Caio S.A. Felix’s research while affiliated with Federal University of Bahia and other places

This work reports carcinogenic and non-carcinogenic indices in inorganic assessing contamination in fish samples. In this context, fifty-one sardine samples were commercially acquired in seventeen neighborhoods and were toxicologically evaluated. These samples were washed, frozen, freeze-dried, and digested in a microwave oven. Six chemical elements were quantified using inductively coupled plasma optical emission spectrometry. The average levels on a wet basis expressed as μg g−1, ranged from 0.34 to 2.03 for total arsenic, 0.12 to 4.42 for copper, 0.04 to 0.26 for chromium, 4.61 to 99.39 for iron, 3.73 to 34.99 for zinc, and 0.01 to 4.07 for manganese. The estimated weekly intake, target hazard quotient, maximum safe consumption quantity, and carcinogenic risk indices were applied to the data found, denoting that arsenic levels can cause carcinogenic and non-carcinogenic adverse effects on the health of residents. However, these risks are minimized because the evaluation indices were calculated by total arsenic concentrations. In fish matrices, the arsenic is predominantly arsenobetaine, which has low toxicity. Samples from ten neighborhoods also showed copper concentrations that indicate the likelihood of carcinogenic risks. The chromium, iron, zinc, and manganese levels do not pose any health risks to consumers.

This work reports assessing risks to human health resulting from mercury levels in sardines (Sardinella brasiliensis), which have been highly consumed by the low-income population from Salvador, Brazil. Mercury was determined using the Direct Mercury Analysis (DMA) in fifty-one commercially acquired samples in seventeen neighborhoods. The mercury content on a wet basis ranged from 0.023 to 0.083 μg g− 1 for an average value of 0.039 μg g− 1. The estimated weekly intake (EWI), target hazard quotient (THQ), and maximum safe consuming quantity (MSCQ) were used in the toxicological assessment, and all these indices denoted that this food does not pose any risks to the human health of the population that consumes it. The development of this work was very significant because most sardines sold in Salvador originate from Todos os Santos Bay, which has a history of mercury contamination.

This work reports the quantification of total mercury in sediments collected in periods with and without rain from the Joanes River, Bahia, Brazil. Determinations were made using Direct Mercury Analysis (DMA), the accuracy of which was confirmed with two certified reference materials. The highest total mercury concentrations were found at the sampling point close to commercial areas and large residential condominiums. On the other hand, the lowest levels were found in the site close to a mangrove region. The geoaccumulation index was applied to the total mercury results, evidencing low contamination in the region studied. The contamination factor showed that of the seven stations investigated, four samples collected in the rainy season showed moderate contamination. The results of the ecological risk assessment were utterly consistent with the contamination factor data. This study showed that the smaller sediment particles concentrate more mercury, corroborating what has been predicted by the adsorption processes.

This work proposes the synthesis of a new polymer with imprinted ions (IIP) for the pre-concentration of uranium in natural waters using digital imaging as a detection technique. The polymer was synthesized using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) for complex formation, ethylene glycol dimethacrylate (EGDMA) as a crosslinking reagent, methacrylic acid (AMA) as functional monomer, and 2,2′-azobisisobutyronitrile as a radical initiator. The IIP was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy (FTIR). Uranium determination was performed using digital imaging (ID), and some experimental conditions (sample pH, eluent concentration, and sampling flow rate) were optimized using a two-level full factorial design and Doelhert response surface methodology. Thus, using the optimized conditions, the system allowed the determination of uranium with detection and quantification limits of 2.55 and 8.51 µg L−1, respectively, and a pre-concentration factor of 8.2. All parameters were determined using a 25 mL sample volume. The precision expressed as relative deviation (RSD%) was 3.5% for a solution with a concentration of 50 µg L−1. Given this, the proposed method was used for the determination of uranium in four samples of natural waters collected in the city of Caetité, Bahia, Brazil. The concentrations obtained ranged from 35 to 75.4 μg L−1. The accuracy was evaluated by the addition/recovery test, and the values found ranged between 91 and 109%.

This work reports the determination of mercury in fish samples purchased at a public market in Belem City, Brazil. The mercury quantification was performed using the DMA method, which allows limits of detection and quantification of 0.004 and 0.012 ng, respectively. Method accuracy was confirmed using a certified reference material of fish protein from (NRCC) National Research Council, Canada. The analyzed species were: Dourada (Brachyplatystoma rousseauxii), Filhote (Brachyplatystoma filamentosum), Pescada Branca (Cynoscion leiarchus), Piramutaba (Brachyplatystoma vaillanti). The mercury contents expressed as wet sample weight varied from 0.078 to 0.150 μg g-1. Afterward, the health risk assessment indices Estimated Weekly Intake (EWI), Target Hazard Quotient (THQ), and Maximum Safe Consuming Quantity (MSCQ) were applied to the analytical data, and the results obtained were exhaustively interpreted and discussed. All the indices demonstrated that the daily consumption of 25 g of these fishes does not pose a risk to the human health of the local population. However, these conclusions are preliminary and should not be used in public policy matters.

This study indicates the use of Phallusia nigra as a potential biomonitor of mercury contamination. In this way, Hg levels were measured in seawater and different parts of ascidians (tunic, hepatopancreas, and branchial basket) from eight different sites in the Todos os Santos Bay, Salvador-Bahia. The ascidians were lyophilized, weighed, and taken to the DMA-80 (direct mercury analyzer); the method accuracy was confirmed by analyzing the certified material DORM- 4 muscle tissue and MEES-3 marine sediment with a confidence level of 95%. The results were evaluated through the Tukey’s test and it was possible to observe a higher concentration of Hg (82.00-312.7 ng g-1) in the branchial basket, followed by the hepatopancreas (69.67‑130.7 ng g-1) and tunic (21.63-33.27 ng g-1). Thus, the branchial basket was the only tissue capable of identifying spatial differences in pollution between the points.

In the present work is described a new on-line solid-phase extraction system using a novel ion imprinted polymer as adsorbent for the preconcentration and determination of mercury(II) in natural water samples by Cold Vapor Atomic Fluorescence Spectrometry (CV AFS). The ion imprinted polymer was prepared by the improved bulk polymerization technique, occurring in only 3 h, based on mercury(II)-dithizone chelate, using methacrylic acid as monomer, ethylene glycol dimethacrylate as cross-linking reagent, 2,2′‑azobisisobutyronitrile as radical initiator, and dimethyl sulfoxide and acetonitrile as porogen solvents. The obtained polymer was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetry (TG), Derivative Thermogravimetry (DTG) and X-ray Diffraction (XRD). The on-line system was mounted by the easy coupling the mini-column packed with the Hg²⁺-IIP sorbent to the cold vapor system of the spectrometer. The optimum experimental conditions for the on-line preconcentration system were established employing multivariate methodology (two-level full factorial design and Doehlert matrix). Under the optimized conditions, limits of detection and quantification of 0.02 and 0.06 μg L⁻¹, and preconcentration factor of 29 were obtained for the determination of mercury using the developed on-line system, considering a sample volume of 50 mL. Precision expressed as a relative standard deviation (RSD%) was of 5.2% (n = 7) for a standard solution with mercury(II) concentration of 0.5 μg L⁻¹. Then, the on-line system was applied for the selective preconcentration and determination of mercury (II) in four natural water samples, and addition/recovery tests were performed to evaluate the accuracy of the method. All analyzed samples presented Hg²⁺ concentrations below the limit of quantification of the proposed method and the recovery values found were in range from 90 to 105%.

This work proposes an on-line digestion system employing 70% (w/w) hydrogen peroxide and UV radiation for producing hydroxyl radicals for the determination of chromium in beer samples by electrothermal atomization atomic absorption spectrometry (ETAAS). The digester system consists of a closed wooden box, which is painted black internally, containing a PTFE tube wrapped around a 15 W UV lamp. During the mineralization step, a peristaltic pump is employed to propel the sample solution over the UV lamp. The experimental factors UV irradiation time and hydrogen peroxide volume were optimized using a two-level full factorial design. Degradation curves at different pH conditions demonstrated that the digestion of beer is faster at alkaline pH. The results demonstrated that, in the presence of 70% H 2 O 2 and 15 W UV radiation, 75% of the chromophore species is degraded with an irradiation time of 25 min. The degradation kinetic curves of beer samples under different conditions were also evaluated. The apparent kinetic constant (kapp) found for the process assisted by 70% H 2 O 2 and 15 W UV light was 0.0668 min ⁻¹ (R ² = 0.9936). The on-line digestion procedure with a sample flow rate of 2 mL min ⁻¹ for 45 min allowed the determination of chromium in beer samples by ETAAS, utilizing the external calibration technique, with the analytical line 357.9 nm, in the presence of magnesium as chemical modifier with limits of detection and quantification of 0.86 and 2.90 μg L ⁻¹ , respectively. The method accuracy was confirmed by the analysis of the certified reference material of ERM-CA713 wastewater provided by the European Reference Materials. Six beer samples were digested and the chromium was determined. The contents found varied from 4.26 to 33.28 μg L ⁻¹ . Addition/recoveries tests were also performed to evaluate the accuracy method. The recoveries obtained varied from 93.2 to 96.4%.