Kristiany Moreira Diniz

Novel on-line sequential preconcentration system of Cr(III) and Cr(VI) hyphenated with flame atomic absorption spectrometry exploiting sorbents based on chemically modified silica.

In the present study, a flow injection system using dual mini-columns, SiO(2)/Al(2)O(3)/TiO(2) and silica gel functionalized with [3-(2-aminoethylamino)propyl] trimethoxysilane (SiO(2)/AAPTMS) for the sequential preconcentration of Cr(III) and Cr(VI), respectively, from water samples with FAAS detection was proposed. A two-level full factorial design (2(4)) and desirability function were employed for the optimization of variables related to the system performance. The detection limits of 0.66 and 0.27 μg L(-1) for Cr(III) and Cr(IV), respectively, were obtained under the optimized preconcentration conditions (flow rate of 7.0 mL min(-1)), pH 5.0, buffer concentration (acetate buffer) of 0.01 mol L(-1), and eluent (2.5 mol L(-1) HCl) flow rate of 5.0 mL min(-1). The other parameters including preconcentration factor (PF), consumptive index (CI), and concentration efficiency (CE) were found to be 17.62/32.98, 1.13/0.6 mL, and 6.2/11.54 min(-1) for Cr(III)/Cr(VI), respectively. The developed method was applied to the Cr(III) and Cr(VI) determination in water samples [tap, lake and mineral water, artificial saliva and parenteral solutions (physiological serum, water for injection, and glucose physiological solution)]. The method accuracy was checked by the analysis of standard reference materials (trace elements in water).

Preparation and evaluation of kinetics and thermodynamics studies of lead adsorption onto chemically modified banana peels

Abstract The use of alternative materials for environmental decontamination has been intensively studied. In this study, the capacity of banana peels treated with sodium hydroxide (NaOH), hydrochloric acid (HCl), and phosphoric acid (H3PO4) to adsorb Pb (II) was evaluated. The physical and chemical changes on the banana peels after chemical treatment were evaluated by infrared spectroscopy and scanning electron microscopy. Batch adsorption experiments were carried out as a function of pH, time, metal concentration, and temperature; desorption tests were also performed. Pb (II) concentrations were determined by flame atomic absorption spectrometry. An increase in the adsorption capacity of the modified and natural peels was observed in the pH range of 3–5, and pH 5 was adopted for further experiments. The adsorption system reached equilibrium in 300 min, and its kinetics followed the pseudo-second-order equation. From adsorption isotherms, it was observed considerable enhance on adsorption capacity of bana...

Synthesis, characterization and application of ion imprinted poly(vinylimidazole) for zinc ion extraction/preconcentration with faas determination

In this paper, we describe the synthesis of an ion imprinted polymer (IIP) by homogeneous polymerization and its use in solid-phase to extract and preconcentrate zinc ions. Under optimal conditions (pH 5.0, preconcentration flow rate of 12.0 mL min-1, and eluted with 1.0 mol L-1 HNO3) this procedure allows the determination of zinc with an enrichment factor of 10.2, and with limits of detection and quantification of 1.5 and 5.0 µg L-1, respectively. The accuracy of our results was confirmed by analysis of tap water and certified reference materials: NIST 1570a (Spinach leaves) and NIST 1515 (Apple leaves).

Preconcentration of Nickel(II) by a Mini-Flow System with a Novel Ternary Oxide Solid Phase and Flame Atomic Absorption Spectrometry

ABSTRACT A SiO2/Al2O3/Sb2O5 mixed oxide was synthesized via a sol-gel method and applied to the on-line preconcentration of Ni(II) with determination by flame atomic absorption spectrometry. The mixed oxide was characterized by infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray fluorescence, thermogravimetric analysis, and the specific surface area. Analysis was performed by percolating 20.0 mL of sample at pH 7.1 through 100 mg of SiO2/Al2O3/Sb2O5 packed into a mini-column at 9.5 mL min−1. Under the optimum conditions, a preconcentration factor of 77.5-fold, linear dynamic range from 5.0 to 270.0 µg L−1, and limits of detection and quantification of 0.48 and 1.61 µg L−1 were obtained. The effects of several concomitant ions were evaluated and no interferences were observed. The method was employed for the analysis of water with good recoveries (92.9–100.6%) and the accuracy was verified by using a marine sediment certified reference material (MESS-3).

Study on the performance of micro-flow injection preconcentration method on-line coupled to thermospray flame furnace AAS using MWCNTs wrapped with polyvinylpyridine nanocomposites as adsorbent

This work describes the synthesis and characterization of a new adsorbent nanocomposite based on multi-walled carbon nanotubes (MWCNTs) and polyvinylpyridine and its use in the development of a highly sensitive micro-flow injection preconcentration method coupled to TS-FF-AAS for the determination of very low levels of Cd. The characterization of the nanocomposite was performed by FT-IR, TGA, SEM, TEM and textural data measurements using the BET and BJH methods. The optimized conditions of the micro-flow injection preconcentration method involved a preconcentrated sample (8.8 mL) at pH 8.0 flowed through 50.0 mg of nanocomposite packed into a mini-column at a flow rate of 4.4 mL min−1. The on-line elution of Cd(II) ions towards the TS-FF-AAS detector was carried out in countercurrent at a flow rate of 0.6 mL min−1 using 1.0 mol L−1 HCl. The analytical curve ranged from 0.12 to 6.0 μg L−1 (r = 0.997), and an enhancement factor of 19.5, sample throughput of 15 h−1 and consumptive index of 0.45 mL were achieved. In terms of sensitivity, the uniquely high adsorption capacity of the nanocomposite was confirmed by the low limit of detection (36 ng L−1) achieved after implementing the preconcentration step in TS-FF-AAS. In terms of selectivity, the proposed method was shown to be tolerable to several foreign ions and applicable to different kinds of waters (tap, mineral, lake, and synthetic seawater), cigarettes, a food sample (powder chocolate), a medicinal herb (Ginkgo biloba) and a certified reference material (fish protein DORM-3).