Determination of237Np in environmental samples using inductively coupled plasma mass spectrometry

Ammonium uranates (AU) obtained by the addition of aqueous NH₄ OH to a solution of UO₂ (NO₃)₂ or the equilibrium reaction of UO₃ · 2H₂ O with the vapour over concentrated NH₄ OH have been studied by X-ray diffraction (XRD) analysis, diffuse reflectance Fourier transform infrared spectrometry (DR-FTIR) and chemical analysis. Ammonia can be present as either NH₃ or NH ₄ ⁺ . For precipitates obtained at a pH of 3.7, ammonia in the form of NH₃ is predominant. For ammonium uranate obtained by reaction over concentrated NH₄OH, most of the ammonia is bonded as NH ₄ ⁺ . The reaction mechanism and structures of the products are also discussed.     

Radionuclide determination in environmental samples by inductively coupled plasma mass spectrometry

The determination of naturally occurring and anthropogenic radionuclides in the environment by inductively coupled plasma mass spectrometry has gained recognition over the last fifteen years, relative to radiometric techniques, as the result of improvement in instrumental performance, sample introduction equipment, and sample preparation. With the increase in instrumental sensitivity, it is now possible to measure ultratrace levels (fg range) of many radioisotopes, including those with half-lives between 1 and 1000 years, without requiring very complex sample pre-concentration schemes. However, the identification and quantification of radioisotopes in environmental matrices is still hampered by a variety of analytical issues such as spectral (both atomic and molecular ions) and non-spectral (matrix effect) interferences and instrumental limitations (e.g., abundance sensitivity).The scope of this review is to highlight recent analytical progress and issues associated with the determination of radionuclides by inductively coupled plasma mass spectrometry. The impact of interferences, instrumental limitations (e.g., degree of ionization, abundance sensitivity, detection limits) and low sample-to-plasma transfer efficiency on the measurement of radionuclides by inductively coupled plasma mass spectrometry will be described. Solutions that overcome these issues will be discussed, highlighting their pros and cons and assessing their impact on the measurement of environmental radioactivity. Among the solutions proposed, mass and chemical resolution through the use of sector-field instruments and chemical reactions/collisions in a pressurized cell, respectively, will be described. Other methods, such as unique sample introduction equipment (e.g., laser ablation, electrothermal vaporisation, high efficiency nebulization) and instrumental modifications/optimizations (e.g., instrumental vacuum, radiofrequency power, guard electrode) that improve sensitivity and performance will also be examined.     

Determination of technetium-99 in aqueous samples by isotope dilution inductively coupled plasma-mass spectrometry

An isotope dilution/inductively coupled plasma mass spectrometric method (ID/ICP-MS) for measuring the concentration of technetium-99 in aqueous samples was developed at the Savannah River Technology Center (SRTC). The procedure is faster than radiometric tecniques, is less subject to interferences, and has equal or better detection limits. It is currently being used to measure the concentration of⁹⁹Tc in samples of Savannah River water collected in the vicinity of the Savannah River Site. In this method one liter samples of water are spiked with⁹⁷Tc. After equilibration, the technetium is extracted from the sample with a chromatographic resin. Interfering elements, molybdenum and ruthenium, are either not retained by the resin or are washed off with, dilute nitric acid. The technetium is then eluted with more concentrated nitric acid, and the⁹⁹Tc/⁹⁷Tc ratio in the eluant is measured with an ICP-MS. The⁹⁹Tc concentration in the original sample is calculated from the⁹⁹Tc/⁹⁷Tc ratio. The chemical recovery of the extraction procedure is greater than 90%. The detection limit of the instrument, taken as three times the background counts atm/z=99, is 0.6 part per trillion (ppt). The detection limit of the procedure, taken as three times the standard deviation of several reagent blank analyses, is 0.33 pCi/l.     

Determination of 237Np and Pu isotopes in large soil samples by inductively coupled plasma mass spectrometry

A new method for the determination of (237)Np and Pu isotopes in large soil samples has been developed that provides enhanced uranium removal to facilitate assay by inductively coupled plasma mass spectrometry (ICP-MS). This method allows rapid preconcentration and separation of plutonium and neptunium in large soil samples for the measurement of (237)Np and Pu isotopes by ICP-MS. (238)U can interfere with (239)Pu measurement by ICP-MS as (238)UH(+) mass overlap and (237)Np via (238)U peak tailing. The method provides enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then transferring Pu to DGA resin for additional purification. The decontamination factor for removal of uranium from plutonium for this method is greater than 1×10(6). Alpha spectrometry can also be applied so that the shorter-lived (238)Pu isotope can be measured successfully. (239) Pu, (242)Pu and (237)Np were measured by ICP-MS, while (236)Pu and (238)Pu were measured by alpha spectrometry.     

Determination of 99Tc in bentonite clay samples using inductively coupled plasma mass spectrometry

A method was developed for the determination of ⁹⁹Tc at low concentrations in clay samples. The chemical treatment of the samples prior to chemical separation and analysis comprised leaching with sulphuric acid/ sodium bromate. After leaching, pertechnetate was extracted with Alamine-336/chloroform and then back-extracted into nitric acid. Detection was carried out using inductively coupled plasma mass spectrometry, ICP-MS. The instrumental detection limit was 0.45 pg/mL, which corresponds to 0.28 mBq/mL. With the use of a desolvating nebuliser, the detection limit was lowered by about a factor of five. The results were compared with a method using radiometric detection.     

Determination of 99Tc in bentonite clay samples using inductively coupled plasma mass spectrometry

A method was developed for the determination of ⁹⁹Tc at low concentrations in clay samples. The chemical treatment of the samples prior to chemical separation and analysis comprised leaching with sulphuric acid/ sodium bromate. After leaching, pertechnetate was extracted with Alamine-336/chloroform and then back-extracted into nitric acid. Detection was carried out using inductively coupled plasma mass spectrometry, ICP-MS. The instrumental detection limit was 0.45 pg/mL, which corresponds to 0.28 mBq/mL. With the use of a desolvating nebuliser, the detection limit was lowered by about a factor of five. The results were compared with a method using radiometric detection. Received: 16 April 1998 / Revised: 12 June 1998 / Accepted: 16 June 1998     

Determination of226Ra in environmental samples using high-resolution inductively coupled plasma mass spectrometry

A time-saving and accurate technique for determining²²⁶Ra in groundwater and soil was examined, using high-resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS). The technique was applied to the determination of²²⁶Ra in groundwater and soil samples and compared with the conventional liquid scintillation counting method. This technique was capable of completing²²⁶Ra counting within 3 minutes, without the in-growth period to allow radon and its progeny to achieve secular equilibrium with the parent²²⁶Ra. The detection limits of HR-ICP-MS for²²⁶Ra in groundwater and soil were 0.19 mBq·1⁻¹ and 0.75 Bq·kg⁻¹, respectively, which were about 10 times lower than that of the liquid scintillation counter. The results obtained from HR-ICP-MS in groundwater and soil were in accordance with those of LSC within a relative error of about 13%.     

电感耦合等离子体质谱测定地质样品中多种元素

用电感耦合等离子体质谱(ICP-MS)测定了地质样品中多种元素。考察了测量过程中的基体效应及质谱干扰,利用In内标,补偿由于基体效应的影响所引起的测量偏差,建立校正公式校正质谱干扰。方法的检出限为0.06~250ng/L,精密度为1.7%~3.2%,加标回收率为91%~108%,方法适于批量地质样品分析。     

Determination of lithium in biological samples by inductively coupled plasma mass spectrometry

Lithium was determined in human serum by inductively coupled plasma mass spectrometry. Sample preparation was kept to the minimum: serum samples were diluted and beryllium was added as internal standard. Special attention was given to the choice of the internal standard and to the occurrence of memory effects. To test the accuracy of the method several biological reference materials were analysed, namely a “Second-Generation” Biological Reference Material (Freeze-Dried Human Serum) (University of Ghent), Human Serum SRM 909, Whole Egg Powder SRM 1845 and Mixed Human Diet SRM 1548 (National Institute of Standards and Technology). The results were compared with those obtained by other techniques. For the “second-generation” reference freeze-dried human serum a mean lithium concentration of 15.10 ng g^?1 with a standard deviation of 0.54 ng g^?1 dry weight was found. Analyses on serum samples from healthy individuals yielded lithium concentrations ranging from 0.22 to 0.97 μg l^?1.     

Determination of plutonium and americium in environmental samples by inductively coupled plasma sector field mass spectrometry and alpha spectrometry

Application of inductively coupled plasma sector field mass spectrometry (ICP-SFMS) for the determination of americium and plutonium in environmental samples is described in comparison with alpha spectrometry. A sequential sample preparation method was employed using a co-precipitation step for pre-concentration and a separation step applying extraction chromatographic resins. The average recovery of sample preparation calculated from the concentration of the tracer before and after sample treatment was better than 80%. The method development focused on the elimination of possible interferences in mass spectrometric analysis caused by molecular ions (e.g. ²⁰⁰Hg⁴⁰Ar⁺, ²⁰⁴Pb³⁶Ar⁺, ²⁰⁸Pb¹⁶O₂⁺or ²³⁸U¹H⁺) employing matrix separation and desolvation prior to ICP-SFMS analysis. The effect of N₂ gas on signal intensity and oxide ratio was investigated. A two-fold signal improvement was obtained by adding 5 ml min^− 1 N₂ to the sample gas after the desolvation system. For ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²⁴¹Am limit of detection (LOD) of 15, 9.2, 14 and 104 fg g^− 1 was achieved, respectively. Calculation of LOD was based on three times standard deviation of the method blank solution. Absolute detection limit was calculated to be 10-25 fg. For all investigated actinides the precision of the analysis was in the range 0.8-3% relative standard deviation. Results from the analysis of certified reference materials (IAEA-384 and IAEA-385) showed good agreement with recommended values and data available in the literature. The method was applied for analysis of environmental samples originated from Chernobyl and from Mayak region. The possibility of the determination of the origin and date of pollution was demonstrated using isotopic data obtained by ICP-SFMS and alpha spectrometry.     

Determination of zinc in plant samples by isotope dilution inductively coupled plasma mass spectrometry

Determination of zinc involved spiking with (68)Zn enriched solution, digestion by HNO(3)+H(2)O(2) in microwave decomposition unit, off-line separation of zinc on Chelex-100 column and measurement of ((64)Zn+(66)Zn)/(68)Zn isotope ratio on ICP-MS spectrometer with a quadrupole mass filter. After optimization of standard operation procedure (details are given) the method was validated. LOD was found to be 0.3 mug g(-1) for the procedure without zinc separation and 3.6 mug g(-1) for the procedure involving zinc separation, respectively. The accuracy of results was proved by analyses of several CRM and a primary solution of zinc, the concentration of which was verified by gravimetry and complexometric titration. Barium is the only element causing serious interferences and it must be removed from samples. The uncertainty budget is given together with the scheme of combined uncertainty calculation. The main uncertainty components are contamination during zinc separation and uncertainty of isotopic composition of natural zinc.     

Determination of gadolinium in geological samples by inductively coupled plasma mass spectrometry and multivariate calibration

Gadolinium can be difficult to determine by ICP-MS. In a normal geological sample there are risks of spectroscopic interferences on all of its isotopes. In this study this problem has been solved by using partial least squares (PLS) regression. Two PLS models are investigated: the first is based on aqueous standards, and the second on reference materials. Both models are capable of determining Gd with good results in reference materials containing interfering elements. It was not necessary to correct for nonspectroscopic matrix interferences. PLS is compared to principal components regression (PCR), another multivariate calibration method. For the aqueous standards PLS leads to a simpler model, while similar results are obtained for the two methods in the model based on reference materials.     

Determination of trace elements in geological samples by laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was applied for the sensitive multi-element analysis of traces and ultra-traces in geological samples. In order to prepare homogeneous targets the powdered geological samples were melted together with a lithium-borate mixture (90% Li₂B₄O₇, 10% LiBO₂) in a muffle furnace at 1050 °C. The quantification of the analysis results was carried out using the BCR-2G and BM standard reference material (SRM). The experimentally determined relative sensitivity coefficients (RSC) for both SRMs vary between 0.2 and 3 for most of the elements, whereas the relative standard deviation (RSD) of the determination (N = 3) of the concentration was 5–20%. The analysis results of LA-ICP-MS for various geological samples are in agreement with those of other methods. Received 31 March 1999 / Revised: 26 May 1999 / Accepted: 31 May 1999     

Determination of trace elements in geological samples by laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was applied for the sensitive multi-element analysis of traces and ultra-traces in geological samples. In order to prepare homogeneous targets the powdered geological samples were melted together with a lithium-borate mixture (90% Li₂B₄O₇, 10% LiBO₂) in a muffle furnace at 1050?°C. The quantification of the analysis results was carried out using the BCR-2G and BM standard reference material (SRM). The experimentally determined relative sensitivity coefficients (RSC) for both SRMs vary between 0.2 and 3 for most of the elements, whereas the relative standard deviation (RSD) of the determination (N = 3) of the concentration was 5–20%. The analysis results of LA-ICP-MS for various geological samples are in agreement with those of other methods.     

Determination of rare earth elements in environmental matrices by sector-field inductively coupled plasma mass spectrometry

In the framework of an international certification campaign, sector-field inductively coupled plasma mass spectrometry (sector-field ICP–MS) was used for the accurate determination of the rare earth elements in five candidate reference materials: aquatic plant, calcareous soil, mussel tissue, river sediment, and tuna muscle. All samples were taken into solution by use of microwave-assisted or mixed microwave-assisted / open beaker acid digestion. Subsequently, the samples were appropriately diluted and subjected to ICP–MS analysis. Except for Sc, all the elements involved were determined at low mass resolution (R = 300). For Sc, application of a higher resolution setting (R = 3000) was required to separate the analyte signal from those of several molecular ions which gave rise to spectral overlap at low mass resolution. Some of the heavier REE can also suffer from spectral overlap attributed to the occurrence of oxide ions (MO⁺) of the lighter REE and Ba. This spectral overlap could be successfully overcome by mathematical correction. Matrix effects were overcome by use of two carefully selected internal standards, such that external calibration could be used. On each occasion, a geological reference material was analyzed as a quality-control sample and the reliability of all results obtained was additionally checked by means of chondrite normalization. For tuna muscle the content of all REE was below the limit of detection. For calcareous soil and river sediment, low to sub μg g^–1 values were observed, whereas the REE content of aquatic plant and mussel tissue was considerably lower (low to sub ng g^–1). Overall, the results obtained were in excellent agreement with the average values, calculated on the basis of all “accepted” values, obtained in different laboratories using different techniques.     

Determination of rare earth elements in environmental matrices by sector-field inductively coupled plasma mass spectrometry

In the framework of an international certification campaign, sector-field inductively coupled plasma mass spectrometry (sector-field ICP-MS) was used for the accurate determination of the rare earth elements in five candidate reference materials: aquatic plant, calcareous soil, mussel tissue, river sediment, and tuna muscle. All samples were taken into solution by use of microwave-assisted or mixed microwave-assisted / open beaker acid digestion. Subsequently, the samples were appropriately diluted and subjected to ICP-MS analysis. Except for Sc, all the elements involved were determined at low mass resolution (R = 300). For Sc, application of a higher resolution setting (R = 3,000) was required to separate the analyte signal from those of several molecular ions which gave rise to spectral overlap at low mass resolution. Some of the heavier REE can also suffer from spectral overlap attributed to the occurrence of oxide ions (MO+) of the lighter REE and Ba. This spectral overlap could be successfully overcome by mathematical correction. Matrix effects were overcome by use of two carefully selected internal standards, such that external calibration could be used. On each occasion, a geological reference material was analyzed as a quality-control sample and the reliability of all results obtained was additionally checked by means of chondrite normalization. For tuna muscle the content of all REE was below the limit of detection. For calcareous soil and river sediment, low to sub microg g(-1) values were observed, whereas the REE content of aquatic plant and mussel tissue was considerably lower (low to sub ng g(-1)). Overall, the results obtained were in excellent agreement with the average values, calculated on the basis of all "accepted" values, obtained in different laboratories using different techniques.     

Determination of actinides in environmental and biological samples using high-performance chelation ion chromatography coupled to sector-field inductively coupled plasma mass spectrometry

The combination of suppressed and non-suppressed cation-exchange chromatography with electrospray ionization mass spectrometry was demonstrated for the structural elucidation of unknown by-products (mostly quaternary ammonium compounds) in a new cholesterol-reducing drug. The suppressed mode using methanesulfonic acid and acetonitrile turned out to be unsuitable because of regenerant (tetrabutylammonium hydroxide) passing through the membrane of the suppressor into the eluent which led to a significant increase of spectral background in the mass spectrometer. Employing a mobile phase consisting of 200 mM formic acid and 60% (v/v) acetonitrile, the separation and detection of 8 unknown compounds was possible in the non-suppressed mode. The three most prominent compounds were selected for structural elucidation utilizing collision induced dissociation experiments. In a series of experiments the fragmentation behavior was investigated for different fragmentation voltages finally leading to structure proposals. Using gas chromatography hyphenated with mass spectrometry, additional information for the structure of the unknowns was collected and a possible way of their formation was proposed.     

Elimination of interferences in determination of platinum and palladium in environmental samples by inductively coupled plasma mass spectrometry

Various approaches were evaluated in order to eliminate the spectral interferences noted when Pt and Pd has to be determined in environmental dust samples by ICP-MS. The chemical separation of Pt and Pd from the matrix components on ion-exchange resins was applied. The performance of cation-exchange resins (Dowex 50 WX-8, Dowex 50 WX-2, Dowex HCR-S, Varion KS, Cellex-P) for the separation of interfering ions was then examined. It was found that Dowex 50 WX-8 shows best performance. The effects of mass, mesh number of resin and concentration of Cl⁻ ions on matrix separation were also studied. Another approach was to use the anion-exchange sorbent Cellex-T, which allows almost total retention of both analytes followed by their elution with 0.1 mol L⁻¹ thiourea in 1 mol L⁻¹ HCl. This procedure however can be used only for platinum determination by ICP-MS. The accuracy of proposed procedures was confirmed by the analysis of certified material BCR-723, and then it was used for determination Pt and Pd in samples of road dust.     

茶叶和蔬菜中铅的同位素稀释电感耦合等离子体质谱的测定

采用同位素稀释电感耦合等离子体质谱(ID-ICP-MS)法测定了铅的含量,通过对茶叶标准物质(GBW-07605)中铅的测定,考察了方法的准确度和精密度,比较了同位素稀释法与普通外标定量法的测定结果。在5mLHNO3～0.5mLHF～1mLH2O2的消解体系中,ID-ICP-MS法测量茶叶中铅的回收率可达97.7%,相对标准偏差(RSD)小于1.2%。实验对市售的12种茶叶和10种蔬菜中Pb进行测定,铅含量符合相应国家标准的样品分别占总样品数的83%和90%。该法适合于植物样品中微量铅的测定。     

Determination of vanadium by reaction cell inductively coupled plasma mass spectrometry

Recent advances in inductively coupled plasma mass spectrometry (ICP-MS) have included the addition of interference reduction technologies, such as collision and reaction cells, to improve its detection capability for certain elements that suffer from polyatomic interferences. The principle behind reaction cell (RC)-ICP-MS is to remove a particular polyatomic interference by dissociation or formation of a different polyatomic species that no longer interferes with the analyte of interest. However, some interferences cannot be removed by commonly reported reaction gases, such as hydrogen, oxygen, or methane, necessitating using more reactive and hazardous gases, such as ammonia. The current study investigates oxygen as a reaction gas in RC-ICP-MS to specifically react with vanadium analyte ions, rather than the interferents, to produce a polyatomic analyte species and thereby provide a way to analyze for vanadium in complex environmental matrices. The technique has been tested on a series of river water, tap water, and synthetic laboratory samples, and shown to be successful in vanadium analyses in high chloride and sulfate matrices. The zinc isobaric interference on the new vanadium oxide analyte at m/z 67 is also investigated, and can be corrected by using a standard mathematical correction equation. The results of this study further increase the utility of RC-ICP-MS analytical techniques for complex environmental matrices.