A procedure using disposable pipette tips adapted for solid-phase extraction, known as DPX SPE, was used as an alternative way for the chromium determination in wastewater samples. DPX-SPE consists of a device which allows a dynamic contact between the sample and the solid-phase. A residue obtained from the processing of coffee beans, denominate coffee silverskin, was used as a new adsorbent. Characterization techniques revealed properties of lignocellulosic materials with potential application for chromium adsorption. The parameters including adsorbent mass (25.00 mg), elution solvent (0.1 mol L-1 HCl, 200 μL) and pH (2.0) were optimized. Thus, 1.00 mL of deionized water for conditioning, 4.00 mL of sample, 2 extraction cycles and 1 elution cycle were the employed conditions. Enrichment factor of 12, limit of detection of 6.00 µg L-1 and relative standard deviation (RSD) 1.3% (n = 3) were obtained. The method proved to be fast, cheap, environmentally friendly, and simple, providing good recoveries (104-113%), and it was satisfactorily applied in real samples.

A magnetic solid-phase microextraction procedure was developed to detect lead in aqueous samples by flame atomic absorption spectrometry (FAAS). Fe3O4 nanoparticles were synthesized by coprecipitation and the crystalline phase was confirmed by X-ray diffraction. The point of zero charge (PZC) indicated that the oxide surface was negatively charged at pH levels above 9.4. pH 9.0 is the best for adsorption and the influence of stirring time and adsorbent mass were analyzed and set at 4 min and 3.0 mg, respectively. The best desorption conditions were obtained for 500 µL of 0.5 mol L-1 HNO3 as eluant. The limit of quantification (LOQ) and relative standard deviation (RSD) were 16.48 µg L-1 and 0.25%, respectively. The linear range was found to be 16.48‑500 µg L-1. The accuracy was evaluated by recovery tests in mineral water, micellar water and aqueous makeup remover samples, showing values in the range of 95.94 to 118%.

A procedure was developed for the direct determination of SbIII and total inorganic Sb in water samples by hydride generation atomic absorption spectrometry (HG AAS), without pre-reduction of SbV. The NaBH4 concentration was maintained at 0.4% (m/v) to perform the selective generation of stibine from SbIII and online stibine generation was carried out with 5.0% (m/v) NaBH4 to obtain the total antimony concentration. SbV was calculated as the difference between the values obtained for total Sb and SbIII. In both cases, the procedure did not appear to be adversely affected by potential interferents such as SbV, AsIII, AsV, CaII, NaI, chloride and phosphate at a concentration of 0.5 mg L-1. For the proposed procedure, the detection limits were 0.2 µg L-1 for SbIII and 0.3 µg L-1 for total Sb, while the relative standard deviations were 0.1% for 10.0 µg L-1 SbIII and 0.4% for 10.0 µg L-1 total Sb. A sampling rate of approximately 30 determinations perhour was achieved, requiring 300 mL of NaBH4, and the amount of waste generated was in order of 960 mL, indicating that this analytical procedure can be considered as green. The method was shown to be satisfactory for the determination of trace levels of antimony in water samples. The result obtained for the assaying of certified drinking water samples was 9.7 ± 0.1 µg L-1 (certified value 10.0 ± 0.5 µg L-1).

Este trabalho descreve o potencial de sorção das sementes de Moringa oleifera para descontaminação de AgI em soluções aquosas. Espectroscopia de infravermelho foi usada para elucidação de possíveis grupos funcionais responsáveis pela adsorção de AgI. Estudos de adsorção foram feitos em batelada usando soluções padrão de AgI como função da massa do adsorvente, tempo de extração, tamanho da partícula e pH. A AgI foi quantificada antes e após os experimentos de remoção usando espectrometria de absorção atômica por chama. Adicionalmente, considerando-se os estudos de adsorção e isotermas de adsorção aplicadas ao modelo de Langmuir foi possível verificar que as sementes de M. oleifera apresentam alta capacidade de adsorção. As condições ótimas foram: 2,0g de adsorvente com tamanhos de partícula de 75-500 µm, 100 mL de solução 25,0 mg L-1 AgI, tempo de extração de 20 min e pH 6,5. Os resultados mostram que as sementes de Moringa oleifera podem ser usadas para remoção de AgI em soluções aquosas.

This work describes the sorption potential of Moringa oleifera seeds for the decontamination of AgI in aqueous solutions. Infrared spectroscopy was used for elucidating possible functional groups responsible for uptaking AgI. Sorption studies using AgI standard solutions were carried out in batch experiments as functions of adsorbent mass, extraction time, particle size and pH. The AgI was quantified before and after the removal experiments using flame atomic absorption spectrometry. Furthermore, based on adsorption studies and adsorption isotherms applied to the Langmuir model, it was possible to verify that M. oleifera seeds present a high adsorption capacity. The optimum conditions were: 2.0 g of adsorbent with particle size of 75-500 µm, 100 mL of 25.0 mg L-1 AgI, extraction time of 20 min and pH at 6.5. The results show that Moringa oleifera seeds can be used for removing AgI in aqueous solutions.