Determination of Trace Elements in Vegetable Oils and Biodiesel by Atomic Spectrometric Techniques—A Review

Abstract

The determination of trace elements in edible oils and biodiesel using atomic spectrometric methods is reviewed. Problems related to sample pretreatment for appropriate sample introduction and calibration are addressed as well as the strategies to overcome them. Recent trends aimed at simplifying sample manipulation are presented. The applications and scope of atomic absorption spectrometry (AAS), flame optical emission spectrometry (F-OES), inductively coupled plasma–optical emission spectrometry (ICP-OES), and inductively coupled plasma–mass spectrometry (ICP-MS) techniques for the determination of trace metals in edible oils and biodiesel are discussed, as well as some current instrumental new developments.     

Atomic absorption and inductively coupled plasma–optical emission spectroscopic method for determination of micronutrients and toxic metals in Curcuma longa L. to characterize human health toxicity

Environment-friendly procedures for determination of nutritious and harmful elements in curcuma longa L. and commercially available turmeric powder are presented. Microwave and ultrasound (probe and bath) procedures for sample preparations were adopted and the elements were determined by validated flame atomic absorption and inductively coupled plasma–optical emission spectrometry. Student’s t-test was established whether there was a difference between the sample preparation methods. Trueness of certified values by all methods was ensured which were not differing significantly at 95% level of confidence interval. % recovery and relative standard deviation are in compliance with Food and Drug Administration-USA guidelines for spectrometric determination of elemental composition in food stuffs. Results showed that concentrations of copper, iron, manganese, and zinc found in both types of samples are promising source of nutrition. Exposure to aluminum, cadmium, and lead from consumption of products under investigation was estimated and few sample contents were higher than permissible level suggested by Food and Agriculture Organization-UN. Regarding the food safety monitoring, the proposed methods are rapid and met green chemistry approach can be implemented in laboratories easily for routine analysis.     

Wavelength‐dispersive x‐ray fluorescence measurements on organic matrices: application to milk‐based products

A simple and fast method for the determination of a series of analytes (sodium, magnesium, phosphorus, sulfur, chlorine, potassium, calcium, iron, zinc) in milk‐based products by wavelength‐dispersive x‐ray fluorescence spectrometry was developed and validated. Reference values were obtained by inductively coupled plasma optical emission spectroscopy and by potentiometry for chloride. The investigated samples were commercial products obtained from various parts of the world. Pellets of 4 g were prepared under 2 t pressure. For each sample, three pellets were prepared and analysed. Limits of quantification and repeatabilities were evaluated for the described analytes. Calibrations were established with 29 samples and validation of the method was made using a second set of 29 samples. An evaluation of this alternative method was done by comparison with data from the reference methods, using robust statistics. Copyright © 2004 John Wiley & Sons, Ltd.     

Application of Multivariate Techniques in Optimization of Spectroanalytical Methods

Abstract

The present article describes fundamentals and applications of multivariate techniques used for the optimization of analytical procedures and systems involving spectroanalytical methods such as flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively coupled plasma mass spectrometry (ICP‐MS), considering the main steps of a chemical analysis. This way, applications of experimental designs in optimization of sampling systems, digestion procedures, preconcentration procedures, instrumental parameters of quantification steps of analytical methods, and robustness tests have been summarized in this work.     

Critical Evaluation of Analytical Procedures for the Determination of Lead in Seawater

Abstract: This article presents a critical evaluation of the analytical procedures used for the determination of lead in seawater, which is important because lead is a good indicator of marine pollution caused by human activities. Sampling, storage, and pretreatment techniques are briefly overviewed, including the significance of systematic errors that cannot be corrected later on. The main techniques in this article are electrothermal–atomic absorption spectrometry (ET-AAS), inductively coupled plasma–mass spectrometry (ICP-MS), and voltammetry. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma–optical emission spectrometry (ICP-OES) are treated as well, although their limits of quantification are not sufficient for a determination of lead in unpolluted seawater. Even when separation and preconcentration techniques are applied, these techniques are only capable of detecting lead in polluted coastal seawater. Separation and preconcentration are actually also required for ET-AAS and ICP-MS in order to determine the lowest concentrations of lead found in unpolluted open-ocean seawater, which is still a challenge for the analytical chemist.     

Determination of essential elements (Mn,Fe, Cu and Zn) in herbal teas by TXRF,FAAS and ICP-OES

The aim of this study was the comparison of the results obtained in the determination of the content of essential elements such as Mn, Fe, Cu and Zn in vegetation samples using different analytical approaches, including suspension preparation and total reflection X-ray fluorescence ( TXRF) analysis as well as most commonly used spectroscopic methods in the field of vegetal analysis such as acid digestion in combination with atomic emission (AES) and atomic absorption spectrometry (AAS). In the case of TXRF analysis, two instruments equipped with different X-ray tubes anodes (W and Mo) were used to better evaluate the potential of TXRF for vegetal samples analysis. Analytical figures of merit for the considered methods were determined by the analysis of plant reference materials. The one-way analysis of variance (ANOVA) applied to the analysed and certified values showed that the results were not statistically different at the significance level of p-values <0.05. Therefore, suspension preparation and TXRF analysis proved to be a sustainable and fast analytical alternative to the most commonly used ones involving a previous digestion of the sample and inductively coupled plasma optical emission spectrometry (ICP-OES) or flame atomic absorption spectrometry (FAAS) analysis. Finally, the different analytical approaches were applied to the determination of Mn, Fe, Cu and Zn in a set of herbal teas used for medical purposes.     

Dry Ashing Preparation of (Quasi)solid Samples for the Determination of Inorganic Elements by Atomic/Mass Spectrometry

Abstract:

This work presents an overview of the development of dry ashing preparation techniques for solid and quasisolid sample analysis by atomic and inorganic mass spectrometry, including flame/graphite furnace atomic absorption spectrometry, chemical vapor generation atomic absorption/fluorescence spectrometry, and inductively coupled plasma–optical emission/mass spectrometry. This article also summarizes all of the dry ashing methods reported in the past 20 years. The dry ashing methods applied to sample preparation are classified as electrothermal ashing, microwave ashing, oxygen combustion, and other special ashing methods including laser, ultraviolet (UV)/ozone, and plasma. Moreover, the development of relevant devices is discussed in context.     

Optimization of Arsenic Speciation Conditions in Plant Material by HPLC‐ICPOES

Instrument and extraction methods have been investigated and optimized for arsenic speciation in Chinese Brake ferns (Pteris vittata) by high‐performance liquid chromatography–inductively coupled plasma optical emission spectrometry system components and parameters. The optimum chromatographic conditions were determined to be 30 mM NH₄H₂PO₄ (pH=6) buffer, 1 mL/min flow rate, and 10% methanol. The limits of detection for this method were approximately 80 ng As(III) and 60 ng As(V) per gram of dried fern material. The optimum solvent for extracting arsenic from lyophilized fern material was 50% methanol.     

Direct multielement determination of Cd,Pb, Fe,and Mn in ground coffee samples using energy dispersive X‐ray fluorescence spectrometry

An analytical method was proposed for the quantification of Cd, Pb, Mn, and Fe in ground coffee samples using energy dispersive X‐ray fluorescence (EDXRF) spectrometry. External calibration was possible using the coffee matrix itself as standards with samples previously analyzed by inductively coupled plasma optical emission spectrometry (ICP OES). The ground coffee samples were analyzed in the form of pellets, which were placed in the center of the EDXRF measuring cell for the determination of the analytes. The limits of detection were 62, 55, 86, and 76 μg/kg for Cd, Pb, Fe, and Mn, respectively. Good linearities were obtained for the calibration curves with coefficients of correlation (R) of 0.9959 for Cd, 0.9939 for Pb, 0.9929 for Fe, and 0.9909 for Mn. Precision, evaluated as the relative standard deviation (RSD) of 10 independent measurements of different cataloged samples with an approximate concentration of 400 μg/kg for each analyte, was between 6 and 14% (n = 10), demonstrating that the preparation of the samples in form of pellets was sufficient to perform analyses by EDXRF. The proposed method was applied in the determination of Cd, Pb, Fe, and Mn in ground coffee samples collected in Salvador, Bahia, Brazil. In a parallel comparative procedure, coffee samples were also analyzed by ICP OES after sample pretreatment by acid digestion. A paired Student's t test was carried out (confidence level of 95%, n = 5) and no significant difference was observed between the concentrations obtained by the proposed and comparative methods.     

准分子激光取样与电感耦合等离子体质谱和光谱联用分析仪器研究进展

将准分子激光剥蚀取样后的产物经由电感耦合等离子质谱与光谱分析,从而获得被激光剥蚀样品的元素与同位素含量信息,是迄今为止适应于表面原位微区分析最为重要的分析科学技术手段之一.基于准分子激光剥蚀取样技术分别与电感耦合等离子体质谱或发射光谱技术联用的分析手段,已经被广泛应用于地质学、材料学、环境科学,甚至生命科学领域的原位微...     

Procedures of Separation and Pre‐concentration for Molybdenum Determination Using Atomic Spectrometry—a Review

Abstract

The literature concerning the improvement of atomic and ionic procedures for molybdenum determination through separation and pre‐concentration were updated. Analytical procedures based on flame atomic absorption spectrometry (AAAS), electrothermal or graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma optical emission spectrometry (ICP‐OES), and inductively coupled plasma mass spectrometry were reviewed taking into consideration the preliminary steps, which can enhance the selectivity and sensitivity based on co‐precipitation, solvent extraction, and solid‐phase extraction. Both in‐batch and on‐line procedures were considered.     

Slurry Nebulization in Plasmas for Analysis of Inorganic Materials

Abstract

This review summarizes and discusses the preparation of slurries for analysis of inorganic materials by inductively coupled plasma optical emission spectrometry (ICP‐OES) and inductively coupled plasma mass spectrometry (ICP‐MS). Details about the grinding step for slurry preparation, the stabilization of slurries, and the calibration strategies are critically discussed. Typical applications described in the literature and the state‐of‐the‐art including advantages and limitations of slurry analysis are presented.     

Revisiting the sodium and calcium matrix effects in inductively coupled plasma optical emission spectrometry. Excitation mechanisms by inelastic collisions

Abstract

The dependence of calcium and sodium matrix effects on the total excitation energy of analyte emission signals was used as a tool for the study of excitation mechanisms in radial view mode inductively coupled plasma optical emission spectroscopy. A total of 95 atomic and 66 ionic emission signals of aluminum, cobalt, chromium, iron, magnesium, manganese, nickel, and silicon in the 3.0–17.59?eV energy range were measured at the non-robust plasma operating conditions to facilitate the matrix effect study. Different matrix effects versus total excitation energy relationships were observed regarding the energy interval. The change of sign from negative to positive of the both matrix effect versus total excitation energy relationship observed around 14?eV, in the 12.06–17.59?eV energy range, is interpreted as experimental evidence of the action of two non-thermic excitation mechanisms: Penning ionization from approximately 12 to 14?eV and charge transfer from 14 to 17?eV. Based on the energy resonance principle and total spin conservation Wigner’s Theorem, possible reactions between excited ionic argon and ground state analyte ions were proposed.     

流动注射-电感耦合等离子体发射光谱法测定天然水中的钙和镁

本文采用流动注射－电感耦合等离子体发现光谱联用技术测定了天然水中的钙、镁元素。考察了试液的雾化和曝光时间及载气压力等因素对分析信号的影响。通过与气动连续进样的对比，测出了钙、镁在流动注射进样下的分散系数。本法在测定钙、镁含量高的水性时，不需对试样进行稀释处理。对五个水样中钙、镁的分析结果与EDTA络合滴定法相吻合。     

Sample Preparation for the Determination of Metals in Food Samples Using Spectroanalytical Methods—A Review

Abstract

The present article gives an overview of recent publications and modern techniques of sample preparation for food analysis employing atomic and inorganic mass spectrometric techniques, such as flame atomic absorption spectrometry, chemical vapor generation atomic absorption and atomic fluorescence spectrometry, graphite furnace atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry, and inductively coupled plasma mass spectrometry. Among the most frequently applied sample preparation techniques for food analysis are dry ashing, usually with the addition of an ashing aid, and acid digestion, preferably with the assistance of microwave energy. Slurry preparation, particularly with the assistance of ultrasound, is increasingly used to reduce acid consumption and sample preparation time. Direct analysis of solid samples is gaining importance in the field of food analysis as it offers the highest sensitivity, avoids the use of acids and other aggressive reagents, makes possible the analysis of micro‐samples, and can be applied for fast screening analysis, e.g., of fresh meat.     

Correction factor based on the ratio of the magnesium atom to ion background signals used for evaluating robustness in inductively coupled plasma optical emission spectrometry

The ratio of the magnesium ion to atom signals with wavelengths of 280.270 and 285.213 nm, respectively, is frequently employed to estimate plasma robustness in inductively coupled plasma optical emission spectrometry. To guarantee a rigorous and accurate calculation of this indicator of the plasma condition, a correction for the difference in the response of the instrument at the two wavelengths of magnesium has been frequently applied. However, the literature reviewed shows inconsistencies in the values of the correction factor used. Also it is notable the lack of information concerning the procedures to calculate such correction factor.

In this paper, we propose a simple method for the best estimate of the correction factor from an appropriate measurement of the magnesium atomic and ion background signals, when a blank solution, contaminated by magnesium, is nebulized. We proved that a bad selection of the wavelengths used for background signal estimation can underestimate the correction factor up to a 56%.     

Slurry Sampling—An Analytical Strategy for the Determination of Metals and Metalloids by Spectroanalytical Techniques

Abstract

This article critically overviews the state-of-the-art of slurry sampling as an approach for the minimization of sample preparation prior to the determination of metals and metalloids in complex matrices by spectroanalytical techniques. Relevant factors involved in the optimization of slurry-based analytical procedures and the dependence of the quality of the results on the calibration method selected are discussed in detail. The advantages and limitations compared to solid sampling for the analysis of solid matrices are highlighted and discussed.

Analytical applications of slurry sampling reported in the literature emphasizing publications between 2004 and 2009 are comprehensively compiled covering detection by flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ET-AAS), cold vapor atomic absorption spectrometry (CV-AAS), hydride generation atomic absorption spectrometry (HG-AAS), hydride generation atomic fluorescence spectrometry (HG-AFS), inductively coupled plasma optical emission spectrometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS).     

Electrodeposition study of simulated and dissolution solutions of the positive electrode of a spent Ni-MH battery using the electrochemical quartz crystal microbalance and inductively coupled plasma optical emission spectrometry

Ionics - The use of electrochemical quartz crystal microbalance (EQCM) and inductively coupled plasma optical emission spectrometry (ICP-OES) as well as potentiodynamic and potentiostatic methods...     

Direct determination of mineral nutrients in soybean leaves under vivo conditions by portable X-ray fluorescence spectroscopy

A portable energy dispersive X-ray fluorescence (XRF) spectrometer furnished with an Rh X-ray tube was evaluated for the determination of macronutrients and micronutrients in soybean leaves (Glycine max L.). XRF instrumental parameters were optimized in a univariate way, and emission intensities were measured for 60 s and under vacuum for macronutrients, and during 180 s, under air, and 305 μm Al/25.4 μm Ti filter, for micronutrients. Fresh and dried leaves were irradiated, and it was possible to identify P, K, Ca, S, Mn, Fe, Cu, and Zn Kα emission lines. For comparative purpose, the samples were also microwave assisted, digested and analyzed by inductively coupled plasma optical emission spectrometry. In general, linear correlations between K, Ca, Mn, Fe, Cu, and Zn concentrations in the tested samples and the corresponding portable XRF (pXRF) intensities were obtained. The linear correlation coefficients (R²) ranged from 0.42 to 0.86. In addition, the detection limits were suitable for plant nutrient diagnosis. It is demonstrated that pXRF is a simple and powerful tool for analysis of plant materials.     

Multielement Analytical Spectroscopy in Plant Ionomics Research

Abstract: The study of the ionome (ionomics) is defined as quantitative and simultaneous measurement of the element composition of living organisms and changes in this composition in response to physiological stimuli, development stage, and genetic modifications (Salt et al., Ann. Rev. Plant Biol., Vol. 59, 2008). The necessity of understanding the regulation processes of elements in the organisms demands determination of many elements in the organism, tissue, and cell (Baxter, Plant Biol., Vol. 12, 2009). A prospect for ionomics is environmental pollution where great variety of conditions and pollutants exist resulting in concentration and interelemental changes in the plant ionome. The capabilities of and problems with several multielement analytical techniques, including instrumental neutron activation analysis (INAA), X-ray fluorescence, inductively coupled plasma–atomic emission spectrometry (ICP-AES), inductively coupled plasma–mass spectrometry (ICP-MS), and atomic absorption spectrometry (AAS), which are adequate and most promising in ionomic and environmental studies of plants, are reviewed. References are confined mainly to the last 10–15 years. Information about concentrations, roles, binding forms, and pollution sources of the elements and comparison between methods with respect to limits of detection, determined elements, interferences, and economic considerations are tabulated. Some combinations of instrumental techniques supplementing each other are highly valued, namely, ICP-MS and ICP-AES and INAA and AAS or ICP-AES.