Inductively coupled plasma-atomic emission spectrometric determination of rare earth elements in geological materials

Inductively coupled plasma-atomic emission spectrometry (ICP-AES) has been applied to the determination of the rare earth elements (REE) lanthanum to lutetium (except terbium) in a range of geological materials. Group separation of the REE is carried out by sintering the sample with sodium peroxide to remove the bulk of the matrix, followed by fluoride precipitation with an yttrium carrier. This minimizes spectral interferences and provides sensitivities that are adequate for concentration levels around crustal abundances. The precision (2σ) is 3–5% for most of the elements and about 10% for some of the less abundant elements with concentrations that approach the limit of determination. Comparison of results obtained on a range of reference samples with literature values demonstrates the suitability of the procedures to provide rare earth abundance data for geochemical investigations.     

Inductively coupled plasma-atomic emission spectroscopy: Its present and future position in analytical chemistry

Summary This review (with 179 references) is mainly intended to facilitate judgements about the present and future position of inductively coupled plasma-atomic emission spectrometry (ICP-AES) among both various established spectroscopic methods and AES methods based on novel plasma sources for liquid analysis. It is considered that a thorough and critical comparison of the capabilities and cost of ICP-AES with those of the existing outfit of a laboratory must be made in each individual situation separately to judge whether ICP-AES as a supplement to or a replacement of one or more established techniques is an economic proposition. From this point of view ICP-AES is reviewed as a relatively new method for the analysis of liquids and dissolved solids.The principle of the method and the basic instrumentation are briefly outlined. The distinction between low-power argon ICPs and high-power nitrogen-argon ICPs is pointed out and the viability of both approaches in the analysis of real samples is noted. Analytical performance is discussed in terms of detection limits, precision, accuracy and dynamic range. Applications of real-sample analysis are given as illustrative examples.A list is included of the best detection limits of 67 elements in aqueous solutions as reported for argon ICPs operated with pneumatic and ultrasonic nebulizers. Detection limits of 15 elements in oil are given to illustrate the potentials of low-power argon ICPs in the field of organic liquid analysis. The detection limits of As, Sb, Bi, Se and Te as achieved by combining hydride generation with an argon ICP, are presented to demonstrate recent progress in the determination of elements for which the detection power was hitherto less satisfactory than desired.With regard to precision, the behaviour of ICPs is pointed out as fluctuation-nose limited systems that are dominated by a relative standard deviation (RSD) of 1 % in both background and net signals as generated in the source. The dependence of the RSD in the eventually measured net signals (gross signal minus background signal) on the ratio of concentration to detection limit is discussed.An extensive discussion of accuracy incorporates detailed reference to factors such as spectral interferences and reagent impurities, nebulization and transport interferences, solute vaporization interferences, and ionization interferences, which may affect the accuracy attained in ICP-AES. It is shown that ICP-AES is relatively free from interferences so that a fair degree of accuracy can be reached, if proper precautions are taken, which, in comparison with AES methods using other excitation sources, or AAS, are not excessive. It is added, however, that the measures needed to ensure fair accuracy will become increasingly severe as the analyte concentration approaches the detection limit more closely or the composition of the sample becomes more complex. It is noted that under these conditions the problems that arc spectroscopists had to face in trace analysis using dc arc spectrography are again encountered, in particular as regards the correct isolation of a net line signal from a background spectrum whose structure depends on the sample composition.The advantages of the large linear dynamic range of three to five orders of magnitude are mentioned.The numerous applications of ICP-AES reported in literature are illustrated with a list of classes of materials for which analyses were described recently.Spectrometers enter into the discussion as indispensable parts of ICP equipment that are necessary for complete analytical instruments and the price of which may be a multiple of that of the ICP source itself. Alternative spectrometers for ICP-AES are grouped into three categories depending on the type of analysis problem: 1) general survey analysis, 2) routine multielement analysis and non-routine multielement analysis with limited flexibility, and 3) flexible single-element analysis.This classification, which fits in with general cost and performance considerations, is used as a convenient basis in the subsequent assessment of the position of ICP-AES among established spectroscopic methods. This assessment encompasses comparisons of the capabilities of ICP-AES, flame AES, flame and furnace atomic absorption spectrometry (AAS), de arc AES, spark AES, and X-ray fluorescence spectrometry (XRFS).The position of ICPs with respect to alternative novel plasma sources for liquid analysis by AES is discussed in the light of the historic development. This eventually led to the present situation in which there are at least twelve manufacturers of spectroscopic equipment that are marketing ICP apparatus and one marketing a dc plasma source for liquid analysis, while a renewed commercialization of a capacitively coupled microwave plasma (CMP) is stimulating new interests in CMPs. As to microwave-induced plasmas (MIP), attention is drawn in particular to the TM₀₁₀ cavity that permits the generation of atmospheric pressure plasmas in helium. These have excellent characteristics as element-selective detectors in gas chromatography and also have many potential applications in multielement and single-element analysis in general, especially for the analysis of microsamples, if these are separately evaporated and atomized, e.g. by electrothermal means, prior to their introduction into the MIP.

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ICP-AES: Gegenwärtige und zukünftige Stellung in der Analytischen Chemie

Zusammenfassung Diese Übersicht (mit 179 Literaturzitaten) beabsichtigt hauptsächlich, die gegenwärtige und zukünftige Stellung der atomaren Emissions-Spektrometrie unter Verwendung eines induktiv gekoppelten Hochfrequenz-Plasmas (ICP-AES) sowohl unter den verschiedenen herkömmlichen, »bewährten« spektroskopischen Methoden als auch unter den AES-Methoden mit neuen Plasmaquellen für Flüssigkeitsanalysen zu verdeutlichen. Nach gründlichem und kritischem Vergleich der Leistungsfähigkeit und Kosten der ICP-AES gegenüber schon bestehenden Laboreinrichtungen muß die Wirtschaftlichkeit der ICP-AES je nach Situation als mögliche Ergänzung oder als möglicher Ersatz zu den herkömmlichen Techniken bewertet werden. Im Hinblick darauf wird die ICP-AES als eine relativ neue Methode zur Analyse von Flüssigkeiten und gelösten Feststoffen untersucht.Das Prinzip der Methode und die Grundausrüstung werden kurz erklärt. Dabei wird auf den Unterschied eines Argon-ICPs niedriger Leistung gegenüber einem Stickstoff-Argon-ICP hoher Leistung hingewiesen und die Fähigkeit dieser beiden Arten für Analysen realer Proben besprochen. Die Analysenfähigkeit im allgemeinen wird anhand von Nachweisgrenzen, Genauigkeit, Richtigkeit und dynamischem Bereich diskutiert. Typische Anwendungsbeispiele werden erwähnt.Eine Zusammenstellung der besten Nachweisgrenzen von 67 Elementen in wäßrigen Lösungen wird für Argon-ICPs mit pneumatisch und mit Ultraschall betriebenem Zerstäuber gegeben. Nachweisgrenzen von 15 Elementen in Öl werden angeführt, um die Anwendungsmöglichkeiten von Argon-ICPs niedriger Leistung auch im Bereich der organischen Flüssigkeitsanalysen zu zeigen. Die Nachweisgrenzen von As, Sb, Bi, Se und Te, die durch eine Kombination von Hydridbildung und Argon-ICP erreichbar sind, werden dargestellt, um den neuesten Fortschritt in der Elementbestimmung zu zeigen, wo bisher das Nachweisvermögen noch nicht ausreichend war.Bei der Behandlung der Genauigkeit wird auf die Eigenschaft des ICPs als ein durch Schwankungsrauschen in der Lichtquelle begrenztes System hingewiesen, was durch die relative Standardabweichung (RSD) von 1 %, sowohl in den Untergrund- als auch Nettosignalen, wie sie die Quelle selbst bewirkt, deutlich wird. Die Abhängigkeit der RSD in den schließlich gemessenen Nettosignalen (Bruttosignal minus Untergrundsignal) vom Verhältnis Konzentration zu Nachweisgrenzen wird diskutiert.Eine ausführliche Besprechung der Richtigkeit umfaßt detaillierte Angaben über Faktoren wie spektrale Interferenzen, Reagensunreinheiten, Zerstäubungsund Transportinterferenzen, Verdampfungsinterferenzen und schließlich Ionisationsinterferenzen, die alle für die erreichte Richtigkeit ausschlaggebend sein dürften. Es wird gezeigt, daß die ICP-AES relativ frei von Interferenzen ist, so daß gute Richtigkeit in beträchtlichem Maß erreicht werden kann, wenn geeignete Vorsichtsmaßnahmen getroffen werden, die weniger aufwendig als diejenigen anderer AES-Methoden oder der AAS sind. Es wird jedoch ausgeführt, daß die zur Erzielung guter Richtigkeit erforderlichen Maßnahmen, immer aufwendiger werden, sobald die Analysenkonzentration sich mehr und mehr der Nachweisgrenze nähert oder die Proben komplexer werden. Dazu ist zu sagen, daß hier wieder die gleichen Probleme auftauchen, mit denen sich die Bogenspektroskopiker bei der Anwendung des Gleichstrombogens in der Spurenanalyse zu befassen hatten, besonders hinsichtlich der korrekten Abtrennung eines Nettosignals vom Untergrundspektrum, dessen Struktur von der Probenzusammensetzung abhängt.Der Vorteil des großen linearen dynamischen Bereichs über drei bis fünf Größenordnungen wird erwähnt.Die zahlreichen Anwendungen der ICP-AES werden in einer Liste nach denjenigen Matrialklassen aufgeführt, die in der neuesten Literatur beschrieben sind.Spektrometer werden als unentbehrlicher Teil einer ICP-Ausrüstung diskutiert, der zu einem vollständigen Analysengerät gehört und dessen Preis ein Vielfaches von dem der ICP-Quelle selbst betragen kann. Die unterschiedlichen Spektrometer für die ICP-AES werden in drei Gruppen eingeteilt, abhängig von der Art des Analysenproblems: 1. Allgemeine Übersichtsanalysen, 2. routinemäßige Multielementanalysen und nichtroutinemäßige Multielementanalysen mit beschränkter Flexibilität, und 3. flexible Einzelelementanalysen. Diese Klassifikation, angepaßt an die allgemeinen Kosten und Leistungsbetrachtungen, wird als nützliche Basis zur nachfolgenden Einschätzung der Stellung der ICPAES unter den herkömmlichen, »bewährten« spektroskopischen Methoden verwendet. Diese Einschätzung schließt Leistungsvergleiche zwischen ICP-AES, Flammen-AES, Flammen- und Ofenatomabsorptionsspektrometrie, Gleichstrombogen-AES, Funken-AES und Röntgenfluorescenzspektrometrie (XRFS) ein.Die Stellung des ICPs gegenüber anderen neuen Plasmaquellen für Flüssigkeitsanalysen durch AES wird im Hinblick auf die geschichtliche Entwicklung behandelt. Diese führte schließlich zu der heutigen Situation, wo mindestens 12 Hersteller von Spektrometerausrüstungen ICP-Geräte (einer mit einer Gleichstromplasmaquelle) anbieten, währenddem erneuter Handel mit einem kapazitiv gekoppelten Mikrowellenplasma (CMP) neue Interessen an CMPs weckt. Was Mikrowellen induzierte Plasmen (MIP) betrifft, wird die Aufmerksamkeit speziell auf den TM₀₁₀-Hohlraum gerichtet, der die Erzeugung von Helium-Plasmen bei atmosphärischem Druck ermöglicht. Diese MIPs haben ausgezeichnete Eigenschaften als element-selektive Detektoren in der Gas-Chromatographie und bieten auch viele Verwendungsmöglichkeiten bei allgemeinen Multielement- und Einzelelementanalysen, speziell für Mikroproben, wenn diese vor der Eingabe in das MIP getrennt verdampft und atomisiert werden (z.B. elektrothermisch).

     

Inductively coupled plasma-atomic emission spectrometry method for determination of trace metals in alkaline-earth matrices after flotation separation

An inductively coupled plasma-atomic emission spectrometry (ICP-AES) method is developed for determination of Cd, Co, Cr, Cu, Ni, Tl and Zn in traces in calcite, CaCO₃, dolomite, CaMg(CO₃)₂, and gypsum, CaSO₄. Interferences of a Ca/Mg matrix on analyte intensities were investigated. The results reveal that Ca does not interfere with Cr, Ni and Zn, but tends to decrease the intensity of the other elements. Magnesium as a matrix element does not interfere on with Zn, but increases the intensities of Ni, Cr and Cu, and decreases the intensities of Cd, Co and Tl. To eliminate these matrix interferences on trace element intensities, a flotation separation method is proposed. Lead(II) hexamethylenedithiocarbamate, Pb(HMDTC)₂, is applied as a collector for flotation of trace elements from acidic solutions of mineral samples. The flotation of acidic aqueous solutions of calcite, dolomite and gypsum was performed at pH 6.0, using 10 mg l⁻¹ Pb and 0.3 mmol l⁻¹ HMDTC⁻ added to 1 l of solution tested. The method detection limits of analytes in different minerals range from 0.02 to 0.06 μg g⁻¹ for Cd, 0.04 to 0.10 μg g⁻¹ for Co, 0.03 to 0.13 μg g⁻¹ for Cr, 0.02 to 0.16 μg g⁻¹ for Cu, 0.09 to 0.30 μg g⁻¹ for Ni, 6.45 to 7.71 μg g⁻¹ for Tl and 0.18 to 0.20 μg g⁻¹ for Zn.     

A novel bottom-viewed inductively coupled plasma-atomic emission spectrometry

A novel optical configuration for inductively coupled plasma (ICP)-atomic emission spectrometry is presented. Plasma emission is measured axially via the bottom end of the ICP torch. Analytical performance, such as increase in signal-to-background ratio (SBR) over radially viewed ICP and linear dynamic range, is comparable to that of end-on axially viewed ICP reported in the literatures. Under typical ICP operating conditions (forward power=1.0–1.6 kW, central channel gas flow rate=0.8–1.4 l/min), SBR is generally five times or more that of radial-viewing mode (observation heights=3–20 mm) for atomic lines of elements of low to medium ionization potential (Na, K, Sr and Ba). The enhancement factor in SBR is two to four times for ionic lines (e.g. MgII) and atomic lines of elements of high ionization potential (Zn). The influence of ICP forward power and carrier gas flow rate on analyte emission intensity and SBR were also studied. Similar to radially viewed ICP, as forward power increases, the net emission intensity increases and SBR decreases. Using a constant flux of analyte aerosols, the net intensity decreases as the central channel gas flow rate increases. No trend of SBR vs. central channel gas flow rate, however, is found. The linear dynamic range starts and ends at analyte concentration 0.5–1 order of magnitude lower than the corresponding radial-viewing mode. As a result, the span of linear dynamic range is similar for all viewing modes. Matrix effects of K and Ca on atomic lines are different from those reported for end-on axially viewed ICPs, probably due to the difference in the plasma regions that were probed. The matrix effects on ionic lines, however, are similar in magnitude.     

Neptunium estimation in the spent fuel dissolver solution by inductively coupled plasma-atomic emission spectroscopy

This paper deals with the optimization of experimental conditions for the estimation of Np in spent fuel dissolver solution using 2-thenoyltrifluoroacetone (HTTA) as extractant. The quantitative extraction of Np from the dissolver solution employing 0.5 M HTTA/xylene was followed by its estimation by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) after stripping it from the organic phase with 8 M HNO₃. The reliability of the method was checked by standard addition technique. The method is precise and accurate yielding Np analytical recovery of 99 ± 1%.     

Inductively coupled plasma-atomic emission spectrometry: Analytical assessment of the technique at the beginning of the 90's

The main application of the inductively coupled plasma (ICP) today is in atomic emission spectroscopy (AES), as an excitation spectrochemical source, although uses of an ICP for fluorescence as just an atomiser, and specially for mass spectrometry, as an ionization source, are rocketing in the last few years.Since its inception, only a quarter of a century ago, ICP-AES has rapidly evolved to one of the preferred routine analytical techniques for convenient determination of many elements with high speed, at low levels and in the most varied samples. Perhaps its comparatively high kinetic temperature (capable of atomising virtually every compound of any sample), its high excitation and ionisation temperatures, and its favourable spatial structure at the core of the ICP success.By now, the ICP-AES can be considered as having achieved maturity in that a huge amount of analytical problems can be tackled with this technique, while no major or fundamental changes have been adopted for several years. Despite this fact, important driving forces are still in operation to further improve the ICP-AES sensitivity, selectivity, precision, sample throughput, etc. Moreover, proposals to extend the scope of the technique to traditionally elusive fields (e.g. non-metals and organic compound analysis) are also appearing in the recent literature.In this paper the state of the art, the last developments and the expectations in trying to circumvent the limitations of the ICP-AES (on the light of literature data and personal experience) are reviewed.     

Speciation of magnesium in rat plasma using capillary electrophoresis-inductively coupled plasma-atomic emission spectrometry

A new method for speciation analysis of magnesium species and quantification of free magnesium concentrations in rat plasma was developed by on-line coupling of CE with inductively coupled plasma-atomic emission spectrometry (ICP-AES). Baseline separation of seven magnesium species was achieved by using a 120 cm (100 microm internal diameter) fused-silica capillary, a 20 kV separation voltage and a solution of 50 mmol/L NaAc-HAc (pH 5.5) as electrolyte buffer. CE-ICP-AES analysis of a rat plasma sample showed the presence of seven magnesium species, one of which was identified as free Mg2+ ion by spiking a Mg2+ standard; the migration time of the Mg2+ peak in the standard and the spiked sample matched with each other. One protein-bound magnesium species in rat plasma is associated with albumin, and the other three species are combined with globulin. The concentration of free magnesium in the plasma was 14.0 mg/L. The other six magnesium species were estimated to be 4-15 mg/L. RSDs of migration time and peak area for the magnesium species from ten replicates were less than 5%. The developed method was also applied to speciation analysis of magnesium species in spiked plasma samples. The recoveries of the free magnesium species in four samples ranged from 95.8 to 103.8%.     

Multielement analysis of gypsiferous soils using a sequential inductively coupled plasma-atomic emission spectrometric method

The amount of major, minor, and trace elements (Ca, Mg, Fe, Na, Sr, Mn, Cu, Cr, V, Mo, B, Ni, Li, and Ba) in gypsiferous soils formed by evaporitic processes was determined. A sequential analysis method by atomic emission spectroscopy with an inductively coupled plasma was used, working with partial matrix matching between the reference standards and the real samples. Furthermore, a simplified method, based on two calibration graphs (Fe and Li), was developed for calibrating the analysis procedure.     

Development and characterization of bottom-viewed inductively coupled plasma-atomic emission spectrometry

In bottom-viewed inductively coupled plasma-atomic emission spectrometry (BV-ICP-AES), emission from the central channel of the plasma is measured axially from the bottom of the plasma. A straight quartz tube was used as a hollow light pipe (HLP) to collect plasma emission in this study. The HLP also serves as an injector for aerosols transport and injection into the ICP. The optical characteristics of HLPs with the original reflective surface and roughened outer surface are reported. The roughened HLP is effective in rejecting light beams that are not in line with the HLP. The transmission efficiency of the HLP, however, is high (> 70%) for light beams from a source that has the same dimension as the entrance of the HLP and is flush with the HLP. The HLP is effective in rejecting background emission from the core of the plasma that encircles the plasma central channel and yet efficient in light collection from the central channel of the plasma.     

Miniature hydride generator system for inductively coupled plasma-atomic emission spectrometry

Conclusion The detachable miniature hydride generator presented in this work gives the analytical chemist easy access to the determination of ultratrace levels of tin and germanium using a 1.2 kW-ICP spectrometer commercially available. An improvement of the detection limits of approximately 100 times those for conventional pneumatic nebulizer-ICP-AES, has been reported in this work.     

Observations on the determination of oxygen in silver halides using inductively coupled plasma-atomic emission spectrometry

This paper reports on a novel method for the determination of oxygen in silver halides using inductively coupled plasma-atomic emission spectrometry (ICP-AES). A heating system was designed and set up to heat the sample and to release oxygen which was then sent into the plasma by the argon carrier gas. A demountable extended ICP torch was assembled to prevent air from entering the analytical region of the ICP. The nonresonance near infrared atomic oxygen line, O(I) 777.19 nm, was used for the determination of oxygen. The detection limit of the method was 1.6 μg of oxygen. Pure oxygen was used for calibration. The method had a precision of 4.74% RSD for about 15 μg of oxygen in samples.     

Qualities related to spectra acquisition in inductively coupled plasma-atomic emission spectrometry

As many elements emit line-rich spectra in ICP-AES, the role of the resolution of the dispersive system has been considered as crucial not only to minimize spectral interferences but also to improve signal-to-background ratios. Resolution is mainly based on the line width measured at half of the peak intensity. Because of the availability of modern gratings, the practical resolution is no longer limited by the diffraction patterns produced by the grating, but is mainly bandpass and optical aberration limited. High resolutions of 5 pm may be obtained in the UV, which has to be compared with the physical line widths in the range 1–6 pm. However, such a high resolution cannot be achieved in the visible region because it is no longer possible to use a high line number for conventional gratings and high diffraction orders for echelle gratings. Moreover, the resolution concept does not consider the line wings, which are of concern for background correction. It is then suggested a measurement of the line profile at 1% of the peak intensity and a comparison with that measured at 50%. Because of the current possibility to have acquisition of the entire, or at least large portions of the UV-visible spectra, wavelength reproducibility may become the most important parameter to facilitate data processing such as spectra addition and subtraction, filtering, deconvolution and line correlation.     

Studies on laser defocusing effects on laser ablation inductively coupled plasma-atomic emission spectrometry using emission signals from a laser-induced plasma

The effect of laser defocusing on analytical performance of laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) was studied by varying laser focus conditions with respect to the surface of a low-alloy steel and a powdered sediment pellet. Laser-induced plasma (LIP) and LA-ICP-AES emission signals and LIP excitation temperatures (LIP T_ex) were determined and compared for different laser defocus conditions. LIP Fe and LA-ICP-AES Fe emission signals and LIP T_ex decreased when the laser was defocused for the low-alloy steel. On the other hand, when the sediment pellet was ablated, LIP T_ex decreased when the laser was defocused. However, LA-ICP-AES Fe emission signals increased at first, then decreased when the laser was defocused more. It was concluded that LIP T_ex and LIP and LA-ICP-AES Fe emission signals are dependent on laser shot conditions (focus–defocus), and are also dependent on sample type (texture, mineralogy, hardness, conductivity and heat capacity).     

Evaluation of spray chambers for use in inductively coupled plasma-atomic emission spectrometry

A laboratory-built spray chamber featuring aerosol collection at the centre of the chamber by means of a funnel is described and compared with a commercially available, dual tube chamber. The influence of some chamber design parameters on the emission signal intensity and stability, the nebulizer efficiency and chamber clean-out time is studied.     

Determination of impurities in highly pure platinum by inductively coupled plasma-atomic emission spectrometry

In this work, a cyclone spray chamber system is used in conjunction with an inductively coupled plasma-atomic emission spectrometer instead of the conventional Scott-type chamber system to reduce the lower limit of detection achieved by the instrument, and an internal standard element (Y) is introduced to eliminate the effects caused by the drift in the plasma background level. An ICP-AES method for the determination of 13 impurity elements in a highly pure platinum sample has been developed. In this method, it is not necessary either to add a platinum matrix to the calibration standard or to separate and concentrate the elements to be determined in the samples. The effect of the platinum matrix on the elements to be analyzed is corrected for by a background equivalent concentration subtraction method. The determination ranges of the method are as follows: 0.00010-0.0050% for Mg, Mn, Cu, Ag, Fe and Zn; 0.00030-0.015% for Au, Ir, Ni and Pb; 0.00050-0.025% for Rh and Al; and 0.00080-0.040% for Pd. The method is simple, rapid and accurate, and can be applied to the analysis of 99.9–99.995% pure platinum.     

电感耦合等离子体原子发射光谱法测定自来水中的8种元素

采用电感耦合等离子体原子发射光谱法(ICP-AES)测定了化学实验室自来水中铝、钾、锶、钡、锰、钴、钼、硒8种元素的含量;对仪器的工作条件进行了优化,确定了各元素的分析波长和检出限.结果表明,所述方法可以方便地用于测定化学实验室自来水样品中的8种元素,相对标准偏差为0.08%～6.90%.     

Erbium determination in preforms of optical fibres by inductively coupled plasma-atomic emission spectrometry

Erbium which is used in the composition of heavy metal fluoride optical fibres was determined in preforms of these materials by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The new analytical procedure developed comprises: solid sample dissolution, via an alkaline fusion with sodium carbonate, and acid leaching with dilute hydrochloric acid, and measurements of emission intensities of 337.276 nm. This method has a detection limit of 31 ng/ml and a reproducibility of 0.90% r.s.d.     

Determination of arsenic in homeopathic drugs by bromide volatilization-inductively coupled plasma-atomic emission spectrometry

Arsenic in homeopathic drugs was determined by coupling a volatile generation with inductively coupled plasma-atomic emission spectrometry. The method is based on the chemical vaporization of arsenic(III) with bromide ions in sulfuric acid media using a batch procedure and subsequent introduction of the gaseous analyte into the plasma torch. The main and interactive effects of the experimental variables affecting this method were evaluated by a 2-level full factorial design. In optimized conditions by Simplex, the method shows an absolute detection limit (3 s) of 0.28 microg for the injection of 230 microL sample. The precision (% relative standard deviation) of the determination was 4.2% at a level of 50 microg/mL As(III) (n = 5). The interference effect of various ions on the arsenic signal was evaluated.