New magnetic chelating sorbent for chromium speciation by magnetic solid phase extraction on-line with inductively coupled plasma optical emission spectrometry.

A novel sorbent material employing magnetic nanoparticles (MNPs) coupled to graphene oxide (GO) functionalized with 4-aminobenzenesulfonic acid (M@GO-ABS) has been synthesized and applied to develop an inexpensive and automatic method for Cr(III) and Cr(VI) speciation in environmental samples; the developed method combines inductively coupled plasma optical emission spectrometry (ICP-OES) with on-line magnetic solid phase extraction (MSPE). Two magnetic-knotted reactors containing M@GO-ABS were installed in the eight-port injection valve of a flow injection (FI) manifold. Two different eluents were used, one for Cr(VI) (the most toxic chromium species) and one for total Cr concentration. Cr(III) concentration was calculated by the difference between Cr(VI) concentration and total Cr concentration. The optimized method presented detection limits (LOD, peak height) of 0.1 µg L-1 for chromium (VI) and 0.08 µg L-1 for total chromium, and enrichment factors of 15 and 23, respectively. Certified reference materials (TMDA 54.5 fortified lake water and SPS-SW2 surface water) and spiked aqueous samples were used to validate the developed method. The developed method was fruitfully applied to chromium speciation in environmental water samples such as seawater, well water and tap water collected in Málaga (Spain). The obtained values were in good agreement with the certified values, and the recoveries were found in the range of 91-108% for the spiked samples.

Semiautomatic method for the ultra-trace arsenic speciation in environmental and biological samples via magnetic solid phase extraction prior to HPLC-ICP-MS determination.

A novel magnetic functionalized material based on graphene oxide and magnetic nanoparticles (MGO) was used to develop a magnetic solid phase extraction method (MSPE) to enrich both, inorganic and organic arsenic species in environmental waters and biological samples. An automatic flow injection (FI) system was used to preconcentrate the arsenic species simultaneously, while the ultra-trace separation and determination of arsenobetaine (AsBet), cacodylate, AsIII and AsV species were achieved by high performance liquid chromatography combined with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The sample was introduced in the FI system where the MSPE was performed, then 1 mL of eluent was collected in a chromatographic vial, which was introduced in the autosampler of HPLC-ICP-MS. Therefore, preconcentration and separation/determination processes were automatic and conducted separately. To the best of our knowledge, this is the first method combining an automatic MSPE with HPLC-ICP-MS for arsenic speciation, using a magnetic nanomaterial based on MGO for automatic MSPE. Under the optimized conditions, the LODs for the arsenic species were 3.8 ng L-1 AsBet, 0.5 ng L-1 cacodylate, 1.1 ng L-1 AsIII and 0.2 ng L-1 AsV with RSDs <5%. The developed method was validated by analyzing Certified Reference Materials for total As concentration (fortified lake water TMDA 64.3 and seawater CASS-6 NRC) and also by recovery analysis of the arsenic species in urine, well-water and seawater samples collected in Málaga. The developed method has shown promise for routine monitoring of arsenic species in environmental waters and biological fluids.

Direct solid sampling for speciation of Zn2+ and ZnO nanoparticles in cosmetics by graphite furnace atomic absorption spectrometry.

The application of nanoparticles (NPs) in science and technology is a fast growing field. Therefore, reliable and straightforward analytical methods are required for their fast determination in different types of samples. This work investigates a method that enables the determination of ZnO NPs, discriminating them from ionic zinc in cosmetic samples. The method is based on direct solid sampling high-resolution continuum source electrothermal atomic absorption spectrometry (SS-HR-CS-GFAAS), and has been applied to determination of ZnO NPs, Zn2+ and total Zn in eye shadow samples. In this work the deconvolution of the atomization peak and the calibration by standard additions have been done in order to discriminate and quantify ionic zinc and ZnO NPs. A Zn wavelength with low sensitivity was selected. The proper optimization of the graphite furnace temperature program, minimizing the mineralization of the sample matrix, enables different atomization profiles between the different chemical species of the analyte. Two multiple response surface designs have been used in order to optimize the adequate furnace program to achieve our aims. All the optimization experiments were performed using a sample of eye shadow. Further, a method for the determination of total Zn by direct solid sampling with calibration by aqueous standards, was also optimized. The optimized method was successfully applied to the determination of ionic Zn and ZnO NPs in different eye shadow samples, and has been validated by recovery assays, obtaining recovery percentages between 80 and 125%. Total Zn concentration in the solid samples was validated by the determination of total Zn by direct solid sampling and by the analysis of the same eye shadow samples digested in microwave oven.

Speciation analysis of inorganic arsenic by magnetic solid phase extraction on-line with inductively coupled mass spectrometry determination.

Arsenic, one of the main environmental pollutants and potent natural poison, is a chemical element that is spread throughout the Earth's crust. It is well known that the toxicity of arsenic is highly dependent on its chemical forms. Generally, the inorganic species are more toxic than its organics forms, and As(III) is 60 times more toxic than As(V). In environmental waters, arsenic exists predominantly in two chemical forms: As(III) and As(V). In view of these facts, fast, sensitive, accurate and simple analytical methods for the speciation of inorganic arsenic in environmental waters are required. In this work, a new magnetic solid phase extraction with a hydride generation system was coupled on line with inductively coupled plasma mass spectrometry (MSPE-HG-ICP-MS). The new system was based on the retention of As(III) and As(V) in two knotted reactors filled with (Fe3O4) magnetic nanoparticles functionalized with [1,5-bis (2-pyridyl) 3-sulfophenylmethylene] thiocarbonohydrazide (PSTH-MNPs). As(III) and total inorganic As were sequentially eluted in different reduction conditions. The concentration of As(V) was obtained by subtracting As(III) from total As. The system runs in a fully automated way and the method has proved to have a wide linear range and to be precise, sensitive and fast. The detection limits found were 2.7 and 3.2 ng/L for As(III) and total As, respectively; with relative standard deviations (RSDs) of 2.5% and 2.7% and a sample throughput of 14.4 h-1. In order to validate the developed method, several certified reference samples of environmental waters including sea water, were analyzed and the determined values were in good agreement with the certified values. The proposed method was successfully applied to the speciation analysis of inorganic arsenic in well-water and sea water.

Simultaneous determination of V, Ni and Fe in fuel fly ash using solid sampling high resolution continuum source graphite furnace atomic absorption spectrometry.

A green and simple method has been proposed in this work for the simultaneous determination of V, Ni and Fe in fuel ash samples by solid sampling high resolution continuum source graphite furnace atomic absorption spectrometry (SS HR CS GFAAS). The application of fast programs in combination with direct solid sampling allows eliminating pretreatment steps, involving minimal manipulation of sample. Iridium treated platforms were applied throughout the present study, enabling the use of aqueous standards for calibration. Correlation coefficients for the calibration curves were typically better than 0.9931. The concentrations found in the fuel ash samples analysed ranged from 0.66% to 4.2% for V, 0.23-0.7% for Ni and 0.10-0.60% for Fe. Precision (%RSD) were 5.2%, 10.0% and 9.8% for V, Ni and Fe, respectively, obtained as the average of the %RSD of six replicates of each fuel ash sample. The optimum conditions established were applied to the determination of the target analytes in fuel ash samples. In order to test the accuracy and applicability of the proposed method in the analysis of samples, five ash samples from the combustion of fuel in power stations, were analysed. The method accuracy was evaluated by comparing the results obtained using the proposed method with the results obtained by ICP OES previous acid digestion. The results showed good agreement between them. The goal of this work has been to develop a fast and simple methodology that permits the use of aqueous standards for straightforward calibration and the simultaneous determination of V, Ni and Fe in fuel ash samples by direct SS HR CS GFAAS.

Synthesis and characterization of a novel mesoporous silica functionalized with [1,5 bis(di-2-pyridyl)methylene thiocarbohydrazide] and its application as enrichment sorbent for determination of antimony by FI-HG-ETAAS.

A simple, sensitive, low-cost and rapid flow injection (FI) on-line sorption preconcentration/hydride generation system has been synchronously coupled to an electrothermal atomic absorption spectrometer (ETAAS) for the determination of trace amounts of Sb in aqueous environmental samples (river and sea water samples). The system is based on retention of the analyte onto a micro-column filled with a novel mesoporous silica functionalised with [1,5 bis(di-2-pyridyl) methylene] thiocarbohydrazide placed in the injection valve of the FI manifold. The adsorption capacity of the resin for Sb was found to be 160.8 µmol g(-1). Chemicals and flow variables affecting the continuous preconcentration of antimony, the direct generation of antimony hydride and the final determination of this element by ETAAS were evaluated. The optimized operating conditions selected were: sample pH 5.0, sample flow rate 2.5 ml min(-1), eluent flow rate 5.4 ml min(-1), eluent 2.0% thiourea in 4.0% nitric acid. Under the optimum conditions, the calibration graph obtained was linear over the range 0.025-2.5 µg L(-1). At a sample frequency of 20 h(-1) and 120 s preconcentration time, the enrichment factor was 22. The detection limit of the method (3Æ¡) was 1 ng L(-1) for a 5.0 mL sample volume and the precision was 0.9% (RSD) for 11 replicate determinations at 1.0 µg L(-1) Sb. The preconcentration factor and detection limit can be improved by increasing the preconcentration time, which can be increased at least up to 5 min. The accuracy of the proposed method was demonstrated by analyzing two certified reference materials and by determining the analyte content in spiked environmental water samples. The results obtained using this method were in good agreement with the certified values of the standard reference materials and the recoveries for the spiked river and sea water samples were 91.3-109.9%.

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.

Quantitative determinations of SiC and SiO2 in new ceramic materials by Fourier transform infrared spectroscopy.

Silicon carbide-based biomorphic ceramics have been fabricated by the pyrolysis and infiltration of natural wood (mukali and pine) with molten silicon. The results of the process of synthesis have been studied in this and other biomorphic ceramics using thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) analysis and scanning electron microscopy (SEM). For evaluating the yield of the synthesis, a new method by Fourier transform infrared spectrometry (FTIR) has been developed for the direct determination of SiC and the simultaneous determination of SiC and SiO2 by absorbance measurements in KBr pellets. The procedure was based on the use of the ratio between the absorbance of the characteristic band of silicon carbide or silica and those of an acetate internal standard added to samples. A multivariate calibration strategy based on inverse least squares and the standard addition approach were employed for quantification. The results obtained for all biomorphic ceramics studied and synthetic samples prepared by mixing pyrolyzed wood with pure SiC were satisfactory. The relative standard deviation for all samples was lower than 2.9%.

Lead ultra-trace on-line preconcentration and determination using selective solid phase extraction and electrothermal atomic absorption spectrometry: applications in seawaters and biological samples.

In this work, a new chelating resin [1,5-bis (2-pyridyl)-3-sulphophenyl methylene] thiocarbonohydrazide immobilised on aminopropyl-controlled pore glass (550 A; PSTH-cpg) was synthesised and packed in a microcolumn which replaced the sample tip of the autosampler arm. The system was applied to the preconcentration of lead. When microliters of 10% HNO3, which acts as elution agent, pass through the microcolumn, the preconcentrated Pb(II) is eluted and directly deposited in a tungsten-rhodium coated graphite tube. With the use of the separation and preconcentration step and the permanent modifiers, the analytical characteristics of the technique were improved. The proposed method has a linear calibration range from 0.012 to 10 ng ml(-1) of lead. At a sample frequency of 36 h(-1) with a 90 s preconcentration time, the enrichment factor was 20.5, the detection and determination limits were 0.012 and 0.14 ng ml(-1), respectively and the precision, expressed as relative standard deviation, was 3.2% (at 1 ng ml(-1)). Results from the determination of Pb in biological certified reference materials were in agreement with the certified values. Seawaters and other biological samples were analysed too.

Automatic on line preconcentration and determination of lead in water by ICP-AES using a TS-microcolumn.

A simple, sensitive, low-cost and rapid, flow injection system for the on-line preconcentration of lead by sorption on a microcolumn packed with silica gel funtionalized with methylthiosalicylate (TS-gel) was developped. The metal is directly retained on the sorbent column and subsequently then eluted from it by EDTA. Five variables (sample flow rate, eluent flow rate, eluent concentration, pH and buffer concentration) were considered as factors in the optimization process. Interactions between analytical factors and their optimal levels were investigated using two level factorial and Box-Behnken designs. The optimum conditions established were applied to the determination of lead by flow injection inductively coupled plasma atomic emission spectrometry (FI-ICP-AES). The proposed method has a linear calibration range from 10 to at least 500ngml(-1) of lead. At a sample frequency of 24h(-1) and a 120s preconcentration time, the enrichment factor was 41, the detection limit was 15.3ngml(-1) (S/N=3) and the precision, expressed as relative standard deviation, was 0.9% (at 100ngml(-1)). Validation of the developed method was carried out against electrothermal atomic absorption spectrometry analysis without statistically significant differences between the proposed method and the atomic absorption method.

Automatic determination of cobalt at the submicrogram per millilitre level using a flowthrough spectrophotometric sensor.

A flowthrough spectrophotometric sensor for the determination of cobalt at the nanogram per millilitre level using pyridoxal 4-phenylthiosemicarbazone as reagent and integrated preconcentration and detection in the flow cell is proposed. The method is highly selective for cobalt(II); it features detection and determination limits of 0.02 and 0.06 mug ml(-1) respectively, and a linear range of at least 0.04-18 mug ml(-1). The method is subject to very few interferences because the strongly acidic medium used prevents the formation of most complexes of the reagent with other metal ions. The method was applied to the determination of cobalt in pharmaceutical preparations.

Determination of trace heavy metals in biological samples by inductively-coupled plasma atomic emission spectrometry after extraction with 1,5-bis-(di-2-pyridylmethylene)thiocarbonohydrazide.

A sensitive inductively-coupled plasma atomic emission spectrometric sequential method for the determination of trace heavy metals (cadmium, cobalt, copper and nickel) in biological samples after extraction of the metals into isobutyl methyl ketone (IBMK) containing 1,5-bis-(di-2-pyridylmethylene)thiocarbonohydrazide (DPTH) is described. A systematic study was made to determine the optimum conditions for extraction of the metals into IBMK. The complexes formed are quite soluble in IBMK, so much so that this allows the use of aqueous-to-organic phase volume ratios of up to 40 and hence the determination of concentrations down to 40 times lower than those afforded by the direct non-extractive method. The method has been used for the determination of these elements in various biological materials with good results.

Determination of nickel in biological materials after microwave dissolution using inductively coupled plasma atomic emission spectrometry with prior extraction into butan-1-ol.

A sensitive procedure has been developed for the determination of ultratrace amounts of nickel in biological materials by inductively coupled plasma atomic emission spectrometry after extraction of the nickel ion into butan-1-ol by using 1,5-bis(di-2-pyridylmethylene)thiocarbonohydrazide as the extracting reagent. Fast, efficient and complete sample digestion is achieved by an HNO3-HCl poly(tetrafluoroethylene) bomb dissolution technique using microwave heating. Results obtained for eleven certified reference materials agreed with the certified values.