SRM 1573a Research Articles

Analysing Sr isotopes in low‐Sr samples such as single insects with inductively coupled plasma tandem mass spectrometry using N2O as a reaction gas for in‐line Rb separation

RationaleStrontium isotopes are valuable markers of provenance in a range of disciplines. Limited amounts of Sr in low‐mass samples such as insects mean that conventional Sr isotope analysis precludes their use for geographic origins in many ecological studies or in applications such as biosecurity. Here we test the viability of using inductively coupled plasma tandem mass spectrometry (ICP‐MS/MS) with N2O as a reaction gas for accurately determining Sr isotopes in insects with Sr < 100 ng.MethodsStrontium isotopes were determined in solution mode using ICP‐MS/MS with 0.14 L/min N2O as a reaction gas to convert Sr+ into SrO+ for in‐line separation of 87Sr from 87Rb. The Sr isotope reference standards NIST SRM 987, NIST SRM 1570a and NIST SRM 1547 were used to assess accuracy and reproducibility. Ten insect species collected from the wild as a proof‐of‐principle application were analysed for Sr concentration and Sr isotopes.ResultsUsing ICP‐MS/MS we show for the first time that internal mass bias correction of 87Sr16O/86Sr16O based on 88Sr16O/86Sr16O works to give for NIST SRM 987 a 87Sr/86Sr ratio of 0.7101 ± 0.012 (RSD = 0.17%) and for NIST SRM 1570a a 87Sr/86Sr ratio of 0.7100 ± 0.009 (RSD = 0.12%), which are within error of the accepted values. The first 87Sr/86Sr ratio of NIST SRM 1547 is 0.7596 ± 0.0014. Strontium analyses were run on 0.8 mL of 0.25–0.5 ppb Sr, which equates to 2–4 ng of Sr. Strontium isotope analysis with a precision of >99.8% can be achieved with in‐line separation of 87Sr from 87Rb at least up to solutions with 25 ppb Rb.ConclusionsA minimum of 5 mg of insect tissue is required for Sr isotope analysis. This new ICP‐MS/MS method enables Sr isotope analysis in single insects, allowing population‐scale studies to be feasible and making possible applications with time‐critical uses such as biosecurity.

Investigation on major, minor and trace elements in some medicinal plants using Particle Induced X-ray Emission

Elemental concentrations namely P, S, Cl, K, Ca, Sc, Ti, Mn, Fe, Cu, Zn, Rb, Br and Sr were determined using Particle Induced X-ray Emission method in leaves and flowers of medicinal plants namely flowers of Hibiscus rosa-sinensis, leaves and flowers of Annona reticulata, leaves of holy basil and leaves of Psidium guajava. No toxic elements were detected in these samples. The method was validated by analyzing the reference materials namely IAEA RM V-10 and NIST SRM 1632a. The main objective of this study is to provide a good source of elemental concentration data for Ayurvedic medicine dosage.

Transition Metal Containing Particulate Matter Promotes Th1 and Th17 Inflammatory Response by Monocyte Activation in Organic and Inorganic Compounds Dependent Manner.

In recent years, a significant increase in the frequency of disorders caused by air pollutants has been observed. Here we asked whether transition metal-containing particulate matter (TMCPM), a component of air pollution, has an effect on the activity of human CD4+ T cell subsets (Th1, Th2, Th17, and Treg). Peripheral blood mononuclear cells (PBMC) from healthy donors were cultured with or without NIST (SRM 1648a—standard urban particulate matter purchased from the National Institute for Standards and Technology) and LAP (SRM 1648a particulate matter treated within 120 min with cold oxygen plasma) preparations of TMCPM, differing in organic compounds content. Data show that TMCPM treatment increased the level of CD4+ cells positive for IFN-γ and IL-17A, specific for Th1 and Th17 cells, respectively. Moreover, a substantial decrease in frequency of Foxp3 positive CD4+ cells was observed in parallel. This effect was more pronounced for NIST particles, containing more organic components, including endotoxin (LPS - lipopolysaccharide) and required the presence of monocytes. Inactivation of LPS by treatment of TMCPM with polymyxin B reduced the inflammatory response of monocytes and Th subsets but did not abolish this activity, suggesting a role of their inorganic components. In conclusion, treatment of human PBMC with TMCPM skews the balance of Th1/Th2 and Treg/Th17 cells, promoting polarization of CD4+ T cells into Th1 and Th17 subsets. This phenomenon requires activation of monocytes and depends on the organic and inorganic fractions, including endotoxin content in TMCPM, as significantly higher inflammatory response was observed for the NIST comparing to LAP. This observation may shed a new light on the role of TMCPM in development and exacerbation of allergies, inflammatory, and autoimmune disorders.

Chromium Levels in Tobacco, Filter and Ash of Illicit Brands Cigarettes Marketed in Brazil.

Smoking is a public health problem and an important source of exposure to toxic metals. This work describes an efficient analytical method comparable to the ones based on atomic emission techniques for the determination of chromium in different constituent parts of cigarette samples (tobacco, filters and ashes) using electrothermal vaporization-atomic absorption spectrometry. The method was evaluated using 12 samples, and the results showed recovery values between 83 and 107%. The accuracy was also evaluated using a reference sample of tomato leaves (NIST SRM 1573a), which proved the efficiency of the method. The limits of detection of the developed method were 20.4, 75.8 and 80.7ngg-1 for tobacco, filter and cigarette ash samples, respectively. The average chromium values found for the analyzed samples were in the range of 0.96 to 3.85 and from 0.32 to 0.80μg/cigarette for tobacco and ashes, respectively. For most pre-burn and post-burn filter samples, the values of chromium concentration remained below limits of detection. The developed method presented adequate results about precision and accuracy, demonstrating its applicability in the determination of chromium in cigarette samples.

Elemental analysis of SRM 1547 peach leaves, 1573a tomato leaves, and 1570a spinach leaves

Neutron Activation Analysis Techniques more used in determining macro and microcontent in food ingredients. The quality of the test results is needed to produce a valid analysis. To validate the result of the analysis of macro and micro mineral content in food ingredients, quantitative analysis of the elements in the reference standard is NIST SRM 1547 certified Peach Leaves, NIST SRM 1573a Tomato Leaves, and NIST SRM 1570a Spinach Leaves have been done. The Z-score parameter was used as a validation parameter. Elemental with a long half-life was determined quantitatively using the NAA k0 method. The elements were determined quantitatively through long-lived radioisotopes using the k0 Instrumental Neutron Activation Analysis in the G.A Siwabessy reactor. A number of 50 mg-120 mg samples were weighed and irradiated at the neutron flux of 2.5x1013 n.cm−2.s−1. Irradiation was carried out for 3 hours on the rabbit system while counting with gamma spectrometry was carried out after cooling time of 23 weeks. Quantitative analysis was carried out using a soft K0-IAEA device. The results of quantitative analysis obtained elements of Ca, Fe, Zn, Rb, Sr on SRM NIST 1547 Peach Leaves; elements of Ca, Cr, Fe, Co on NIST SRM 1573a Tomato leaves and elements Ca, Sc, Zn, Rb, Sr, Co on NIST SRM 1570a Spinach Leaves with uncertainty <10% (3.26-8.68%). The Z-score value ranges from-1.25 to 0.69 and the relative bias ranges from 0.1 to 6.28%, so the results of the analysis of these elements are valid for testing elements in food.

Elemental composition analysis in Sangyod rice by instrumental neutron activation analysis

Sangyod Muang Phatthalung Rice is a traditional rice variety grown in the area of Phatthalung province for more than a hundred years. Sangyod rice is the first rice variety of Thailand that has been registered as Geographical Indication (GI). It is also good rice for anyone who is searching for good health. The concentrations of nine elements (Mg, Al, Cl, As, Br, K, Mn, Rb and Zn) in Sangyod rice, locally cultivated in four districts (Pak Phayun, Tamot, Pa Phayom and Muang) in Phatthalung province, were determined using instrumental neutron activation analysis (INAA). The method validation of INAA was verified by SRM 1568a Rice Flour. All elements were found to be in a good agreement with the certified values. The results were analyzed using analysis of variance and Tukey’s HSD test. There were no statistical differences in concentrations of Mg, Al, As, Br, K and Mn in rice from four districts. The concentrations of Cl, Rb and Zn found in rice were significantly different according to the cultivation region. Therefore, Cl, Rb and Zn were good characteristic indicators for Sangyod rice that could be applied to identify the geographical origins of rice.

Preparation and evaluation of a new reference material for macro- and micronutrients in fish feed

A new reference material for inorganic constituents analysis in fish feed was produced and characterized according to the ISO Guides 30-35. The evaluation of the estimated minimum mass, homogeneity, and short- and long-term stability of the material was performed using microwave-assisted digestion and inductively coupled plasma optical emission spectroscopy as an in-house validated technique for Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn analysis. The accuracy of the measurements results was confirmed by analyzing the certified reference materials Oyster Tissue and Tomato Leaves, NIST SRM 1566b and SRM 1573a. The chemical characterization concerning elemental composition was performed through a collaborative trial with the participation of 35 laboratories by using spectroscopic and instrumental neutron activation analysis techniques. One-way analysis of variance (ANOVA) and regression analysis were the statistical methods applied to achieve the consensus values and their combined uncertainty, and the homogeneity and stability of the material presented averages within the 95% confidence interval. The expanded uncertainty considered all the instability observed during the stability, homogeneity, and characterization tests. The certified values and expanded uncertainties (k = 2) for the candidate reference were (28.65 ± 1.84) g kg−1 Ca, (10.51 ± 0.87) mg kg−1 Cu, (231.97 ± 20.17) mg kg−1 Fe, (5.86 ± 0.31) mg kg−1 K, (1.55 ± 0.16) g kg−1 Mg, (19.46 ± 2.12) mg kg−1 Mn, (2.16 ± 0.19) g kg−1 Na, (16.06 ± 0.97) g kg−1 P, and (129.56 ± 6.79) mg kg−1 Zn. The produced material proved its suitability for internal instrumental quality control or for the quality assurance of Ca, Cu, Fe, Mg, Mn, Na, P, and Zn analysis in fish feed for evaluation the laboratories quality control.

Integrative analysis of mRNAs, miRNAs and lncRNAs in urban particulate matter SRM 1648a-treated EA.hy926 human endothelial cells

Considering the unique physiochemical properties of concentrated ambient particles (CAPs), it is extremely important to be aware of their toxic effect. A number of studies have investigated the vascular toxicity of CAPs, while potential mechanisms are still not clearly defined. Differentially expressed mRNAs, miRNAs and lncRNAs were analyzed in EA.hy926 endothelial cells after incubation with 2.5 and 10 μg/cm2 urban particulate matter SRM 1648a for 24 h. As a result, the microarray profile showed that 97 mRNA, 18 miRNA, and 356 lncRNA transcripts are dysregulated in 2.5 μg/cm2 group. And the expression of 440 mRNAs, 40 miRNAs, and 1283 lncRNAs significantly changes in 10 μg/cm2 group. Through the miRNA-mRNA-transcription factor (TF) network, hsa-miR-128-3p, miR-18-5p and miR-376a-3p, miR-4306 as well, are key miRNAs in SRM 1648a-induced endothelial damage. Withal, lncRNA-mRNA-TF analysis hinted the importance of lncRNA T018951 and T200627. Subsequently, competing endogenous RNA (CeRNA) network was constructed for the comprehensive analysis of the regulation dogma between mRNAs and non-coding RNAs. It suggested that 35 GO terms and 1 KEGG pathway are significantly enriched in 2.5 μg/cm2 group. Meanwhile, 185 terms and 18 pathways are important in 10 μg/cm2 group. Pathway analysis revealed that Gap junction, Ras and MAPK signaling pathways are most significant in endothelial cell lesion. In conclusion, integrative analysis of mRNA and non-coding RNA in human endothelial cells suggests that a vast majority of non-coding RNAs regulate vascular toxicity in response to SRM 1648a. Moreover, it highlights the need for comprehensive analysis of latent mechanisms through a combination of signaling pathways with epigenetics studies.

Tissue level distribution of toxic and essential elements during the germination stage of corn seeds (Zea mays, L.) using LA-ICP-MS

Both essential and toxic metal contaminants impact agricultural crops by bioaccumulation in plants. The goal of this study was to evaluate the tissue-level spatial distribution of metal(loids) in corn seeds (Zea mays, L.) from contaminated corn fields near the Xikuangshan (XKS) antimony mine in Hunan, China, and compared them with corn (Zea mays everta L., popcorn) grown in a farm in Amherst, MA that practices sustainable farming as a control. How toxic and essential metals translocate through the roots and shoots during early stages of germination was also investigated. The cleaned corn seed samples were mounted in resin blocks and longitudinally dissected into thin sections. The laser ablation parameters were optimized, and the instrument was calibrated using tomato leaf standard reference material (NIST SRM 1573a) in a pellet form. Tissue level distributions of metal(loid)s As, Cd, Hg, Sb and Zn in corn seeds collected were determined using (LA-ICP-MS). Seeds from the control farm were germinated and their roots and shoots were analyzed to determine tissue level concentrations and their spatial distributions. It was found that seeds from the XKS mine region in China had higher overall concentration of all elements analyzed due to metal(loids) absorbed from contaminated mine soils. Metal(loids) concentrations were highest in the embryo (∼360 mg/kg) and pericarp (∼0.48 mg/kg) compared with the endosperm of corn seeds. Essential element Zn was found in the embryo and emerging coleoptile and radicle. Finally, in both roots and shoots, element concentrations were highest proximally to the tip cap compared to distal concentrations and later translocated to distal tissue regions. This study offers unique insights of metal(loid) bioaccumulation and translocation in corn and thus is better able to track metal(loids) contaminants trafficking in our food systems.

Particulate matter induces pro-inflammatory cytokines via phosphorylation of p38 MAPK possibly leading to dermal inflammaging.

Particulate matter (PM) is known to have harmful effects on human health. Epidemiological studies have suggested that PM exposure is related to skin diseases and extrinsic skin ageing. However, the mechanisms by which PM affects skin are unclear. The aim of this study was to investigate the mechanism of action of PMs on epidermal inflammation and skin ageing using a co-culture of human keratinocytes (HaCaT) and fibroblasts (HDF). SRM 1648a (pmA) and 1649b (pmB), which mainly comprise heavy metals and polycyclic aromatic hydrocarbons, respectively, were used as reference PMs. Cytotoxic effects, activation of AhR, phosphorylation of p38 kinase and ROS generation were examined in PM-treated HaCaT cells. The phosphorylation of p38 MAPK induced by PMs was shown to be critically important for the increases in IL-1α and IL-1β expression. Moreover, the mRNA and protein expression levels of MMP1 and COX2 were markedly increased in HDF cells co-cultured with PM-treated HaCaT cells. In conclusion, PMs induce the expression of pro-inflammatory cytokines in keratinocytes via the p38 MAPK pathway, and these interleukins increase the expression of MMP1 and COX2 in HDF cells. These results suggest that PMs trigger skin ageing via p38 MAPK activation and interleukin secretion in epidermal keratinocytes.

Application of an Isotope Binary Mixing Model for Determination of Precise Mercury Isotopic Composition in Samples with Low Mercury Concentration.

An isotope binary mixing model was applied for high precision measurement of mercury isotope ratios in samples with low mercury concentrations by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). Standard addition was used to evaluate the precision and accuracy of the isotope composition calculations resulting from the isotope binary mixing model. A high, steady 202Hg signal of approximately 2.13 V was achieved, with the mercury concentration reaching 3 ng/mL. The isotopic composition of three standards (NIST SRM 1646a; NIST SRM 1575a; BCR 482) and natural samples were precisely determined. The standards and natural samples were diluted to low mercury concentrations (low to 0.90 ng/mL) and mixed with standard solutions (NIST SRM 3133) with high mercury concentrations (50 ng/mL); the isotopic compositions of low mercury concentration samples were calculated using an isotope binary mixing model after the isotopic compositions of the mixing solutions were measured. The results showed that the uncertainty of the calculated mercury isotopic compositions was in an acceptable range and the calculation isotope data were in good agreement with direct measurements. Our method allows the precise determination of mercury isotope composition in mercury solutions of concentrations (0.90 ng/mL) below the detection limit of the current system (3.00 ng/mL).

Assessment of Gluten-Free Food Sourced Heavy Metal Accumulation for Celiac People

This paper shows an evaluation to the study of some heavy metals in certain gluten-free foods for celiac people marketed in Kayseri, Turkey. The concentration values of Cu, Mn, Co, Pb, Cr, Zn, Ni, Cd and Fe in eleven different gluten-free food samples are reported. The determinations were carried out by flame atomic absorption spectrometry after wet digestion method. The average metal concentrations of all the analyzed samples were determined in the range of 0.45-5.12, 1.84-12.2, 1.29-22.5, 0.60-3.01, 0.08-0.18, and 4.61-79.6 mg kg-1 for Cu, Mn, Zn, Ni, Cd and Fe, respectively. The accuracy of the method was confirmed by the analysis of a standard reference material (SRM 1570a Spinach Leaves). Metal pollution index was also calculated to examine the overall heavy metal levels in all analyzed samples. The concentrations of the analyzed metals are equivalent to 7.55-35.3% compared to the daily intake offered by international decision authorities. For this reason, the nutritional quality index for gluten-free food products with respect to all the metals seems to be relatively low.

Colorimetric and visual determination of ultratrace uranium concentrations based on the aggregation of amidoxime functionalized gold nanoparticles.

The authors describe the synthesis and characterization of 3-mercaptopropionylamidoxime functionalized gold nanoparticles (AuNPs) for visual detection of uranium (U) by cloud point extraction. The method is capable of quantifying U at the concentration limits set by the World Health Organization in drinking water i.e., 30.0ngmL-1. The method is based on the gradualcolor change from red to blue that occurs as a result of the interaction between uranyl ion and the modified AuNPs leading to particle aggregation. Such analyte-triggered aggregation results in AuNP's peak absorbance quenching as well as red shift in the wavelength range of 520 to 543nm. The colorimetric response at 520nm is linear in the 2-100ngmL-1U concentration range, and the limit of detection is 0.3ngmL-1. No interferences by other ions are found, and the relative standard deviation is ≤4% (for n = 5). The method is validated by analyzing a certified reference material (NIST SRM 1640a; natural water), and also applied to the quantification of U in four (spiked) water samples. Graphical abstract Schematic presentation of cloud point extraction (CPE) assisted coloirmetric and visual detection of uranium (U). In CPE of gold nanoparticles (AuNPs) the color of surfactant rich phase (SRP) turns red in absence of U(VI) and blue in presence of U(VI).

Multi-wavelength calibration: Determination of trace toxic elements in medicine plants by ICP OES

In the present work a promising method for elemental impurities quantification, such as As, Cd, Cr, Cu, Ni and Pb in medicinal plants, called Multi-Wavelength Calibration - MWC, is shown. Calibration and quantification are performed with only two solutions. The first solution contains sample and a standard solution of known concentration of each analyte (1:1 v−1), and the second solution contains sample and a blank sample solution (1:1 v−1). The method was validated using addition and recovery tests, and content quantification of each analyte in SRM 1570a and SRM 1575a. The recoveries obtained were between 96.90–99.90% and relative standard deviation of 1.40%. The results obtained in the quantification of SRMs demonstrate excellent method accuracy. The levels of elemental impurities present in medicinal plants had concentrations above that allowed for As, Cr, Cu, Ni and Pb, and higher concentrations for arsenic, when compared to the maximum limits allowed by the Brazilian Pharmaceutical, World Health Organization, National Sanitation Foundation International and European Medicines Agency. The results demonstrated that the MWC is a fast, accurate and highly sensitive alternative to the methods used by the main regulatory agencies to determine elemental impurities in medicinal and phytotherapeutic plants.

Graphene oxide chemically modified with 5-amino-1,10-phenanthroline as sorbent for separation and preconcentration of trace amount of lead(II).

Graphene oxide (GO) was chemically functionalized with 5-amino-1,10-phenanthroline. The resulting conjugate (phen-GO) was characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. The experiments show that phen-GO has a high affinity for extraction of Pb(II) ions. Isotherms and kinetics fit the Langmuir model and pseudo-second-order equations. By using phen-GO as a sorbent, Pb(II) ions can be quantitatively adsorbed at pH6.0. The adsorption capacity is 548mgg-1. Following desorption with 2molL-1 HNO3, Pb(II) was quantified by inductively coupled plasma optical emission spectrometry. The effects of pH value, eluent type, sorption time, sample volume, and matrix ions were optimized. The accuracy of the method was validated by analysis of the reference materials DOLT-3 (dogfish liver) and SRM 1640a (natural water). Under optimal conditions, the calibration plots cover the 0.25 to 500ngmL-1 Pb(II) concentration range. The method was successfully applied to the analysis of spiked water and biological samples. Other figures of merit include a preconcentration factor of 250, a detection limit of 46ngL-1, and a relative standard deviation of <5%. Graphical abstract Schematic presentation of the dispersive solid-phase extraction of lead(II) ions using graphene oxide modified with 5-amino-1,10-phenanthroline, followed by their determination by inductively coupled plasma optical emission spectrometry (ICP OES).

Determination of toxic organic pollutants in fine particulate matter using selective pressurized liquid extraction and gas chromatography–tandem mass spectrometry

Studies investigating toxic organic pollutants in fine dust (PM2.5), such as polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), are insufficient, despite the pollutants’ potent toxicity. The objective of this study is to develop an analytical method for determining PAHs, OCPs and PCBs in ambient PM2.5 using selective pressurized liquid extraction (SPLE). To maximize the extraction efficiency of target analytes, the extraction parameters of SPLE, particularly solvent type, temperature, static time, and cycle number, were optimized. The highest recoveries were observed under the conditions of dichloromethane:acetone (9:1), 100℃, 5 min of static time, and 1 cycle extraction, which is selected as the optimal method of SPLE. In the method validation, the results showed that the suggested method can quantify 17 PAHs, 20 OCPs, and 63 PCBs in PM2.5. Using urban dust SRM (1648a) and ambient PM2.5 samples, the applicability of the method was also confirmed. Total concentration of PAHs was the highest (2639.42–7377.75 pg/m3) followed by OCPs (80.57–674.69 pg/m3) and PCBs (1.39–9.34 pg/m3). Most of the PAHs were detected, whereas 2–7 compounds among 20 OCPs and 2–6 compounds among 63 PCBs were determined. The developed analytical method is highly efficient in terms of process (a one-step extraction process), time (15 min extraction time per one sample) and solvent usage (less than 30 mL per one sample), showing good performance. This method can be applied to investigate the organic toxicants in PM2.5, and it can contribute to monitoring and risk assessment, leading to an effective risk management policy for PM2.5 in Korea.

Urban Particulate Matter-Induced Decomposition of S-Nitrosoglutathione Relevant to Aberrant Nitric Oxide Biological Signaling.

Exposure to airborne particulate matter (PM) is associated with hazardous effects on human health. Soluble constituents of PM may be released in biological fluids and disturb the precisely tuned nitric oxide signaling processes. The influence of aqueous extracts from two types of airborne urban PM (SRM 1648a, a commercially available sample, and KR PM2.5, a sample collected "in-house" in Krakow, Poland) on the stability of S-nitrosoglutathione (GSNO) was investigated. The particle interfaces had no direct effect on the studied reaction, but extracts obtained from both samples facilitated NO release from GSNO. The effectiveness of NO release was significantly affected by glutathione (GSH) and ascorbic acid (AscA). Examination of the combined influence of Cu2+ , Fe3+ , and reductants on GSNO stability revealed copper to be the main GSNO decomposing species. Computational models of nitrosothiols interacting with metal oxide substrates and solvated metal ions support these claims. The study stresses the importance of the interplay between metal ions and biological reductants in S-nitrosothiols decomposition.

Assessment of ultrasound-assisted extraction combined with supramolecular solvent-based microextraction for highly sensitive cadmium determination in medicinal plant sample by TS-FF-AAS

A new analytical method exploiting supramolecular solvent-based microextraction (SUPRAS) combined with ultrasound-assisted extraction to preconcentrate cadmium from medicinal plant, with further determination by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS), is proposed. The proposed method is based on the cadmium ultrasound-assisted extraction from Ginkgo biloba L. leaf samples with diluted acid (0.10 mol L−1 HNO3), followed by the metal complexation with diethyl dithiophosphate and preconcentration using a supramolecular solvent composed of inverted hexagonal aggregates of dodecanoic acid arranged in tetrahydrofuran/water medium. The limits of detection (LOD) and quantification (LOQ) were found to be 0.11 μg L−1 and 0.36 μg L−1, respectively. Intraday and interday precision assessed in terms of relative standard deviations (RSD, %) were lower than 8.50% to 0.70, 1.75 and 5.00 μg L−1 cadmium solutions. The efficiency of ultrasound-assisted extraction was comparable to microwave-assisted digestion and the method accuracy was checked by analysis of certified reference material (Tomato Leaves, SRM 1573a). Samples of Ginkgo biloba L. were analyzed and cadmium contents between 0.21 and 0.33 μg g−1 were found, thereby showing clearly the importance of investigating toxic metals in medicinal plants. The proposed method is simple, highly sensitive, environmentally friendly and has great potential to be applied in the quality control of medicinal plants aiming trace cadmium determination.

Comparison of the sorption capacities of 1,10-phenanthroline and 2,2-bipyridyl complexes with cadmium on activated carbon and graphene oxide

In this study adsorption potential of oxidation activated carbon (ox-AC) and graphene oxide (GO) was investigated. Cd(II) was bound to cationic complexes with 1,10-phenanthroline or 2,2-bipyridyl. The sorbents have been used for the dispersive solid-phase extraction of Cd(II) prior to its inductively coupled plasma optical emission spectrometric or electrothermal atomic absorption spectrometric determination. The influences of the various analytical parameters including pH, eluent type, ligand amount, sample volume and sorption time on the recovery efficiencies of Cd(II) were investigated. The limit of detection for activated carbon - 1,10-phenanthroline and activated carbon - 2,2-bipyridyl were 0.006 and 0.016 ng mL−1, respectively. For graphene oxide with 1,10-phenanthroline and graphene oxide with 2,2-bipyridyl obtained limit of detection were 0.046 and 0.091 ng mL−1, respectively. Maximum adsorption capacities and preconcentration factors were compared. The equilibrium sorption fitted better to the Langmuir isotherm. The method was validated with the certified reference materials ERM-BB186 and SRM 1640a.

Determination of Selenium in Food Samples by High-Resolution Continuum Source Atomic Absorption Spectrometry After Preconcentration on Halloysite Nanotubes Using Ultrasound-Assisted Dispersive Micro Solid-Phase Extraction

In this study, a preconcentration procedure was developed for the determination of selenium in food samples using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS). Halloysite nanotubes (HNTs) were used as a solid sorbent in ultrasound-assisted dispersive micro solid-phase extraction (USA DMSPE) during the preconcentration step. The experimental parameters including pH of the sample solution, the amount of halloysite nanotubes, and ultrasonication time, as well as the main parameters of HR-CS GFAAS, were optimized. The limit of detection of total selenium was 0.01 μg/L and the achieved preconcentration factor was 18. The relative standard deviations (RSDs) were 6–9%. The accuracy of this method was validated by analyses of NIST SRM 1567a (wheat flour) and NIST SRM 1549 (non-fat milk powder) certified reference materials. Selenium contents measured in these reference materials were in satisfactory agreement with the certified values according to the t test for a 95% confidence level. The proposed method was successfully applied to the determination of selenium in food samples (corn flour, rice flour, oat flour, buckwheat flour, garlic, cranberries, goji berries, and raisins).