒子共振光散射光谱法测定痕量CTMAB

利用十六烷基三甲基溴化铵(CTMAB)与银纳米粒子作用生成的聚集体,使体系的共振光散射(RLS)强度明显增强,建立了一种快速、简便的测定痕量CTMAB的RLS光谱法。考察了p H值,反应最佳时间,试剂加入顺序等因素对测定CTMAB的影响。实验结果表明,在p H值为10.88,作用时间为10 min,银纳米粒子浓度(以银原子计算)为2.5×10-3mol·L-1,按CTMAB、BR、银纳米粒子为添加顺序的条件下,测定CTMAB的线性范围为:5.0×10-9~5.0×10-7mol·L-1,检出限为3.8×10-9mol·L-1。该法用于合成样品中CTMAB的测定,灵敏度高,重现性好,结果准确。     

Determination of trace level mercury in biological and environmental samples by neutron activation analysis

Sorptivity studies with Chelex 100 column indicated chloride to be the best medium for the sorption of mercury. A radiochemical separation procedure has been developed for the determination of mercury by neutron activation analysis utilizing sorption of mercury on Chelex 100. The method was checked with Orchard Leaves and Tuna Fish standards from the National Institute of Standards and Technology.     

固体进样-直接测汞仪法测定银精矿汞量

建立了固体进样-直接测汞仪法测定银精矿中汞的分析方法。试样无需进行样品前处理,将银精矿试样直接称量于样品舟中,在氧气气氛中,试样在分解炉中经历干燥和高温热分解,汞被还原成汞原子,再被氧气流带进汞齐化管中进行汞齐化反应,其中的汞被选择性吸附,于900℃加热释放出汞蒸汽,,汞蒸气被氧气流带入单波长光学吸收池进行原子吸收测量,方法检出限为0.007μg/g,测定结果的相对标准偏差为1.77%~3.07%(n=11),加标回收率为98.08%～102.43%。方法操作简单、快速稳定、重现性良好,适合于银精矿中微量汞的测定。     

阻抑动力学分光光度法测定痕量碘

研究了在稀H3PO4介质中,痕量碘离子对NO-2催化溴酸钾氧化吖啶橙的阻抑作用,建立了测定痕量碘离子的阻抑动力学光度分析的新方法。测定碘离子的线性范围为0～0.40μg/mL,检出限为7.3×10-9g/mL。已用于食品中的微量碘的测定。     

Determination of trace level of selenium and mercury in photographic emulsions by atomic spectroscopy techniques

Trace level of selenium and mercury in photographic emulsion are used to improve photographic properties. The presence of silver halide in photographic emulsion does not allow the application of the most common analytical methods such as Hydride Generation Atomic Absorption Spectrometry (HG-AAS) and cold vapour Atomic Absorption Spectrometry (CV-AAS). Besides, silver removal was not quantitative, leading to a significant loss of the analytes and low reproducibility. The present work suggest the use of inductively coupled plasma Atomic Emission Spectrometry (ICP-AES) equipped with Ultrasonic Nebulizer (USN) for direct aqueous samples analysis at microgram l-1 level (d.l. 5.1 ppb for Hg and 6.1 ppb for Se).     

Determination of major components and trace elements in ancient silver by thermal neutron activation analysis

Thermal neutron activation of minute samples of ancient silver objects has provided useful information concerning their silver, copper and gold content. The results of such analysis of eighteen Sasanian silver objects are discussed together with consideration of the sampling problems involved. In order to extend these measurements to include other elements, an isotopic exchange system has been developed to separate other activities present in irradiated silver specimens quantitatively from the silver, copper and gold activities. Following exchange with cuprous and silver iodides it has been possible to count quantitatively the activity of fourteen additional elements: As, Br, Co, Cr, Fe, Hg, Ir, K, Mn, Na, Sb, Sc, Se and Zn. Research supported in part by the U. S. Atomic Energy Commission.