Multielement analysis of environmental samples by total-reflection X-ray fluorescence spectrometry, neutron activation analysis and inductively coupled plasma optical emission spectroscopy

Summary In environmental research and protection trace elements have to be determined over a wide range of atomic number, down to very low concentrations, and in quite different matrices. This challenge requires the availability of complementary analytical methods characterized by a high detection power and few sources of systematic errors. Besides, the capacity of multielement detection is often desired since it facilitates the tackling of many problems in which numerous trace elements are of direct concern. Total reflection X-ray fluorescence, neutron activation analysis and inductively coupled plasma optical emission spectroscopy, in principle, fulfill these requirements quite well. However, each method has its domain, and the application to certain sample species may be less promising. Under this aspect, the paper summarizes some recent developments and investigations, including intercomparisons as far as possible. Various matrices are considered: rainwater and airborne particulates, soil samples, river sediments and suspended particulate matter, river water filtrates, ovean water, and organic matrices. Capabilities and limitations are discussed. Sample preparation techniques are described if they are new or essential for achieving the results given.

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Multielementanalyse von Umweltproben mit Totalreflexions-Röntgenfluorescenzspektrometrie, Neutronenaktivierungsanalyse und ICP-Emissionsspektroskopie

Zusammenfassung Umweltforschung und Umweltschutz erfordern die Bestimmung von Spurenelementen über einen weiten Bereich der Ordnungszahl, z. T. bis in den extremen Spurenbereich und in ganz unterschiedlichen Matrices. Die Erfüllung dieser Aufgabe setzt die Verfügbarkeit einander ergänzender analytischer Verfahren voraus, die durch eine hohe Nachweisstärke und geringe systematische Fehler gekennzeichnet sein müssen. Hinzu kommt, daß vielfach Multielement-Eigenschaften wünschenswert sind, da bei manchen Fragestellungen zahlreiche Elemente von Interesse sind. Die Totalreflexions-Röntgenfluorescenzanalyse, die Neutronenaktivierungsanalyse und die optische Emissionsspektroskopie mit induktiv angeregter Plasmafackel erfüllen grundsätzlich diese Forderungen in hohem Maße. Jedoch besitzt jede Methode ihre besonderen Stärken, und Anwendungen auf bestimmte Probenarten können weniger erfolgreich sein. Der vorliegende Beitrag faßt unter diesem Aspekt einige neuere Entwicklungen und Untersuchungen zusammen, wobei nach Möglichkeit Vergleiche der verschiedenen Verfahren angestellt werden. Dabei werden die folgenden Matrices behandelt: Niederschlag und luftgetragene Partikel, Bodenproben, Flußsedimente und Schwebstoffe, Flußwasserfiltrate, Ozeanwasser und einige organische Matrices. Die Einsatzmöglichkeiten und die Leistungsgrenzen werden diskutiert. Die Probenvorbereitungstechniken werden beschrieben, sofern sie neu sind oder eine wesentliche Voraussetzung für die Erzielung der angegebenen Ergebnisse darstellen.

     

Selenium speciation analysis using inductively coupled plasma-mass spectrometry

Selenium exists in several oxidation states and a variety of inorganic and organic compounds, and the chemistry of selenium is complex in both the environment and living systems. Selenium is an essential element at trace levels and toxic at greater levels. Interest in speciation analysis for selenium has grown rapidly in this last decade, especially in the use of chromatographic separation coupled with inductively coupled plasma-mass spectrometry (ICP-MS). Complete characterization of selenium compounds is necessary to understand selenium's significance in metabolic processes, clinical chemistry, biology, toxicology, nutrition and the environment. This review describes some of the essential background of selenium, and more importantly, some of the currently used separation methodologies, both chromatographic and electrophoretic, with emphasis on applications of selenium speciation analysis using ICP-MS detection.     

Uranium colloid analysis by single particle inductively coupled plasma-mass spectrometry

Uranium single particle analysis has been performed by inductively coupled plasma-mass spectrometry (ICP-MS) and the performances are compared with that provided by scanning electron microsopy and single particle counting. The transient signal induced by the flash of ions due to the ionisation of an uranium colloidal particle in the plasma torch can be detected and measured for selected uranium ion masses (²³⁸U⁺, ²³⁵U⁺ or ²⁵⁴[²³⁸U¹⁶O]⁺) by the mass spectrometer. The signals recorded via time scanning are analysed as a function of particle size or fraction of the studied element or isotope in the colloid phase. The frequency of the flashes is directly proportional to the concentration of particles in the colloidal suspension. The feasibility tests were performed on uranium dioxide particles. The study also describes the experimental conditions and the choice of mass to detect uranium colloids in a single particle analysis mode.     

Thorium colloid analysis by single particle inductively coupled plasma-mass spectrometry

Thorium colloid analysis in water has been carried out by a single particle mode using inductively coupled plasma mass spectrometry (ICP-MS). The flash of ions due to the ionisation of a thorium colloidal particle in the plasma torch can be detected and measured in a time scan for ²³²Th⁺ or ²⁴⁸[ThO]⁺ according to the sensitivity required by the mass spectrometer. The peaks of the recorded intensity of the MS signal can be analysed as a function of the particle size or fraction of the studied element in the colloid phase. The frequency of the flashes is directly proportional to the concentration of particles in the colloidal suspension. After discussing Th colloid detection, on the basis of the intensity of the ion flashes generated in the plasma torch, tests were performed on thorium dioxide colloidal particles. This feasibility study also describes the experimental conditions and the limitation of the plasma design to detect thorium colloids in a single particle analysis mode down to about 10 fg.     

Certification of total arsenic in blood and urine standard reference materials by radiochemical neutron activation analysis and inductively coupled plasma-mass spectrometry

Radiochemical neutron activation analysis (RNAA) was used to measure arsenic at four levels in standard reference material (SRM) 955c Toxic Elements in Caprine Blood and at two levels in SRM 2668 Toxic Elements in Frozen Human Urine for the purpose of providing mass concentration values for certification. Samples were freeze-dried prior to analysis followed by neutron irradiation for 3 h at a fluence rate of 1 × 10¹⁴ cm^?2 s^?1. After sample dissolution in perchloric and nitric acids, arsenic was separated from the matrix either by retention on hydrated manganese dioxide (urine) or by extraction into zinc diethyldithiocarbamate in chloroform (blood). ⁷⁶As was quantified by gamma-ray spectroscopy. Differences in chemical yield and counting geometry between samples and standards were monitored by measuring the count rate of a ⁷⁷As tracer added before sample dissolution. RNAA results were combined with inductively coupled plasma-mass spectrometry values from National Institute of Standards and Technology and collaborating laboratories to provide certified values of 10.81 ± 0.54 and 213.1 ± 0.73 μg/L for SRM 2668 Levels I and II, and certified values of 21.66 ± 0.73, 52.7 ± 1.1, and 78.8 ± 4.9 μg/L for SRM 955c Levels II–IV, respectively. Because of discrepancies between values obtained by different methods for SRM 955c Level I, an information value of <5 μg/L was assigned for this material.     

Comparison of a portable micro-X-ray fluorescence spectrometry with inductively coupled plasma atomic emission spectrometry for the ancient ceramics analysis

Two multielement instrumental methods of analysis, micro X-ray fluorescence spectrometry (micro-XRF) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were applied for the analysis of 7th and 5th century B.C. ancient ceramic sherds in order to evaluate the above two methods and to assess the potential to use the current compact and portable micro-XRF instrument for the in situ analysis of ancient ceramics. The distinguishing factor of interest is that micro-XRF spectrometry offers the possibility of a nondestructive analysis, an aspect of primary importance in the compositional analysis of cultural objects. Micro-XRF measurements were performed firstly directly on the ceramic sherds with no special pretreatment apart from surface cleaning (micro-XRF on sherds) and secondly on pressed pellet disks which were prepared for each ceramic sherd (micro-XRF on pellet). For the ICP-AES determination of elements, test solutions were prepared by the application of a microwave-assisted decomposition procedure in closed high-pressure PFA vessels. Also, the standard reference material SARM 69 was used for the efficiency calibration of the micro-XRF instrument and was analysed by both methods. In order to verify the calibration, the standard reference materials NCS DC 73332 and SRM620 as well as the reference materials AWI-1 and PRI-1 were analysed by micro-XRF. Elemental concentrations determined by the three analytical procedures (ICP-AES, micro-XRF on sherds and micro-XRF on pellets) were statistically treated by correlation analysis and Student's t-test (at the 95% confidence level).     

Multielemental analysis of food and agricultural matrixes by inductively coupled plasma-mass spectrometry

The suitability of quadrupole inductively coupled plasma-mass spectrometry (ICP-MS) for multielemental analysis of food following microwave closed vessel digestion of samples was evaluated in relation to analytical challenges presented by some major food and agricultural matrixes. Fifteen key analytes (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, Sn, V, Zn) were determined in 9 reference materials representative of 3 major groups of staple foods (cereals, seafood, and meat). For all measurements, the method of external calibration was used and Rh was selected as internal standard. Matrix-induced interferences were evaluated for each material, and suitable methods to overcome them were applied. Spectral interferences caused by C, Cl, and Ca content of digestates were quantitated and corrected by entering a simple system of mathematical correction equations into the instrument software before each analytical run. Full mastering of interferences together with adoption of a series of measures to control the reliability of analytical measurements produced accurate results for all the analytes. A standard analytical protocol is outlined for the benefit of both research and routine high-throughput laboratories that perform ICP-MS analyses of food.     

Application of instrumental neutron activation analysis and inductively coupled plasma-mass spectrometry to studying the river pollution in the State of Minas Gerais

Instrumental neutron activation analysis (INAA) and inductively coupled plasma-mass spectrometry (ICP-MS) have been used for the determination of toxic heavy metals and other pollutants in the water of the Das Velhas river in the State of Minas Gerais, in south-east Brazil. Elemental concentrations of about 60 elements were measured in water samples collected to different parts of this river and from two affluents. There was a good agreement between the two analytical methods and the results were complementary. The results indicated an increase in the concentration of several polluting elements in the water from mining industry area.     

Instrumental neutron activation analysis and inductively coupled plasma mass spectrometry on atmospheric biomonitors

Sensitivities for detecting fluorine, distributed uniformly in elements with atomic numbers 8, 13, 20, 28, 34, 42, 50, 60, 68 and 79, through the F(p,αγ)O reaction, have been calculated using experimentally measured excitation functions and the available energy-range data. Thick target yields of the prompt 6.13 MeV gammas, as well as of the three gamma-lines of 6.13, 6.92 and 7.12 MeV combined, have been plotted as a function of the incident energy of up to 4.16 MeV. From these yield curves the sensitivity of detecting fluorine in thick or thin samples, and even in a layer of known thickness at a particular depth within a thick target, can be directly read for known bombarding and detecting conditions. The curves should also be valid, to a certain approximation, for neighbouring elements and for mixtures or compounds with similar average atomic numbers. Furthermore, it is explained as to how these yield curves can also be used in non-destructive profile analysis of fluorine to much greater depths than can be achieved by the well-known resonance-shift method.     

Neutron activation analysis and inductively coupled plasma-mass spectrometry for the determination of elements in tree stems

Mn, Zn and Al concentrations of ume, sakura and sugi stems determined by ICP-MS using a simple pretreatment were compared with those determined by INAA. We obtained a considerably good agreement between the two methods. ICP-MS using simple pretreatment was found to be useful in analyzing the elements in tree stems.     

Practical aspects of routine trace element environmental analysis by inductively coupled plasma-mass spectrometry

Since the appearance, in the early eighties, of first publications describing plasma source mass spectrometry as a viable analytical technique, there has been a rapid increase in the number of papers detailing its possible applications, instrumental developments and fundamental studies. In the laboratories involved in the environmental or food monitoring problematics, inductively coupled plasma-mass spectrometry (ICP-MS) systems are usually acquired in order to analyze large series of samples. At our knowledge, very rare are works dedicated to the sum of factors and additional problems usually encountered in the routine analysis using this analytical technique. In this work, we will try to fill in these gaps by discussing the main factors that may strongly influence the analysis of large series of samples. Firstly, there are uncertainties associated to the choice of measurement parameters: calibration blanks, curve algorithms and their long-term validity, selection of internal standards, recalibration blocks and usefulness of correction equations. Secondly, we will discuss analytical parameters that concern samples themselves: their appropriate dilution and acidification as well as the knowledge of matrix effects possibly produced. Finally, there is also a very important point concerning appropriate definition of the procedure blank as well as its utilization. Only the careful consideration of all these aspects permits to obtain accurate results during routine analysis. Aim of this work is not oriented to discussion of typical and well-documented ICP-MS individual problems but rather to means that allow to overcome main uncertainties resulting in an improvement of the whole routine analysis.     

Gold colloid analysis by inductively coupled plasma-mass spectrometry in a single particle mode

Analysis in a single particle mode of gold colloids in water has been performed by inductively coupled plasma-mass spectrometry (ICP-MS). The signal induced by the flash of ions due to the ionization of a colloid in the plasma torch can be measured for the ions ¹⁹⁷Au⁺ by the mass spectrometer without interferences. The intensity of the MS signal is recorded in time scan. The recorded peak distributions were analysed as a function of the colloid size for five monodisperse colloids (80-250 nm). This study describes the experimental conditions to analyse gold colloids in a single particle mode. The size detection limit is around 25 nm corresponding to 0.15 fg colloids and one particle per ml may be detected during a 1 min time scan within standard procedure.     

电感耦合等离子体质谱法测定地球化学样品中镉

采用HF-HClO4-HNO3-H2SO4分解样品,王水提取,选用4个国家一级标准物质制备成标准系列校准,ICP-MS法直接测定地球化学样品中的Cd。选择103Rh为内标,确定了仪器的最佳分析条件,研究了Zr,Sn对Cd的干扰,选择114Cd作为测定同位素,采用数学公式校正了Sn对Cd的同质异位素干扰,方法检测限(3s)为6.3×10-3μg/g,RSD(n=12)为3.9%～6.6%。经国家一级标准物质验证,测定值与标准值吻合较好。该方法适用于地球化学样品中的微量Cd的测定。     

On-line coupling of gel electrophoresis and inductively coupled plasma-mass spectrometry

The on-line coupling of gel electrophoresis with inductively coupled plasma-mass spectrometry (GE-ICP-MS) is a powerful tool for simultaneous separation, detection and quantification of bio-molecules, and has been applied to the determination of phosphorus in DNA, phosphoproteins, and phosphopeptides, gold in nano-particles, iron in metalloproteins, and iodine in aerosols, and cisplatin-oligonucleotide interactions. However, since the first report in 2005, relatively few papers have been published, perhaps reflecting the lack of familiarity with the benefits of this promising methodology. So, here for the first time, we critically review the applications of GE-ICP-MS, and explore the advantages and the limitations of the technique for various applications. Such scrutiny may be useful in not only the development of the technique but also highlighting its potential in proteomics, genomics and metallomics.     

Effects of sampler-skimmer separation in inductively coupled plasma-mass spectrometry

The effects of varying the sampler-skimmer spacing in an inductively coupled plasma-mass spectrometer are illustrated. The signals for a number of species were monitored including background ions (ArN⁺, ArO⁺, ArOH⁺, Ar₂⁺, Ar₂H⁺), background continuum, analyte ions (Cu⁺, Ce⁺, La⁺), analyte oxide ions (CeO⁺, LaO⁺), and matrix induced ions (ArNa⁺). As the sampler-skimmer spacing is increased over that normally used, the signal for some species decreases in intensity while the signal for others increases in intensity. There is a wide range of differential behavior and in some cases the signal changes are quite dramatic.

In addition to presenting results for an Ar plasma, measurements are also presented for a N₂-Ar mixed gas plasma. For some species, the signal changes observed when the sampler-skimmer spacing is increased are quite different with the N₂-Ar mixed gas plasma than with the Ar plasma and are, in some cases, opposite to signal changes observed with the Ar plasma. It appears that a larger sampler-skimmer spacing is more appropriate for a N₂ mixed gas plasma than the spacing normally used for a pure Ar plasma. Finally the effect of sampler-skimmer spacing on matrix effects is presented and it appears that matrix effects are not induced in the zone between the sampler and the skimmer.     

Monitoring of elements in mosses by instrumental neutron activation analysis and total X-ray fluorescence spectrometry

Journal of Radioanalytical and Nuclear Chemistry - This research presents a study of environmental monitoring at different sampling sites from the Metropolitan Area of the Valley of Toluca (MAVT)...     

Characterization and differentiation of iron ores using X-ray diffractometry,k0 instrumental neutron activation analysis and inductively coupled plasma optical emission spectrometry

This study was aimed at developing methodology for the characterization and differentiation of iron ores from different ore deposits. X-ray diffractometry (XRD) was used for the determination of major and minor chemical phases in the ores, k₀-instrumental neutron activation analysis (k₀-INAA) and inductively coupled plasma optical emission spectrometry (ICP-OES) were employed for the determination of elemental profiles of iron ores. The quality of the ores was evaluated to establish their suitability to serve as a raw material for iron production. Principal component analysis was performed on the elemental data for the classification of ores. It was also shown that ores can be differentiated on the basis of rare earth elemental profiles. In this paper a new indicator, based on four elements (Ca, S, Sb, Yb), was proposed for the classification.

     

Reactor neutron activation analysis followed by characteristic X-ray spectrometry

The possibility of applications of characteristic X-rays from radioactive products of reactor neutron activation was investigated with particular emphasis on (n, ), n, n), (n, 2n), (n, p) and (n, ) products with long half-lives. The sensitivity and detection limits of silver, cerium, gadolinium, selenium, cadmium and europium have been investigated. The elements were studied both in a pure and in a matrix form, in both cases the samples were diluted with graphite (90%) to minimize matrix effects (absorption and enhancement).     

Determination of metals in composite diet samples by inductively coupled plasma-mass spectrometry

A study was conducted to evaluate the applicability of inductively coupled plasma-mass spectrometry (ICP-MS) techniques for determination of metals in composite diets. Aluminum, cadmium, chromium, copper, lead, manganese, nickel, vanadium, and zinc were determined by this method. Atmospheric pressure microwave digestion was used to solubilize analytes in homogenized composite diet samples, and this procedure was followed by ICP-MS analysis. Recovery of certified elements from standard reference materials ranged from 92 to 119% with relative standard deviations (RSDs) of 0.4-1.9%. Recovery of elements from fortified composite diet samples ranged from 75 to 129% with RSDs of 0-11.3%. Limits of detection ranged from 1 to 1700 ng/g; high values were due to significant amounts of certain elements naturally present in composite diets. Results of this study demonstrate that low-resolution quadrupole-based ICP-MS provides precise and accurate measurements of the elements tested in composite diet samples.     

Automatic selection of internal standards in inductively coupled plasma-mass spectrometry

The automatic selection of internal standards in inductively coupled plasma-mass spectrometry was performed using a cluster analysis algorithm. The samples contained 25 analytes, spanning the atomic mass and ionization potential ranges, and a single interfering element. The interferents examined were Na, Mg, K, Zn, Ba, and Pb. The cluster analysis algorithm used kinetic energy, ionization potential, oxide bond strength, hydride bond strength, and electronegativity, to group the analytes. These variables were weighted differently in the various matrices. The performance of the clustering method and selection of internal standards was good for most analytes in the various matrices.