Determination Of Platinum Group Metals Research Articles

A new preconcentration technique for the determination of PGMs and gold by fire assay and ICP-OES

Accurate determination of platinum group metals (PGMs) and gold (Au) has always proven to be a difficult task, due to their low concentrations in platiniferous ores. The most common preconcentration technique used in analysis of these metals is fire assay with a flux containing nickel or lead. This technique can be improved by using co-collectors. Here we hypothesise that Fe, Co, and Cu can be used as co-collectors to enhance separation and preconcentration of PMGs and gold by fire assay. To test this hypothesis, geological exploration samples from Siyanda Union Mine (Northam, South Africa) were analysed by an inductively coupled plasma-optical emission spectrometer (ICP-OES) for PGMs (Pt, Pd, and Rh) and Au. A control sample (certified reference material AMIS 0426) was also analysed by the same technique. The PGM and Au recoveries from the control sample ranged from 83% to 105% for all three co-collectors, with relative standard deviations less than 10% for the control sample and 7% for the geological samples. The PGM and Au recoveries by Fe and Co co-collectors were modestly higher than that of the Cu-collector. These results indicate that Fe and Co are better co-collectors than Cu, presumably due to the loss of analyte when using Cu. Taken together, Fe and Co co-collectors can be viable alternatives for analysis of PGMs and gold using the fire assay method.

Variation in the determination of platinum group metals using ICP OES induced by the effect of complex matrices and the correction method based on multivariate calibration

We reveal the effect of matrix complexity on the quantitative determination of platinum group metals (PGMs) using inductively coupled plasma optical emission spectrometry. The variation in PGM determination is compensated by employing the multivariate calibration technique.

Determination of platinum group metals in dust, water, soil and sediments in the vicinity of a cement manufacturing plant

Global economic growth has led to an increase in cement production to meet the demand of infrastructural development over the past decades. This has resulted in cement factories being the major sources of dust pollution. Dust emanating from the cements plants deposits on buildings, roadways, on road pavements and plants. The purpose of this study was to determine the concentration of platinum group metals (PGMs) emitted with cement dust on a dust suppressed roadway next to a cement factory in Waterberg, South Africa. The concentrations of PGMs were determined using inductively coupled optical emission spectrometry. This region is well known for large reserves and mining of PGMs such as Pt, Rh, Ru and Pd. The highest concentration in the dust samples collected along the roadway was that of Pt followed by Ru, Rh and Pd. The concentrations of Pt, Ru, Rh and Pd in soil samples decreased with the increase of depth. Water concentration of PGMs decreased at each sampling point in the following order; Pt > Ru > Rh > Pd. Sediments samples were also sampled along the Crocodile River for characterisation of physico-chemical parameters. It was of great importance to also analyse PGMs in soils, water and sediments since, dust settles on them. Elevated concentrations of Pt were observed in all samples and the highest concentrations were partitioned to the small particle size fraction of 32 µm. The pH and electric conductivity (EC) of the sediments were measured and the pH values increased while EC values decreased moving along the river. The most common minerals identified in the dust samples were quartz and calcites. Vehicular emissions were also found to be the major contributor to suspended particulate matter and atmospheric deposition of dust dominantly result from emission from the cement plant. The cement plant was the major polluter through atmospheric deposition of dust particles. The result also revealed that the pH of the Crocodile River was slightly alkaline which was influenced by the effluent from the cement plant.

The HR-CS-GF-AAS determination and preconcentration of palladium in contaminated urban areas, especially in lichens

The increasing content of platinum group metal particles emitted into the environment by car traffic is gradually attracting the attention of the scientific community. However, the methods for the determination of platinum group metals in environmental matrices are either costly or suffer from low sensitivity. To facilitate the use of less sensitive, but significantly cheaper, devices, the preconcentration of platinum group metals is employed. For platinum, a multitude of preconcentration approaches have been published. On the contrary, the preconcentration approaches for palladium are still rare. In this work, the development, optimization, and testing of a new approach is described; it is based on a preconcentration of palladium on octadecyl modified silica gel together with the complexing agent dimethylglyoxime, and it is then analyzed with the high-resolution continuum-source atomic absorption spectrometry. For comparison, a newly developed sorbent, QuadraSil™ TA, with a high affinity for platinum group metals was also tested. The preconcentraiton approach was tested on the lichen Hypogymnia physodes, which served as a bioindicator of palladium emissions. The case study site was a mid-sized city in central Europe: Brno, Czech Republic. The dry “bag” monitoring technique was used to collect the palladium near roads with a large span of traffic density. The developed analytical approach confirmed an increasing concentration of palladium with increasing exposure time and intensity of the traffic. Consequently, a simple relationship between the amount of bioaccumulated palladium and traffic density was established.

Current State and Problems of Analytical Control of Spent Automobile Catalysts (Review)

Abstract—Spent Automobile Catalysts (SACs) hold a special place among secondary raw materials containing precious metals. Accurate determination of platinum group metals in SACs plays an important role influencing the economic efficiency of the utilization process. In this work, we review the methods of analysis of SACs available in the literature, as well as methodological developments of the Giredmet Institute in collaboration with Anserteko and NUST “MISiS”. The main emphasis is placed on the use of modern tools for chemical preparation of hard-to-break objects like SACs, including autoclave and microwave opening of the samples. The advantages of the assay concentration method based on developments at the Yekaterinburg Non-Ferrous Metals Processing Plant for analysis of SACs are considered. We discuss certified spectroscopic and chemical methods which have been developed for analysis of spent automobile catalysts and outline the ways of their further improvement.

Catalytic methods for determination of platinum group metals (Review)

The present state of the art, accomplishments, and prospects of kinetic catalytic methods for determination of rare platinum group metals are considered. Indicator reactions and methods based on them suggested during the last 20 years are reviewed; their metrological characteristics are presented. Results of investigation of catalytic activity of different forms of platinum group metals in solution are described. The peculiarities of conducting of a number of catalytic indicator reactions in flow and test systems are considered.

Stripping voltammetric determination of palladium, platinum and rhodium in freshwater and sediment samples from South African water resources

Stripping voltammetry as technique has proved to be very useful in the analysis of heavy and other metal ions due to its excellent detection limits and its sensitivity in the presence of different metal species or interfering ions. Recent assessments of aquatic samples have shown increased levels of platinum group metals (PGMs) in aquatic ecosystems, caused by automobile exhaust emissions and mining activities. The development of an analytical sensor for the detection and characterisation of PGMs were investigated, since there is an ongoing need to find new sensing materials with suitable recognition elements that can respond selectively and reversibly to specific metal ions in environmental samples. The work reported shows the successful application of another mercury-free sensor electrode for the determination of platinum group metals in environmental samples. The work reported in this study entails the use of a glassy carbon electrode modified with a bismuth film for the determination of platinum (Pt2+), palladium (Pd2+) or rhodium (Rh2+) by means of adsorptive cathodic stripping voltammetry. Optimised experimental conditions included composition of the supporting electrolyte, complexing agent concentration, deposition potential, deposition time and instrumental voltammetry parameters for Pt2+, Pd2+ and Rh2+ determination. Adsorptive differential pulse stripping voltammetric measurements for PGMs were performed in the presence of dimethylglyoxime (DMG) as complexing agent. The glassy carbon bismuth film electrode (GC/BiFE) employed in this study exhibit good and reproducible sensor characteristics. Application of GC/BiFE sensor exhibited well-defined peaks and highly linear behaviour for the stripping analysis of the PGMs in the concentration range between 0 and 3.5 μg/L. The detection limit of Pd, Pt and Rh was found to be 0.12 μg/L, 0.04 μg/L and 0.23 μg/L, respectively for the deposition times of 90 s (Pd) and 150 s (for both Pt and Rh). Good reproducibility was also observed and the practical applicability of the sensor was demonstrated with the analysis of environmental water and sediment samples.

Laser ablation-inductively coupled plasma-mass spectrometry using a double-focusing sector field mass spectrometer of Mattauch–Herzog geometry and an array detector for the determination of platinum group metals and gold in NiS buttons obtained by fire assay of platiniferous ores

This paper explores the potential of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for the determination of Au, Ir, Pd, Pt, Rh and Ru in NiS buttons obtained by fire assay of platiniferous ores using a new type of ICP-MS instrument equipped with an array detector Mattauch–Herzog spectrometer. The method evaluated comprises the NiS fire assay of a representative amount of the ore sample (40–75 g), grinding of the NiS buttons subsequently obtained, pelleting of the resulting powders using polyethylene wax as a binder, and LA-ICP-MS analysis of the sample using in-house matrix-matched standards for calibration. The use of this new ICP-MS device proved very beneficial in this context, offering a remarkable level of precision (2–3% RSD for the most abundant analytes, Pt, Pd, Rh and Ru, and 6–11% RSD for Au and Ir) owing to its simultaneous capabilities and its extended linear range, which enabled an improved performance of the internal standard (61Ni). Moreover, the low level of argide-based interferences and the detection power of the instrument provided low limits of detection (10 ng g−1 level) even for those elements that could be potentially affected by ArNi+ and ArCu+ overlap in this particular matrix (Pd, Rh, Ru). The accuracy finally obtained (90% of results within 10% of the reference value, and 70% of results within 5%) is fit-for-purpose for this application. The resulting method can be thus considered very attractive as a faster and greener strategy for the control of these types of samples in the platinum group metal industry, circumventing the need for the cumbersome and environmentally unfriendly digestion procedures currently employed.

Femtosecond laser ablation-ICP-mass spectrometry analysis of a heavy metallic matrix: Determination of platinum group metals and gold in lead fire-assay buttons as a case study

Owing to the shorter time interval during which energy is delivered to the sample material, femtosecond (fs) laser ablation is preferable over nanosecond laser ablation for metallic samples. In this project, the influence of various laser parameters—beam diameter, repetition rate and laser fluence—on the ablation of Pb as a heavy metallic matrix using an infrared (λ = 795 nm) fs-LA system (150 fs pulse duration) was studied. The merits of Ar and He as carrier gases were compared and as He did not provide a substantial improvement in the limits of detection, while deposition of sample material on the window of the ablation chamber was more pronounced, Ar was selected for all further measurements. The effect on the ICP caused by the introduction of various amounts of sample aerosol was studied by monitoring the signal intensity for 38Ar+. It was shown that maximizing the amount of sample ablated and thus, the amount of sample aerosol introduced into the ICP, did not result in maximum sensitivity, which was rather obtained under ‘compromise’ conditions. Subsequently, femtosecond LA-quadrupole-based ICP-mass spectrometry (ICP-MS) was used for the determination of traces of the platinum group metals (PGMs) Rh, Pd, Ru, Ir and Pt and of Au in Pb buttons obtained by fire assay of platiniferous ore reference materials. The signal of 204Pb+ was used as an internal reference, correcting for variations in the laser ablation and transport efficiencies and in the instrument's sensitivity. The spectral interferences established for some of the target nuclides due to the occurrence of Pb2+ ions were successfully overcome by pressurizing the reaction cell with NH3. Quantification versus a calibration curve constructed on the basis of the results obtained for matrix-matched standards (> 99% Pb) provided excellent accuracy, superior to those obtained using nanosecond LA-ICP-MS. Also the limits of detection were improved by a factor ranging between 3 and 10 and are <0.010 μg g−1 for the most important PGMs (Rh, Pd, Pt) and Au. Several measures, such as the use of a large ablation cell and housing up to 10 Pb buttons, were taken to increase the sample throughput. In the same context, day-to-day reproducibility of the calibration curve was also examined. When recording a ‘fresh’ calibration curve every day, the average bias between the experimental results and the corresponding reference values was established to be <2.5% for every target element. When using one calibration curve during three consecutive days, the bias still remains <10%, while the sample throughput is increased and analysis of several tens of buttons per day is feasible (10–15 min total analysis time per sample).

Determination of platinum-group metals and gold in the group extract by inductively coupled plasma atomic emission spectrometry after the autoclave decomposition of geological samples

An ICP AES procedure is developed for the direct determination of all platinum-group metals (PGM) and Au in an extract based on the correlation between the main constituents of the analytical cycle. Concentrations interfering with the determination PGM and Au in the extract admissible for ICP AES were found. It was shown that the extraction system (a mixture of p-alkylaniline with oil sulfides in o-xylene or in post-xylene fractions) is compatible with ICP, ensures the 10- to 20-fold preconcentration of PGM and Au and the necessary depth of extract purification (106) of the interfering elements. The accuracy of the procedure is confirmed by results of analyses of seven certified reference samples (GSO) and the agreement with the results of the reference ETA AAS determination. The procedure was tested on raw materials and products of a copper-nickel plant for the determination of all PGM, including osmium and Au in the concentration range 10−7 to 10−4%.

Platinum group metals bulk analysis in automobile catalyst recycling material by laser-induced breakdown spectroscopy

Development and application of an in-situ applicable method to provide rapid determination of platinum group metals (platinum, palladium, and rhodium) elemental concentration in automobile catalyst scrap is reported. Application is based on laser-induced breakdown spectroscopy (LIBS). Actual automobile catalyst slurry in powder form was used to develop the application. With a method requiring approximately 1.5 min of examination per sample, calibration curves are presented with linear regression coefficients close to 0.99 and stability better than 3.0%.

Laser ablation-inductively coupled plasma-dynamic reaction cell-mass spectrometry for the determination of platinum group metals and gold in NiS buttons obtained by fire assay of platiniferous ores

This paper discusses the potential of laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) for the determination of Au, Ir, Pd, Pt, Rh and Ru in NiS buttons obtained by fire assay of platiniferous ores. The method finally proposed is based on: (i) the sampling of large amounts of ores (40–75 g) in order to compensate for the typical inhomogeneous distribution of the target elements over the sample matrix; (ii) the grinding of the NiS buttons obtained after the fire assay procedure in order to obtain more homogeneous samples and the subsequent pelleting of the resulting powders using polyethylene wax as a binder; (iii) LA-ICPMS analysis based on the use of the line profiling mode for ablation of a representative portion of sample during each replicate measurement; (iv) the pressurization of the dynamic reaction cell (DRC) with ammonia in order to cope with all spectral interferences, and the optimization of the RPq setting to prevent the clustering of ammonia with the main matrix components (Ni, Cu), which could otherwise give rise to new spectral overlaps; and (v) the use of home-made matrix-matched standards for calibration, combined with the monitoring of 61Ni as an internal reference. In this way, it was feasible to obtain accurate values for all of the samples investigated with RSD values typically below 10% and LODs at the 10 ng g−1 level. This performance makes the method appealing for the control of these types of samples in the platinum group metal industry, successfully circumventing the need for the cumbersome digestion procedures currently in use.

Methods of determination of light platinum metals and potentialities of the precision spectrophotomertic method with internal referencing as applied to analysis of elements

Methods of determination of platinum group metals and potentialities of precision spectrophotometry with internal referencing were reviewed in the context of recovery of these metals from spent nuclear fuel.

Solid sampling in the determination of precious metals at ultratrace levels

The determination of platinum group metals in solid samples at ultratrace levels is demanded in many situations. This complicated analytical task traditionally requires a complex, time-consuming analytical procedure if sample digestion is intended. This article discusses recent advances in several analytical techniques (spark-optical emission spectrometry, graphite furnace-atomic absorption spectrometry, electrothermal vaporization-inductively coupled plasma-mass spectrometry (ICP-MS), laser ablation-ICP-MS and glow discharge-MS) that can provide quantitative results by direct analysis of the solid samples. They increase both the sample throughput and the sensitivity while diminishing contamination issues, and enable the determination of these elements at levels below 10 μg/g. Obviously, these solid-sampling techniques result in a higher risk of matrix effects and spectral overlap. In order to compare the strengths and weaknesses of the different techniques evaluated, we will discuss different strategies to cope with these problems, such as the separate vaporization of the analytes and the interfering species in time or the use of chemical or mass resolution.

Comparison of the solid sampling techniques laser ablation-ICP-MS, glow discharge-MS and spark-OES for the determination of platinum group metals in Pb buttons obtained by fire assay of platiniferous ores

This work reports on the performance of a new Pb fire assay procedure for the extraction of Au, Cu, Ir, Ni, Pd, Pt, Rh and Ru from platiniferous ores, followed by the direct analysis of the Pb buttons thus obtained by means of three solid sampling techniques (spark-OES, LA-ICP-DRC-MS and GD-sector field-MS), therefore avoiding the process of cupellation. It can be concluded that this working scheme allows the reliable analysis of different ore materials, except for Ni and Ir, for which no quantitative extraction was achieved. The preparation of the Pb buttons using large masses of the ores permitted us to obtain representative and homogeneous buttons, resulting in acceptable precision values (typically RSD values ranged between 2–5% for spark-OES and GD-MS, and between 4–10% for LA-ICP-MS), while the simple composition of these buttons (≥99% Pb) enabled the preparation of matrix-matched standards for calibration. In general terms, all these techniques perform in a satisfactory way, although they showed different strengths and weaknesses. While spark-OES provides the highest sample throughput, its detection limits are not always sufficiently low for some analytes (Au, Ir, Pt). It is demonstrated that these detection limits can be further decreased by using techniques based on mass spectrometry (LA-ICP-MS and, particularly, GD-MS), although the use of an instrumental configuration capable of dealing with spectral overlap is required, namely a dynamic reaction cell pressurized with NH3 in the case of LA-quadrupole ICP-MS and a double-focusing sector field mass analyser in the case of GD-MS.

Simultaneous square wave stripping voltammetric determination of platinum group metals (PGMs) and lead at trace and ultratrace concentration level: Application to surface water

The present work purposes two goals: to set up both a new method for simultaneously determining, at ultratrace level concentrations, Pd(II) and Rh(III) by square wave adsorption stripping voltammetry (SWAdSV), using dimethylglyoxime (DMG) as complexing agent, and a new analytical procedure for the sequential determination of Pt(II), Rh(III), Pd(II) by square wave adsorption stripping voltammetry (SWAdSV) and Pb(II) by square wave anodic stripping voltammetry (SWASV) in surface water. The critical comparison between peak area and peak current highlights once more that lower limits of detection are obtained if peak area is employed as instrumental datum. About 0.5 mol/L acetate buffer pH 3.5 + 1.8 × 10 4 mol/L dimethylglyoxime (DMG), 0.3 mol/L HCl and 0.6 mmol/L formaldehyde + 1.2 mmol/L hydrazine (formazone complex) in 0.3 mol/L HCl were employed as the supporting electrolytes. The analytical procedure was verified by the analysis of the standard reference materials: sea water BCR-CRM 403 and fresh water NIST-SRM 1643d. Precision and accuracy, expressed as relative standard deviation and relative error, respectively, were generally lower than 6% in all cases. Once set up on the standard reference materials, the analytical procedure was transferred and applied to surface water sampled in proximity to superhighway and in the Po river mouth area. A critical comparison with spectroscopic measurements is also disc used.

Determination of platinum-group metals and lead in vegetable environmental bio-monitors by voltammetric and spectroscopic techniques: critical comparison

This paper reports voltammetric sequential determination of Pt(II), Pd(II), and Rh(III), by square-wave adsorption stripping voltammetry (SWAdSV), and Pb(II), by square-wave anodic stripping voltammetry (SWASV), in vegetable environmental matrices. Analytical procedures were verified by the analysis of the standard reference materials: Olive Leaves BCR-CRM 062 and Tomato Leaves NIST-SRM 1573a. Precision and accuracy, expressed as relative standard deviation and relative error, respectively, were always less than 6% and the limits of detection (LOD) for each element were below 0.096 mug g(-1). Once set up on the standard reference materials, the analytical procedure was transferred and applied to laurel leaves sampled in proximity to a superhighway and in the Po river mouth area. A critical comparison with spectroscopic measurements is discussed.

Quantitative analysis of platinum group metals using X-ray fluorescence spectrometry

X-ray fluorescence (XRF) spectrometry was used to determine the platinum, palladium and rhodium contents in spent automotive catalyst and in two National Institute of Standard and Technology Standard Reference Materials (NIST SRMs) referred to as used auto catalysts. The XRF technique has proven to be a fast, effective and accurate method for determining not only these platinum group metals (PGM) but also other solid materials that are less soluble by wet digestion. The detection limits of XRF analyses are better than those of inductively coupled plasma mass spectrometry, which usually requires significant dilution to avoid high dissolved solid concentration. However, the XRF technique suffers from a strong matrix-dependent problem. The objective of this study was to examine the applicability of XRF for PGM analysis where the sample matrix is not exactly the same as the standard materials. This study compared the effect of various matrices, including alumina, iron, copper and nickel, on the determination of PGM.

Quantitative determination of PGM using ICP-MS, ICP-AES, AAS and XRF

The quantitative determination of platinum group metals from ore samples and industrial materials using inductively coupled plasma-mass spectrometer (ICP-MS), inductively coupled plasma-atomic emission spectrometer (ICP-AES), atomic absorption spectrometer (AAS) and X-ray fluorescence (XRF) techniques was conducted, and the performance of these techniques was compared. The ICP-AES technique exhibited better accuracy than AAS but showed limitations in its application due to strong spectral interference in the presence of common matrix elements such as iron. The ICP-MS showed the lowest detection limit and less spectral interference than the previous two techniques. The XRF technique was also applied to examine the total amount of PGM from industrial materials. Results from each analytical method on various sources were presented and discussed.

Analytical problems in the determination of platinum-group metals in urine by quadrupole and magnetic sector field inductively coupled plasma mass spectrometry

At present, there is some concern as regards the release of Pt from catalytic converters for automotive exhaust control. These catalysts, in fact, can release particulate Pt and other metals, such as Pd and Rh, into the environment through combined mechanical and thermal effects. The increasing emission of Pt-group metals has led to a growing need for suitable analytical procedures for their determination at very low levels in biological and environmental matrices. In this context, a method is described which is based on the use of a magnetic sector field inductively coupled plasma–mass spectrometry (ICP–MS) for the determination of Pd, Pt and Rh at ng l −1 levels in urine preliminarily digested by UV irradiation. Several sample pretreatment approaches were tested. The adverse effect of potentially interfering species on the mass-spectrometric determination of these metals was also taken into account. In particular, the role of other concomitants, such as Cd, Cu, Mo, Pb, Rb, Sr and Zn, was investigated in detail. The influence of such elements on the isotopes of interest, i.e. 106Pd, 195Pt and 103Rh, was quantified as apparent mean concentrations produced by the interfering elements at the expected levels in urine. These turned out to be in the 0.003–3.5 ng l −1 range. The data obtained demonstrated that the effects of 106Cd and 40Ar 66Zn on 106Pd as well as of 206Pb 2+, 87Sr 16O and 40Ar 63Cu on 103Rh cannot be disregarded. Detection limits in UV-digested and 1 : 20 diluted urine were found to be 0.25, 0.03 and 0.03 ng l −1 for 106Pd, 194Pt and 103Rh, respectively, in the low resolution mode in conjunction with ultrasonic nebulization. Repeatability of measurements was always better than 3%, while recovery data were in good agreement with the expected values. The method was tentatively applied to urine samples of 30 youngsters from the urban and suburban area of Rome. The findings allow the Pt level of these subjects to be defined at or below 1 ng l −1 and the Pd and Rh contents at ca. 10 ng l −1.