Collision Reaction Interface Research Articles

Simultaneous Determination of Ultra-Trace Pt, Pd, Rh, and Ir in Gold Mining Residue by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) with an Antimony-Copper Fire Assay and Microwave Digestion

The evaluation of the flow direction of platinum group elements (PGEs) during gold-copper ore mining is challenging due to the uneven distribution and low content. Therefore, it is vital to accurately and simultaneously determine ultra-trace PGEs Pt, Pd, Rh, and Ir in gold mining residue samples. In this study, a method to simultaneously determine ultra-trace Pt, Pd, Rh, and Ir in gold mining residue is reported using Sb–Cu fire assay, microwave digestion, and inductively coupled plasma-mass spectrometry (ICP-MS). The Sb–Cu fire assay was used to enrich Pt, Pd, Rh, and Ir, obtaining Sb–Cu alloy particles that concentrate these elements. An optimal microwave method was employed to digest the Sb–Cu alloy particles. In ICP-MS, the collision reaction interface was used to eliminate the interferences of other elements and improve the accuracy. Moreover, the matrix-matched multi-external standards combined with internal standard calibration were utilized to reduce the error. High concentrations of Au, Ag, and Pb showed no interferences with Pt, Pd, Rh, or Ir determination. The limits of detection for Pt, Pd, Rh, and Ir were 0.018, 0.052, 0.064, 0.035 ng·g−1, respectively, and the relative standard deviation was 5.18, 4.66, 1.55, and 3.17%. Additionally, the determination of Pt, Pd, Rh, and Ir in standard reference materials showed good agreement with the certified values. In summary, a reliable and efficient method is provided to determine various PGEs which is of great significance for gold-copper ore mining.

Strategies to overcome interferences in elemental and isotopic geochemical analysis by quadrupole inductively coupled plasma mass spectrometry: A critical evaluation of the recent developments.

Quadrupole Inductively Coupled Plasma Mass Spectrometry (ICP-MS) instruments were introduced into geochemical and mineral exploration laboratories nearly four decades ago, providing a technique that could meet their longstanding requirement for the precise and accurate determination of several groups of trace elements and isotopes in geological materials such as rocks, minerals, ores, soils, sediments, and natural water samples. Despite its popularity among geochemists, the technique suffered from spectral and non-spectral interferences some of which seriously affected the quality of the data generated. These interferences have also had a significant impact on the ability of ICP-MS systems to achieve low detection limits. Over the last three decades, technical advances such as the development of high-resolution (HR)-ICP-MS, cool plasma, collision/reaction cell technology (CCT), dynamic reaction cell (DRC) technology, collision reaction interface (CRI), kinetic energy discrimination (KED), tandem mass spectrometry (ICP-MS/MS)/triple quadrupole ICP-MS, and multi-quadrupole ICP-MS have been introduced to eliminate/minimize many of these interferences, with each technique having its strengths and limitations. These technologies have extended the range of elements that can be measured accurately not only in geological materials, but also in several other matrices, with lower detection limits than before. In addition, other methods such as internal standardization, isotope-dilution, standard addition and matrix-matching calibrations have contributed to improving the quality of the data. This paper provides a review of these new developments from the geochemical analysis point of view.

Fundamentals of the collision reaction interface in inductively coupled plasma mass spectrometry: Using ion kinetic energies and collision cross section measurements to characterize the collision region

The collision reaction interface (CRI) removes polyatomic ions in inductively coupled plasma mass spectrometry (ICP-MS) by introducing a collision gas directly into the plasma expansion as ions are extracted into the mass spectrometer. Many collisions and reactions occur in a relatively short region (~ 2 mm long), much shorter than with other instruments that use multipole collision cells. In this paper, experiments are first described for the estimation of the collision cross sections of singly charged cations employing the use of a hexapole collision cell. Based on those determined cross sections, general characteristics of the collision region in the CRI are determined and discussed.

Triethylamine-assisted Mg(OH)2 coprecipitation/preconcentration for determination of trace metals and rare earth elements in seawater by inductively coupled plasma mass spectrometry (ICP-MS)

In this paper, we report an improved magnesium hydroxide, Mg(OH)2, coprecipitation method for the determination of 16 trace elements (Al, V, Cr, Mn, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Sb, Sn and Pb) and 18 rare earth elements (REEs), including Sc, Y, U and Th in seawater and estuarine water samples. The procedure involves coprecipitation of the trace elements and REEs on Mg(OH)2 upon addition of a small volume of triethylamine (TEA) followed by analysis of the dissolved pellet solutions by inductively coupled plasma mass spectrometry (ICP-MS). Three-step sequential coprecipitation was carried out on 10 mL aliquots of seawater to eliminate the matrix ions and to preconcentrate the analytes of interest into a 1 mL final volume. Spike recoveries varied from 85% (Th) to 105% (Y). Calcium (Ca), sodium (Na) and potassium (K) matrices were virtually eliminated from the analysis solutions. Collision reaction interface (CRI) technology utilizing H2 and He gases was employed to determine its effectiveness in removing the spectral interferences originating from the residual Mg matrix, TEA and plasma gases. H2 was more effective than He in reducing spectral interferences from TEA and plasma gases. Limits of detection (LODs) ranged from 0.01 ng L−1 (Ho) to 72 ng L−1 (Al). The method was validated by using certified seawater (CASS-4) and estuarine water (SLEW-3) reference materials. Precision for five (n = 5) replicate measurements were between 1.2% (Pr) and 18% (Lu). Fe, Pb, Sn, and Zn impurities in TEA were significant in comparison to the levels in CASS-4 and SLEW-3, while relatively high background signals impacted determinations of low levels of Sc and Th. The effects of these hurdles on precision and accuracy were alleviated by measuring these elements in spiked CASS-4 and SLEW-3.

Determination of Selenium in Bovine Semen by ICP-MS Using Formic Acid for Sample Preparation

Determination of Se by inductively coupled plasma mass spectrometry (ICP-MS) can be difficult due to spectral interferences; however, these interferences can be eliminated by using collision-reaction interface (CRI) technology. A simple and fast procedure for determination of total Se concentration in bovine semen by ICP-MS after sample solubilization with diluted formic acid is here proposed. Formic acid caused an increase of up to 50% in selenium net signals and the maximum gain was obtained at 10% v v-1 formic acid solution. The optimized nebulizer gas flow rates were 1.05 and 0.95 L min-1, and radio frequency applied power were 1.3 and 1.4 kW without and with CRI, respectively. Microwave-assisted acid digestion was also implemented in the preparation of semen sample for comparison of results. No statistical differences between these sample preparation strategies at 95% confidence level (t-test) were observed for 76Se+ , 77Se+ , 78Se+ and 82Se+ without using CRI and 82Se+ with CRI.

The effects of analyte mass and collision gases on ion beam formation in an inductively coupled plasma mass spectrometer

Planar laser induced fluorescence (PLIF) was used to evaluate the effect of matrix components on the formation and focusing of a Ba ion beam in a commercial inductively coupled plasma mass spectrometer. Cross sections of the ion beams were taken in the second vacuum stage, in front of the entrance to the mass analyzer. Under normal operating conditions, the addition of Pb shifted the position of the Ba ion beam to the right. PLIF was also used to evaluate the effect of a collision reaction interface (CRI) on Ca and Ba ion beams. A wider velocity distribution of ions and a decrease in overall intensity were observed for the CRI images. The fluorescence and mass spectrometer signals decreased with increased CRI flow rates. These effects were most obvious for Ca ions with He gas.

Polyatomic interference removal using a collision reaction interface for plutonium determination in the femtogram range by quadrupole ICP-MS

This paper proposes a new method for accurately determining low-level 239Pu using quadrupole ICP-MS with collision reaction interface (CRI) technology. A helium CRI gas flow rate of 70 mL min−1 with a radiofrequency power of 1.4 kW was found to be suitable for the removal of the 238UH+ interference in order to accurately determine 239Pu. The optimum instrument conditions were applied to a quantitative analysis, which produced a 239Pu calibration with excellent linearity. The proposed method achieved 239Pu recoveries between 96-98 % and low detection limits of 0.15 fg mL−1.

Estimation of the bio-accessible fraction of Cr, As, Cd and Pb in locally available bread using on-line continuous leaching method coupled to inductively coupled plasma mass spectrometry

A previously developed, efficient and simple on-line leaching method was used to assess the maximum bio-accessible fraction (assuming no synergistic effect from other food and beverage) of potentially toxic elements (Cr, As, Cd and Pb) in whole wheat brown and white bread samples. Artificial saliva, gastric juice and intestinal juice were successively pumped into a mini-column, packed with bread (maintained at 37°C) connected on-line to the nebulizer of an inductively coupled plasma mass spectrometry (ICP-MS) instrument equipped with a collision-reaction interface (CRI) using hydrogen as reaction gas to minimize carbon- and chlorine-based polyatomic interferences. In contrast to the conventional batch method to which it was compared, this approach provides real-time monitoring of potentially toxic elements that are continuously released during leaching. Mass balance for both methods was verified at the 95% confidence level. Results obtained from the whole wheat brown and white bread showed that the majority of Cr, Cd and Pb was leached by gastric juice but, in contrast, the majority of As was leached by saliva. While there was higher total content for elements in whole wheat bread than in white bread, a higher percentage of elements were bio-accessible in white bread than in whole wheat bread. Both the on-line and batch methods indicate that 40–98% of toxic elements in bread samples are bio-accessible. While comparison of total analyte concentrations with provisional tolerable daily intake values may indicate some serious health concern for children, when accounting for the bio-accessibility of these elements, bread consumption is found to be safe for all ages.

Optimization of Sample Preparation in the Determination of Minerals and Trace Elements in Honey by ICP-MS

In this paper, analytical procedures are proposed for determination of inorganic constituents in honey samples from different regions of Brazil. Inductively coupled plasma with mass spectrometry detection (ICP-MS) was used to determine the analytes, using two different sample preparation methods: acid mineralization in block digester and microwave-assisted acid digestion. The methods were optimized in order to minimize the final acidity and the residual carbon content after the sample preparation. It was observed that mineralization using microwave radiation with 2 mol L−1 HNO3 was the most suitable method for determination of minerals and trace elements by ICP-MS. Besides, Se, Mg, Ca, Al, P, Mn, Fe, Cu, Zn, Ba, and Pb were determined in 60 honey samples by ICP-MS. The appropriate instrumental conditions were also evaluated for this determination, as the need of the use of collision–reaction interface and internal standards. The accuracies were evaluated using two certified reference materials, and the recoveries ranged from 82 to 115 %. The results showed no evidence of contamination in the honey samples analyzed.

Accurate Analysis of Chromium in Foodstuffs by Using Inductively Coupled Plasma Mass Spectrometry with a Collision-Reaction Interface

Food is a common source of chromium (Cr) exposure. However, it is difficult to analyze Cr in complex food matrices by using inductively coupled plasma mass spectrometry (ICP-MS) because the major isotope, <TEX>$^{52}Cr$</TEX>, is masked by interference generated by the sample matrix and the plasma gas. Among the systems available to minimize interference, the recently developed collision-reaction interface (CRI) has a different structure relative to that of other systems (e.g., collision cell technology, octopole reaction system, and dynamic reaction cell) that were designed as a chamber between the skimmer cone and quadrupole. The CRI system introduces collision or reaction gas directly into the plasma region through a modified hole of skimmer cone. We evaluated the use of an CRI ICP-MS system to minimize polyatomic interference of <TEX>$^{52}Cr$</TEX> and <TEX>$^{53}Cr$</TEX> in various foodstuffs. The <TEX>$^{52}Cr$</TEX> concentrations measured in the standard mode were 2-3 times higher than the certified values. This analytical method based on an ICP-MS system equipped with a CRI of helium gas was effective for Cr analysis in complex food matrices.

Tungsten coil electrothermal matrix decomposition and sample vaporization to determine P and Si in biodiesel by inductively coupled plasma mass spectrometry

A tungsten coil extracted from commercially available microscope light bulbs is used to decompose the organic matrix and vaporize biodiesel samples for P and Si determination by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). The vaporization cell is connected to a modified sheath gas tube so that sample vapors are mixed with a continuous aerosol flow exiting the ICP-MS nebulization chamber. Helium and H2 are used with a collision–reaction interface (CRI) to minimize spectral interferences and obtain low baseline spectra. These strategies contribute to improving repeatability and accuracy. A small solid state constant current power supply is used to resistively heat the vaporizer and 10 μl sample aliquots are introduced manually on the coil with a micropipette. Limits of detection of 0.4 and 0.1 mg kg−1 are obtained for P and Si, respectively. Reference biodiesel samples are used to check the accuracy of the procedure for P. A spike experiment is carried out to assess accuracy in Si determinations. No statistically significant differences are observed for reference and determined values by applying a t-test at a 95% confidence level. The direct analysis of biodiesel by tungsten coil ETV-ICP-MS is a fast and effective alternative to determine challenging elements like P and Si.

Evaluation of a Collision-Reaction Interface (CRI) for Carbon Effect Correction on Chromium Determination in Environmental Samples by ICP-MS

Spectral interferences in inductively coupled plasma quadrupole mass spectrometry (ICP-MS) may affect several trace element analyses. In this work, the performance of a collision-reaction interface (CRI) for correction of spectral interferences on chromium determination at m/z 52 affected by 40Ar12C+ in a rich-carbon medium was evaluated. Hydrogen or He gases were introduced through sampler or skimmer cones of the CRI for promoting collisions and reactions. Background equivalent concentrations (BEC) and signal-background ratios (SBR) were the chosen parameters for evaluating CRI performance. It was observed that the introduction of both gases through the sampler cone was not effective considering the maximum gas flow rate evaluated at 140 mL min−1. The best condition to reduce polyatomic interferences caused by carbon containing species was obtained while introducing 60 mL min−1 of H2 through the skimmer cone. The trueness of the developed procedure was checked by 52Cr+ determination in certified reference materials. Sequential extractions in acetic acid and ammonium acetate (carbon sources) media, according to the Bureau Communautaire de Référence (BCR) of the Commission of the European Communities, was employed for BCR 701 (Lake Sediment) and microwave-assisted digestion was applied for Sewage Sludge from Industrial Origin (BCR 146 R). The feasibility of the CRI to overcome spectral interferences caused by molecular ions containing carbon on 52Cr+ determined by ICP-MS was demonstrated.

Assessment of Polyatomic Interferences Elimination Using a Collision Reaction Interface (CRI) for Inorganic Analysis of Fuel Ethanol by ICP-QMS

The effectiveness of a collision-reaction interface (CRI) as instrumental device and the addition of oxygen in the composition of auxiliary gas were evaluated to minimize polyatomic species generated in plasma gas caused by direct introduction of fuel ethanol samples through spray chambers in inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). The oxygen flow-rate was optimized as a compromise among signal counts, signal to background ratio (SBR), and background equivalent concentration (BEC). For 12.5 mL min−1 O2, ethanol samples diluted 20 times were introduced into the plasma and deposits of carbon compounds on the sampler and/or skimmer cones were not observed. The performance of CRI using H2 and He inserted through the sampler or skimmer cones was evaluated. Hydrogen gas added through the skimmer cone was more efficient to reduce blank and BEC values. This strategy was necessary to eliminate spectral interferences caused by 40Ar12C+, 40Ar16O+, 12C16O+, at isotopes 52Cr+, 56Fe+, 28Si+ and 24Mg+, respectively. Using matrix-matching calibration and Y internal standard, the optimized method was applied to the determination of Al, Ba, Co, Cr, Cu, Fe, Mg, Mn, Mo, Na, Ni, Pb, Sb, Si, V, and Zn in fuel ethanol. Accuracy of developed method was checked after addition/recovery tests. Recoveries and RSD (n = 12) for all elements varied within the 78–114% and 0.4–2% ranges, respectively. Limits of detection for all elements obtained by combining CRI and ICP-QMS were always better than 0.80 µg L−1 except for Si at 14 µg L−1.

Performance evaluation of collision–reaction interface and internal standardization in quadrupole ICP-MS measurements

The combined use of internal standardization with collision and reaction interface in an inductively coupled plasma quadrupole mass spectrometer (ICP-QMS-CRI) was evaluated. The behavior of several elements (Ba, Cd, Co, Cr, Cu, Li, Mn, Mo, Pb, Sb, V and Zn) was studied by introducing H2 or He through the skimmer and sampler cones of the CRI device and by using In, Rh and Sc as internal standards. Certified reference material of trace elements in water (NIST 1643e) was used to evaluate the performance of the method. A vinegar sample and mixed food diet standard reference material were directly introduced into the equipment as complex matrices for Cr and V determinations. Improvements in accuracy and precision were attained combining both strategies. The introduction of H2 through the skimmer cone was the best way to overcome polyatomic ions formation and to improve SBR and BEC values for several elements. The use of Sc as internal standard improved the performance of ICP-QMS-CRI.

Determination of the total and extractable mass fractions of cadmium and lead in mineral feed by using isotope dilution inductively coupled plasma mass spectrometry

This paper describes the determination of the total and extractable mass fractions of Cd and Pb in mineral feed test sample distributed by the Community Reference Laboratory for Heavy Metals in Feed and Food (CRL-HM), in the frame of the fifth interlaboratory comparison for the European Union National Reference Laboratories (NRL). The developed in this study protocol for the total and extractable mass fractions of Pb and Cd in mineral feed sample is based on isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS). The applied dual spiking approach reduced by 50% the number of analytical steps. The addition of hydrofluoric acid in the digestion step was found necessary to ensure a full decomposition and complete isotope equilibration. Quadrupole inductively coupled plasma mass spectrometer equipped with collision reaction interface (CRI) was employed for the measurements of Cd and Pb. Two methods for the determination of Cd were applied and compared. In the first one the high molybdenum content was reduced by introduction of matrix separation step followed by standard ICP-MS mode measurement, whereas in the second one CRI mode was used for the determination of Cd without preliminary matrix separation. The estimation of the combined uncertainty was performed according to the ISO guidelines. Uncertainty propagation was used as a tool for validation of proposed analytical procedure. Contributions from the correction for moisture content, sample homogeneity, procedural blank, instrumental background and dead time effects were evaluated in both cases. The largest uncertainty contributors for Cd and Pb is due to the within bottle homogeneity of the mineral feed sample – 50.3% and 90% respectively. The IUPAC data for isotope composition are the second major contributor to the combined uncertainty of the result for the total mass fraction of Cd in mineral feed – 43.3%. However, the ID ICP-MS results achieved from the two series of samples (partial and total extraction) were in excellent agreement within uncertainty, irrespective of the method used for extraction. The ID ICP-MS results for the total and extractable mass fractions of Cd and Pb in feed sample were compared with the results obtained with external calibration approach and routinely applied in the daily analytical practice of the Belgium National Reference Laboratory for trace elements in food and feed.

Combination of cool plasma and collision-reaction interface for correction of polyatomic interferences on copper signals in inductively coupled plasma quadrupole mass spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS) is an important instrumental technique for elemental analysis. However, some elements suffer from spectral interferences caused by ions derived from argon plasma gas and matrix components. The determination of copper isotopes is affected by 40Ar 23Na + and 40Ar 25Mg +. The performance of an ICP-MS with a collision reaction interface (CRI) and cool plasma conditions for correction of spectral interferences was evaluated here. The efficiency of the CRI was studied introducing H 2 or He through sampler and skimmer cones. Gas introduction through the sampler cone was ineffective. Complete elimination of spectral interferences was reached when introducing 60 or 80 mL min −1 of H 2 in the skimmer cone, but sensitivity losses were as large as 99%. Further, the effect of interferences was checked when the argon plasma was operated under cool plasma conditions. The effects of the applied radiofrequency (0.6, 0.8, 0.9, and 1.0 kW), sampling depth (5.5, 8.5 and 11.5 mm), and dwell time (25 and 50 ms) were studied considering interference reduction and sensitivities. Best conditions were reached at 0.8 kW. Subsequently, both CRI and cool plasma conditions were combined to evaluate their performance on reduction of polyatomic Na and Mg argide interferences. Spectral interferences were eliminated using a CRI with 20 mL min −1 H 2 introduced through the skimmer cone, cool plasma conditions at 0.8 kW and sampling depth of 8.5 mm. This work demonstrated the feasibility of combining CRI and cool plasma for circumventing some spectral interferences on Cu determination by ICP-QMS.

Determination of Cd, Cr, Hg and Pb in plastics from waste electrical and electronic equipment by inductively coupled plasma mass spectrometry with collision–reaction interface technology

A procedure based on the use of a quadrupole inductively coupled plasma-mass spectrometer equipped with a collision-reaction interface (CRI) for control of spectral overlap interferences was developed for simultaneous determination of Cd, Cr, Hg, and Pb in plastics from waste electrical and electronic equipment (WEEE). The injection of H 2 and He (80 and 60 mL min −1, respectively) into the sampled plasma, colliding and reacting with potentially interfering polyatomic ions, allows interference-free determination of chromium via its isotopes 52Cr and 53Cr that are freed from overlap due to the occurrence of 40Ar 12C +, 40Ar 12C 1H +, 36S 16O + or 1H 36S 16O +. Cadmium, Hg and Pb were directly determined via their isotopes 110Cd, 111Cd, 112Cd, 199Hg, 200Hg, 201Hg, 202Hg, 206Pb, 207Pb, and 208Pb, without using CRI. The CRI can be quickly activated or deactivated before each analyte measurement. Limits of detection for 52Cr were 0.04 or 0.14 μg L −1 with He or H 2 injected in CRI. Cadmium and Pb have LODs between 0.02 and 0.08 μg L −1 and Hg had 0.93–0.98 μg L −1, without using CRI. Analyte concentrations for samples varied from 16 to 43, 1 to 11, 4 to 12, and 5 to 13 mg kg −1 for Cr, Cd, Hg and Pb, respectively.

Interference standard: a new approach to minimizing spectral interferences in inductively coupled plasma mass spectrometry

Spectral interferences are the most critical issue in inductively coupled plasma mass spectrometry determinations. The effects of isobaric polyatomic ions on accuracy often represent an important limitation to the application of this technique to more complex matrices. This aspect is especially critical in quadrupole-based instruments and the most common approaches to minimizing the problem are based on collision-reaction cells and interfaces. In this work a new strategy based on minimizing the interfering ion signal variation is used to improve accuracy in K, As, P and Si determinations. Different from traditional internal standard methods, argon species naturally present in the plasma are used as probes to correct fluctuations in the interfering ion rather than in the analyte signal. Accuracy is significantly improved with no instrumental modification or post-plasma reactions. At the best conditions, recoveries ranging from 86 to 107% were obtained for all elements evaluated in different certified reference materials and spiking studies. Results were comparable and sometimes better than recoveries obtained with a collision–reaction interface. Adequate precision, accuracy and sensitivity were obtained while using the 38Ar+ probe even for isotopes prone to severe isobaric interferences such as 28Si.

Behaviour of arsenic and selenium in an ICP-QMS with collision and reaction interface

The performance of a collision reaction interface (CRI) for minimization of spectral interferences on analytical signals of 75As+ and 76Se+, 77Se+, 78Se+, 80Se+ and 82Se+ isotopes was evaluated by using H2 and He gases introduced through the sampler or skimmer cones of an inductively coupled plasma quadrupole mass spectrometer (ICP-QMS). Different gas flow rates were tested employing reference solutions prepared either in hydrochloric acid or in water soluble tertiary amines (CFA-C) media as carbon source. A hydrogen gas flow rate at 60 mL min−1 introduced through skimmer cone was effective for minimizing polyatomic interferences on 75As+ and Se isotopes, except for 80Se+. The use of He introduced through sampler or skimmer cones had a minor effect on the minimization of interferences when compared to the use of H2 gas. Moreover, it was observed that the gas introduction through the sampler cone had no effect on interferences when using gas flow rates up to 80 mL min−1 for both gases evaluated. Based on these results, it can be recommended to use H2 gas introduced through skimmer cone of the CRI for correcting polyatomic interferences on 75As+ and Se isotopes in matrixes containing up to 2% v v−1 chloride.