High-resolution Continuum-source Atomic Absorption Spectrometry Research Articles

Lithium isotope ratio analysis of geological samples using atomic absorption spectrometry with improved spectral resolution

This study introduces an improved spectrometric method with enhanced precision to determine isotope ratios in geological samples without chromatographic separation. Firstly, the improvement is achieved by increasing the spectral resolution of the spectrometer applied in well-known high-resolution continuum source atomic absorption spectrometry (HR-CS-AAS). The resulting resolving power and linear dispersion of the upgraded setup, which is denoted in the following as HR+CS-AAS, is well adapted to the line widths of the Li isotope components we investigated. Secondly, our proposed method combines optical absorption spectrometry with machine learning data analysis using an extreme gradient boosting algorithm (XGBoost). This method was applied to analyze certified geological reference materials with δLSVEC(7Li/6Li) (hereafter δ7Li) values ranging from −0.5 ‰ to 4.5 ‰. With a pixel related optical resolving power of λ/∆λ ≈ 780 000, we obtain precisions in δ7Li measurements from 1.0 ‰ to 2.5 ‰. The method is validated by comparing the results with multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), confirming its metrological compatibility. This work presents a fast, robust, and reliable method for δ7Li measurement in geological samples.

Potent Anticancer Activity of a Dinuclear Gold(I) bis-N-Heterocyclic Imine Complex Related to Thioredoxin Reductase Inhibition in Vitro.

A dinuclear gold(I) complex featuring a strongly donating bis-N-heterocyclic imine ligand was synthesised and characterised by different methods, including single crystal X-ray diffraction (SC-XRD) analysis. The compound has been tested for its antiproliferative effects in a panel of human cancer cell lines in vitro, showing highly selective anticancer effects, particularly against human A549 non-small cell lung cancer cells (NSCLC), with respect to non-tumorigenic cells (VERO). The accumulation of the compound in A549 and VERO cells was studied by high-resolution continuum source atomic absorption spectrometry (HRCS-AAS), revealing that the anticancer effects are not particularly related to the different amounts of gold taken up by the cells over 72 h. Enzyme inhibition studies to evaluate the activity of the seleno-enzyme thioredoxin reductase (TrxR) in cancer cell extracts show that the gold(I) compound is a potent inhibitor (IC50=0.567±0.208 μM), while the free ligand is ineffective. This result correlates with the observed compound's selectivity towards A549 cells overexpressing the enzyme.

Determination of residual dimethyl sulfoxide by high-resolution continuum source graphite furnace molecular absorption spectrometry

High-resolution continuum source molecular absorption spectrometry (HR-CSMAS) has been extended to the determination of sulfur-containing organic molecule, on the example of dimethyl sulfoxide (DMSO) as a residual solvent in CH3NH3PbI3 perovskite thin films. For this purpose, DMSO molecules were converted into CS molecules by pyrolysis in a graphite furnace at low temperature and the sulfur content was determined by measuring molecular absorption of CS at 258.055 nm. An aqueous solution of DMSO was used for calibration. A characteristic mass of 17 ng was achieved for S after pyrolysis at 160 °C by using Pd as a chemical modifier. Furthermore, the content of DMSO was normalized to that of Pb whereas the content of Pb was determined by reducing the Pb in the perovskite to metallic Pb with Zn powder and measuring absorption of the weak Pb line at 261.418 nm by high-resolution continuum source atomic absorption spectrometry (HR-CSAAS). The Pb content remained constant whereas the S/Pb molar ratio decreased with increasing annealing time. Our results open new opportunities for the characterization of residual DMSO in wide classes of materials.

The HR-CS-GF-AAS determination and preconcentration of palladium in contaminated urban areas, especially in lichens

The increasing content of platinum group metal particles emitted into the environment by car traffic is gradually attracting the attention of the scientific community. However, the methods for the determination of platinum group metals in environmental matrices are either costly or suffer from low sensitivity. To facilitate the use of less sensitive, but significantly cheaper, devices, the preconcentration of platinum group metals is employed. For platinum, a multitude of preconcentration approaches have been published. On the contrary, the preconcentration approaches for palladium are still rare. In this work, the development, optimization, and testing of a new approach is described; it is based on a preconcentration of palladium on octadecyl modified silica gel together with the complexing agent dimethylglyoxime, and it is then analyzed with the high-resolution continuum-source atomic absorption spectrometry. For comparison, a newly developed sorbent, QuadraSil™ TA, with a high affinity for platinum group metals was also tested. The preconcentraiton approach was tested on the lichen Hypogymnia physodes, which served as a bioindicator of palladium emissions. The case study site was a mid-sized city in central Europe: Brno, Czech Republic. The dry “bag” monitoring technique was used to collect the palladium near roads with a large span of traffic density. The developed analytical approach confirmed an increasing concentration of palladium with increasing exposure time and intensity of the traffic. Consequently, a simple relationship between the amount of bioaccumulated palladium and traffic density was established.

Levels of Trace Elements in Black Teas Commercialized in Saudi Arabia Using Inductively Coupled Plasma Mass Spectrometry.

The present work has been demonstrated a developed method for the determination of Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, As, Cr, Pb, and V in different types of black teas collected from Saudi Arabia market using inductively coupled plasma mass spectrometry (ICP-MS). Each sample represents a well-mixed combination of ten packets from the same type collected from the market. Detection limits in ngg-1 were 76.06, 166.03, 5.94, 2.94, 18.29, 18.29, 9.00, 0.48, 0.48, 7.67, 3.07, and 4.21 for Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, As, Cr, Pb, and V, respectively. In order to validate the developed method, a certified reference material of green tea was analyzed. Further comparison with the results obtained from high-resolution continuum source atomic absorption spectrometry (HR-CS-AAS) was demonstrated. The obtained good agreement confirms the validity of the investigated method. Fortunately, the concentrations of the heavy metals locate on the range of the international values. The highest metal content was found in Al-Rabee tea, and this type results should be confirmed by using a large number of samples in order to have satisfied and confirmed statistical analysis results.

High-Resolution Continuum Source Atomic Absorption Spectrometry with Microwave-Assisted Extraction for the Determination of Metals in Vegetable Sprouts

The goal of this study was to investigate the enrichment of garden cress (Lepidium sativum), mung beans (Vigna radiata), and soybeans (Glycine max) with minerals. Hydroponic nutrient solutions were enriched with Zn2+,Cr3+, Ca2+, Mg2+, and Se2+. Morphological assessment was based on monitoring changes that occurred as a function of the concentrations of elements in the medium. The growth of the plant, as a result of a stimulating or inhibitory effect of the identity and concentration of elements on the germination process, was characterized. Microbiological contamination was identified and catabolic profiles of two bacterial strains were performed. High-resolution continuum source atomic absorption spectrometry (HR-AAS) was used to determine Zn2+, Cr3+, Ca2+, Mg2+, and Se2+ in dried plant material after sample pretreatment using microwave-assisted extraction. The limits of detection were 0.010, 0.029, 0.013, 0.151, and 0.030 milligram per liter for Ca2+, Cr3+, Mg2+, Se2+, and Zn2+, respectively. Recoveries were higher than 98 percent and the relative standard deviation was less than 5 percent. The accuracy of the procedure was estimated by analyzing certified reference materials. The results showed that biofortification of garden cress by zinc holds the highest promise for the creation of designer foods. Garden cress was found to have the highest bioconcentration factor among the investigated plants; at 50 parts per million, plant growth was stimulated without contamination by microorganisms.

Detection of silver nanoparticles in parsley by solid sampling high-resolution–continuum source atomic absorption spectrometry

In this work, we present a fast and simple approach for detection of silver nanoparticles (AgNPs) in biological material (parsley) by solid sampling high-resolution-continuum source atomic absorption spectrometry (HR-CS AAS). A novel evaluation strategy was developed in order to distinguish AgNPs from ionic silver and for sizing of AgNPs. For this purpose, atomisation delay was introduced as significant indication of AgNPs, whereas atomisation rates allow distinction of 20-, 60-, and 80-nm AgNPs. Atomisation delays were found to be higher for samples containing silver ions than for samples containing silver nanoparticles. A maximum difference in atomisation delay normalised by the sample weight of 6.27 ± 0.96smg(-1) was obtained after optimisation of the furnace program of the AAS. For this purpose, a multivariate experimental design was used varying atomisation temperature, atomisation heating rate and pyrolysis temperature. Atomisation rates were calculated as the slope of the first inflection point of the absorbance signals and correlated with the size of the AgNPs in the biological sample. Hence, solid sampling HR-CS AAS was proved to be a promising tool for identifying and distinguishing silver nanoparticles from ionic silver directly in solid biological samples.

Multi-elemental analysis of ready-to-eat “baby leaf” vegetables using microwave digestion and high-resolution continuum source atomic absorption spectrometry

The mineral content (phosphorous (P), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu)) of eight ready-to-eat baby leaf vegetables was determined. The samples were subjected to microwave-assisted digestion and the minerals were quantified by High-Resolution Continuum Source Atomic Absorption Spectrometry (HR-CS-AAS) with flame and electrothermal atomisation. The methods were optimised and validated producing low LOQs, good repeatability and linearity, and recoveries, ranging from 91% to 110% for the minerals analysed. Phosphorous was determined by a standard colorimetric method. The accuracy of the method was checked by analysing a certified reference material; results were in agreement with the quantified value. The samples had a high content of potassium and calcium, but the principal mineral was iron. The mineral content was stable during storage and baby leaf vegetables could represent a good source of minerals in a balanced diet. A linear discriminant analysis was performed to compare the mineral profile obtained and showed, as expected, that the mineral content was similar between samples from the same family. The Linear Discriminant Analysis was able to discriminate different samples based on their mineral profile.

Palladium as chemical modifier for the stabilization of volatile nickel and vanadium compounds in crude oil using graphite furnace atomic absorption spectrometry

It has been observed in previous work using high-resolution continuum-source atomic absorption spectrometry that up to 50% of the nickel and vanadium in crude oil, most likely non-polar nickel and vanadyl porphyrin complexes, was already lost at pyrolysis temperatures >400 °C, whereas the rest of the analyte was stable up to at least 1200 °C. In this work we were investigating the use of a chemical modifier in order to avoid these low-temperature losses and also to make possible a differential determination of the volatile analyte fractions. Oil-in-water emulsions, using Triton X-100 as surfactant, were used for easy sample handling. A mass of 20 μg of Pd, introduced into the graphite tube and thermally pretreated prior to the injection of the emulsion, was found to efficiently prevent any low-temperature losses of nickel and vanadium from crude oil samples up to pyrolysis temperatures of 1200 °C and 1450 °C, respectively. The best characteristic mass obtained was m0 = 16 pg for Ni and m0 = 33 pg for V. The limits of detection and quantification were 0.02 μg g−1 and 0.065 μg g−1, respectively, for Ni, and 0.06 μg g−1 and 0.17 μg g−1, respectively, for V in oil, based on an emulsion of 2 g of oil in 10 mL. The precision expressed as relative standard deviation (n = 9) for a crude oil containing about 5 μg g−1 Ni and 3 μg g−1 V was 2.0% and 3.1% for Ni and V, respectively. The accuracy of the procedure was verified by analyzing the certified reference material NIST SRM 1634c, trace metals in fuel oil, and the research material RM 8505, vanadium in crude oil.

High-resolution continuum-source atomic absorption spectrometry: what can we expect?

Um novo conceito instrumental vem sendo desenvolvido para espectrometria de absorcao atomica (AAS), usando como fonte de radiacao uma lâmpada de xenonio de alta intensidade, um monocromador double-echelle e um dispositivo com arranjo de carga acoplada como detector, permitindo uma resolucao de ~2 pm por pixel. Entre as principais vantagens do sistema estao: i) uma melhora na razao sinal/ruido devido a elevada intensidade da fonte de radiacao, resultando em melhor precisao e limites de deteccao; ii) pelo mesmo motivo, nao ha mais linhas “fracas”, portanto raias secundarias podem ser usadas sem comprometimentos; iii) novos elementos podem ser determinados, para os quais fontes de radiacao ainda nao sao disponiveis; iv) toda a regiao espectral nas vizinhancas da raia analitica torna-se “visivel”, possibilitando muito mais informacoes do que as obtidas por instrumentos convencionais de AAS; v) a deteccao com arranjo de carga acoplada permiti uma correcao simultânea real da radiacao de fundo nas proximidades da raia analitica; vi) o software possibilita a armazenagem de espectros de referencia, por exemplo, de espectro de absorcao molecular com estruturas rotacionais finas, e a subsequente subtracao deste do espectro de uma amostra , usando-se o algoritmo dos minimos quadrados, sendo assim possivel a correcao de fundo estruturado mesmo sob a raia analitica; vii) embora ainda nao disponivel, se um detector bidimensional apropriado for usado o sistema permitira em AAS medidas simultâneas multielementares, pratica comum em espectrometria de emissao otica; (viii) finalmente, experimentos preliminares vem indicando que o novo instrumental podera resultar em um melhor desempenho analitico na determinacao de elementos traco em matrizes complexas. A new instrumental concept has been developed for atomic absorption spectrometry (AAS), using a high-intensity xenon short-arc lamp as continuum radiation source, a high-resolution doubleechelle monochromator and a CCD array detector, providing a resolution of ~2 pm per pixel. Among the major advantages of the system are: i) an improved signal-to-noise ratio because of the high intensity of the radiation source, resulting in improved photometric precision and detection limits; ii) for the same reason, there are no more ‘weak’ lines, i.e. secondary lines can be used without compromises; iii) new elements might be determined, for which no radiation source has been available; iv) the entire spectral environment around the analytical line becomes ‘visible’, giving a lot more information than current AAS instruments; v) the CCD array detector allows a truly simultaneous background correction close to the analytical line; vi) the software is capable of storing reference spectra, e.g. of a molecular absorption with rotational fine structure, and of subtracting such spectra from the spectra recorded for a sample, using a least squares algorithm; vii) although not yet realized, the system makes possible a truly simultaneous multi-element AAS measurement when an appropriate two-dimensional detector is used, as is already common practice in optical emission spectrometry; vii) preliminary experiments have indicated that the instrumental concept could result in a more rugged analytical performance in the determination of trace elements in complex matrices.

Investigation of interferences in the determination of thallium in marine sediment reference materials using high-resolution continuum-source atomic absorption spectrometry and electrothermal atomization

A high-resolution continuum-source atomic absorption spectrometer with a xenon short-arc lamp as the radiation source, a compact double echelle monochromator with a focal length of 302 mm and a spectral resolution of λ/Δλ≈110 000, and a UV-sensitive charged-coupled device (CCD) array detector was used to investigate the spectral interferences found with a conventional line-source atomic absorption spectrometer in the determination of thallium in marine sediment reference materials. A transversely heated graphite furnace was used as the atomizer unit, and the samples were introduced in the form of slurries. A strong iron absorption line at 276.752 nm, which was observed at atomization temperatures >2000 °C in the vicinity of the thallium resonance line at 276.787 nm, could be responsible for some of the interferences observed with low-resolution continuum-source background correction. The outstanding feature at atomization temperatures <2000 °C was the electron excitation spectrum of the gaseous SO 2 molecule that exhibited a pronounced rotational fine structure, and is for sure the main reason for the observed spectral interferences. The molecular structures could be removed completely by subtracting a model spectrum recorded during the atomization of KHSO 4, using a least squares algorithm. The same results, within experimental error, were obtained for thallium in a variety of marine sediment reference materials using ammonium nitrate as a modifier, ruthenium as a permanent modifier in addition to ammonium nitrate, and without a modifier, using aqueous standards for calibration, demonstrating the ruggedness of the method. A characteristic mass of 15–16 pg Tl was obtained, and a limit of detection of 0.02 μg g −1 Tl was calculated from the standard deviation of five repetitive determinations of HISS-1, the sediment with the lowest thallium content.

High-Resolution continuum-source atomic absorption spectrometry in an inductively coupled plasma with photodiode array detection

Atomic absorption spectrometry (AAS) is a well established technique using flames and graphite furnaces. An inductively coupled plasma (ICP), however, is an attractive alternative atom/ion reservoir. A high-resolution continuum-source atomic absorption spectrometer with a photodiode array detector and an ICP as the atomization/ionization reservoir is described. Multi-wavelength capability permits the simultaneous determination of several elements by their atomic and/or ionic transitions. Each acquired spectrum is averaged for 10 s to improve the signal-to-noise ratios. Detection limits are calculated for 14 elements and compared with literature values.