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

Mercury is one of the most toxic environmental pollutants and its effects on human and ecosystem health are well known. All mercury species are toxic, with organic mercury compounds generally being more toxic than inorganic species. Chromatography techniques (GC, HPLC) coupled to element specific detectors, are able to separate mercury species in order to elucidate mercury transformation and transport processes where the determination of all mercury species is desirable. However, in practice, especially in sampling campaigns for sea water analysis where a large number of samples are collected over a longer period of time, a combination of methods is usually applied to accurately determine the most toxic mercury species. These include non-chromatographic methods based on the different chemical and/or physical behavior of the mercury species. These non-chromatographic methods can be less time consuming, more cost effective and available, and present competitive limits of detection. Especially when mercury could vapor (CV) generation technique is employed, which reduces salt effect on the analytical signal and improve the sensibility. Among non-chromatographic methods, solid phase extraction and microextraction (SPE and SPME) which is becoming increasingly popular for sample preparation in organic analysis, found its way to speciation analysis of organometals. SPE/SPME is the most popular sample preconcentration method for its simplicity, high enrichment factor, low or no consumption of organic solvents and feasibly to be automated. On the other hand, the exploration of new materials, especially nanometer sized materials, as the support phase is another active research area in SPE/SPME for mercury determination. The use of nanoparticles leads to higher extraction capacity/efficiency and rapid dynamics of extraction originated from the higher surface area to volume ratio and short diffusion route. In this work, a new enrichment nanosorbent functionalized with 1,5 bis (2-pyridyl) methylene thiocarbohidrazide was synthesized and characterized. From the study of its adsorption capacity toward metal ions, Hg2+ was observed to be one of the most retained 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 showed to be useful for the automatic pre-concentration and sequential speciation of mercury and methylmercury in environmental and biological samples. The system was based on chelating retention of the analytes onto 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 analysis of two certified samples, LGC 6016 estuarine water and SRM 2976 mussel tissue were addressed. The results showed good agreement with the certified values. The method was successfully applied to the speciation of mercury in sea-water samples collected in the Málaga Bay.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Synthesis and characterization of a new nanosorbent based on functionalized magnetic nanoparticles and its use in the determination of mercury by FI-CV-ETAAS

In this work, a new chelating sorbent which employs 1,5-bis(di-2-pyridil)methylene thiocarbohydrazide as the functional group and magnetic nanoparticles (MNPs) as its support (DPTH-MNP) was synthetized and characterized. The MNPs were prepared by coprecipitation of Fe+2 and Fe+3 with NH3 and then coated with silica in order to easily bind the support and the functionalizing molecule. The aim of the synthesis of this material is applying it as a solid-phase extracting agent and evaluating its potential for the extraction and pre-concentration of trace amounts of analytes present in biological and environmental samples with on-line methods. The MNPs’ magnetic core would allow overcoming the usual backpressure problems that happen in solid-phase extraction methods thanks to the possibility of immobilizing the MNPs by applying an external magnetic field. From the study of its adsorption capacity toward metal ions, mercury and antimony were the most retained. Thus, a flow injection solid phase extraction and cold vapor generation method for mercury determination based on the use of this new chelating nanosorbent was optimized. The greatest efforts were put into the reactor design to minimize compaction and loss of nanosorbent. The knotted reactor shown in Figure 1 was chosen as the best. Then, chemical and flow variables were optimized by Central composite designs (CCDs). The method developed has showed to be useful for the automatic pre-concentration and determination of mercury in environmental and biological samples. The determination was performed using electrothermal atomic absorption spectrometry (ETAAS). Under the optimum conditions, pH 5 and 120 s preconcentration time, the enrichment factor was 5.33; the detection limit (3σ) was 7.8 ng L-1; the determination limit (10σ) was 99 ng L-1; and the precisions (calculated for 10 replicate determinations at a 1 and 5 µg L-1 standards) were 1.7 and 1.9 % (RSD), respectively. Two linear calibration graphs were obtained, from the determination limits to 10 µg L-1 and from 10 to at least 50 µg L-1. From the comparison with other similar methods found in the bibliography, the detection limit and precisions calculated with our method were better. In order to evaluate the accurate and applicability of the method, the analysis of five certified samples LGC 6016 estuarine water, TMDA 54.4 fortified lake water, SRM 2976 mussel tissue, TORT-1 lobster hepatopancreas and DOLT-1 dogfish liver by standard addition and external calibration, were addressed. The results showed good agreement between the certified values, or added amounts of mercury, and the found concentrations. The method was successfully applied to the determination of mercury in sea-water samples collected in the Málaga Bay.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Simultaneous determination of traces of PT, PD, OS, IR, RH, AG and AU by using magnetic nanoparticles solid phase extraction coupled with ICP OES

The direct analysis of these target analytes is very limited being essential sample pre-treatment techniques and the use of very sensitive instrumental techniques to carry out determinations. The inductively coupled plasma optical emission spectrometry shows a poor sensitivity because the concentration of some elements in environmental samples is below the detection limit of ICP OES. To solve this problem, preconcentration separation procedures have been proposed, minimizing the spectral and matrix interferences. Thus, enrichment is a very important issue for achievement of low detection limits [1-4]. In this study, a chelating resin 1,5 bis (di 2 pyridil) methylene thiocarbonohydrazide bonded to iron oxide magnetic nanoparticles (DPTH-MNPs) were synthesized. These magnetic nanoparticles were employed as a solid phase extraction (SPE) adsorbent for the separation and concentration of trace amounts of 7 elements (Au, Ag, Pd, Pt, Ir, Rh and Os) from environmental water samples. The main aim of this work was to develop a precise and accurate method for the simultaneous determination of the maximum possible number of elements by using this new absorbent and a multimode sample introduction system (MSIS). The MSIS acts as a system for the generation, separation and introduction of chemical vapours (CVG) and also as an introduction system for sample aerosols, in a simultaneous form, into an inductively coupled plasma-optical emission spectrometer. The on-line SPE-CVG-ICP-OES system developed was applied in the determination of the aforementioned metals in natural water samples (sea water, estuarine, lake and river water), with the least demanding and simple sample preparation procedure. The developed method was validated by analysing natural water certified reference materials (TMDA 54.4 fortified lake waters and SRM 1643e, trace elements in water; and National Institute of Standards and Technology (NIST), NIST-2557 autocatalyst). Sea water, tap water and well water samples collected from Malaga (Spain) were also analysed. The procedure has been demonstrated to be fast, easy, automatic, selective and economical, and the sensitivity was good. The main advantage of DPTH-MNPs is its very good stability and resistance because chemisorption of chelating molecules on the surface of solid supports provides immobility, mechanical stability and insolubility. The precision (RSD), accuracy (by standard addition or recovery) and limit of detection (LOD) were used to evaluate the characteristics of the procedure. Furthermore, the proposed method was applied in the simultaneous determination of the 7 elements mentioned above with a sample throughput of about 13 h-1, thereby, reducing the time of analysis and the volume of reagents and sample required. References [1] M. Tuzen, M. Soylak, D. Citak, H.S. Ferreira, M.G.A. Korn, M.A. Bezerra, A pre-concentration system for determination of copper and nickel in water and food samples employing flame atomic absorption spectrometry, Journal of Haz-ardous Materials 162 (2009) 1041–1045. [2] Y. Cui, X. Chang, Y. Zhai, X. Zhu, H. Zheng, N. Lian, ICP-AES determination of trace elements after preconcentrated with p-dimethylaminobenzaldehyde-modified nanometer SiO2 from sample solution, Microchem. J. 83 (2006) 35–41. [3] P. Liang, B. Hu, Z. Jiang, Y. Qin, T. Peng, Nanometer-sized titanium dioxide micro-column on-line preconcentration of La, Y, Yb, Eu, Dy and their determination by inductively coupled plasma atomic emission spectrometry, J. Anal. Atom. Spectrom. 16 (2001) 863–866. [4] B. Feist, B. Mikula, K. Pytlakowska, B. Puzio, F. Buhl, Determination of heavy metals by ICP-OES and F-AAS after preconcentration with 2,2-bipyridyl and erythrosine, J. Hazard. Mater. 152 (2008) 1122–1129.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Sequential determination of traces of As, Sb and hg by on-line magnetic solid phase extraction coupled with Hr-Cs-Cvg-Gfaas

A green and rapid method was developed for the simultaneous separation/preconcentration and sequential monitoring pf arsenic, antimony and mercury by flow injection magnetic solid phase extraction coupled with on-line chemical vapor generation and determination by high resolution continuum source graphite furnace atomic absorption spectrometry. The system is based on chelating/cationic retention of the analytes onto a magnet based reactor designed to contain functionalized magnetic nanoparticles (MNPs). The MNP score allows overcoming the back-pressure problems that usually happen in SPME methods with NPs thanks to the possibility of inmobilizing the MNPs by applying an external magnetic field. Several chemical and flow variables were considered as factors in the optimization process using central composite designs. With the optimized procedure the detection limits obtained were 0.2, 0.003 and 0.4 µg/L for As, Sb and Hg respectively. For the quality control of the analytical performance and the validation of the 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.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Cold vapour generation electrothermal atomic absorption spectrometry and solid phase extraction based on a new nanosorbent for sensitive HG determination in environmental samples (sea water and river water)

Reunión bianual del Grupo Regional Andaluz de la Sociedad Española de Química AnalíticaMercury is not an essential element for plant or animal life and it is a potential environmental toxic because of its tendency to form covalent bonds with organic molecules and the high stability of the Hg-C bond. Reports estimate a total mercury concentration in natural waters ranging from 0.2 to 100 ng L-1. Due to this fact, highly sensitive methods are required for direct determination of such extremely low levels. In this work, a rapid and simple method was developed for separation and preconcentration of mercury by flow injection solid phase extraction coupled with on-line chemical vapour generation electrothermal atomic absorption spectrometry. The system is based on chelating retention of the analyte onto the mini column filled with a mesoporous silica functionalized with 1,5 bis (di-2-pyridyl) methylene thiocarbohydrazide. The main aim of this work was to develop a precise and accurate method for the determination of the Hg. Under the optima conditions and 120 s preconcentration time, the detection limit obtained was 0.009 μg L-1, with RSDs 3.7 % for 0.2 μg L-1, 4.8 % for 1 μg L-1 and enrichment factor 4, Furthermore, the method proposed has permitted the determination of Hg with a reduction in the analysis time, the sample throughput was about 18 h-1, low consumption of reagents and sample volume. The method was applied to the determination of Hg in sea water and river water. For the quality control of the analytical performance and the validation of the newly developed method, the analysis of two certified samples, TMDA 54.4 Fortified Lake, and LGC6187 River sediment was addressed. The results showed good agreement with the certified values.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Determination of Pb using F3eO4 GO join to DPTH for ferrofluid based dispersive solid phase extraction

In this work has been described a green and rapid method the synthesis of Fe3O4@GO nanospheres via chemical covalent bonding method. The Fe3O4@GO DPTH was applied to ferrofluid based dispersive solid phase extraction of lead as a model analyte using an ionic liquid carrier. The ferro fluid allows the rapid extraction of lead ions using a low amount of sorbent material. Besides, the magnetic separation greatly improved the separation rate. The presented method is highly time saving due to the high dispersion of the sorbent in the aqueous phase and also there is no need to shake the sample solution. The other benefits of the proposed methods are simplicity of operation, low cost, high sorption capacity, high recovery and high preconcentration. In order to optimize the method the following parameters were studied: sample solution pH, concentration of DPTH, extraction time, amount of sorbent, desorption conditions, influence of ionic strength, and tolerance of potentially interfering ions. The sample or standard solution containing Pb(II), DPTH (0.05% ethanol w/v), NaCl (0.5 %, w/v) and buffer (pH = 5.6) was poured into high volume. Then 240 µL of ferrofluid was injected rapidly into the sample solution through a syringe. Thereupon, a dark cloudy suspension was formed, ferrofluid was dispersed thoroughly in solution and the complex of Pb-DPTH was extracted in a few seconds. Subsequently, a strong magnet was placed at the bottom of the tube to let the extractant settle. After about 3 min, the solution became clear and the supernatant was discarded simply by decanting it. Afterwards, the magnet was removed and 1 mL of nitric acid (2.0 mol L−1) was introduced to the vial to desorb the Pb by sonication. Finally, the sorbent was separated by positioning the magnet to the outside of the tube and the concentration of Pb in acidic aqueous phase was determined by ETAAS.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Sequential determination of heavy metals in environmental water samples by flow injection-chemical vapour generation-inductively coupled plasma mass spectrometry

The toxicity of “heavy metals” has been well recognized for a long time. Often the non-specific term “heavy metals” is used for three of the metals, cadmium, mercury and lead. These have large bioconcentration factors in marine organism, are highly toxic and, unlike many of the transition elements have no known natural biological functions. For these reasons these metals generate the greatest concern for the general public and therefore also for environmental agencies in the majority of states. The monitoring and control of these trace elements in the environment requires powerful analytical methods to accurately characterize their abundance and to reach reliable conclusions. In this work, 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 system (FI-CVG). It is difficult to simultaneously determine these elements by CVG, because their conditions of CVG are different. Thus, the system was based on the use of two minicolumns packed with 1-(di-2-pyridyl)methylene thiocarbonohydrazide 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 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 the Málaga Bay.Universidad de Málaga, Campus de Excelencia Internacional Andalucia Tec

Magnetic dispersive solid phase microextraction coupled with on-line chemical vapor generation method to extraction/preconcentration of mercury from environmental samples and determination by graphite furnace atomic absorption spectrometry.

Mercury (Hg) is classified as priority hazardous substances. Concentrations found in the aquatic environment are at trace levels as result of natural processes, such as erosion and volcanism, and anthropogenic discharges related mainly to industrial and mining activities. Mercury is one of the most potent neurotoxins known, showing a high number of adverse health effects in animals and humans. For this reason, a simple and rapid method for the determination and preconcentration of mercury in environmental waters is proposed. This work is based on magnetic dispersive solid phase microextraction (MDSPME) coupled with on-line chemical vapour generation (CVG). Graphite furnace atomic absorption spectrometry (GFAAS) was employed for the quantification of Hg. In the preconcentration step, a shell structured Fe3O4@graphene oxide was suspended in the ionic liquid carrier (1-n-butyl-3-metilimidazolium tetrafluoroborate [BMIM][BF4]), obtaining a stable colloidal suspension called ferrofluid. This sorbent possesses as large contact surface area and a high density of polar groups on its surface. The nanoparticles, when finely dispersed in the sample solution, result in almost complete extraction of Hg within a few seconds. All experimental and instrumental variables were optimized and the method was adequately validated by the analysis of certified reference materials of environmental waters. Acknowledgements The authors would like to thank Plan Propio “Proyecto Puente” de la Universidad de Málaga for financial support of this work.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

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 chromatog raphy 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/deter mination 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 Malaga. ´ The developed method has shown promise for routine monitoring of arsenic species in environmental waters and biological fluids.This work has been partially supported by the University of Malaga (Proyecto Puente UMA), FEDER funds, Junta de Andalucia, Project UMA18FEDERJA060 and the Spanish Ministerio de Ciencia y Tecnologia (fellowship FPU18/05371). Funding for open access charge: Universidad de Málaga / CBU

Solid sampling determination of ZnO nanoparticles in eyeshadows 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. In this work, a method that enables the determination of the average size of ZnO NPs, besides their concentration, discriminating them from ionic zinc, has been optimized. The method is based on solid sampling high-resolution continuum source electrothermal atomic absorption spectrometry (SS-HR-CS-GFAAS), and has been applied to determination and characterization of ZnO NPs in cosmetic samples. Recently, graphite furnace atomic absorption spectrometry has been introduced as a new tool to determine the size of nanoparticles by evaluation of the following parameters: atomization delay (tad) and atomization rate (kat). In this work both parameters (besides peak area) have been obtained from absorbance signals for a line of Zn with low sensitivity. 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 baby´s skin irritation protective cream. The optimized furnace program is shown in Table 1. Table 1. Optimized furnace program The size calibrations were performed against solid (powered) ZnO standards, from 50-nm to 500-nm sized nanoparticles. The correlation coefficients (R value) of the linear calibration were not worse than 0.9982. The optimized method was tested in other types of cosmetic samples such as eyeshadow samples with good results. The determination of the MNPs’ size was validated by transmission electron microscopy (TEM) and the Zn concentration in the solid samples was validated by atomic fluorescence spectroscopy (AFS). Acknowledgements (optional) [Garamond font, 10 points] The authors would like to thank Plan propio “Proyecto Puente” de la Universidad de Málaga for financial support of this work.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec