Platinum determination by inductively coupled plasma–sector field mass spectrometry (ICP–SFMS) in different matrices relevant to human biomonitoring

Abstract

The analytical challenges of Pt determination by ICP-SFMS posed by different human tissues and fluids have been critically assessed. Investigated samples were (1) urine, (2) serum of cancer patients sampled during chemotherapy with carboplatin, (3) microdialysates (20 micro L sample volume) collected from tumor and non-tumor tissue, and, finally-for the first time-(4) human lung tissue to study background concentrations of inhaled platinum. Sample preparation involved microwave digestion and open vessel treatment or simple dilution (microdialysates). Depending on the sample preparation and introduction systems used (microconcentric nebulization, ultrasonic nebulization with and without membrane desolvation) excellent procedural detection limits (3s criterion) of 0.35 pg g(-1) for urine, 420 pg g(-1) for serum, 400 pg g(-1) for lung tissue and 13 pg g(-1) for microdialysates could be obtained. Ultratrace concentrations of 1-40 pg g(-1), and 1000-3000 pg g(-1) were measured in urine and human lung tissue, respectively, as typical for samples in environmental studies. Quantification was carried out by IDMS and standard addition in the case of urine samples. Internal standardization could not correct for non-spectral interferences in external calibration. In the serum and microdialysates of patients during chemotherapy with carboplatin, elevated Pt levels ranging between 0.01 and 10 micro g g(-1) were determined by external calibration ((195)Pt isotope). For all investigated samples spectral interferences could be excluded by following different strategies. High-resolution control measurements ((194)Pt, (195)Pt) were performed in the case of elevated Pt levels, i.e. for microdialysates and serum samples. An Hf/Pt ratio of 0.4 was determined in human lung samples. An HfO formation ratio of 0.2% was assessed for standard solutions at the present experimental conditions, revealing that the contribution of (179)Hf(16)O, (178)Hf(17)O, (177)Hf(18)O to the (195)Pt isotope signal used for quantification was not significant.

The application of inductively coupled plasma mass spectrometry in clinical pharmacological oncology research

“…Oxide formation, though, can be minimized by optimizing the gas flow rate, pump rate, and ionization conditions of the plasma. Since metal oxide formation is typically controlled, via the plasma conditions, to be less than 2% and because hafnium background concentrations in biological samples are typically lower than Pt backgrounds (Rodushkin et al, 2004), hafniumoxides will not interfere significantly with Pt signals (Hann et al, 2003a). Prior to the development of an ICP-MS assay for Pt or Ru, however, background concentrations of the elements of potentially interfering metal oxides in the biological matrix should be investigated.…”

“…The methods were in agreement, indicating that no sample was lost due to volatility after dry ashing. An open vessel wet ashing procedure (HNO 3 /H 2 O 2 /HCl) was used in another study to digest urine (Hann et al, 2003a). HCl was used to provide chlorocomplexes of Pt and thereby reduce the memory effects in the sample introduction system that were observed when diluting in 1% HNO 3 (v/v).…”

“…The digestion procedure can be performed in several ways, varying from heating at high temperatures in concentrated HNO 3 (Tothill, Matheson, & Smyth, 1990;Tothill et al, 1992a,b;Minami et al, 1994;Minami, Ichii, & Okazaki, 1995;Screnci et al, 2000;Liang & Huang, 2002;Siim et al, 2003;Ghezzi et al, 2004;McDonald et al, 2005;Centerwall et al, 2006;Rice et al, 2006;Samimi et al, 2007) to more complex procedures such as digestion with concentrated HNO 3 and 30% H 2 O 2 (Ding et al, 1999;Bible et al, 2000) at elevated temperatures or microwave digestion with HNO 3 , H 2 O 2 , and HCl (Hann et al, 2003a). Perry and Balazs (1994) compared the digestion of cells with sodium hydroxide with the sonication of cells followed by digestion with concentrated HNO 3 .…”

“…Iridium and bismuth, in contrast, did show acceptable results (101-108%). Hann et al (2003a) showed that rhenium and indium did not correct for matrix suppression of Pt in digested urine. The inconsistent results point out that, when developing a new assay, it is advisable to test several ISs for each matrix.…”

“…In addition to spiking the analyte in the biological matrix (Morrison et al, 2000;Bettinelli et al, 2004;Brouwers et al, 2006Brouwers et al, , 2007cZoriy et al, 2007) some authors use alternative matrices containing the major components of the biological matrix, such as saline solutions (Nygren et al, 1990;Gamelin et al, 1997Gamelin et al, , 1998 and artificial plasma (Allain et al, 1992). Others use calibrants in water (Hann et al, 2003a) or in diluted acid (Casetta et al, 1991;Hanada et al, 1998a,b;Ding et al, 1999;Screnci et al, 2000;Yamada et al, 2005). When significant matrix effects are observed in the samples, it is, however, advisable to use matrix matched standards instead of solely water or diluted acid.…”