Multielement Determination Research Articles

Classification of cowpea beans using multielemental fingerprinting combined with supervised learning

Multielemental compositions (Ag, As, Ba, Be, Cd, Cs, Co, Cr, Cu, Mo, Ni, Pb, Sb, Se, Sn, Sr, Tl, Rb, V, and Zn) of 106 cowpea bean samples belonging to different varieties collected from the province of Corrientes in Argentina were determined using inductively coupled plasma mass spectrometry (ICP-MS). Based on the multielemental data, five supervised learning techniques, namely, linear discriminant analysis (LDA), partial least square discriminant analysis (PLS-DA), k nearest neighbors (k-NN), random forest (RF), and support vector machine (SVM) with radial basis function Kernel, were computed aiming at building classification models that allow one to predict the botanical variety of the samples based on their element profiles. The best classification performance was obtained by SVM with 93% accuracy rate. The model developed through this method enabled the correct separation of the samples into the five cowpea varieties investigated, where 100% sensitivity was achieved for most of the predicted classes. Thus, SVM was the algorithm selected for the classification of the cowpea beans according to their botanical variety. Multielemental determination coupled with supervised pattern recognition techniques have proved to be an interesting approach for differentiating a diverse range of cowpea genotypes. This study has contributed toward generalizing the use of multielemental fingerprinting as a promising tool for testing the authenticity of cowpea beans on a global scale.

Optimization and validation of a fast digestion method for the determination of major and trace elements in breast milk by ICP-MS

Breast milk guarantees all the nutrients required by infants during their first few months of life and remains the most important food source for their health and growth. However, the mother may transfer potentially toxic chemicals to the suckling infant through breastfeeding. The aim of this study was to optimize and validate a fast method for the determination of a total content of 34 elements (Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cs, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, Sb, Se, Si, Sn, Sr, Te, Ti, Tl, U, V, and Zn) in liquid and lyophilized breast milk. The samples were subjected to HNO3:H2O2 (2:1) digestion in an open vessel heated in a water bath (WBD; 80 °C) and subsequently analysed by quadrupole inductively coupled plasma mass spectrometry equipped with a collision-reaction interface.The performance of the proposed method was evaluated in terms of selectivity, detection and quantification limits, linearity, accuracy, and robustness by using standard reference materials and filed samples of breast milk. Compared to microwave-assisted acid digestion, the proposed open vessel digestion allows a significant reduction in treatment time and sample manipulation, while maintaining a similar analytical performance. Masses of 0.5 g of breast milk were efficiently digested with the WBD treatment allowing a residual carbon content lower than 60 mg L−1 and a residual acidity lower than 0.87 mol L−1 in final digested samples. Thus, it shows great potential for application to routine analysis. The method provides satisfactory detection limits and good performance (trueness and recovery percentages 80–111%; coefficient of variation <10%; and relative repeatability <15%) and allows a high sample throughput for multi-elemental determination in human biomonitoring studies.

Multi-element determination of Cd, Pb, Cu, V, Cr, and Mn in ethanol fuel samples using energy dispersive X-ray fluorescence spectrometry after magnetic solid phase microextraction using CoFe2O4 nanoparticles

In this study, multi-element determination in ethanol fuel samples using energy dispersive X-ray fluorescence spectrometry (EDXRF) combined with magnetic solid phase microextraction (MSPME) was explored. The extraction and preconcentration of Cd, Pb, Cu, V, Cr, and Mn from ethanol fuel samples using CoFe2O4 nanoparticles impregnated with 1-(2-pyridylazo)-naphthol (PAN) was carried out for posterior direct determination in the solid phase using EDXRF. Factors such as the concentration of PAN, pH value, time of extraction, and sample volume were optimized. Under the optimized conditions, linear calibration curves were obtained. The precisions for the determination of each element, expressed as relative standard deviations (RSD) of standard solutions containing 0.20 mg L−1 of Cu, Cd, Pb, Cr, V, and Mn and calculated from ten consecutive measurements, were 1.6, 2.8, 2.8, 4.0, 1.5, and 4.5%, respectively. The proposed method allowed the determination of metals with detection limits of 0.012, 0.013, 0.016, 0.012, 0.009, and 0.011 mg L−1 for Cu, Cd, Pb, Cr, V, and Mn, respectively. The method was successfully applied to the extraction and determination of Cd, Pb, Cu, V, Cr, and Mn in ethanol fuel samples.

Development, validation and application of an ICP-MS/MS method to quantify minerals and (ultra-)trace elements in human serum

Multi-element determination in human samples is very challenging. Especially in human intervention studies sample volumes are often limited to a few microliters and due to the high number of samples a high-throughput is indispensable. Here, we present a state-of-the-art ICP-MS/MS-based method for the analysis of essential (trace) elements, namely Mg, Ca, Fe, Cu, Zn, Mo, Se and I, as well as food-relevant toxic elements such as As and Cd. The developed method was validated regarding linearity of the calibration curves, method LODs and LOQs, selectivity and trueness as well as precision. The established reliable method was applied to quantify the element serum concentrations of participants of a human intervention study (LeguAN). The participants received isocaloric diets, either rich in plant protein or in animal protein. While the serum concentrations of Mg and Mo increased in participants receiving the plant protein-based diet (above all legumes), the Se concentration in serum decreased. In contrast, the animal protein-based diet, rich in meat and dairy products, resulted in an increased Se concentration in serum.

In Situ Dielectric Barrier Discharge Trap for Ultrasensitive Arsenic Determination by Atomic Fluorescence Spectrometry.

The mechanisms of arsenic gas phase enrichment (GPE) by dielectric barrier discharge (DBD) was investigated via X-ray photoelectron spectroscopy (XPS), in situ fiber optic spectrometer (FOS), etc. It proved for the first time that the arsenic species during DBD trapping, release, and transportation to the atomic fluorescence spectrometer (AFS) are probably oxides, free atoms, and atom clusters, respectively. Accordingly, a novel in situ DBD trap as a GPE approach was redesigned using three-concentric quartz tube design and a modified gas line system. After trapping by O2 at 9.2 kV, sweeping for 180 s, and releasing by H2 at 9.5 kV, 2.8 pg detection limit (LOD) was achieved without extra preconcentration (sampling volume = 2 mL) as well as 4-fold enhancement in absolute sensitivity and ∼10 s sampling time. The linearity reached R2 > 0.998 in the 0.1-8 μg/L range. The mean spiked recoveries for tap, river, lake, and seawater samples were 100-106%; and the measurements of the certified reference materials (CRMs) were in good agreement with the certified values. In situ DBD trap is also suitable to atomic absorption spectrometry (AAS) or optical emission spectrometry (OES) for fast and on-site determination of multielements.

Multielement Determination of Trace Heavy Metals in Water by Microwave-Induced Plasma Atomic Emission Spectrometry after Extraction in Unconventional Single-Salt Aqueous Biphasic System.

For the first time liquid-liquid extraction was used for the preconcentration of heavy metals prior to their determination in water by microwave-induced plasma atomic emission spectrometry (MP-AES). Extraction of Pb(II), Cd(II), Co(II), Ni(II), Zn(II), and Cu(II) was performed in unconventional aqueous biphasic system (ABS) formed by addition of hydrophobic solid salt, namely, tetrahexylammonium bromide, to aqueous sample, with neither organic solvents nor salting-out agents being used. The metal ions were quantitatively recovered with 4-(2-pyridylazo)-resorcinol (PAR). The extract was diluted with ethanol/HCl and introduced directly into an MP-AES instrument. The factors influencing extraction (pH, reagent concentration, phase contact time, etc.) and MP-AES detection parameters were studied and optimized. For the developed method, limits of detection of 1.3, 4.9, 0.06, 1.2, 4.2, and 3.2 μg L-1 were obtained for cadmium, cobalt, copper, nickel, lead, and zinc, respectively, providing from 60- to 500-fold improvement as compared with the analysis without preconcentration. The method was applied for the analysis of two certified reference materials (CRM) of wastewater and surface water as well as the samples of well and seawater. Coupling MP-AES with ABS extraction significantly extends the capabilities of the method, especially for the analysis of high salinity waters.

Development of dried serum spot sampling techniques for the assessment of trace elements in serum samples by LA-ICP-MS

A novel approach for serum analysis by dried matrix spot (DMS) technique is proposed. The methodology consists of sampling filter paper discs (2.7 mm in diameter) containing the large amount of serum retained after a single spotting. Several oxidizers (sodium chlorate, sodium azide, acetic acid, formic acid, 1-butyl-3-methylimidazoliumm chloride/bromide) were tested (oxidizers premixed with the sample before spotting, and papers previously soaked in concentrated additive/oxidizer solutions). Direct multi-element determination (Al, Be, Ca, Cu, Fe, K, Li, Mg, Mn, Mo, Na, P, Rb, Se, V, and Zn) in dried serum spots at very low levels was therefore assessed by laser ablation (LA) coupled with inductively coupled plasma - mass spectrometry (ICP-MS). Laser ablation was performed using a focused Nd: YAG laser beam in lineal scan mode (wavelength 213 nm, laser fluency 2.2 J cm−2, repetition rate 20 Hz, laser spot diameter 90 µm, depth 0 µm, scanning speed 12 µm s−1). Matrix-matched calibration mode and 13C as internal standard (for signal intensities normalization) was used throughout the work. Limits of quantification were found to be from 21 µg L−1 to 221 mg L−1. Repeatability (seven ablations of the same dried serum spot) and reproducibility (two ablations of seven dried serum spot from the same material) offered RSDs below 12% for all analytes, which seems satisfactory for clinical purposes. The method was validated by analyzing several certified reference materials (Seronorm™ level I and II trace elements in serum), and it was applied to several DMS from serum samples from healthy adults.

Examination on simultaneous multi-element isotope ratio measurement by inductively coupled plasma time of flight mass spectrometry

The simultaneous multi-element isotope ratio measurement by inductively coupled plasma time of flight mass spectrometry (ICP-TOFMS) was examined to evaluate the possibility of simultaneous multi-element determination by isotope dilution mass spectrometry (IDMS). Output from the two different ICP-TOFMS instruments (icpTOF and Optimass 9500) were examined and the figures of merit between them were determined from the analytical results of intensity ratios as isotope ratio measurements for 10 elements (137Ba/135Ba, 111Cd/112Cd, 63Cu/65Cu, 69Ga/71Ga, 60Ni/62Ni, 208Pb/206Pb, 107Ag/109Ag, 205Tl/203Tl, 238U/235U and 66Zn/68Zn). For the results, linear calibration curves for all elements, except for 235U obtained by icpTOF, with coefficient of determination (r2) of more than 0.999 could be obtained for both ICP-TOFMS instruments in the range of concentration from 1 ng mL−1 to 100 ng mL−1, even though the sensitivities of elements were slightly different. However, the trends of intensity ratios of elements observed were different between two ICP-TOFMS instruments, especially for heavier elements such as Pb, Tl and U. The icpTOF provided consistent isotope ratios at the concentrations from 1 ng mL−1 to 100 ng mL−1 for most of elements examined, although Optimass 9500 did not provide consistent isotope ratios except for Ba, Ga and Ag. From these analytical results, icpTOF appears to be the better instrument for simultaneous multi-element determination by IDMS compared to Optimass 9500. Consequently, the simultaneous IDMS of Cd, Hg and Pb by icpTOF was demonstrated to examine the possibility of simultaneous multi-element IDMS by ICP-TOFMS and the consistent analytical results with respect to the certified values could be obtained. From these results, it was expected that icpTOF could be used for simultaneous multi-element IDMS to obtain accurate and precise analytical results since it provided consistent isotope ratios of elements.

Nutritional analysis of Spirulina dietary supplements: Optimization procedure of ultrasound-assisted digestion for multielemental determination

Arthrospira platensis and Arthrospira maxima are a type of blue-green microalga used as a dietary supplement (Spirulina). A low time-consuming ultrasound-assisted digestion (UAD) of Spirulina supplements for multielemental determination by microwave induced plasma atomic emission spectrometry (MPAES) was performed. Several parameters such as acid concentration (AC), thermostated water bath (TWB), digestion time (DT) and UAD – probe or bath – affecting the digestion process were evaluated through a full factorial design. Under the optimal conditions −100 °C for TWB, 5% for AC and 10 min for DT- and selecting the bath as the proper UAD system, the concentrations of 15 analytes (Al, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, V, Zn) were reported. The values are in accordance with the recommendation established by Food and Drug Administration (FDA) excepting for Cd. The knowledge of Spirulina multielemental composition contributes to an outstanding nutritional and toxicological report for human health.

Multivariate Optimization for the Development of a Fast and Simple Ultrasound-Assisted Extraction Procedure for Multielemental Determination in Tea Leaves by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES)

The current study describes a fast and efficient procedure of ultrasound-assisted extraction for determination of Ca, Mg, K, Na, Cu, Zn, Mn, and Al in tea leaves by inductively coupled plasma optical emission spectrometry (ICP OES). The variables of procedure were optimized using the Box–Behnken design and the conditions selected were nitric acid concentration (1.0 mol L−1), sonication time (7 min), and sonication temperature (75 °C). The extraction efficiency was calculated using the analyte concentration obtained by a total digestion procedure as reference. Accuracy was confirmed by analysis of certified reference material of apple leaves (NIST 1515) and spinach leaves (NIST 1570a) using the procedure proposed. A statistical evaluation using Student’s t test showed that there is no significant difference between the value obtained with the proposed procedure and the certified value, at 95% confidence level. The proposed procedure was successfully applied and is a good alternative to conventional acid digestion procedure and can be applied to routine analysis for determination of Ca, Mg, K, Na, Zn, Mn, Cu, and Al in tea leaves used for the preparation of infusions.

K0-INAA as a contributor in nutrition and health: multielemental determination in Stevia rebaudiana Bertoni, leaves and stevioside product

Concerned about food safety and considering the advantages that bring the use of the powerful INAA technique based in k0 method, we have decided to perform a complete multi element determination in the leaves and in the product stevioside, of Stevia rebaudiana Bertoni, which use as a sweetener has increased in the last decade. Using Stevia leaves from different origin, thirty seven elements were determined using k0-INAA; copper was quantified using FAAS, while sixteen elements were determined in the stevioside product from different manufacturers. The results indicated that it is necessary to make a strict quality control on the content of elements in leaves, which are used both as a raw material of the stevioside product, as a sweetener.

Nonthermal optical emission spectrometry for simultaneous and direct determination of zinc, cadmium and mercury in spray.

A nonthermal optical emission spectrometric (OES) system is developed for the simultaneous multi-element determination of zinc, cadmium and mercury, with a dielectric barrier discharge (DBD) microplasma generated on the nozzle of a pneumatic micronebulizer as the excitation source. After solution nebulization, zinc, cadmium and mercury are directly atomized and excited in the spray by a DBD microplasma for performing optical emission. The emission spectra are measured with a charge-coupled device (CCD) spectrometer. Various important parameters governing the analytical performance of the nonthermal OES system are scrutinized, encompassing the conditions of sample solution introduction, microplasma formation, signal collection and matrix matching for DBD-OES detection. With the characteristic emission lines of Zn 213.9 nm, Cd 228.8 nm and Hg 253.7 nm as the analytical lines for quantification, the detection limits for the simultaneous determination of Zn, Cd and Hg are 22, 1.6, and 10 μg L-1, respectively, and the corresponding linear ranges are 70-6000, 5-1000, and 35-2000 μg L-1, respectively. The accuracy of the present nonthermal OES system is confirmed by the determination of Zn, Cd and Hg in two certified reference materials, i.e., CRM 176 (city waste incineration ash) and GBW 08608 (water). The proposed nonthermal OES system provides a portable instrument for field analysis in emergency with low cost and low consumption.

A high-throughput method for multi-element determination in green coffee beans using diluted nitric acid and ultrasound energy

This work describes the multivariate development of a straightforward method for multi-element determination based on the use of diluted nitric acid and UAE followed by determination using ICP-OES.

Microwave-assisted digestion using diluted HNO3 and H2O2 for macro and microelements determination in guarana samples by ICP OES

A microwave-assisted digestion procedure using diluted HNO3 and H2O2 was developed for multi-element determination in guarana samples by ICP OES. Optimization step was performed employing a mixture design with pseudocomponents using HNO3, H2O2 and H2O. The analytical signal of each element, residual acidity and residual carbon content were optimized simultaneously using the desirability function. The best condition for digestion of a 250 mg sample mass resulted from a mixture constituted by 1.0 mL of HNO3, 3.0 mL of H2O2 and 6.0 mL of H2O. This condition allowed final digests with residual acidity and residual carbon content of 0.4 mol L−1 and 6.5%, respectively. The method was validated and applied for the determination of K, Ca, Mg, S, P, Cu, Fe, Mn and Zn in 72 guarana seed samples from Bahia state. This work presents unpublished results about the mineral composition of guarana seed samples produced in Bahia state, Brazil.

A Fast Ultrasound-assisted Extraction Sample Preparation for Multi-elemental Determination of Contaminants in Pharmaceutical Ingredients by ICP-MS

A Fast Ultrasound-assisted Extraction Sample Preparation for Multi-elemental Determination of Contaminants in Pharmaceutical Ingredients by ICP-MS

Multi-element determinations in foods from Amazon region by ICP-MS after enzymatic hydrolysis assisted by pressurisation and microwave energy

The use of pressurised solvents (liquids at a high pressure and/or high temperature without reaching the sub–critical point) or microwave energy were investigated to accelerate enzymatic hydrolysis processes of selected foods (Brazil nut, golden berries, acai fruit and heart of palm) from Amazon region for multi–element determinations. The target elements (Ca, Co, Cu, K, Mg, Ni, P and Rb) were released from dried and defatted foods by the action of a protease and an enzyme activator (DTT, dithiothreitol), and they have been evaluated by inductively coupled plasma – mass spectrometry (ICP–MS). The influence of variables inherent to the enzymatic activity (TRIS-HCl concentration, TRIS-HCl volume, pH, temperature, and protease XIV and DTT masses) and factors affecting pressurisation and/or microwave extraction (pressurised time, pressure and microwave extraction steps) on the efficiency of metals leaching were evaluated using a Plackett-Burman 28×3/32 experimental design as screening method. Results shown statistical significance for extraction temperature and TRIS-HCl concentration (confidence interval of 95%) for enzymatic extraction assisted by solvent pressurisation, whereas number of microwave extraction steps and DTT mass have affected enzymatic extraction assisted by microwave energy. After significant variables optimization, extraction procedure times were 7min (7min per sample) and 70min (12min per sample) for enzymatic extraction assisted by pressurisation and microwave energy, respectively. Limits of quantification were found to be from 1.2ngg−1 to 53.8μgg−1 and 0.23ngg−1 to 35.1μgg−1 for enzymatic extraction assisted by pressurisation and microwave energy, respectively. Repeatability of the over–all procedures were generally below 20%. Element contents in Amazon samples were within the 80–1400, 0.03–3.0, <0.58–50, 500–25,000, 60–7480, 0.40–11.0, 70–14,000, 0.4–200μgg−1 ranges for Ca, Co, Cu, K, Mg Ni, P and Rb, respectively.

Evaluation of Multi-Mixtures of Acids for the Sample Preparation of Organic Soil Amendments for Multi-Element Determination by ICP OES

ABSTRACTA method for the simultaneous determination of aluminum (Al), arsenic (As), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), phosphorus (P), lead (Pb), sulfur (S), selenium (Se), vanadium (V), and zinc (Zn) in organic soil amendments using microwave-assisted acid digestion and inductively coupled plasma optical emission spectroscopy (ICP OES) is proposed. Concentrated or diluted acids mixtures (HNO3, HF, HBF4, and H3BO3) combined or not with H2O2 were systematically evaluated in order to achieve the best digestion procedure for masses of around 150 mg of samples. Principal component analysis (PCA) was applied in order to choose the best acid mixture for digestion (3 mL HNO3 + 1 mL HBF4 + 2 mL H2O). The determined concentrations were in accordance with certified values of CRM 029 at the 95% confidence level, according to the Student-t test. This acid mixture was successfully applied for the digestion of four organic soil amendment samples (organic fertilizers, substrates, and soil conditioners) and element determination.

Characterisation and chemometric evaluation of 21 trace elements in three edible seaweed species imported from south-east Asia

This study was performed to delineate a characterisation of 21 trace elements (Al, As, Be, Cd, Co, Cr, Cu, Fe, Hg, Mo, Mn, Ni, Pb, Sb, Se, Sn, Sr, Tl, U, V, and Zn), in 92 samples of edible seaweeds, belonging to three species (Laminaria Japonica, 16; Porphyra Yezoensis, 54; Undaria Pinnatifida, 22) produced in south-eastern Asiatic countries. Analytical method based on inductively coupled plasma mass spectrometry was used. The compliance of samples with current European regulations was investigated and the 26% of samples was found not-compliant for Cd level. The suitability of the method due to multi-elemental determination allowed a multivariate approach to study the differentiation between species and to investigate the contribution of each element in differentiation. Influence of the geographical origin onto trace element profile was evaluated, and correlation study between each pair of elements was performed by Pearson coefficients. Taxonomic genus and, although to a lesser extent, the geographic origin have a great influence on trace element profile. Comparison with other similar studies was also performed. Discussion on safety aspects concerning heavy metal exposure related to seaweed consumption has been addressed, by comparing the tolerable levels of the most important toxic elements and the intake brought by seaweed species. For some toxic metals, such as Al and Cd, a remarkable risk related to seaweed consumption has been assessed, though with differences between species.

Potential Anthropogenic Pollution by Eu as well as Gd Observed in River Water around Urban Area

The anthropogenic pollution by rare earth elements (REEs) in river water around urban area in Japan was investigated based on multielement determination by ICP-MS after solid-phase extraction using a chelating resin. As a result, the potential anthropogenic pollution by Eu as well as Gd was observed for the river water in the Sakai River, which flows across some urban area from Machida-shi, Tokyo, to Fujisawa-shi, Kanagawa. In particular, the potential anthropogenic pollution due to Eu in river water was found for the first time in the world.

Multivariate Optimization of Conditions for Digestion of Wet Feeds for Dogs and Cats Using a Closed Digester Block and Multielement Determination by ICP-OES

A full 24 factorial design was applied to find the best combination of diluted reagents (HNO3 and H2O2), time, and temperature for the digestion of samples of wet feed for dogs and cats using a closed digestion block. The residual carbon concentration (RCC) was used as the response in the factorial design. All variables and their interactions significantly influenced the digestion of the feed samples, as indicated by the RCC. The conditions established for the digestion of 0.05 g (dry mass) wet feed samples were the addition of 3.0 mol/L HNO3 and 5.0% m/m H2O2 in a final volume of 10 mL, followed by heating in a closed digestion block at a temperature of 170°C for 120 min. Analyses were performed by inductively coupled plasma (ICP) optical emission spectrometry (OES). LOQs ranged from 0.2 μg/g (Mg and Sr) to 51 μg/g (P). Accuracy of the analytical method was confirmed through the analysis of the Standard Reference Materials Tomato Leaves (NIST 1573), Apple Leaves (NIST 1515), and Peach Leaves (NIST 1547). The agreement values achieved ranged from 80.2 ± 0.3% for Ba to 113.8 ± 7.1% for Zn (n = 3). Addition and recovery tests were carried out by adding the analytes to a feed sample at two concentration levels, and the recoveries were between 84 ± 6 and 114 ± 10% for macroelements (Ca, K, Mg, and P; n = 3) and between 88 ± 3 and 113 ± 7% for microelements and trace elements (B, Cu, Fe, Sr, and Zn; n = 3). The precision values achieved for the different elements, expressed as RSDs, were better than 7.3% (Zn; n = 3) except for Cu determination, that was 14.6% (n=3). The optimized analytical method was applied to 10 commercial samples of wet feed for cats and dogs, with the concentrations of Al, B, Ba, Ca, Cu, Fe, K, Mg, Mn, P, Sr, and Zn determined by ICP-OES.