E. Vereda Alonso

Flow injection on-line electrothermal atomic absorption spectrometry.

Today the greatest hindrances to couple the continuous FI system to discrete ETAAS operations have been overcome as demonstrated by the great number of papers published in the last few years. This paper reviews 109 references to the development and expansion of the FI-ETAAS methodology. The selected FI-ETAAS systems, namely: on-line column preconcentration and separation systems; on-line knotted reactor preconcentration systems; on-line aerosol deposition systems; flow-injection for in situ trapping of volatile compounds and miscellaneous on-line systems.

Bioavailability of heavy metals in water and sediments from a typical Mediterranean Bay (Málaga Bay, Region of Andalucía, Southern Spain).

Concentrations of heavy metals were measured in sediment and water from Málaga Bay (South Spain). In the later twentieth century, cities such as Málaga, have suffered the impact of mass summer tourism. The ancient industrial activities, and the actual urbanization and coastal development, recreation and tourism, wastewaters treatment facilities, have been sources of marine pollution. In sediments, Ni was the most disturbing metal because Ni concentrations exceeded the effects range low (ERL), concentration at which toxicity could start to be observed in 85% of the samples analyzed. The metal bioavailability decreased in the order: Cd>Ni>Pb>Cu>Cr. In the sea water samples, Cd and Pb were the most disturbing metals because they exceeded the continuous criteria concentration (CCC) of US EPA in a 22.5% and 10.0% of the samples, respectively. Statistical analyses (ANOVA, PCA, CA) were performed.

Mercury speciation in sea food by flow injection cold vapor atomic absorption spectrometry using selective solid phase extraction

An on-line inorganic and organomercury species separation, preconcentration and determination system consisting of cold vapor atomic absorption spectrometry (CV-AAS or CV-ETAAS) coupled to a flow injection (FI) method was studied. The inorganic mercury species was retained on a column (i.d., 3 mm; length 3 cm) packed to a height of 0.7 cm with a chelating resin aminopropyl-controlled pore glass (550 A) functionalized with [1,5-bis (2 pyridyl)-3-sulphophenyl methylene thiocarbonohydrazyde] placed in the injection valve of a simple flow manifold. Methylmercury is not directly determined. Previous oxidation of the organomercurial species permitted the determination of total mercury. The separation of mercury species was obtained by the selective retention of inorganic mercury on the chelating resin. The difference between total and inorganic mercury determined the organomercury content in the sample. The inorganic mercury was removed on-line from the microcolumn with 6% (m/v) thiourea. The mercury cold vapor generation was performed on-line with 0.2% (m/v) sodium tethrahydroborate and 0.05% (m/v) sodium hydroxide as reducing solution. The determination was performed using CV-AAS and CV-ETAAS, both approaches have been used and compared for the speciation of mercury in sea food. A detection limit of 10 and 6 ng l(-1) was achieved for CV-AAS and CV-ETAAS, respectively. The precision for 10 replicate determinations at the 1 microg l(-1) Hg level was 3.5% relative standard deviation (R.S.D.), calculated from the peak heights obtained. Both approaches were validated with the use of two certified reference materials and by spiking experiments. By analyzing the two biological certified materials, it was evident that the difference between the total mercury and inorganic mercury corresponds to methylmercury. The concentrations obtained by both techniques were in agreement with the certified values or with differences of the certified values for total Hg(2+) and CH(3)Hg(+), according to the t-test for a 95% confidence level. It is amazing how this very simple method is able to provide very important information on mercury speciation.

Speciation of antimony(III) and antimony(V) in seawater by flow injection solid phase extraction coupled with online hydride generation inductively coupled plasma mass spectrometry

An automated low pressure flow analysis method with online columns pre-concentration/hydride generation (HG) inductively coupled plasma mass spectrometry (ICP-MS) was developed for the simultaneous determination of Sb(III) and Sb(V) in aqueous environmental samples. For this purpose a chelating resin [1,5-bis(2-pyridyl)-3-sulfophenyl methylene] thiocarbonohydrazide immobilised on aminopropyl-controlled pore glass (550 A, PSTH-cpg) and an anion exchanger (Amberlite IRA-910) were used. A three column system was accordingly designed, using the two adsorbents in tandem, for the separation and preconcentration of the antimony species. The method was developed on the basis of selective sorption of Sb(III) on PSTH-cpg resin. After removal of Sb(III) by PSTH-cpg, Sb(V) was collected on Amberlite. The effects of chemicals and flow variables were investigated. The optimized operating conditions were: sample pH 8.4, a sample flow rate of 1.1 mL min−1, an eluent flow rate of 1.3 mL min−1, and an eluent 0.04% thiourea in 5% HNO3. The relative standard deviations (n = 10) were 4.6% for Sb(III) and 3.0% for Sb(V), demonstrating a good precision for the analysis. The enrichment factors for Sb(III) and Sb(V) were 5.5 and 3.9, respectively. Detection limits (2 min sample loading time) were 0.013 µg L−1 for Sb(III) and 0.021 µg L−1 for Sb(V).The accuracy of the proposed method was checked with two certified reference materials (CRMs): SLRS-5 River Water and TMDA-54.4 Fortified Lake Water. Values obtained were in accordance with those reported for the certified materials. Recovery was found to be in the range of 97–105% for a suite of seawater samples collected in Malaga, Spain.

On-line preconcentration using chelating and ion-exchange minicolumns for the speciation of chromium(III) and chromium(VI) and their quantitative determination in natural waters by inductively coupled plasma mass spectrometry

There are only a few analytical techniques available that have sufficient sensitivity and selectivity for the determination and speciation of chromium in environmental waters. In this work, a non-chromatographic system is developed for the simultaneous determination of chromium(III) and chromium(VI) by solid phase extraction and inductively coupled plasma mass spectrometry (ICP-MS). The system is based on the use of three minicolumns packed, respectively, with chelating and anionic ion exchange resins, which were placed in the injection valve of a simple flow manifold. By using this device, diverse advantages are attained: speciation and simultaneous determination of Cr(III) and Cr(VI) as well as increase of the sensitivity and reduction of the interferences by the preconcentration. The effects of chemicals and flow variables were investigated. Detection limits (2 min sample loading time) were 0.009 μg L−1 for Cr(VI) and 0.03 μg L−1 for Cr(III). The relative standard deviations (n = 10) for 0.3 μg L−1 of Cr(VI) and Cr(III) were 3.2% and 2.6%, respectively, demonstrating a good precision for the analysis. The accuracy of the proposed method was checked with certified reference materials. Values obtained were in accordance with those reported for the certified materials. The method was applied to the determination of chromium species in different seawater samples.

On-line solid-phase chelation for the determination of six metals in sea-water by inductively coupled plasma mass spectrometry

An automated low pressure flow analysis method with on-line column pre-concentration/inductively coupled plasma mass spectrometry (ICP-MS) was developed for the simultaneous determination of cobalt, chromium, cadmium, manganese, zinc and nickel in aqueous environmental samples. The system is based on cationic retention of the analytes onto a mini-column filled with silica gel functionalised with 1-(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 as a compromise between sensitivity and analytical frequency were: sample pH 8.6, sample flow rate of 1.4 mL min−1, eluent flow rate of 1.3 mL min−1, and eluent (HNO3) concentration of 2% (m/m). The relative standard deviation (n = 5), enrichment factor and linear working range were 0.3–4.0%, 2.3–32.9 and 0.02–60 μg L−1, respectively. Detection limits (3 min sample loading time) were between 0.006 and 0.530 μg L−1. The accuracy of the proposed method was checked with two certified reference materials (CRMs) of sea water SLEW 3 and NASS-5 and with two natural waters SLRS-4 and TMDA-54.4. Values obtained were in accordance with those reported for the certified materials. Recovery was found to be in the range of 93–110% for a suit of water samples with variable matrices (seawater and river water) collected in Malaga, Spain.

Determination of antimony, bismuth and tin in natural waters by flow injection solid phase extraction coupled with online hydride generation inductively coupled plasma mass spectrometry

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%.

High resolution continuum source atomic absorption spectrometry and solid phase extraction for the simultaneous separation/preconcentration and sequential monitoring of Sb, Bi, Sn and Hg in low concentrations

A rapid method was developed for separation, pre-concentration and sequential determination of antimony, bismuth, tin and mercury by flow injection solid phase extraction coupled with on-line chemical vapor generation electrothermal atomic absorption spectrometry. The system is based on chelating/cationic retention of the analytes onto a mini-column filled with a mesoporous silica functionalized with 1,5 bis(di-2-pyridyl)methylene thiocarbohydrazide. Several variables (sample flow rate, eluent flow rate, eluent concentration and reductant concentration) were considered as factors in the optimization process. Interactions between analytical factors and their optimal levels were investigated using three central composite designs. The optimized operating conditions were: sample pH = 2.2, sample flow rate 3 mL min−1, eluent flow rate 2.5 mL min−1, eluent 3.1% HCl for Sb, Bi and Sn, and 4.6% thiourea for Hg, and 0.6% NaBH4 reductant. The optimum conditions established were applied to the determination of Sb, Bi, Sn and Hg in sea water and river water by flow injection solid phase extraction coupled with on-line chemical vapor generation high resolution continuum source electrothermal atomic absorption spectrometry (FI-SPE-CVG-CS ETAAS). For the quality control of the analytical performance and the validation of the newly developed method, the analysis of two certified samples, TM 24.3 and TMDA 54.4, Fortified Lake Waters was addressed. The results showed good agreement with the certified values.

Use of a new enrichment nanosorbent for speciation of mercury by FI-CV-ICP-MS

A new enrichment nanosorbent based on mesoporous silica functionalized with 1,5-bis(2-pyridyl) methylene thiocarbohydrazide was synthesized and characterized. From the study of its adsorption capacity toward metal ions, it was observed that Hg2+ is one of the elements with higher adsorption capacity on the nanosorbent, 173.1 μmol g−1 at pH 5. Thus, a flow injection solid phase extraction and cold vapor generation method for its determination and speciation based on the use of this new chelating nanosorbent was optimized. The method developed has been shown to be useful for the automatic pre-concentration and sequential determination of mercury and methylmercury in environmental and biological samples. The system was based on chelating retention of the analytes on a mini-column filled with the new nanosorbent and their sequential elution by using two different eluents, 0.2% HCl for CH3Hg+ and 0.1% thiourea in 0.5% HCl for Hg2+. The determination was performed using inductively coupled plasma mass spectrometry. Under the optimum conditions and 120 s preconcentration time, the enrichment factors were 4.7 and 11.0, the detection limits (3σ) were 0.002 and 0.004 μg L−1, the determination limits (10σ) were 0.011 and 0.024 μg L−1, and the precisions (calculated for 10 replicate determinations at a 2 μg L−1 standard of both species) were 2.8 and 2.6% (RSD); for CH3Hg+ and Hg2+, respectively. Linear calibration graphs were obtained for both species from the determination limits to at least 70 μg L−1. For the quality control of the analytical performance and the validation of the newly developed method, the analyses of two certified samples, LGC 6016 estuarine water and SRM 2976 mussel tissue, were performed. The results showed good agreement with the certified values. Also the method was successfully applied to the speciation of mercury in sea-water samples collected in the Malaga Bay.

On-line separation and sequential determination of trace amounts of heavy metals in biological materials by flow injection inductively coupled plasma atomic emission spectrometry

A flow injection inductively coupled plasma atomic emission spectrometric method for the sequential determination of trace amounts of heavy metals (Cd, Co, Cu and Zn) in biological samples is described based on the complexation of the metal ions with 1,5-bis (di-2-pyridyl) methylene thiocarbohydrazide and its subsequent on-line extraction into isobutyl methyl ketone. A systematic study was performed to determine the optimum conditions for the continuous extraction of the metals. Detection limits for Cu, Co, Zn and Cd ranged from 1.1 to 23.0 ng ml–1 with precision varying from 1.2 to 3.7% relative standard deviation at 100 ng ml–1. These values were obtained under simultaneous multi-element conditions. The effect of various foreign ions on the determination of these metals by the proposed method was examined under the optimum working conditions. The tolerance limits found showed that they can be determined in the presence of a variety of ions including most of those that commonly occur with them in natural samples. Accuracy and matrix interference were confirmed by standard additions and use of certified reference materials.