Determination of trace and platinum-group elements in high ionic-strength volcanic fluids by sector-field inductively coupled plasma mass spectrometry (ICP-MS)

The accurate measurement of ultra-trace concentrations of rare metals and platinum group elements in volcanic fluids is complicated by interferences, complex matrices, and preferential element partitioning. We analyzed condensed, high-temperature magmatic fluids collected from Kudryavy volcano (Kurile Islands, Russia) for Be, B, Rb, Sr, Mo, Ru, Rh, Pd, Cd, W, Re, Pt, Pb, Bi, and U using ICP-MS. The samples had three different matrices: 5 mol L^–1 sodium hydroxide (NaOH, pH = 11), gas condensates of sulfuric acid (H₂SO₄, pH = 0), and solid elemental sulfur. Interferences and suppression/enhancement effects were investigated using standards in concentrated NaOH and H₂SO₄ solutions to determine adequate dilution for sample analyses, which then required very low levels of element detection (< 1 μg L^–1 for most elements). Depending on the field sampling technique of volcanic gas vents, our results show significant differences in concentrations of some trace elements due to the precipitation of solid sulfur during gas condensation and variations in element volatility as a function of temperature.     

Sulfur speciation by capillary zone electrophoresis: conditions for sulfite stabilization and determination in the presence of sulfate, thiosulfate and peroxodisulfate

Capillary zone electrophoresis (CZE) was used for the separation of the sulfur species SO₃ ^2–, SO₄ ^2–, S₂O₃ ^2– and S₂O₈ ^2–. Using an electrolyte system with 9.5 mmol L^–1 potassium chromate as UV-absorbing probe and 1 mmol L^–1 diethylenetriamine (DETA) as electroosmotic flow modifier, various possibilities for the stabilization of sulfite and electrophoretic separation of the sulfur anions were investigated. By adding 5% propanol as a stabilizer to both the working electrolyte and the sample solution, a good stabilization for sulfite and a separation of the sulfur anions in a short analysis time (4 min) was achieved. The advantages by using propanol instead of other stabilizers often used in analytical techniques are discussed. The electrophoretic separation of the sulfur anions was optimized with respect to the pH of the working electrolyte and concentration of the electroosmotic flow modifier (DETA). The detection limits achieved for SO₃ ^2–, SO₄ ^2–, S₂O₃ ^2– and S₂O₈ ^2– were 0.35, 0.25, 0.78 and 0.80 mg L^–1, respectively. Received: 16 December 1999 / Revised: 7 March 2000 / Accepted: 14 March 2000     

Determination of sulfur in metal sulfides by bromine water-CCl4 oxidative dissolution and modified EDTA titration

The sulfur content in metal sulfides can be determined after oxidative dissolution with bromine water-CCl₄ at 50 °C by modified EDTA titration. The sulfides were quantitatively oxidized to SO₄ ^2– without evolving H₂S, and the metal cations were removed by cation exchange on an H-type column. Sulfate was precipitated as BaSO₄, and the remaining Ba²⁺ was subsequently titrated with EDTA at pH = 10. The standard deviation for the determined sulfur in the metal sulfides, some of which can be hardly dissolved in usual mineral acid media, is about a few %. The method can be carried out with sample amounts containing as little as 1.5–2 mg sulfur. Received: 31 July 1997 / Revised: 5 January 1998 / Accepted: 9 January 1998     

Determination of sulfur in metal sulfides by bromine water-CCl4 oxidative dissolution and modified EDTA titration

The sulfur content in metal sulfides can be determined after oxidative dissolution with bromine water-CCl₄ at 50 °C by modified EDTA titration. The sulfides were quantitatively oxidized to SO₄ ^2– without evolving H₂S, and the metal cations were removed by cation exchange on an H-type column. Sulfate was precipitated as BaSO₄, and the remaining Ba²⁺ was subsequently titrated with EDTA at pH = 10. The standard deviation for the determined sulfur in the metal sulfides, some of which can be hardly dissolved in usual mineral acid media, is about a few %. The method can be carried out with sample amounts containing as little as 1.5–2 mg sulfur. Received: 31 July 1997 / Revised: 5 January 1998 / Accepted: 9 January 1998     

Amperometric method for the determination of myoglobin based on the electrochemical reduction on the glassy carbon electrode

An irreversible reduction peak of oxymyoglobin (MbO₂) was observed on the bare glassy carbon electrode (GCE) in acetate buffer solution under atmospheric conditions. It is the reduction of bonded oxygen in Mb, but not the heme Fe(III)/Fe(II) redox couple that underwent electrochemical reaction on the electrode. The peak current achieved a maximum value in acetate buffer solution of pH 4.0. The peak potential was pH dependent, suggesting that the proton was involved in the electrochemical reaction. Furthermore, the peak current was linearly related to the concentration of myoglobin in the range of 2.5 × 10^–8∼ 1.0 × 10^–6 mol · L^–1 with a detection limit of 5 × 10^–9 mol · L^–1. Received: 20 March 1998 / Revised: 24 June 1998 / Accepted: 1 July 1998     

Determination of sulfur forms in wine including free and total sulfur dioxide based on molecular absorption of carbon monosulfide in the air–acetylene flame

A new method for the determination of sulfur forms in wine, i.e., free SO₂, total SO₂, bound SO₂, total S, and sulfate, is presented. The method is based on the measurement of the carbon monosulfide (CS) molecular absorption produced in a conventional air–acetylene flame using high-resolution continuum source absorption spectrometry. Individual sulfur forms can be distinguished because of the different sensitivities of the corresponding CS molecular absorption. The sensitivity of free SO₂ is about three times higher than the value for bound SO₂ and sulfate. The method makes use of procedures similar to those used in classic reference methods. Its performance is verified by analyzing six wine samples. Relative standard deviations are between 5 and 13% for free SO₂ and between 1 and 3% for total SO₂. For the validation of the accuracy of the new method, the results are compared with those of reference methods. The agreement of the values for total SO₂ with values of the classic method is satisfactory: five out of six samples show deviations less than 16%. Due to the instability of free SO₂ in wine and the known problems of the used reference method, serious deviations of the free SO₂ results are found for three samples. The evaluation of the limits of detection focuses on the value for free SO₂, which is the sulfur form having by far the lowest concentration in wine. Here, the achievable limit of detection is 1.8 mg L⁻¹. Figure Detection of non-metal elements using continuum source flame absorption spectrometry     

水系混合离子全电池LiMn2O4//NaTi2(PO4)3

分别以LiMn_2O_4,NaTi_2(PO_4)_3为正负极,1 mol·L~(-1) Li_2SO_4和0.5 mol·L~(-1) Na_2SO_4的混合水溶液为电解液组装成一种水系混合离子全电池。分别将正负极材料在3种不同水相电解液(1 mol·L~(-1) Li_2SO_4、0.5 mol·L~(-1)Na_2SO_4以及1 mol·L~(-1) Li_2SO_4+0.5 mol·L~(-1)Na_2SO_4混合电解液)中进行循环伏安和恒流充放电测试,结果发现,LiMn_2O_4在上述电解液中仅有Li~+的脱出/嵌入而Na~+由于半径较大而不参与该过程,NaTi_2(PO_4)_3在3种电解液中Li+、Na+均参与嵌入/脱嵌过程,且Li~+和Na~+的嵌入/脱出峰电位相差不大,分别为-0.82和-0.64 V,-0.95和-0.75 V;全电池在265 mA·g~(-1)电流密度下平均放电电压为1.55 V,充放电比容量分别为100.1和74.9 m Ah·g~(-1)。     

Flow injection-solid phase spectrofluorimetric determination of pyridoxine in presence of group B-vitamins

A flow-through optosensor has been prepared for the sensitive and selective determination of pyridoxine (vitamin B₆) in aqueous solutions. The sensor was developed in conjunction with a monochannel flow-injection analysis system with fluorimetric detection using Sephadex SP-C25 resin as an active sorbent substrate. This method of determination is carried out without any derivatization. The wavelengths of excitation and emission were 295 and 385 nm, respectively. When a HCl (10^–3 mol L^–1) / NaCl (3 × 10^–2 mol L^–1) solution is used as carrier solution, the sensor responds linearly in the measuring range of 5–200, 10–400 and 50–1800 ng mL^–1 with detection limits of 0.33, 0.67, and 5.70 ng mL^–1 for 2000, 1000 and 200 μL of sample volume, respectively. The relative standard deviation for ten independent determinations is less than 0.75% for 0.2 and 1.0 mL of sample volumes used, and 1.31% for 2.0 mL of sample volume used. The method was satisfactorily applied to the determination of vitamin B₆ in pharmaceutical preparations. Received: 4 June 1998 / Revised: 16 July 1998 / Accepted: 6 August 1998     

Influence of the support on the state of nickel in the Ni/SiO2, Ni/ZrO2, and Ni/SO4/ZrO2 oxide systems studied by diffuse-reflectance IR spectroscopy

The Ni/SiO₂, Ni/ZrO₂, and Ni/SO₄/ZrO₂ systems were studied by diffuse-reflectance IR spectroscopy using CO as a probe molecule. The Ni/SiO₂ and Ni/ZrO₂ systems are similar in properties, and the state of nickel in the Ni/ZrO₂ system is determined by the specific surface area. In the Ni/SO₄/ZrO₂ system, the surface sulfur compounds affect substantially the state of nickel: Ni^δ+ species with a partial positive charge are formed due to the strong electron-acceptor properties of the sulfur compounds. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 409–413, March, 1998.     

Determination of heavy metals in environmental bio-indicators by voltammetric and spectroscopic techniques

The determination of copper, lead, cadmium and zinc in matrices involved in the food chain as algae, species Ulva rigida, and clams, species Tapes philippinarum by differential pulse anodic stripping voltammetry (DPASV) was carried out. For the mercury determination in these matrices, a new accurate and precise method was developed employing a mixture of concentrated acids H₂SO₄-K₂Cr₂O₇ for digestion and subsequent cold vapor atomic absorption spectrometry (CV-AAS) by reduction with SnCl₂. The analytical procedures were verified for four reference standard materials: Ulva lactuca BCR-CRM 279, Lagarosiphon major BCR-CRM 060, Oyster tissue NBS-SRM 1566, Mussel tissue BCR-CRM 278. For all the elements the precision, expressed as relative standard deviation (s_r), and the accuracy, expressed as relative error (e), were in the order of 3 to 5%, while the detection limits were in the range 0.010–0.100 μg/g. The standard addition technique improved the resolution of the voltammetric method even in the case of very high element concentration ratios. The analytical procedure was used for real matrices sampled in the Adriatic Sea south to Po river mouth, in the zone “Goro bay”, and at open sea north to the Ravenna shore. Received: 7 June 1998 / Revised: 2 November 1998 / Accepted: 5 November 1998     

Determination of ultra-trace amounts of inorganic selenium species in natural water by ion chromatography-inductively coupled plasma-mass spectrometry coupled with nano-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> solid phase extraction

This work presents a nano-Al₂O₃ solid phase extraction technique for the determination of ultra-trace amounts of inorganic selenium species in aqueous systems using ion chromatography inductively coupled plasma-mass spectrometry (IC-ICP-MS). In this experiment, the inorganic selenium species were successfully extracted on a nano-Al₂O₃ solid phase column and then quantitative eluted with a 100 mmol L⁻¹ NaOH solution. Extraction conditions such as solvent identity, solvent concentration, solvent volume, solvent pH and salt addition were optimized. Under the optimum extraction conditions (elute solvent: 100 mmol L⁻¹ NaOH, solvent volume: 4 mL, pH: 7.0), low detection limits (Se (IV): 6 ng L⁻¹, Se (VI): 11 ng L⁻¹; RSD<5.0%) and good linear range (0.5–100 ng mL⁻¹, R² > 0.999) were obtained for all of the analytes. Good spiked recoveries over the range of 80–98% were obtained by applying the proposed method on real environmental water samples. These results indicated that this method is very sensitive and reliable when monitoring trace levels of inorganic selenium species in aqueous samples.      

Spectrofluorometric determination of hesperidin by manual and flow-injection methods

A reliable and highly sensitive method for the determination of hesperidin is described. It involves the formation of a highly fluorescent complex between hesperidin and aluminium (III) in a micellar medium. There is a linear relationship between fluorescence intensity (λ_em = 496 nm, λ_ex = 391 nm) and hesperidin concentration over the range 5 × 10^–7– 2 × 10^–5 mol L^–1. The detection limit is 79 μg L^–1. The method can easily be adapted to a flow system using a three-channel manifold, the peak height being proportional to the hesperidin concentration over the range 1 × 10^–6– 1 × 10^–4 mol L^–1. Manual and flow-injection procedures have been successfully applied to the determination of hesperidin in orange peel and orange juice. Received: 21 October 1998 / Revised: 16 December 1998 / Accepted: 25 December 1998     

Determination of p-nitroaniline by the tartrate-acetone-Mn2+-KBrO3-H2SO4 double organic substrate oscillating system using non-equilibrium stationary state

This paper described the determination of p-nitroaniline in a double organic substrate oscillating system of tartrate-acetone-Mn²⁺-KBrO₃-H₂SO₄. Under the optimum conditions, temperature was chosen as a control parameter to design the bifurcation point and proposed a convenient method for determination of p-nitroaniline. Results showed that the system consisting of 3.5 mL 0.06 mol L⁻¹ tartrate, 4.0 mL 0.7 mol L⁻¹ H₂SO₄, 1.5 mL 1.5×10⁻⁴ mol L⁻¹ MnSO₄, 4.0 mL 0.4 mol L⁻¹ acetone and 7.0 mL 0.05 mol L⁻¹ KBrO₃ was very sensitive to the surrounding at 33.5°C. A good linear relationship between the potential difference and the negative logarithm concentration of p-nitroaniline was obtained to be in the range of 2.50×10⁻⁷∼3.75×10⁻⁵ mol L⁻¹ with a lower detection limit of 2.50×10⁻⁸ mol L⁻¹.      

Laboratory and field measurements of a badge type passive sampler for the determination of ambient sulfur dioxide concentrations

The performance of a badge type passive sampler for the determination of sulfur dioxide is described. The trapping agent is triethanolamine. Analysis is performed by ion chromatography. Thus, the method allows the simultaneous detection of sulfur dioxide and nitrogen dioxide. The sampler was tested in the laboratory and in the field. The intercomparison with independent methods in the field showed very good agreement against two active sampling methods. Regression analyses (the results of the passive sampler always represent the y-axes) gave r² = 0.81 and k = 1.07 ± 0.01 for the intercomparison with an annular denuder technique and r² = 0.92 and k = 0.96 ± 0.01 for the intercomparison with a commercial fluorescence sulfur dioxide analyzer. The average reproducibility in the field was 7% (RSD). The detection limit was 0.18 μg SO₂/m³ for an exposure time of two weeks. Received: 9 February 1998 / Revised: 22 June 1998 / Accepted: 26 June 1998     

Preconcentration and voltammetric determination of palladium (II) at sodium humate modified carbon paste electrodes

A chemically modified carbon paste electrode was prepared by incorporating appropriate amounts of sodium humate(NaA). Palladium(II) was selectively accumulated in a solution of Britton-Robinson(B-R) buffer (pH 2.8) onto the electrode surface in open circuit mode. The subsequent electrochemical measurement was carried out by cyclic voltammetry (CV) and linear sweep anodic stripping voltammetry (LSASV) in a supporting electrolyte of 1.0 M HCl. The obtained oxidation currents (I_pa1 and L_pa2) were proportional to the Pd(II) concentration in the range of 4.7 × 10^–6 - 9.4 × 10^–8 M. The developed method was applied to the quantitative determination of palladium in real samples. Received: 6 March 1998 / Revised: 3 June 1998 / Accepted: 3 July 1998     

Laboratory and field measurements of a badge type passive sampler for the determination of ambient sulfur dioxide concentrations

The performance of a badge type passive sampler for the determination of sulfur dioxide is described. The trapping agent is triethanolamine. Analysis is performed by ion chromatography. Thus, the method allows the simultaneous detection of sulfur dioxide and nitrogen dioxide. The sampler was tested in the laboratory and in the field. The intercomparison with independent methods in the field showed very good agreement against two active sampling methods. Regression analyses (the results of the passive sampler always represent the y-axes) gave r² = 0.81 and k = 1.07 ± 0.01 for the intercomparison with an annular denuder technique and r² = 0.92 and k = 0.96 ± 0.01 for the intercomparison with a commercial fluorescence sulfur dioxide analyzer. The average reproducibility in the field was 7% (RSD). The detection limit was 0.18 μg SO₂/m³ for an exposure time of two weeks. Received: 9 February 1998 / Revised: 22 June 1998 / Accepted: 26 June 1998     

Automated continuous monitoring of drug dissolution process using a flow injection on-line dialysis sampling – solvent extraction separation spectrophotometric system

Inductively coupled plasma optical emission spectrometry (ICP-OES) was used for the element-specific determination of water-soluble organosilicon species separated by high-performance liquid chromatography (HPLC). Leachates from different waste deposit sites were investigated. The polydimethylsiloxane (PDMS) degradation product dimethylsilanediol (DMSD) could be detected in almost all samples in the low mg L^–1 range, and it was furthermore possible to determine trimethylsilanol (TMSOL) in some leachate samples in the μg L^–1 range. TMSOL was additionally analyzed by a method established before (LT-GC/ICP-OES). This study proved the occurrence of silanol compounds in leachates from locations were silicone material is deposited. Received: 10 July 1998 / Revised: 2 November 1998 / Accepted: 5 November 1998     

Comparison of enantioseparation of amino acid derivatives in aqueous and mixed aqueous-organic media by capillary zone electrophoresis

The chiral separation of dansyl-amino acids has been performed by capillary zone electrophoresis using ?β-cyclodextrin as a chiral selector, urea as an additive and 2-propanol and methanol as organic modifiers. The enantiomeric separations of dansyl-amino acids were investigated in aqueous medium and compared with the separation in mixed aqueous-organic medium as background electrolytes. The separation conditions, (concentration of buffer, β-cyclodextrin, methanol, urea and the pH value of buffer) were optimized. In the absence of organic modifier, only five pairs of 8 separated dansyl-amino acids were resolved when run separately. A mixture of up to eight chiral amino acids can be baseline resolved in less than 19 min by β-cyclodextrin-modified capillary zone electrophoresis with a buffer of 60 mmol L^–1 H₃BO₃-KCl/40 mmol L^–1 NaOH (pH 9.0), 4 mol L^–1 urea, 100 mmol L^–1β-cyclodextrin and 10% (v/v) methanol. Received: 15 March 1999 / Revised: 10 May 1999 / Accepted: 12 May 1999     

Conductometric Determination of Sulfur Dioxide in Wine Using a Multipumping System Coupled to a Gas-Diffusion cell

A conductometric system with a multipumping module and a gas-diffusion cell has been developed to determine free and total sulfur dioxide (SO₂) in wine. The developed method has two protocols to determine both types of SO₂ using the same system. For free SO₂, sulfite is converted to H₂SO₄ by acidification and diffusion with H₂O₂ in an acceptor channel. The sample was previously hydrolyzed by mixing the sample with NaOH and heated at 70?°C prior making the determination of total SO₂ in order to break the bonds of the combined SO₂. Free and total SO₂ were determined in the ranges of 2.5–25.4 and 10.2–76.2?mg L^?1 with a sample throughput of 13 and 12?h^?1, respectively. The calibration curves of free and total SO₂ were in the range of ΔG (mS cm^?1)?=?(–1.0242?±?0.2871)?+?(0.6613?±?0.0201) [SO₂, mg L^?1], r² of 0.997 and ΔG (mS cm^?1)?=?(–0.5850?±?0.1678)?+?(0.1236?±?0.0033) [SO₂, mg L^?1], r² of 0.997. The proposed automated method is simple and easy to apply for the determination of SO₂ in wine using simple reagents.     

Organic solvent-soluble membrane filters for the preconcentration and spectrophotometric determination of iron(II) traces in water with Ferrozine

An organic solvent-soluble membrane filter (MF) is proposed for the simple and rapid reconcentration with subsequent spectrophotometric determination of trace levels of iron (II) in water. Iron (II) is collected on a nitrocellulose membrane filter as ion associate of an anionic complex, which is formed by iron (II) and Ferrozine and a cation-surfactant. The ion-pair compound and the MF can be dissolved in small volumes of 2-ethoxyethanol and the absorbance of the resulting solution is measured at 560 nm against a reagent blank with molar absorptivity of 4.01 × 10⁴ L mol^–1 cm^–1. Beer’s law is obeyed over the concentration range 0–10 μg L^–1 of iron (II) in water and the detection limit is 0.03 μg L^–1 with a 50-fold enrichment factor. The proposed method can satisfactorily be applied to the determination of iron (II) in natural water and sea water. Received: 23 June 1998 / Revised: 21 July 1998 / Accepted: 25 August 1998