Determination of thorium and uranium in activated concrete by inductively coupled plasma mass spectrometry after anion-exchange separation

A sensitive analytical method was established for the determination of Th and U in activated concrete samples. The method combines an anion-exchange separation step with an ICP-MS determination technique. In the ICP-MS measurement, a few μg mL^–1 of Al and Ca, a few ng mL^–1 of Mn, La, Ce, Nd and Pb and pg mL^–1 amounts of Li, Zr, Nb and Ba coexisting in the anion-exchange fraction of Th and U did not interfere. No adverse interference effects were observed in real sample analyses. The obtained detection limits (3σ, n = 10) of Th and U were 2.3 and 1.8 pg mL^–1, respectively. The analytical precisions for ca. 5 μg g^–1 Th and ca. 1 μg g^–1 U in real activated concrete samples were equally less than 7% RSD. The accuracies obtained by the analysis of GSJ rock standard samples were –18.1 to 0.4% for the Th determination and –14.0 to –5.7% for the U determination. The method uses the conventional absolute calibration curve. The internal standard calibration is unnecessary. Received: 14 March 1999 / Revised: 13 July 1999 / Accepted: 15 July 1999     

Study of the preconcentration and determination of ultratrace rare earth elements in environmental samples with an ion exchange micro-column

A study was carried out on the preconcentration of ultratrace rare earth elements (REEs) in environmental samples with a micro ion-exchange column and determination by inductively coupled plasma mass spectrometry (ICP-MS). The preconcentration parameters were optimized and the REE recovery was ca. 100% in the pH range 4 to 6 with an ionic strength (μ) less than 0.18. The ion-exchange column capacity with respect to REEs was estimated as 0.96 mmol/g. The linear response coefficients ranged from 0.995 to 0.997 at the pg mL^–1 level. The concentration in the blank could be minimized (0.09 to 3.1 pg mL^–1) if the buffer solution and the water were purified. The detection limits ranged from 0.03 to 0.40 pg mL^–1, for a preconcentration factor of 100. The precision and accuracy of the method was evaluated with a synthetic standard solution and real samples. Results indicated that the REE recovery ranged from 88.1% to 100.2%, and the RSD ranged from 2.7% to 6.7%. Satisfactory results were achieved when this method was applied for the determination of REEs in raw water, purified water and tap water, as well as in environmental aquatic samples. Meanwhile, the method is simple and flexible.     

Application of a hexapole collision and reaction cell in ICP-MS Part II: Analytical figures of merit and first applications

The application of an ion-guiding gas-filled hexapole collision/reaction cell in ICP-MS has been studied to characterize the analytical figures of merit that can be achieved with this approach. For the elements investigated, application of a buffer and a reaction gas resulted in improved sensitivities which are lowest for Be with about 7 · 10⁷ cps per μg mL^–1 and highest for Ba with about ¶6 · 10⁸ cps per μg mL^–1. Relative standard deviations (RSD) < 0.1% were obtained. Application of the reaction gas H₂ was used to suppress polyatomic ions caused by argon. The reduction amounted up to four orders of magnitude so that elements such as Ca, K, Cr, Fe, As and Se could be analyzed in nitric and hydrochloric acid or in methanol. Detection limits of 6 pg mL^–1 for Cr in 2% methanol, 23 pg mL^–1 for As and 9 pg mL^–1 for Se in 0.28 M HCl were achieved. For other elements detection limits ¶< 1 pg mL^–1 were realized in the medium and high mass range. Accuracy was proved using the NIST 1643d standard reference material.     

Headspace single-drop microextraction coupled with gas chromatography electron capture detection of butanone derivative for determination of iodine in milk powder and urine

A new detection method using headspace single-drop microextraction (HS-SDME) coupled to gas chromatography (GC) was established to determine the iodine in milk powder and urine. The derivative from the reaction between iodine and butanone in the acidic media was extracted into a micro-drop then determined by GC-ECD. With the optimisation of HS-SDME and derivatisation, the calibration curve showed good linearity within the range of 0.004–0.1 μg mL^?1 (0.004–0.1 μg g^?1) (R ² = 0.9991), and the limits of detection for milk powder and urine were 0.0018 μg g^?1 and 0.36 μg L^?1, respectively. The mean recoveries of milk powder and urine were 90.0–107 % and 89.4–101 % with mean RSD of 1.7–3.4 % and 2.7–3.3 %, respectively. This detection method affords a number of advantages, such as being simple, rapid, and inexpensive, with low organic solvent consumption, and is remarkably free from interference effects, rendering it an efficient method for the determination of iodine in milk powder and urine samples.     

Highly sensitive chemiluminescence flow sensor for ascorbic acid

A highly sensitive chemiluminescence(CL) flow sensor is proposed for the determination of ascorbic acid. The analytical reagents luminol and iron(II) are immobilized on anion-exchange and cation-exchange resins, respectively, and can be eluted by sodium sulphate. The calibration graphs are linear in the range 1 × 10^–9 to 1 × 10^–6 g mL^–1 and the detection limit is 4.0 × 10^–10 g mL^–1. The sensor has been applied successfully to the determination of ascorbic acid in vegetables.     

Determination of cadmium,indium and zinc in nickel—base alloys by atomic absorption spectrometry with introduction of solid samples into furnaces

Atomic absorption spectrometry with an induction furnace is used for the determination of cadmium (0.002–2 μg g^-1), indium (0.6–350 μg g^-1) and zinc (0.05–26 μg g^-1) in 0.8–35 mg samples of nickel—base alloys dropped into the furnace. A resistively-heated furnace is employed for the determination of lower concentrations of indium (<0.6 μg g^-1). Standardised alloys were used for calibration. Accuracy, precision and detection limits are described for numerous nickel—base alloys. With alloys containing zinc, > 0.1 μg Cd g^-1 and >0.6 &,mu;g In g^-1, the relative standard deviations are 12%, 8% and 7%, respectively. Calculated detection limits for cadmium, indium and zinc are 2 ng g^-1, 10 ng g^-1 and 10 ng g^-1, respectively.     

Evaluation of different sample introduction approaches for the determination of boron in unalloyed steels by inductively coupled plasma mass spectrometry

An extended study of different sampling introduction approaches using inductively coupled plasma mass spectrometry (ICP-MS) is presented for the determination of boron in steel samples. The following systems for sample introduction were applied: direct sample solution nebulization by continuous nebulization (CN) using a cross-flow nebulizer and with flow injection (FI), applied to 0.1% (m/v) and 0.5% (m/v) sample solutions, respectively; FI after iron matrix extraction, using acetylacetone–chloroform, and isotopic dilution (ID) analysis as the calibration method; FI with on-line electrolytic matrix separation; and spark ablation (SA) and laser ablation (LA) as solid sampling techniques. External calibration with matrix-matching samples was used with CN, SA, and LA, and only acid solutions (without matrix matching) with FI methods. When FI was directly applied to a sample solution, the detection limit was of 0.15 μg g⁻¹, improving by a factor of 4 that was obtained from the CN measurements. Isotopic dilution analysis, after matrix removal by solvent extraction, made it possible to analyse boron with a detection limit of 0.02 μg g⁻¹ and, with the on-line electrolytic process, the detection limit was of 0.05 μg g⁻¹. The precision for concentrations above 10 times the detection limit was better than 2% for CN, as well as for FI methods. Spark and laser ablation sampling systems, avoiding digestion and sample preparation procedures, provided detection limits at the μg g⁻¹ levels, with RSD values better than 6% in both cases. Certified Reference Materials with B contents in the range 0.5–118 μg g⁻¹ were used for validation, finding a good agreement between certified and calculated values.     

Study of the preconcentration and determination of ultratrace rare earth elements in environmental samples with an ion exchange micro-column

A study was carried out on the preconcentration of ultratrace rare earth elements (REEs) in environmental samples with a micro ion-exchange column and determination by inductively coupled plasma mass spectrometry (ICP-MS). The preconcentration parameters were optimized and the REE recovery was ca. 100% in the pH range 4 to 6 with an ionic strength (μ) less than 0.18. The ion-exchange column capacity with respect to REEs was estimated as 0.96 mmol/g. The linear response coefficients ranged from 0.995 to 0.997 at the pg mL^–1 level. The concentration in the blank could be minimized (0.09 to 3.1 pg mL^–1) if the buffer solution and the water were purified. The detection limits ranged from 0.03 to 0.40 pg mL^–1, for a preconcentration factor of 100. The precision and accuracy of the method was evaluated with a synthetic standard solution and real samples. Results indicated that the REE recovery ranged from 88.1% to 100.2%, and the RSD ranged from 2.7% to 6.7%. Satisfactory results were achieved when this method was applied for the determination of REEs in raw water, purified water and tap water, as well as in environmental aquatic samples. Meanwhile, the method is simple and flexible. Received: 17 January 1997 / Revised: 23 April 1997 / Accepted: 29 April 1997     

A Novel Label Free Electrochemical Magnetoimmunosensor for Human Interleukin‐6 Quantification in Serum

A novel magnetoimmunosensor, designed for sensitive and selective quantification of interleukin 6, is herein reported. The experimental design involves the covalent immobilization of anti‐interleukin 6 antibody through an amidic bond formed with the carboxyl functionalities provided at the surface of protein G‐functionalized magnetic microparticles, assuring a sandwich‐type immunoassay with electrochemical label free detection. All the experimental parameters involved in the elaboration and testing protocol were optimized. A linear calibration plot between the charge transfer resistance and the logarithmic concentration of interleukin‐6 was achieved in the 1 pg mL^?1 to 1 μg mL^?1 range. A limit of quantification of 1 pg mL^?1 and a detection limit of 0.3 pg mL^?1 were obtained. The optimized magnetoimmunosensor showed an excellent selectivity against some potentially interfering proteins and has been successfully applied for the determination of target protein in human serum, proving its clinical relevance.     

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.     

Determination of bismuth,lead and tellurium in copper by atomic absorption spectrometry with introduction of solid samples into an induction furnace

Atomic absorption spectrometry with an induction furnace is used for the determination of bismuth (0.015–10 μg g^-1), lead (0.2–15 μg g^-1) and tellurium (0.04–5 μg g^-1) in 2–30-mg samples of copper and low-alloy copper dropped into the furnace. Calibration graphs of peak area versus mass of element were constructed by use of standardised alloys. The accuracy, precision and limits of detection of the method are described for numerous copper samples. With alloys containing more than 0.1 μg Bi g^-1, 0.2 μg Pb g^-1 and 0.8 μg Te g^-1, average relative standard deviations are 7%, 6% and 8%, respectively. The limits of detection for bismuth, lead and tellurium are 0.01, 0.1 and 0.02 μg g^-1, respectively.     

Influence of citric acid as chemical modifier for lead determination in dietary calcium supplement samples by graphite furnace atomic absorption spectrometry

Citric acid was used as a chemical modifier for Pb determination by graphite furnace atomic absorption spectrometry in dietary supplement samples (calcium carbonate, dolomite and oyster shell samples) and its efficiency was compared to the use of palladium. Pyrolysis and atomization curves were established without use of chemical modifier, with the addition of 20, 100 and 200 μg of citric acid, and with 3 μg of palladium. The citric acid modifier made possible the interference-free Pb determination in the presence of high concentrations of Ca and Mg nitrates. Acid sample digestion involving closed vessels (microwave-assisted and conventional heating) and acid attack using polypropylene vessels at room temperature were compared. All digestion procedures presented similar results for calcium carbonate and dolomite samples. However, for oyster shell samples accurate results were obtained only with the use of closed vessel systems. Analyte addition and matrix-matched standards were used for calibration. The characteristic mass for Pb using citric acid and palladium were 16 and 25 pg, respectively. The relative standard deviation (RSD) was always less than 5% when citric acid was used. The relative and absolute limits of detection were 0.02 μg g^− 1 and 8 pg with citric acid and 0.1 μg g^− 1 and 44 pg with the Pd modifier, respectively (n = 10, 3σ). The recovery of Pb in spiked calcium supplement samples (10 μg l^− 1) was between 98% and 105%. With the use of 100 μg of citric acid as chemical modifier, problems such as high background absorption and high RSD values were minimized in comparison to the addition of 3 μg of palladium.     

Removal, preconcentration and spectrophotometric determination of U(VI) from water samples using modified maghemite nanoparticles

Arsenazo III modified maghemite nanoparticles (A-MMNPs) was used for removing and preconcentration of U(VI) from aqueous samples. The effects of contact time, amount of adsorbent, pH and competitive ions was investigated. The experimental results were fitted to the Langmuir adsorption model in the studied concentration range of uranium (1.0 × 10^?4–1.0 × 10^?2 mol L^?1). According to the results obtained by Langmuir equation, the maximum adsorption capacity for the adsorption of U(VI) on A-MMNPs was 285 mg g^?1 at pH 7. The adsorbed uranium on the A-MMNPs was then desorbed by 0.5 mol L^?1 NaOH solution and determined spectrophotometrically. A preconcentration factor of 400 was achieved in this method. The calibration graph was linear in the range 0.04–2.4 ng mL^?1 (1.0 × 10^?10–1.0 × 10^?8 mol L^?1) of U(VI) with a correlation coefficient of 0.997. The detection limit of the method for determination of U(VI) was 0.01 ng mL^?1 and the relative standard deviation (R.S.D.) for the determination of 1.43 and 2.38 ng mL^?1 of U(VI) was 3.62% and 1.17% (n = 5), respectively. The method was applied to the determination of U(VI) in water samples.     

Differential pulse polarographic determination of traces of molybdenum in solar-grade silicon

After dissolution of silicon with hydrofluoric and nitric acids and matrix volatilization as hexafluorosilicic acid, 0.2 M nitric acid and 1.8 M ammonium nitrate are added to the residue. Molybdate is then determined by means of its catalytic wave in nitrate media. The limit of determination is ca. 0.1 μg g^-1 and calibration graphs are linear up to 0.2 μg Mo(VI) ml^-1.     

Voltammetric Method for the Simultaneous Determination of Melatonin and Pyridoxine in Dietary Supplements Using a Cathodically Pretreated Boron‐doped Diamond Electrode

The simultaneous voltammetric determination of melatonin (MT) and pyridoxine (PY) has been carried out at a cathodically pretreated boron‐doped diamond electrode. By using cyclic voltammetry, a separation of the oxidation peak potentials of both compounds present in mixture was about 0.47 V in Britton‐Robinson buffer, pH 2. The results obtained by square‐wave voltammetry allowed a method to be developed for determination of MT and PY simultaneously in the ranges 1–100 μg mL⁻¹ (4.3×10⁻⁶–4.3×10⁻⁴ mol L⁻¹) and 10–175 μg mL⁻¹ (4.9×10⁻⁵–8.5×10⁻⁴ mol L⁻¹), with detection limits of 0.14 μg mL⁻¹ (6.0×10⁻⁷ mol L⁻¹) and 1.35 μg mL⁻¹ (6.6×10⁻⁶ mol L⁻¹), respectively. The proposed method was successfully to the dietary supplements samples containing these compounds for health‐caring purposes.     

Determination of Fluoride in Water by Reversed-Phase High-Performance Liquid Chromatography using F−-La3+-Alizarin Complexone Ternary Complex

A method for the determination of fluoride by reversed-phase, high-performance liquid chromatography (RP-HPLC) is described. Fluoride, La³⁺ and alizarin complexone form F-La³⁺-alizarin complexone ternary complex, which is separated from the matrix on a RP, Ultrasphere C₁₈ column (250 × 4.6 mm, 5 μm) using methanol-water (19:81, v/v) mobile phase at 1.00 mL min^?1; detection at 568 nm. The calibration graph was linear from 1.0–150 ng mL^?1 for fluoride with a correlation coefficient: 0.9993 (n=6). The detection limit was 0.2 ng mL^?1. The method was successfully applied to the determination of fluoride in river and tap water. Recovery was: 94–102%, RSD in the range: 1.9 –3.6%.     

In-situ separation of chromium(III) and chromium(VI) and sequential ETV–ICP–AES determination using acetylacetone and PTFE as chemical modifiers

Electrothermal vaporization–inductively coupled plasma–atomic emission spectrometry (ETV–ICP– ES) has been used for the sequential determination of Cr(III) and Cr(VI). The method is based on the difference between the chelate reactions of the two Cr species and acetylacetone. Cr(III) chelate was separated from Cr(VI) and determined with use of acetylacetone as chemical modifier. The retained Cr(VI) in graphite tube was analyzed subsequently, after addition of polytetrafluoroethylene (PTFE) as chemical modifier. The different factors affecting the vaporization behavior of Cr(III) acetylacetonate were investigated in detail. The detection limits for Cr (III) and Cr(VI) were 0.56 and 1.4 ng mL^–1, respectively, and relative standard deviations for 0.1 μg mL^–1 Cr(III) and 0.1 μg mL^–1 Cr(VI) were 2.5% (n = 6) and 4.8% (n = 6), respectively. The linear ranges of the calibration curve for both Cr(III) and Cr(VI) covered three orders of magnitude. The proposed method was used to analyze water samples with satisfactory results.     

Analysis of Ir in Köfelsit rocks by inductively coupled plasma–sector-field mass spectrometry (ICP–SFMS)

Three different analytical strategies have been evaluated for the quantification of Ir in geological samples. Glassy rock samples from Köfels and reference material WGB-1 were analyzed directly by inductively coupled plasma sector field mass spectrometry (ICP–SFMS) at mass resolution 400 using membrane desolvation and at mass resolution 9500 without membrane desolvation. Matrix separation by anion-exchange pre-concentration was also investigated. The ultrasonic nebulizer USN6000AT⁺ (Cetac Technologies, Omaha, NE, USA) incorporating a membrane desolvation unit was used as the sample-introduction system. Sample preparation involved complete microwave-assisted acid digestion of the silicate matrix with HNO₃–HCl–HF. The results obtained by the three methods of quantification were in good agreement, showing that oxide-type interferences were effectively eliminated solely by membrane desolvation. The limits of detection were 6 pg g^–1 for low resolution measurement with use of the membrane, 15 pg g^–1 at a mass resolution of 9500, and 59 pg g^–1 for the ion-exchange procedure. The ultimate precision obtained for the Köfelsit Ir data was, however, compromised by the small sample intake (0.3 g), because of the inhomogeneous distribution of Ir in geological samples.     

Simultaneous Determination of Aluminum,Cadmium and Lead in Whole Blood by Simultaneous Atomic Absorption Spectrometry with Oxygen Charring

A method for the simultaneous determination of aluminum (Al), cadmium (Cd) and lead (Pb) in whole blood has been developed by using simultaneous atomic absorption spectrometry (SIMAAS) with oxygen charring. The optimized conditions for the simultaneous determination of Al, Cd and Pb were obtained in the presence of palladium (Pd) as the chemical modifier, using 600 °C and 2400 °C as the pyrolysis and the atomization temperature, respectively. The whole blood samples were diluted 1+5 (v/v) directly with 0.1% (v/v) Triton X‐100. Oxygen was employed to eliminate the interference of carbonaceous residues in the charring step before pyrolysis. The calibration curves were carried out with aqueous standard solutions and the linear ranges were 0–40 ng mL⁻¹, 0–4 ng mL⁻¹ and 0–40 ng mL⁻¹ for Al, Cd and Pb, respectively. The detection limits were 0.96 ng mL⁻¹ (19.2 pg) for Al, 0.03 ng mL⁻¹ (0.6 pg) for Cd and 0.60 ng mL⁻¹ (12.0 pg) for Pb. The spiked recoveries of Al, Cd and Pb in whole blood were 98.0%, 100.0% and 101.7%, respectively. The accuracy of the proposed method was evaluated with the analysis of a whole blood certified reference material (Seronorm, level 2). The found concentrations were in agreement with the recommended values. The proposed method has been successfully applied to the simultaneous determination of Al, Cd and Pb in whole blood of healthy volunteers before and after eating barbecued foods.     

Determination of total tin in silicate rocks by graphite furnace atomic absorption spectrometry

A method is described for the determination of total tin in silicate rocks utilizing a graphite furnace atomic absorption spectrometer with a stabilized-temperature platform furnace and Zeeman-effect background correction. The sample is decomposed by lithium metaborate fusion (3 + 1) in graphite crucibles with the melt being dissolved in 7.5% hydrochloric acid. Tin extractions (4 + 1 or 8 + 1) are executed on portions of the acid solutions using a 4% solution of trioctylphosphine oxide in methyl isobutyl ketone (MIBK). Ascorbic acid is added as a reducing agent prior to extraction. A solution of diammonium hydrogenphosphate and magnesium nitrate is used as a matrix modifier in the graphite furnace determination. The limit of detection is > 10 pg, equivalent to > 1 μg l^?1 of tin in the MIBK solution or 0.2–0.3 μg g^?1 in the rock. The concentration range is linear between 2.5 and 500 μg l^?1 tin in solution. The precision, measured as relative standard deviation, is < 20% at the 2.5 μg l^?1 level and < 7% at the 10–30 μg l^?1 level of tin. Excellent agreement with recommended literature values was found when the method was applied to the international silicate rock standards BCR-1, PCC-1, GSP-1, AGV-1, STM-1, JGb-1 and Mica-Fe. Application was made to the determination of tin in geological core samples with total tin concentrations of the order of 1 μg g^?1 or less.