Development of an on-line solid phase extraction method based on new functionalized magnetic nanoparticles. Use in the determination of mercury in biological and sea-water samples.

A new chelating sorbent which employs magnetic nanoparticles (MNPs) functionalized with 1,5-bis(di-2-pyridil)methylene thiocarbohydrazide (DPTH-MNPs) was synthetized and characterized. The aim of the synthesis of this material was to develop fast and simple methods for analysis of trace amounts of metal ions present in biological and environmental samples combining on-line magnetic solid phase microextraction (MSPME) with atomic spectrometry. The MNPs' magnetic core allows overcoming the backpressure problems that usually happen in SPME methods with NPs thanks to the possibility of immobilizing the MNPs by applying an external magnetic field. Thus, a flow injection FI-MSPME/cold vapor generation system coupled to an electrothermal atomic absorption spectrometer (CV-ETAAS) method for the determination of trace amounts of Hg in biological and sea-water samples was developed. A magnet based reactor designed to contain DPTH-MNPs was placed in the injection valve of the FI manifold. Several chemical and flow variables were considered as factors in the optimization process using central composite designs. With the optimized procedure, the detection limit obtained was 7.8ngL(-1) with a precision of 1.7% (RSD) (1.0µgL(-1) Hg). The linear range of the method was studied, and two sections of linear calibration were obtained: from determination limit (0.099µgL(-1)) to 10µgL(-1), and from 10µgL(-1) to at least 50µgL(-1). A preconcentration factor of 5.4 was calculated. The accuracy of the proposed method was demonstrated by analyzing three certified reference materials and by determining the analyte content in spiked sea-water samples. The determined values were in good agreement with the certified values and the recoveries for the spiked samples were in the range of 97.0-107.0%.

Multi-element determination of Pt, Pd and Ir traces in environmental samples by ICP-MS after pre-concentration.

An automated flow analysis method with on-line column pre-concentration/ inductively coupled plasma mass spectrometry (ICP-MS) was developed for the simultaneous determination of Pt, Pd and Ir in environmental samples. The system is based on retention of the analytes onto a column filled with 1,5-bis (2-pyridyl)-3-sulphophenyl methylene thiocarbonohydrazide immobilized on an aminopropyl-controlled pore glass (PSTH-cpg) placed in the injection valve of a simple flow manifold. The retained platinum group metals (PGMs) were subsequently eluted with a mixture of HNO(3) and thiourea. The effects of chemicals and flow variables were investigated. The optimized operating conditions were: sample pH 3.2, sample flow rate: 1.1 mL min(-1); eluent flow rate: 2.1 mL min(-1) and eluent 0.03% m/v thiourea solution in 3.2% (v/v) HNO(3). The detection limits obtained were 78.5 ng L(-1) for Pt, 55.5 ng L(-1) for Pd and 0.1 ng L(-1) for Ir. The enrichment factors were 18, 2.3 and 43 for Pt, Pd and Ir, respectively. The accuracy of the method was checked by the analysis of certified reference materials and by determining the analytes content in spiked environmental samples. Recovery was found to be in the range 93-107% in all cases.

Synthesis and acid digestion of biomorphic ceramics: determination of alkaline and alkaline earth ions.

Ceramic and glass are some of the more recent engineering materials and those that are most resistant to environmental conditions. They belong to advanced materials in that they are being developed for the aerospace and electronics industries. In the last decade, a new class of ceramic materials has been the focus of particular attention. The materials were produced with natural, renewable resources (wood or wood-based products). In this work, we have synthesised a new biomorphic ceramic material from oak wood and Si infiltration. After the material characterization, we have optimized the dissolution of the sample by acid attack in an oven under microwave irradiation. Experimental designs were used as a multivariate strategy for the evaluation of the effects of varying several variables at the same time. The optimization was performed in two steps using factorial design for preliminary evaluation and a Draper-Lin design for determination of the critical experimental conditions. Five variables (time, power, volume of HNO3, volume H2SO4 and volume of HF) were considered as factors and as a response the concentration of different metal ions in the optimization process. Interactions between analytical factors and their optimal levels were investigated using a Draper-Lin design.

Automated on-line preconcentration of palladium on different sorbents and its determination in environmental samples.

The determination of noble metals in environmental samples is of increasing importance. Palladium is often employed as a catalyst in chemical industry and is also used with platinum and rhodium in motor car catalytic converters which might cause environmental pollution problems. Two different sorbents for palladium preconcentration in different samples were investigated: silica gel functionalized with 1,5-bis(di-2-pyridyl)methylene tbiocarbohydrazide (DPTH-gel) and [1,5-Bis(2-pyridyl)-3-sulphophenyI methylene thiocarbonohydrazide (PSTH) immobilised on an anion-exchange resin (Dowex lx8-200)]. The sorbents were tested in a micro-column, placed in the auto-sampler arm, at the flow rate 2.8 mL min(-1). Elution was performed with 4 M HCl and 4 M HNO3, respectively. Satisfactory results were obtained for two sorbents.

Application of flow injection on-line electrothermal atomic absorption spectrometry to the determination of rhodium.

A fully automated procedure for the determination of rhodium has been developed using flow injection (FI) on-line microcolumn preconcentration coupled with electrothermal atomic absorption spectrometry (ETAAS). The proposed FI manifold and its operation make possible the introduction of the total eluate volume into the graphite atomizer, avoiding the necessity for optimisation of subsampling the eluate. Rhodium is adsorbed on a microcolumn packed with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide immobilized on silica gel (DPTH-gel). Under the optimum conditions, using a 60 s preconcentration time, a sample flow rate of 3.5 mL min(-1) and an injection volume of eluent of 50 microL, a linear calibration graph was obtained from 1 to at least 40 ng mL(-1) and the detection limit was 1 ng mL(-1). The proposed method has been successfully applied to the analysis of samples. Its performance was investigated against certified reference catalyst sample SRM-2557 and by recovery measurements on spiked samples (soil, foods and beverages).