José Manuel Cano Pavón

Herein, a chelating sorbent that employs magnetic nanoparticles (MNPs) functionalized with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide (DPTH-MNPs) has been used to develop a simple method for the analysis of trace amounts of metal ions present in environmental samples; the method combines on-line magnetic solid phase extraction (MSPE) with atomic spectrometry. Thus, a flow injection FI-MSPE/cold vapour generation system coupled to an inductively coupled plasma optical emission spectrometry (ICP OES) method for the determination of trace amounts of noble metals, platinum group elements (PGEs: Ir, Pd, Pt, Os, and Rh), and Au and Ag in environmental samples has been 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 two central composite designs; with the optimized method, the experimental detection limits for simultaneous determination, calculated as the concentration of analyte giving signals equivalent to three times the standard deviation of the blank plus the net blank intensity (LOD, peak height), were 1.5 μg L⁻¹, 0.03 μg L⁻¹, 0.65 μg L⁻¹, 0.62 μg L⁻¹, 0.57 μg L⁻¹, 0.03 μg L⁻¹, and 100 μg L⁻¹ for Pd, Ag, Os, Au, Ir, Pt, and Rh, respectively. The method offers relatively good precision (RSD 1.8–7.2%). The accuracy of the proposed method was verified using certified reference materials (CMRs, NIST 2557 autocatalyst, TMDA 54.4 fortified lake water, and SRM 1643e trace elements in fresh water) and by determining the analyte contents in spiked aqueous samples. Sea water and tap water samples obtained from Malaga (Spain) were also analysed. The determined values were in good agreement with the certified values, and the recoveries for the spiked samples were in the range of 91.8–108.1%. Additionally, the proposed method was applied in the simultaneous determination of the abovementioned 7 elements with a sample throughput of about 17 h⁻¹, thereby reducing the time of analysis and the volumes of reagents and sample required.

Concentrations of heavy metals (Cd, Cr, Cu, Ni and Pb) were measured in sediment and water from a representative Western Mediterranean basin in South Spain: Guadalhorce River. In the later twentieth century, cities such as Málaga (capital of the Costa del Sol), have suffered the impact of the mass summer tourism. The ancient industrial activities, abandoned mine sites and the actual urbanisation and coastal development, recreation and tourism, wastewater treatment facilities, have been sources of pollution. This river has been heavily modified, with three dams for volume regulation purposes owing to the climatic cycles, with some years very dry and others with torrential rains. In this study, different indices to assessment of sediment contamination, statistical tools (Kruskall–Wallis test, Conglomerate analysis), sequential extraction methods and environmental quality guidelines have been employed to assess the possible contamination of this basin. Other physical–chemical parameters as chloride concentration, pH and conductivity were also measured. The results indicated that Ni and Cu were the most troublesome metals because they were more easily mobilisable than Cr and Pb; Ni exceeds the SQGs guidelines, and Cu presents considerable contamination. These metals were derived from lithogenic and anthropogenic sources, respectively, according to the enrichment factors (EF) values. Ni was the most dangerous because Ni concentrations exceeded the threshold effect concentration (TEC) below which harmful effects are unlikely to be observed, in 96.6% of the samples analysed and even the probable effect concentration (PEC) above which harmful effects are likely to be observed, in 56.6%. The cause of this pollution was postulated to be by abandoned Ni mines, which indicates that the pollution from mining persists during several decades. Multivariate analyses used in this study provide important tools for better understanding of the pollution source identification.

An inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the sequential determination of Pb, Cd and Hg in natural waters, including sea-water, using an on-line preconcentration flow injection chemical vapour generation (FI-CVG) system. The system is based on the use of two minicolumns packed with a chelating resin which were placed in two injection valves of a simple flow manifold to be loaded simultaneously. A third valve was arranged to select the reagent for the selective vapour generation of the analytes and, thus make possible the sequential determination of the three metals. By using this device, diverse advantages are attained: increase of the sensitivity and reduction of the interferences by the preconcentration and the vapour generation. The detection limits achieved (3 min sample loading time) were: 9, 17 and 12 ngL⁻¹ for Pb, Cd and Hg, respectively, with a sample throughput of about 10.4 h⁻¹. The accuracy of the proposed method was checked with three certified reference materials (CRMs): TMDA-54.4 fortified lake water, LGC6016 estuarine water and CASS-5 oceanic water, and the results obtained were in good agreement with the certified values. The method was also applied to the determination of Pb, Cd and Hg in different sea-water samples from Málaga Bay.

The efficiencies of two types of chelating resins were evaluated and optimized for the extraction and determination of lead by flow injection graphite furnace and hydride generation atomic absorption spectrometry (FI-HG-ETAAS) in environmental water samples. The optimum analytical conditions were examined and the analytical features of each method were revealed and compared in terms of sensitivity, selectivity and accuracy. Lead determination by FI-HG-ETAAS using [1,5-bis(2-pyridyl)-3-sulphophenyl methylene] thiocarbonohydrazide immobilised on aminopropyl-controlled pore glass (PSTH-cpg, 55 nm) provides a detection limit of 3.0 ng l⁻¹ lead with a relative standard deviation (R.S.D.) of 2.5% at the 50 ng l⁻¹ level (n = 10) compared to silica gel funtionalized with methylthiosalicylate (TS-gel) which provides a detection limit of 82 ng l⁻¹. Under the optimal experimental conditions, with the use of PSTH-cpg and a tungsten–rhodium coated graphite furnace, an enhancement factor of 20 was obtained with a sample consumption of 6.4 ml, while an enhancement factor of 3.5 was obtained with the use of TS-gel. Both methods have been applied to the determination of low levels of lead in environmental water samples. The results obtained show good agreement with certified or expected values.

A method was developed for the simultaneous separation, preconcentration and determination of antimony, bismuth and tin by flow injection solid phase extraction coupled with on-line hydride generation inductively coupled plasma mass spectrometry. The system is based on cationic retention of the analytes onto a mini-column filled with silica gel functionalised with 1,5-bis(di-2-pyridyl) methylene thiocarbonohydrazide placed in the injection valve of a simple flow manifold. The effects of chemicals and flow variables were investigated. The optimized operating conditions selected were: sample pH 3.5, sample flow rate 1.9 mL min⁻¹, eluent flow rate 0.5 mL min⁻¹, eluent 4% HNO₃ and also 0.75% L-cysteine was added directly to the standard and sample solutions. The relative standard deviations (n = 10) were 1.4% for Sb, 1.1% for Bi and 1.5% for Sn. The enrichment factors were 7.0, 8.6 and 2.5 for Sb, Bi and Sn, respectively. Detection limits (3 min sample loading time) were 0.011 μg L⁻¹ for Sb, 0.002 μg L⁻¹ for Bi and 0.142 μg L⁻¹ for Sn. The accuracy of the proposed method was checked with two certified reference materials (CRMs) of natural water TMDA-54.4 and TM-24.3. The results obtained using this method were in good agreement with the certified values of standard reference materials. The recoveries for the method when applied to determine traces of analytes in seawater were 97.0–107.5%.