Inductively Coupled Plasma Optical Emission Spectrometry Technique Research Articles

Comparative study of metal concentration determination in albumen of hen eggs originating from industrial poultry farms, backyard and free-range hens using ICP-OES technique

There have been multiple types of research focusing on the relationship between feed ingredients and metal content in the egg white due to their role in human nutrition. The aim of the present study is to determine the metal concentration in hens’ eggs and, in particular, to compare the metal concentration in egg albumen originating from industrial poultry farms with that of backyard and free-range hens. All samples were collected in Romania from five separate counties and 10 different farms, over a period of two weeks and, as a result, a total of 50 were collected, 10 from each housing system (batteries/cages, litter/soil, free-range, organic and backyard). The measurements of the metals were taken by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), with a wide range of elements reported. For the essential elements, we measured Cr, Cu, Fe, Mn and Zn; Al, Cd, Ni and Pb for the heavy metals and, in addition, we measured B, Ba, Sr, Ca and Mg. The present study revealed that the metals in eggs from free-range hens are richer in essential elements with mean concentrations as follows: 1.528 mg/kg for Fe, 3.278 mg/kg for Zn, 0.058 mg/kg for Mn and 1.362 mg/kg for Cu. We concluded that the egg quality is closely connected with the housing system and nutrition. Furthermore, the results demonstrate that eggs from backyard housing are no better than those from free-range hens in terms of essential metal composition. The heavy and non-essential metal contents, present in the albumen of all the examined eggs, were much lower than the maximum allowed concentration and, therefore, egg consumption does not pose any risk to human health.

Challenges in the Application of Dendrochemistry in Research on Historical Environmental Pollution in an Old Copper Mining Area

This research investigates the long-term environmental impact and historical temporal pollution patterns caused by a former copper mine in Iwiny (south-western Poland) using a dendrochemical approach. An additional aspect of this research was considering the possibility of using the inductively coupled plasma-optical emission spectrometry (ICP-OES) measurement technique as a cheaper alternative to inductively coupled plasma mass spectrometry (ICP-MS) in dendrochemical analyses conducted in copper mining areas. In the study area, a tailings storage facility (TSF) dam failure (1967) took place and the alkaline flotation waste containing high concentration of Cu and Pb are stored. Tree cores from pedunculate oak (Quercus robur L.) were analysed for the content of 11 trace elements (TEs) (Cd, Mn, Ni, Zn, Cr, Co, Pb, Cu, Fe, Al, Ag) using the ICP-OES technique, while tree rings’ widths (TRWs) were also measured. Samples that were most significant in the context of the research goals were verified with the ICP-MS method. The results revealed the strong long-term impact of the copper industry as reflected in a substantial increase in the mean contents of: (1) Mn, Ni, Zn, Cr, Pb, Cu and Fe in industrial vs. control trees, (2) TRWs for control vs. industrial trees. However, the observed patterns of TEs and TRWs did not correspond to the known timing of pollution inputs (mining activity, tailings spill). Peak levels were observed for Zn and Fe after the mine was closed. The lack of new sources of pollution and the temporal relationship strongly suggests that the tree rings recorded the chemical signal of the TSF reclamation (the use of fertilizers and agrotechnical interventions). Patterns of 7 elements were detected in most of the samples by ICP-OES (Co and Cd were not detected, Al and Ag were partly detected), while ICP-MS detected all of the elements. Significant differences were obtained for Ag, Cd, and Co. Despite challenges with the application of dendrochemistry in research on old mining areas (e.g., lack of old trees), it has proved to be a useful tool for investigating the aggregate environmental impact.

Synthesis and characterization of aluminum citrate compounds and evaluation of their influence on the formation of hydrogels based on polyacrylamide

Aluminum citrate is used as a conformance control agent to improve oil production and excess water production. This paper discusses the formation of mono and polynuclear aluminum species from the synthesis of aluminum citrate and evaluates these compounds as crosslinkers in hydrogels for conformance control. The products obtained from the synthesis were characterized by Fourier-transform infrared spectrometry (FTIR), elemental analysis (CHN), scanning electron microscopy (SEM), and inductively coupled plasma–optical emission spectrometry (ICP-OES). The FTIR analyses indicated the presence of mononuclear aluminum citrate complexes at pH 3 and polynuclear species starting at pH 4. These results were corroborated by CHN and ICP-OES techniques, which revealed the variation of carbon, oxygen, hydrogen, and alumina precipitate levels as functions of pH variation. The focus of the study was to assess how these crosslinking agents perform in hydrogel formation under reservoir conditions. Rheological analysis showed that the values of tan (delta) of the hydrogel synthesized with aluminum citrate at pH 6 were lower than 0.1, indicating strong gels, while at pH 9, the values were above 0.1, indicating weak gels. These results are in agreement with those obtained by FTIR, which showed that at pH 6, the structures of the aluminum citrate complex were probably in the form [Al3(C6H5O7)3(OH)4(H2O)]4−. This structure appears to allow easier access to the aluminum orbital for the crosslinking process compared to the gel composed of aluminum citrate synthesized at pH 9 [Al3(C6H6O7)3(OH)4(H2O)5]4−.

Assessment of Selected Heavy Metals in Water Samples from Vlora Bay, by using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)

Assessment of Selected Heavy Metals in Water Samples from Vlora Bay, by using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) ValbonaTahiri, Astrit Denaj, Fatjon Musli Abstract In this study is presented an evaluation of Cr, Cu, Fe, Mn and Ni concentration levels in coastal waters ofVlora bay, Albania. Water samples were collected during spring-summer season in seven different sampling stations along three different depth levels: 10cm, 60cm and 120 cm respectively. Water samples were treated according to EPA3015A procedure (Microwave Assisted Acid Digestion of Aqueous Samples and Extracts). The measurements were carried out byOptima 2100™ DV, using ICP-OES technique. By the obtained results it is shown a heterogenicity distribution of heavy metal concentration values. Herein we noticed that Fe concentration level was above the allowed limit. Regarding the correlations, Fe shows: an uphill (positive) linear relationship with Cr, Ni and Mn and a downhill (negative) linear relationship with Cu. Although the coastline of Vlora does not represent a polluted environmental area regarding the concentration levels of heavy metals, it is needed to be monitored continuously since the area is subject to urban, industrial and touristic developments. Full Text: PDF DOI: 10.15640/jaes.v8n2a5

Detection of micro-toxic elements in commercial coffee brands using optimized dual-pulsed laser-induced spectral analysis spectrometry.

A fast detection system based on dual-pulsed laser-induced breakdown spectroscopy (DP-LIBS) was successfully developed and optimized for the estimation of micro-toxic element contents in commercial coffee brands to monitor pollution and ensure food safety. A series of 13 various coffee brands were quantitatively analyzed in this study utilizing DP-LIBS and a standard analytical technique like inductively coupled plasma/optical emission spectrometry (ICP-OES). The micro-toxic elements, such as aluminum (Al), lead (Pb), zinc (Zn), and chromium (Cr), that exist in the coffee brands were exactly identified. We prepared standard matrices in a known concentration in the coffee sample to draw the standard calibration curves for each element, as well as by utilizing a tactic based on the intense line emission of the element of interest as a quantitative analysis. The analytical routines were approved under the expectations that the plasma created by the dual-pulsed lasers was in local thermodynamic equilibrium (LTE) and was optically thin. We investigated the influence of different parametric dependence studies to enhance our DP-LIBS detection sensitivity. Furthermore, the precision of our DP-LIBS data for determining the concentration of micro-toxic elements present in coffee samples was validated via the ICP-OES technique. The results achieved by the DP-LIBS technique were in full agreement with the ICP-OES results. In addition, the estimated limit of detection of our DP-LIB spectrometer for Al, Pb, Zn, and Cr were 105.13±07, 90.17±12, 83.58±15, and 68.78±09 μg L-1, respectively. The suggested protocols demonstrated the excellent benefits of the DP-LIBS for the detection of micro-toxic elements existing in coffee and for checking the purity and quality of food products.

Influence of various parameters on the levels of arsenic in washed scalp hair from Karbala, Iraq by using ICP-OES technique

The use of unconventional biological materials as biomarkers in trace element studies has increased in terms of published research studies. In the present study, human scalp hair samples (n = 65) were used to be a possible biomarker for the arsenic level in the human body as no study has been published in Karbala city, Iraq yet. The level of arsenic was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The validity, precision and accuracy of the methodology were evaluated using a “pooled” sample and certified reference materials, respectively. The validation methods provided acceptable levels of precision and accuracy with lower range of RSD (1.1%) and acceptable range of elemental recovery (97.72%), respectively. The influence of various factors including health status, gender, smoking activity, interaction, individual's age and drinking water on arsenic levels in washed scalp hair was investigated using the analysis of covariance (ANCOVA), analysis of variance (ANOVA), F-test and a two-tailed pooled t-test. The arsenic levels in washed scalp hair of breast cancer patients (8.270 ± 4.345 mg/km) were significantly increased when compared with healthy individuals (6.266 ± 1.892 mg/km) (p < 0.05). It was found that the levels of As were significantly higher in washed scalp hair of males (12.395 ± 6.243 mg/kg) than those for females (7.637 ± 4.234 mg/kg) (P < 0.05). Hair of smokers (16.078 ± 4.245 mg/kg) was significantly contained more As than hair of non-smokers (6.532 ± 2.817 mg/kg). The levels of As in the age group (over 40 year) are significantly different when compared with the two remaining groups (under 20 year, and 20–40 year). The value of correlation coefficient (r = 0.907, p < 0.001) was indicated that there is significant positive correlation between the arsenic level in the scalp hair and the arsenic level in the drinking water.

Selected problems with boron determination in water treatment processes. Part I: comparison of the reference methods for ICP-MS and ICP-OES determinations

The aim of the study was to compare the two reference methods for the determination of boron in water samples and further assess the impact of the method of preparation of samples for analysis on the results obtained. Samples were collected during different desalination processes, ultrafiltration and the double reverse osmosis system, connected in series. From each point, samples were prepared in four different ways: the first was filtered (through a membrane filter of 0.45 μm) and acidified (using 1 mL ultrapure nitric acid for each 100 mL of samples) (FA), the second was unfiltered and not acidified (UFNA), the third was filtered but not acidified (FNA), and finally, the fourth was unfiltered but acidified (UFA). All samples were analysed using two analytical methods: inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The results obtained were compared and correlated, and the differences between them were studied. The results show that there are statistically significant differences between the concentrations obtained using the ICP-MS and ICP-OES techniques regardless of the methods of sampling preparation (sample filtration and preservation). Finally, both the ICP-MS and ICP-OES methods can be used for determination of the boron concentration in water. The differences in the boron concentrations obtained using these two methods can be caused by several high-level concentrations in selected whole-water digestates and some matrix effects. Higher concentrations of iron (from 1 to 20 mg/L) than chromium (0.02–1 mg/L) in the samples analysed can influence boron determination. When iron concentrations are high, we can observe the emission spectrum as a double joined and overlapping peak.

Detection of trivalent-iron based on low-dimensional semiconductor metal oxide nanostructures for environmental remediation by ICP-OES technique

A large-scale synthesis of undoped low-dimensional semiconductor metal oxide nanostructures (ZnO nanoparticles, NPs) by simple wet-chemical method was performed using reducing agents at low temperature. The NPs were characterized in terms of their morphological, structural, and optical properties, and efficiently applied for the metal ions uptake. The detailed structural, compositional, and optical characterizations of the NPs were evaluated by powder X-ray diffraction pattern (XRD), Fourier-transform infra-red spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Electron dispersion spectroscopy (EDS), and UV–vis. spectroscopy, respectively which confirmed that the obtained NPs are well-crystalline undoped ZnO and possessed good optical properties. The ZnO NSs morphology was investigated by FESEM, which confirmed that the calcined materials were spherical shape in nano-level and growth in huge-quantity. The analytical efficiency of newly synthesized ZnO NPs was also investigated for a selective separation of trivalent iron [Fe(III)] prior to its determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). The selectivity of ZnO NPs towards different metal ions, including Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Ni(II), Zn(II), and Zr(IV), was studied. Data obtained from the selectivity study suggested that that ZnO NPs phase was the most selective towards Fe(III). The static uptake capacity of Fe(III) was found to be ~79.80mgg−1. Moreover, adsorption isotherm data also provided that the adsorption process was mainly monolayer on a homogeneous adsorbent surface.

Quantitative elemental analysis of Celocia argentea leaves by ICP-OES technique using various digestion methods

Abstract Aim Quantification of macronutrient, micronutrient and toxic elements from the leaves of Celocia argentea by inductively coupled plasma-optical emission spectrometry (ICP-OES) and to report efficient, reliable, eco friendly method of digestion for better recovery of the elements. Methods The five digestion methods are studied included, dry ashing method with HNO3/HCl, wet digestion method with HNO3/HClO4 and HNO3/H2O2, microwave digestion with HNO3/HClO4 and HNO3/H2O2. ICP-OES operating parameter was optimized at radial and axial viewing along with the radio-frequency power, sample flush time and gas flow rate. The results of the elemental quantification were statistically analyzed using one way analysis of variance (ANOVA) by Kruskal–Wallis test. Results C. argentea exhibits good quantity of macronutrients like Mg, Ca S, P, K and Fe. The ashing and microwave digestion method were found to more reliable as compare to wet digestion method and hence recommended for better recovery. The element Ca, Cu and Fe gives better recovery by ash and microwave digestion method as compare to wet digestion method. Toxic elements show their concentration below permissible limit. Conclusion All the nutrients as well as toxic elements are quantified successfully by ICP-OES technique by all methods of digestion. Dry and wet digestion methods are tedious and time consuming compare to microwave digestion method, which is greener and simpler. Kruskal–Wallis test can be employed for non-parametric methods to compare more than two population average which do not require any specific form of the distribution of the population. The C. argentea can be used as supplementary food for deficiency of minerals like Fe, Mg and Ca.

Development and validation of an ICP-OES method for quantitation of elemental impurities in tablets according to coming US pharmacopeia chapters

May 1, 2014 the United States Pharmacopeia (USP) will implement two new chapters stating limit concentrations of elemental impurities in pharmaceuticals applying inductively coupled plasma methods. In the present work an inductively coupled plasma optical emission spectrometry (ICP-OES) method for quantitation of As, Cd, Cu, Cr, Fe, Hg, Ir, Mn, Mo, Ni, Os, Pb, Pd, Pt, Rh, Ru, V and Zn in tablets according to the new USP chapters was developed. Sample preparation was performed by microwave-assisted acid digestion using a mixture of 65% HNO3 and 37% HCl (3:1, v/v). Limits of detection and quantitation were at least a factor of ten below the USP limit concentrations showing that the ICP-OES technique is well suited for quantitation of elemental impurities. Excluding Os, spike recoveries in the range of 85.3–103.8% were obtained with relative standard deviations (%RSD) ranging from 1.3 to 3.2%. Due to memory effects the spike recovery and %RSD of Os were 161.5% and 13.7%, respectively, thus the method will need further development with respect to elimination of the memory effect of Os. The method was proven to be specific but with potential spectral interference for Ir, Os, Pb, Pt and Rh necessitating visual examination of the spectra. Hg memory effect was handled by using lower spike levels combined with rinsing with 0.1M HCl. The tablets had a content of Fe and Pt of 182.8±18.1 and 2.8±0.2μg/g, respectively and did therefore not exceed the limit concentration defined by USP. It is suggested that the developed method is applicable to pharmaceutical products with a composition and maximal amount of daily intake (g drug product/day) similar to the tablets used in this work.

Method of low tantalum amounts determination in niobium and its compounds by ICP-OES technique

A method of determination of low amounts of tantalum in niobium and niobium compounds without its prior separation by means of inductively coupled plasma optical emission spectrometry (ICP-OES) has been worked out. The method involves dissolution of the analyzed samples of niobium as well as its various compounds (oxides, fluorides, chlorides, niobates(V)) in fluoride environments, precipitation of sparingly soluble niobic(tantalic) acid (Nb2O5(Ta2O5)·xH2O), converting them into soluble complex compounds by means of oxalic acid with addition of hydrogen peroxide and finally analyzing directly obtained solutions by ICP-OES. This method permits determination of Ta in niobium at the level of 10−3% with relatively good precision (≤8% RSD) and accuracy (recovery factor: 0.9–1.1). Relative differences in the results obtained by two independent methods (ICP-OES and ICP-MS) do not exceed 14%, and other elements present in niobium compounds (Ti, W, Zr, Hf, V, Mo, Fe, Cr) at the level of 10−2% do not affect determination.

Determination of Zinc, Copper, Cadmium and Lead in Serum of Patients with Acute Leukemia

The relations between malignant hematological diseases and trace heavy metals in blood have not been understood clearly. Alterations in serum Zn and Cu levels may frequently occur in many neoplastic diseases, including leukemia. Therefore, it is necessary from an analytical point of view to develop sensitive and economical methods for the determination of trace amount of heavy metals and the relationship between changes in concentrations of these metals and the development of hematological malignancies. Differential Pulse Stripping Voltammetry (DPAdSV) is relatively inexpensive and is one of the most sensitive and selective techniques in the determination of trace amounts of metals. The levels of heavy metals such as Zn, Cu, Pb and Cd were determined in the serum of 20 patients with acute leukemia before initial chemotherapeutic treatment and compared to 15 apparently health control group using two different analytical techniques; (DPAdSV) and inductively coupled plasma optical emission spectrometry (ICP-OES). The selection criteria for the patients and controls were the lack of recent blood transfusion history and taking any medication with mineral supplement. The Serum levels of Cu, Zn and Cd were significantly lower with acute leukemia than controls (p=0.003, p=0.035, p=0.014, respectively), while Pb was insignificantly elevated (p=0. 381). Conclusion: In this study, we found the levels of Cu, Zn and Cd to be lowered and of lead to be elevated in patients with acute leukemia. Further studies are needed to clarify the role of these elements in pathogenesis of acute leukemia. And also a comparative study was carried out between the results using DPAdSV and ICP-OES techniques, which are in very good agreement. Keywords-Acute Leukemia, Serum, Stripping Voltammetry, Zinc

Microanalytical characterization of decorations in handmade ancient floor tiles using inductively coupled plasma optical emission spectrometry (ICP-OES)

In this study a total of 114 glazed decorations of 42 ceramic floor tiles, manufactured in Sicily from the 16th to the 21th AD, were investigated. The micro sampling method, proposed by us, using a cotton swab soaked in hydrofluoric acid, includes advantages of high sensitivity, high selectivity, simplicity, speed, not expensive and can be considered non-destructive because the point of sampling remains invisible to the human eye. ICP-OES technique was used in this study. Twenty-four elements (Al, As, B, Be, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Ni, Pb, Sb, Se, Si, Sn, Ti, V and Zn) were determined in each colored enamel.Enameled decorations in Sicilian tiles were varied in tones and chromatic effects, obtained with a limited number compounds of cobalt, copper, iron, manganese, tin, and in the artifacts following the year 1920, also titanium. An important remark is that some of the colors, such as black, orange, purple and brown were prepared using the same metals, while white, light blue, blue and green were obtained with different elements. The adoption of different recipes for the same color suggests the presence of several laboratories of ceramists working in Sicily who had preferences for different methods for the production of their enameled artifacts.Concerning the opacifier, the high amounts of lead and antimony, only in a case, indicate the use of lead antimonate (Pb2Sb2O7). Black decorations were present in several of the analyzed samples and in most of them were identified mixtures of black iron and manganese oxides. The green decorations appear to have been prepared with copper oxide; lighter hue samples contained additional amounts of zinc and/or barium compounds. Considering all the samples, meanly, iron predominates in yellow decorations, only a sample contains large amounts of Cd, Zn and very little Sb, which suggests the use of the pigments ZnO (as white) and CdS as cadmium yellow. For all samples, except one, we can exclude the use of pigments containing chromium.

Study on selected trace elements and heavy metals in some popular medicinal plants from Sudan

This study reports on the determination of 11 elements in 33 medicinal plants from Sudan and discusses a possible correlation between their curative effects and their trace elements content. Further, a possible accumulation of adverse heavy metals could be excluded. A total of 11 elements (cadmium, lead, mercury, tin, copper, iron, manganese, zinc, chromium, selenium and magnesium) were determined using inductively coupled plasma (ICP)-optical emission spectrometry (ICP-OES), ICP-sector field-mass spectrometry (ICP-sf-MS) and hydride generation (HG)-ICP-OES techniques. The results of the present study showed no heavy metal accumulation in any of the plants. Cd, Pb, Hg and Sn were found only in trace concentrations significantly below the global limits. This indicates the possibility of a safe use of these medicinal plants. Elevated chromium concentrations were found in those phytopharmaca which are employed for the treatment of diabetes mellitus in Sudanese traditional medicine. Cr was detected in the same range as in other plants reported to be applied for diabetes mellitus treatment. Aside from these medicinal plants, some others were identified which could be potential sources for providing reasonable amounts of Cr, Zn, Mn, Se and Mg for the treatment of diabetes mellitus, smooth muscle relaxation and/or against gastro-intestinal cramps.

Comparative study of heavy metal and trace element accumulation in edible tissues of farmed and wild rainbow trout ( Oncorhynchus mykiss) using ICP-OES technique

The objective of this research was to determine the differences between farmed and wild rainbow trout in terms of heavy metal and trace element accumulation in edible tissues. The samples were analyzed for As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, Sr and Zn by inductively coupled plasma-optical emission spectrometry (ICP-OES); and for Hg by cold vapor atomic absorption spectrometry (CVAAS). The results were expressed as μg/g of dry weight. With the exception of Ba and Sr, liver had significantly higher heavy metal and trace element concentrations compared to the muscle in farmed or wild fish. Higher levels of Ba, Cr, Fe, Mn and Zn, as well as lower levels of Cu and Sr were found in tissues of wild rainbow trout compared to its farmed relative. Levels of Cd in 41.6% of farmed fish samples and 45.8% of wild fish samples exceeded the European Commission regulation. Regarding the Pb, concentrations in 50% of farmed fish samples and 62.5% of wild ones were above the European Commission limit. However, levels of Hg and As in all of the examined samples were lower than the legislated limits. The differences in heavy metal and trace element accumulation observed between farmed and wild fish were probably related to the differences in their environmental conditions and dietary element concentrations.

Determination of Major and Minor Elements in the Malva sylvestris L. from Turkey Using ICP-OES Techniques

In this work, Malva sylvestris var. mauritiana (L.) leaves were collected from different points in Muradiye region of Manisa-Turkey. The leaves were dissolved by wet digestion method using a mixture of mineral acid. Concentrations of Ag, Al, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, La, Mg, Mn, Na, Ni, Pb, Sn, Sr, Sb, Si, Ti, U, Zn, and Zr in prepared solutions were determined by using inductively coupled plasma optical emission spectrometry (ICP-OES). High Ca (13,848 mg/kg) and Mg (1,936 mg/kg) concentrations were found at the leaves. Obtained values were compared with the internationally permitted (standard) values. The results of elements were analyzed statistically (analysis of variance test). For different leaf sizes, concentration factors were calculated.

Comparison of dry, wet and microwave digestion procedures for the determination of chemical elements in wool samples in Turkey using ICP-OES technique

The aim of this study is to quantify the content of elements (Co, Ni, Zn, Cu, Mn, Cd, Pb Cr, Fe, Na, K, Ca, Mg) present in wool samples ( n:87) from Turkey because similar studies have not been published earlier. A fast and simple method for quantification of the metal content of wool samples was standardized for the three sample digestion procedures using dry ashing, wet ashing and microwave digestion and compared by the flame atomic absorption spectrometry (FAAS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). The proposed method indicated satisfactory recovery, detection limits and standard deviation for trace metal determination in wool samples. The results in the samples (minimum–maximum in µg g − 1 ) were: Co 1.22–1.54, Cu 2.45–3.64, Mn 0.44–0.65, Cd 0.08–0.30, Pb 1.33–1.74, Cr 0.33–1.25, Zn 73.94–87.08 and Fe 119.04–182.52.The lowest and highest levels of Na 0.31–0.37, K 0.05–0.06, Ca 0.50–0.66, Mg 0.11–0.12 were found as %. The concentration of Ni was below detection limit. The Certified Reference Material, CRM 397, Human Hair and Tomato Leaves-1573a were used in order to verify the accuracy of the microwave digestion method, and whether the results were in good agreement with the certified values.

Use of fractional factorial design for optimization of digestion procedures followed by multi-element determination of essential and non-essential elements in nuts using ICP-OES technique

Two digestion procedures have been tested on nut samples for application in the determination of essential (Cr, Cu, Fe, Mg, Mn, Zn) and non-essential (Al, Ba, Cd, Pb) elements by inductively coupled plasma-optical emission spectrometry (ICP-OES). These included wet digestions with HNO 3/H 2SO 4 and HNO 3/H 2SO 4/H 2O 2. The later one is recommended for better analytes recoveries (relative error < 11%). Two calibrations (aqueous standard and standard addition) procedures were studied and proved that standard addition was preferable for all analytes. Experimental designs for seven factors (HNO 3, H 2SO 4 and H 2O 2 volumes, digestion time, pre-digestion time, temperature of the hot plate and sample weight) were used for optimization of sample digestion procedures. For this purpose Plackett–Burman fractional factorial design, which involve eight experiments was adopted. The factors HNO 3 and H 2O 2 volume, and the digestion time were found to be the most important parameters. The instrumental conditions were also optimized (using peanut matrix rather than aqueous standard solutions) considering radio-frequency (rf) incident power, nebulizer argon gas flow rate and sample uptake flow rate. The analytical performance, such as limits of detection (LOD < 0.74 μg g −1), precision of the overall procedures (relative standard deviation between 2.0 and 8.2%) and accuracy (relative errors between 0.4 and 11%) were assessed statistically to evaluate the developed analytical procedures. The good agreement between measured and certified values for all analytes (relative error <11%) with respect to IAEA-331 (spinach leaves) and IAEA-359 (cabbage) indicates that the developed analytical method is well suited for further studies on the fate of major elements in nuts and possibly similar matrices.