NIST 1566b Research Articles

Separation of nickel and cadmium from aqueous solutions by flow injection preconcentration onto cadion functionalized polyurethane foam

A simultaneous spectrophotometric method was developed for the rapid determination of the binary elements nickel and cadmium. Two polyurethane foam sorbents, cadion functionalized foam and untreated foam, were separately packed in two minicolumns and used for on-line preconcentration/separation. The two elements were separated/preconcentrated on the cadion- foam minicolumn, and then they were eluted by hydrochloric acid and mixed with a thiocyante stream before entering the untreated foam minicolumn. Nickel passed out to react with 4-(2-pyridylazo)-resorcinol reagent and measured spectrophotometrically at 498 nm. The adsorbed cadmium-thiocyanate on the untreated foam was further eluted by sodium hydroxide and identically detected. At a preconcentration time of 60 sec (100 µg L−1), the detection limit was 4.6 and 3.3 µg L−1 and the quantification limit was 15.3 and 11.0 µg L−1 for cadmium and nickel, respectively. The preconcentration factor was 5.0 and 11.0, respectively, and sampling frequency was 12 and 20 h−1. The accuracy was assessed using the BCR397R human hair and NIST 1577b bovine liver certified reference materials with a recovery of 92.0–94.2% (Relative standard deviation = 5.3–8.2%). The analysis of human urine and tap water samples demonstrated the applicability of the method and showed a relative recovery of 89.6 to106% (Relative standard deviation ≤ 9.4%).

Artificial neural network employment for element determination in Mugil cephalus by ICP OES in Pontal Bay, Brazil.

Fish are important sources of protein, making them very significant in the human diet. Although the consumption of this food is beneficial for health, it is essential that the product does not contain inorganic components above the limits recommended by the current legislation. Therefore, a method for determination of elements in fish (Mugil cephalus) samples was optimized. A simplex centroid mixture design with restriction was applied for optimization of the acid digestion of samples in an open system under reflux in order to evaluate the best ratio between the reagents HNO3, H2O2 and H2O. The results indicated that more intense analyte signals were obtained when a mixture containing 3.6 mL of HNO3 (65% v/v), 0.4 mL of H2O2 (30% v/v) and 6.0 mL of H2O was used. The accuracy of the method was assessed with a CRM of oyster tissue (NIST 1566b). The method presented relative standard deviations (RSDs) of 3.54%; 3.82%; 4.81% and 3.50% for Zn, Fe, Cu and S, respectively. The detection limits were 0.002 mg kg-1 for Cu and Zn and 0.02 mg kg-1 for Fe and S. The proposed method was applied for the determination of Zn, Fe, Cu and S in fish samples. A Kohonen Self-Organizing Map (KSOM) with K-means implementation was applied to better delimit the boundary between groups and the spatial and temporal influence on how concentrations of the chemical elements were perceived. To verify the separation, the Davies-Bouldin and Silhouette indices were used, obtaining 0.5374 and 0.8541, respectively, indicating satisfactory separation.

Determination of essential and potentially toxic elements and their estimation of bioaccessibility in honeys

In this work, the evaluation of the mineral profile and estimation of the bioaccessibility of essential and potentially toxic elements in honey samples was proposed. The experimental design and multivariate data analysis were applied as tool chemometrics. The acidic honey decomposition procedure using a cold finger digester block was proposed for analysis by inductively coupled plasma optical emission spectrometry (ICP OES). The analytical method presented good precision (<10%). The accuracy was confirmed through the analysis of a certified reference material (CRM) of tomato leaves (AGRO C1003a) and oyster tissue (NIST 1566b). The concentration ranges (in mg kg−1) of the analytes quantified in honey samples were As (<LoQ, 3.25), B (<LoQ, 6.72), Ba (<LoQ, 0.25), Ca (28.4–216), Cd (<LoQ, 0.29), Cu (<LoQ, 0.29), Fe (<LoQ, 47.0), K (27.2–1210), Mg (2.82–96.0), Mn (0.17–4.62), Na (16.4–260), P (<LoQ, 128), Se (<LoQ, 0.45), Sr (<LoQ, 1.08), and Zn (<LoQ, 2.94). Higher concentrations of Cu and Zn were observed in dark and amber honeys. From the multivariate analysis of the data, it was verified that the samples of urban predominance presented higher mineral content than the samples of honey of predominance rural. The bioaccessibility estimation was performed using the in vitro extraction method using the simple bioaccessibility extraction test (SBET). The bands of the bioaccessible contents (in %) for the analytes were Ca (<LoQ, 21.4), Fe (<LoQ, 21.8), K (9.4–20.0), Mg (15.0–25.0), and Na (<LoQ, 20.2). These results provide relevant information about the mineral composition of honey based on the visual coloration, geographical origin and bioaccessible content of the analytes in the gastric phase, contributing to the control of honey quality.

Optimization of magnetic solid phase microextraction with CoFe2O4 nanoparticles unmodified for preconcentration of cadmium in environmental samples by flame atomic absorption spectrometry

A method of preconcentration based in the magnetic solid phase microextraction with CoFe2O4 nanoparticles for the determination of cadmium in oyster and water samples using flame atomic absorption spectrometry (FAAS). Magnetic nanomaterials ones have aroused a greater interest in the area of analytical chemistry because of the high area of material and separation facility of the adsorbent. The statistical significance variables, extraction time, nanoparticles mass, pH, eluent concentration and desorption time were evaluated using a fractional factorial design of two levels (25–1). Afterward, a design Doehlert was used to optimize the pre-concentration process. The best experimental conditions were: nanoparticles mass (25 mg), pH (10.0) and eluent concentration of 1.20 mol L−1. The method allowed the determination of cadmium with a LOD of 0.24 μg L−1 and LOQ of 0.80 μg L−1. The precision expressed as relative standard deviation (RSD) of 3.33% for cadmium concentration with 20 μg L−1, the accuracy of the method was confirmed by the analysis of materials certified reference NIST 1566b Oyster tissue, pre-concentration factor 31. The method was applied to the analysis of the oyster and water samples has determined the concentration of cadmium from 4.6 to 7.8 mg kg−1 for oyster and 2.75 to 4.8 μg L−1 for water.

Hybridized robust chemometrics approach for direct rapid determination of trace biometals in tissue utilizing energy dispersive X-ray fluorescence and scattering (EDXRFS) spectrometry

Direct rapid energy dispersive X-ray fluorescence and scattering (EDXRFS) analysis of trace biometals in soft body tissues is important because it has an immense potential for biomedical applications. Unfortunately this is challenging because soft body tissues are characterized by dark matrix problems, weak analyte fluorescence, scattering, poor signal-to-noise ratio (SNR) of the analyte and spectral overlaps due to the properties of the detector and detection process. We report on hybridized utility of robust chemometrics approach for spectral preprocessing towards improving the quality of spectra towards quantitative analysis of trace biometals in soft body tissue. The study was based on (5–20 µm thick) paraffin wax model ‘standards’ spiked with biometals Fe, Cu, Mn, Zn, Co, Na and Mg. Wavelet transform (WT) and principal component analysis (PCA) were used conjointly for de-noising and mathematical enhancement of resolution. There was improved SNR of spectra by a factor of 3 compared to use of WT alone. The preprocessed spectra were used as input to artificial neural network (ANN) and partial least squares (PLS) models for developing multivariate calibration strategies for quantitative analysis. Both models predicted the concentrations of the biometals better than when raw spectra were utilized (R2 ~ 0.892–0.954 before, and ~ 0.990–0.998 after preprocessing for ANNs; and R2 ~ 0.876–0.931 before, and ~ 0.977–0.992 after preprocessing for PLS). There was also improvement in prediction of Na and Mg in model tissue when both fluorescence and scatter were utilized conjointly (EDXRFS) i.e. R2 = 0.970 for fluorescence alone and R2 = 0.998 for both fluorescence and scatter for Na; and R2 = 0.934 for fluorescence alone and R2 = 0.993 for both fluorescence and scatter for Mg for ANN model. The accuracy of the calibration model was tested using Oyster tissue (NIST 1566b). The results of all analyzed elements were in agreement with certified values to ≤ 6%. This shows proof-of-concept for use of hybridized robust chemometrics approaches for direct rapid determination of trace biometals in soft tissue utilizing EDXRFS spectrometry; an approach that has potential for biomedical applications of EDXRF.

Analysis of children modelling clay (toy) using inductively coupled plasma-based methods

This work proposes the application of a Doehlert design to optimize dilute HNO3 and H2O2 concentrations employed for the digestion of samples of modelling clay for children (used as toy). Inductively coupled plasma-based (ICP) methods were employed to determine 22 inorganic constituents (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Sb, Se, Sr, V and Zn) in children's modelling clay samples. The limits of quantification (LoQ) obtained were between 0.003 mg kg-1 (Cd, Co and Sb) and 0.54 g kg-1(Ca) employing ICP-based methods. The accuracy and precision of the methods were evaluated by analysing the certified reference materials (CRMs) oyster tissue (NIST 1566b), rice flour (NIST 1568b), peach leaves (NIST 1547) and tomato leaves (NIST 1573a), along with addition and recovery tests. The children's modelling clay samples presented concentrations of As, Ba, Cd, Cr, Pb, Sb and Se in agreement with the maximum values established by National Institute of Metrology, Quality and Technology (Instituto Nacional de Metrologia, Qualidade e Tecnologia - INMETRO). However, for other elements it were obtained concentrations within the following ranges: Al (0.83 ± 0.12–2.91 ± 0.04 g kg−1), Ca (16.09 ± 0.20–24.56 ± 1.00 g kg−1), Cu (< 0.30–30.01 ± 2.11 mg kg−1), Fe (< 5.3 - 13.21 ± 3.94 mg kg−1), K (1.31 ± 0.33–33.47 ± 0.75 g kg−1), Mg (0.90 ± 0.04–1.36 ± 0.05 g kg−1), Mn (3.32 ± 0.10–121.05 ± 1.88 mg kg−1), Na (12.07 ± 0.88–36.77 ± 0.50 g kg−1), Sr (4.23 ± 0.47–22.43 ± 6.95 mg kg−1), P (1.00 ± 0.13–57.43 ± 0.88 g kg−1), V (0.25 ± 0.07–1.15 ± 0.19 mg kg−1), S (3.57 ± 0.77–48.49 ± 1.02 g kg−1), Zn (< 4.4–11.82 ± 0.49 mg kg−1), Co (0.020 ± 0.002–0.060 ± 0.020 mg kg−1) and Ni (< 0.03–1.33 ± 0.46 mg kg−1). These elements have no minimum and maximum limits established by legislation for children's modelling clay so, a comparison was not possible. The ICP-based methods presented an efficient routine application in the analysis of modelling clay.

Multivariate data analysis of trace elements in bivalve molluscs: Characterization and food safety evaluation

Four species of bivalve molluscs (Anomalocardia brasiliana, Iphigenia brasiliana, Lucina pectinata and Trachycardium muricatum) were collected in the Todos os Santos Bay (TSB), Bahia, Brazil, in order to evaluate As, Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb, Se, V and Zn levels and, consequently, the risk of bivalve mollusc consumption in humans. The samples were analyzed by inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry (ICP-MS) after closed-vessel microwave digestion. The accuracy was confirmed using the certified reference materials of oyster tissue (NIST 1566b) and mussel tissue (NIST 2977), and the results were statistically equivalent to the certified values. Application of principal component analysis (PCA) and hierarchical cluster analysis (HCA) showed a tendency to form two groups between samples of Lucina pectinata and Trachycardium muricatum. All species showed As and Cr concentrations higher than the maximum tolerable limit specified in Brazilian legislation.

Optimization of sample preparation procedures for evaluation of the mineral composition of fish feeds using ICP-based methods

This work describes the application of an experimental design in optimizing the decomposition and spectrometer operational conditions for analysis of fish feeds. The content of 22 elements (six macroelements, four microelements and eleven trace elements) in feeds for fishes (ornamental and for human consumption) was determined by inductively coupled plasma (ICP)-based methods. Limits of quantification were obtained and the values ranged between 0.02 mg kg−1 (Cd) and 76 mg kg−1 (Al). Evaluation of the methods was achieved through analysis of standard reference material, Oyster Tissue (NIST 1566b) and Tea (NCS DC 73351). Element concentrations in feed samples for ornamental fish ranged from <0.02 mg kg−1 (Cd) to 2.79% (P) and for fish breeding for human consumption from <0.02 mg kg−1 (Cd) to 2.00% (Ca). The concentrations of the elements obtained in the analyzed fish feeds were within the limits established by Brazilian and American legislation for regulated elements.

Application of Factorial Design and Desirability Function to Develop a Single Analytical Procedure for the Determination of Metals in Different Tissues of Blue Crab (Callinectes danae)

In this scientific work, it was developed a single analytical procedure for the sample preparation of different tissues of blue crabs using microwave-assisted digestion for the determination of Cu, Mn, Fe and Zn by fast sequential flame atomic absorption spectrometry (FS FAAS). The limits of quatification were 10.5, 1.6, 8.9 and 19.3 µg g-1 for Cu, Mn, Fe and Zn, respectively. The precision was estimated in terms of repeatability using the relative standard deviation (RSD, n = 7) 3.4% for Cu; 4.8% (Mn); 4.7% (Fe) and 4.7% (Zn) and accuracy of the procedure was confirmed by analysis of certified reference material (CRM) of oyster tissue (NIST 1566B) with concentration values of 71.3 for Cu, 18.3 for Mn, 202.5 for Fe and 1415 µg g-1 for Zn. The procedure has been applied for the determination of Cu, Mn, Fe and Zn in several blue crab samples from Cachoeira River estuary, Ilheus, Bahia, Brazil.

Determination of Co and Cr in wet animal feeds using direct solid sample analysis by HR-CS GF AAS

The present study proposes the determination of Cr and Co in wet animal feeds for employing direct solid sample analysis (SS) and high resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). For determination of Cr and Co, the analytical lines 357.8687nm and 240.7254nm were used, respectively. The pyrolysis temperatures were 1500 and 1400°C and atomization temperatures were 2500 and 2400°C for Cr and Co, respectively. The limits of quantification (LoQ) obtained for Cr was 0.03μgg−1 and 0.17μgg−1 for Co. The characteristic masses (m0) also obtained were 2.2pg for Cr and 2.9pg for Co. The accuracy of the proposed methods was performed by analysis of standard reference materials (SRM) of tomato leaves (NIST 1573), bovine muscle powder (NIST 8414) and apple leaves (NIST 1515) for Cr and bovine liver (NIST 1577b) for Co. The trueness obtained were between 102±9 and 116±7% for Cr and 94±8% for Co for analyzed of the SRM. Precision, expressed as relative standard deviation (RSD), was better than 8.7% for Cr and 8.3% for Co (n=5). Thirteen wet animal feed samples for dogs and cats were analyzed. The concentrations values found for Cr in the samples ranged from 0.17±0.01 to 0.59±0.06μgg−1 with an average of 0.36±0.13μgg−1 (n=13). On the other hand, the obtained concentrations for Co ranged between <0.18 and 12.57±1.11μgg−1, with an average of 5.92±3.19μg. The optimized analytical methods were simple, fast, efficient, precise and accurate for determination of Cr and Co in wet animal feeds for cats and dogs by HR-CS SS-GF AAS. Additional advantage of the method was no dissolution of the samples, no use of harmful reagents and consequently no generation of residues, besides the use of an effective analytical technique that allows optimization of fast and reliable screening procedures.

Screening of Passiflora L. mineral content using principal component analysis and Kohonen self-organizing maps

A method using digestion with diluted nitric acid and inductively coupled plasma optical emission spectrometry was applied to determine metal ions in the peel, pulp, and seed of Passiflora edulis f. flavicarpa and Passiflora cincinnata cultivated in the Bahia state, Brazil. Plasma parameters (radio frequency power and argon flow rates) were optimized. The quantification limits (µg g−1) were: Ca (43.0); Co (1.3); Cu (10.0); Fe (10.0); K (20.0); Mg (26.6); Mn (0.33); Na (56.6) and Zn (10.0). The accuracy of the method was evaluated by the analysis of certified reference materials (NIST 1567a Wheat Flour and NIST 1577b Bovine Liver). Recovery studies were carried out and values found were between 89 and 120%. PCA and Kohonen self-organizing maps showed the formation of groups, corresponding to the fruit parts. Thus, passion fruit has great importance and biological potential, due to its high content of K and low Na.

Estimation of the Expanded Uncertainty of an Analytical Method to Quantify Aluminum in Tissue of Sprague Dawley Rats by FAAS and ETAAS

The soluble forms of aluminum are now considered toxic or potentially toxic and they have been associated or related with neurological alterations, liver, bone, hematological disorders and breast cancer. To estimate the expanded uncertainty of a previously validated analytical method to quantify aluminum in tissues of Sprague Dawley rats through flame atomic absorption spectroscopy (FAAS) and electrothermal (ETAAS). The sources of uncertainty through an Ishikawa diagram have been established and the relative and combined standard uncertainty of the concentration of aluminum was determined from the curves of calibration, volumetric material and the dilution factor, repeatability, the purity of a standard aluminium and the concentration of aluminium in two certified reference materials (SRM-S-B and NIST 1566b). The estimates of each source of uncertainty were determined following the Eurachem/Citac Guide. It was possible to estimate the expanded uncertainty (U) with a factor k = 2, and the results were of 3.709 mgL−1 and 3.717 µgL−1 of aluminium in tissues of Sprague Dawley rats with FAAS and ETAAS, respectively. There are few works in which the expanded uncertainty of an analytical method has been found to determine aluminum in tissue, however the results are acceptable and comparable against the results obtained with other methods that estimate the uncertainty of other metals and different matrix or tissue.

Evaluation of Distribution and Bioaccumulation of Arsenic by ICP-MS in Tilapia (Oreochromis niloticus) Cultivated in Different Environments

The concentration of arsenic in tissues of tilapia was evaluated and an estimation of the risks associated with the consumption of this fish was done, taking into account the guidelines established by FAO/WHO. The inductively coupled plasma mass spectrometry (ICP-MS) technique in kinetic energy discrimination (KED) mode was employed and certified reference materials were analyzed with recoveries of 101, 110, and 80% from NIST 1640a (trace elements in water), NIST 1566b (oyster tissue), and DORM-3 (fish protein). In the consumable portion (the muscle fish tissue), the average concentration found was 0.030 ± 0.008 µg g-1, which is below the arsenic maximum level established by international regulatory agencies. The average concentration found in the viscera (stomach, gills, and liver) was 0.485 ± 0.225 µg g-1, concluding that the viscera had greater capacity for the bioaccumulation of arsenic. From this study was possible to monitor the arsenic element in different tilapia specimens evidencing its accumulation throughout the body of the fish.

Application of constrained mixture design and Doehlert matrix in the optimization of dispersive liquid-liquid microextraction assisted by ultrasound for preconcentration and determination of cadmium in sediment and water samples by FAAS

A dispersive liquid-liquid microextraction assisted by ultrasound (USADLLME) with 5-(4-Dimethylaminobenzylidene)Rhodanine procedure has been developed for preconcentration of cadmium in water and sediment samples by flame atomic absorption spectrometry (FAAS). The proportions of mixture composed of disperser, extractor solvents and complexing reagent was optimized using a constrained mixture design. The variables pH, concentration of NaCl and sonication time were optimized using a Doehlert matrix. The precision of method expressed as relative standard deviation (RSD) of 2.92 and 3.38% for 50 and 20μgL−1, respectively, the detection limit was 0.23μgL−1 and the limit of quantification of 0.76μgL−1. The accuracy was confirmed by the analysis of certified reference materials (Drinking Water Standard APS 1071, Fresh Water Sediment 3 RTC 016, Oyster Tissue NIST 1566b, Tomato Leaves NIST 1773a), the Spike test showed recoveries between 90 and 110%. The method was applied to river water, drinking water and sediment, the concentration of cadmium ranged from 1.46–4.60μgL−1 for water samples and from 0.90 to 1.23μgg−1 for sediment samples.

Determination of Na, K, Fe, and Zn whole blood elements concentration of Algerian Alzheimer patients by k 0-NAA method

k0-Standardization method was applied in clinical investigation to evaluate the whole blood correlation factor of Na and K, Fe and Zn of 21 patients suffering from Alzheimer pathology and 5 normal controls. Samples were irradiated at Es-Salam research reactor. However, the concept (QC/QA) is considered to evaluate the accuracy of the method. NIST 1566b (Oyster tissue) and IAEA A13 (animal blood) were analyzed simultaneously with the samples. Three statistical parameters Z-score, U-score and bias were determined and discussed.

Selenium Surveillance: A New Option for China to Examine Selenium Contents in Major Sources of the Chinese Diet

China continues to face severe health effects from selenium overconsumption and underconsumption. To monitor the intake of selenium from foods, we collected 12 kinds of food samples representing major sources of food from 14 provinces in China. We treated samples with nitrate and hydrogen peroxide in microwave digestion. Using Y89 as the internal standard, we determined selenium contents in foods with inductively coupled plasma mass spectrometry (ICP-MS). Detection limit of the method was 0.03 ng/mL; the linear range was between 0-500 ng/mL; and the linear coefficient(r) was better than 0.9995. We evaluated precision and accuracy of testing by analyzing NIST 1568a and 1566b standardized reference materials. On average, selenium contents are 0.02-0.1 mg/kg among milk products, below 0.1 mg/kg among cereals, beans, tubers, vegetables and fruits, sugar, alcoholic and non-alcoholic beverages, 0.10-0.13 mg/k among meats, 0.25-0.50 mg/kg among eggs, 0.6-1.2 mg/kg among animal kidney and liver. Selenium contents vary widely among sea foods from 0.1-1.2 mg/kg. Selenium contents differ significantly among food produced in different regions and are linked with earlier research on the health effects of selenium. This suggests monitoring of major sources of selenium may be a useful marker for identifying early emerging high or low selenium intake patterns in different regions.

Determination of selenium and its compounds in marine organisms

In this study, we investigate the type and quantity of selenium compounds in fish and marine organisms, using ion-pair reversed phase LC–ICP-MS, developed and applied for the analysis of Atlantic cod, Atlantic salmon, Greenland halibut, Atlantic herring, blue mussel, common crab, scallop, calanus, and Euphasia super. Of the samples examined, the lowest level of selenium was found in farmed Atlantic salmon (0.17mgSekg−1dm). The total selenium extraction efficiency by phosphate buffer was 2.5 times higher in sea plankton and shellfish samples than in fish samples. Analysis of Se species in each hydrolysate obtained by proteolysis showed the presence of selenomethionine, which constituted 41.5% of the selenium compounds detected in hydrolysates of Atlantic herring and 98.4% of those in extracts of Atlantic salmon. Inorganic compounds, such as selenates and selenites, were detected mainly in sea plankton and shellfish samples (<0.13mgSekg−1wm), although no correlation was found between the presence of inorganic compounds and total selenium concentration. The accuracy of the total selenium determination was validated using a certified reference material (oyster tissue (NIST 1566b)). A lyophilised powder of cod (Gadus morhua) was used to validate speciation analysis, enzymatic hydrolysis of lyophilised powder of cod recovered 54±6% of total selenium, and SeMet constituted 83.5±5.28% of selenium detected in hydrolysates. The chromatographic detection limits were, respectively, 0.30ngmL−1, 0.43ngmL−1, 0.54ngmL−1, 0.55ngmL−1, 0.57ngmL−1 and 0.72ngmL−1 for selenate, selenomethionine, selenite, Se-methyl-selenocysteine, selenocystine and selenomethionine selenoxide.The data on selenium concentrations and speciation presented here could be useful in estimating levels of selenium intake by seafood consumption.

Magnetic Fe3O4@C nanoparticles modified with 1-(2-thiazolylazo)-2-naphthol as a novel solid-phase extraction sorbent for preconcentration of copper (II)

We report on a new magnetic nanosorbent for solid phase extraction of Cu(II) before its determination by flame atomic absorption spectrometry. The magnetic sorbent is composed of carbon-coated magnetite nanoparticles (Fe3O4@C) synthesized by a single-step solvothermal reaction and then loaded with the chelator 1-(2-thiazolylazo)-2-naphthol. It was used for the preconcentration of Cu(II) ions from water and food samples. The effects of pH value and volume of sample, of type and volume of eluent, and of interfering ions were investigated. Under the optimum conditions, the calibration graph is linear in the 4.0–400 μg L−1 concentration range, with a detection limit of 1.5 μg L−1. The method was validated by using a certified reference material (NIST 1566b; oyster tissue) and applied to the determination of trace copper in spiked water and food samples.

Determination of toxic heavy metals in Echinodermata and Chordata species from South Korea

This study aimed at analysing concentrations of heavy metals including arsenic, lead, cadmium, aluminium and mercury in commonly consumed seafood species belonging to Echinodermata (Anthocidaris crassispina and Stichopus japonicus) and Chordata (Halocynthia roretzi and Styela plicata). The samples were digested by a microwave system and analysed for As, Cd and Pb by inductively coupled plasma mass spectrometer, for Al by inductively coupled plasma-optical emission spectrometer and Hg by Direct Mercury Analyser. The analytical method was validated by determining sensitivity, linearity, precision, spiking recoveries and analysis of the Standard Reference Material (SRM) NIST 1566-b, an Oyster Tissue. Results showed considerably higher accumulation of Al and As in analysed samples, compared to Pb and Cd, while Hg had the lowest contamination. On comparison, the obtained results with the recommended standards by the Food and Agriculture Organization, European Commission and Ministry of Food and Drug Safety of Korea, it was concluded that the analysed seafoods were safe and thus would not pose a threat to consumers.

Multivariate optimization of an analytical method for the analysis of dog and cat foods by ICP OES

Experimental design methodology was used to optimize an analytical method for determination of the mineral element composition (Al, Ca, Cd, Cr, Cu, Ba, Fe, K, Mg, Mn, P, S, Sr and Zn) of dog and cat foods. Two-level full factorial design was applied to define the optimal proportions of the reagents used for microwave-assisted sample digestion (2.0molL−1 HNO3 and 6% m/v H2O2). A three-level factorial design for two variables was used to optimize the operational conditions of the inductively coupled plasma optical emission spectrometer, employed for analysis of the extracts. A radiofrequency power of 1.2kW and a nebulizer argon flow of 1.0Lmin−1 were selected. The limits of quantification (LOQ) were between 0.03μgg−1 (Cr, 267.716nm) and 87μgg-1 (Ca, 373.690nm). The trueness of the optimized method was evaluated by analysis of five certified reference materials (CRMs): wheat flour (NIST 1567a), bovine liver (NIST 1577), peach leaves (NIST 1547), oyster tissue (NIST 1566b), and fish protein (DORM-3). The recovery values obtained for the CRMs were between 80±4% (Cr) and 117±5% (Cd), with relative standard deviations (RSDs) better than 5%, demonstrating that the proposed method offered good trueness and precision. Ten samples of pet food (five each of cat and dog food) were acquired at supermarkets in Aracaju city (Sergipe State, Brazil). Concentrations in the dog food ranged between 7.1mgkg−1 (Ba) and 2.7gkg−1 (Ca), while for cat food the values were between 3.7mgkg−1 (Ba) and 3.0gkg−1 (Ca). The concentrations of Ca, K, Mg, P, Cu, Fe, Mn, and Zn in the food were compared with the guidelines of the United States’ Association of American Feed Control Officials (AAFCO) and the Brazilian Ministry of Agriculture, Livestock, and Food Supply (Ministério da Agricultura, Pecuária e Abastecimento—MAPA).