Simplified multi-element analysis of ground and instant coffees by ICP-OES and FAAS

A simplified alternative to the wet digestion sample preparation procedure for roasted ground and instant coffees has been developed and validated for the determination of different elements by inductively coupled plasma optical emission spectrometry (ICP-OES) (Al, Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, Zn) and flame atomic absorption spectrometry (FAAS) (Ca, Fe, K, Mg, Na). The proposed procedure, i.e. the ultrasound-assisted solubilisation in aqua regia, is quite fast and simple, requires minimal use of reagents, and demonstrated good analytical performance, i.e. accuracy from ?4.7% to 1.9%, precision within 0.5–8.6% and recovery in the range 93.5–103%. Detection limits of elements were from 0.086 ng ml^?1 (Sr) to 40 ng ml^?1 (Fe). A preliminary classification of 18 samples of ground and instant coffees was successfully made based on concentrations of selected elements and using principal component analysis and hierarchic cluster analysis.     

Simple and Fast Sample Preparation Procedure Prior to Multi-element Analysis of Slim Teas by ICP OES

The knowledge about mineral content of slim teas is of great importance since the consumption of these beverages has rapidly increased for the past several years. An increasing popularity of these tea products is mainly attributed to their nutritional properties, flavor, taste and health effects. Therefore, the main goal of the present work was to develop a precise and accurate method of the multi-element analysis of slim teas by inductively coupled plasma optical emission spectrometry (ICP OES) without the need for a laborious and tedious sample treatment preceding spectrometric measurements. Five sample preparation procedures, i.e., the total decomposition in a mixture of HNO₃ and H₂O₂ solutions using closed vessel microwave-assisted or open vessel hot-plate systems, the solubilisation in aqua regia or a tetramethyl ammonium hydroxide solution and the extraction in a diluted HNO₃ solution, were compared. The performance of the compared procedures was determined in terms of the precision and the accuracy of results achieved and limits of detection of elements. It was found that the solubilisation in aqua regia gave the best results, i.e., limits of detection between 0.15 and 98.4 ng l^?1, the precision within 0.6?3.0 % and the accuracy better than 5 %. The developed method of the analysis, being a useful alternative to time-consuming wet digestion procedures, was successfully applied to the analysis of five slim tea products.     

Improvement of Determination of Trace Amounts of Arsenic and Selenium in Slim Coffee Products by HG-ICP-OES

A method for the determination of total inorganic arsenic and selenium in slim instant coffees using hydride generation inductively coupled plasma optical emission spectrometry (HG-ICP-OES) was proposed. Various sample preparation procedures, including the traditional total decomposition by the hot-plate or microwave heating in a HNO₃/H₂O₂ mixture and alternative procedures based on the solubilisation in aqua regia or tetramethyl ammonium hydroxide (TMAH) and the dilution only with water or a low concentrated HNO₃ solution were examined and compared. Corresponding As and Se hydrides were generated in the reaction of an acidified sample solution with the NaBH₄ reductant in the presence of antifoam A. A small sample preparation with aqua regia in an ultrasonic bath followed by the pre-reduction with KI–ascorbic acid in the HCl medium for total As and the boiling with HCl for total Se were found to be optimal. The external calibration using standards treated and measured as the same as samples were applied for the analysis. Limits of detection (LODs) of 0.96 and 0.55 ng ml^?1 were assessed for As and Se, respectively. The precision (as the relative standard deviation [RSD]) was within 1.6–7.1 %. The accuracy of the method was confirmed by the recovery test and the analysis of a standard reference material (non-fat milk powder, SRM 1459). The developed procedure was applied for the analysis of six commercial instant slim coffee products available in the Polish market and it was found that these products contain traces of As (0.114–0.247 μg g^?1) and Se (0.089–0.137 μg g^?1).     

Toxic and nutrient elements in yerba mate (Ilex paraguariensis)

Toxic and nutrient elements were investigated in yerba mate (Ilex paraguariensis) from South America. Fifty-four brands of commercialised yerba mate from Argentina, Brazil, Paraguay and Uruguay were analysed for Al, Ba, Ca, Cu, Fe, K, Mg, Mn, P, Sr, and Zn, using inductively coupled plasma optical emission spectrometry (ICP-OES), and Li, Be, Ti, V, Cr, Ni, Co, As, Se, Rb, Mo, Ag, Cd, Sb, La, Ce, Pb, Bi and U using inductively coupled plasma mass spectrometry (ICP-MS). Antimony, Se, Ag and Bi were not detected in any sample whereas the limits of detection (LODs) of these elements were 0.19, 0.40, 0.003 and 0.001 μg g^?1, respectively. Analysis of variance (ANOVA) revealed that the concentrations of Cd, Ti, Ni, As, Mo, U, Li and Be in yerba mate were not statistically different with regard to the country of origin, while those of the other investigated elements differed.     

Investigation of major and trace elements and their distributions between lipid and non-lipid fractions in Brazil nuts by inductively coupled plasma atomic optical spectrometry

Major (Ca, Mg, P) and trace (As, Al, Ba, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Se, Zn) elements were determined in Brazil nuts by means of inductively coupled plasma atomic optical spectrometry (ICP-OES) and five of them were measured for the first time. For measurement of As, Hg and Se levels, hydride generation was used as the sample treatment method. The element concentrations were compared with recommended dietary allowances and upper tolerable levels. The distributions of the elements between lipid and lipid-free fractions were investigated with the use of solvent extraction. Two extractants (petroleum ether and chloroform:methanol 2:1) were applied. Most of the Cr, Fe and Ni contents were found in the lipid fraction, while Ba, Ca, Cu, Mn, P and Zn were mainly bonded with defatted nut residue. Al, Mg, Se, Sr were only present in the defatted fraction.     

Rapid multi-element analysis of Chinese vinegar by sector field inductively coupled plasma mass spectrometry

An analytical method for simultaneous determination of 20 trace elements in vinegar including Na, Mg, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Sn, Sb, Ba and Pb by sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) with microwave digestion has been established. Sample first underwent microwave digestion with HNO₃ + H₂O₂ followed by dilution with ultrapure water, and then, the as-obtained solution was analyzed directly by SF-ICP-MS. The matrix effects were studied in details and corrected by Sc, In and Re as the internal standard elements. Data accuracy was improved by measuring in medium-resolution mode and high-resolution mode. The applicability of the proposed method has also been validated by the analysis of reference material (NIST SRM 1643e). These results showed that the detection limit of this method is in the range of 0.002–0.34 μg/L with good precision (RSD < 3 %).     

One-step multiplex PCR method for the determination of pecan and Brazil nut allergens in food products

BACKGROUND: A one‐step polymerase chain reaction (PCR) method for the simultaneous detection of the major allergens of pecan and Brazil nuts was developed. Primer pairs for the amplification of partial sequences of genes encoding the allergens were designed and tested for their specificity on a range of food components. RESULTS: The targeted amplicon size was 173 bp of Ber e 1 gene of Brazil nuts and 72 bp of vicilin‐like seed storage protein gene in pecan nuts. The primer pair detecting the noncoding region of the chloroplast DNA was used as the internal control of amplification. The intrinsic detection limit of the PCR method was 100 pg mL^?1 pecan or Brazil nuts DNA. The practical detection limit was 0.1% w/w (1 g kg^?1). The method was applied for the investigation of 63 samples with the declaration of pecans, Brazil nuts, other different nut species or nuts generally. In 15 food samples pecans and Brazil nuts allergens were identified in the conformity with the food declaration. CONCLUSION: The presented multiplex PCR method is specific enough and can be used as a fast approach for the detection of major allergens of pecan or Brazil nuts in food. Copyright © 2011 Society of Chemical Industry     

Brazil nuts and associated health benefits: A review

Epidemiological studies have shown an inverse relationship between nut intakes and chronic diseases such as cardiovascular diseases and cancers. The composition of lipids, minerals, and phytochemicals, and their associated health functions in Brazil nuts are critically reviewed. The nuts have high nutritive food value containing 60–70% oil and 17% protein. Brazil nuts contain abundant dietary antioxidants, especially selenium (Se). One single Brazil nut provides 160% of the US Recommended Daily Allowance (RDA) of selenium - perhaps the best source of Se from plant-based foods. Brazil nuts possess phenolics and flavonoids in both free and bound forms and are rich in tocopherol, phytosterols, and squalene. These compounds' possible beneficial effects are due to their antioxidant and antiproliferative activities, which are linked to a reduced risk for developing atherosclerosis and cancer.     

Application of High-Performance Liquid Chromatography with Diode Array Detector for Simultaneous Determination of 11 Synthetic Dyes in Selected Beverages and Foodstuffs

A simple, inexpensive and robust high-performance liquid chromatography diode array detector (HPC-DAD) procedures are proposed to analyse food dyes in beverages, hard candy and fish roe samples. An ether-linked phenyl stationary phase provides sufficient selectivity and chromatographic performance for separation of 11 sulfonated azo dyes. Beverage samples were only diluted (and degassed when needed) before analysis. Solid-phase extraction (SPE) or matrix solid-phase dispersion (MSPD) procedures are proposed for efficient extraction of the analytes from candies or fish roe samples, respectively. Limits of detection (LODs) were from 0.005 to 0.013 μg mL^?1 and limits of quantification (LOQs) between 0.014 and 0.038 μg mL^?1. HPLC-DAD method was validated in terms of intra- and inter-day accuracy and precision at three concentration levels 2, 1, and 0.1 μg mL^?1. Validation was also performed for SPE and MSPD extraction procedures including intra- and inter-day accuracy (Recovery %) and precision (RSD%), as well as intra-laboratory reproducibility. Application to analysis of beverages and food samples available to consumers proved that described methods are suitable for the routine analysis of dyes in food products.     

Determination of aflatoxin risk components for in-shell Brazil nuts

A study was conducted on the risk from aflatoxins associated with the kernels and shells of Brazil nuts. Samples were collected from processing plants in Amazonia, Brazil. A total of 54 test samples (40?kg) were taken from 13 in-shell Brazil nut lots ready for market. Each in-shell sample was shelled and the kernels and shells were sorted in five fractions: good kernels, rotten kernels, good shells with kernel residue, good shells without kernel residue, and rotten shells, and analysed for aflatoxins. The kernel?:?shell ratio mass (w/w) was 50.2/49.8%. The Brazil nut shell was found to be contaminated with aflatoxin. Rotten nuts were found to be a high-risk fraction for aflatoxin in in-shell Brazil nut lots. Rotten nuts contributed only 4.2% of the sample mass (kg), but contributed 76.6% of the total aflatoxin mass (µg) in the in-shell test sample. The highest correlations were found between the aflatoxin concentration in in-shell Brazil nuts samples and the aflatoxin concentration in all defective fractions (R ^2?=?0.97). The aflatoxin mass of all defective fractions (R ^2?=?0.90) as well as that of the rotten nut (R ^2?=?0.88) were also strongly correlated with the aflatoxin concentration of the in-shell test samples. Process factors of 0.17, 0.16 and 0.24 were respectively calculated to estimate the aflatoxin concentration in the good kernels (edible) and good nuts by measuring the aflatoxin concentration in the in-shell test sample and in all kernels, respectively.     

Optimization of Sample Preparation in the Determination of Minerals and Trace Elements in Honey by ICP-MS

In this paper, analytical procedures are proposed for determination of inorganic constituents in honey samples from different regions of Brazil. Inductively coupled plasma with mass spectrometry detection (ICP-MS) was used to determine the analytes, using two different sample preparation methods: acid mineralization in block digester and microwave-assisted acid digestion. The methods were optimized in order to minimize the final acidity and the residual carbon content after the sample preparation. It was observed that mineralization using microwave radiation with 2 mol L^?1 HNO₃ was the most suitable method for determination of minerals and trace elements by ICP-MS. Besides, Se, Mg, Ca, Al, P, Mn, Fe, Cu, Zn, Ba, and Pb were determined in 60 honey samples by ICP-MS. The appropriate instrumental conditions were also evaluated for this determination, as the need of the use of collision–reaction interface and internal standards. The accuracies were evaluated using two certified reference materials, and the recoveries ranged from 82 to 115 %. The results showed no evidence of contamination in the honey samples analyzed.     

Magnetic effervescent tablet-assisted ionic liquid dispersive liquid–liquid microextraction of selenium for speciation in foods and beverages

A novel, simple and rapid method based on magnetic effervescent tablet-assisted ionic liquid dispersive liquid–liquid microextraction (MEA-IL-DLLME) followed by graphite furnace atomic absorption spectrometry (GFAAS) determination was established for the speciation of selenium in various food and beverage samples. In the procedure, a special magnetic effervescent tablet containing CO₂ sources (sodium carbonate and sodium dihydrogenphosphate), ionic liquids and Fe₃O₄ magnetic nanoparticles (MNPs) was used to combine extractant dispersion and magnetic recovery procedures into a single step. The parameters influencing the microextraction efficiency, such as pH of the sample solution, volume of ionic liquid, amount of MNPs, concentration of the chelating agent, salt effect and matrix effect were investigated and optimised. Under the optimised conditions, the limits of detection (LODs) for Se(IV) were 0.021 μg l^–1 and the linear dynamic range was 0.05–5.0 μg l^–1. The relative standard deviation for seven replicate measurements of 1.0 μg l^–1 of Se(IV) was 2.9%. The accuracy of the developed method was evaluated by analysis of the standard reference materials (GBW10016 tea, GBW10017 milk powder, GBW10043 Liaoning rice, GBW10046 Henan wheat, GBW10048 celery). The proposed method was successfully applied to food and beverage samples including black tea, milk powder, mushroom, soybean, bamboo shoots, energy drink, bottled water, carbonated drink and mineral water for the speciation of Se(IV) and Se(VI) with satisfactory relative recoveries (92.0–108.1%).     

Toxic and micronutrient elements in organic,brown and polished rice in Brazil

Concentration levels of As, Cd, Hg, Pb, Tl, Sn, Sb Co, Cu, Mn, Se, Zn, Cr, Ni and Mo in different types of rice cultivated in irrigated fields in Brazil were evaluated. Arsenic, Cd, Pb, Zn, Mn and Cu were found in higher concentrations in brown rice samples, suggesting the prevalence of these elements in the bran. Meanwhile, lower concentrations of Pb, Mo, Cr, Se and Co were found in parboiled rice. Organic rice did not differ of cultivated conventionally rice. Thallium, Hg and Sb were not detected in any rice sample whose limits of detection were 0.7 μg kg^?1, 2.5 μg kg^?1 and 8 μg kg^?1, respectively. The concentrations of the investigated elements were compared with those reported for polished rice and brown rice from other countries, unveiling concentrations in general at the same level for rice produced at non-contaminated sites.     

Determination of Toxic Elements in Nuts by Inductively Coupled Plasma Mass Spectrometry after Microwave-Induced Combustion

Microwave-induced combustion (MIC) of nuts in closed vessels was evaluated as a sample preparation method for further determination of As, Cd, and Pb by inductively coupled plasma mass spectrometry (ICP-MS) and Hg by flow injection cold vapor generation coupled to ICP-MS (FI-CVG–ICP-MS). Conventional microwave-assisted acid digestion (MW-AD) in pressurized vessels was also used for results comparison. Samples were wrapped in polyethylene films and combusted using 20 bar of oxygen and 50 μl of 6 mol l^?1 ammonium nitrate as aid for ignition. Sample masses up to 500 mg of hazelnuts, almonds, cashew nuts, Brazil nuts, and walnuts were combusted using 7 mol l^?1 HNO₃ as absorbing solution. Accuracy was evaluated using certified reference materials and an agreement better than 96% was obtained for all analytes. Using MIC, it was possible to obtain lower limits of detection (LODs) in comparison with those obtained by MW-AD. The LOD obtained using MIC was 3, 2, and 6 ng g^?1 for As, Cd, and Pb, respectively. The LOD for Hg by FI-CVG–ICP-MS was 7 ng g^?1. Residual carbon content obtained after decomposition by MW-AD and MIC was 20% and lower than 1.5%, respectively, showing the high efficiency of MIC and allowing the determination of toxic elements in samples with high fat content. With the use of MIC up to eight samples could be processed simultaneously and only diluted nitric acid was required minimizing physical interferences, reagent consumption, and waste generation.     

电感耦合等离子体质谱法(ICP-MS)测定砂糖中31种微量元素

利用微波消化－电感耦合等离子体质谱法（ＩＣＰ－ＭＳ）同时测定了白砂糖和赤砂糖中３１种微量元素。白砂糖中检测出２３种,赤砂糖中检出２７种。结果表明,Ｃａ,Ｍｇ,Ｋ,Ｆｅ,Ｍｎ,Ｃｕ等６种元素在赤砂糖中含量比在白砂糖中含量高出４￣４００倍。Ｌｉ,Ｂａ,Ｎａ,Ｐ,Ａｌ,Ｖ,Ｃｒ,Ｎｉ,Ｚｎ,Ｇａ,Ｓｒ,Ａｇ,Ｓｎ,Ｓｈ,Ｂａ,Ｈｇ,Ｐｂ等１７种元素在白砂糖和赤砂糖中的含量无显著差别。本方法具有前处理简单     

Geographical Characterization of Beans Based on Trace Elements After Microwave-Assisted Digestion Using Diluted Nitric Acid

In this paper, multivariate optimization was applied for the development of microwave-assisted digestion using diluted nitric acid for the determination of essential (Ca, Co, Cr, Cu, K, Mg, Mn, Mo, Ni, P, Se, and Zn) and nonessential (Al, As, Ba, Pb, and Sr) elements in bean samples. Three variables (nitric acid concentration, temperature, and processing time) were regarded as factors in the optimization study. The optimum working conditions were as follows: 4.0 mol?L^?1 nitric acid, 190 °C, and a 15-min reaction time for step 4, which required a microwave heating program. The proposed procedure was then applied to bean samples from small producers of Bahia and to samples acquired from markets of Salvador, Bahia, Brazil. Pattern recognition techniques were applied to the data sets to characterize samples in relation to their geographical origin, species, and production mode. Some differences were found in the samples taken from the northeastern, central, and southern parts of Brazil.     

A novel real-time polymerase chain reaction method for the detection of macadamia nuts in food

A real-time PCR-based method for the detection of macadamia nuts (fruits of Macadamia integrifolia or M. tetraphylla or their hybrids) in food products is described. The method consists of DNA isolation by chaotropic solid phase extraction and subsequent PCR with macadamia-specific primers and a TaqMan fluorescent probe. The primers and the probe were targeted to the gene encoding for vicilin precursor. The method was positive for M. integrifolia and M. tetraphylla and negative for 16 other plant species used in food industry, including peanuts, walnuts, hazelnuts, almonds, pistachio nuts, cashew nuts, Brazil nuts, and chestnuts. The DNA-based detection limit of the method was 1.45 pg. Using a series of model samples with defined macadamia nut contents, a practical detection limit of 0.02% (w/w) macadamia nuts was determined. Practical applicability of the PCR method was tested by the analysis of 14 confectionery samples. For all of the samples, results conforming to the labeling were obtained. The presented PCR method is useful for relatively fast, highly selective, and moderately sensitive detection of macadamia nuts in food samples.     

Determination of sub-ng g–1 levels of total inorganic arsenic and selenium in foods by hydride-generation atomic absorption spectrometry after pre-concentration

ABSTRACT

A new and simple ultrasonic-assisted extraction (UAE) procedure was developed for the determination of inorganic arsenic and selenium in foods by hydride-generation atomic absorption spectrometry (HG-AAS). The various analytical variables affecting complex formation and extraction efficiency were investigated and optimised. The method is based on selective complex formation of As(III) and Se(IV) in the presence of excess As(V) and Se(VI) with toluidine red in the presence of tartaric acid at pH 4.5, and then extraction of the resulting condensation products into the micellar phase of non-ionic surfactant, polyethylene glycol dodecyl ether, Brij 35. Under optimised conditions, good linear relationships were obtained in the ranges of 4–225 and 12–400 ng l^–1 with limits of detection of 1.1 and 3.5 ng l^–1 for As(III) and Se(IV), respectively. The repeatability was better than 3.9% for both analytes (n = 10, 25 ng l^–1) while reproducibility ranged from 4.2% to 4.8%. The recoveries of As(III) and Se(IV) spiked at 25–100 ng l^–1 were in the range of 94.2–104.8%. After pre-concentration of a 5.0 ml sample, the sensitivity enhancement factors for As(III) and Se(IV) were 185 and 140, respectively. Accuracy was assessed by analysis of two standard reference materials (SRMs) and spiked recovery experiments. The method was successfully applied to the accurate and reliable determination of total As and total Se by HG-AAS after pre-reduction with a mixture of L-cysteine and tartaric acid. Finally, the method was shown to be rapid and sensitive, with good results for extraction, pre-concentration and determination of total As and Se contents (as As(III) and Se(IV)) from food samples.     

Predominant mycobiota and aflatoxin content in Brazil nuts

The Brazil nut (Bertholletia excelsa) is an economically important product to the Brazilian Amazon. Currently, its marketing is being affected by the high incidence of aflatoxins (AF) produced by potentially aflatoxigenic fungi associated with its seeds. In this context, the purpose of this study was to determine which part of the nut contributes to contamination by aflatoxins and to identify the mycobiota in Brazil nut samples. Unshelled and shelled nuts were analyzed by measuring the total count of filamentous fungi (Aspergillus sections Flavi, Nigri and Circumdati) in sanitised and non-sanitised treatments. The isolates identified as Aspergillus section Flavi, the major producers of AF, were plated for determination of their aflatoxigenic potential. To perform the AF analysis, samples of Brazil nuts were treated separately. The AF from the shell and kernel were extracted by chloroform and analysed by the HPLC-FD system in isocratic mode. The Aspergillus section Flavi count was 21.67% lower. The production of AF by the isolated fungi was 30% for sanitised and 23.8% for non-sanitised samples. The concentrations obtained of AFB₁ and AFG₁ were higher than those of AFB₂ and AFG₂. The AFB₁ concentrations of shelled nuts and shell samples were 35.0 and 1.78 μg/kg, respectively. AFB₂ and AFG₂ were detected only in shelled nut samples. The HPLC-FD analysis presented limits of detection (LOD) and quantification (LOQ) of 0.2 and 0.4 μg/kg, respectively.     

Miniaturization of the QuEChERS Method in the Fast Gas Chromatography-Tandem Mass Spectrometry Analysis of Pesticide Residues in Vegetables

Two reduced-scale quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedures, combined with fast gas chromatography-triple quadrupole mass spectrometry (GC-QqQ MS), were developed and then validated for the determination of 35 pesticides in different vegetable products (tomatoes, zucchini, red peppers, and lettuce). The proposed reduced-scale methods, involving the use of only 3 g of sample, were compared with an official European Union method, namely EN15662:2008, based on the use of a 10-g sample. Method validation was performed considering the following figures of merit: recovery, linearity, precision, matrix effects, and limits of detection and quantification. Specifically, recovery was in the 67–126% range, regression coefficients were between 0.991 and 0.999, and coefficients of variation were between 1 and 13% (at the 50 μg kg^?1 level), while limits of quantification were always below European legislation residue limits. Additionally, the measurement of matrix effects confirmed the necessity of matrix-matched calibration. The developed QuEChERS GC-QqQ MS method is both simple and rapid (analysis of six samples in 2.5 h) and is sensitive enough for EU regulation purposes. To demonstrate the applicability of the proposed reduced-scale method, multi-residue analysis was performed on 20 samples.