Direct Analysis Of Solid Samples Research Articles

Rare earth elements profile in a cultivated and non-cultivated soil determined by laser ablation-inductively coupled plasma mass spectrometry

Rare earth elements (REEs) have several applications but the effects on environment are not well known. Therefore, the aim of this work is to establish a method for direct solid sample analysis by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) to evaluate the concentration and distribution of REEs in cultivated and non-cultivated soil. Samples were collected in two areas to 40 cm of depth. The LA-ICP-MS method is easy to be implemented and the sample treatment is very fast comprising only its drying, grounding and pressing as a pellet. The accuracy of the method was evaluated by using a certified reference material (BCR 667 – Estuarine Sediment, Institute for Reference Materials and Measurements (IRMM)) where good agreement with the certified values was obtained. Analyte recovery at two levels of concentration (2.5 and 15.0 μg g−1) was also performed and recoveries in the range of 85%–120% were achieved, values that are acceptable for LA-ICP-MS analysis. In general, the concentration of the REEs is higher in the cultivated soil and increased from the surface to deeper layers, which can be a consequence of fertilizer application.

Determination of Cr, Cu and Pb in industrial waste of oil shale using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

Three methods were developed for Cr, Cu and Pb determination in oil shale residues using direct solid analysis.

Investigation of spectral interference in the determination of Pb in road dust using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

Pb determination using HR-CS SS-GF AAS in road dust samples and evaluation of spectral interference.

Characterization and application of in-vacuum PIXE/EBS system for the direct elemental analysis of thick solid biological samples

Utilization of combined particle-induced X-ray emission (PIXE) and elastic backscattering (EBS) spectrometry for the direct elemental analysis of thick solid biological samples was thoroughly discussed. Powdered samples pressed as pellets were directly analyzed. Combination of applying low ion beam currents, random scanning of the sample across the beam during data acquisition, and using special sample holder enabled effective minimization of local ion beam heating. This subsequently inhibited potential element loss during ion beam irradiation. Matrix elements were determined from multiple EBS spectra, which were acquired using three different ion beam energies. Subsequently, averaging of the elemental concentrations obtained was achieved using novel MultiSIMNRA software. Moreover, combined EBS spectrometry, nuclear reaction analysis (NRA), and elastic recoil detection analysis (ERDA) measurements were used to overcome the limitations of using EBS separately and subsequently obtain accurate matrix element concentrations. The validity of the PIXE/EBS system for the direct elemental analysis of thick biological samples was comprehensively evaluated. The obtained concentration values demonstrated reliable results for most investigated elements (5–15%), starting from sodium onwards. The non-satisfying results were evaluated and justified.

Determination of silicon in biomass and products of pyrolysis process via high-resolution continuum source atomic absorption spectrometry

Thermochemical processes can convert the biomass into fuels, such as bio-oil. The biomass submitted to pyrolysis process, such as fibers, are generally rich in silicon, an element that can lead to damages in an engine when there is high concentration in a fuel. High-resolution continuum source atomic absorption spectrometry (HR-CS AAS) is an interesting alternative for Si determination in the products and byproducts of the pyrolysis process because, besides the flame (F) and graphite furnace (GF) atomizers, it has enhanced the application of direct analysis of solid samples (SS) within GF. This study aimed the development of methods to determine Si in biomass samples, their products and byproducts using HR-CS AAS. A high-resolution continuum source atomic absorption spectrometer contrAA 700 equipped with F and GF atomizers was used throughout the study. HR-CS F AAS (λ = 251.611nm, 1 detection pixel, N2O/C2H2 flame) was used to evaluate Si content in biomass and ash, after a microwave-assisted acid digestion with HNO3 and HF. HR-CS GF AAS (Tpyr = 1400°C, Tatom = 2650°C) has evaluated Si in pyrolysis water and bio-oil at 251.611nm, and in peach pit biomass and ash at 221.174nm using SS, both wavelengths with 1 detection pixel. Rhodium (300μg) was applied as permanent modifier and 10μgPd + 6μg Mg were pipetted onto the standards/samples at each analysis. Three different biomass samples were studied: palm tree fiber, coconut fiber and peach pit, and three certified reference materials (CRM) were used to verify the accuracy of the methods. The figures of merit were LOD 0.09–20mgkg–1, and LOQ 0.3–20mgkg–1, considering all the methods. There were no significant differences between the CRM certified values and the determined ones, using a Student t-test with a confidence interval of 95% (n = 5). Si concentration ranged from 0.11–0.92% mm–1, 1.1–1.7mgkg–1, 3.3–13mgkg–1, and 0.41–1.4%mm–1, in biomass, bio-oil, pyrolysis water and ash, respectively. Si remained mostly in the ash, leading to a mass fraction of up to 103%, even when the Si loss is not considered. Silicon concentration in bio-oil was below 1.7mgkg–1, which is suitable for its application as a fuel. The developed methods using HR-CS AAS are suitable for Si determination in biomass, bio-oil, pyrolysis water, and ash. The application of bio-oil as an alternative fuel would be possible evaluating its Si content due to its low levels. The mass balance for Si has proved to be an important tool in order to evaluate the correct disposal of pyrolysis process byproducts.

Determination of fluorine in copper concentrate via high-resolution graphite furnace molecular absorption spectrometry and direct solid sample analysis – Comparison of three target molecules

The chemical composition of complex inorganic materials, such as copper concentrate, may influence the economics of their further processing because most smelters, and particularly the producers of high-purity electrolyte copper, have strict limitations for the permissible concentration of impurities. These components might be harmful to the quality of the products, impair the production process and be hazardous to the environment. The goal of the present work is the development of a method for the determination of fluorine in copper concentrate using high-resolution graphite furnace molecular absorption spectrometry and direct solid sample analysis. The molecular absorption of the diatomic molecule CaF was measured at 606.440nm. The molecule CaF was generated by the addition of 200µg Ca as the molecule-forming reagent; the optimized pyrolysis and vaporization temperatures were 900°C and 2400°C, respectively. The characteristic mass and limit of detection were 0.5ng and 3ng, respectively. Calibration curves were established using aqueous standard solutions containing the major components Cu, Fe, S and the minor component Ag in optimized concentrations. The accuracy of the method was verified using certified reference materials. Fourteen copper concentrate samples from Chile and Australia were analyzed to confirm the applicability of the method to real samples; the concentration of fluorine ranged from 34 to 5676mgkg−1. The samples were also analyzed independently at Analytik Jena by different operators, using the same equipment, but different target molecules, InF and GaF, and different operating conditions; but with a few exceptions, the results agreed quite well. The results obtained at Analytik Jena using the GaF molecule and our results obtained with CaF, with one exception, were also in agreement with the values informed by the supplier of the samples, which were obtained using ion selective electrode potentiometry after alkaline fusion. A comparison will also be made for the three target molecules and the three independently developed methods for the determination of fluorine, although all three methods used direct solid sample analysis.

Determination of Co and Cr in wet animal feeds using direct solid sample analysis by HR-CS GF AAS

The present study proposes the determination of Cr and Co in wet animal feeds for employing direct solid sample analysis (SS) and high resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). For determination of Cr and Co, the analytical lines 357.8687nm and 240.7254nm were used, respectively. The pyrolysis temperatures were 1500 and 1400°C and atomization temperatures were 2500 and 2400°C for Cr and Co, respectively. The limits of quantification (LoQ) obtained for Cr was 0.03μgg−1 and 0.17μgg−1 for Co. The characteristic masses (m0) also obtained were 2.2pg for Cr and 2.9pg for Co. The accuracy of the proposed methods was performed by analysis of standard reference materials (SRM) of tomato leaves (NIST 1573), bovine muscle powder (NIST 8414) and apple leaves (NIST 1515) for Cr and bovine liver (NIST 1577b) for Co. The trueness obtained were between 102±9 and 116±7% for Cr and 94±8% for Co for analyzed of the SRM. Precision, expressed as relative standard deviation (RSD), was better than 8.7% for Cr and 8.3% for Co (n=5). Thirteen wet animal feed samples for dogs and cats were analyzed. The concentrations values found for Cr in the samples ranged from 0.17±0.01 to 0.59±0.06μgg−1 with an average of 0.36±0.13μgg−1 (n=13). On the other hand, the obtained concentrations for Co ranged between <0.18 and 12.57±1.11μgg−1, with an average of 5.92±3.19μg. The optimized analytical methods were simple, fast, efficient, precise and accurate for determination of Cr and Co in wet animal feeds for cats and dogs by HR-CS SS-GF AAS. Additional advantage of the method was no dissolution of the samples, no use of harmful reagents and consequently no generation of residues, besides the use of an effective analytical technique that allows optimization of fast and reliable screening procedures.

A comparison of laser ablation-inductively coupled plasma-mass spectrometry and high-resolution continuum source graphite furnace molecular absorption spectrometry for the direct determination of bromine in polymers

This work describes the development and comparison of two methods for the direct determination of Br in polymer samples via solid sampling, one using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and the other using high-resolution continuum source graphite furnace molecular absorption spectrometry with direct solid sample analysis (HR-CS SS-GF MAS). The methods were optimized and their accuracy was evaluated by comparing the results obtained for 6 polymeric certified reference materials (CRMs) with the corresponding certified values. For Br determination with LA-ICP-MS, the 79Br+ signal could be monitored interference-free. For Br determination via HR-CS SS-GF MAS, the CaBr molecule was monitored at 625.315nm with integration of the central pixel±1. Bromine quantification by LA-ICP-MS was performed via external calibration against a single CRM while using the 12C+ signal as an internal standard. With HR-CS SS-GF MAS, Br quantification could be accomplished using external calibration against aqueous standard solutions. Except for one LA-ICP-MS result, the concentrations obtained with both techniques were in agreement with the certified values within the experimental uncertainty as evidenced using a t-test (95% confidence level). The limit of quantification was determined to be 100μgg−1 Br for LA-ICP-MS and 10μgg−1 Br for HR-CS SS-GF MAS.

Validity of Generalized Standard Addition Method for a Mixture of Amino Acid Analysis

A Modified version of the Generlized standard addition method ( GSAM) was developed. This modified version was used for the quantitative determination of arginine (Arg) and glycine ( Gly) in arginine acetyl salicylate – glycine complex . According to this method two linear equations were solved to obtain the amounts of (Arg) and (Gly). The first equation was obtained by spectrophotometic measurement of the total absorbance of (Arg) and (Gly) colored complex with ninhydrin . The second equation was obtained by measuring the total acid consumed by total amino groups of (Arg) and ( Gly). The titration was carried out in non- aqueous media using perchloric acid in glacial acetic acid as a titrant. The developed method is accurate, precise, and free from interferences and may provide a useful approach to calibrate in the direct analysis of solid sample and it is suitable method to be used as a quality control procedure.&#x0D; Key words: GSAM , amino acid analysis

Simultaneous determination of nickel and iron in vegetables of Solanaceae family using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

A method has been developed for the simultaneous determination of Ni and Fe in vegetables of the Solanaceae family (bell pepper, tomato, potato, eggplant, physalis, and red pepper) using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis (HR-CS SS-GF AAS). The vegetables were cultivated using both conventional and “organic” farming. The samples were lyophilized, milled, and the particle size was controlled using a 200μm polyester sieve. The primary absorption line for Ni at 232.003nm and a secondary line for Fe at 232.036nm were used throughout the study. Pyrolysis and atomization temperatures for both analytes were 1400°C and 2500°C, respectively. The molecular spectrum of SiO appeared during atomization, and it was corrected using a least-squares algorithm. The calibration was carried out with aqueous standard solutions. The characteristic masses for Ni and Fe were 95pg and 340pg, respectively. The LODs of Ni and Fe were 0.02μgg−1 and 2μgg−1, and the LOQs were 0.06μgg−1and 6μgg−1, respectively. The accuracy of the method was confirmed by analyzing a certified reference material of tomato leaves (SRM NIST 1573a). The concentrations of Fe were different for conventional and organic farming, whereas only one group of organically grown vegetables had higher Ni concentrations than the conventionally grown.

Design and evaluation of a new bench-top instrument for laser-induced breakdown spectroscopy

ABSTRACTA newly designed and developed bench-top instrument is reported for laser-induced breakdown spectroscopy offering compact size and relatively low cost. A miniature laser was designed in the laboratory with a small volume and a light weight. The spectrometer was controlled using laboratory-written software. The instrument is suitable for the direct and rapid analysis of solid samples after simple pretreatment. Good stability and accuracy were achieved for quantitative analysis. The performance of the instrument was evaluated by qualitative and quantitative analyses of nickel ore for Mn, Al, Fe, Cr, Zn, Mg, Si, and Ca. The quantitative analysis showed linear calibration graphs and small relative standard deviations. The results show that the new instrument is suitable for elemental analysis.

Alternative method for chromium determination in pharmaceutical drugs by HR-CS GF AAS and direct analysis of solid samples

High-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) was used to develop an analytical method for chromium determination in pharmaceutical drugs through direct analysis of solid samples. The limit of detection and quantification were, respectively, 2.9μgkg−1 and 9.7μgkg−1 and the characteristic mass was 2.0pg. Eighteen pharmaceutical drugs and three excipients were analyzed. The encapsulated samples were opened and only its powder content was analyzed; the tablet samples were grinded before the analysis. The results obtained from the direct analysis of the solid samples were in agreement with those found after total digestion of samples using a closed-vessel microwave oven device, with a confidence level of 95%. The Cr concentration obtained for the different capsules and tablets investigated varied between 0.05 and 1.92mgkg−1. The proposed method is fast, reliable and simple for routine pharmaceutical analysis.

Inductively Coupled Plasma Optical Emission Spectrometry for Rare Earth Elements Analysis

Abstract Inductively coupled plasma optical emission spectrometry (ICP-OES) merits multielements capability, high sensitivity, good reproducibility, low matrix effect and wide dynamic linear range for rare earth elements (REEs) analysis. But the spectral interference in trace REEs analysis by ICP-OES is a serious problem due to the complicated emission spectra of REEs, which demands some correction technology including interference factor method, derivative spectrum, Kalman filtering algorithm and partial least-squares (PLS) method. Matrix-matching calibration, internal standard, correction factor and sample dilution are usually employed to overcome or decrease the matrix effect. Coupled with various sample introduction techniques, the analytical performance of ICP-OES for REEs analysis would be improved. Compared with conventional pneumatic nebulization (PN), acid effect and matrix effect are decreased to some extent in flow injection ICP-OES, with higher tolerable matrix concentration and better reproducibility. By using electrothermal vaporization as sample introduction system, direct analysis of solid samples by ICP-OES is achieved and the vaporization behavior of refractory REEs with high boiling point, which can easily form involatile carbides in the graphite tube, could be improved by using chemical modifier, such as polytetrafluoroethylene and 1-phenyl-3-methyl-4-benzoyl-5-pyrazone. Laser ablation-ICP-OES is suitable for the analysis of both conductive and nonconductive solid samples, with the absolute detection limit of ng-pg level and extremely low sample consumption (0.2 % of that in conventional PN introduction). ICP-OES has been extensively employed for trace REEs analysis in high-purity materials, and environmental and biological samples.

Determination of chlorine in cement via CaCl molecule by high-resolution continuum source graphite furnace molecular absorption spectrometry with direct solid sample analysis

The use of a new molecule the calcium mono-chloride (CaCl) with absorption band head at 621.145nm was evaluated in the development of a method for Cl determination in cement by high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GFMAS) employing direct solid sample analysis. Calcium compounds present in cement samples acted as CaCl-forming reagent. Pyrolysis and vaporization curves were established to optimize the atomizer temperature program. The optimum pyrolysis and vaporization temperatures were 1000°C and 2200°C, respectively. These values provided higher thermal stability of the CaCl molecule which allows reducing matrix effects and the calibration with aqueous standard solutions in the range of 10–200ng Cl. Correlation coefficient of 0.995 and a slope of 0.00159sng−1 were obtained, with a calculated limit of detection of 1.4ng Cl. Sample masses in the range 0.65–1.05mg can be accurately weighed and assayed. Commercial cement samples were analyzed by the proposed method and the concentrations of Cl were in the 159–540μgg−1 concentration range. Samples were also analyzed by the Brazilian Association of Technical Norms (ABNT) and results were in agreement at a 95% confidence level (paired t-test). Recoveries of Cl added to samples were in the range 101–118% and the relative standard deviations (n=12) were in the 3.4–11.2% interval.

Fast and direct detection of metal accumulation in marine sediments using laser-induced breakdown spectroscopy (LIBS): a case study from the Bay of Cienfuegos, Cuba†

Metal accumulation in sediments from Cienfuegos Bay assessed by Laser-induced breakdown spectroscopy (LIBS) suitable for the direct analysis of solid samples.

Development of analytical methods for the determination of copper and manganese in infant formula using high resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

Two fast, simple and reliable methods for the determination of Cu and Mn in infant formula were developed by HR-CS GF AAS.

Determination of cadmium, chromium and copper in vegetables of the Solanaceae family using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

Three methods have been developed for the determination of Cd, Cr, and Cu in vegetables of the Solanaceae family cultivated in different farming systems by HR-CS SS-GF AAS.

New Spectral Systems Based on MAES Analyzers

We present a review of the spectral systems developed by “VMK-Optoelektronika” company for atomic-emission spectral analysis: Grand Globula, Grand Kristall, and Express intended for direct atomic-emission spectral analysis of solid metal and powder samples; Grand-Potok desired for rapid analysis of powders by the spill-injection method; Grand-Expert and Favorit for rapid analysis of metals and alloys; spark sampling systems Aspekt for analysis of metal samples using ISP-AES and ISP-MS; Express-Oil for direct analysis of oils; and Pavlin for rapid determination of sodium, lithium, potassium, calcium, barium, cesium, and rubidium in solutions. The design of the spectrometers and performance data are presented.

Direct Determination of Trace Elements in Meat Samples via High-Resolution Graphite Furnace Atomic Absorption Spectrometry

This work presents a direct and straightforward approach for the determination of trace elements in fish muscle, oyster, and bovine liver via direct solid sample analysis (SS) using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). The preliminary studies revealed the presence of spectral interferences at the analytical line of Ni at 231.096 nm, which could be corrected subtracting the spectrum of SiO and PO from the sample spectra using least-squares background correction. Moreover, all meat samples were proven homogeneous according to the homogeneity factor (H e) (all values were <10 mg½). Pyrolysis (Tp) and atomization (Ta) temperatures were studied and optimized as 800 °C (Tp) and 2500 °C (Ta) for Mn, 700 °C (Tp) and 2600 °C (Ta) for Ni, and 600 °C (Tp) and 2500 °C (Ta) for Rb. Calibration against aqueous standards was proven feasible for Mn determination, whereas Ni and Rb required calibration against solid standards for their quantification. The detection limits achieved were demonstrated adequate for application to food analysis (0.005 μg g−1 for Mn, 0.002 μg g−1 for Ni, and 0.1 μg g−1 for Rb). The developed method was successfully applied for the elemental analysis of fish muscle, oyster, and bovine liver and three certified reference materials, demonstrating good agreement with the certified values and with the reference technique at a 95 % statistical confidence level.

Determination of chlorine via the CaCl molecule by high-resolution continuum source graphite furnace molecular absorption spectrometry and direct solid sample analysis

This work investigates the possibilities of high-resolution continuum source graphite furnace molecular absorption spectrometry for the direct determination of Cl in solid samples via the CaCl molecule and measurement of its molecular absorption. The method proposed is based on addition of 400µg Ca as molecule-forming reagent and of 20µgPd as chemical modifier, which helps to stabilize the analyte and enhances sensitivity.The molecular spectrum for CaCl offers different lines with different limits of detection and linear ranges, which permitted to analyze solid samples with different Cl contents. The lowest limit of detection (0.75ng Cl, corresponding to 0.75µgg−1 for a typical sample mass of 1mg) could be achieved by combination of three of the most sensitive lines in the vicinity of 620.862nm, while the amplest linear range (up to 860ng Cl) was achieved by selection of the less sensitive line at 377.501nm.The method developed enabled the direct determination of Cl in solid samples using simple external calibration with aqueous standards. Good precision (5–9% RSD) and accuracy was attained in a series of certified samples of very different nature (i.e. coal, iron oxide, polyethylene, human hair, pine needles, rice flour and milk) and with very different Cl contents, ranging from about 50µgg−1 to 1% (w/w) Cl. The method appears as particularly useful for Cl determination in samples with elevated Ca contents, for which biased results with other diatomic molecules, such as AlCl or SrCl, may be obtained.