Study of essential element accumulation in the leaves of a Cu-tolerant plant Elsholtzia splendens after Cu treatment by imaging laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for the quantitative imaging of Cu and other essential elements (such as K, Mg, Mn, P, S and B) in the leaves of a Cu-tolerant plant Elsholtzia splendens treated with the enriched ⁶⁵Cu isotope tracer (isotope abundance of 89.2%). The leaves (newly formed, fully grown and oldest) were scanned directly with a focused Nd:YAG laser in the laser ablation chamber. The ablated material was transported with argon as carrier gas to a quadrupole-based ICP-MS (ICP-QMS), and the ion intensities of ⁶⁵Cu⁺, ³⁹K⁺, ²⁴Mg⁺, ⁵⁵Mn⁺, ³¹P⁺, ³⁴S⁺ and ¹¹B⁺ were measured by ICP-QMS to study the accumulation of Cu and other elements of interest. Standard reference material NIST SRM 1515 Apple Leaves doped with known concentrations of analytes (from 0.1 to 2000 mg L⁻¹) was measured together with the samples by LA-ICP-MS and was used for the quantification of the analytical data. Notable accumulation of Cu in the newly formed leaves was clearly identified by imaging LA-ICP-MS. The increased isotope ratios of ⁶⁵Cu/⁶³Cu measured by LA-ICP-MS demonstrated the path of Cu uptake and accumulation via the petiole and main veins in the leaves. Cu stress-induced accumulation of K, Mg, Mn, P and S in the newly formed leaves was observed, while B was not significantly affected. In the present study, the concentrations of K, Mg, Mn, P and S were not obviously changed in the fully grown leaves after short-term treatment. Along with the treatment, a visible decrease of K and P was found in the oldest leaves, while other elements were not influenced by Cu stress.     

Defence response of Sitka spruce before and after inoculation with Heterobasidion annosum: 1H NMR fingerprinting of bark and sapwood metabolites

Metabolite fingerprinting of Sitka spruce (Picea sitchensis) bark and sapwood was carried out by ¹H nuclear magnetic resonance after wounding and artificial inoculation with the white rot fungus Heterobasidion annosum sensu stricto. The aim was to determine whether metabolites would differ in clones showing differing levels of susceptibility to H. annosum, in the fungal as compared with the control treatment (wounding, no fungus) and the reference (healthy sample collected at 0 days), at two different locations on the host, and at different sampling times (3 and 43 days after treatment). The results suggested that different metabolic processes occur in bark and sapwood after wounding and fungal inoculation, compared with healthy samples collected before treatment: In bark, greater peaks were elicited in the aromatic region whereas, in sapwood, lower amounts of all metabolites were observed in inoculated samples, compared with healthy samples. Multivariate statistical analysis carried out with analysis of variance–principal component analysis showed highly significant effects of reference, location, and time (PC1), and significant effects of clone and fungus. Differences between clones were apparent in sapwood but not in bark and were due to peaks in the aliphatic and carbohydrate regions. Over time, in bark, there was a decrease in carbohydrate peaks, followed by an increase in aliphatic and aromatic peaks. Sapwood, by contrast, showed a decrease in all peaks, followed by an increase in carbohydrate and aliphatic peaks. Changes in carbohydrate levels were observed within the lesion compared with the more distal location in both bark and sapwood.     

Imaging of nutrient elements in the leaves of Elsholtzia splendens by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for the quantitative imaging of nutrient elements (such as K, Mg, Mn, Cu, P, S and B) in the leaves of Elsholtzia splendens. The plant leaves were scanned directly with a focused Nd:YAG laser in the laser ablation chamber. The ablated material was transported with argon as carrier gas to a quadrupole-based ICP-MS (ICP-QMS), and the ion intensities of ³⁹K⁺, ²⁴Mg⁺, ⁵⁵Mn⁺, ⁶³Cu⁺, ³¹P⁺, ³⁴S⁺ and ¹¹B⁺ were measured by ICP-QMS to study the distribution of the elements of interest. The imaging technique using LA-ICP-MS on plant leaves does not require any sample preparation. Carbon (¹³C⁺) was used as an internal standard element to compensate for the difference in the amount of material ablated. Additional experiments were performed in order to study the influence of the water content of the analyzed leaves on the intensity signal of the analyte. For quantification purposes, standard reference material (NIST SRM 1515 Apple Leaves) was selected and doped with standard solutions of the analytes within the concentration range of 0.1-2000 mg L⁻¹. The synthetic laboratory standards together with the samples were measured by LA-ICP-MS. The shape and structure of the leaves was clearly given by LA-ICP-MS imaging of all the elements measured. The elemental distribution varied according to the element, but with a high content in the veins for all the elements investigated. Specifically, Cu was located uniformly in the mesophyll with a slightly higher concentration in the main vein. High ion intensity was measured for S with a high amount of this element in the veins similar to the images of the metals, whereas most of the B was detected at the tip of the leaf. With synthetic laboratory standard calibration, the concentrations of elements in the leaves measured by LA-ICP-MS were between 20 μg g⁻¹ for Cu and 14,000 μg g⁻¹ for K.     

Comparative imaging of P,S, Fe,Cu, Zn and C in thin sections of rat brain tumor as well as control tissues by laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for quantitative imaging of selected elements (P, S, Fe, Cu, Zn and C) in thin sections of rat brain samples (thickness 20 μm). The sample surface was scanned (raster area ~ 2 cm²) with a focused laser beam (wavelength 266 nm, diameter of laser crater 50 μm, and irradiance 1 × 10⁹ W cm^− 2). The laser ablation system was coupled to a double-focusing sector field. The possibility was evaluated of using carbon (via measurement of ¹³C⁺) as an internal standard element for imaging element distribution as part of this method. The LA-ICP-MS images obtained for P, S, Fe Cu and Zn were quantified using synthetically prepared matrix-matched laboratory standards. Depending on the sample analyzed, concentrations of Cu and Zn in the control tissue were found to be in the range of 8–10 μg g^− 1 and 10–12 μg g^− 1, while in the tumor tissue these concentrations were in the range of 12–15 μg g^− 1 and 15–17 μg g^− 1, respectively. The measurements of P, S and Fe distribution revealed the depletion of these elements in tumor tissue. In all the samples, the shape of the tumor could be clearly distinguished from the surrounding healthy tissue by the depletion in carbon. Additional experiments were performed in order to study the influence of the water content of the analyzed tissue on the intensity signal of the analyte. The results of these measurements show the linear correlation (R² = 0.9604) between the intensity of analyte and amount of water in the sample. The growth of a brain tumor was thus studied for the first time by imaging mass spectrometry.     

Laser ablation inductively coupled plasma mass spectrometry for imaging of copper, zinc, and platinum in thin sections of a kidney from a mouse treated with cis-platin

Platinum complexes are used for the treatment of several types of cancer. High platinum concentrations in the target tissue and low concentrations in dose-limiting tissue structures such as renal tubules are desirable to assure selective toxicity. Microlocal analysis of platinum distribution in tissue sections may thus contribute to the optimization of platinum therapy. Scanning laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to produce images of element distribution in 14-μm thin sections of kidney tissue from a mouse treated with cis-platin 60 min prior to victimization. The sample surface was scanned (raster area 300 mm²) with a focused laser beam (wavelength 266 nm, diameter of laser crater 50 μm, inter line distance 50 μm and laser power density 3 × 10⁹ W cm⁻²) in a cooled laser ablation chamber (about −15 °C) developed for these measurements. The laser ablation system was coupled to a double-focusing sector field ICP-MS. Ion intensities of ⁶³Cu⁺, ⁶⁴Zn⁺, and ¹⁹⁶Pt⁺ were measured within the tissue by LA-ICP-MS. Matrix-matched laboratory standards served for calibration of analytical data. The mass spectrometric analysis yielded an inhomogeneous distribution for Cu, Zn, and Pt in thin kidney sections. Copper was enriched in the capsule and outer cortex, zinc in the inner cortex and the platinum concentration followed a centripetal gradient with clear medullar enrichment. Thus, scanning LA-ICP-MS may be a useful tool in the preclinical development of new and less nephrotoxic platinum complexes.     

External calibration strategy for trace element quantification in botanical samples by LA-ICP-MS using filter paper

The use of reference solutions dispersed on filter paper discs is proposed for the first time as an external calibration strategy for matrix matching and determination of As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, V and Zn in plants by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). The procedure is based on the use of filter paper discs as support for aqueous reference solutions, which are further evaporated, resulting in solid standards with concentrations up to 250 μg g⁻¹ of each element. The use of filter paper for calibration is proposed as matrix matched standards due to the similarities of this material with botanical samples, regarding to carbon concentration and its distribution through both matrices. These characteristics allowed the use of ¹³C as internal standard (IS) during the analysis by LA-ICP-MS. In this way, parameters as analyte signal normalization with ¹³C, carrier gas flow rate, laser energy, spot size, and calibration range were monitored. The calibration procedure using solution deposition on filter paper discs resulted in precision improvement when ¹³C was used as IS. The method precision was calculated by the analysis of a certified reference material (CRM) of botanical matrix, considering the RSD obtained for 5 line scans and was lower than 20%. Accuracy of LA-ICP-MS determinations were evaluated by analysis of four CRM pellets of botanical composition, as well as by comparison with results obtained by ICP-MS using solution nebulization after microwave assisted digestion. Plant samples of unknown elemental composition were analyzed by the proposed LA method and good agreement were obtained with results of solution analysis. Limits of detection (LOD) established for LA-ICP-MS were obtained by the ablation of 10 lines on the filter paper disc containing 40 μL of 5% HNO₃ (v v⁻¹) as calibration blank. Values ranged from 0.05 to 0.81  μg g⁻¹. Overall, the use of filter paper as support for dried aqueous standards showed to be a useful strategy for calibration and plant analysis by LA-ICP-MS.     

Quantitative images of metals in plant tissues measured by laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for quantitative imaging of toxic and essential elements in thin sections (thickness of 30 or 40 μm) of tobacco plant tissues. Two-dimensional images of Mg, Fe, Mn, Zn, Cu, Cd, Rh, Pt and Pb in leaves, shoots and roots of tobacco were produced. Sections of the plant tissues (fixed onto glass slides) were scanned by a focused beam of a Nd:YAG laser in a laser ablation chamber. The ablated material was transported with argon as carrier gas to the ICP ion source at a quadrupole ICP-MS instrument. Ion intensities of the investigated elements were measured together with ¹³C⁺, ³³S⁺ and ³⁴S⁺ within the entire plant tissue section. Matrix matching standards (prepared using powder of dried tobacco leaves) were used to constitute calibration curves, whereas the regression coefficient of the attained calibration curves was typically 0.99. The variability of LA-ICP-MS process, sample heterogeneity and water content in the sample were corrected by using ¹³C⁺ as internal standard. Quantitative imaging of the selected elements revealed their inhomogeneous distribution in leaves, shoots and roots.     

Biomonitoring of essential and toxic metals in single hair using on-line solution-based calibration in laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been established as a powerful and sensitive surface analytical technique for the determination of concentration and distribution of trace metals within biological systems at micrometer spatial resolution. LA-ICP-MS allows easy quantification procedures if suitable standard references materials (SRM) are available. In this work a new SRM-free approach of solution-based calibration method in LA-ICP-MS for element quantification in hair is described. A dual argon flow of the carrier gas and nebulizer gas is used. A dry aerosol produced by laser ablation (LA) of biological sample and a desolvated aerosol generated by pneumatic nebulization (PN) of standard solutions are carried by two different flows of argon as carrier or nebulizer gas, respectively and introduced separately in the injector tube of a special ICP torch, through two separated apertures. Both argon flows are mixed directly in the ICP torch. External calibration via defined standard solutions before analysis of single hair was employed as calibration strategy. A correction factor, calculated using hair with known analyte concentration (measured by ICP-MS), is applied to correct the different elemental sensitivities of ICP-MS and LA-ICP-MS. Calibration curves are obtained by plotting the ratio of analyte ion M⁺/³⁴S⁺ ion intensities measured using LA-ICP-MS in dependence of analyte concentration in calibration solutions. Matrix-matched on-line calibration in LA-ICP-MS is carried out by ablating of human hair strands (mounted on a sticky tape in the LA chamber) using a focused laser beam in parallel with conventional nebulization of calibration solutions. Calibrations curves of Li, Na, Mg, Al, K, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, Sr, Mo, Ag, Cd, I, Hg, Pb, Tl, Bi and U are presented. The linear correlation coefficients (R) of calibration curves for analytes were typically between 0.97 and 0.999. The limits of detection (LODs) of Li, V, Mn, Ni, Co, Cu, Sr, Mo, Ag, Ba, Cd, I, Hg, Pb, Bi and U in a single hair strand were in the range of 0.001-0.90 μg g⁻¹, whereas those of Cr and Zn were 3.4 and 5.1 μg g⁻¹, respectively. The proposed quantification strategy using on-line solution-based calibration in LA-ICP-MS was applied for biomonitoring (the spatial resolved distribution analysis) of essential and toxic metals and iodine in human hair and mouse hair.     

Development and Evaluation of Fiber Optic Probe-based Helium–Neon Low-level Laser Therapy System for Tissue Regeneration—An In Vivo Experimental Study

We report the design and development of an optical fiber probe-based Helium–Neon (He–Ne) low-level laser therapy system for tissue regeneration. Full thickness excision wounds on Swiss albino mice of diameter 15 mm were exposed to various laser doses of 1, 2, 3, 4, 6, 8 and 10 J cm⁻² of the system with appropriate controls, and 2 J cm⁻² showing optimum healing was selected. The treatment schedule for applying the selected laser dose was also standardized by irradiating the wounds at different postwounding times (0, 24 and 48 h). The tissue regeneration potential was evaluated by monitoring the progression of wound contraction and mean wound healing time along with the hydroxyproline and glucosamine estimation on wound ground tissues. The wounds exposed to 2 J cm⁻² immediately after wounding showed considerable contraction on days 5, 9, 12, 14, 16 and 19 of postirradiation compared with the controls and other treatment schedules, showing significant (P < 0.001) decrease in the healing time. A significant increase in hydroxyproline and glucosamine levels was observed for the 2 J cm⁻² irradiation group compared with the controls and other treatment groups. In conclusion, the wounds treated with 2 J cm⁻² immediately after the wounding show better healing compared with the controls.     

Application of dried-droplets deposited on pre-cut filter paper disks for quantitative LA-ICP-MS imaging of biologically relevant minor and trace elements in tissue samples

In this work, a novel calibration approach for minor and trace element quantification in LA-ICP-MS imaging of biological tissues is presented. Droplets of aqueous standard solutions are deposited onto pre-cut pieces of filter paper, allowed to dry, and sputtered with a thin gold layer for use as pseudo-internal standard. Analysis of the standards using LA-ICP-MS is performed using radial line-scans across the filters. In contrast to conventionally used preparation of matrix-matched tissue standards, the dried-droplet approach offers a variety of advantages: The standards are easy to prepare, no characterization of the standards using acid digestion is required, no handling of biological materials is necessary, and the concentration range, as well the number of investigated analytes is almost unlimited. The proposed quantification method has been verified using homogenized tissue standards with known analyte concentrations before being applied to a human malignant mesothelioma biopsy from a patient who had not received any chemotherapeutic treatment. Elemental distribution images were acquired at a lateral resolution of 40 μm per pixel, limits of detection ranging from 0.1 μg g⁻¹ (Mn, Ni, Cu, Zn) to 13.2 μg g⁻¹ (K) were reached.     

Stark broadening of Mg I and Mg II spectral lines and Debye shielding effect in laser induced plasma

We report Stark broadening parameters for three Mg I lines and one Mg II line in the electron number density range (0.67–1.09) · 10¹⁷ cm^− 3 and electron temperature interval (6200–6500) K. The electron density is determined from the half width of hydrogen impurity line, the H_α, while the electron temperature is measured from relative intensities of Mg I or Al II lines using Boltzmann plot technique. The plasma source was induced by Nd:YAG laser radiation at 1.06 μm having pulse width 15 ns and pulse energy 50 mJ. Laser induced plasma is generated in front of a solid state surface. High speed photography is used to determine time of plasma decay with good homogeneity and then applied line self-absorption test and Abel inversion procedure. The details of data acquisition and data processing are described and illustrated with typical examples. The experimental results are compared with two sets of semiclassical calculations and the results of this comparison for Mg I lines are not unambiguous while for Mg II 448.1 nm line, the results of Dimitrijević and Sahal-Bréchot calculations agree well with our and other experimental results in the temperature range (5000–12,000) K and these theoretical results are recommended for plasma diagnostic purposes. The study of line shapes within Mg I 383.53 nm multiplet shows that the use of Debye shielding correction improves the agreement between theoretical and experimental Stark broadening parameters.     

High-resolution laser ablation inductively coupled plasma mass spectrometry used to study transport of metallic nanoparticles through collagen-rich microstructures in fibroblast multicellular spheroids

We have efficiently produced collagen-rich microstructures in fibroblast multicellular spheroids (MCSs) as a three-dimensional in vitro tissue analog to investigate silver (Ag) nanoparticle (NP) penetration. The MCS production was examined by changing the seeding cell number (500 to 40,000 cells) and the growth period (1 to 10 days). MCSs were incubated with Ag NP suspensions with a concentration of 5 μg mL⁻¹ for 24 h. For this study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to visualize Ag NP localization quantitatively. Thin sections of MCSs were analyzed by LA-ICP-MS with a laser spot size of 8 μm to image distributions of ¹⁰⁹Ag, ³¹P, ⁶³Cu, ⁶⁶Zn, and ⁷⁹Br. A calibration using a NP suspension was applied to convert the measured Ag intensity into the number of NPs present. The determined numbers of NPs ranged from 30 to 7200 particles in an outer rim of MCS. The particle distribution was clearly correlated with the presence of ³¹P and ⁶⁶Zn and was localized in the outer rim of proliferating cells with a width that was equal to about twice the diameter of single cells. Moreover, abundant collagens were found in the outer rim of MCSs. For only the highest seeding cell number, NPs were completely captured at the outer rim, in a natural barrier reducing particle transport, whereas Eosin (⁷⁹Br) used as a probe of small molecules penetrated into the core of MCSs already after 1 min of exposure.

Fibroblast MCS could build up the barrier only for nanoparticles

     

Laser ablation inductively coupled plasma mass spectrometry for direct analysis of the spatial distribution of trace elements in metallurgical-grade silicon

The spatial distribution and concentration of impurities in metallurgical-grade silicon (MG-Si) samples (97–99% w/w Si) were investigated by use of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The spatial resolution (120 μm) and low limits of detection (mg kg⁻¹) for quality assurance of such materials were studied in detail. The volume-dependent precision and accuracy of non-matrix-matched calibration for quantification of minor elements, using NIST SRM 610 (silicate standard), indicates that LA-ICP-MS is well suited to rapid process control of such materials. Quantitative results from LA-ICP-MS were compared with previously reported literature data obtained by use of ICP-OES and rf-GD-OES. In particular, the distribution of element impurities and their relationship to their different segregation coefficients in silicon is demonstrated. Dedicated to Professor Klaus G. Heumann     

Comparison of laser ablation-inductively coupled plasma-mass spectrometry and micro-X-ray fluorescence spectrometry for elemental imaging in Daphnia magna

Visualization of elemental distributions in thin sections of biological tissue is gaining importance in many disciplines of biological and medical research. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and scanning micro-X-ray fluorescence spectrometry (micro-XRF) are two widely used microanalytical techniques for elemental mapping. This article compares the capabilities of the two techniques for imaging the distribution of selected elements in the model organism Daphnia magna in terms of detection power and spatial resolution. Sections with a thickness of 10 and 20 μm of the fresh water crustacean Daphnia magna were subjected to LA-ICP-MS and micro-XRF analysis. The elemental distributions obtained for Ca, P, S and Zn allow element-to-tissue correlation. LA-ICP-MS and micro-XRF offer similar limits of detection for the elements Ca and P and thus, allow a cross-validation of the imaging results. LA-ICP-MS was particularly sensitive for determining Zn (LOD 20 μg g⁻¹, 15 μm spot size) in Daphnia magna, while the detection power of micro-XRF was insufficient in this context. However, LA-ICP-MS was inadequate for the measurement of the S distributions, which could be better visualized with micro-XRF (LOD 160 μg g⁻¹, 5 s live time). Both techniques are thus complementary in providing an exhaustive chemical profiling of tissue samples.     

Geochemistry study of soil affected catastrophically by tsunami disaster triggered by 2004 Indian Ocean earthquake using a fourth harmonics (λ = 266 nm) Nd:YAG laser induced breakdown spectroscopy

In this work, laser induced breakdown spectroscopy (LIBS) analysis of the soil samples collected from Aceh, a place in Indonesia worst affected by 2004 Indian Ocean tsunami, was conducted. In the LIBS experimental system, a high energy pulsed laser beam was focused on the tsunami affected soil samples and the atomic emission lines, originating from the laser induced plasma were recorded using locally developed laser induced breakdown spectrometer. Our results show that the concentrations of many elements especially terrestrial markers, namely titanium, iron, and carbonate marker such as magnesium, are higher in the tsunami-affected samples than that in the unaffected samples collected from the same neighborhood. The quantification of Ti, Fe and Mg were carried out using Ti II 334.94, Fe I 438.35, and Mg I 277.98 nm atomic transition lines respectively by drawing the calibration curve by preparing the samples of known concentrations in unaffected soil matrix. In order to ensure accurate quantification, the local thermal equilibrium of the laser-induced plasma was verified using Mc Writher criterion, for which the plasma temperature was estimated using linearized Boltzmann plot for six iron atomic transition lines and the electron number density in the plasma was estimated using Stark broadened Fe I 540.4 nm atomic lines. The estimated temperature and electron number density of the laser induced plasma are 9642 K and 3.5 × 10¹⁶ cm^?3 respectively. The concentrations of Ti, Fe and Mg in tsunami unaffected soil are 0.09, 3.2 and 0.02 w/w% and in tsunami affected soil are 0.14, 7.9 and 0.048 w/w% respectively. These values are in good agreement with XRF data. The elemental ratios extracted from LIBS signal intensity revealed that LIBS emission intensity ratios of several elements, such as Si/Ti, Al/Ti and Sr/Ba are potential candidates as the distinctive geochemical signature for identification the soil impacted and unimpacted by the 2004 Indian Ocean giant tsunami. The advantage of using LIBS for the elemental analysis is that the sample can be analyzed in its pristine form without any need cumbersome sample preparation method, which has the risk of bringing in external additives through chemicals used for the sample preparation. Other advantages of LIBS technique are that the analysis can be in situ and can be carried out remotely.     

Fast sequential multi-element determination of Ca,Mg, K,Cu, Fe,Mn and Zn for foliar diagnosis using high-resolution continuum source flame atomic absorption spectrometry: Feasibility of secondary lines,side pixel registration and least-squares background correction

The fast sequential multi-element determination of Ca, Mg, K, Cu, Fe, Mn and Zn in plant tissues by high-resolution continuum source flame atomic absorption spectrometry is proposed. For this, the main lines for Cu (324.754 nm), Fe (248.327 nm), Mn (279.482 nm) and Zn (213.857 nm) were selected, and the secondary lines for Ca (239.856 nm), Mg (202.582 nm) and K (404.414 nm) were evaluated. The side pixel registration approach was studied to reduce sensitivity and extend the linear working range for Mg by measuring at wings (202.576 nm; 202.577 nm; 202.578 nm; 202.580 nm; 202.585 nm; 202.586 nm; 202.587 nm; 202.588 nm) of the secondary line. The interference caused by NO bands on Zn at 213.857 nm was removed using the least-squares background correction. Using the main lines for Cu, Fe, Mn and Zn, secondary lines for Ca and K, and line wing at 202.588 nm for Mg, and 5 mL min^− 1 sample flow-rate, calibration curves in the 0.1–0.5 mg L^− 1 Cu, 0.5–4.0 mg L^− 1 Fe, 0.5–4.0 mg L^− 1 Mn, 0.2–1.0 mg L^− 1 Zn, 10.0–100.0 mg L^− 1 Ca, 5.0–40.0 mg L^− 1 Mg and 50.0–250.0 mg L^− 1 K ranges were consistently obtained. Accuracy and precision were evaluated after analysis of five plant standard reference materials. Results were in agreement at a 95% confidence level (paired t-test) with certified values. The proposed method was applied to digests of sugar-cane leaves and results were close to those obtained by line-source flame atomic absorption spectrometry. Recoveries of Ca, Mg, K, Cu, Fe, Mn and Zn in the 89–103%, 84–107%, 87–103%, 85–105%, 92–106%, 91–114%, 96–114% intervals, respectively, were obtained. The limits of detection were 0.6 mg L^− 1 Ca, 0.4 mg L^− 1 Mg, 0.4 mg L^− 1 K, 7.7 µg L^− 1 Cu, 7.7 µg L^− 1 Fe, 1.5 µg L^− 1 Mn and 5.9 µg L^− 1 Zn.     

Magnesium and cadmium containing Heusler phases REPd2Mg,REPd2Cd,REAg2Mg,REAu2Mg and REAu2Cd

Twenty-eight new Heusler phases REPd₂Mg, REPd₂Cd, REAg₂Mg, REAu₂Mg and REAu₂Cd with different rare earth elements were synthesized from the elements in sealed niobium ampoules in a water-cooled sample chamber of an induction furnace. The samples were characterized by powder X-ray diffraction. The cell volumes show the expected lanthanide contraction. The structures of YPd₂Cd, GdPd₂Cd, GdAu₂Cd, Y_1.12Ag₂Mg_0.88 and GdAg₂Mg were refined based on single crystal diffractometer data. The magnetic properties were determined for fifteen phase pure samples. LuAu₂Mg is a weak Pauli paramagnet with a susceptibility of 1.0(2) × 10⁻⁵ emu mol⁻¹ at room temperature. The remaining samples show stable trivalent rare earth ions and most of them order magnetically at low temperatures. The ferromagnet GdAg₂Mg shows the highest ordering temperature of T_C = 98.3 K. ¹¹³Cd and ⁸⁹Y MAS NMR spectra of YAu₂Cd and YPd₂Cd confirm the presence of unique crystallographic sites. The resonances are characterized by large Knight shifts, whose magnitude can be correlated with electronegativity trends.     

Mapping of lead,magnesium and copper accumulation in plant tissues by laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass spectrometry

Laser-Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) were utilized for mapping the accumulation of Pb, Mg and Cu with a resolution up to 200 μm in a up to cm × cm area of sunflower (Helianthus annuus L.) leaves. The results obtained by LIBS and LA-ICP-MS are compared with the outcomes from Atomic Absorption Spectrometry (AAS) and Thin-Layer Chromatography (TLC). It is shown that laser-ablation based analytical methods can substitute or supplement these techniques mainly in the cases when a fast multi-elemental mapping of a large sample area is needed.     

Application of multivariate optimization in the development of an ultrasound-assisted extraction procedure for multielemental determination in bean seeds samples using ICP OES

In this paper, multivariate optimization was applied for the development of an ultrasound-assisted multielemental extraction procedure for analysis of bean samples by inductively coupled plasma optical emission spectrometry. For this procedure, powdered samples were treated with an acid mixture and submitted to ultrasound energy for extracting the target elements (Ba, Ca, Cu, Fe, K, Mg, Mn, Sr and Zn). Centroid simplex mixture design was used for optimize the acid proportions (nitric, acetic and chloride acid) and Box Behnken design was applied for optimize the process variables (particle size, final concentration of extracting solution and sonication time) after mixture optimization. Iron had not presented quantitative extractions and it was excluded from final samples analysis. The developed method presents the follow limits of quantification in μg g^{− 1}: Ba (0.90); Ca (5.2); Cu (4.0); K (0.90); Mg (1.4); Mn (0.22); Sr (0.25) and Zn (4.0). Accuracy was accessed by comparison of determined concentration with the values obtained by the microwave digestion procedure. The proposed method was applied toward the determination of elemental composition in bean samples collected in the country zone from Jequié city located on the Bahia State, Brazil. The trace elements content ranged from 0.21 to 3.04, 3.84 to 10.8, 0.60 to 5.23, 31.0 to 46.5 and 10.8 to 19.6 μg g^{− 1} Ba, Cu, Sr, Zn, Mn, respectively. The major elements content ranged from 0.0418 to 0.0877, 0.109 to 0.153 and 1.30 to 1.56% (w/w) Ca, Mg and K, respectively.     

A rapid approach for assessment of arsenic exposure by elemental analysis of single strand of hair using laser ablation-inductively coupled plasma-mass spectrometry

Application of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) as a method for identification of arsenic in a single hair strand was investigated. Using a single point ablation method detectability of ⁷⁵As and other two elements (²⁰⁸Pb and ⁶⁴Zn) were evaluated. Arsenic (⁷⁵As) signal is improved with enhanced laser ablation conditions. For the arsenic determination in hair single spots or single linear scans with enhanced laser ablation conditions described in the paper are satisfactory although  800 μm linear scans may be preferable. Arsenic levels in a single strand of hair from individuals who were chronically exposed to arsenic contaminated drinking water from a village in the Atacama Desert in northern Chile were determined by LA-ICP-MS. These results were satisfactorily correlated with total As concentration previously measured by hydride generation (HG)-ICP-MS. The sample throughput is high and it takes  3 min per each hair sample including mounting, focusing and analysis. LA-ICP-MS method can be used for the rapid identification and screening of toxic and nutritionally important elements in hair.