Application of ICP-MS,INAA and RNAA to the determination of some “difficult” elements in infant formulas

In this work a determination of selected elements in the infant formulas commercially available on the Polish market was done. 14 different materials (milk-based formulas and grain porridges) were analyzed. Both, inductively coupled plasma mass spectrometry (ICP-MS) and instrumental neutron activation analysis (INAA) were applied for the determination of As, Cr, Fe and Se, which are recognized as the problematic elements for ICP-MS. For As and Se, the radiochemical NAA was also used. The daily intake of Se and Fe in the age 0–6 months for non-breast fed infants was estimated and compared with present safety limits.

     

Slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of As and Se in soil and sludge

Slurry sampling electrothermal vaporization (ETV) inductively coupled plasma mass spectrometry (ICP-MS) has been applied to determine As and Se in soil and sludge samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Pd and ascorbic acid were used as mixed modifiers to enhance the ion signals. The effectiveness of ETV sample introduction technique for alleviating various spectral interferences in ICP-MS analysis has been demonstrated. This method has been applied to determine As and Se in NIST SRM 2709 San Joaquin soil reference material and NIST SRM 2781 domestic sludge reference material and a farmland soil sample collected locally. Since the sensitivities of As and Se in slurry solution and aqueous solution were different, analyte addition technique was used to determine As and Se in these samples. The As and Se analysis results of the reference materials agreed with the certified values. The precision between sample replicates was better than 5% for all determinations. The method detection limit estimated from analyte addition curves was about 0.03 and 0.02 μg g⁻¹ for As and Se, respectively, in original soil and sludge samples.     

Application of tertiary amines for arsenic and selenium signal enhancement and polyatomic interference reduction in ICP-MS analysis of biological samples

Water soluble tertiary amines enhance signals and decrease polyatomic chloride interferences in the direct inductively coupled plasma – mass spectrometric (ICP-MS) determination of As and Se in biological samples. Preliminary experiments with amine concentrations and nebulizer flow rates produced element and interference signal intensity changes. Arsenic and Se ICP-MS determination parameters have been optimized by a simplex procedure with amines in an argon plasma or without amines but with addition of N₂ to the Ar. Variables include RF (radio frequency) power, nebulizer gas flow rate, intermediate gas flow rate, and amine concentration or nitrogen gas flow rate. Detection limit, minimization of polyatomic ion intensities, and reproducibility have been evaluated as reponse factors. The signal enhancement and element-to-molecular interference ratios differ to some extent with analyte intensity optimum operating conditions. The detection limits with addition of nitrogen (16 pg mL^–1 for As and 180 pg mL^–1 for Se) or of amines (8 pg mL^–1 for As and 120 pg mL^–1 for Se) and the extent of chloride interference minimization were compared. Amines addition was more beneficial. Biological standard reference materials and food and fecal samples were analyzed following different sample dissolution procedures.     

Application of tertiary amines for arsenic and selenium signal enhancement and polyatomic interference reduction in ICP-MS analysis of biological samples

Water soluble tertiary amines enhance signals and decrease polyatomic chloride interferences in the direct inductively coupled plasma – mass spectrometric (ICP-MS) determination of As and Se in biological samples. Preliminary experiments with amine concentrations and nebulizer flow rates produced element and interference signal intensity changes. Arsenic and Se ICP-MS determination parameters have been optimized by a simplex procedure with amines in an argon plasma or without amines but with addition of N₂ to the Ar. Variables include RF (radio frequency) power, nebulizer gas flow rate, intermediate gas flow rate, and amine concentration or nitrogen gas flow rate. Detection limit, minimization of polyatomic ion intensities, and reproducibility have been evaluated as reponse factors. The signal enhancement and element-to-molecular interference ratios differ to some extent with analyte intensity optimum operating conditions. The detection limits with addition of nitrogen (16 pg mL^–1 for As and 180 pg mL^–1 for Se) or of amines (8 pg mL^–1 for As and 120 pg mL^–1 for Se) and the extent of chloride interference minimization were compared. Amines addition was more beneficial. Biological standard reference materials and food and fecal samples were analyzed following different sample dissolution procedures.     

Sensitivities of selenite, selenate, selenomethionine and trimethylselenonium ion in aqueous solution and in blood plasma-ETAAS compared with ICP-MS

Aqueous solutions and blood plasma spiked with selenite (Se(IV)), selenate (Se(VI)), selenomethionine (SeMet) or trimethylselenonium (TMSe) iodide were analyzed by Zeeman-corrected electrothermal atomic absorption spectrometry (ETAAS) using palladium as a chemical modifier, and by inductively coupled plasma mass spectrometry (ICP-MS). Using ETAAS, the sensitivities for Se(IV), SeMet and TMSe in aqueous solution were similar, whereas the sensitivity of Se(VI) was 63% of that value. In blood plasma, the ETAAS sensitivities of Se(IV) and Se(VI) were equal, whereas the sensitivities of SeMet and TMSe were 87 and 56%, respectively, of that value. In contrast, the ICP-MS sensitivities obtained for Se(VI), TMSe and SeMet were between 96 and 98% of that obtained for Se(IV) in aqueous solution and in blood plasma. It is concluded, that ICP-MS is superior to ETAAS as the problem of differences in sensitivity of the selenium species when using ETAAS are not prevalent when using the ICP-MS technique.     

Determination of different oxidation states of arsenic and selenium by inductively coupled plasma-atomic emission spectrometry with ion chromatography

Recent regulation in Japan requires more sensitive trace analysis methods for the determination of arsenic and selenium and their oxidation states As(III) and (V), Se(IV) and (VI). The hydride generation (HG) technique is usually used in combination with AAS and ICP-AES to increase sensitivity. However, hydrochloric acid is mostly used to acidify the sample solution in HG. Isobaric interferences due to chlorine-related species cause mass spectral problems when the same solution is used for the determination of these elements by ICP-MS. In this study, different oxidation states of As and Se were determined by coupling ion chromatography (IC) to an ICP-AES instrument. An HG technique was used to introduce test samples into the ICP. Nitric acid was employed to acidify the samples for HG. The concentrations of acid and base were kept as low as possible to reduce contamination. The formation of As and Se hydrides could be achieved without HCl, if the concentrations of acid and alkaline solutions were optimized. However, HCl was necessary for additional reduction of Se(VI) to Se(IV).     

Determination of different oxidation states of arsenic and selenium by inductively coupled plasma-atomic emission spectrometry with ion chromatography

Recent regulation in Japan requires more sensitive trace analysis methods for the determination of arsenic and selenium and their oxidation states As(III) and (V), Se(IV) and (VI). The hydride generation (HG) technique is usually used in combination with AAS and ICP-AES to increase sensitivity. However, hydrochloric acid is mostly used to acidify the sample solution in HG. Isobaric interferences due to chlorine-related species cause mass spectral problems when the same solution is used for the determination of these elements by ICP-MS. In this study, different oxidation states of As and Se were determined by coupling ion chromatography (IC) to an ICP-AES instrument. An HG technique was used to introduce test samples into the ICP. Nitric acid was employed to acidify the samples for HG. The concentrations of acid and base were kept as low as possible to reduce contamination. The formation of As and Se hydrides could be achieved without HCl, if the concentrations of acid and alkaline solutions were optimized. However, HCl was necessary for additional reduction of Se(VI) to Se(IV).     

高效液相色谱-等离子体质谱联用方法研究富硒大米中硒的形态

根据Osborne溶解性蛋白质分类法,用去离子水、2%NaCl溶液、70%乙醇、0.5%KOH4种溶液分别提取出大米中相应的清蛋白、球蛋白、醇溶蛋白及谷蛋白。利用电感耦合等离子质谱(ICP-MS)测量各类蛋白提取液中的硒含量;用色谱与质谱联用法对大米蛋白提取液中含硒蛋白组分及含硒氨基酸组成进行初步分析。结果表明:大米中的硒主要与蛋白质结合,在4类蛋白提取液中硒含量由高到低的分布顺序为:谷蛋白、醇溶蛋白、清蛋白和球蛋白。清蛋白提取液中,分子量为12.6 kDa蛋白是主要的含硒蛋白组分;大米中约30%的硒以硒代半胱氨酸形式存在。     

Multi-element determination in earthworms with instrumental neutron activation analysis and inductively coupled plasma mass spectrometry: A comparison

Earthworms were collected from agricultural fields in Admont, Graz, Piber and Gumpenstein, Austria. Six earthworm samples were investigated with INAA and with ICP-MS in parallel for the element concentrations of As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Pb, Rb, Sb, Se and Zn. With both techniques 14 elements were analysed in a wide concentration range (ng/g to mg/g) GF-AAS and HG-AAS were used for verification of some element concentrations. A comparison of analytical results between INAA and ICP-MS was discussed. In general, good agreement between ICP-MS and INAA was obtained, the relative difference values of most of the elements are within ±20% range, however, a methodical error for the determination of Hg by ICP-MS was found.     

HPLC-ICP-MS或HPLC-FAAS法分离测定硒化合物（英文）

 提出了一种用高效液相色谱（HPLC）分离和用电感偶合等离子体质谱仪（ICP－MS）或火焰原子吸收光谱仪（FAAS）作元素专一检测器在线测定硒的化学形态的方法。在优化的HPLC条件下,用ESAⅢ阴离子色谱柱（250mm×4．6mm）,以柠檬酸铵为流动相（5．5mmol／L,pH5．5,流速1．5mL／min）,进样量100μL,分离和测定三甲基硒离子、硒代蛋氨酸、亚硒酸和硒酸盐只需8min。HPLC－FAAS在线分析4种硒化合物的检测限为p（Se）=1mg／L。     

Selenium speciation analysis in a sediment using strong anion exchange and reversed phase chromatography coupled with inductively coupled plasma-mass spectrometry

An analytical procedure for selenium speciation of analysis of selenourea (SeU), selenoethionine (SeE), selenomethionine (SeM), Se(VI), Se(IV), dimethylselenide (dMeSe) and dimethyldiselenide (dMedSe) was developed, based on two complementary liquid chromatography (LC) techniques coupled with inductively coupled plasma-mass spectrometry (ICP-MS). Specifically, strong anion exchange (SAX) chromatography coupled with ICP-MS was used for the separation and quantification of all the earlier mentioned Se compounds, except for the two methyl selenides, which could be separated and determined by reversed phase chromatography coupled with ICP-MS. This procedure was applied to a soil sample from the warm springs area of Thermopyles (Greece). For leaching the Se species from the soil sample, four extraction methods, using water at ambient temperature, hot water, methanol and 0.5 M HCl, were tested for their efficiency of extracting the different Se species. The speciation results obtained by the LC-ICP-MS methods were compared with those obtained by voltammetric techniques. The determination of total selenium in the sample was achieved by graphite furnace atomic absorption spectrometry, as well as by ICP-atomic emission spectrometry, after suitable digestion of the sediment sample.     

Rapid and simple determination of selenium in blood serum by inductively coupled plasma–mass spectrometry (ICP–MS)

An inductively coupled plasma mass spectrometer (ICP-MS) with a rapid sample-preparative procedure was used for the determination of selenium in blood serum. Blood serum was prepared by dilution in an acidic solution consisting of nitric acid (1%), X-triton (0.1%) and 1-butanol (0.8%). A calibration curve was established for 1-40 microg mL(-1) (r(2)>0.99). The limit of detection was 0.5 microg mL(-1). Repeatability and intermediate precision were satisfactory with relative standard deviations (RSD) of 2.0% and 3.2%, respectively. This method was easily applied to reference materials with satisfactory accuracy. Good correlation (r(2)=0.96) was observed between ICP-MS and atomic absorption spectrometry (AAS) for the determination of (82)Se in blood serum from 23 patients. These results suggest that the sample preparative procedure coupled with ICP-MS can be used for the routine determination of (82)Se in human blood serum.     

Simultaneous determination of arsenic, selenium and antimony species using HPLC/ICP-MS

A new method for the simultaneous separation and determination of four arsenic species [As(III), As(V), monomethylarsonic acid and dimethylarsinic acid], three selenium species [Se(IV), Se(VI) and selenomethionine] as well as Sb(III) and Sb(V) is presented. The speciation was achieved by on-line coupling of anion exchange high-performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS). Chromatographic parameters such as the composition and pH of the mobile phase were optimised. Limits of detection are below 4.5 μg L^–1 (as element) for Sb(III) and the selenium species and below 0.5 μg L^–1 for the other species. Precisions of retention times were better than 2% RSD and of peak areas better than 8% RSD for all the species investigated.     

Determination of arsenic, selenium, and antimony in cloud water by inductively coupled plasma mass spectrometry

The capability of inductively coupled plasma mass spectrometry in determining trace levels of As, Se, and Sb in cloud water was evaluated. Preliminary studies focused on identifying and eliminating potential interferences in the cloud water matrix, the choice of appropriate internal standards, and system optimization. The detection limits for As, Se, and Sb were 20, 100, 20 pg/mL using pneumatic nebulization, and 5, 25, 5 pg/mL, respectively, using ultrasonic nebulization with a precision of better than 5% RSD. The accuracy was demonstrated by the analysis of a NIST commercial reference material, SRM 1643d. In all cases, the results from ICP-MS analysis agreed within 4% of the certified values. Comparative analysis of cloud water samples obtained from a site downwind from large pollution sources (Whiteface Mountain, New York) and Changlagali Pakistan, a rural mountain peak, was carried out by hydride generation atomic absorption (HGAA) spectrometry. There was excellent agreement between the ICP-MS and HGAA results.     

Use of granulated modified zeolite Y for the removal of inorganic arsenic and selenium species

Column studies were performed to evaluate the performance of modified zeolite-Y with ion Fe (zeolite-FeY) in removing As(III), As(V), Se(IV) and Se(VI) from groundwater. The removal capacities for zeolite-FeY was carried out on arsenic and selenium species in aqueous solution by co-precipitation technique with DBDTC-Pp complex in the pH range of 1.5–2.5 followed by the neutron activation analysis (NAA) using a TRIGA-MkII reactor with an average flux of 2.1 × 10¹² neutrons cm⁻² s⁻¹ and inductively coupled plasma-mass spectrometry (ICP-MS) technique as comparison. The accuracy between the results obtained from both techniques were compared and evaluated.     

Trace element analysis of turkey vulture (Cathartes aura) feathers

Ten feather samples, including primary and secondary flight and tail feathers, were analysed for the trace element composition of vane and rachis structures using instrumental neutron activation analysis (INAA), inductively coupled plasma-mass spectrometry (ICP-MS), and cold vapour atomic absorption spectroscopy (CVAAS). Five environmentally significant elements, Cr, As, Se, Sb and Hg, were analysed by INAA and ICP-MS/CVAAS. A further seventeen elements were analysed by ICP-MS. The majority data obtained by INAA and ICP-MS/CVAAS were not statistically significantly different (p = 0.05), although the removal of isobaric interferences using dynamic reaction cell technology was essential to produce ICP-MS data that were consistent with INAA for Cr, As and Se. Significantly higher trace element concentrations were observed for vane relative to rachis for all elements, except Cu and Hg. These elements displayed vane/rachis ratios of 0.7 ± 0.2 and 1.0 ± 0.2, respectively. In general, vane and rachis subgroups afforded data that were consistent with a normal distribution, with RSDs in the range (12–83) % for INAA analyses. A total of 18 outliers were noted amongst the various feather, structure, element combinations, with 14 outliers being observed in the vane and/or rachis structures of the same tail feather. Given the significant differences in vane and rachis concentrations observed for many elements, the large RSDs reported for elements and the potential for outliers, the determination of environmental trace element burden using feathers is significantly enhanced by the analysis of multiple feathers using INAA.     

Sequential photocatalyst-assisted digestion and vapor generation device coupled with anion exchange chromatography and inductively coupled plasma mass spectrometry for speciation analysis of selenium species in biological samples

We have developed an on-line sequential photocatalyst-assisted digestion and vaporization device (SPADVD), which operates through the nano-TiO₂-catalyzed photo-oxidation and reduction of selenium (Se) species, for coupling between anion exchange chromatography (LC) and inductively coupled plasma mass spectrometry (ICP-MS) systems to provide a simple and sensitive hyphenated method for the speciation analysis of Se species without the need for conventional chemical digestion and vaporization techniques. Because our proposed on-line SPADVD allows both organic and inorganic Se species in the column effluent to be converted on-line into volatile Se products, which are then measured directly through ICP-MS, the complexity of the procedure and the probability of contamination arising from the use of additional chemicals are both low. Under the optimized conditions for SPADVD – using 1 g of nano-TiO₂ per liter, at pH 3, and illuminating for 80 s – we found that Se(IV), Se(VI), and selenomethionine (SeMet) were all converted quantitatively into volatile Se products. In addition, because the digestion and vaporization efficiencies of all the tested selenicals were improved when using our proposed on-line LC/SPADVD/ICP-MS system, the detection limits for Se(IV), Se(VI), and SeMet were all in the nanogram-per-liter range (based on 3σ). A series of validation experiments – analysis of neat and spiked extracted samples – indicated that our proposed methods could be applied satisfactorily to the speciation analysis of organic and inorganic Se species in the extracts of Se-enriched supplements.     

Determination of Ga, Ge, As, Se and Sb in fly ash samples by ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry

Ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS) has been applied to determine Ga, Ge, As, Se and Sb in fly ash samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Pd and ascorbic acid were used as the mixed modifiers to enhance the ion signals. This method has been applied to determine Ga, Ge, As, Se and Sb in NIST SRM 1633a and 1633b coal fly ash reference materials and a fly ash sample collected locally. Since the sensitivities of the elements studied in slurry solution and aqueous solution were different slightly, analyte addition technique was used for the determination of Ga, Ge, As, Se and Sb in these samples. The As and Se analysis results of the reference materials agreed with the certified values. The results for which no certified value was available were also found to be in good agreement between the ETV-ICP-MS results and the reference values. The reference value was obtained by digesting the samples and analyzing the digested sample solutions by pneumatic nebulization Dynamic Reaction Cell™ (DRC) ICP-MS. The method detection limits estimated from analyte addition curves were about 0.23, 0.13, 0.17, 0.25 and 0.11 μg g⁻¹ for Ga, Ge, As, Se and Sb, respectively, in original fly ash samples.     

Reduction of polyatomic interferences in biological material using dynamic reaction cell ICP-MS

An analytical method is described for the routine quantification of five elements (As, Cr, Fe, Ni, and Se) in plants and animal feedstuffs using dynamic reaction cell inductively coupled plasma mass spectrometry (ICP-DRC-MS) after microwave digestion. Methane (for Cr, Fe, Ni, and Se) and oxygen (for As) were used as reaction gases to reduce polyatomic interferences. Optimization of the gas flow rate and the quadrupole dynamic bandpass tuning parameter (RPq) was carried out for the method. Detection limits (LOD) were in the range of 0.03–0.65 µg L^? 1 and were significantly lower compared to the standard mode without DRC. The trueness of the method was tested using three reference materials from Round robin tests. Results were well in accordance with the certified values. Furthermore, DRC data were examined by analyzing the same samples using sector field ICP-MS (SF-ICP-MS) and an ICP-MS equipped with collision cell technology (ICP-CCT-MS). The data obtained were in the confidence range of the reference material, too. The investigated method was applied for the analysis of grass and corn silage samples.     

Optimisation and assessment of an innovative high sensitivity 90-degree reflecting ICP-MS ion optics system for the validation of simultaneous determination of arsenic and selenium in water matrices

A routine ICP-MS method for the determination of As and Se in fresh and sewage water has been developed. After a first phase of optimisation, where the torch alignment, flow of gases and ion optic adjustments were calibrated, the method was validated successfully. The parameters limits of detection, linearity, working range, sensitivity and the interferences, precision and accuracy were studied with three procedures for the method: measuring two SRMs (BCR-714 of influent wastewater and NIST 1643e of groundwater); spiking four different matrices at three levels of concentration; and doing a proficiency test. The limits of detection obtained were 0.2 and 0.8?µg?L^?1 for As and Se, respectively. The percentages of linearity obtained were 99.2% for As and 99.8% for Se. All recovery values were according to the AOAC intervals, from 95.3% for As in the wastewater matrix to 106.4% for Se in the seawater matrix. The accuracy was also studied determined via a proficiency testing resulting in acceptable Z-scores of 0.65 and 0.4 respectively for As and Se. The complete method allowed analysis of water samples according to European Directive 2000/60 EC and the different guides for method validation.