Comparison of activation methods for mercury determination

A comparative study is made on different activation methods for mercury analysis. Mercury concentrations down to 0.1 ppm were determined instrumentally via the isotopes¹⁹⁷Hg (T=65 h) and²⁰³Hg (T=47 d). A high-resolution Ge(Li) detector was used in measuring the activity and a small computer for data reduction. Up to 500 samples were measured daily. Chemical separations were performed on samples with low mercury concentrations. Sensitivity of 0.01 ppm was attained by precipitating HgS from basic solutions and counting¹⁹⁷Hg on NaI(T1) detector. A new rapid instrumental method was also developed based on^199mHg (T=43 min). This short-lived isotope was activated with resonance neutrons. The sensitivity of the method is 0.5 μg and it requires only 1 hr.     

固体进样直接测定法测定铜精矿中汞

建立了固体进样直接测定法测定铜精矿中汞含量的方法。铜精矿样品在测汞仪的分解炉中经300℃干燥和750℃高温热分解后,汞被催化分解为汞原子,于850℃齐化成金汞齐。汞蒸气被氧气流带入单波长光学吸收池,在波长253.7 nm处测量汞的吸光度,采用标准曲线法计算汞量。方法的线性范围分别为0~1.00,0~100μg/mL,线性相关系数为0.9999,检出限分别为0.10,0.04 ng/g。5个汞含量不同的铜精矿样品测定结果的相对标准偏差为2.14%~4.35%(n=11),样品加标回收率为92.00%~104.02%。采用该方法分别对2个铜精矿样品和铜精矿国际标准物质进行测定,测定结果与标准分析方法测定值和标准物质标示值基本一致。该方法简便、快速、准确,可以作为标准方法推广使用。     

Comparison of conventional filtration and a denuder-based methodology for sampling of particulate-phase mercury in ambient air

This paper compares the results of total atmospheric particulate-phase mercury determinations using samples collected by two methods. The conventional filtration method (FM) collects airborne particulate matter first, whereas the denuder-based method (DM) removes gaseous-phase mercury prior to particulate matter collection. In each case, particulate-phase mercury (PM) is collected on a quartz fiber disc held in a miniaturized device and is analyzed using a pyrolysis/gold amalgamation/thermal desorption/cold vapor atomic fluorescence spectrometry (CVAFS) technique. The results show that the concentrations of PM determined using the samples collected by DM are higher than those determined using the samples collected by FM. Evidence presented shows that the higher results are due to mercury-bearing gold particles flaking off from the gold-coated denuder surfaces in the denuder-based sampling system.     

Comparison of gas chromatographic hyphenated techniques for mercury speciation analysis

In this study, we evaluate advantages and disadvantages of three hyphenated techniques for mercury speciation analysis in different sample matrices using gas chromatography (GC) with mass spectrometry (GC-MS), inductively coupled plasma mass spectrometry (GC-ICP-MS) and pyrolysis atomic fluorescence (GC-pyro-AFS) detection. Aqueous ethylation with NaBEt(4) was required in all cases. All systems were validated with respect to precision, with repeatability and reproducibility <5% RSD, confirmed by the Snedecor F-test. All methods proved to be robust according to a Plackett-Burnham design for 7 factors and 15 experiments, and calculations were carried out using the procedures described by Youden and Steiner. In order to evaluate accuracy, certified reference materials (DORM-2 and DOLT-3) were analyzed after closed-vessel microwave extraction with tetramethylammonium hydroxide (TMAH). No statistically significant differences were found to the certified values (p=0.05). The suitability for water samples analysis with different organic matter and chloride contents was evaluated by recovery experiments in synthetic spiked waters. Absolute detection and quantification limits were in the range of 2-6 pg for GC-pyro-AFS, 1-4 pg for GC-MS, with 0.05-0.21 pg for GC-ICP-MS showing the best limits of detection for the three systems employed. However, all systems are sufficiently sensitive for mercury speciation in environmental samples, with GC-MS and GC-ICP-MS offering isotope analysis capabilities for the use of species-specific isotope dilution analysis, and GC-pyro-AFS being the most cost effective alternative.     

Trueness, precision, and detectability for sampling and analysis of organic species in airborne particulate matter

Recovery, precision, limits of detection and quantitation, blank levels, calibration linearity, and agreement with certified reference materials were determined for two classes of organic components of airborne particulate matter, polycyclic aromatic hydrocarbons and hopanes, using typical sampling and gas chromatography/mass spectrometry analysis methods. These determinations were based on initial method proficiency tests and on-going internal quality control procedures. Recoveries generally ranged from 75% to 85% for all target analytes and collocated sample precision estimates were generally better than 20% for polycyclic aromatic hydrocarbons and better than 25% for hopanes. Results indicated substantial differences in data quality between the polycyclic aromatic hydrocarbons and hopanes. Polycyclic aromatic hydrocarbons demonstrated better collocated precision, lower method detection limits, lower blank levels, and better agreement with certified reference materials than the hopanes. The most serious area of concern was the disagreement between measured and expected values in the standard reference material for hopanes. With this exception, good data quality was demonstrated for all target analytes on all other data quality indicators.     

The preparation of silver absorbers for sampling airborne mercury

Microchimica Acta - The procedure for the preparation of MC-8 silver absorbers is described. Silver gauze, 30–60 mesh, is used after heat activation at 800°. The construction of the...     

Generation,sampling and chromatographic analysis of particulate matter in dilute sidestream tobacco smoke

The sampling and gas chromatographic separation of the particulate matter of sidestream tobacco smoke for high-molecular-weight compounds are described. Four n-alkanes (C₂₇, C₂₉, C₃₁ and C₃₃) were identified and their relationship to the particulate levels was established. The sidestream yields of these compounds for several cigarette types, including regular, low- and ultra-low-tar filtered and high-tar unfiltered varieties are reported. Concentrations in diluted smoke at particulate levels similar to ambient tobacco smoke were also determined. Methods for generating test atmospheres of sidestream smoke at low-level, uniform concentrations are described.     

Simultaneous on-line size and chemical analysis of gas phase and particulate phase of cigarette mainstream smoke

This paper describes the combined set-up of on-line chemical analysis of gas phase by single-photon ionisation/resonance enhanced multiphoton ionisation–time-of-flight mass spectrometry (SPI/REMPI-TOFMS) and on-line particle size analysis by differential electrical mobility particle spectrometry (DMS 500) for the investigation of fresh cigarette mainstream smoke. SPI is well suited for the investigation of a great variety of organic species, whereas REMPI is highly sensitive for aromatic compounds. Gas phase measurements of filtered and unfiltered smoke are possible with the SPI/REMPI-TOFMS in order to determine the influence of the presence of particles on the chemical composition of the gas phase. Initial results are shown for the characterisation and comparison of three pure Virginia tobacco research cigarettes having filter ventilations of 0%, i.e. no filter ventilation, 35% and 70% ventilation. The three cigarette types are smoked under two different smoking regimes, a standard regime using puff parameters equivalent to the conventional International Standard Organisation regime and a more intense smoking regime. For the gas phase, qualitative puff-by-puff resolved yields of three selected compounds (acetaldehyde, phenol and styrene) are shown and compared. For particulate matter, particle number, count median diameter and total surface area are illustrated on a puff-by-puff basis. Yields of the chemicals analysed, puff number and surface area are in good agreement with the intensity of the smoking regime and the dilution of smoke by filter ventilation. However, gaseous compounds are influenced differently, depending whether an absolute particle filter is present or not, i.e. they can be totally removed (phenol), partially removed (styrene) or not affected (acetaldehyde). For particle analysis, the count median diameter decreases from puff to puff and is strongly dependent on the smoking regime and ventilation rate. Thereby, 0% ventilated cigarettes smoked under the intense regime result in the smallest count median diameters of ca. 180 nm, whereas 70% ventilated cigarettes smoked with a standard regime lead to the largest values of up to 280 nm. As particle diameter increases, particle number decreases as a consequence of increasing time for particle coagulation.     

大气颗粒物中有机物色谱分析的样品制备技术

大气颗粒物中有机物成分分析对深入研究大气颗粒物对人类健康、环境、气候、生态的影响,解析气溶胶来源,制定颗粒物控制相关法规,以及风险管理方法具有重要意义。由于颗粒物中的有机组分种类繁多,分析复杂,目前仅10%~20%的有机物得到了定性和定量分析。因此,大气细颗粒中有机物的分析已成为环境分析领域的优先发展方向。色谱是大气颗粒物中有机物分析的主要方法,而样品制备则是影响分析速度和精度的关键步骤。本文对颗粒物中有机组分色谱分析前的样品制备方法进行了综述,介绍了索氏提取、超声辅助提取、微波辅助提取、加压溶剂提取等溶剂提取方法以及热解吸提取方法,并重点介绍了这些方法在大气颗粒物样品处理中的应用,总结了各种方法的优缺点。     

Multicomponent analysis: Comparison of various graphical and numerical methods

The performance of several graphical (zero-crossing and derivative quotient spectra with standardized divisor) and numerical methods (MULTIC and PLS) for the resolution of binary and ternary mixtures of species is compared. Numerical methods were found to be specially suited to multicomponent analysis, particularly for mixtures containing more than two analytes with highly overlapped spectra. The results obtained by using the compared methods to analyse various synthetic mixtures of acetylsalicylic acid, caffeine and thiamine were quite consistent and errors in the simultaneous quantification of the analytes amounted to less than 5% in all instances.     

Comparison of different extraction and detection methods for sugars using amino-bonded phase HPLC

In this study, different methods are compared in order to quantitate individual sugars extracted from apple samples using methanol and water. Glucose, fructose, and sucrose are separated in 20 min using an amino-bonded carbohydrate column and a 75:25 acetonitrile-water mobile phase, followed by UV (190 nm) and refractive index detection. Variations in the sugar profiles are observed using different extraction or detection methods (or both) at a 1.4-mL/min flow rate. The data obtained show differences (p < 0.01) from both extraction or detection methods. The highest contents of free sugars studied occur in samples extracted with water.     

Comparison of passive and active sampling methods for the determination of nitrogen dioxide in urban air

Three different methods for sampling and determination of nitrogen dioxide in urban air are compared: an NO/NO_x-monitor and an active (pumped) and a passive sampling method. For the latter two methods, sodium iodide is used as absorbent. For weekly averages the results from the passive sampler are within 10–20% of the results for the two other methods in the concentration range 15–30 μg NO₂/m³. The detection limit for the passive sampler is 1 μg NO₂/m³ (7 days), the precision is 5% and the accuracy is estimated to 20%. The active iodide method agrees very well with the NO/NO_x-monitor. Compared on 24 h basis for a period of 3 months, covering a concentration range of 5–45 μg NO₂/m³, the deviation between the two methods is within 5%, and the absorption capacity of the iodide reagent is excellent as the breakthrough is below 1%.     

Comparison of passive and active sampling methods for the determination of nitrogen dioxide in urban air

Three different methods for sampling and determination of nitrogen dioxide in urban air are compared: an NO/NO_x-monitor and an active (pumped) and a passive sampling method. For the latter two methods, sodium iodide is used as absorbent. For weekly averages the results from the passive sampler are within 10–20% of the results for the two other methods in the concentration range 15–30 μg NO₂/m³. The detection limit for the passive sampler is 1 μg NO₂/m³ (7 days), the precision is 5% and the accuracy is estimated to 20%. The active iodide method agrees very well with the NO/NO_x-monitor. Compared on 24 h basis for a period of 3 months, covering a concentration range of 5–45 μg NO₂/m³, the deviation between the two methods is within 5%, and the absorption capacity of the iodide reagent is excellent as the breakthrough is below 1%. Received: 3 December 1996 / Revised: 11 March 1997 / Accepted: 15 March 1997     

Comparison of three methods for trace analysis of polycyclics

Summary Several analytical techniques for the determination of polycyclic aromatic hydrocarbons in air have been evaluated. Two solvents, benzene and cyclohexane, were compared for their efficacy in the preliminary preparation of the air sample. To identify and measure the polycyclics, the techniques of ultraviolet absorption and fluorescence were used. Air sample extracts were analyzed with and without prior Chromatographic separation. A rapid Chromatographic procedure using benzene as elutant was employed for the first time. The extract aliquot or eluate fraction was chromatographed on fully activated alumina using benzene as the eluting solvent. BaP and BkF are eluted from such a column in 30 minutes or less in a total eluate volume of perhaps 50 ml and the two hydrocarbons are determined by fluorescence emission. Work in progress suggests that benzene may be replaced in this application by the less toxic toluene.By any method used the BkF values found were in good agreement. The agreement between the various BaP values was poor, suggesting not all were of equal validity. The highest, and also least accurate, BaP values seem to be associated with the use of benzene as extractant, or ultraviolet absorption as a measuring technique.

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Zusammenfassung Verschiedene Analysenverfahren zur Bestimmung polycyklischer aromatischer Kohlenwasserstoffe in Luft wurden ausgearbeitet. Benzol und Cyklohexan wurden hinsichtlich ihrer Wirksamkeit als Lösungsmittel bei der Vorbereitung der Luftproben verglichen. Zur Identifizierung und Messung der polycyklischen Substanzen wurde die UV-Absorption und die Fluoreszenz herangezogen. Die Luftprobenextrakte wurden mit und ohne vorherige chromatographische Auftrennung analysiert. Bin rasches chromatographisches Verfahren mit Benzol als Elutionsmittel wurde erstmals verwendet. Extraktanteil oder Eluatfraktion wurden auf hochaktivem Aluminiumoxid chromatographiert und mit Benzol eluiert. Benzo(a)perylen (BaP) und Benzo(k)fluoranthen (BkF) werden aus einer solchen Säule in 30 Minuten mit etwa 50 ml eluiert und durch Fluoreszenzmessung bestimmt. Es scheint naheliegend, statt Benzol das weniger toxische Toluol zur Elution zu verwenden. Die nach jeder Methode erhaltenen BkF-Werte stimmen gut überein im Gegensatz zu den BaP-Werten. Die höchsten und gleichzeitig wenigst genauen BaP-Werte treten offenbar auf, wenn Benzol als Extraktionsmittel und UV-Absorption zur Messung verwendet werden.

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Presented at the Anachem Conference, Detroit, Mich., U. S. A., October 11, 1966.     

Evaluation of the fundamental sampling error in the sampling of particulate solids

Chemical analysis is a multi-stage process, which starts with primary sampling and ends with evaluation of the resuts. Especially in trace analysis and microanalysis of solid materials, sampling can far outweigh all other sources of error. For estimating the reliability of complete analytical procedures, a method is needed which can be used to estimate the errors made in the primary and the secondary sampling and sample preparation steps. Based on Gy's theory of sampling, a computer program (SAMPEX) was written for the solution of practical sampling problems. The method involves the estimation of the sampling constant, C. For well-characterized materials, C can be estimated from the material properties. If the necessary material properties are difficult to estimate, C can be evaluated experimentally. The program can be used to solve the following problems: minimum sample size for a tolerated relative standard deviation of the fundamental sampling error; relative size for a tolerated for a given sample size; maximum particle size of the material for a specified standard deviation and sample size; balanced design of a multi-stage sampling and sample-reduction process; and sampling for particle size determination.     

Comparison of quantitative methods for analysis of polyphasic pharmaceuticals

Adequate very sensitive quantification methods are needed for the development and are also now required for the monitoring of undesirable solid form(s) as routine tests. The pre-requisite for quantitation are selectivity, sensitivity and most important the purity of standards and their proper storage, what is a challenge for metastable forms. Several analytical techniques are available such as X-ray diffraction, spectroscopy, thermal analysis and microcalorimetry. The different steps of the validation of the analytical methods and problems to be solved are discussed. Examples illustrate the different techniques and compare their possible advantages and limits. The relative standard deviation of measurements should allow for checking the homogenization procedure of mixtures for calibration. The validation should be carried out following ICH guidelines for validation of analytical methods. Comparison of different techniques in adequate concentration range add confidence in the analytical results.     

Comparison of extraction methods for sampling of low molecular compounds in polymers degraded during recycling

The demand for mechanical recycling of plastic waste results in an increasing amount of recycled polymeric materials available for development of new products. In order for recycled materials to find their way into the material market, high quality is demanded. Thereby, a complete and closed loop of polymeric materials can be achieved successfully. The concept of high quality for recycled plastics imply that besides a pure fraction of e.g. polyethylene (PE) or polypropylene (PP), containing only minor trace amount of foreign plastics, knowledge is required about the type and amount of low molecular weight (LMW) compounds. During long-term use (service-life), products made of polymeric materials will undergo an often very slow degradation where a series of degradation products are formed, in parallel, additives incorporated in the matrix may also degrade. These compounds migrate at various rates to the surrounding environment. The release rate of LMW products from plastics depends on the initiation time of degradation and the degradation mechanisms. For polymers the formation of degradation products may be initiated already during processing, and subsequent use will add products coming from the surrounding environment, e.g. fragrance and aroma compounds from packaging. During recycling of plastics, emissions which contain a series of different LMW compounds may reach the environment leading to unwanted exposure to additives and their degradation residues as well as degradation products of polymers.Several extraction techniques are available for sampling of LMW compounds in polymers before chromatographic analysis. This paper reviews and compares polymer dissolution, accelerated solvent extraction (ASE), microwave assisted extraction (MAE), ultrasound assisted extraction (UAE), super critical fluid extraction (SFE), soxhlet extraction, head-space extraction (HS), head-space solid phase micro extraction (HS-SPME), and head-space stir bar sorptive extraction (HSSE) as appropriate sampling methods for LMW compounds in recycled polymers. Appropriate internal standards useful for these kinds of matrices were selected, which improved the possibility for later quantification. Based on the review of extraction methods, the most promising techniques were tested with industrially recycled samples of HDPE and PP and virgin HDPE and PP for method comparison.     

Determination of total particulate mercury in air with the coleman mercury analyzer system

A simple and rapid cold-vapour atomic absorption system is described for the simultaneous determination of low ambient levels of particulate mercury and volatile mercury compounds. Of the different filters checked for particle collection, quartz fibre filters have the best properties. Sampling characteristics were considered with respect to efficiency, reproducibility and duration of sampling. The homogeneity of the solid mercury deposit on the filter was tested. Possible enrichment during sampling by absorption of volatile mercury compounds and possible mercury losses by volatilization of solid compounds were examined. After sampling the mercury is released by pyrolysis and collected on a gold-coated sand absorber. In order to avoid deactivation of the absorber by condensation of pyrolysis products or interference during the subsequent dcsorption and atomic absorption measurement of the collected mercury, a heated catalytic convertor and two specific absorbers for organic substances are inserted in the analysis line.