Highly accurate and precise multielement determination of environmental samples by means of photon activation using the internal standard method

In order to examine effective applications of the newly developed internal standard method, determinations of Cr, Co, Ni, Zn, As, Rb, Sr, Y, Zr, Nb, Cs, Ce and Pb in three environmental materials, such as pond, lake and estuarine sediments, have been tried by means of photon activation. In these examinations, some major constituent elements in the above sediments were properly used as excellent and effective internal standards. In consequence, it was confirmed that highly accurate and precise determinations of the above 13 elements were achieved easily and favourably.     

Instrumental photon activation analysis of coal fly ashes using the internal standard method coupled with the standard addition method

Multielement determinations of coal fly ashes (NIST SRM-1633a and BCR CRM-38) have been carried out by instrumental photon activation analysis using 30 MeV bremsstrahlung and the internal standard method coupled with the standard addition method. In these determinations, some major and minor constituent elements in the samples were properly used as effective internal standards. As a result, it was demonstrated that concentrations of 18 elements were determined accurately and precisely. Furthermore, a similar multielement determination has also been examined using 20 MeV bremsstrahlung. In this case, it was proved that better results can be achieved, because all interfering reactions were eliminated completely.     

Contributions to accuracy improvement of simultaneous ICP atomic emission spectrometry using multi-line measurements of analyte and internal standard elements Applications for the analysis of permalloy

For successful application of simultaneous ICP atomic emission spectrometry for major component determinations in multi-component materials the accuracy of the method has to be improved. As a contribution to solve this problem a combined procedure for multi-component standard sample preparation, optimum calibration and different variations of internal standard corrections is described. Variance-weighted multi-line calibrations give most accurate results. Internal standard corrections are effective, if the time-dependent spectral line intensity fluctuations of the standard and the analyte elements are well correlated. Their sensitivities against some responsible device parameter variations are investigated. On the basis of multi-line measurements of the analyte and internal standard elements a “group-selected internal standard correction” (GS-ISC) method is applied and results in relative errors of less than 1% even for extreme fluctuations of the raw intensities. For rapid routine determination methods of materials with variable element compositions the added line intensities of the internal standard element can be used to correct the added analyte line raw intensities (“intensity addition internal standard correction” (IA-ISC) method). These accuracy optimization procedures are applied for the analysis of the soft magnetic material permalloy using the internal standard element In.     

Optimized simultaneous determination of several elements in human intestinal Caco-2 TC7 cells by inductively coupled plasma-mass spectrometry after closed vessel microwave digestion

A rapid procedure, based on closed vessels microwave digestion and inductively coupled plasma-mass spectrometry (ICP-MS), was evaluated to ascertain the effect of chronic exposure to cadmium on intracellular accumulation of minor and essential trace elements in cultured epithelial cells (Caco-2 TC7). For all measurements, the method of external calibration was used and 3 elements (Be, Sc, In) were selected as internal standards. Optimization procedures are discussed and results are presented for the total determination of 9 key analytes (Na, Mg, Ca, Cr, Mn, Cu, Zn, Mo, and Cd) in certified reference materials (CRMs) and 20 samples of Caco-2 TC7 cells long-term exposed to Cd. The performance characteristics of the analytical system were evaluated by calibration and linearity, limits of detection and quantitation, accuracy with spiking, trueness and repeatability with available CRMs. As a complement to the ICP-MS determinations, both available CRMs and cell samples were analyzed either by electro thermal- or flame atomic absorption spectrometry. The results were in good agreement with the ICP-MS results.     

Instrumental NAA of carbonate rocks and its application for the analysis of secondary sedimentary environments in shallow sea

Aiming at distinguishing between the sedimentary environments in shallow sea using elemental geochemical markers, the determinations of trace elements in carbonate rocks by thermal neutron, epithermal neutron and short-irradiation activation analysis have been studied, and more than 30 major and trace elements determined. Al, Cl, Sc, Ti, V, Cr, Fe, Co, As, Br, Rb, Sb, Cs, Lu, Hf, Ta, Th and U were found to be the effective distinguishing markers for the secondary environments in shallow sea.     

Possibilities of the Determination of Matrix Elements of High-Purity Glasses of As–Se and As–S Systems by Inductively Coupled Plasma Atomic Emission Spectrometry

Possibilities of inductively coupled plasma atomic emission spectrometry (ICP AES) as an alternative to X-ray spectrochemical analysis are estimated in the determination of matrix elements of glasses of As–Se and As–S systems. Standard solutions were prepared from pure elements As, Se and S. It was shown that the matrix elements of glasses can be determined with an expanded uncertainty of 0.05–0.1 mol %. The results of determinations by ICP AES and X-ray fluorescence spectrometry were compared; and it was found that by the attained performance characteristics, the results of ICP AES are highly competitive with the data of X-ray fluorescence spectrometry, but do not require sets of adequate solid reference samples.     

Instrumental charged-particle activation analysis of several selected elements in biological materials using the internal standard method

In order to study instrumental charged-particle activation analysis using the internal standard method, simultaneous determination of several selected elements, such as Ca, Ti, V, Fe, Zn, As, Sr, Zr and Mo, in oyster tissue, brewer's yeast and mussel has been examined by using the respective (p, n) reactions and a personal computer-based gamma-ray spectrometer equipped with a micro-robot for sample changing. In the above determination, constant amounts of Y and La were added to the sample and comparative standard as exotic internal standards. As a result, it was demonstrated that concentrations of the above elements can be determined accurately and precisely.     

微波消解-电感耦合等离子体质谱法测量小麦粉中铅、镉、砷和铬

在我国局部都存在不同程度的铅、镉、砷和铬的土壤和水资源污染,土壤和水域中的有毒有害元素经食物链累积在人体,对人们的身体造成极大的危害,因此对食品中这些限量元素进行准确高效定量非常必要。本文建立了微波消解-电感耦合等离子体质谱(ICP-MS)法对小麦粉中的Pb、Cd、As和Cr进行测量,测量方法采用内标法,内标元素选择Rh、In和Bi。另外对微波消解前处理方法和ICP-MS使用参数进行了优化,测量方法简单高效。工作标准曲线呈良好的线性关系,相关系数均大于0.9999。该方法采用GBW(E)100493小麦粉标准物质和NIST 1567b Wheat Flour对本实验所采用的方法进行验证,结果显示测量值和标准值一致,表明本实验中小麦粉中Pb、Cd、As和Cr的测定方法是准确可靠的。     

Direct determination of Se and As in solid certified reference materials using electrothermal vaporization inductively coupled plasma mass spectrometry

Firstly, electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) has been successfully applied for the direct determination of Se in solid certified reference materials (CRMs) of both biological and environmental origin. Secondly, in order to exploit one of the most important advantages of ICP-MS (the multi-element capability), Se and As have been determined simultaneously in two CRMs (“Sea lettuce” and “Estuarine sediment”), the potential of ETV-ICP-MS for accurate mono-element determination of As in solid CRMs having been proven in a previous study. For both the mono-element and the multi-element determinations, several parameters (ashing and vaporization temperature, carrier gas flow rate) have been studied systematically in order to obtain optimized conditions. Both the linearity of the mass response curves and the signal profiles (signal intensity as a function of time) are examined. Absolute detection limits, based on the 3s criterion, are found to be approximately 1 pg. Using single standard addition for calibration and Sb as an internal standard, accurate results are obtained for both the mono-element determinations of Se (mean relative difference with the certified value of 6.5%) and the multi-element determinations of Se and As (mean relative difference with the certified values of, respectively, 6.6% for Se and 7.2% for As).     

Semiquantitative Analysis of Biological Materials by Inductively Coupled Plasma–Mass Spectrometry

Semiquantitative analysis with accuracy of ±30 to 50% is a valuable tool for rapid screening of samples prior to quantitative determination of trace metals. In this study semiquantitative analysis software available with commercial inductively coupled plasma–mass spectrometry (ICP-MS) instrumentation is applied for rapid multielemental analysis, and the accuracy and precision of this semiquantitative analysis approach is evaluated with biological certified reference materials. Samples were prepared by high-pressure, high-temperature nitric acid vapor-phase digestion. For most elements the measured semiquantitative results are in the range of the certified values. With appropriate analyte solution dilution, the measured concentrations of the major elements (e.g., Ca) also agree with certified values. The accuracy is within ±10% for 28 element determinations that include 16 individual elements (Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Rb, Sb, Sr, Tl, and Zn) and ±20% for 54 element determinations that include three more elements (Mg, V, and U) in eight certified reference materials including water. The method precision is 11 ± 11% (relative standard deviation,n= 65).     

Simultaneous determination of Ti,Cr, Fe,Cu, Ga and Zr in aluminium alloys by charged-particle activation analysis using the internal standard method

In order to study the application of the new developed internal standard method to charged-particle activation analysis, simultaneous determination of Ti, Cr, Fe, Cu, Ga and Zr in several commercial aluminium alloys has been tried using the respective proton-induced reactions. As a result, it could be proved that the best precision and accuracy are also obtained in these determinations.     

Simultaneous determination of sixteen major and minor elements in river sediments by energy-dispersive x-ray fluorescence spectrometry after fusion in lithium tetraborate glass

Fluvial sediments, including the NBS SRM-1645 Standard River Sediment, were fused in lithium tetraborate to form glass discs on which determinations of 16 elements (K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr and Pb) were obtained simultaneously at a single set of x-ray conditions by energy-dispersive x-ray fluorescence spectrometry (e.d.x.r.f.). Relatively high sample-to-flux ratios of 1:3 were employed to obtained determinations of several minor as well as major elements on a single disc. Lower sample concentrations 1:6 and 1:10 were also used with the NBS SRM-1645. Inter-element corrections for absorption by iron were significant for detectable elements heavier than iron. In the NBS SRM-1645 samples, corrections were made for the fluorescence of chromium by the Fe K lines as well as the absorption of the Fe K lines by chromium. A background correction was also necessary for manganese in NBS SRM-1645. At the lowest sample-to-flux ratio (1:10) good agreement was obtained between the e.d.x.r.f. determinations and the NBS values for all quantifiable elements except zinc. At higher sample-to-flux ratios, agreement with the NBS values was generally poorer with increasing sample concentration. The relative standard deviation (RSD) of the eight quantifiable major and minor elements (K, Ca, Ti, Mn, Fe, Zn, Sr and Zr) determined under a single set of x-ray conditions ranged from 2 to 9% (RSD) with a mean RSD of 4.4% for a set of replica discs fused with Lake Pueblo/Arkansas River sediment samples.     

Determination of As, Sb, Bi and Hg in water samples by flow-injection inductively coupled plasma mass spectrometry with an in-situ nebulizer/hydride generator

A simple and very inexpensive in-situ nebulizer/hydride generator was used with inductively coupled plasma mass spectrometry (ICP-MS) for the determination of As, Sb, Bi and Hg in water samples. The application of hydride generation ICP-MS alleviated the sensitivity problem of As, Sb, Bi and Hg determinations encountered when the conventional pneumatic nebulizer was used for sample introduction. The sample was introduced by flow injection to minimize the deposition of solids on the sampling orifice. The elements in the sample were reduced to the lower oxidation states with L-cysteine before being injected into the hydride generation system. This method has a detection limit of 0.003, 0.003, 0.017 and 0.17 ng ml⁻¹ for As, Bi, Sb and Hg, respectively. This method was applied to determine As, Sb, Bi and Hg in a CASS-3 nearshore seawater reference sample, a SLRS-2 riverine water reference sample and a tap water collected from National Sun Yat-Sen University. The concentrations of the elements were determined by standard addition method. The precision was better than 20% for most of the determinations.     

Determination of trace elements in marine plankton by inductively coupled plasma mass spectrometry (ICP-MS)

A method has been developed for the determination of 23 elements in marine plankton in which inductively coupled plasma (ICP) source mass spectrometry (MS) was used to quantify the elements in the solution after digestion in a mixture of hydrofluoric and nitric acids in sealed PTFE vessels in a microwave field. The procedure was validated by the analysis of a standard reference soil (SRM 2709 San Joaquin Soil) and a standard reference fresh water plankton (CRM 414). The method was applied to the analysis of several marine plankton samples grown under controlled conditions including several whose growth media had been enriched with selenium. Matrix induced signal suppressions and instrumental drift were corrected by internal standardization. The suitabilities of germanium, indium, rhodium, scandium and yttrium as internal standard elements were evaluated. Neither scandium nor yttrium could be used due to the presence of these elements in the samples, germanium was used for the determination of As, Co, Cu, Fe, Ni, Se, Si and Zn, indium was used for Al, Ba, Ca, Eu, Sr, and Tl, and rhodium was used for Cd, Cr, Hg, Mg, Pb, Sb, Sn, and V. For Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Si, Sr, V, and Zn internal standardization did not completely compensate for the suppressive effect of the heavier elements and the solutions were diluted. However, for As, Ba, Cd, Co, Eu, Hg, Pb, Sb, Se, Sn and T1, it was possible to obtain accurate results despite the 35-40% suppression in the signals. Isobaric overlap was only a problem in the cases of 42Ca and 78Se; 44Ca and 77Se, respectively, were used. Memory effects were only observed with Hg for which a nitric acid-sodium chloride solution was the most effective wash-out solution. The marine plankton samples were able to tolerate a higher concentration of Hg as the selenium concentration increased.     

Trace element analysis of high purity arsenic through vapour phase dissolution and ICP-QMS

Vapour phase dissolution (VPD) has been used for the dissolution of high purity arsenic through acid vapours generated by aquaregia mixture, prior to trace element characterization. Trace impurities in As were determined by employing ion-exchange and volatilization methodologies for quantitative separation of the As matrix. After dissolving the As matrix through VPD procedure, sample solution in 0.1 M HF medium was loaded on Dowex-50WX8. The sorbed elements were then eluted first with a 20 ml aliquot of 4 M HNO₃ followed by another 10 ml of 6 M HNO₃ for the elution of REE (La, Ce, Gd and Lu). In the volatilization procedure, arsenic was removed from H₂SO₄ medium as volatile bromide by three successive additions of HBr at a temperature of about 220 °C. The trace element determinations were carried out by ICP-QMS. In both the matrix separation procedures namely on Dowex-50WX8 in 0.1 M HF medium and volatilization from H₂SO₄+HBr medium showed that the removal of arsenic matrix was nearly quantitative (>99.99%). The recoveries of trace elements were found to be >95%. Good agreement was obtained for many elements in both the procedures. The VPD approach provides considerable reduction of the process blank levels for all the elements when compared with conventional open dissolution approach. The subsequent ion-exchange or volatilization steps, contribute more to the overall process blanks.     

Development of an Automated Procedure for the Optimization of Multielement Analysis with Energy Dispersive X-Ray Fluorescence Spectroscopy

Abstract

A system is devised that automatically optimizes energy dispersive x-ray spectrometer settings for multielement determinations under compromise conditions using self-sustained search algorithms. As an objective function, the joint probability of detecting all elements was chosen. The current process is to date limited by the resolution of the commercially available automatic power supply employed. Typical optimization times needed for the entire procedure are on the order of 5 minutes for major constituents, with prolonged times for minor and trace elements as a result of increased counting time to obtain good counting statistics.     

Analysis of FDA in-house food reference materials with anticoincidence INAA

In-house reference material (IRM) cocoa powder (CCP) has been in use at US Food and Drug Administration laboratories for about 15 years. A single lot of commercial material was originally characterized for 32 elements by several laboratories and five techniques. A unique approach for basis weight determination based upon ambient relative humidity was developed for CCP, eliminating the need for dry weight determinations. The CCP Reference Sheet is updated by incorporating new results approximately every 5 years. The last update occurred in 2006. As part of an effort to revalidate and update values for CCP, anticoincidence instrumental neutron activation analysis (INAA) was used to determine mass fractions for 16 of the originally characterized elements, as well as to provide information on 16 other elements. Results were in very good agreement with 2006 Reference Sheet values. A new candidate IRM, fresh-frozen swordfish (FFSF) powder, was produced by adding inorganic As, Cd, Cr, Hg, Pb, Sb, and Se to liquid nitrogen-frozen commercial swordfish filets which were then homogenized. Portions of FFSF were analyzed by INAA to provide mass fraction and homogeneity information for As, Cd, Cr, Hg, Sb, and Se as well as for eight other elements occurring naturally in the material. Non-homogeneities were ≤2.5 % for As, Br, Cd, and Cs, and ≤1.8 % for Cr, Hg, Rb, Sb, and Se. Certified reference materials DORM-3 Fish Protein powder and fresh-frozen SRM 1947 Lake Michigan Fish Tissue were analyzed as controls.     

Determination of trace elements in marine plankton by inductively coupled plasma mass spectrometry (ICP-MS)

A method has been developed for the determination of 23 elements in marine plankton in which inductively coupled plasma (ICP) source mass spectrometry (MS) was used to quantify the elements in the solution after digestion in a mixture of hydrofluoric and nitric acids in sealed PTFE vessels in a microwave field. The procedure was validated by the analysis of a standard reference soil (SRM 2709 San Joaquin Soil) and a standard reference fresh water plankton (CRM 414). The method was applied to the analysis of several marine plankton samples grown under controlled conditions including several whose growth media had been enriched with selenium. Matrix induced signal suppressions and instrumental drift were corrected by internal standardization. The suitabilities of germanium, indium, rhodium, scandium and yttrium as internal standard elements were evaluated. Neither scandium nor yttrium could be used due to the presence of these elements in the samples, germanium was used for the determination of As, Co, Cu, Fe, Ni, Se, Si and Zn, indium was used for Al, Ba, Ca, Eu, Sr, and Tl, and rhodium was used for Cd, Cr, Hg, Mg, Pb, Sb, Sn, and V. For Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Si, Sr, V, and Zn internal standardization did not completely compensate for the suppressive effect of the heavier elements and the solutions were diluted. However, for As, Ba, Cd, Co, Eu, Hg, Pb, Sb, Se, Sn and Tl, it was possible to obtain accurate results despite the 35–¶40% suppression in the signals. Isobaric overlap was only a problem in the cases of ⁴²Ca and ⁷⁸Se; ⁴⁴Ca and ⁷⁷Se, respectively, were used. Memory effects were only observed with Hg for which a nitric acid-sodium chloride solution was the most effective wash-out solution. The marine plankton samples were able to tolerate a higher concentration of Hg as the selenium concentration increased.     

High-throughput determination of seven trace elements in food samples by inductively coupled plasma-mass spectrometry

A method was developed for high-throughput determinations of 7 elements in food samples, namely antimony (Sb), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and tin (Sn). The samples were digested by closed-vessel microwave-assisted digestion using concentrated nitric acid (HNO3) as the medium, followed by microwave- assisted evaporation to concentrate the sample solutions before dilution to the desired volume. The microwave-assisted evaporation procedure effectively reduced the final acid concentration to around 8% before analysis by inductively coupled plasma-mass spectrometry (ICP-MS). This reduction allows determination by ICP-MS to proceed without further sample dilution, which would affect the detection limit. The method was validated, and method recoveries for As, Cd, Cr, Pb, and Hg were within the certified ranges of the chosen certified reference materials. Recoveries of the 7 elements from spiked samples ranged from 93.1 to 103.6%. The standard uncertainties of precision for the 7 elements were between 3.1 and 4.3%. Interlaboratory comparison studies for As, Cd, and Pb gave z-scores ranging from -0.2 to 0.3.     

Characterization and Improvement of Ion Exchange Capacities of Mexican Clinoptilolite-rich Tuffs

Clinoptilolite-rich tuffs from the states of Chihuahua and Oaxaca in Mexico were modified with NaCl solutions to improve their ion exchange properties using different conditioning processes. First, the elemental and sodium compositions were identified by both induced coupled plasma atomic emission spectroscopy and neutron activation, respectively. The clinoptilolite-rich tuffs were characterized by scanning electron microscopy and X-ray diffraction and the surface areas were also determined in both tuffs. Effective, internal and external cation exchange capacities were determined. It was found that the elemental composition was different in both zeolitic rocks. A sodium treatment using a 0.1 M NaCl solution and reflux thus, improves effective cation exchange capacities of the Mexican clinoptilolite-rich tuffs. The external and internal cation exchange capacities depend on the size of the particle, as well as the source of the zeolitic rocks. The quaternary ammonium salt (HDTMABr or BCDMACl) considered is important in those determinations.