Occurrence of ochratoxin A in bread consumed in Morocco

One hundred samples of commercial bread purchased from January to October (2006) from retail bakeshops in five different cities (Rabat, Témara, Salé, Casablanca and Meknès) in Morocco were surveyed for the presence of ochratoxin A (OTA) using liquid chromatography coupled to fluorescence detection. The identification of OTA in positive bread samples was confirmed by methyl ester derivatization. Analytical results showed that forty eight (48%) samples were positive with OTA greater than the limit of quantification (LOQ = 0.051 ng/g). Levels of OTA in positive samples ranged between 0.14 and 149 ng/g. The average contamination of bread samples with OTA was 13 ± 1.5 ng/g. The highest frequency of positive samples (61.5%) and the most contaminated sample (149 ng/g) were found in bread commercialized in the Casablanca area. Twenty six of the positive samples exceeded the maximum level of 3 ng/g set by European regulations for OTA in cereals and derivatives. Based in the results presented in this study, the estimated daily intake of OTA from bread was 126 ng/kg bw/day. The present paper is the first ever drafted on the natural occurrence of OTA in bread consumed in Morocco. Data on the daily intake of OTA by the Moroccan population are also estimated for the first time.     

Determination of ochratoxin A content in wheat bread samples collected from the Algarve and Bragança regions, Portugal: Winter 2007

Ochratoxin A (OTA) is a mycotoxin produced by fungi such as Penicillium verrucosum and Aspergillium spp. and has been found to have a variety of potentially deadly toxic effects. The favoured substrate for fungal growth and OTA production appears to be cereals and flour-based products, including bread. Due to the dietary relevance of bread for the Portuguese population, it is imperative that its OTA content remains well within safe quantities. As such, bread samples collected from commercial surfaces across the Algarve region and from the city of Bragança during the winter of 2007 were tested for OTA through extraction with immunoaffinity columns and quantification by liquid chromatography coupled with fluorescence detection. Although OTA content was found to be above the limit of quantification in approximately 60% and 50% of the analysed samples from Algarve and Bragança, respectively, all samples were found to be compliant with European Commission. OTA content reached maximums of 0.49 ng/g in Algarve and 0.43 ng/g in Bragança, and was thus below the maximum limit established by European legislation for bread of 3 ng/g. The results of the present study put the estimated daily intake of OTA from bread at approximately 0.26 ng/kg bw/day in Algarve and 0.38 ng/kg bw/day in Bragança, circa 1.5% and 2.0% of the TDI established by either the EFSA or the FAO/WHO, or over 4.5% and 6.5% if we consider the FAO/WHO advised bread consumption of 250 g/day. These results seem to suggest that, in these two Portuguese regions, OTA contamination is well under control and unlikely to represent a threat to consumer health.     

Selenium content in selected foods from the Saudi Arabia market and estimation of the daily intake

This study was conducted to create a selenium database for the representative food items in Saudi diet and to estimate the dietary selenium intake of Saudi Arabians. Three samples for each food item selected were purchased from the markets. Each pooled sample was analyzed in triplicate by ICP–MS after thorough homogenization. The rich sources of selenium were meats (0.216–0.658 μg/g), eggs (0.226 μg/g) and cereals and cereals products (0.043–0.165 μg/g). Vegetables and fruits contained trace amounts of selenium (0.001–0.067 μg/g). The major food sources of selenium intake were cereals and cereals products (30.2%), legumes (24.7%) and meats (20%). The daily intake of Se was calculated taking into account the concentration of this element in the edible part and the daily consumption data which were derived from two sources, (a) the food balance sheet of KSA given by Food and Agriculture Organization (FAO) and (b) from questionnaires distributed among 200 families in Jeddah. The results showed that the daily intake of Se according to the two sources is 75.00–121.65 μg/person/day.     

Determination of copper,lead, cadmium and zinc content in commercially valuable fish species from the Persian Gulf using derivative potentiometric stripping analysis

This study was performed to determine the concentrations of cadmium, lead, copper and zinc in the edible muscle of pelagic (Scomberomorus commerson, Chirocentrus dorab, Sphyraena jello, Rachycentron conadum, Thunus tonggol, and Tenualosa ilisha) and demersal (Nemipterus japonicas, Epinephelus coioides, Platycephalus indicus, Psettodes erumei, Pomadasys argenteus, and Acanthopagrus latus) fish species from the Persian Gulf during winter and summer. The samples were analyzed by the derivative potentiometric stripping technique; and the results were expressed as μg/g of wet weight. The obtained range of metals in fish species was 0.024–0.111 μg/g for cadmium, 0.057–0.471 μg/g for lead, 0.799–4.790 μg/g for copper and 3.226–11.390 μg/g for zinc. The study revealed that seasonal variation influenced the concentration of metals in the samples. The highest concentration of cadmium, lead, copper and zinc was found in Platycephalus indicus (0.147 μg/g), Acanthopagrus latus (0.534 μg/g), Psettodes erumei (5.294 μg/g) and Psettodes erumei (13.528 μg/g) in winter, respectively. Moreover, demersal fish species had higher cadmium, lead and zinc concentrations, but lower copper content than pelagic ones. Our study demonstrated that the estimated daily and weekly intakes of lead, copper and zinc, and estimated monthly intake of cadmium via consumption of fish flesh were below the PTDI, PTWI and PTMI values established by FAO/WHO.     

Direct determination of bromine in plastic materials by means of solid sampling high-resolution continuum source graphite furnace molecular absorption spectrometry

This work investigates the potential of high-resolution continuum source graphite furnace molecular absorption spectrometry for the direct determination of bromine in polymers, which could be interesting in view of the current regulations restricting the use of organobrominated compounds. The method developed is based on the addition of Ca (300 μg) and Pd (30 μg) to favor the formation of CaBr, which is monitored at the main molecular “lines” (rotational spectra) found in the vicinity of 625.315 nm.It was found that accurate results could be obtained for all the samples investigated (polyethylene, polypropylene and acrylonitrile butadiene styrene certified reference materials) using any of the lines studied and constructing the calibration curve with aqueous standards. Furthermore, the combined use of the main four CaBr lines available in the spectral area simultaneously monitored permits to easily expand the linear range up to 2000 ng, provides a limit of detection of 1.8 ng (1.8 μg g^− 1 for a mass of 1 mg) and further improves precision to values between 3–7% RSD. Overall, the method proposed seems suited for the fast and simple control of these types of samples (approximately 10 min for sample are required), circumventing the traditional problems associated with sample digestion (e.g., losses of volatile compounds), and providing sufficient sensitivity to easily comply with regulations.     

Microwave-assisted purge-and-trap extraction device coupled with gas chromatography and mass spectrometry for the determination of five predominant odors in sediment,fish tissues,and algal cells

Off-flavors are among the most troublesome compounds in the environment worldwide. The lack of a viable theory for studying the sources, distribution, and effect of odors has necessitated the accurate measurement of odors from environmental compartments. A rapid and flexible microwave-assisted purge-and-trap extraction device for simultaneously determining five predominant odors, namely, dimethyltrisulfide, 2-methylisoborneol, geosmin, β-cyclocitral and β-ionone, from the primary sources and sinks is demonstrated. This instrument facilitates the extraction and concentration of odors from quite different matrices simultaneously. This device is a solvent-free automated system that does not require cleaning and is timesaving. The calibration curves of the five odor compounds showed good linearity in the range of 1–500 ng/L, with correlation coefficients above 0.999 (levels = 7) and with residuals ranging from approximately 77% to 104%. The limits of detection (S/N = 3) were below 0.15 ng/L in algae sample and 0.07 ng/g in sediment and fish tissue samples. The relative standard deviations were between 2.65% and 7.29% (n = 6). Thus the proposed design is ready for rapid translation into a standard analytical tool and is useful for multiple applications in the analysis of off-flavors.     

Determination of lead,cadmium and mercury in blood for assessment of environmental exposure: A comparison between inductively coupled plasma–mass spectrometry and atomic absorption spectrometry

A biomonitoring method for the determination of Pb, Cd, and Hg at background levels in whole blood by inductively coupled plasma-mass spectrometry is described. While this method was optimized for assessing Pb, Cd and Hg at environmental levels, it also proved suitable for assessing concentrations associated with occupational exposure. The method requires as little as 200 μl of blood that is diluted 1 + 49 for direct analysis in the inductively coupled plasma-mass spectrometer. Method performance is compared to well-established AAS methods. Initial method validation was accomplished using National Institute of Standards and Technology (NIST) Standard Reference Material 966, Toxic Metals in Bovine Blood. Method detection limits (3s) are 0.05 μg dl^− 1 for Pb, 0.09 μg l^− 1 for Cd; and 0.17 μg l^− 1 for Hg. Repeatability ranged from 1.4% to 2.8% for Pb; 3% to 10% for Cd; and 2.6% to 8.8% for Hg. In contrast, AAS method detection limits were 1 μg dl^− 1, 0.54 μg l^− 1, and 0.6 μg l^− 1, for Pb, Cd, and Hg, respectively. Further performance assessments were conducted over a 2-year period via participation in four international External Quality Assessment Schemes (EQAS) operated specifically for toxic metals in blood. This includes schemes operated by (a) the New York State Department of Health's Wadsworth Center, Albany, NY, USA (b) L′Institut National de Santé Publique du Québec, Centre de Toxicologie du Québec, Canada, (c) Friedrich-Alexander University, Erlangen, Germany, and (d) the University of Surrey, Guildford, UK Trace Elements scheme. The EQAS data reflect analytical performance for blind samples analyzed independently by both inductively coupled plasma-mass spectrometry and AAS methods.     

The role of gamma irradiation on the extraction of phenolic compounds in onion (Allium cepa L.)

The effect of gamma irradiation on the content of total phenolic compounds, especially quercetin (Q), in onion (Allium cepa L.) skin was investigated. Onion skin extracts contained two predominant flavonoid compounds, Q and quercetin-4′-glucoside (Q4′G). After 10 kGy gamma irradiation, the yield of Q in the extracts increased significantly from 36.8 to 153.9 μg/ml of the extract, and the Q4′G content decreased slightly from 165.0 to 134.1 μg/ml. In addition, the total phenolic compound content also increased after irradiation at 10 kGy, from 228.0 μg/g of fresh weight to 346.6 μg/g; negligible changes (237.1–256.7 μg/g) occurred at doses of up to 5 kGy. As we expected, radical-scavenging activity was enhanced remarkably (by 88.8%) in the 10 kGy irradiated sample. A dose-dependent increase in the peak intensity of the electron paramagnetic resonance (EPR) spectra was observed in all irradiated samples, with a maximum increase at 10 kGy. The intensity relative to that of the control was 0.15, and it increased to 1.10 in 10 kGy irradiated samples. The optimum gamma irradiation dose, which is sufficient to break the chemical or physical bonds and release soluble phenols of low molecular weight in onion skin, is about 10 kGy.     

Effects of H3PO4 and KOH in carbonization of lignocellulosic material

Samples of lignocellulosic material, stem of date palm (Phoenix dactylifera), were carbonized at different temperatures (400–600 °C) to investigate the effects of their impregnation with aqueous solution of either phosphoric acid (85 wt%) or potassium hydroxide (3 wt%). The products were characterized using BET nitrogen adsorption, helium pycnometry, Scanning Electron Microscopy (SEM) and oil adsorption from oil–water emulsion (oil viscosity, 60 mPa s at 25 °C). True densities of the products generally increased with increase in carbonization temperature. Impregnated samples (acid/base) showed wider differences in densities at 400 (1.978/1.375 g/cm³) than at 600 °C (1.955/2.010 g/cm³). Without impregnation, the sample carbonized at 600 °C showed higher density of 2.190 g/cm³. This sample has impervious surface with BET surface area of 124 m²/g. Acid-impregnated sample carbonized at 500 °C has the highest surface area of 1100 m²/g and most regular pores as evidenced by SEM micrographs. The amounts of oil adsorbed decreased with increase in carbonization temperature. Without impregnation, sample carbonized at 400 °C exhibited equilibrium adsorption of 4 g/g which decreases to about a half for sample carbonized at 600 °C. Impregnation led to different adsorptive capacities. There are respective increase (48 wt%) and decrease (5 wt%) by the acid- or base-impregnated samples carbonized at 600 °C. This suggests higher occurrence of oil adsorption-enhancing surface functional groups such as carbonyl, carboxyl and phenolic in the former sample.     

Direct determination of trace rare earth elements in ancient porcelain samples with slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry

A method for the direct determination of trace rare earth elements in ancient porcelain samples by slurry sampling fluorinating electrothermal vaporization inductively coupled plasma mass spectrometry was developed with the use of polytetrafluoroethylene as fluorinating reagent. It was found that Si, as a main matrix element in ancient porcelain sample, could be mostly removed at the ashing temperature of 1200 °C without considerable losses of the analytes. However, the chemical composition of ancient porcelain sample is very complicated, which makes the influences resulting from other matrix elements not be ignored. Therefore, the matrix effect of ancient porcelain sample was also investigated, and it was found that the matrix effect is obvious when the matrix concentration was larger than 0.8 g l^− 1. The study results of particle size effect indicated that when the sample particle size was less than 0.057 mm, the particle size effect is negligible. Under the optimized operation conditions, the detection limits for rare earth elements by fluorinating electrothermal vaporization inductively coupled plasma mass spectrometry were 0.7 ng g^− 1 (Eu)–33.3 ng g^− 1(Nd) with the precisions of 4.1% (Yb)–10% (La) (c = 1 μg l^− 1, n = 9). The proposed method was used to directly determine the trace rare earth elements in ancient porcelain samples produced in different dynasty (Sui, Ming and Qing), and the analytical results are satisfactory.     

Iron,copper, zinc and bromine mapping in cirrhotic liver slices from patients with hemochromatosis studied by microscopic synchrotron radiation X-ray fluorescence analysis in continuous scanning mode

Iron (Fe) and copper (Cu) are essential metals in physiological cell metabolism. While Fe is easy to determine biochemically in histological slices, Cu and zinc (Zn) distribution is frequently critical in confirming the presence of an overload in disturbed Fe/Cu metabolism. To analyze Fe, Cu and Zn in a near histological resolution, energy dispersive microscopic synchrotron radiation X-ray fluorescence was applied.In normal liver tissue, after fixation and imbedding in paraffin, mean Fe, Cu and Zn concentrations were 152 ± 54, 20.1 ± 4.3 and 88.919.5 μg/g sample weight, respectively. No substantial, characteristic differences in their distribution were found in the two-dimensional scans. In slices from patients with hemochromatosis mean Fe, Cu and Zn concentrations were 1102 ± 539, 35.9 ± 14.6 and 27.2 ± 6.7 μg/g sample weight, respectively. Additionally, a significant decrease in phosphorus and sulphur concentrations existed. An increased Cu around cirrhotic regenerations nodules is mostly associated with a lymphocytic infiltration in this region. Analyzing concentrations of Fe in different regions of the samples show a clear negative dependency between Fe and Cu, Cu and Zn, but a positive one between Fe and Zn.Conclusion: With a focal beam size of 15 μm in diameter a resolution of the elemental distribution was achieved which is widely comparable with stained histological slices (20× light microscope). The analysis of simultaneous determined elements reveals metabolic differences between Fe, Cu and Zn in liver tissue from patients with hemochromatosis.     

Analysis of total and dissolved heavy metals in surface water of a Mexican polluted river by total reflection X-ray fluorescence spectrometry

The present area of study is located in the Upper Course of the Lerma River (UCLR). The Lerma is one of the most important rivers of Mexico, where it drains highly populated and industrialized regions. The aim of the present study is to determine the heavy metal concentration of Cr, Mn, Fe, Cu and Pb in dissolved and total phases of the UCLR by means of Total Reflection X-ray Fluorescence Spectrometry (TXRF). The surface water samples were collected at 8 sites distributed following the stream flow direction of the river. Four sampling campaigns were carried out in each site in a 1-year period. A sample preparation method was applied in order to obtain the total and dissolved fraction and to destroy the organic matter. The total heavy metal average concentration decrease in the following order: Fe (2566 μg/L) > Mn (300 μg/L) > Cu (66 μg/L) > Cr (21 μg/L) > Pb (15 μg/L). In general, the heavy metal concentrations in water of the UCLR are below the maximum permissible limits.     

Palladium(II) complexes with the new P,N-type ligand (2-oxazoline-2-ylmethyl)di-isopropylphosphine as intermediates in CO/ethylene or CO/methyl acrylate insertion

The ligand (i-Pr)₂PCH₂(oxazoline) (1a), of the P,N-donor type, was reacted with [PdMeCl(COD)] to yield the square planar methylpalladium(II) complex [PdClMe(P,N)] (P,N = 1a) (2a), from which the complex [PdMe(P,N)OTf] (OTf = OSO₂CF₃) (3a) was obtained by AgOTf-promoted chloride abstraction. The alkyl complexes

(P,N = 1a) (5a, R = H; 7a, R = C(O)OMe) have been isolated from the initial CO/ethylene or CO/methyl acrylate insertion steps into the Pd–Me bond of 3a, respectively, and spectroscopically characterized. Complexes 2a, 3a and 7a have been fully characterized by single crystal X-ray diffraction. Complex 7a is still a rare example of a structurally characterized CO/methyl acrylate stepwise insertion product. These complexes are relevant to the alternating copolymerization of olefins and carbon monoxide catalyzed by palladium complexes. In addition, the centrosymmetric dinuclear complex trans-[Pd(μ-Cl){(i-Pr)₂PCH₂(oxazoline)}]₂(OTf)₂ (6) has been obtained and characterized by X-ray diffraction; it appears to be the first dinuclear complex of the type [Pd(μ-Cl)(P,N)]₂ to be characterized by X-ray crystallography.

Résumé

Le ligand (i-Pr)₂PCH₂(oxazoline) (1a), de type donneur P,N, réagit avec [PdClMe(COD)] pour former le complexe plan carré méthylpalladium(II) [PdClMe(P,N)] (P,N = 1a) (2a), à partir duquel le complexe [PdMe(P,N)OTf] (OTf = OSO₂CF₃) (3a) a été obtenu par abstraction de chlorure à l'aide de AgOTf. Les complexes alkyles

(P,N = 1a) (5a, R = H; 7a, R = C(O)OMe), ont été isolés lors des premières étapes d'insertion de CO/éthylène ou de CO/acrylate de méthyle, respectivement, dans la liaison Pd–Me de 3a, et caractérisés par méthodes spectroscopiques. Les complexes 2a, 3a et 7a ont été complètement caractérisés par diffraction des rayons X sur monocristal. Le complexe 7a est un exemple encore rare de produit d'insertion par étapes de CO/acrylate de méthyle qui ait été caractérisé structuralement. Ces complexes sont pertinents pour la copolymérisation alternée d'oléfines et de monoxyde de carbone catalysée par les complexes du palladium. En outre, le complexe dinucléaire centrosymétrique trans-[Pd(μ-Cl){(i-Pr)₂PCH₂(oxazoline)}]₂(OTf)₂ (6) a été obtenu et caractérisé par diffraction des rayons X; il s'agit du premier complexe dinucléaire de type [Pd(μ-Cl)(P,N)]₂ à être caractérisé par diffraction des rayons X.     

Determination of zinc and copper in human hair by slurry sampling employing sequential multi-element flame atomic absorption spectrometry

The present work proposes a direct method based on slurry sampling for the determination of zinc and copper in human hair samples by multi-element sequential flame atomic absorption spectrometry. The slurries were prepared by cryogenic grinding and sonication of the samples. The optimization step was performed using univariate methodology and the factors studied were: nature and concentration of the acid solution, amount sample/slurry volume, sonication time, and particle size. The established experimental conditions are the use of a sample mass of 50 mg, 2 mol L^− 1 nitric acid solution, sonication time of 20 min and slurry volume of 10 mL. Adopting the optimized conditions, this method allows the determination of zinc and copper with detection limits of 88.3 and 53.3 ng g^− 1, respectively, and precision expressed as relative standard deviation (RSD) of 1.7% and 1.6% (both, n = 10) for contents of zinc and copper of 100.0 and 33.3 μg g^− 1, respectively. The accuracy was checked and confirmed by analysis of two certified reference materials of human hair. The procedure was applied for the determination of zinc and copper in two human hair samples. The zinc and copper contents varied from 100.0 to 175.6 and from 3.2 to 32.8 μg g^− 1, respectively. These samples were also analyzed after complete digestion in a closed system and determination by FAAS. The statistical comparison by t-test (95% confidence level) showed no significant difference between these results.     

Cu determination in crude oil distillation products by atomic absorption and inductively coupled plasma mass spectrometry after analyte transfer to aqueous solution

Cu was determined in a wide range of petroleum products from crude oil distillation using flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICP-MS). Different procedures of sample preparation were evaluated: (i) mineralization with sulfuric acid in an open system, (ii) mineralization in a closed microwave system, (iii) combustion in hydrogen–oxygen flame in the Wickbold's apparatus, (iv) matrix evaporation followed by acid dissolution, and (v) acidic extraction. All the above procedures led to the transfer of the analyte into an aqueous solution for the analytical measurement step. It was found that application of FAAS was limited to the analysis of the heaviest petroleum products of high Cu content. In ICP-MS, the use of internal reference method (with Rh or In as internal reference element) was required to eliminate the matrix effects in the analysis of extracts and the concentrated solutions of mineralized heavy petroleum products. The detection limits (in original samples) were equal to, respectively, 10, 86, 3.3, 0.9 and 0.4 ng g^− 1 in procedures i–v with ETAAS detection and 10, 78, 1.1 and 0.5 ng g^− 1 in procedures i–iii and v with ICP-MS detection. The procedures recommended here were validated by recovery experiments, certified reference materials analysis and comparison of results, obtained for a given sample, in different ways. The Cu content in the analyzed samples was: 50–110 ng g^− 1 in crude oil, < 0.4–6 ng g^− 1 in gasoline, < 0.5–2 ng g^− 1 in atmospheric oil, < 6–100 ng g^− 1 in heavy vacuum oil and 140–300 ng g^− 1 in distillation residue.     

Determination of Pt,Pd and Rh in Brassica Napus using solid sampling electrothermal vaporization inductively coupled plasma optical emission spectrometry

Conventional approaches for the analysis of platinum group elements (PGEs) in plant material suffer from sample digestion which results in sample dilution and therefore requires high sample intakes to maintain the sensitivity. The presented solid-sampling method avoids sample digestion while improving sensitivity when compared to digestion-based inductively coupled plasma optical emission spectrometry (ICP-OES) methods and allows the analysis of sample masses of 5 mg or less. Detection limits of 0.38 μg g^− 1, 0.14 μg g^− 1 and 0.13 μg g^− 1 were obtained for Pt, Pd and Rh, respectively using a sample intake of 5 mg. The reproducibility of the procedure ranged between 4.7% (Pd) relative standard deviation (RSD, n = 7) and 7.1% (Rh) RSD for 25 ng analytes. For quantification, aqueous standards were applied on paper filter strips and dried. Only the dried filters were introduced into the electrothermal vaporization unit. This approach successfully removed memory-effects observed during analysis of platinum which occurred only if liquid standards came into contact with the graphite material of the furnace. The presented method for overcoming the Pt-memory-effects may be of further interest for the analysis of other carbide-forming analytes as it does not require any technical modification of the graphite furnace (e.g., metal inlays, pyrolytic coating). Owing to lack of suitable certified reference materials, the proposed method was compared with conventional ICP-OES analysis of digested samples and a good agreement was obtained. As a result of the low sample consumption, it was possible to determine the spatial distribution of PGEs within a single plant. Significant differences in PGE concentrations were observed between the shoots (stem, leaves) and the roots. Pd was mainly found in the roots, whereas Pt and Rh were also found in higher concentrations in the shoots.     

Heat capacity studies of the iron oxyhydroxides akaganéite (β-FeOOH) and lepidocrocite (γ-FeOOH)

The iron oxides and iron oxyhydroxides exist as several different polymorphs, and a thermodynamic understanding of these polymorphs can provide us with an understanding of their relative stability and chemical reactivity. This study provides heat capacity measurements for lepidocrocite (γ-FeOOH) over the temperature range (0.8 to 38) K and akaganéite (β-FeOOH) over the range (0.7 to 302) K. Fits of the heat capacity of the two samples below T = 15 K showed similar behavior to previously published fits of goethite (α-FeOOH), which required a linear term and an anisotropic gap parameter to model accurately the antiferromagnetic spin–wave contributions. The akaganéite measurements were compared to previously reported measurements all of which showed significant disagreement. It is believed that the measurements reported here are the most reliable. Also, the presence of adsorbed water contributes significantly to the heat capacity of akaganéite, and the standard molar entropy at T = 298.15 K of the hydrated form was calculated to be (81.8 ± 2) J · mol^?1 · K^?1.     

Gamma radiation influence on technological characteristics of wheat flour

This study aimed at determining the influence of gamma radiation on technological characteristics of wheat (Triticum sativum) flour and physical properties of pan breads made with this flour. The bread formulation included wheat flour, water, milk, salt, sugar, yeast and butter. The α-amylase activity of wheat flour irradiated with 1, 3 and 9 kGy in a Gammacell 220 (AECL), one day, five days and one month after irradiation was evaluated. Deformation force, height and weight of breads prepared with the irradiated flour were also determined. The enzymatic activity increased—reduction of falling number time—as radiation dose increased, their values being 397 s (0 kGy), 388 s (1 kGy), 343 s (3 kGy) and 293 s (9 kGy) respectively, remaining almost constant over the period of one month. Pan breads prepared with irradiated wheat flour showed increased weight. Texture analysis showed that bread made of irradiated flour presented an increase in maximum deformation force. The results indicate that wheat flour ionizing radiation processing may confer increased enzymatic activity on bread making and depending on the irradiation dose, an increase in weight, height and deformation force parameters of pan breads made of it.     

Dithizone–chloroform single drop microextraction system combined with electrothermal atomic absorption spectrometry using Ir as permanent modifier for the determination of Cd in water and biological samples

A simple and sensitive method using dithizone–chloroform single drop microextraction has been developed for separation and preconcentration of trace Cd prior to its determination by electrothermal atomic absorption spectrometry with Ir as permanent modifier. Parameters, such as pyrolysis and atomization temperature, solvent type, pH, dithizone concentration, extraction time, organic drop volume, stirring rate and sample volume were investigated. Under the optimized conditions, a detection limit (3σ) of 0.7 ng/l and enrichment factor of 65 were achieved. The relative standard deviation was 7.4% (c = 0.2 μg/l, n = 5). The developed method has been applied to the determination of trace Cd in water samples and biological reference materials with satisfactory results.     

Nanocrystalline bioactive TiO2–chitosan impedimetric immunosensor for ochratoxin-A

Fourier transform infrared (FT-IR) and UV-visible spectroscopy were used to optimize TiO₂ concentration in chitosan (CS) to develop a sensitive CS/TiO₂ bioactive electrode. Electrochemical impedance spectroscopy (EIS) used to measure electro-activity of these bioactive electrodes associated with enhance oligosaccharide containing –CO groups from degradation of CS molecules. This matrix has free –NH₂ and –OH functional groups due to higher probability of hydrogen and covalent bonding between –OH group in CS molecules with Ti–O–Ti which supported immobilization of rabbit antibodies (IgGs) and proteins. Ochratoxin A (OTA) was detected and showed a linear response up to 10 ng/mL with CS/TiO₂ bio-electrode. The OTA detection sensitivity of 7.5 mM TiO₂ added CS bioactive electrode was four times higher than only CS.