Revaluation of the internal standard method coupled with the standard addition method applied to soil samples by means of photon activation

In order to achieve the highly accurate and precise multielement determination in environmental materials, the usefulness of the comparative standard provided by the processing method proposed previously for soil samples has been re-examined using calcareous loam soil, light sandy soil and river sediment as unknown samples. As a result, it was also demonstrated that concentrations of 15 trace elements in each sample can be determined effectively and reasonably.     

Amberlite XAD-4 functionalized with succinic acid for the solid phase extractive preconcentration and separation of uranium(VI)

Amberlite XAD-4 resin has been functionalized with succinic acid by coupling it with dibromosuccinic acid after acetylation. The resulting resin has been characterized by FT-IR, elemental analysis and TGA and has been used for preconcentrative separation of uranium(VI) from host of other inorganic species prior to its determination by spectrophotometry. The optimum pH value for quantitative sorption of uranium(VI) in both batch and column modes is 4.5-8.0 and desorption can be achieved by using 5.0 ml of 1.0 mol l⁻¹ HCl. The sorption capacity of functionalized resin is 12.3 mg g⁻¹. Calibration graphs were rectilinear over the uranium(VI) concentrations in the range 5-200 μg l⁻¹. Five replicate determinations of 50 μg of uranium(VI) present in 1000 ml of solution gave a mean absorbance of 0.10 with a relative standard deviation of 2.56%. The detection limit corresponding to three times the standard deviation of the blank was found to be 2 μg l⁻¹. Various cationic and anionic species at 200-fold amounts do not interfere during the preconcentration of 5.0 μg of uranium(VI) present in 1000 ml (batch) or 100 ml (column) of sample solution. Further, adsorption kinetic and isotherm studies were also carried out by a batch method to understand the nature of sorption of uranium(VI) with the succinic acid functionalized resin. The accuracy of the developed solid phase extractive preconcentration method in conjunction with Arsenazo III procedure was tested by analyzing marine sediment (MESS-3) and soil (IAEA soil-7) reference material. Further, the above procedure has been successfully employed for the analysis of soil and sediment samples.     

A new internal standard method for activation analysis and its application. Determination of Co,Ni, Rb,Sr in pepperbush by means of photon activation

A new internal standard method for activation analysis has been developed. This method is characterized by that a suitable element present originally in the sample is used as an internal standard and the comparative standard is prepared by applying the standard addition method to the duplicated sample. When a sample under examination contains W_ag of trace element A to be determined together with a known amount of element B which is usable as an internal standard, and when the comparative standard is prepared by adding W _a ^* g of accurately known small amount of the element A to the duplicated sample, even if the sample and comparative standard are irradiated separately by particles with different fluxes, W_a can be determined, easily by using the following equation: W_a=W _a ^* /[(A _R ^* /A_R)-1] Where A_R and A _R ^* are counting ratios of gamma-rays emitted by two radioactive nuclides produced from the element A and B in the sample and comparative standard, respectively. Neither correction of the inhomogeneities of flux between the sample and comparative standard, nor that of, the self-shielding effects are necessary for the present method. The usefulness of the method was examined through the determination of Co, Ni, Rb and Sr in pepperbush by means of photon activation, and the precision and accuracy of the method were proved to be valid.     

Determination of dysprosium by INAA in some Bulgarian standard rocks

Dy content has been determined by INAA in the Bulgarian standard rocks BV, GV, DM, MrA, OgG, OZnO and in the IAEA standard reference materials SL-1, SOIL-5, and SOIL-7. Results are compared with Dy values obtained by interpolation of the chondrite-normalized contents of other REE in these samples.     

Neutron activation analysis of reference materials by the k0-standardization and relative methods

Instrumental neutron activation analysis with the k₀-standardization method was applied to eight geological, environmental and biological reference materials, including leaves, blood, fish, sediments, soil and limestone. To a first approximation, the results were normally distributed around the certified values with a standard deviation of 10%. Results obtained by using the relative method based on well characterized multi-element standards for IAEA CRM Soil-7 are reported.     

A complex neutron activation method for the analysis of biological materials

The aim of the present work was to deal primarily with a few essential trace elements and to obtain reliable results of adequate accuracy and precision for the analysis of biological samples. A few other than trace elements were determined by the nondestructive technique as they can be well evaluated from the gamma-spectra. In the development of the method BOWEN's kale was chosen as model material. To confirm the reliability of the method two samples were analysed proposed by the IAEA in the frame of an international comparative analysis series. The comparative analysis shows the present method to be reliable, the precision and accuracy are good.     

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.     

Instrumental neutron activation analysis based on k0-standardization method as compared with other methods in the analysis of the IAEA inter-comparison test

Results of inter-comparison test organized by the IAEA are analyzed according to the contribution and performance of INAA as non-destructive method for trace elements analysis as compared to other techniques. Several methods were employed for certifying the biological sample (IAEA-0140) and were also compared. It is shown that NAA is the method of a good accuracy and precision. The biological sample has been investigated by INAA based on semi-absolute technique. More than 30 elements have determined without using standards. The reference materials, which are certified in this manner and utilized as primary standard, are also discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Enhanced spectrofluorimetric determination of aflatoxin B1 in wheat by second-order standard addition method

Determination of aflatoxin B1 (AFB1) in wheat has been accomplished by enhanced spectrofluorimetry in combination with second-order standard addition method (EF-SOSAM). The adopted strategy combined the use of parallel factor analysis (PARAFAC) for extraction of the pure analyte signal and the standard addition method, for a determination in the presence of matrix effect caused by wheat matrix. The method is based on the enhanced fluorescence of AFB1 by beta-cyclodextrin in 10% (w/w) methanol-water solution. After sample treatment and without any extended cleanup steps and derivatization process, four standard additions were performed for each sample. A specific PARAFAC model was built from three-way arrays formed by excitation-emission spectra and 5 measurements (sample plus 4 additions). The scores related to AFB1 were used for a linear regression in the standard addition method. Two naturally contaminated wheat and spiked wheat samples containing AFB1 in the range 0-18 microg kg(-1) were analyzed by EF-SOSAM and compared with HPLC results. EF-SOSAM analysis of spiked wheat samples gave a good correlation with spiked values (R(2)>0.990). The limit of detection of method was 0.9 microg kg(-1) for the determination of AFB1 in wheat samples.     

Combining standard addition method and second-order advantage for direct determination of salicylate in undiluted human plasma by spectrofluorimetry

Second-order advantage turns possible a determination in the presence of unknown interferences. This work presented an application of the second-order advantage provided by parallel factor analysis (PARAFAC). The aim was the direct determination of salicylic acid (SA), the main product of aspirin degradation, in undiluted human plasma by spectrofluorimetry. The strategy of this analysis combined the use of PARAFAC, for extraction of the pure analyte signal, with the standard addition method, for a determination in the presence of a strong matrix effect caused by the quenching effect of the proteins present in the plasma. For each sample, four standard additions were performed, in triplicates. A specific PARAFAC model was built for each triplicate of each sample, from three-way arrays formed by 436 emission wavelengths, 7 excitation wavelengths and 5 measurements (sample plus 4 additions). In all the cases, the models were built with three factors and explained more than 99.90% of the total variance. The obtained loadings were related to SA and two background interferences. The scores related to SA were used for a linear regression in the standard addition method. Good results were obtained for determinations in the SA concentration range from 3.0 to 24.0 μg ml⁻¹, providing errors of prediction between 0.7 and 6.3%.     

Assessment of three digestion procedures for Zn contents in Pakistani soil by flame atomic absorption spectrometry

Evaluation of three different digestion procedures for accurate determination of elemental concentration in soils was undertaken. The digestion procedures, two leaching and a total dissolution processes were compared for twenty-one soil samples. The soil standard reference materials (SRMs), IAEA Soil-5 and IAEA Soil-7 were analysed for quality control purposes. Zinc (Zn) was analysed using flame atomic absorption spectrometry (FAAS). Precise analysis was accomplished in the SRM and soil samples, which was better than 4.7% for leaching and total dissolution procedure. Compared with the elemental concentration in soil samples, HF–HClO₄ procedure achieved greater accuracy, where as HNO₃–H₂O₂ and HNO₃–H₂SO₄–HCl procedures were comparable with slight variation in a few samples.     

Precision and accuracy of laser ablation-ICP-MS analysis of rare earth elements with external calibration

Solid sample introduction into an ICP-MS by laser ablation is an effective method for the total analysis of rare earth elements (REEs) in soils because no digestion is needed. A problem of the method, however, is the difference of the ablated mass for each laser shot. Therefore, internal standard for the compensation of signal instability, sample preparation, and the calibration method have to be carefully chosen.The analyzed sample was a certified standard provided by IAEA (SOIL-7). The sample was mixed with an internal standard solution and polyethylene (PE), dried, homogenized in a ball-mixer/mill, and pressed to a pellet. For the calibration 5 external standards with increasing REEs concentrations (0.4–20 g/g) as well as a blank were prepared in the same way.The analysis of the pellets was performed on a VG PlasmaQuad II + with a LaserLab unit. The laser ablation-cell was modified to improve the sample particle transportation characteristics and to allow a quicker sample-exchange. The pellets were ablated from six different spots for 60 s each with a laser-repetition rate of 4 Hz.The correlation coefficients of the calibration curves based on 5 standards, were better than 0.995. The concentrations c_A of the 15 REEs in the soil sample were determined with an average relative confidence interval 100(CI)/c_A of 6.95%, as a figure for the precision. This good precision have been obtained with a new laser ablation cell, which will be described in detail.With 2 exceptions (Ce and La) the measured concentrations were within the confidence intervals (CI) of the certified values. Therefore, with respect to accuracy and precision, the presented method offers a convenient way to analyze homogeneous and powdered soil samples for REE's without digestion. Since a good calibration for the REE determination may be obtained, the laser sampling variance (within the sample) is less significant than the analytical variance. Automation of the method is possible by construction of an autosampler based on the modified laser cell.Presented in part at the 1993 European Winter Conference on Plasma Spectrochemistry, Granada, Spain     

Determination of trace metals in sediment standard reference materials by graphite-furnace atomic absorption spectrometry with a stabilized temperature platform

Trace elements (As, Be, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, V, Zn) in NBS 1645 (river sediments), NBS 1646 (estuarine sediment), MESS-1 and BCSS-1 (marine sediments), IAEA SL-1 (Lake Sediment) and IAEA Soil-5, are determined by graphite furnace atomic absorption spectrometry with the L'vov platform. The samples (ca. 0.25 g) are dissolved in a mixture of nitric, perchloric and hydrofluoric acids in a PTFE bomb. Results based on direct calibration with simple aqueous solutions are in good agreement with those obtained by the method of standard additions and with recommended values. The relative standard deviations are generally 5–10%. Chromium determinations are also evaluated by inductively-coupled plasma/atomic emission spectrometry.     

Application of the internal standard method coupled with the standard addition method in photon activation analysis to trace characterization of environmental materials

The internal standard method coupled with the standard addition method has been applied to the analysis of environmental materials, such as urban particulate matter, vehicle exhaust particulates and coal fly ash by photon activation. High-resolution gamma-ray spectrometry makes possible to use multi-internal standard gamma-rays, in order to crosscheck the analytical results obtained from each internal standard. It was ascertained that this method can provide not only accurate analytical results but also the information of homogeneity of samples, correlation of elements in the sample, loss or contamination in the preparation process.     

Dithiocarbamate functionalized or surface sorbed Merrifield resin beads as column materials for on line flow injection-flame atomic absorption spectrometry determination of lead

This article describes the preparation of dithiocarbamate immobilized/functionalized and diethylammonium dithiocarbamate (DDTC) sorbed Merrifield Chloromethylated Resin (MCR) beads and comparison of these materials for on-line flow injection (FI)–flame atomic absorption spectrometry (FAAS) determination of lead. The above two materials enrich lead quantitatively over an identical optimal pH range (8.0–9.0), a preconcentration/loading time (up to 4 min) and elution with acidified methanol (a minimum of 0.01 mol L⁻¹ HNO₃ in methanol). However, the detection limit for lead using dithiocarbamate functionalized MCR beads is 1.3 μg L⁻¹ compared to 3 μg L⁻¹ for DDTC sorbed MCR beads. Again, the sensitivity enhancement over direct FAAS signal is 48- and 27-fold, respectively. In addition, dithiocarbamate functionalized MCR beads offers better precision compared to DDTC sorbed MCR beads as the corresponding relative standard deviation (R.S.D.) values for five successive determinations of 0.20 μg mL⁻¹ are 1.44 and 4.36%, respectively. The accuracy of the developed on-line FI–FAAS procedure employing dithiocarbamate functionalized MCR beads as column material was tested by analyzing Certified Reference Material (CRM) of soil (IAEA soil-7) and marine sediment reference material (MESS-3) supplied by International Atomic Energy Agency (IAEA), Vienna and National Research Council (NRC), Canada, respectively. Furthermore, the developed procedure has been successfully tested for the analysis of surface, pond, ground and effluent water and soil samples collected from the vicinity of lead acid battery industry in India.     

Determination of silver in SOIL-7 standard reference material by NAA

IAEA standard reference material SOIL-7 has been analyzed by both instrumental NAA and radiochemical NAA using epithermal neutron activation. These analyses confirm the NAA value of Ag in the intercomparison SOIL-7 which disagrees with some AAS values. Further geostandards were included and compared with literature data.     

GF-AAS法和HG-AFS法测定土壤中铅的分析方法比较

为验证土壤中铅的氢化物发生原子荧光光谱法(HG-AFS)的有效性,对3种土壤标准样品(GSS-2,GSS-3及GSS-7)进行测定,同时用国家标准方法GB/T 17141—1997[石墨炉原子吸收光谱法(GF-AAS)]进行比较测定。试验结果表明:两种方法的测定结果均与认定值一致。在精密度、回收率及检出限等方面,HG-AFS法均达到与GF-AAS法相当的水平。但HG-AFS法具有操作简单、分析快速等优势。     

Photon and proton activation analysis of iron and steel standards using the internal standard method coupled with the standard addition method

The internal standard method coupled with the standard addition method has been applied to photon activation analysis and proton activation analysis of minor elements and trace impurities in various types of iron and steel samples issued by the Iron and Steel Institute of Japan (ISIJ). Samples and standard addition samples were once dissolved to mix homogeneously, an internal standard and elements to be determined and solidified as a silica-gel to make a similar matrix composition and geometry. Cerium and yttrium were used as an internal standard in photon and proton activation, respectively. In photon activation, 20 MeV electron beam was used for bremsstrahlung irradiation to reduce matrix activity and nuclear interference reactions, and the results were compared with those of 30 MeV irradiation. In proton activation, iron was removed by the MIBK extraction method after dissolving samples to reduce the radioactivity of⁵⁶Co from iron via⁵⁶Fe(p,n)⁵⁶Co reaction. The results of proton and photon activation analysis were in good agreement with the standard values of ISIJ.     

INAA in the determination of the elemental constituents of a natural fluorite

A complementary use of the comparative and the semi-absolute variations of instrumental neutron activation analysis (INAA) has enabled us to determine 22 different elements in a sample of natural fluorite originating from the younger granite province of Nigeria. The mineral has a brownish purple appearance with some veinlets having a deep purple coloration. Of all the 22 elements measured, Fe (851.36 ppm), Sb (7.69 ppm), Ag (87.4 ppm), Hg (2.71 ppm) and Se (1.97 ppm) are found to be exclusive to the veinlets while Au (109.15 ppm), Co (2.15 ppm) and W (173.20 ppm) are concentrated in the main matrix of the fluorite. With the aid of the semi-absolute method, it was possible to measure the Au concentration in the IAEA Soil-7 reference material to be 56.83±5.87% ppm. A qualitative electron microprobe analysis (EMA) showed that the bulk of the matrix is composed mainly of Ca and F, as expected.