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- RESULTS AND DISCUSSION
In recent years the increasing use of platinum (Pt) both in medical and in industrial applications has caused its growing anthropogenic emission and spread in the environment. Pt is released into the atmosphere by exhaust catalytic converters, and Pt compounds are often used in antitumour therapies. As a consequence, significant amounts of Pt can be detected in hospital wastewaters. This can lead to an increase in the exposure levels to Pt, especially in urban areas. It is therefore necessary to determine Pt reference values in the general population, by using suitable procedures able to achieve adequate analytical performances. Several measurements of Pt in biological fluids have been reported, but the analytical methods used for the determination of Pt often lack information about the uncertainty of the results, especially for low concentrations of urinary Pt in non-occupationally exposed subjects. The present paper considers the measurement of urinary Pt levels in a general population group from central Italy, by both quadrupole (Q) and sector field (SF) inductively coupled plasma mass spectrometry (ICP-MS). The two procedures were validated and their expanded uncertainties were evaluated. The limits of detection (LODs), calculated taking into account dilution factors, were 0.18 and 0.05 ng L−1 of Pt for the Q and SF procedures, respectively. The median value observed was 4.13 ng L−1 of Pt in urine, while the relative combined uncertainty at 5 ng L−1 was below 20% with both ICP-MS techniques. These data are in good agreement with those reported in the literature for similar studies. Copyright © 2005 John Wiley & Sons, Ltd.
The use and diffusion of platinum in the environment have increased rapidly in recent years, both in the medical and in the industrial field. Platinum is widely used in the antineoplastic chemotherapy of several tumours, such as lung, cervical, testicular, head, neck ovarian and bladder carcinomas.1, 2 The resulting excretion of Pt compounds by treated patients leads to not negligible concentrations of Pt in wastewaters, and then in the environment.3 In addition, modern three-way automotive catalysts, which abate the emission of NOx, CO and aromatic hydrocarbons, typically contain high concentrations of Pt group elements (PGEs) and, thus, can be considered as the main sources of Pt dispersion.4–6 Many studies have reported high Pt concentration in airborne particulate,7, 8 in sewage sludges,9 and in road dust,6 thus raising concern about potential harmful consequences on humans.
The most efficient way to monitor and evaluate the real incidence of this exposure is to determine the reference value (RV) of Pt in the urine of the general population.10 The assessment of the RV of Pt in biological fluids is a difficult task for analytical laboratories, due to the low levels at which the metal is present, requiring adequate detection limits, careful and minimal manipulation of the samples, and effective control of pre-analytical factors in order to assure low levels of blanks.11
The determination of Pt in biological fluids is performed by means of different inductively coupled plasma mass spectrometry (ICP-MS) techniques, i.e., quadrupole (Q), sector field (SF) and instruments with dynamic cell reaction (Q-DRC), and related hyphenated techniques,12–15 although some alternative procedures like voltammetry,16 ETAAS with on-line pre-concentration,17 and ICP-OES18 have also been investigated.
There is considerable experimental data on the Pt concentrations in biological fluids available in the literature, but very few studies have involved a robust evaluation of the analytical performance, in terms of assessment of the measurement uncertainty. It is now, however, generally acknowledged that the fitness of analytical data cannot be assessed without some estimation of the measurement uncertainty to be compared with the required confidence levels. It is thus necessary to identify all the possible sources of uncertainty arising from the adopted procedure, to define their magnitude, and to combine their estimations to give standard and expanded uncertainties.
This is particularly important when trace or ultra-trace elements have to be assessed as RVs. At low level it is important to establish if a procedure is able to give satisfactory results, i.e., which is the lower difference between two samples that the procedure is able to distinguish. From this point of view, overall uncertainties higher than 50% seem to be unacceptable.
In a previous study19 the assessment of the measurement uncertainty was applied to validate the method of Pt quantification in fluids of patients treated with antitumour agents. The same approach has been adopted here for comparing the performances of two analytical procedures involving different ICP-MS techniques, namely the Q and SF systems, in the determination of Pt in the urine of selected healthy subjects. The tentative RVs for urinary Pt of a general population group from a central region of Italy were also calculated.
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- RESULTS AND DISCUSSION
The analytical performances of two ICP-MS procedures for the quantification of Pt in urine showed a good agreement, in terms of accuracy and precision, between the two sets of data, and confirmed that ICP-MS techniques are suitable for monitoring the general population. Moreover, both techniques gave adequate LODs and overall uncertainties associated with the measurements.
The procedures, when applied to the evaluation of Pt in urine of 50 subjects from a central region of Italy, gave the median value of 4.13 ng L−1, with minimum and maximum values equal to 1.20 and 27.3 ng L−1, respectively.
This study will continue, as a correlation between the information collated on the study subjects' lifestyle and dietary habits and their urinary Pt levels was outside of the scope of this study.