Synthesis of Chelating Agent Free-Solid Phase Extractor (CAF-SPE) Based on New SiO2/Al2O3/SnO2 Ternary Oxide and Application for Online Preconcentration of Pb2+ Coupled with FAAS

Abstract

A new online solid phase preconcentration method using the new SiO 2 /Al 2 O 3 /SnO 2 ternary oxide (designated as SiAlSn) as chelating agent free-solid phase extractor (CAF-SPE) coupled to flame atomic absorption spectrometry (FAAS) for Pb 2+ determination at trace levels in different kind of samples is proposed. The solid adsorbent has been characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron miscroscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray fluorescence spectroscopy (XRF) and textural data. The method involves the preconcentration using time-based sampling of Pb 2+ solution at pH 4.3 through 100.0 mg of packed adsorbed into a mini-column under flow rate of 4.0 mL min -1 during 5 min. The elution step was accomplished by using 1.0 mol L -1 HCl. A wide range of analytical curve (5.0-400.0 µg L -1 ), high enrichment factor (40.5), low consumption index (0.5 mL) and low limits of quantification and detection, 5.0 and 1.5 µg L -1 , respectively, were obtained with the developed method. Practical application of method was tested on water samples, chocolate powder, Ginkgo biloba and sediment (certified reference material). On the basis of the results, the SiAlSn can be considered an effective adsorbent belonging to the class of CAF-SPE for Pb 2+ determination from different matrices.Keywords: lead, online solid phase extraction, SiO 2 /Al 2 O 3 /SnO 2 , flame atomic absorption spectrometry, food and water samples IntroductionLead contamination has been considered one of the most environmental concern worldwide due to numerous acute and chronic adverse effects caused by the element. 1,2 To the population in general, which is not occupationally exposed, water and food are significant sources of exposure to lead. 2 The most common lead contamination pathways to water are the household plumbing corrosion and anthropic pollution, while to food are the development of plants grown in soil containing high amount of lead and the accidental additive picked up during food processing. [3][4][5][6] Due to its high degree of toxicity and the effects caused to the ecosystem, a rigid monitoring of the activities involving this metal is required.According to World Health Organization (WHO), 6-8 the health-based guideline established value for lead in drinking water is 10.0 µg L -1 , while for food, the seventy-third report of the Joint Food Agriculture Organization/WHO Expert Committee on Food Additives estimated the mean dietary Synthesis of Chelating Agent Free-Solid Phase Extractor (CAF-SPE) Based on New SiO 2 /Al 2 O 3 /SnO 2 Ternary Oxide J. Braz. Chem. Soc. 1226 exposure per day and body weight for children (aged about 1-4 years) and to adults being in the range 0.03-9.00 and 0.02-3.00 µg kg -1 , respectively. The Brazilian Ministry of Health 9 and CONAMA resolution No. 357 (Brazil National Environment Council) 10 established the maximum allowable lead content in freshwater as 30.0 µg L -1 , while for drinking water this index reduces to 10.0 µg L -1 and effluents release...

Development of an electrochemical sensor based on ternary oxide SiO2/Al2O3/SnO2 modified with carbon black for direct determination of clothianidin in environmental and food samples

“…The high performance of the GCE/CB/SiAlSn sensor is explained using the electrochemical conductivity of the carbon black (a low-cost and abundant material) which is maximized with the association of the ternary oxide formed by a silica matrix homogeneously supporting two oxides of amphoteric nature, due to the synthesis process based on the sol–gel method. 46 This is probably due to the interactions between the CB and the SiAlSn-A material by intermolecular forces of the van der Waals type and/or hydrogen bonding, since the SiAlSn-A material presents hydroxyl groups (OH) on its surface, which can interact with a range of oxygen functionalities (phenolic, carboxylic, quinonic or lactonic) present on the CB surface. 51 These characteristics directly influenced the electroreduction and electrocatalysis response of the CLD pesticide on the surface of the proposed sensor.…”

“…1a, it was identied that the surface morphology of SiAlSn was at or rough with nonspherical particles smaller than 50 mm, very common for mixed oxides obtained by the sol-gel process. 46 In Fig. 1b, the incorporation of particles of the ternary oxide with carbon black is noticed demonstrating the possibility of an increase in the roughness of the bare GCE surface when modied and, consequently, an improvement in the electroactive surface area.…”

“…The mixed oxide material used in this study was synthesized by the sol–gel process with variation only in the proportion of reactants. 46 Thus, initially, in a 500 mL reactor, approximately 115.0 mL of tetraethylorthosilicate (TEOS, 98%), 115.0 mL of ethanol PA and 15.0 mL of a 3.0 mol L −1 HNO 3 solution were added to promote the pre-hydrolysis of TEOS. The resulting solution was stirred for 3 h at a temperature of 700 °C.…”