Multi-element Standard Solutions Research Articles

Analysis of Trace Impurities in Lithium Carbonate.

Lithium carbonate (Li2CO3) is a critical raw material in cathode material production, a core of Li-ion battery manufacturing. The quality of this material significantly influences its market value, with impurities potentially affecting Li-ion battery performance and longevity. While the importance of impurity analysis is acknowledged by suppliers and manufacturers of battery materials, reports on elemental analysis of trace impurities in Li2CO3 salt are scarce. This study aims to establish and validate an analytical methodology for detecting and quantifying trace impurities in Li2CO3 salt. Various analytical techniques, including X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma optical emission spectroscopy (ICP-OES), were employed to analyze synthetic and processed lithium salt. X-ray diffraction patterns of Li2CO3 were collected via step-scanning mode in the 5-80° 2θ range. SEM-EDX was utilized for particle morphology and quantitative impurity analysis, with samples localized on copper tape. XPS equipped with a hemispherical electron analyzer was employed to analyze the surface composition of the salt. For ICP-OES analysis, a known amount of lithium salt was subjected to acid digestion and dilution with ultrapure water. Multielemental standard solutions were prepared, including elements such as Al, Cd, Cu, Fe, Mn, Ni, Pb, Si, Zn, Ca, K, Mg, Na, and S. Results confirmed the presence of the zabuyelite phase in XRD analysis, corresponding to the natural form of lithium carbonate. SEM-EDX mapping revealed impurities of Si and Al, with low relative quantification values of 0.12% and 0.14%, respectively. XPS identified eight potential impurity elements, including S, Cr, Fe, Cl, F, Zn, Mg, and Na, alongside Li, O, and C. Regarding ICP-OES analysis, performance parameters such as linearity, limit of detection (LOD), and quantification (LOQ), variance, and recovery were evaluated for analytical validation. ICP-OES results demonstrated high linearity (>0.99), with LOD and LOQ values ranging from 0.001 to 0.800 ppm and 0.003 to 1.1 ppm, respectively, for different elements. The recovery rate exceeded 90%. In conclusion, the precision of the new ICP-OES methodology renders it suitable for identifying and characterizing Li2CO3 impurities. It can effectively complement solid-state techniques such as XRD, SEM-EDX, and XPS.

Quantification capabilities of N2 MICAP-MS with solution nebulization and aerosol desolvation.

The analytical capabilities of a nitrogen-sustained high-power microwave inductively coupled atmospheric-pressure plasma mass spectrometer (N2 MICAP-MS) were investigated using solution nebulization with and without aerosol desolvation. The reduced solvent load for the desolvated aerosol and the increased aerosol transfer resulted in a signal enhancement of ten times for most elements in samples without a significant amount of dissolved solids. An exception was boron, whose signal decreased by a factor of seven when a desolvator was used. To compare the accuracy, reproducibility, and matrix susceptibility of the N2 MICAP-MS, the mass fractions of 30 elements were determined in two certified water reference materials using external calibration and standard addition. The results were generally found to agree within 10% of the certified reference values with a maximum deviation of 17% in the case of 64Zn. Comparing external calibration and standard addition provided comparable results regardless of the sample introduction method. To assess the extent of matrix effects, multi-element standard solutions were doped with amounts of up to 100 mg kg-1 calcium. This resulted in a signal suppression of up to 30% and 70% for conventional nebulization and aerosol desolvation, respectively. This substantially reduced the improvement in sensitivity observed for the desolvated aerosol. To further investigate the fundamental characteristics of the N2 MICAP-MS, the plasma gas temperature was estimated using three methods. The determined temperatures for the two most reliable methods were in the range of ∼5000-6000 K and were found to be independent of the sample introduction method and similar to those of an Ar ICP.

Simultaneous Measurement of Trace Levels of Hg, As, Sb, and Bi in Coastal Seawater with a Multichannel Chemical Vapor Generation Atomic Fluorescence Spectrometer.

Trace levels of Hg, As, Sb, and Bi in coastal seawater have been simultaneously detected by a laboratory-built multichannel chemical vapor generation coupled to an atomic fluorescence spectrometer. The system was configured with a built-in electrochemical H2 generator as the fuel supplier to replace chemical H2 produced by the oxidation of potassium borohydride under acidic conditions in traditional instruments. The electrochemical H2 generator not only isolated the atomization process from the chemical vapor injection process but also improved the stability of atomization, excitation, and fluorescence emission in the hydrogen flame, making it easier to optimize conditions for CVG while introducing evaporating multielement vapors. Calibrations were obtained using a mixed standard solution of Hg(II), As(III), Sb(III), and Bi(III). The addition of KBr to a 3% (v/v) HCl solution was selected as the preservative to ensure the stability of 0.10 μg/L Hg(II) in a multielement standard solution for at least 15 days while also preserving μg/L levels of As(III), Sb(III), and Bi(III) stable. The method detection limits (LOD, 3σ) were 0.001, 0.015, 0.010, and 0.005 μg/L for Hg, As, Sb, and Bi, respectively. The relative standard deviations (RSD, n = 7) of the standard spiked seawater samples were 3.2% (0.020 μg/L Hg), 1.2% (0.50 μg/L As), 1.0% (0.50 μg/L Sb), and 3.5% (0.050 μg/L Bi), respectively. The recoveries of seawater samples spiked with different salinities were in the range of 84.5%(Sb)-114%(Hg). The system has been successfully applied to the simultaneous analysis of the four elements in the seawater samples collected from Xiamen Bay, Southeast China.

Biologically-induced synthetic manganese carbonate precipitate (BISMCP) for potential applications in heavy metal removal

Heavy metal pollution of water is a burning issue of today’s world. Among several strategies involved for heavy metal remediation purpose, biomineralization has shown great potential. Of late, research has been focused on developing effective mineral adsorbents with reduced time and cost consumption. In this present paper, the Biologically-Induced Synthetic Manganese Carbonate Precipitate (BISMCP) was produced based on the biologically-induced mineralization method, employing Sporosarcina pasteurii in aqueous solutions containing urea and MnCl2. The prepared adsorbent was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD) and BET surface area analyzer. EDX analysis showed the elements in the crystal BISMCP were Mn, C, and O. XRD result of BISMCP determined the crystal structure, which is close to rhodochrosite (MnCO3). Spectral peaks of FTIR at 1641.79 cm−1 confirmed the appearance of CO binding, with strong stretching of CO32− in Amide I. From the six kinds of BISMCP produced, sample MCP-6 has the higher specific surface area by BET analysis at 109.01 m2/g, with pore size at 8.76 nm and higher pore volume at 0.178 cm3/g. These specifications will be suitable as an adsorbent for heavy metal removal by adsorption process. This study presents a preliminary analysis of the possibility of BISMCP for heavy metals adsorption using ICP multi-element standard solution XIII (As, Cr, Cd, Cu, Ni, and Zn). BISMCP formed from 0.1 MnCl2 and 30 ml of bacteria volume (MCP-6) produced a better adsorbent material than others concentrations, with the adsorption efficiency of total As at 98.9%, Cr at 97.0%, Cu at 94.7%, Cd at 88.3%, Zn at 48.6%, and Ni at 29.5%. Future work could be examined its efficiency adsorbing individual heavy metals.

Lanthanoid analysis in seawater by seaFAST-SP3™ system in off-line mode and magnetic sector high-resolution inductively coupled plasma source mass spectrometer

Analysis of lanthanoids in seawater is challenging due to the complex matrix (∼35 g L−1 TDS) and low dissolved concentrations (in ng L−1). A 4-step strict analytical protocol and state-of-the-art technology were implemented and validated in this study. The 4-steps method involves the 1) sample filtration and acidification (pH<2); 2) pre-concentration by the matrix separation system, 3) off-line injection of the eluted sample; and 4) determination of lanthanoids by high-resolution inductively coupled plasma mass spectrometer (HR-ICP-MS). Since there are no certified values for lanthanoids in seawater are available, the method validation was done by analyzing SLEW-3 (estuarine water reference samples) and comparing with other reports and artificial seawater (100 ng L−1 lanthanoid multi-element standard solutions). SLEW-3 recovery varied from 78.6% to 106% and in artificial samples it ranged from 87 to 110%. Low recovery can be explained by complex organic in seawater, because the UV oxidation was not performed in the acidified samples. The variation was ≤10%, except for Gd, Tb, and Yb (11–13.75%). Blanks varied between 0.01 and 0.07 ng L−1, except for La and Ce (0.13–0.21 ng L−1). Blanks represent <5% SLEW-3 values and <1% synthetic seawater. The procedural detection limit varied from 0.01 to 0.03 ng L−1.•Lanthanoids as geochemical tracers in seawaters•A 4-step strict analytical protocol and state-of-the-art technology for lanthanoids analyses in seawaters•Sample pre-concentration system for matrix separation for the detection of ultra-low lanthanoids levels

Schiff base functionalized silica gel for simultaneous separation and preconcentration of Cu(II), Ni(II), and Cd(II) in pharmaceuticals and water samples

A method for separation and preconcentration of Cu(II), Ni(II), and Cd(II) using N-N'-bis(5-methoxsalicylidene)-2-hydroxy-1,3-propanediamine modified silica gel was improved for aqueous samples and pharmaceuticals. Determination of the analytes was achieved by inductively coupled plasma optic emission spectrometry. The experimental conditions including pH value, sample volume, eluent type and volume, sorbent mass, sample, and eluent flow rates were optimized with univariate and multivariate optimization tools. The relative standard deviations of the method were 2.9% for Cu(II), 3.0% for Ni(II), and 3.3% for Cd(II) with recovery values between 98.8 ± 3.2-101.5 ± 3.0%. The limits of detection were found to be 62.4, 39.5, and 28.2 ng L-1 for Cu(II), Ni(II), and Cd(II), respectively. The accuracy of the suggested procedure was tested with the certified reference material (Certipur ICP multi-element standard solution IV) and addition-recovery experiments. The method was successfully applied to eye drop, anesthetic, serum, tap water, mineral water, and spring water samples.

Experience in using high matrix introduction (HMI) technology for the analysis of lead by inductively coupled plasma mass-spectrometry (ICP-MS)

The impurities contained in lead and lead-based alloys, which are widely used in various branches of industry, i.e., nuclear, medical, electrical engineering, etc., affect their physicochemical properties which necessitates developing of the reliable method for the impurity determination. Photometric, spectral, and chemical — spectral methods used to address this problem are labor-intensive and do not always have the required sensitivity. A method of inductively coupled plasma mass spectrometry (ICP-MS) coupled with High Matrix Introduction (HMI) technology has been proposed as alternative easy to use procedure designed to be more sensitive. The Agilent HMI Sample Injection System provides inline dilution of the sample aerosol (supplied from the spray chamber to the burner) with pure argon. This method of sample introduction provides for analysis of the solutions with a solute content of up to 1% and higher. The aerosol dilution reduces concentration of the matrix and solvent at the inductively coupled plasma interface without conventional dilution. In this case, the matrix suppression of impurities is almost eliminated and CeO+/Ce+ is reduced to 0.2%, while the typical CeO+/Ce+ ratio for the Agilent 7500 mass spectrometers is 1 – 2%, but no more than 3%. We present application of this method to the analysis of Mg, Ca, Fe, Cu, As, Ag, Sn, Sb, Bi in lead by an Agilent 7500cx ICP-MS with preliminary acid digestion of lead samples in a microwave autoclave. The use of the HMI system made it possible to exclude the stage of sample dilution, reducing the possibility of sample contamination with a diluent, and to determine the content of impurities in a highly concentrated matrix at a level of 10–4 – 10–5 %. The efficiency of the method, as well as the possibility of using multi-element standard solutions prepared with 1% nitric acid for analysis of the samples with high lead content is shown.

The relatively higher concentrations of trace elements to arsenic may have influenced on methylation process of inorg- As in humans

The relatively higher concentrations of trace elements to arsenic may have influenced on methylation process of inorg- As in humans

Trace element levels in pleural effusions.

Trace element levels in pleural effusions.

Determination of impurities in copper metal using total reflection X‐ray fluorescence spectrometry after matrix separation: Method validation and uncertainty assessment

TXRF spectrometry has been utilized for the determination of impurities in copper metal. Multielement standard solution has been used for the calibration of TXRF spectrometer. To avoid the matrix effects, Cu was separated by electrochemical separation method under optimized condition followed by determination of impurities using TXRF. K, Ca, Fe, Ni, and Zn are the impurities found to be present in copper metal. Bottom up approach was employed to get the measure of the combined uncertainty in the results. The uncertainty associated with the recovery of electrochemical separation process is the highest. The TXRF results were validated by analyzing the same sample using ICP‐OES. Student's t‐test was performed to establish the statistical indistinguishability of the results obtained from TXRF and ICP‐OES.

Schiff base functionalized silica gel for simultaneous separation and preconcentration of Cu(II), Ni(II), and Cd(II) in pharmaceuticals and water samples.

A method for separation and preconcentration of Cu(II), Ni(II), and Cd(II) using N-N'-bis(5-methoxsalicylidene)-2-hydroxy-1,3-propanediamine modified silica gel was improved for aqueous samples and pharmaceuticals. Determination of the analytes was achieved by inductively coupled plasma optic emission spectrometry. The experimental conditions including pH value, sample volume, eluent type and volume, sorbent mass, sample, and eluent flow rates were optimized with univariate and multivariate optimization tools. The relative standard deviations of the method were 2.9% for Cu(II), 3.0% for Ni(II), and 3.3% for Cd(II) with recovery values between 98.8 ± 3.2-101.5 ± 3.0%. The limits of detection were found to be 62.4, 39.5, and 28.2 ng L-1 for Cu(II), Ni(II), and Cd(II), respectively. The accuracy of the suggested procedure was tested with the certified reference material (Certipur ICP multi-element standard solution IV) and addition-recovery experiments. The method was successfully applied to eye drop, anesthetic, serum, tap water, mineral water, and spring water samples.

Spatial distribution of agricultural yields with elevated metal concentration of the island exposed to acid mine drainage

An island province in the Philippines exposed to acid mine drainage for about 22-25 years, uncovered new discovery in selected agricultural yields. The acid mine drainage was from two open mine pits of higher elevation flowing to Boac and Mogpog River system. A total of 78 various agricultural yields samples with 234 specimens were collected and analyzed from six municipalities of Marinduque, Philippines in 2019. These agricultural yields were (A) vegetables, (B) root crops, (C) fruits, and (D) rice. Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES) Perkin Elmer Optima 8000 with ICP multi-element standard solution IV were used to detect metals concentration in the agricultural samples. Digestion of samples followed the EPA Method 200.3. Results were compared with the WHO/FAO limit followed by the identification of yields and areas that pose risks to public health. Determination of the spatial distribution was by ArcGIS. The six municipalities; i.e., Boac, Buenavista, Gasan, Mogpog, Torrijos and Sta. Cruz, were labelled as B, BV, G, M, T and S, respectively. Record showed that Sample A from G contain higher metal concentration among other yields. Manganese concentration in Samples A, B, and D were found to be higher than WHO/FAO limit. However, copper and zinc concentration in Sample C in all municipalities exceeded the allowable limit. Elevated total chromium concentration was found in Sample D collected from G, T, and S. These results would help relevant government agencies and units design strategies to mitigate the degraded agricultural lands and protect public health.

Methodology development and optimization for direct quantification of total selenium concentration in mine water by total-reflection X-ray fluorescence spectrometry

Methodology for direct quantification of total selenium (Se) concentration in mine water by total-reflection X-ray fluorescence (TXRF) spectrometry was developed and optimized. Inductively coupled plasma – mass spectrometry (ICP-MS), as a recognized standard test method, was used as a benchmark for results verification. Preliminary measurements with aqueous multi-element standard solutions showed that Se concentration can be accurately determined down to 10 ng/g by using a single-drop of solution (10 μL) and a measurement time of 600 s. Quantification of lower Se concentration below 10 ng/g was subsequently optimized, also with aqueous multi-element standard solutions. Improvement in detection limit was accomplished by increasing amount of sample deposition as well as increasing measurement time. TXRF analysis of SRM1640a, Trace Elements in Natural Water, was also performed for accuracy check. The developed methodology was applied to analyze five raw mine water samples (MW-1, MW-2, MW-3, MW-4 and MW-5) collected from anonymous mine site locations. TXRF analysis was performed on the as-received samples directly without filtration, dilution and digestion. Samples were prepared as single-drop specimens and analyzed using a measurement time of 600 s. Se and fifteen other elements were detected in varying degree in the as-received samples. Se concentrations quantified by TXRF were 256.5 ± 22.5, 88.4 ± 1.4 and 61.3 ± 2.8 ng/g for mine water samples MW-1, MW-2 and MW-3, respectively, compared to 255.3 ± 5.6, 87.3 ± 2.6 and 59.7 ± 3.5 ng/g by ICP-MS. No clear Se-Kα peak above background was observed for samples MW-4 and MW-5. Increasing amount of sample deposition by preparing triple-drop specimens and using a longer measurement time of 1800 s, allowed a Se-Kα peak to emerge above the background for MW-4, but not MW-5. Se concentration in MW-4 quantified by TXRF was 4.9 ± 0.5 ng/g, compared to 6.7 ± 0.7 ng/g by ICP-MS, which represents an agreement within three standard deviation values between the two techniques. For sample MW-5, even after using triple-drop specimens and increasing the measurement time to 1800 s, Se concentration could not be determined because a Se-Kα peak was not detected by TXRF, compared to the Se concentration of 0.83 ± 0.1 ng/g obtained by ICP-MS. Overall, our analysis results showed that the TXRF technique can be used for direct analysis of total Se concentration in raw mine water samples down to ng/g range, providing high-quality, accurate and repeatable analysis comparable to ICP-MS while requiring much simpler sample preparation.

Microwave acid digestion of mafic and ultramafic rocks in ICP-MS determination of the rare earth elements

A technique of the microwave digestion of mafic and ultramafic rocks is developed for ICP-MS determination of the rare earth elements. A series of experiments was carried out to optimize the digestion parameters (temperature, acid ratio, sample mass) in a microwave system MARS-5. A mixture of acids HF and HNO3 in a volume ratio of 4:1 was used at the first stage (60 min, 190°C, maximum pressure 20 atm), and after distilling off the excess fluorides in the form of SiF4 the dry residue was treated with aqua regia (60 min, 190°C, maximum pressure 20 atm). Measurements were carried out using a double-focusing ICP mass spectrometer ELEMENT Finnigan Mat. Multielement standard solution with an acidic composition similar to the analyzed solutions was used for external calibration and indium was used as an internal standard. The detection limits were 0.0002 – 0.008 μg/g. The digestion technique was validated by analysis of the geological reference materials BHVO-2 and BCR-2 (basalts), UB-N (serpentinite), JP-1 (peridotite). The relative standard deviations for the determined elements were below 8% for reference materials BHVO-2, BCR-2, and UB-N, and ranged within 10 – 35% for JP-1 sample. The developed technique was used for determination of the rare earth elements in Kola Peninsula rocks. The correctness of the results was confirmed by comparison with the results of ICP-MS analysis after fusion with lithium metaborate. The rapidity compared to acid decomposition without using a microwave system and low detection limits compared to fusion are the apparent advantages of the developed technique.

Universal EDXRF Method for Multi-elemental Determinations Using Fused Bead Specimens.

A systematic study on the EDXRF determination of multi-elements using fusion bead specimens and a universal calibration procedure was carried out. Beads of multi-elements were prepared by mixing MERCK multi-elemental standard solutions with the fusion flux. The elemental X-ray lines of K, Ca, Ba, Cr, Mn, Fe, Co, Ni, Cu and Zn were excited using a Ge secondary target and that of Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Pb, Bi and Sr using a Rh primary target. The relative sensitivities of the elemental X-ray lines obtained using different excitation modes were calculated using a single bead. Using this relative sensitivity, the concentration of elements in other bead samples was determined. The average precision obtained was 3% (1 s) and the average deviation from expected values, calculated on the basis of sample preparation, was 6%. In order to further countercheck the validity of this methodology, a standard soil sample received from IAEA was analyzed.

Investigation of the Levels of Heavy Metal in the Blood and Venous Blood and MicroRNA Levels in Women With Migraine

In this study, it is aimed to investigation of microRNA (let-7b, miR-21, miR-22, miR-27-b, miR-34a-5p, miR-126-5p, miR-155-5p and miR-382-5p) and heavy metal levels (Hg, Mn, Co, Ni, As, Cr, Pb, Ag, Se) at the same time in the cupping blood and venous blood in female migraine patients. RNAs isolated from plasma samples by using High Pure microRNA Isolation Kit. RNA samples converted to cDNA by using miScript II RT Kit. cDNA samples are PreAmplified by using miScript Microfluidics PreAMP Kit. qRT-PCR analysis performed by using miScript microRNA Assays with Dynamic Array 96.96 on BioMark System. An ELAN DRC-e inductively coupled plasma mass spectrometry (ICP-MS) system was used for the measurements of the levels of trace elements in serum and using an multielement standard solution for IV and ICP. The MARS microwave digestion system was employed for mineralisation of serum samples. Serum total cholesterol, triglycerides, high density lipoprotein cholesterol, LDL- cholesterol and blood glucose was measured by commertially available kits based on routine methods by the Abbott Architect C16000 auto-analyzer. The plasma miR-21 level of Group 2 was significantly higher than group 3 (p <0.05). Also, plasma miR-22 level of group 2 was found to be statistically significant when compared to group 3 (p <0.05).

Determination of uranium in immersion liquid of demolition waste using total reflection X-ray fluorescence analysis

In this study, we proposed a novel methodology based on total reflection X-ray fluorescence (TXRF) analysis for rapid evaluation of uranium radioactivity concentration in water samples, which will be found in the decommissioning field of Fukushima Daiichi Nuclear Power Plant containing various impurities. Sample solutions were prepared by mixing a multi-element standard solution containing uranium and thorium with an immersion liquid of the demolition debris in order to examine the effect of components of the demolition debris. An indium standard solution was added to the samples as an internal standard. Since the Rb Kα peak overlapped with the U Lα and Th Lα peaks, Gaussian fitting was performed to determine the net intensity of the U Lα peak. Moreover, due to the largely different contents of uranium and rubidium, reducing the number of fitting parameter made the Gaussian fitting easier. To determine the widths of the peaks, long-time TXRF measurement of the standard solutions for each element was performed. In the Gaussian fitting, only the peak intensities were considered as fitting parameters because the peak widths and peak energies could be fixed. The relative intensity of the U Lα peak was calculated as the net intensity of the U Lα peak normalized by that of the In Kα peak. The relative intensity was directly proportional to the uranium concentration. The estimated minimum detection limit of uranium with a measurement time of 15 min was significantly lower than the effluent standard value for uranium concentration in drainage water as defined by the Japanese Water Pollution Prevention Law, 20 mBq/cm3. All in all, we believe that this method will be useful in determining the uranium concentration in drainage water in the decommissioning field of Fukushima Daiichi Nuclear Power Plant.

Evaluation of total-reflection X-ray fluorescence measurements for the prospective determination of uranium in the decommissioning of the Fukushima Daiichi Nuclear Power Plant reactor

Owing to the strong earthquake and subsequent tsunami in March 2011, the Fukushima Daiichi Nuclear Power Plant was exceedingly damaged and is currently under decommissioning. Herein, we propose a methodology to evaluate the uranium concentration in the drainage water from the decommissioning field. Model sample solutions were prepared by mixing multi-element standard solutions containing uranium with an immersion liquid containing demolition debris. A very small amount (10 μL) of the sample solutions was dropped onto a quartz optical flat directory with or without a chromatography resin separation. The total-reflection X-ray fluorescence (TXRF) spectrometry measurement was performed using a portable device. These measurements showed an overlap of the Rb Kα and U Lα peaks in the TXRF spectrum of the sample solution prepared without chromatography resin separation. By contrast, no overlap was observed in the TXRF spectrum of the sample solution after the separation using a chromatography resin. When the drainage water is composed of 0.04% U-234, 5% U-235, and 94.96% U-238, the measurement times in both methods (i.e., with and without pretreatment) required to attain detection limits lower than the effluent standard value are 15 and 5 min, respectively. Additionally, the detection limits, analysis times, required sample volumes, and procedures of the two methods are compared.

Preparation and purification of organic samples for selenium isotope studies.

Selenium (Se) is an important micronutrient but also a strong toxin with a narrow tolerance range for many organisms. As such, a globally heterogeneous Se distribution in soils is responsible for various disease patterns (i.e. Se excess and deficiency) and environmental problems, whereby plants play a key role for the Se entrance into the biosphere. Selenium isotope variations were proved to be a powerful tracer for redox processes and are therefore promising for the exploration of the species dependent Se metabolism in plants and the Se cycling within the Critical Zone. Plant cultivation setups enable systematic controlled investigations, but samples derived from them–plant tissue and phytoagar–are particularly challenging and require specific preparation and purification steps to ensure precise and valid Se isotope analytics performed with HG-MC-ICP-MS. In this study, different methods for the entire process from solid tissue preparation to Se isotope measurements were tested, optimized and validated. A particular microwave digestion procedure for plant tissue and a vacuum filtration method for phytoagar led to full Se recoveries, whereby unfavorable organic residues were reduced to a minimum. Three purification methods predominantly described in the literature were systematically tested with pure Se solution, high concentrated multi-element standard solution as well as plant and phytoagar as target matrices. All these methods efficiently remove critical matrix elements, but differ in Se recovery and organic residues. Validation tests doping Se-free plant material and phytoagar with a reference material of known Se isotope composition revealed the high impact of organic residues on the accuracy of MC-ICP-MS measurements. Only the purification method with no detectable organic residues, hydride generation and trapping, results in valid mass bias correction for plant samples with an average deviation to true δ82/76Se values of 0.2 ‰ and a reproducibility (2 SD) of ± 0.2 ‰. For phytoagar this test yields a higher deviation of 1.1 ‰ from the true value and a 2 SD of ± 0.1 ‰. The application of the developed methods to cultivated plants shows sufficient accuracy and precision and is a promising approach to resolve plant internal Se isotope fractionations, for which respective δ82/76Se values of +2.3 to +3.5 ‰ for selenate and +1.2 to +1.9 ‰ for selenite were obtained.

Sequential coprecipitation and matrix removal for determination of cadmium impurities from multivitamin supplements by inductively coupled plasma mass spectrometry and method validation by isotope dilution analysis of SRM 3280 multivitamin/multielement tablets

In this paper, we examined three different sequential coprecipitation schemes based on Mg(OH)2 and CaF2 precipitation using triethylamine (TEA) and hydrofluoric acid (HF), respectively, for determination of cadmium (Cd) impurities from multivitamin/mineral (MVM) supplements by isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS). The schemes involved three-step coprecipitation with either TEA alone or in combination with HF and are designated as Scheme 1 (TEA-TEA-TEA), Scheme 2 (TEA-HF-TEA) and Scheme 3 (HF-TEA-TEA) according to the addition sequence of each reagent. Experiments were carried out with MVM solutions spiked with 60μgL−1 Cd from a multielement standard solution. All schemes provided quantitative separation of Cd from MVM matrix. Scheme 1 was the least effective in removal of interfering concomitant elements, molybdenum (Mo) and tin (Sn). Scheme 2 performed better for Sn, but failed in eliminating Mo. Scheme 3 was the most effective in eliminating both Mo and Sn. Mo levels in test MVM solutions reduced from 4.3μgmL−1 to as low as 0.014μgmL−1 while that for Sn decreased from 0.5μgmL−1 to 0.018μgmL−1 allowing interference-free determination of Cd to be achieved. Salt-matrix due to Mg, Ca, P and K along with the essential elements (Mn, Fe, Cu and Zn) levels was also reduced significantly. Reagent blanks from HF and TEA were insignificant (0.008μgL−1) allowing a limit of detection of 0.004μgL−1 or 0.26ngg−1 Cd to be achieved (3σ, n=6). The performance of the coprecipitation method (Scheme 3) was validated by determination of Cd in multivitamin/multielement tablets certified reference material (SRM 3280) by ID-ICP-MS. Experimental results (ngg−1) and recoveries were 78.8±4.7 (98.5%), 77.9±5.2 (97.4%) and 76.5±4.8 (95.6%) for 110Cd, 111Cd and 114Cd isotopes, respectively. Several commercial MVM supplements were analyzed using the method. Mean Cd concentration ranged from 21.4ngg−1 to 93.3ngg−1. These values are much lower than those reported to date for various MVM supplements by ICP-MS determinations without chemical separation.