Elsevier

Microchemical Journal

Volume 76, Issues 1–2, February 2004, Pages 131-140
Microchemical Journal

Development of an analytical method for monitoring worker populations exposed to platinum-group elements

https://doi.org/10.1016/j.microc.2003.11.005Get rights and content

Abstract

The increasing industrial use of platinum-group elements (PGEs), namely Ir, Pd, Pt and Rh, and related allergies such as rhinitis, conjunctivitis, asthma, urticaria and contact dermatitis, have led to a growing need to monitor selected populations of exposed workers. In this study, the levels of PGEs were measured in indoor airborne particulate matter and in biological samples taken from employees of a plant where car catalytic converters are produced and precious metals are recovered from spent carbon catalysts. The development of an analytical procedure based on quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) for the analysis of PGEs in airborne particulate matter and on sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) for the analysis of PGEs in blood, serum, urine and hair is described. For airborne particulate matter deposited on filters, the limits of detection (LoDs) were found to be 0.006 ng m−3, 0.020 ng m−3, 0.018 ng m−3 and 0.006 ng m−3 for Ir, Pd, Pt and Rh, respectively. Repeatability of measurements ranged from 1.8 to 8.5%, while recovery was in the range from 92 to 102%. For biological samples LoDs in blood, serum, urine and hair ranged from (in ng l−1) 0.2–0.6 for Ir, 5–10 for Pd, 1–3 for Pt and 2–3 for Rh. For all biological materials, the repeatability varied from 1.1 to 12% for the four elements. Recovery data for the determination of PGEs in biological matrices were found to range from 84.0 to 107.8%. The method was applied to the determination of either total or respirable airborne PGEs collected from five different work areas in the plant. The difference between areas with high and low exposure correlates closely with metal levels in hair, blood and urine. The correlation coefficients between Pt in airborne particulate matter and Pt in biological materials was 0.994, 0.991 and 0.970 for blood, hair and urine, respectively.

Introduction

Platinum-group elements (PGEs) such as Ir, Pd, Pt and Rh belong to the transition metals group and their chemical properties are primarily inherent catalytic activity and resistance to corrosion [1]. Background levels of PGEs in the environment are very low: in airborne particulate matter their concentration is below 0.05 pg m−3, while that in road dust, sediment, soil and grass is thought to be at level of a few pg g−1 [2], [3], [4], [5]. The concentrations of PGEs in the environment have been increasing since the adoption of car catalytic converters as a consequence of their release during vehicle operation [6], [7], [8], [9]. In this context, the impact of PGEs in the workplace has raised much concern in metal-finishing industries such as catalyst manufacturing and recycling. There is thus increasing interest in investigating the levels of these metals in occupationally exposed employees.

The physiological role of PGEs is not known. Knowledge about possible adverse effects of low levels of exposure is still lacking. Hence, the risk inherent in the exposure to PGEs is still undefined. Some toxicological information about Pt is available, particularly regarding the side effects of its therapeutic use in the treatment of several types of tumors and the high-level occupational exposure to halogenated platinum salts. Diseases caused by Pt compounds in occupational environments such as refineries and catalyst-manufacturing plants are well documented. After a period of latency varying from a few weeks to several years, more than 50% of exposed workers develop hypersensitivity reactions, i.e. conjunctivitis, rhinitis, bronchial asthma, urticaria or contact dermatitis [10]. Data concerning Ir, Pd and Rh toxicity are still meager. Only a few cases have been reported in the literature of allergic contact dermatitis and contact stomatitis [11], [12], [13], [14], [15], [16].

The Italian Ministry of Health financed a project to study the allergic response caused by a new group of substances used in industry. In particular, the study aimed to (i) define the type of allergic reaction caused by PGEs; (ii) study the level of exposure in the workplace [17]; and (iii) determine the levels of metals in biological samples from exposed and unexposed subjects [18], [19], [20]. As a part of the above project, the objective of this pilot study was to develop a reliable and sensitive analytical procedure for the measurement of PGEs in the working environment and to biomonitor these metals in blood, plasma, urine and hair of exposed workers. Hair analysis, in particular, is rather advantageous, since this tissue can reflect the total body intake of certain elements better than biological fluids, even though careful evaluation of exogenous contamination is mandatory [21], [22], [23], [24].

The determination of PGEs in biological samples requires analytical techniques of adequate detection power. This poses substantial problems to the majority of instrumental analytical techniques, such as electrothermal atomization atomic absorption spectrometry (ETA-AAS), neutron activation analysis (NAA) and inductively coupled plasma emission spectrometry (ICP-AES) [25], [26], [27], [28]. In this study measurement were performed by sector field (SF) and quadrupole (Q) inductively coupled plasma-mass spectrometry (ICP-MS). These are well-established and powerful analytical techniques for the determination of trace and ultra-trace elements in environmental and biological samples. However, this technique is plagued by isobaric interference, this being a major problem in the analysis of PGEs in such matrices. Analytical methods for the determination of PGEs in airborne particulate matter and road dust, as well as in the urine of schoolboys and adults not professionally exposed, were previously reported [29], [30], [31], [32].

Section snippets

Industrial plant and production processes

The industrial plant monitored in this study is engaged in the production and recycling of PGEs and is organized in sectors in which the different stages of the production/recycling process are carried out. In the salt and solution department (SSD), salts and solutions of PGEs are used for the production of automotive catalytic converters. This department also prepares solutions of PGEs to be used in other sectors of the plant. To this end, the metals are dissolved in acid and, after

Airborne particulate samples

Of the interfering species affecting the 103Rh+ signal, the influence of 87Rb16O+ and 87Sr16O+ was negligible, probably because of the poor oxide formation in this matrix. The contributions of 40Ar63Cu+, 68Zn35Cl+, 66Zn37Cl+ and 206Pb 2+ could also be disregarded when compared with the high content of Rh in airborne particulate matter samples. The Pd determination was achieved at mass 105, where the most relevant potential interferences come from the polyatomic ions 40Ar65Cu+, 89Y16O+, 68Zn37Cl+

Conclusions

Although some of the analytical problems associated with the determination of PGEs in biological fluids of non-exposed individuals have not yet been completely solved, the data reported here clearly indicate that ICP-MS techniques are fully adequate for monitoring occupationally exposed populations. The present findings for both biological and air samples were well above the LoDs of the techniques and satisfactory control on potential mass interferences could be achieved. The overall

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