Determination of Cadmium in River Water Samples by Flame AAS after On-line Preconcentration in Mini-Column Packed with 2-Aminothiazole-modified Silica Gel

Abstract

Heavy metals (e.g., Cd, Cu, Hg, Pb) at trace levels are proven toxic elements and can be the cause of human health disorders. 1,2 Because the main sources of these metals for humans are water and food, monitoring the heavy metal content in natural waters is of paramount importance.The cadmium contamination in environmental samples is generally lower than 5 ng mL -1 , so very sensitive techniques are required for determinations. Several analytical techniques exist for determining trace levels of cadmium. 3,4 Flow injection preconcentration techniques are useful for application in determining heavy metal ions by flame absorption atomic spectrometry (FAAS), providing a superior performance because they allow for the enhancement of sensitivity, separation of the analyte from the matrix and reduction of the risk of contamination. [5][6][7][8] The Cd 2+ preconcentration with solid phase extraction (SPE) technique using highly selective sorbentpacked columns has been described elsewhere.9-11 Compatible detection limits were obtained by the SPE technique.In recent years, the use of chemically modified silica gel matrixes with attached groups having a selective affinity for metal ions has been described. [12][13][14][15] A manual procedure with this sorbent-packed column has been proposed for Cd preconcentration. 12,15 However, the routine application of this procedure is limited by the time necessary for each analysis (100 min for each determination).This work describes the analytical performance of a flow injection system with online preconcentration on a sorbent minicolumn packed with 2-aminothiazole-modified silica gel (SiAT) for determining Cd in a series of river water samples. The material was initially tested with a synthetic aqueous solution containing Cd 2+ ; after that it was used in real samples. ExperimentalReagents, analytical solutions and samples All the solutions were prepared with high purity chemicals and distilled-deionized water (Milli-Q system, Millipore). The hydrochloric and nitric acids used were of the brand Suprapur quality (Merck).Cadmium standard solutions (5 -50 µg L -1 ) were prepared by stepwise dilution from a 1000 mg L -1 stock solution (Merck Titrisol) with Milli-Q treated water, acidified with nitric acid to pH 2.The mini-column (a 5 cm long, 3 mm i.d. glass tube) was drypacked with 100 mg of SiAT.Samples of river water (Tietê, Parapanema and Parana rivers, SP, Brazil) were collected and immediately filtered through a 0.45 µm membrane. After acidification (pH < 2.0) with 6.0 mol L -1 HNO3 solution, the samples were stored in highly purified PE containers. Aliquots of 100 mL of the water samples were digested by oxidation with UV-photolysis in the presence of 0.01% of H2O2, using a low-pressure Hg-lamp integrated to a closed quartz vessel. 17The aqueous extract resulting was poured into a 100 mL volumetric flask and this solution was diluted to the final volume with deionized water. Imperatriz, MA, Brasil A rapid and sensitive method was developed to determine trace levels of Cd 2+...

Simple synthesis of conducting poly(2-aminothiazole) with high molecular weight

“…It was reported that 2AT and its derivatives demonstrated excellent anticorrosive properties [4] and adsorptive functionalities to heavy metal ions due to the sulfur (S)-and nitrogen (N)-rich subgroups [5,6]. 2AT-modified silica gel and TiO 2 particles were reported to be able to remove heavy metal ions including Ni(II), Cu(II), Cd(II), Zn(II), and Pb(II) from fuel kerosene [7], fuel ethanol [8], and aqueous solutions [9][10][11], respectively. Recently, it was reported that 2AT-functionalized polyacrylonitrile resin enabled separation and preconcentration of Hg(II) from multicomponent solutions containing Ni(II), Cu(II), Cd(II), Zn(II), and Pb(II) [12].…”

Application of mesoporous SBA-15 silica functionalized with 4-amino-2-mercaptopyrimidine for the adsorption of Cu(II), Zn(II), Cd(II), Ni(II) and Pb(II) from water

“…As can be seen, the adsorption of Zn(II), Cu(II) and Pb(II) presents distribution coefficients higher than 10 3 and, therefore, have potentiality to be preconcentrated in continuous flow experiments, as described in Ancântara' paper. 23 The characterization of the adsorptive properties of MS-AMP indicated that the material's adsorption capacities were found much lower than expected. Such argument is based on the low molar ratio between the coupled ligand content (0.842 mmol per gram of material) and the magnitude of the maximum adsorption capacities for the metal species.…”

Characterization of Corn (Zea mays) Leaf Powder and Its Adsorption Properties Regarding Cu(II) and Cd(II) from Aqueous Samples

“…In the last two decades, several methods, such as co-precipitation reactions (Soylak et al 2007;Bulut et al 2008), liquid-liquid extraction (Visser et al 2001;Morizono et al 2011), resin adsorption (Tanco et al 2002), and solid-phase extraction (Alcantara et al 2004;Madrakian et al 2008;Ferreira et al 2011;Filho et al 2013), have been successfully applied in the removal of metal species from aqueous samples. Among these methods, solid-phase extraction is still widely applied, possibly because of the development of new adsorbent materials and the possibility of anchoring different molecular ligands onto material surfaces (Alcantara et al 2004;Madrakian et al 2008;Mahmoud et al 2010;Ferreira et al 2011;Prado et al 2011;Filho et al 2013;Hajiaghababaei et al 2013;Jorgeto et al 2013).…”

“…Among these methods, solid-phase extraction is still widely applied, possibly because of the development of new adsorbent materials and the possibility of anchoring different molecular ligands onto material surfaces (Alcantara et al 2004;Madrakian et al 2008;Mahmoud et al 2010;Ferreira et al 2011;Prado et al 2011;Filho et al 2013;Hajiaghababaei et al 2013;Jorgeto et al 2013).…”

“…In general, the synthesis of new materials is the attempt to attach to a solid phase surface molecules containing Lewis base atoms, such as nitrogen, sulfur, oxygen (nonbonding electron carriers), and organic groups such as carboxylic groups, which may be involved in the coordination and ion exchange process, respectively (Alcantara et al 2004;Madrakian et al 2008;Filho et al 2013;Jorgeto et al 2013). Although it is possible to create a material with the desired characteristics, the steps involved in material surface modification may generate toxic residues due to the solvents used and may also have high costs Souza et al 2011;Filho et al 2013;Jorgetto et al 2013), making large-scale production for environmental purposes impossible.…”