M. A. Palacios

ICP-MS determination of Pt, Pd and Rh in airborne and road dust after tellurium coprecipitation

A method has been developed for the simultaneous determination of Pd, Pt and Rh (PGE) in environmental airborne and road dust samples by tellurium coprecipitation and ICP-MS. The Te coprecipitation was applied after digestion of the sample with aqua regia–HF in a microwave oven. This separation method removes more than 95% of the elements producing mass interference in PGE determination by ICP-MS. The methodology was validated with reference road dust samples CW7 and CW8. The detection limits are 0.3, 0.6 and 0.8 pg m−3 for Pt, Pd and Rh in airborne particulate matter, and 1, 1 and 0.4 ng g−1 for Pt, Pd and Rh in road dust. Application of the isotopic dilution method for Pt and Pd after their coprecipitation improves the results obtained for road dust samples. Rh (monoisotopic element) analysis was carried out by external calibration after Te coprecipitation.

On line speciation of Se(VI), Se(IV), and trimethylselenium by HPLC-microwave oven-hydride generation-atomic absorption spectrometry

An on-line system is proposed consisting of an anion-exchange chromatographic column, microwave-induced thermooxidation of trimethylselenium in the presence of persulphate, and microwave-induced thermoreduction of Se(VI) to Se(IV) in HCl medium, followed by hydride generation and atomic absorption for the determination of trimethylselenium (TMeSe), Se(IV) and Se(VI). Trimethylselenium is eluted in the dead volume of an anion-exchange column (Hamilton PRP-X-100), before elution of Se(IV) and Se(VI). Optimum chromatographic conditions have been obtained using 100 mmol L−1 phosphate buffer (pH=6.8) H2PO4−/HPO42−as the mobile phase. Recoveries were around 100%, absolute detection limits were 1.1, 1.4 and 2.2 ng for TMeSe, Se(IV) and Se(VI), respectively. Precision was lower than 10% in all cases. The method has been applied to tap water.

On-line preconcentration and determination of trace platinum by flow-injection atomic absorption spectrometry

The analytical performance of a platinum preconcentration method using a 0.01 M HNO3 carrier solution and an alumina microcolumn is discussed. On-line preconcentration is followed by flame atomic absorption spectrometry (FAAS), and off-line preconcentration by graphite furnace atomic absorption spectrometry (GFAAS). The preconcentration factors were 600 for FAAS (25 μl elution volume) and 30 for GFAAS (500 μl elution volume), both with a 15-ml sampling volume. The detection limits in these conditions were 0.02 mg l−1, and relative standard deviation (R.S.D.) of 9% (0.1 mg l−1 solution, n = 5) for FAAS and 0.33 μg l−1, and a R.S.D. of 7% (5 μg l−1 solution n = 5) for GFAAS. The proposed method is suitable for platinum determination in natural water samples.

Stability studies of arsenate, monomethylarsonate, dimethylarsinate, arsenobetaine and arsenocholine in deionized water, urine and clean-up dry residue from urine samples and determination by liquid chromatography with microwave-assisted oxidation-hydride generation atomic absorption spectrometric detection

Abstract The stability of arsenate, monomethylarsonate, dimethylarsinate (DMA), arsenobetaine (AsB) and arsenocholine (AsC) at a concentration of 200 μg l −1 in deionized water, urine and dry clean-up residue of urine, stored in dark at −20 °C, 4 °C and ambient temperature, without the addition of any stabilizer reagent was evaluated. The five species were determined independently by liquid chromatography with microwave-assisted oxidation-hydride generation atomic absorption spectrometric detection. At −20 °C, all species were stable in water and untreated urine; at 4 °C and ambient temperature, they were stable during the 67 days of testing in the urine dry residue after the clean-up procedure. In untreated urine samples at 4 °C and ambient temperature, AsC is unstable and easily transformed to the more oxidized species, AsB. In deionized water, AsB and AsC are transformed to other species such as DMA. The dry urine residue may be a good matrix as a reference material for As species.

Determination of six arsenic species by high-performance liquid chromatography — hydride generation — atomic absorption spectrometry with on-line thermo-oxidation

SummaryAnion-exchange HPLC has been coupled to on-line thermo-oxidation and hydride generation-atomic absorption spectrometry (HG-AAS) for the speciation of As(V), As(III), MMA, DMA, AsB and AsC. The thermoreactor consists of a loop of PTFE tubing dipped in a powdered-graphite oven heated to +140°C. Samples and persulphate solution run together into the thermo-reactor. The thermo-oxidation conditions were optimized using a FIA system. The chromatographic and chemical parameters affecting hydride generation efficiency were optimized. The overlap of the As(III) and AsB peaks made it necessary to determine AsB as the difference between absorbance in the presence and in the absence of thermo-oxidation. The thermo-conversion efficiencies were above 96%. Recoveries were around 100% and detection limits below 1 ng. The proposed method is rapid, sensitive and precise (RSD about 5%), making it suitable for on-line determination in environmental samples.

Atomic (HPLC-ICP-MS) and molecular mass spectrometry (ESI-Q-TOF) to study cis-platin interactions with serum proteins

The judicious use of cis-Pt as an intravenously administrable Pt(II) drug for chemotherapy requires the evaluation of its interactions with blood proteins. Therefore, the combined use of modern analytical chemical speciation and of analytical proteomics approaches to study these interactions is described here. The method involves incubation of cis-Pt with standard proteins and human serum samples. The separation of the proteins is conducted by liquid chromatography in an anion exchange column (Mono Q). Simultaneous molecular detection by UV absorption (280 nm) and elemental detection (195Pt) using inductively coupled plasma mass spectrometry (ICP-MS) are performed. Using this set-up, the effects of the incubation time as well as the drug concentration on cis-Pt interactions with transferrin, albumin and innmunoglobulin G were studied. In addition, the nature of interactions was also investigated by means of electrospray mass spectrometry (ESI-Q-TOF) of the intact protein. Transferrin and albumin showed different interactions, binding one and four cisplatin molecules, respectively. Also, some typical proteomic studies were initiated by tryptic digesting the transferrin and albumin cis-Pt complexes followed by capillary-LC-ICP-MS and ESI-Q-TOF parallel detection of the peptides obtained. The capLC-ICP-MS chromatogram provided clear evidence of Pt-containing peptides remaining after tryptic digestion.

Preconcentration of inorganic selenium species (Se (IV) and Se (VI)) in an alumina filled microcolumn and on-line determination by hydride generation atomic absorption spectrometry

A flow injection system has been developed consisting of on-line preconcentration of selenium species in a microcolumn filled with activated alumina, reduction of Se(VI) to Se(IV) and determination by HG-AAS. When 0.01 mol/L HNO3 is used both as carrier and activation reagent for the alumina microcolumn, up to 150 ng of Se(IV) and Se(VI) can be preconcentrated and quantitatively eluted by 500 μL of 2 mol/L NH3. The preconcentration factor is 50 when 25 mL of sample is used. The detection limit is about 6 ng/L, the precision is 5% for low concentrations such as 150 ng/L and 3% at high concentrations such as 120 ng/mL. The proposed method is suitable for natural water samples and inorganic Se speciation can be performed by determining Se(IV) and total selenium [Se(VI) is evaluated from the difference].

SEC-ICP-MS and ESI-MS as tools to study the interaction between cisplatin and cytosolic biomolecules

Most of cisplatin’s citotoxic properties are due to the interaction of the drug with DNA. However, other biological molecules present in the cell cytosol, such as MT (metallothionein) and GSH (glutathione), are potential targets for cisplatin and have been related to its side-effects or with the cellular resistance mechanisms to the drug. Experiments simulating physiological conditions have been performed to study the specific cisplatin metabolites which interact with GSH and MT and to characterize the different drug–biomolecule adducts over time. A combination of size exclusion chromatography-inductively coupled plasma mass spectrometry (SEC-ICP-MS) and electrospray ionization-mass spectrometry (ESI-MS) techniques has been used to provide sensible multi-elemental detection and structural information of the species of interest. Time dependent transformation of 10 μM cisplatin at neutral pH (7.4) produces different concentrations of the mono-aquo and oligomeric derivatives, as could be confirmed by ESI-MS. No di-aquo derivative was seen to be produced under these conditions at any of the incubation times used. Cisplatin and the oligomeric derivative were incubated with GSH and MT at different drug:biomolecule ratios. Adducts from cisplatin–GSH (1:500) and from cisplatin–MT (1:10) incubations were characterized by SEC-ICP-MS. While both GSH and MT reacted with cisplatin producing different compounds, only GSH reacted with the oligomeric derivative of cisplatin. SEC-ICP-MS experiments showed that, under neutral pH conditions, Cd atoms remained bound to the cisplatin:MT adducts, but Zn atoms were lost. Results were compared with those obtained by in vitro and in vivo experiments with rat kidney, liver and inner ear cytosols.

Evaluation of high-performance liquid chromatography for the separation and determination of arsenic species by on-line high-performance liquid chromatographic-hydride generation-atomic absorption spectrometry.

An on-line high-performance liquid chromatographic-microwave assisted oxidation-hydride generation-atomic absorption spectrometric (HG-AAS) system (using columns of different kinds) has been developed for the determination of arsenite, arsenate, dimethylarsinate (DMA), monomethylarsonate (MMA), arsenobetaine (AsB) and arsenocholine (AsC) in environmental samples. Ion-pair reversed-phase chromatography using tetrabutylammonium phosphate as the ion-pair reagent and anion-exchange chromatography were evaluated and the analytical performances of each are reported. The detection limits were 97-143 and 10-30 micrograms l-1 for ion-pair reversed-phase and anion-exchange chromatography, respectively. The Hamilton PRP-X 100 anionic column was proposed for the determination of the six species; AsB can be quantitated independently of AsC by taking the difference between readings at pH 6 and pH 10.7. The proposed methods were applied to water samples and sediments and their potential for future application was demonstrated.

An approach to the arsenic status in cardiovascular tissues of patients with coronary heart disease

Among non-cancer effects of arsenic, cardiovascular diseases have been well documented; however, few are known about the arsenic fate in cardiovascular tissues. We studied the analytic bioinorganic arsenic behaviour in cardiovascular tissues from an arsenic exposure coronary heart disease patient group from Antofagasta-Chile against a small unexposed arsenic coronary heart patient group. Total arsenic concentrations were measured in pieces of cardiovascular tissues of the arsenic-exposed and unexposed coronary heart patient groups by hydride generation atomic absorption spectrometry (HG-AAS); speciation analysis was made by high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). Pieces of auricle (AU), mammary artery (MAM), saphenous vein (SAP) and fat residuals (FAT) were considered in this study. The arsenic concentrations in AU and MAM tissues were significantly different between both groups of patients. Also, it was demonstrated that the AU is an ‘As3+ target tissue.’ Otherwise, linking of the total concentrations of arsenic with conditional variables and variables related to medical geology factors allowed us to infer that the latter are more important for the cardiovascular risk of arsenic exposure in the Antofagasta region. Knowledge of total arsenic and the prevalence of the trivalent ion (As3+) in the AU of patients could contribute to understanding the effect of arsenic on cardiovascular diseases.