Methods for the Determination of Platinum Group Elements in Environmental and Biological Materials: A Review

Using HPLC for the determination of platinum drugs in biological matrixes after derivatization with diethyldithiocarbamate

Challenges and pitfalls in the application of diethyldithiocarbamate derivatization for LC analysis of cisplatin and oxaliplatin, as well as the suitability of this method for different biological matrices with implications for use in routine practice have been identified. The LC of platinum drugs presents a significant challenge. They are polar compounds with poor retention on reverse phase packings. Cisplatin also exhibits poor absorption in UV and ionization in mass spectrometry. Therefore, we developed and optimized a derivatization approach for the LC analysis of total platinum in plasma, plasma ultrafiltrate, peritoneal fluid, and urine. Derivatization in urine proved to be difficult due to the complexity of the matrix, and extended testing was required. Our results highlight the important issues affecting the efficiency, reliability, and suitability of platinum drug derivatization. Although precolumn derivatization is less selective than its postcolumn counterpart, the application of precolumn derivatization is a simple, rapid, and universal approach for the determination of platinum drugs by HPLC. One of its major advantages is that it allows a more affordable analysis using UV detection without the need for additional high-end instrumentation such as a MS detector.

A simple dilute-and-shoot procedure for the determination of platinum in human pleural effusions using HR-CS GF-AAS

BACKGROUND

High-resolution continuum source AAS is an emerging technique for the determination of trace elements in clinical analysis. We aimed to develop a method for the direct determination of platinum (Pt) in pleural effusions that could deepen the understanding of the dynamics of intrapleural Pt concentration during cytostatic therapy.

MATERIALS AND METHODS

Samples were collected by thoracic drainage from five patients with lung cancer undergoing platinum based chemotherapy. A simple dilute-and-shoot method for Pt determination in the pleural effusions was developed. Ashing of the sample in an oxygen flow in a graphite tube allowed for direct analysis without prior mineralization. The trueness of the method was verified using an independent technique (ICP-MS). As platinum derivatives are only active in its free form (not bound to proteins), Pt in samples was further divided into free and protein-bound forms by means of ultrafiltration.

RESULTS

Using the proposed method, Pt contents (free and total) were determined in samples collected at different times after the intravenous application of the Pt derivative. The concentration of total Pt reached values of up to 5,000 μg/L and different patterns of its dynamics in intrapleural fluid were observed.

CONCLUSIONS

The developed method enables the fast and simple determination of Pt in biological fluids. It may be applied on a large scale to improve the understanding of Pt dynamics during cytostatic therapy, and also to determine the optimal timing of both thoracic drainage and administration of systemic chemotherapy.

Elimination of interferences in the determination of platinum, palladium and rhodium by diffusive gradients in thin films (DGT) and inductively coupled plasma mass spectrometry (ICP MS) using selective elution

The analysis of platinum (Pt), palladium (Pd) and rhodium (Rh) in aquatic samples by the diffusive gradients in thin films (DGT) technique using chelating resins, specific designed for the accumulation of PGEs, namely Purolite S914, S920 and Italmatch Chemicals IONQUEST® MPX-317. may however, still be influenced by the accumulation of other elements such (Cu, Zn, Pb, etc.) which will be extracted simultaneously by the hot aqua regia extraction and interfere with the Inductively Coupled Plasma Mass Spectrometry (ICPMS) analysis of the Platinum Group Elements (PGEs). Selective extractions were investigated to release the interfering elements without loss of the Platinum Group Elements (PGEs) from the resin gels. . A rinse with deionized water removes over 95% of Sr and Rb and a second rinse with 0.05 mol L^-1 H₂SO₄ can be used to as a common eluent to remove an important fraction of the interfering elements from S920 and S914 without loss of PGEs but this results in loss of around 15% of the PGEs from MPX-317. It was shown that selective extractions can be used to remove specific interferences from each resin gel.

A method based on asymmetric flow field flow fractionation hyphenated to inductively coupled plasma mass spectrometry for the monitoring of platinum nanoparticles in water samples

An analytical methodology based on asymmetric flow field flow fractionation hyphenated to inductively coupled plasma mass spectrometry (AF4-ICP-MS) has been developed for monitoring citrate coated platinum nanoparticles (PtNPs) of different sizes (5, 30, and 50 nm) in water samples. Several factors have been optimized, such as carrier composition, AF4 separation program, focusing step or cross flow values. Under the optimum conditions, PtNPs can be fractionated in about 30 min in a single run with quantitative recoveries of the membrane (100 ± 7%, n = 5). The optimized method has been successfully applied to study transformations, not only in size but also surface modifications, of PtNPs in synthetic and natural water samples over time. The effect of organic matter was specifically studied, and it was found to be a critical parameter. The analytical strategy followed in this work can be very useful to develop further environmental studies involving PtNPs.

Which Metals are Green for Catalysis? Comparison of the Toxicities of Ni, Cu, Fe, Pd, Pt, Rh, and Au Salts

Environmental profiles for the selected metals were compiled on the basis of available data on their biological activities. Analysis of the profiles suggests that the concept of toxic heavy metals and safe nontoxic alternatives based on lighter metals should be re-evaluated. Comparison of the toxicological data indicates that palladium, platinum, and gold compounds, often considered heavy and toxic, may in fact be not so dangerous, whereas complexes of nickel and copper, typically assumed to be green and sustainable alternatives, may possess significant toxicities, which is also greatly affected by the solubility in water and biological fluids. It appears that the development of new catalysts and novel applications should not rely on the existing assumptions concerning toxicity/nontoxicity. Overall, the available experimental data seem insufficient for accurate evaluation of biological activity of these metals and its modulation by the ligands. Without dedicated experimental measurements for particular metal/ligand frameworks, toxicity should not be used as a "selling point" when describing new catalysts.

Active biomonitoring of palladium, platinum, and rhodium emissions from road traffic using transplanted moss

The use of transplanted moss (Pleurozium schreberi) in active biomonitoring of traffic-related emissions of Pd, Pt, and Rh was studied. Moss mats were transplanted to three locations along highway E75 (in Oulu, Finland) at three different distances from the highway. Five samples were collected from a background site after the same exposure period. Mass fractions of Pd, Pt, and Rh as well as mass fractions of 18 other elements were determined in these samples. The results indicated that P. schreberi is well suited for active biomonitoring of Pd, Pt, and Rh. Mass fractions above the background values were observed in the samples exposed to traffic-related emissions. When the results were compared with those of the other elements, high correlations of Pd, Pt, and Rh with commonly traffic-related elements (e.g., Cu, Ni, Sb, Zn, etc.) were found. It was also found that the amounts of Pd, Pt, and Rh in moss samples decreased when the distance to the highway increased. This trend gives evidence for the suitability of P. schreberi for active biomonitoring of Pd, Pt, and Rh. Furthermore, it can be concluded that the mass fractions determined in this study provide valuable evidence about the current state of Pd, Pt, and Rh emissions in Oulu, Finland.

Extraction and pre-concentration of platinum and palladium from microwave-digested road dust via ion exchanging mesoporous silica microparticles prior to their quantification by quadrupole ICP-MS

We report on the use of mesoporous silica microparticles (μPs) functionalized with quarternary amino groups for the isolation of platinum and palladium tetrachloro complexes from aqueous road dust digests. The μPs have a size ranging from 450 to 850 nm and are suspended directly in the aqueous digests, upon which the anionic Pt and Pd complexes are retained on the cationic surface. Subsequently, the μPs are separated by centrifugation. Elements that cause spectral interferences in ICP-MS determination of Pt and Pd can be quantitatively removed by adding fresh 0.240 mol L⁻¹ HCl to the μPs and by repeating the centrifugation step. The analyte-loaded μPs are then dissolved in 0.1 mL of 2 mol L⁻¹ HF, diluted to 2 mL, and the solutions thus obtained are analyzed by quadrupole ICP-MS. This method avoids analyte elution from the sorbent. This “dispersed particle extraction” approach yielded a run-to-run relative standard deviation ≤ 5 % for Pt and ≤ 4 % for Pd (at 0.1 ng mL⁻¹, n = 4 road dust digests). Method detection limits (expressed as concentrations in the dust samples) are 2 and 1 ng g⁻¹ for Pt and Pd, respectively. The method was validated by analysis of a reference material (BCR CRM 723) and applied to the analysis of road dust samples collected in downtown Vienna. Pt and Pd concentrations in samples collected in summer and in winter were compared, with concentrations ranging from 205 to 1445 ng g⁻¹ for Pt and from 201 to 1230 ng g⁻¹ for Pd.

Graphical Abstract

Catalytic C-C and C-heteroatom bond formation reactions: in situ generated or preformed catalysts? Complicated mechanistic picture behind well-known experimental procedures

In situ generated catalysts and preformed catalysts are two practical strategies widely used in cross-coupling methodology that have long been considered to involve the same active species in the catalytic cycle. Recent mechanistic studies have revealed two fundamentally different pictures of catalytic reactions in solution. Preformed catalysts with strongly bound ligands initiate transformations mainly involving single type of metal species. In contrast, in situ generated catalysts give rise to cocktail-type systems with different metal species presented in solution. The role of catalyst precursor, interconversions of catalytic species during reaction, stability and recycling of catalyst, catalysis by autocatalyst exhaust and plausible sources of metal-containing contaminants are the key points discussed in this review.

Speciation of platinum-benzoylthiourea in the gas phase using electrospray ionization mass spectrometry and density functional theory

RATIONALE

Determining the speciation of platinum-benzoylthiourea (Pt-BTU) in the gas phase is a challenging task due to various reaction pathways and the conformational flexibility of the BTU ligand.

METHODS

Electrospray ionization mass spectrometry (ESI-MS) experiments and density functional theory (DFT) based calculations were carried out to shed light on this complex reaction in the gas phase using K2 PtCl4 salt and BTU. Various Pt complexes were studied in both positive and negative ion modes of ESI-MS using a quadrupole-time-of-flight mass spectrometer. The effects of the ESI-MS experimental parameters such as capillary voltage, pH and electrolyte on the peak intensity of the Pt-BTU complex were investigated. DFT calculations employing B3LYP functional with the 6-311++G** basis set were used to characterize the geometric parameters and fragmentation patterns of various Pt complexes in the gas phase.

RESULTS

In the positive ion mode, complexes with differing numbers of BTU ligands coordinated to the metal ion were observed, whereas, in the negative ion mode, no species associated with BTU or with the solvent (acetonitrile) molecules were found. It was also found that Pt forms complexes with the BTU ligand in different stoichiometric ratios. For both Pt(BTU)2 and Pt(BTU)3 complexes, the BTU ligand undergoes deprotonation followed by bi-dentate coordination. DFT calculations suggest that BTU can coordinate to Pt in both cis and trans isomeric forms, which are nearly iso-energetic with a slight preference towards the trans-isomer. The preference of trans-BTU binding is attributed to the exclusive retention of intra-molecular hydrogen bonding which is absent in the cis-form.

CONCLUSIONS

Experimental and theoretical calculations have shown that the gas-phase interaction of BTU to Pt is very complex. The BTU ligand can coordinate to Pt in both mono-dentate and bi-dentate modes, the latter mode being favorable upon deprotonation of the BTU ligand. Furthermore, many close lying species with different geometric isomeric forms are found to be possible due to the presence of intra- and inter-molecular hydrogen bonding.