1,721,042 research outputs found
Voltammetric and spectroscopic methods for the ruthenium determination in the environment at ultra-trace concentration level: critical comparison and application to airborne particulate matter, vegetables, superficial waters, mussels, clams and soils
No full textThe problem related to the presence of Platinum Group Metals (PGMs) in the environment has raised much attention and great interest in the scientific community. This is due to the fact that the PGMs are widely used in various fields, such as anticancer drugs, jewels production, photographic operations, industrial catalysts, and especially autocatalytic converters. In the last case, their continuous use and deterioration implies a considerable release of these metals in the environment. It should be noted that the metals initially used in autocatalytic converters were platinum, palladium and rhodium, but in recent years such PGMs were gradually and partially replaced, or alloyed with osmium and especially ruthenium. Their addition in the manufacture of autocatalytic converters helps them withstand high temperatures and wear, thus increasing the product life. Thus, the increasing use of autocatalytic converters shows two decidedly conflictual effects on the environment: an evident and drastic reduction of the concentration levels of lead, and, at the same time, an equally evident and widespread increase of the PGMs concentration, and in particular of ruthenium, due to its increasing use in recent years. This work proposes a voltammetric method for the determination of ultra-trace ruthenium in environmental samples: airborne particulate matter, vegetables, superficial waters, mussels, clams and soils/sediments. To better validate the proposed analytical procedure, a critical comparison with spectroscopic measurements - electrothermal atomic absorption spectroscopy (ET- AAS) because of its well established and tested robustness - has been also carried out and discussed here. All the parameters of interest for the set-up of an analytical method, such as trueness and precision (accuracy), limit of detection and quantification, selectivity and, especially, sensitivity were taken into account
Iridium, the new and more recent polluting metal linked to vehicular traffic. its determination in airborne particulate matter, superficial waters, soils/sediments, vegetables, mussels, clams and algae by voltammetry and spectroscopy: critical comparison
No full textRecently, the problem relevant to the increasing presence in the environment of platinum group metals (PGMs) have been a topical subject of great interest, even if the scientific attention has been generally addressed to platinum(II), palladium(II) and rhodium(III), and in few cases to iridium(III), osmium(VIII) and ruthenium(III). This is because the PGMs concentration is significantly growing as a consequence of their increasing use in the production of industrial catalysts, anticancer drugs, jewels, and especially autocatalytic converters. In the case of the last tools, their continuous incorrect use “stop and go” with consequent deterioration implies a considerable release of these metals in the environment.
Even if initially the metals used in autocatalytic converters were platinum, palladium and rhodium, in recent years such PGMs were gradually replaced in part, or alloyed with osmium, ruthenium and, especially, iridium. In particular, in the last decade, and always more frequently, iridium is employed as alloying (10-20 % w/w) with platinum, palladium and rhodium in the manufacture of autocatalytic converters in order to withstand high temperature and high wear.
Finally, it is also important to highlight that iridium is one of the least abundant elements in the environment, and, probably for this reason, very few data are available.
Thus, this work intends to propose voltammetric methods for the determination of ultra-trace iridium in environmental samples: airborne particulate matter, superficial waters, soils/sediments, vegetables, mussels, clams and algae.
To better validate the proposed analytical procedures, a critical comparison with spectroscopic measurements — electro-thermal atomic absorption spectroscopy (ET–AAS) because of its well established and tested robustness — has been also carried out and discussed here, taking into account all the parameters of interest to set-up an analytical method, such as precision, trueness, limit of detection and quantification, selectivity and, especially, sensitivity
Voltammetric determination of metals as food contaminants: an excellent alternative to spectroscopic measurements. application to meals, vegetables, mussels, clams and fishes
No full textThe work regards the voltammetric determination of trace metals in different kinds of food matrices.
First goal is relevant to the correct analytical procedure for the voltammetric determination of trace and ultra-trace metals - Platinum Group Metals (PGMs), Mercury (II), Copper (II), Lead (II), Cadmium (II) and Zinc (II) - in meals, vegetables, mussels, clams and fishes: this allows, evidently, to check high quality foodstuffs.
The second goal is to show the advantages that the electrochemical approach may offer over atomic absorption spectroscopy. First, voltammetry, together with the standard addition method, is a valid analytical technique (good selectivity and, especially sensitivity) for the simultaneous element determination in complex matrices and it does not require enrichment steps, like solvent extraction, and/or particular sample treatments. Second, as regards precision, accuracy and limits of detection, the results obtained with the two techniques are both good and comparable in all cases, although voltammetry is better than atomic absorption spectroscopy, allowing simultaneous metal determinations in most cases. In fact, also Inductively Coupled Plasma (ICP) and Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) permit multi-element determination, but the great advantage in using voltammetry is certainly the equipment-related costs: very low in the case of voltammetry, extremely high in the case of ICP and ICP-MS, in the latter case as much as 25-30 times higher.
In this work Electrothermal Atomic Absorption Spectroscopy (ETAAS) was also chosen as comparison technique because of its well-established and tested robustness
Ultra-trace heavy metal determination in sea food by differential pulse catalytic voltammetry: application to fishes and bivalve molluscs
No full textThe paper proposes an analytical procedure regarding the voltammetric determination of chromium(VI), copper(II), lead(II), cadmium(II), zinc(II) and mercury(II) by differential pulse catalytic voltammetry (DPCV) in matrices involved in the food chain, but also employed as possible biological monitors for trace metal.
The digestion of each matrix was carried out using a concentrated HCl-HNO3-H2SO4 acidic attack mixture.
0.23 mol L-1 dibasic ammonium tartrate buffer pH 4.9 + 5.9x10-2 mol L-1 NaBrO3 was employed as the supporting electrolyte. The voltammetric measurements were carried out using, as working electrodes, a stationary hanging mercury drop electrode (HMDE) [simultaneous determination of Cr(VI), Cu(II), Pb(II), Cd(II) and Zn(II)] and a gold electrode (GE) [determination of Hg(II)], a platinum electrode and Ag⎪AgCl⎪KClsat electrode as auxiliary and reference electrodes, respectively. The analytical procedure has been verified on the standard reference materials Mussel Tissue BCR-CRM 278 and Cod Muscle BCRCRM
422. For all the elements in the certified matrices, the precision as repeatability, expressed as relative standard deviation (sr) was lower than 6 %, while the trueness, expressed as relative error (e) was of the order of 5-6 %. Once set up on the standard reference materials, the analytical procedure was transferred and applied to fishes and molluscs sampled in the Po river mouth area
Thallium: A Polluting Metal of New Generation. Its Voltammetric Determination in Herbal Medicines in Presence of Metal Interferences
Full text linkThe present paper reports a new application: the voltammetric determination in herbal medicines of ultra-trace thallium(I), in the presence of lead(II), tin(II) and antimony(III) as interfering metals, by square wave anodic stripping voltammetry (SWASV). A conventional three-electrodes voltammetric cell was employed with a stationary hanging mercury drop electrode (HMDE) as working electrode and a platinum electrode and an Ag|AgCl|KClsatd. electrode as auxiliary and reference electrodes, respectively. The supporting electrolyte was 0.5 mol L−1 ammonium citrate buffer pH 6.5 + 7.3·10−3 mol L−1 EDTA-Na2. The analytical procedure was verified by the analysis of the standard reference materials: spinach Leaves NIST-SRM 1570a and tomato leaves NIST-SRM 1573a from National Institute of Standards and Technology. Precision and trueness, expressed as relative standard deviation and relative error, respectively, were generally lower than 7% in all cases. Once set up on the standard reference materials, the analytical procedure was transferred and applied to herbal medicines samples—Taraxacun officinale weber, Eucalyptus globulus and Harpagophytum procumbens DC—sold on the market. A critical comparison with spectroscopic measurements is also discussed
Determination of emerging metal pollutants and toxic metals in mussels and bivalve mollusks, very important food and environmental bio-monitoring species
No full textA quick and widespread diffusion of heavy metals as contaminants in all the environmental systems has called the attention to their determination. Indeed, heavy metals, together with pesticides, are very dangerous pollutants owing to their bioaccumulation and toxicity. It is, therefore, necessary to determine these metals at trace and ultra-trace level especially in aquatic ecosystems to establish reasonable water quality criteria. Certain marine species, in particular mussels, clams, but also oysters accumulate toxic metals, being filtering organisms. It was verified that an adult organism is able to filter several liters per hours (also up to 4-5 L h-1), depending on its weight. This prerogative involves two important facts and consequences: 1. The ability to accumulate all harmful substances for humans, toxic metals, in particular, requires particular attention and inspections before being sold on the market. 2. In addition to this important and fundamental aspect of public health, the determination of toxic metals in mussels, clams and also oysters, that are not only filtering organisms but also sessile species, can be usefully employed for bio-monitoring campaigns, that evaluate the long-term trend of the pollution load of an aquatic ecosystem, information that evidently cannot be provided by punctual determinations. For completely mapping environmental pollution, the sampling duration and cadence are very important. However, it should be emphasized that the use of bio-monitors, just proposed by several authors, but certainly not scientifically supported, is possible only in the case of a long sampling plan. In any case, the metal determination in mussels and bivalve mollusks evidently must be accurate, reproducible and especially it must show very low limits of detection. The present work reports and discusses the different analytical methodologies for the determination of emerging metals pollutants, together with all toxic metals, in mussels, clams, and oysters
ANALYTICAL METHODS FOR ORGANIC AND INORGANIC TOXICS DETERMINATION IN COSMETICS PRODUCTS
No full textThe widespread use has made preservatives become a special monitored group in commercial cosmetics, especially in the leave-on products due to the prolonged exposure.
Additionally, recently there has been an increase in the demand for preservative-free cosmetics related to undesired adverse effects on human health, in order to minimize the amount in personal care products or produce preservative-free-cosmetics and verify the contents to avoid health risk.
Hence, the simultaneous separation and trace-level determination in personal care products are important for both merchandise reliability and quality assurance.
However, is not possible to exclude that heavy metals can be accumulated in the body over time and repetitive metal-containing product application can lead to significant exposure levels.
In the case of some metallic powders such as nickel (Ni), lead (Pb), and cadmium (Cd), they are unintentionally added to the cosmetics as impurities during manufacturing of an ingredient or product, and represent a minor source of exposure compared to other pathways such as water, food or air.
For these reasons it is necessary a deep knowledge of real toxics (organic and inorganic) content into personal care products and cosmetics using reliable, high-throughput, sensitive and selective analytical assays.
In this chapter, recently developed method for the extraction, separation, and quantitative determination of organic (phthalates and parabens) and inorganic toxic (heavy metals) in cosmetic products are reported
Square wave catalytic adsorptive voltammetric determination of osmium, ruthenium and lead in vegetable environmental bio-monitors
No full textThe present work regards the simultaneous voltammetric determination of Os(VIII), Ru(III) and Pb(II) by square wave catalytic adsorptive voltammetry (SWCAdV) in vegetable environmental bio-monitor matrices. The analytical procedure was verified by the analysis of the standard reference materials: Olive Leaves BCR-CRM 062 and Tomato Leaves NIST-SRM 1573a. Precision and accuracy, expressed as relative standard deviation and relative error, respectively, were generally lower than 6% in all cases, whereas the limits of detection for all elements were lower than 5.0 μg kg-1. Once set up on the standard reference materials, the analytical procedure was transferred and applied to laurel leaves sampled in proximity to superhighway and in the Po river mouth area. A critical comparison with spectroscopic measurements is discussed
Metals
No full textSummary
1. Introduction
2. Analytical Procedure for the Metal Determination
2.1 Sampling
2.2 Sample Dissolution - Destruction of Organic Matter
2.2.1 Wet Ashing
2.2.2 Dry Ashing
2.2.3 Fusion
2.3 Separation and Concentration Methods
2.4 Laboratory Contamination
2.5 Instrumental Determination Methods
2.5.1 Electroanalytical Techniques
2.5.2 Spectrometric Methods
2.5.3 Other Techniques
3. Metals of Interest
3.1 Mercury
3.2 Patinum Group Metals (PGMs)
3.3 Miscellanea
4. Directives for Trace Metals in Food
5. Reference
Chemometrics for the Direct Analysis of Solid Samples by Spectroscopic and Chromatographic Techniques
No full textThe direct chemical analysis allows investigating samples without altering them, keeping the sample available for further analysis. For the qualitative investigation, analytical procedures like gas-chromatography, Raman microscopy, and Infra Red spectroscopy are available; however, the univariate approach is not exhaustive in the case of very complex matrices. The quantitative approach is still an open issue, due to the strong matrix effect hindering the creation of univariate calibration methods in interpolation mode. The multivariate analysis may be the solution.
Three-way Principal Components Analysis (PCA) allows for comprehension of variables influencing classification. The Partial Least Squares regression (PLS) combined with Discriminant Analysis (DA) allows classifying. Multivariate standard addition calibration based on PLS coupled with Net Analyte Signal (NAS) calculation allows bypassing the matrix effect in quantitative analysis.
This Chapter is focused on the issues mentioned above. Three sections will be presented:
SECTION 1: three-way PCA is applied to the discrimination among bacterial species in samples analyzed as such by pyrolysis gas chromatography-mass spectrometry. Applications to timely analysis of pathogenic microbes are foreseen.
SECTION 2: PLS-DA is applied to Raman spectra to discriminate adulterated beeswaxes from natural ones. This procedure may be implemented to prevent possible adulteration of bees’ products.
SECTION 3: PLS-NAS is applied to ATR spectra to quantify biogenic silica in marine sediments. The new method allows to accurately study the time evolution of primary productivity in the Antarctic basins
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