Synthesis and Application of a New Polymer with Imprinted Ions for the Preconcentration of Uranium in Natural Water Samples and Determination by Digital Imaging.

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%.

Lab-in-Syringe, a Useful Technique for the Analysis and Detection of Pollutants of Emerging Concern in Environmental and Food Samples.

Lab-in-syringe is a new approach for the integration of various analytical extraction steps inside a syringe. Fully automated dispersive liquid-liquid microextraction is carried out in-syringe using a very simple instrumental setup. Dispersion is achieved by aspiration of the organic phase and then the watery phase into the syringe as rapidly as possible. After aggregation of the solvent droplets, the organic phase is pushed towards the detector allowing a highly sensitive spectrophotometric or fluorimetric detection. This technique is very useful not only for the preconcentration of analyte, but also for the elimination of their interferences. In this work, its application is described using solvents that are lighter and denser than water. The magnetically assisted variant and its coupling to different instruments has been also described with the aim of increasing the resolution of complex samples, especially useful for the determination of emerging contaminants.

Bioavailability assessment of toxic metals using the technique "acid-volatile sulfide (AVS)-simultaneously extracted metals (SEM)" in marine sediments collected in Todos os Santos Bay, Brazil.

This paper reports the bioavailability of the metals (cadmium, copper, zinc, lead, and nickel) in sediment samples collected in seven stations from the São Paulo Estuary, Todos os Santos Bay, Brazil. The bioavailability was determined by employing the technique "acid-volatile sulfide (AVS) and simultaneously extracted metal (SEM)". The elements cadmium, copper, lead, and zinc were determined using differential pulse anodic stripping voltammetry (DPASV), while nickel was quantified utilizing electrothermal atomic absorption spectrometry (ET AAS). The accuracy of these methods was confirmed using a certified reference material of estuarine sediment (NIST 1646). The sulfide was quantified using potentiometry with selective electrode and the organic matter determination employing an indirect volumetric method using potassium dichromate and iron(II) sulfate solutions. The bioavailability of the metals was estimated by relationship between the concentration of AVS and the sum of the concentrations of the simultaneously extracted metals (ΣSEM), considering a significant toxicity when (ΣSEM)/(AVS) is higher than 1. The bioavailability values in the seven stations studied varied from 0.93 to 1.31 (June, 2014) and from 0.34 to 0.58 (September, 2014). These results demonstrated a critical condition of toxicity (bioavailability >1) in six of the seven sediment samples collected during the rainy season (June, 2014). In the other period (September, 2014), the bioavailability was always lower than 1 for all sediment samples collected in the seven stations. The individual values of the concentrations of the five metals were compared with the parameters PEL (probable effects level) and TEL (threshold effects level), which are commonly employed for characterization of ecological risk in environmental systems. This comparison revealed that all metals have concentrations lower than the PEL and only zinc and lead in some stations have contents higher than the TEL. The bioavailability evaluation and the concentrations achieved for the five elements in the sediments samples analyzed demonstrated that the ecosystem studied does not present an environmental risk.

Human health risk assessment of mercury in highly consumed fish in Salvador, Brazil.

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.

Multi-commutated flow system for inorganic selenium speciation in infusion tea samples by chemical vapor generation atomic fluorescence spectrometry.

This work proposes an automated strategy for the inorganic selenium speciation in infusion tea samples, employing an MSFIA-CVG-AFS system and sodium tetrahydroborate for chemical vapor generation. The selenium total is determined after an online prereduction step of selenium (VI) to selenium (IV) in alkaline media, using a UV reactor with a 15 W Hg lamp. Selenium (IV) is quantified directly on the sample, and selenium (VI) is determined by the difference between the total selenium and selenium (IV) concentrations. The optimization of the chemical parameters: hydrochloric acid - hydrobromide acid solution concentration, potassium iodide concentration, sodium hydroxide concentration, and sodium tetrahydroborate concentration was performed using a (24-1) two-level fractional factorial design. The validation parameters were determined for total selenium and selenium (IV), and the results found were: limits of detection and quantification of 0.05 and 0.18 µg L-1, respectively; a linear range of 0.18-5.0 µg L-1, precision expressed as the relative standard deviation of 2.1% for a sample number of 10, for both analytes. The system allows the speciation analysis with an injection throughput of 15 injections per hour. This analytical method was applied for inorganic selenium speciation in nine infusions of tea samples purchased commercially in supermarkets in Palma de Mallorca City, Spain. The concentrations of selenium (IV) and total selenium varied from 0.2 to 0.6 µg L-1 and 0.4-2.0 µg L-1, respectively. The accuracy method was evaluated using spike tests, and the recoveries achieved varied from 91 to 111%.

Determination and evaluation of the ecological risk of mercury in different granulometric fractions of sediments from a public supply river in Brazil.

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.

The use of ANOVA-PCA and DD-SIMCA in the development of corn flour laboratory reference materials.

The development of a collaborative study as a requirement for the preparation of a laboratory reference material candidate is reported in this paper. The evaluation was performed by 13 laboratories invited to quantify the calcium, potassium, magnesium, phosphorus, copper, iron, manganese and zinc; 8 of them presented results for all the analytes under investigation. The data were statistically analyzed by applying the z-score robust technique as recommended by ISO Guide 35. For the potassium element, laboratories 4 and 13 presented questionable results. Laboratory 5 proved to be unsatisfactory for calcium and zinc. ANOVA-PCA and DD-SIMCA were also applied to evaluate stability and interlaboratory studies results, respectively. It has been demonstrated that multivariate data analysis can be successfully applied as an alternative method to the recommendations made by ISO 13528 and ISO Guide 35 with defined confidence intervals.

Fast automated method for the direct determination of total antimony in grape juice samples by hydride generation and atomic fluorescence spectrometric detection without external pretreatment.

Matrix complexity of fruit juices and their low antimony level requires sensitive, cost-effective instruments, time-consuming and error-prone sample pretreatment methods. Therefore, a flow-batch procedure (HG-FBA-AFS) was developed for the fast and sensitive determination of total inorganic Sb in grape juice samples by hydride generation atomic fluorescence spectrometry. The sample pretreatment, pre-reduction and stibine formation steps run through the mixing chamber. The HCl and NaBH4 concentrations, and carrier gas flowrate were optimized through a Box-Behnken design. The detection limit (LOD) was 20 ng L-1, intra and inter-day precision ranged in 3.0 - 3.5 %, and low errors within (- 2.4 to 6.6 %) for samples containing 1.23 - 4.58 µg L-1 total Sb. Both HG-FBA-AFS and reference method agreed at 95% confidence level. An 87 h-1 sample throughput, and a 1.15 mL total waste per determination attest that HG-FBA-AFS is a fast, and ecofriendly tool for determining Sb in grape juices.

Determination and human health risk assessment of mercury in fish samples.

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.

A risk assessment by metal contamination in a river used for public water supply.

Aquatic ecosystems provide habitats for many organisms. Historically, riverbanks have always been inhabited and exploited for subsistence and navigation. The present study evaluates the contamination and ecological risks caused by potentially toxic elements in surface sediments of the Paraguaçu River, Bahia, Brazil. Seven sediments samples were collected, and eight heavy metals were determined employing inductively coupled plasma spectrometry mass (ICP-MS). The concentrations range as (mg kg-1) found were 6.78-18.68 for lead, 14.21-42.16 for zinc, 27.61-48.63 for nickel, 2.03-6.50 for chromium, 6.06-12.90 for vanadium, 5.99-13.33 for cupper, 1.25-3.19 for cobalt, and 79.52-286.08 for manganese. Nickel showed significant enrichment (EF: 5.75; 7.62, and 14.11), followed by zinc, which showed moderate enrichment (EF: 2.16; 2.19, and 4.52). These enrichment levels are possible of anthropogenic origin. When the pollution index (PI) was evaluated, the elements V, Ni, Zn, Mn, Co, and Cu were strongly polluted (PI ≥3). In general, the pollution index (PI), geoaccumulation index (Igeo), enrichment factor (EF), and potential ecological risk indices (Er and PERI) show that contaminated sediments have adverse effects on aquatic environments, especially for o Mn, Ni, Pb, V, and Zn.

Homogeneity and stability studies during the preparation of a laboratory reference material of soy leaves for the determination of metals.

The homogeneity and stability of metals were tested in a candidate laboratory reference material of soy leaves. Inductively coupled plasma-optical emission spectrometry was used to quantify calcium, magnesium, manganese, iron, zinc, copper, and vanadium. A 6 kg amount of the material, which was dried, ground, and classified as mesh 60, was distributed among 100 bottles. The between-bottle homogeneity test was established by analyzing two subsamples from nine bottles. For the within-bottle test, five determinations of each element of a single bottle were performed. The stability test was performed at temperatures of -10, +27, and +40 degrees C, and after storage times of 4, 12, 24, and 52 weeks. The obtained results indicated that the material was homogeneous and stable under the conditions studied.

Validation of a digestion system using a digester block/cold finger system for the determination of lead in vegetable foods by electrothermal atomic absorption spectrometry.

This paper presents the validation of a system for sample digestion using a digester block/cold finger to determine the lead content in vegetables by electrothermal atomic absorption spectrometry (ETAAS). After mineralization, lead contents were determined by ETAAS using a calibration curve based on aqueous standards prepared in 2.60 M nitric acid solutions containing 5 microg ammonium phosphate as chemical modifier. A pyrolysis temperature of 900 degrees C and atomization temperature of 2000 degrees C were used. This method allowed the determination of lead with a characteristic mass of 35 pg; LOD and LOQ of 0.6 and 2 nglg, respectively, were found. The precision was investigated in terms of reproducibility and repeatability. Reproducibility was estimated by analysis of nine different portions of a certified reference material (CRM) of spinach leaves, and the repeatability was determined through the analysis of nine aliquots of the same solution. The reproducibility and repeatability were found to be 4.27 and 2.94% RSD, respectively. The accuracy was confirmed by analysis of whole meal flour, spinach leaves, and orchard leaves CRMs, all furnished by the National Institute of Standards and Technology. Lead contents were measured using the newly developed technique in 11 different potato samples. The lead contents ranged from 12.80 to 69.27 ng/g, with an average value of 28.59 ng/g. These values were in agreement with data reported in the literature.

Spatio-temporal assessment, sources and health risks of water pollutants at trace levels in public supply river using multivariate statistical techniques.

The Joanes River is located in the northeast of Brazil, crosses the Camaçari Petrochemical Complex, the largest integrated industrial complex in the Southern Hemisphere, which has over 90 companies in the chemical and petrochemical industry. The present study aims to evaluate spatial distribution, seasonal variation and identify possible sources of trace metal contamination in surface water samples of the Joanes River. Samples were collected in the dry (December 2018) and rainy (August 2019) seasons. Analysis of trace elements (As, Cd, Cr, Cu, Ni, Mn and Pb) were performed by ICP-MS. A total of 60 water samples were obtained. Samples were analyzed using exploratory techniques such as principal component analysis (PCA) and cluster analysis (CA). It was possible to characterize the samples according to the seasonal variation. The formation of two groups was observed. Among these, samples from the rainy season presented the higher levels of metals in relation to the samples of the dry season. Natural and anthropic sources of metal contamination were identified using CA. Similarity was shown in the relationship between the metals As-Pb and Ni-Cd-Cr-Cu in the dry season, and Cd-Ni and Pb-As-Cr-Cu in the rainy season. Dermal absorption (HQderm) and ingestion hazard quotients (HQing) routes exhibited values of less than one for all the elements analyzed for adults and children, in both rainy and dry seasons. This indicated that the pollutants analyzed posed little or no health risk over a lifetime of exposure. According to international guidelines (US EPA), the values of Cu, Pb and Cr were above the limit established.

Determination of Cu, Ni, Mn and Zn in diesel oil samples using energy dispersive X-ray fluorescence spectrometry after solid phase extraction using sisal fiber.

As a natural adsorbent, sisal (agave sisalana) fibers were used to extract Cu, Ni, Mn, and Zn from diesel oil samples for posterior determination (i.e., direct analytical measurements on the solid support) of the analytes by energy dispersive X-ray fluorescence spectrometry (EDXRF). In the proposed procedure, 0.2 g of sisal fiber was directly added to 5.0 mL of diesel oil contained in a glass tube. After 5 min of contact time, the mixture was filtered, and the collected fibers were oven-dried for 30 min at 70 °C. After drying, the analytes were quantified directly by EDXRF using the sisal fibers as a solid support. The calibration curves showed linear concentration ranges of 0.09-1.00, 0.12-1.00, 0.09-1.00, 0.06-1.0 µg g-1 for Cu, Ni, Mn, and Zn, respectively. The limits of detection (LOD) for Cu, Ni, Mn, and Zn were 0.03, 0.04, 0.03, and 0.02 µg g-1, respectively. The repeatability, evaluated by performing ten measurements at a concentration of 0.50 µg g-1 for each metal, with the results expressed in terms of the relative standard deviation (RSD), was 3.2, 6.5, 6.8, and 6.1% for Cu, Ni, Mn, and Zn, respectively. The results obtained by the proposed method were compared with the results obtained by a comparative method using inductively coupled plasma optical emission spectrometry, and both results showed good agreement. The proposed method was applied for Ni, Cu, Mn, and Zn determination in diesel oil samples collected from different gas stations.

A fast and sensitive flow-batch method with hydride generating and atomic fluorescence spectrometric detection for automated inorganic antimony speciation in waters.

In this paper, a flow-batch analysis (FBA) system, hydride generation (HG), and atomic fluorescence spectrometry (AFS) are coupled for the first time to develop a fast and sensitive FBA-HG-AFS method for automated inorganic antimony speciation in waters, whether from the sea, mineral water, tap water, or lakes. Unlike previous automated flow methods that use confluent fluids and complex devices, the main advantage of the proposed FBA-HG-AFS method is an innovative use of a simple laboratory made flow-batch chamber to simultaneously perform mixing, homogenization, reactions, antimony hydride formation, and gas-liquid separation. The FBA-HG-AFS method was optimized using two-level full factorial and Box-Behnken designs, and validated on the basis of real repeated measurements and analysis of variance, yielding a satisfactory working range (100-2000 ng L-1), precision (RSD = 4%), sensitivity, and limit of detection (6 ng L-1) for the water samples analyzed. Accuracy was evaluated by recovery tests and analysis of a standard reference material (SRM 1643e) of trace elements in water (NIST, USA), resulting in recovery rates of from 90 to 114%, and relative error = 0.7%. The high sampling throughput (54 speciations h-1), together with low waste generation, low costs, low reagent and sample consumption make this FBA-HG-AFS method an interesting proposal for fast large-scale analysis in routine laboratoy according to the principles of green analytical chemistry.

Multisyringe flow injection analysis (MSFIA) for the automatic determination of total iron in wines.

This work presents a multisyringe flow injection analysis (MSFIA) system for the automatic spectrophotometric determination of total iron in wine. The reaction is based on the complexation of Fe(II) with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP). Ascorbic acid was used as reducing reagent for Fe(III) to Fe(II) and, in this way, to determine the total iron content in wine. The absorbance of the Fe(II)-(Br-PADAP)2 complex was measured at 748 nm. The proposed method provided a working rage from 0.36 to 5 mg L-1 of Fe(II), with a detection limit of 0.11 mg L-1 of Fe(II), a relative standard deviation of 0.42% (3 mg L-1 of Fe(II), n = 10), and a 46 h-1 injection throughput. The system is very simple, rapid and selective, and has been successfully applied to determine total iron in red, rosé and white wine without any need for sample pre-treatment steps. The results agree well with ICP-AES, which used as a reference method.

A closed inline system for sample digestion using 70% hydrogen peroxide and UV radiation. Determination of lead in wine employing ETAAS.

This paper proposes a closed inline system for decomposition of wine, aiming at the determination of lead using electrothermal atomization atomic absorption spectrometry (ETAAS). The system is built using a 0.8 mm diameter PTFE tube, which is wrapped around an 8 W UV lamp. The sample in the presence of 70% hydrogen peroxide is circulated on an 8 W UV lamp at the flow rate of 1 mL min-1 for 45 min. Under these conditions, the carbon content varied from 10% to 2% for a red wine sample before and after digestion, respectively. The system has allowed the determination of lead in wine samples using the analytical line 283.306 nm in the presence of aluminum as the chemical modifier and pyrolysis and atomization temperatures of 800 and 1800 °C, respectively. Then, lead can be quantified employing the external calibration technique with limits of detection 0.27 and quantification 0.89 µg L-1, and characteristics mass of 18 pg. The precision expressed by relative standard deviation (RSD%) was 2.13%, calculated using six replicates of a digested solution of a wine sample with the lead content of 16.35 µg L-1. For evaluation of the accuracy method, two wine samples were analyzed simultaneously by the method proposed and also by inductively coupled plasma mass spectrometry (ICP-MS). A statistical test demonstrated no significant difference between the means obtained by these two techniques. Also, experiments involving addition/recovery tests confirmed the method's accuracy. The system was employed for digestion and determination of lead in four Brazilian wine samples. The lead content varied from 2.19 to 43.48 µg L-1.

Speciation analysis based on digital image colorimetry: Iron (II/III) in white wine.

This work proposes an analytical strategy utilizing digital images (DI) for the iron inorganic speciation in white wine. The method was established by the reaction of iron(II) ions with 1,2 ortho-phenanthroline as a chromogenic reagent. Total iron was determined using the same reagent after the addition of hydroxyl ammonium chloride as a reducing agent. In both cases, digital images of the standards/chromogenic reagent and samples were acquired and stored in JPEG format. The region of interest (ROI) was determined with a constant square shape for all images. The ROI was submitted to decomposition in color values according to the RGB additive color model. However, the data obtained by the blue channel was the one used in the construction of the analytical curves because it presented the highest sensitivity. The optimization of the experimental conditions of the procedure was performed by employing multivariate techniques. The precision was evaluated using a wine sample with iron (II) and total iron contents of 0.41 and 0.69 mg L-1, respectively. The results expressed as relative standard deviations were 3.57% for iron (II) and 4.76% for total iron contents. A comparison between the results obtained for total iron by the DI method with the results found using flame atomic absorption spectrometry confirmed the method accuracy. The DI procedure was applied for speciation analysis in six white wine samples and the contents found varied from 0.41 to 1.67 mg L-1 for iron (II) and from 0.69 to 1.71 mg L-1 for total iron. These results are in agreement with those found for speciation analysis of iron in wine samples. Iron (III) contents can be found by the difference between the total iron and iron (II) contents.

Multivariate optimization techniques in food analysis - A review.

This work presents a critical review of multivariate techniques employed for optimization of methods developed in food analysis. A comparison between the response surface methodologies has been performed, it evidencing advantages and drawbacks of these. Applications of the main chemometric tools (central composite and Box Behnken designs and Doehlert matrix) often utilized for optimization of sample preparation procedures and also instrumental conditions of analytical techniques for determination of organic and inorganic species in food samples are shown. Also, a brief discussion on the use of multiple responses and robustness test in food analysis has been presented.

Determination of free and total sulfur(IV) compounds in coconut water using high-resolution continuum source molecular absorption spectrometry in gas phase.

This work proposes a method for the determination of free and total sulfur(IV) compounds in coconut water samples, using the high-resolution continuum source molecular absorption spectrometry. It is based on the measurement of the absorbance signal of the SO2 gas generate, which is resultant of the addition of hydrochloric acid solution on the sample containing the sulfating agent. The sulfite bound to the organic compounds is released by the addition of sodium hydroxide solution, before the generation of the SO2 gas. The optimization step was performed using multivariate methodology involving volume, concentration and flow rate of hydrochloric acid. This method was established by the sum of the absorbances obtained in the three lines of molecular absorption of the SO2 gas. This strategy allowed a procedure for the determination of sulfite with limits of detection and quantification of 0.36 and 1.21mgL-1 (for a sample volume of 10mL) and precision expressed as relative standard deviation of 5.4% and 6.4% for a coconut water sample containing 38.13 and 54.58mgL-1 of free and total sulfite, respectively. The method was applied for analyzing five coconut water samples from Salvador city, Brazil. The average contents varied from 13.0 to 55.4mgL-1 for free sulfite and from 24.7 to 66.9mgL-1 for total sulfur(IV) compounds. The samples were also analyzed employing the Ripper´s procedure, which is a reference method for the quantification of this additive. A statistical test at 95% confidence level demonstrated that there is no significant difference between the results obtained by the two methods.