Studies of ion-imprinted polymers for solid-phase extraction of ruthenium from environmental samples before its determination by electrothermal atomic absorption spectrometry

The examination of the effect of interfering ions on the analytical signal of ruthenium measured by electrothermal atomic absorption spectrometry was initially performed in this work. The complexes of ruthenium(III) with thiosemicarbazide (TSd) and acetaldehyde thiosemicarbazone (AcTSn) were prepared and imprinted in polymeric network. The ion-imprinted polymers were synthesized by copolymerization of methacrylic acid, as functional monomer and ethylene glycol dimethacrylate, as crosslinking agent in the presence of 2,2-azobisisobutyronitrile as initiator. The effects of sample volume, pH, and flow rate on the extraction of analyte were studied in dynamic mode. The optimum pH for quantitative retention of ruthenium on each of the studied sorbents was 7.5 ± 0.5. The elution of analyte was completed with 0.2 mol L⁻¹ thiourea in 0.2 mol L⁻¹ HCl. The effect of matrix ions on ruthenium(III) separation process was studied. The analytical performance of the Ru-TSd polymer in the presence of competing ions was better than Ru-AcTSn polymer, considering recovery of analyte, reproducibility of results, selectivity coefficients, and sorbent capacity. The detection limit of the proposed method (0.16 ng mL⁻¹ on Ru-TSd and 0.25 ng mL⁻¹ on Ru-AcTSn) is lower in comparison with the previously published methods. The developed separation method was successfully applied to the determination of trace amounts of ruthenium in spiked water samples, sludge, grass, and human hair.     

Cadmium,lead, copper and manganese determination in human deciduous teeth by electrothermal atomic absorption spectrometry using a lanthanum,palladium and citric acid mixture as chemical modifier

Cadmium, lead, copper and manganese were determined in human deciduous teeth and bone ash 1400 standard reference material by electrothermal atomic absorption spectrometry (ETAAS), using a lanthanum + palladium + citric acid (CA) modifier mixture. Optimum masses and mass ratios of La, La + Pd and La + Pd + CA modifiers for analytes in bone ash 1400 sample solution were investigated. Pyrolysis and atomization temperatures of analytes in a tooth sample solution were obtained with and without modifiers. The mixture of La + Pd + CA was found to be preferable for the determination of analytes in tooth samples and bone ash 1400, dissolved in a mixture of HNO₃ + H₂O₂. The detection limits and characteristic masses of analytes were obtained with or without modifiers based on integrated absorbance for tooth sample solution (2% m/v). The detection limits obtained with La + Pd + CA are 6,24,16 and 46 ng g^?1 for Cd, Cu, Mn and Pb, respectively. Recovery tests for analytes in bone ash 1400 and a tooth solution with La and La + Pd + CA modifier mixture were studied and compared with certified and non certified values. The La + Pd + CA mixture was also applied to the determination of Cd, Pb, Cu and Mn in tooth samples.     

Speciation analysis of thallium in water samples after separation/preconcentration with the Empore™ chelating disk

A simple, reliable and novel solid phase extraction procedure using the Empore? chelating disk has been developed for determination of Tl(I) and Tl(III) in environmental water samples by electrothermal atomic absorption spectrometry (ETAAS). The influence of humic acids on separation/preconcentration of thallium species with the Empore? chelating disk is investigated. The preconcentration factor and detection limit are 500 and 5?ng?L^?1, respectively. The recoveries are in the range 93–103% for mineral, pond, sea, snowmelt, waste waters at 28–500?ng?L^?1 Tl and in the range 82–112% for river waters at 18–28?ng?L^?1 Tl.     

Determination of Pb(II) and Cu(II) by Electrothermal Atomic Absorption Spectrometry after Preconcentration by a Schiff Base Adsorbed on Surfactant Coated Alumina

1,2-Bis（salicylidenamino）ethane loaded onto sodium dodecyl sulfate-coated alumina was used as a new chelating sorbent for the preconcentration of traces of Pb（Ⅱ） and Cu（Ⅱ） prior to atomic absorption spectrometric determination. The influence of pH, flow rates of sample and eluent solutions, and foreign ions on the recovery of Pb（Ⅱ） and Cu（Ⅱ） by this sorbent has been studied. The retained ions were eluted with 4 mol·L nitric acid and determined by electrothermal atomic absorption spectrometry （ETAAS）. The data of limit of detection （3σ） for Pb（Ⅱ） and Cu（Ⅱ） were found to be 8.57 and 2.69 ng·L^-1 respectively, while the enrichment factor for both ions was 100. The proposed method was successfully applied to determination of lead and copper in different water samples.     

利用聚四氟乙烯为化学改进剂降低电热原子吸收测定铬的基体干扰

本文研究了电热原子吸收光谱测定痕量铬时几种常见的金属离子的干扰作用。     

Simultaneous determination of lead, nickel, tin and copper in aluminium-base alloys using slurry sampling by electrical discharge and multielement ETAAS

The simultaneous multielement determination of Pb, Sn, Ni and Cu in aluminium alloys by electrothermal atomic absorption spectrometry (ETAAS) was performed by a quick method using slurry sampling. The metallic colloidal slurries were obtained by an electrical discharge operated in liquid medium. In this work, the effects of aluminium were evaluated and the results show that it causes a strong retention of Pb, Ni and Cu at low pyrolysis temperatures which is overcome by employing high pyrolysis temperatures. Aluminium also significantly improves the thermal stabilisation of Pb and Sn, it being possible to reach pyrolysis temperatures of 1100 and 1300 °C, respectively. Such stabilisation indicates that the performance of aluminium as a matrix modifier for Pb is better than that obtained using phosphate and magnesium nitrate without substantial changes of the figures of merit. The effects of aluminium on the atomisation characteristics of the elements and those coming from the simultaneous multielement determination on the figures of merit of the elements are also discussed. In this work, a calibration procedure involving a matrix matching method with aqueous aluminium standards is proposed as a simple and efficient way to solve the inconveniences originated by the aluminium matrix. The proposed method was applied to the simultaneous multielement determination of several aluminium-base alloy standards giving results well within the recommended values.     

Determination of total and methyl mercury in human permanent healthy teeth by electrothermal atomic absorption spectrometry after extraction in organic phase

A simple and sensitive method has been developed for determination of inorganic and methyl mercury in biological samples by ETAAS. For determination of methyl mercury; it was transferred to toluene phase by acid leaching extraction method. For total mercury after digestion of samples; it was extracted to toluene phase by means of the chelating agent diethyldithiocarbamate. Formation of complex between MeHg and diethyldithiocarbamate enhance the MeHg signal and increases the reproducibility. Furthermore, Pd-DDC was used as modifier for both mercury and methyl mercury determinations. The optimization performance was independently carried out by modifying the parameters such as temperature of mineralization, atomization and gas flow rate for methylmercury and inorganic mercury in ETAAS. The limits of detection were 0.15 and 0.12 μg g⁻¹ for methyl mercury and total mercury, respectively. The repeatability of the measurements of whole procedure were 15.8% for methyl mercury and 16.9% for total mercury determination. The accuracy of the method has been investigated by means of spiking different amounts of methylmercury and inorganic mercury to the samples. The recoveries were found within the range of 88-95% for methyl mercury and 85-92% for total mercury. For determination of total mercury, the method was validated by CVAAS. The obtained results by the present procedure were in good agreement with those of the CVAAS. The proposed method was applied for 30 human permanent healthy teeth (without filling) which significant positive correlations were found among number of amalgam filling and total mercury and MeHg.     

Evaluation of a cloud point extraction method for the preconcentration and quantification of silver nanoparticles in water samples by ETAAS

ABSTRACT

A simple and reliable analytical method using instrumentation available in most of the laboratories has been developed for the separation and determination of silver nanoparticles in water samples. Cloud point extraction (CPE) was used for the separation of silver nanoparticles (AgNPs) from the sample and these nanoparticles were then determined by electrothermal atomic absorption spectrometry (ETAAS). Parameters related to the cloud point extraction procedure (Triton X-114 concentration, type of complexing agent (EDTA or Na₂S₂O₃), pH, incubation temperature, incubation and centrifugation time) were selected using a multivariate approach (designs of experiments); 8.6% (v/v) Triton X-114, 750 µL saturated EDTA and pH 7 were selected as the optimum conditions. Calibration standards in a concentration range from 0 to 10 µg L^?1 of AgNPs were subjected to the CPE procedure to obtain quantitative recoveries. The LOD and LOQ were 0.04 and 0.13 µg L^?1, respectively. The method is selective for the extraction of AgNPs, and ionic Ag remains in the aqueous phase. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) was used to evaluate the effect of the CPE procedure in particle size, and no changes were observed. Finally, the procedure was applied to wastewater samples spiked with nanoparticles with quantitative recoveries.     

Vapor phase matrix extraction of high purity di-boron trioxide and trace analysis using electrothermal AAS

A method has been developed for the determination of Al, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Sb, Sn and Zn at trace levels in high purity di-boron trioxide using ETAAS. The boron trioxide matrix was eliminated as trimethyl borate ester in a multiplex vapor phase matrix extraction (MVPME) device using a mixture of glycerol and methanol. In this MVPME device, in situ reagent purification, sample digestion and simultaneous matrix elimination were achieved by a single step in closed condition, which in combined effect reduce the process blanks. The matrix extraction procedure allows determination of trace elemental impurities by electrothermal atomic absorption spectrometry (ETAAS) with fast furnace analysis (without an ashing step and modifier) and calibration against aqueous standards. The performance and accuracy of the vapor phase matrix elimination technique are compared to those of suprapur grade hydrofluoric acid solution in two ways; (i) matrix separation as BF₃ over hot plate and (ii) in situ matrix elimination inside graphite furnaces. The method detection limits calculated from blank samples are in the range of 0.5 (Ni) and 2.9 (Al) ng g⁻¹. Thus the MVPME-based sample preparation approach is well suited for the trace analysis of high purity di-boron trioxide used in microelectronics applications.     

Behaviour of chemical modifiers in the determination of arsenic by electrothermal atomic absorption spectrometry in petroleum products

Most comparative studies on the efficiency of chemical modifiers have been conducted in aqueous media. In the present work, we proposed a detailed study of the use of different chemical modifiers for direct determination of arsenic in complex organic matrices by electrothermal atomic absorption spectrometry (ETAAS). Palladium, rhodium, tungsten, silver, lanthanum and a mixture of palladium and magnesium were tested. The figures of merit used for evaluation and comparison were acquired in the optimal conditions for each modifier, established by multivariate optimization of the main variables based on Doehlert designs. Singular features were observed for the chemical behaviour of some modifiers in organic matrices compared to aqueous media, such as the worse performance of Pd + Mg modifier and no notice of severe tube corrosion from La application. Lanthanum was chosen as the best chemical modifier for the present application, according to predefined criteria. Lanthanum showed the minimum limit of detection, characteristic concentration and blank signal among all tested species and no effect of the concomitants usually present in petrochemical feedstocks. Using a 200 mg L⁻¹ lanthanum solution as a chemical modifier, the average relative standard deviations of 7 and 16% (at 3-15 μg L⁻¹ level) and characteristic concentrations of 0.47 and 0.77 μg L⁻¹ for naphtha and petroleum condensates, respectively, were observed.