A. García de Torres

Determination of cadmium in water by ICP-AES with on-line adsorption preconcentration using DPTH-gel and TS-gel microcolumns.

Two flow injection inductively coupled plasma atomic emission spectrometric methods for the preconcentration and determination of trace amounts of cadmium in sea-water and waste-water samples are described based on the adsorption of the metal ion on a micro-column placed in the injection valve of the FI manifold and packed with silica gel funtionalised with 1,5-bis(di-2-pyridyl) methylene thiocarbohydrazide (DPTH-gel) and silica gel functionalised with methylthiosalicylate (TS-gel), respectively. Various parameters and chemical variables affecting the preconcentration and determination of this metal by ICP-AES are evaluated. The DPTH-gel preconcentration method has a linear calibration range from 5 to at least 100 ng ml(-1) of cadmium, with a R.S.D. of 1.1% for ten independent analyses of 100 ng ml(-1), a detection limit of 1.1 ng ml(-1) and a throughput of 40 samples per hour using a 60 s preconcentration time. The TS-gel preconcentration method shows a linear range between 10 and 100 ng ml(-1), with a R.S.D. of 2.5% for ten independent analyses of 100 ng ml(-1), a detection limit of 4.3 ng ml(-1) and a sample throughput of 24 samples per hour for a preconcentration time of 120 s. Validation was carried out against a certified reference water sample and by determining the analyte content in spiked synthetic sea-water, sea-water and waste-water.

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.

On-line preconcentration of mercury by sorption on an anion-exchange resin loaded with 1,5-bis[(2-pyridyl)-3-sulphophenyl methylene] thiocarbonohydrazide and determination by cold-vapour inductively coupled plasma atomic emission.

Abstract 1,5-Bis[(2-pyridyl)-3-sulphophenyl methylene] thiocarbonohydrazide (PSTH) immobilized on an anion-exchange resin (Dowex) has been used for the on-line preconcentration of mercury from biological samples and waters prior to its determination by inductively coupled plasma atomic emission spectroscopy. The metal was eluted from the column using a solution of 2 M HNO3 and mixed on-line with SnCl2. The optimum experimental conditions were evaluated for the continuous preconcentration of Hg, the direct generation of mercury vapour and the final determination of this element by ICP–AES. The enrichment, together with low blank levels of the optimized procedure, allow the simple determination of this toxic element at concentrations down to a few nanograms per milliliter. The proposed method has a linear calibration range 5–1000 ng ml−1 of mercury, with a detection limit of 4 ng ml−1 (S/N=3) and a sampling rate of 40 h−1, investigated with a 9 ml sample volume. The precision of the method (evaluated as the relative standard deviation obtained after analyzing ten series of ten replicates) was ±3.6% at the 10 ng ml−1 level of Hg(II) and ±1.3% at the 100 ng ml−1 level. The accuracy of the method was examined by the analysis of certified reference materials.

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.

Use of flow injection cold vapour generation and preconcentration on silica functionalized with methylthiosalicylate for the determination of mercury in biological samples and sea-water by inductively coupled plasma atomic emission spectrometry

A novel and expeditious approach to the direct determination of mercury in sea-water and biological samples based on a separation–preconcentration system coupled on-line to a flow injection (FI) manifold is described. The method employs on-line preconcentration of mercury on a 3 cm×3 mm column packed with silica gel functionalized with methylthiosalicylate (TS-gel) and placed in the injection valve of the FI manifold. Synthesis of the resin is simpler and faster than that of other resins described previously, where many steps are required. In this system the metal was eluted from the column with thiourea and mixed on-line with NaBH4; mercury vapour was generated directly and separated via a gas–liquid separator. Various parameters and chemical variables affecting the preconcentration of HgII, the direct generation of mercury vapour and the final determination by ICP-AES were evaluated. The calibration graph was linear over the range 5–1000 ng ml–1 HgII, with a relative standard deviation at the 10 ng ml–1 level of 2.1%. The accuracy of the method was evaluated by the analysis of certified reference materials. The results showed good agreement with the certified values.

Simultaneous determination of iron, cobalt, nickel and copper by UV-visible spectrophotometry with multivariate calibration.

A method for the simultaneous spectrophotometric determination of the divalent ions of iron, cobalt, nickel and copper based on the formation of their complexes with 1,5-bis(di-2-pyridylmethylene) thiocarbonohydrazide (DPTH) is proposed. The resolution of quaternary mixtures of these metallic ions was accomplished by several chemometric approaches. A comparative study of the results obtained for simultaneous determinations in mixture by using principal component regression (PCR) and partial least-squares regression (PLS-1 and PLS-2) for absorbance, first-derivative and second-derivative data is presented. In general, the best recovery values are obtained by the PLS-2 method for absorbance data. This procedure allows the simultaneous determination of the cited ions in alloys and biological materials Good reliability of the determination was proved.

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.

Automated on-line separation-preconcentration system for platinum determination by electrothermal atomic absorption spectrometry

A flow injection on-line sorption preconcentration system for the electrothermal atomic absorption spectrometric determination of platinum has been developed. The method employs on-line preconcentration of platinum on a column packed with silica gel functionalised with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide (DPTH-gel) placed in the autosampler arm. The modification of the autosampler in the tubing line and circuit allowed either the flow of the sample through the column or the operation of the autosampler in the normal mode, where microlitres of 2 M HNO3, which acts as the elution agent, pass through the microcolumn eluting Pt(IV), which is directly deposited in the graphite tube as a drop of a precisely defined volume. An enrichment factor of 41.7 and a 3σ detection limit of 0.8 ng ml −1 along with a sampling frequency of 29 h −1 are achieved with 60 s preconcentration time at a sample flow rate of 2.4 ml min −1 . The relative standard deviation is 1.6% for 4 ng ml −1 Pt (n = 11). The method has been applied to the determination of platinum in catalyst, vegetation, soil and water samples.

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.