Factorial design for multivariate optimization of an on-line preconcentration system for platinum determination by ultrasonic nebulization coupled to inductively coupled plasma optical emission spectrometry

A system for on-line preconcentration and determination of platinum by ultrasonic nebulization (USN) coupled to inductively coupled plasma optical emission spectrometry (ICP-OES) was studied. It is based on the chemical sorption of platinum on a column packed with polyurethane foam loaded with thiocyanate reagent. The optimization step was carried out using two level full factorial design. Three variables (pH, loading flow rate (LFR) and eluent concentration) were regarded as factors in the optimization. Results of the two level factorial design 2³ with three replicates of the central point for platinum preconcentration, based on the variance analysis (ANOVA), demonstrated that the factors and their interactions are not statistically significant. The proposed procedure allowed the determination of platinum with a detection limit of 0.28 μg l⁻¹. The precision for 10 replicate determinations at 10.0 μg l⁻¹ Pt level was 3.8% relative standard deviation (R.S.D.), calculated from the peak heights obtained. A total enhancement factor of 100 was obtained with respect to ICP-OES using pneumatic nebulization (10 for USN and 10 for preconcentration). A sampling frequency of 50 samples per hour was obtained. The effect of other ions in concentrations agreeing with water samples was studied. The addition/recovery experiments in the samples analyzed demonstrated the accuracy and applicability of the system developed for platinum determination in spiked water samples.     

Quantitative determination of wear metals in engine oils using LIBS: The use of paper substrates and a comparison between single- and double-pulse LIBS

A comparison between single- and double-pulse LIBS for the quantitative elemental analysis of used engine oils has been performed. Paper substrates have been utilised for the analysis and are shown to provide better limits of detection (LODs), no splashing and easier sample handling compared to the previously reported experiments using laminar liquid jets and static liquid surfaces. Single-pulse LIBS analysis of oil on paper substrates has had on average 2× better LODs than was obtained using flowing liquid jets, while double-pulse LIBS showed 4× improvement. Single-pulse LIBS has been found preferable for the analysis, as the use of an additional laser in double-pulse LIBS yielded only a minor improvement while adding substantially to the complexity and cost of the system.     

Sorption of platinum on immobilized microorganisms for its on-line preconcentration and chemiluminescent determination in water samples

Fungi of the type Aspergillus sp. were immobilized on a cellulosic resin and used as a biosorbent for the on-line preconcentration and separation of Pt(IV) ions prior to their chemiluminescent determination via flow injection analysis. Biosorption and elution conditions were optimized, and the results compared to biosorbents based on the use of Chlorella vulgaris algae and Saccharomyces cerevisiae yeast in terms of preconcentration and selective retention of Pt(IV). The immobilized fungi presented here have a high potential for use in platinum biosorption. The procedure exhibits the currently lowest limit of detection (0.02 ng mL^?1 of Pt) and very high selectivity. The procedure was applied to the determination of Pt(IV) in river water, road run-off, and wastewater samples.

Quantitative determination of wear metals in engine oils using laser-induced breakdown spectroscopy: A comparison between liquid jets and static liquids

A comparison of laser-induced breakdown spectroscopy (LIBS) sensitivity in laminar liquid jets and at the surface of a static liquid has been performed. Limits of detection (LODs) have been estimated for Na, Mg, Al, Ca, Ti, V, Cr, Mn, Ni, Fe, Cu, Zn, Mo, Ag, Cd, and Ba under similar conditions using both experimental arrangements. LODs in liquid jets are found to be four times lower on average compared to measurements at static surfaces. Data acquisition rates in jet experiments are also generally higher than for static liquids due to reduced problems with splashing effects.The use of LIBS in jets has also been investigated for quantitative analysis of used lubricants. A number of contaminants have been measured in a set of used engine oils and the results compared to analysis via ICP-AES, where a good correlation is obtained.     

Platinum levels in urban soils from Palermo (Italy); Analytical method using voltammetry

A fast accumulation of platinum in the environmental and biological matrices was observed in the last years and concern arose about potential environmental and health risks.The toxicity of platinum species has been investigated in various studies, some of their, especially the chlorinated ones, are very toxic and allergenic. Information of the acute toxicity of some Pt-chlorinated salts and evidence of DNA damage due to Pt exposure have been observed both in vitro and in vivo.Taking into account what is written above, the development of reliable analytic methods to measure very low Pt concentrations is required. In this work was developed a reliable method for the determination of Pt in soils because of inherent difficulties in using conventional techniques, in particular, the ICP-OES technique. A determination of Pt using ICP-MS, for instance, is problematic, due to interfering signals. Differential pulse voltammetry (DPV/a) was employed by us for the determination of platinum in soils collected in Palermo area. Possible interferences by other environmental metals have been also evaluated.All samples show concentrations of Pt above average upper crust values; concentrations were found in the ranges 0.6–2240 μ/kg d.w. We carried out linear regression analysis between total Pt concentrations in soils obtained in this work and Pt concentrations in leaves of Nerium oleander measured in previous researches. The high correlation coefficient obtained confirms the geographical distribution of the considered pollutant in the Palermo area.     

Multi-element analysis of iron ore pellets by Laser-induced Breakdown Spectroscopy and Principal Components Regression

Laser-induced Breakdown Spectroscopy (LIBS) in combination with Principal Components Regression (PCR) has been applied to determine the elemental composition of a series of run-of-mine (ROM) iron ore samples. The samples were presented for measurement both as compressed pellets and as loose chipped material. The present paper details the results of the measurements of the compressed pellets. Results from ore chips will be reported separately. LIBS spectral data was recorded in three separate spectral regions to measure major, minor and trace components of the iron ore sample pellets. Background stripping, normalization and spectral cleaning were applied to minimize the relative standard deviations of the LIBS data. PCR analysis was then applied to produce calibration models for iron, aluminum, silicon, manganese, potassium and phosphorous. These calibration models were then validated using independent LIBS measurements. Robust calibration models were determined for iron, aluminum, silicon and potassium, whilst the results for manganese were encouraging. Phosphorous, present at low levels in the ores measured, remained the most difficult element to determine accurately. The combination of LIBS and PCR shows potential for in-situ on-line determination of ore composition.     

Fast and sensitive trace metal analysis in aqueous solutions by laser-induced breakdown spectroscopy using wood slice substrates

To perform fast and sensitive trace metal analysis in aqueous solutions by laser-induced breakdown spectroscopy (LIBS) based on only one single-pulse laser system, a wood slice has been used as a liquid absorber to transform liquid sample analysis to solid sample analysis using LIBS. High detection sensitivity and good reproducibility can be achieved with this approach. Calibration curves for five metal elements, Cr, Mn, Cu, Cd, and Pb under trace concentrations, have been obtained, and the limits of their detection were determined to be in the range of 0.029–0.59 mg L^− 1, 2–3 orders better than those obtained by directly analyzing liquid samples where the laser was focused on a liquid surface. The wood slice was very easy to handle and thus, the whole analysis process took only 4–5 min for each sample. This approach provides a more practical approach for fast and sensitive metal element analysis in aqueous solutions using LIBS, which is especially useful for monitoring toxic heavy metals in water.     

Assessment of immobilized yeast for the separation and determination of platinum in environmental samples by flow-injection chemiluminescence and electrothermal atomic absorption spectrometry

The yeast Saccharomyces cerevisiae immobilized in calcium alginate beads was used for separation and subsequent determination of Pt in environmental samples by flow-injection chemiluminescence (FI-CL) and electrothermal atomic absorption spectrometry (ETAAS). The application of a yeast column resulted in an increase in the tolerable matrix ions concentration compared to direct measurements by both detection techniques. The developed FI-CL method of Pt determination based on the catalytic effect of Pt(IV) ions on luminol oxidation in alkaline medium is characterized by a low limit of detection (0.15 ng mL^?1), and good sensitivity and precision, and can be used for analysis of Pt in water samples. Determination of Pt in more complex environmental samples can be carried out by ETAAS (LOD?=?6 ng mL^?1) after introduction of a column clean-up step with 10 mM nitric acid. The accuracy of the method was confirmed by analyzing the certified reference material of platinum ore (SARM-7), spiked grass, and road dust samples.     

Simultaneous determination of palladium, platinum, rhodium and gold by on-line solid phase extraction and high performance liquid chromatography with 5-(2-hydroxy-5-nitrophenylazo)thiorhodanine as pre-column derivatization regents

In this paper, 5-(2-hydroxy-5-nitrophenylazo)thiorhodanine (HNATR) was synthesized. A new method for the simultaneous determination of palladium, platinum, rhodium and gold ions as metal-HNATR chelates was developed using a rapid analysis column high performance liquid chromatography equipped with on-line solid phase extraction technique. The samples (Water, human urine, geological samples and soil) were digested by microwave acid-digestion. The palladium, platinum, rhodium and gold ions in the digested samples were pre-column derivatized with HNATR to form colored chelates. The Pd-HNATR, Pt-HNATR, Rh-HNATR and Au-HNATR chelates can be absorbed onto the front of the enrichment column when they were injected into the injector and sent to the enrichment column [Zorbax Stable Bound, 10 mm x 4.6 mm, 1.8 microm] with a buffer solution of 0.05 mol L(-1) phosphoric acid as mobile phase. After the enrichment had finished, by switching the six ports switching valve, the retained chelates were back-flushed by mobile phase and travelling towards the analytical column. These chelates separation on the analytical column [Zorbax Stable Bound, 10 mm x 4.6 mm, 1.8 microm] was satisfactory with 72% acetonitrile (containing 0.05 mol L(-1) of phosphoric acid and 0.1% of Triton X-100) as mobile phase. The palladium, platinum, rhodium and gold chelates were separated completely within 2.5 min. Compared to the routine chromatographic method, more then 80% of separation time was shortened. By on-line solid phase extraction system, a large volume of sample (10 mL) can be injected, and the sensitivity of the method was greatly improved. The detection limits (S/N=3, the sample injection volume is 10 mL) of palladium, platinum, rhodium and gold in the original samples reaches 1.4, 1.8, 2.0 and 1.2 ng L(-1), respectively. The relative standard deviations for five replicate samples were 2.4-3.6%. The standard recoveries were 88-95%. This method was applied to the determination of palladium, platinum, rhodium and gold in human urine, water and geological samples with good results.     

火试金预浓集结合中子活化和电感耦合等离子体质谱法测定铂族元素

建立了两种以火试金预浓集为基础的、可用于准确测定铂族元素的方法;中子活化法和电感耦合等离子体质谱法。讨论了它们的分析检出限、准确度及其适应性。并用这两种方法测定了5种候选地质参考物质中铂族元素的含量。     

Problems,possibilities and limitations of inductively coupled plasma atomic emission spectrometry in the determination of platinum,palladium and rhodium in samples with different matrix composition

The economic and geological importance of platinum group of elements has led to the development of analytical methods to quantify them in different types of samples. In the present paper the quantitative information for spectral interference in radial viewing 40.68 MHz inductively coupled plasma atomic emission spectrometry in the determination of Pt, Pd and Rh in the presence of complex matrix, containing Al, Ca, Fe, Mg, Mn, P and Ti as matrix constituents was obtained. The database was used for optimum line selections. By using the selected analysis lines the following detection limits in ng g^− 1 were obtained: Pt 1700, Pd-1440, Rh-900. The reached detection limits determine the possibilities and limitation of the direct ICP-AES method in the determination of Pt, Pd and Rh in geological and environmental materials. The database for spectral interferences in the presence of aluminum can be used for the determination of platinum group of elements in car catalysts.     

Determination of trace elements including platinum in tree bark by ICP mass spectrometry

The increasing emission of Pt-group metals from automobile catalytic converters requires the development of highly sensitive procedures for ultratrace analysis of environmental and biological systems. Tree bark, located close to motorway or industrial areas, was utilised as a substrate for collection of airborne particulate matter and samples after digestion (microwave assisted dissolution with HNO3 and HCl) were analysed by ICP mass spectrometry. The study targeted Pt and other metallic contaminants and involved analysis of some 57 tree bark samples using both quadrupole and double-focusing sector field ICP mass spectrometers. Detection limits for platinum determination in tree bark were 0.03 ng/g (DF-ICP-MS) and 0.2 ng/g (ICP-QMS). The platinum content of the bark samples ranged from 0.07-5.4 ng/g.     

Voltammetric Determination of Platinum in Plant Material

A very sensitive procedure for the determination of platinum in hydroponically cultivated plant samples (Sinapis alba L and Lolium perenne) is presented. A microwave digestion with HNO₃, HClO₄ and HCl acids with additional UV irradiation is followed by the platinum determination by adsorptive stripping voltammetry at hanging mercury drop electrode. The influence of HNO₃ acid on voltammetric determination of platinum is discussed. For validation of the obtained results the recovery of Pt was examined and the Pt determination by ICP MS was carried out. The highest platinum amounts were found in the roots of the plants, nevertheless the effective transport of platinum to the steams and leaves was also observed.     

Determination of trace elements including platinum in tree bark by ICP mass spectrometry

The increasing emission of Pt-group metals from automobile catalytic converters requires the development of highly sensitive procedures for ultratrace analysis of environmental and biological systems. Tree bark, located close to motorway or industrial areas, was utilised as a substrate for collection of airborne particulate matter and samples after digestion (microwave assisted dissolution with HNO₃ and HCl) were analysed by ICP mass spectrometry. The study targeted Pt and other metallic contaminants and involved analysis of some 57 tree bark samples using both quadrupole and double-focusing sector field ICP mass spectrometers. Detection limits for platinum determination in tree bark were 0.03 ng/g (DF-ICP-MS) and 0.2 ng/g (ICP-QMS). The platinum content of the bark samples ranged from 0.07–5.4 ng/g.     

Elemental analysis by surface-enhanced Laser-Induced Breakdown Spectroscopy combined with liquid–liquid microextraction

In this work, the possibility of using Laser-Induced Breakdown Spectrometry (LIBS) combined with liquid–liquid microextraction techniques is evaluated as a simple and fast method for trace elemental analysis. Two different strategies for LIBS analysis of manganese contained in microdroplets of extraction solvent (Triton X-114) are studied: (i) analysis by direct laser irradiation of microdroplets; and (ii) analysis by laser irradiation of microdroplets dried on metallic substrates (surface-enhanced LIBS — SENLIBS). Experiments were carried out using synthetic samples with different concentrations of manganese in a 10% w/w Triton X-114 matrix. The analysis by direct laser irradiation of microdroplets showed low precision, sensitivity and poor linearity across the concentration range evaluated (R² < 0.95). On the other hand, the SENLIBS method of analysis improved the sensitivity, the precision and the linearity of the calibration curve with respect to the direct analysis of microdroplets. In comparison with experimental results obtained by direct analysis, SENLIBS also allowed several replicate measurements to be carried out in a single microdroplet. The limit of detection obtained was 6 μg g^− 1 of Mn.     

Rapid determination of platinum plasma concentrations of chemotherapy patients using total reflection X-ray fluorescence

A fast and simple method using Total Reflection X-ray Fluorescence has been developed for the determination of platinum plasma concentrations of patients undergoing chemotherapy with Pt-bearing drugs. Avoiding chemical digestion, micro liter amounts of blood plasma are employed using Compton peak standardization and the use of matrix-matched spiked samples with known amounts of platinum for spectrometer sensitivity determination. The analytical results with the proposed procedure are compared to values obtained with Graphite Furnace Atomic Absorption Spectrometry obtaining values of comparable accuracy and precision. Measurements of the time course of the Pt plasma concentration in single-dose treatments, and of the achieved plasma concentration of multiple infusion treatments demonstrate the potential usefulness of the method for pharmacokinetic studies or for routine optimization of Pt chemotherapy treatments.     

Evaluation of laser induced breakdown spectroscopy for the determination of macronutrients in plant materials

Laser induced breakdown spectroscopy (LIBS) has become an analytical tool for the direct analysis of a large variety of materials in order to provide qualitative and/or quantitative information. However, there is a lack of information for LIBS analysis of agricultural and environmental samples. In this work a LIBS system has been evaluated for the determination of macronutrients (P, K, Ca, Mg) in pellets of vegetal reference materials. An experimental setup was designed by using a Nd:YAG laser operating at 1064 nm and an Echelle spectrometer with ICCD detector. The plasma temperature was estimated by Boltzmann plots and instrumental parameters such as delay time, lens-to-sample distance and pulse energy were evaluated. Certified reference materials as well as reference materials were used for analytical calibrations of P, K, Ca, and Mg. Most results of the direct analysis of plant samples by LIBS were in reasonable agreement with those obtained by ICP OES after wet acid decomposition.     

Multivariate calibration of spectra obtained by Laser Induced Breakdown Spectroscopy of plutonium oxide surrogate residues

Laser Induced Breakdown Spectroscopy (LIBS) was used to determine elemental concentration of plutonium oxide surrogate (cerium oxide) residue for monitoring the fabrication of lanthanide borosilicate glass. Quantitative analysis by LIBS is affected by the severe limitation of variation in the induced plasma due to changes in the matrix. Multivariate calibration was applied to LIBS data to predict the concentrations of Ce, Cr, Fe, Mo, and Ni. A total of 18 different samples were prepared to compare calibration from univariate data analysis and from multivariate data analysis. Multivariate calibration was obtained using Principal Component Regression (PCR) and Partial Least Squares (PLS). Univariate calibration was obtained from background-corrected atomic emission lines. Calibration results show improvement in the coefficient of determination from 0.87 to 0.97 for Ce compared to univariate calibration. The root mean square error also reduced from 7.46 to 2.93%. A similar trend was obtained for Cr, Fe, Mo, and Ni also. These results clearly demonstrate the feasibility of using LIBS for online process monitoring in a hazardous waste management environment.     

Determination of nine emerging pesticides at trace level in aqueous samples using fully automated on-line solid phase extraction coupled with liquid chromatography-mass spectrometry

On-line solid phase extraction (SPE) coupled to liquid chromatography-mass spectrometry (LC-MS) offers an easy and fast strategy to analyze the organic contaminants in environmental samples with high sensitivity and selectivity. This paper described an in-house designed on-line SPE system and an on-line SPE-LC-MS method for the determination of pesticides at trace levels in water samples. The system was assembled from an eight-position valve, a piston pump, a six-port valve and a C18 SPE column, and significantly reduced analysis time by achieving full automation. Moreover, the use of a large enrichment volume (50?mL) significantly enhanced method sensitivity. Using this on-line SPE system, an on-line SPE-LC-MS method was developed for the determination of nine pesticides at trace levels in lake water and seawater sample. Under optimized conditions, method detection limits (MDLs) were 1.00–10.0?ng?L^?1.     

Metal-Loaded Sorbents for Selective On-Line Sample Handling and Trace Enrichment in Liquid Chromatography

Abstract

Three different commercially available stationary phases containing a thiol, an 8-hydroxyquinoline (oxine), and a 2-amino-1-cyclopentene-1-dithiocarboxylic acid (ACDA) functional group, were loaded with mercury (Hg(II)), platinum (Pt(IV)) and silver (Ag(I)) ions. The phases were packed in small precolumns and evaluated for their potential towards the selective on-line sample handling and trace enrichment of three model systems in liquid chromatography. The thiol 2-mercaptobenzimidazole was used to study trace enrichment on Hg(II)-loaded phases; the herbicide buturon, which contains an ethynic bond, was selected to study trace enrichment on Ag(I)-loaded phases. The on-line filter effect of Pt(IV)-loaded phases was investigated with 4-chloroaniline as a model compound.

The results indicate that the Hg(II)-ACDA phase should be preferred for the trace enrichment of thiols, a Pt(IV)-ACDA or a Pt(IV)-thiol phase for the anilines and the Ag(I)-oxine phase for the trace enrichment of ethynic compounds.

As environmental application, the selective on-line trace enrichment of buturon from river water samples, on a precolumn packed with Ag(I)-oxine, is shown.