Continuous separation of Sr, Y and some actinides by mixed solvent anion exchange and determination of 89,90Sr, 238,239Pu and 241Am in soil and vegetation samples

Methodology for the determination of ^89,90Sr, Am and Pu isotopes in complex samples is given. Methodology is based on simultaneous isolation of Sr, Y and actinides from samples by mixed solvent anion exchange chromatography, mutual separation of ^89,90Sr and ⁹⁰Y from actinides, mutual separation of Th, Pu and Am by extraction chromatography, quantitative determination of ^89,90Sr by Cherenkov counting and quantitative determination of Pu and Am isotopes in soil and vegetation samples by alpha spectrometry. It is shown that Y and Sr can be efficiently separated from alkaline, alkaline earth and transition elements as well as from lanthanides and actinides on the column filed by strong base anion exchanger in nitrate form and 0.25?M HNO₃ in mixture of ethanol and methanol as eluent. It is also shown that Pu, Am and Th strongly binds on the mentioned column, can be separated from number of elements and easily be eluted from column by water. After elution actinides were mutually separated on TRU column and electrodeposited on stainless steel disc. Examination of conditions of electrodeposition was shown that chloride-oxalate electrolyte with addition of DTPA in presence of sodium hydrogen sulphate in cell with cooling and rotating platinum anode enables deposition of actinides within 1?h by 0.8?A?cm^?2 current density. Obtained peaks FWHM for Pu, Am and Th isotopes are between 27 and 40?keV. Scanning electron microscopy picture and ED XRF analysis of electroplated discs showed that actinide deposition is followed by iron oxide formation on disc surface. The methodology was tested by determination of ^89,90Sr, Am and Pu isotopes in ERA proficiency testing samples (low level activity samples). Obtained results shows that ^89,90Sr, ²⁴¹Am and ^238,239Pu can be simultaneously separated on anion exchange column, ^89,90Sr can be determined by Cherenkov counting with a satisfactory accuracy and limit of determination within 1?C3?days after separation. ²⁴¹Am and ^238,239Pu can easily be separated on TRU column and determined after electrodeposition with acceptable accuracy within 1?day.     

Optimization and characterization of a sulfate based electrodeposition method for alpha-spectrometry of neptunium and curium

The parameters for a sulfate based electrodeposition method were optimized for the preparation of Cm and Np alpha-spectrometry sources. Alpha-spectrometry requires the preparation of essentially massless sources to eliminate self-absorption of alpha-particles, which can cause degraded alpha-spectra. A variety of methods for the electrodeposition of actinides have been reported in the literature, many of which require long deposition times and lack reproducibility. A previously reported sulfate based method has been evaluated for the preparation of Np and Cm sources. High yields were achieved and source preparation took 90 minutes or less. The effects of electrodeposition time and pH of the depositing solution were evaluated for each element. Typical resolution (FWHM) for sources prepared by this method is 50 keV or less with recoveries approaching 100%.     

The reduction of ferricyanides and a sensitive test for the detection of hydrogen peroxide

Yellow zinc ferricyanide is reduced by heating to white zinc ferrocyanide by hydrogen peroxide in the presence of zinc sulphate and sodium, acetate. Copper ferricyanide, however, is reduced to brown copper ferrocyanide at room temperature, by means of hydrogen peroxide in the presence of copper sulphate and sodium acetate. The latter reaction can be applied for the detection of extremely small quantities of hydrogen peroxide both in a test tube (2.5 γ in 1 ml) and as a spot test (0.5 to 1 γ).     

The detection of nitrate using in-situ copper nanoparticle deposition at a boron doped diamond electrode.

Electrochemical deposition from a 0.1 M sodium sulphate solution, containing Cu2+ (adjusted to pH 3 with hydrochloric acid) produced a well defined copper nanoparticle deposit on the surface of a boron doped diamond electrode. Changing conditions such as potential (-0.8, -1.0 and -1.2 V), time (5, 2 and 0.5 s) and concentration of Cu2+ (500, 250 and 100 microM) was found to give copper nanoparticles of varying size and particle density. The electrocatalytic properties of the copper surface towards nitrate reduction were explored. An in-situ copper nanoparticle production method was developed for the detection of nitrate; this involves electrodeposition, followed by linear sweep voltammetry for the reduction of nitrate and then application of a stripping potential to renew the electrode surface. The linear sweep was discovered to have homogenised the size of the nanoparticles but their number density was still dependant on the initial conditions of deposition. Some particles were still present at the surface after the stripping potential had been applied but repetitions of the procedure showed these did not have an effect on subsequent deposits. Optimisation of the method lead to applying a deposition potential of -0.8 V, at a BDD electrode for 5 s in a 0.1 M sodium sulphate solution (pH 3) containing 100 microM Cu2+ followed by a linear sweep at 1 V/s; this yielded a limit of detection of 1.5 microM nitrate. The analytical applicability of the technique was evaluated for nitrate detection in a natural mineral water sample and was found to agree well with that stated by the manufacturer.     

Preliminary results on the immobilisation of radionuclides from waters with specific adsorbers based on phosphate salts

The present paper is focused on the ability of aluminium phosphate (ALPC), magnesium ammonium phosphate (MGPC), magnesium hydrogen phosphate (MGHPC), and calcium hydrogenphosphate (CAHPC), adsorbed onto charcoal, to immobilise actinides by adsorption from natural waters. The objective of this process is to evaluate the environmental pollution due to the actinides. Europium, thorium, protactinium, neptunyl, and uranyl ions were chosen to simulate actinides in the +3, +4, +5 and +6 oxidation state. The adsorbers were tested using natural waters samples. The adsorption trends and capacities were analysed. ALPC and MGPC exhibited a similar behaviour and adsorbed demonstrating that the +5, +4 and +3 actinide ions can be easily immobilised from natural waters and may be successfully used at pH 7-8. MGHPC may be used at a higher pH, whereas CAHPC is effective in the whole pH range. In all cases, thorium, protactinium and europium were strongly     

Chemiluminescence high-performance liquid chromatography for the determination of hyaluronic acid, chondroitin sulphate and dermatan sulphate.

A sensitive chemiluminescence high-performance liquid chromatographic method has been developed for the determination of hyaluronic acid, chondroitin sulphate and dermatan sulphate as their unsaturated disaccharide-dansylhydrazine derivatives involving an effective sample clean-up system. The dansylhydrazones of the unsaturated disaccharides derived from the hyaluronic acid, chondroitin sulphate and dermatan sulphate by chondroitinase ABC and/or chondroitinase ACII, were separated by reversed-phase chromatography using a mixture of 0.1 M sodium acetate buffer (pH 6.0) and 80% acetonitrile on a column (250 mm x 4.0 mm I.D.) packed with amide-80 silica beads (5 microns diameter). For post-column elution in the chemiluminescence system, 1 mM bis[2-(3,6,9-trioxadecanyloxycarbonyl)-4-nitrophenyl]oxalate and 3mM hydrogen peroxide in acetonitrile were used. The detection limit of each glycosaminoglycan was 100 fmol. The method was applicable to the determination of the levels of hyaluronic acid, chondroitin sulphate and dermatan sulphate in rat peritoneal mast cells.     

The influence of complexing agents on the effectiveness of electrochemical masking with anionic surfactants in anodic stripping voltammetry

The influence of sodium dodecyl sulphate, sodium dodecyl sulphonate and sodium stearinate on the anodic stripping peaks of Tl(I), Pb(II), Cd(II), Cu(II) and In(III) was investigated. The supporting electrolytes were 0.5M sodium sulphate solution, 0.2M citrate solution (pH 3.7, 4.6 and 7.3), 0.5M tartrate solution (pH 4.4) and 0.1M solution of EDTA (pH 4.4). The composition of complex compounds forming in a solution under experimental conditions was defined. The conditions of ion reduction of metals on hanging mercury electrode during the electrolytical deposition were investigated. The investigation included an analysis of voltammetric curves of the metal ions. The obtained results suggest that "electrochemical masking" is much stronger in electrolytes containing a complexing agent than in the sodium sulphate solution. The influence of the complexing agent may not be explained in terms of the interaction between the form of the complex and the charge of the adsorbed surfactant particles; rather the complexing process is connected with indirect inhibition, i.e., by decreasing the rate of charge transfer reaction.     

Purification and Partial Properties of a Superoxide Dismutase from Agave Hybrid No.11648

A superoxide dismutase enzyme was extracted from the leaves of Agave Hybrid No.11648 using homogenisation, ammonium sulphate fractional precipitation, diethylaminoethyl cellulose ion exchange and Sephadex gel filtration chromatography. A superoxide dismutase parallelogram‐shaped crystal was formed after packing at 4 °C for two days. The optimum pH was 8, and the optimum temperature was 40 °C. The crystal was relatively stable at temperatures below 60 °C and at pH values from 5 to 10. The subunit size was determined to be approximately 27.5 kDa by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis. It was also demonstrated that the enzyme is an iron‐containing superoxide dismutase based on its sensitivity to inhibitors of potassium cyanide, hydrogen peroxide and chloroform‐ethanol and based on the results of ultraviolet absorption spectroscopy.     

Sulphate determination after its reduction to hydrogen sulphide and volatile separation by molecular absorption spectrometry

A rapid spectrophotometric method for sulphate determination in a discontinuous mode is described. The method is based on sulphate reduction to hydrogen sulphide followed by its volatilization and absorption in an alkaline solution. The reduction is obtained when a sulphate sample is heated to 287 degrees C for 15 min, with a mixture of Fe(o)/KI and phosphoric acid. The resulting gas is swept by nitrogen flow into a 0.1 M sodium hydroxide solution and the absorbance of the sulphide ions is measured directly at 230 nm. The proposed method enabled us to determine 50-700 mug of total sulphate with a relative standard deviation of the order of 5%. The method has been applied for the determination of sulphates in liquid (mineral waters) and solid (gypsiferous soils) samples.     

Electrosorption impedance on Pt(111) in sulphuric media and nature of the “unusual” state

Impedance measurements, up to 1 MHz, not only in sulphuric acid but also with supporting electrolytes for H⁺ or for anions, confirmed that the usual peaks on Pt(111) are related to a fast hydrogen electrosorption, and that the “unusual” state is due to sulphate anion electrosorption on the whole pH range, or to hydrogenosulphate at low pH and to sulphate above pH 2.     

Investigations of reactions involved in flameless atomic absorption procedures: Part VI. A Study of some factors influencing the determination of lead in sulphate matrices

The degree of interference from various sulphates in the determination of lead by flameless a.a.s. is high (e.g. the decrease in the signal from lead is 10% for 2 nanomol of sodium sulphate) and decreases in the order sodium ? potassium ? calcium ? magnesium. The interference from magnesium sulphate can be eliminated by ashing the sample at 870 ± 10°C. Results obtained from high-temperature equilibrium calculations show that gaseous lead sulphide is responsible for the interferences in the presence of sodium sulphate. Theoretical conditions for the formation of gaseous lead sulphide are outlined. The influence of carbon on the reactions involved was investigated by use of standard graphite as well as glassy carbon tubes; the results are compared with those found theoretically. In the presence of a tenfold excess of lanthanum(III), the recovery of lead is higher than 90% for all the sulphates investigated, at least up to an amount of 0.2 μ mol. The addition of oxygen as well as hydrogen to the inert gas decreases the interference from sodium sulphate, in accordance with the theoretical predictions.     

Differential pulse polarographic study of the hydrolysis of endosulfan and endosulfan sulphate in emulsified medium. Application to the determination of binary mixtures of organochlorine pesticides

Hydrolysis reactions of endosulfan and endosulfan sulphate in the emulsified medium formed with ethyl acetate and a mixture of the two surfactants Hyamine 2389 and Triton X-405 are studied by differential pulse polarography. Besides the heptachlor-endosulfan sulphate pair, whose peak potentials are sufficiently different at pH 8.0 to allow their simultaneous determination, the organochlorine pesticide binary mixtures endosulfan-endosulfan sulphate, dieldrin-endosulfan and dieldrin-endosulfan sulphate can be determined based on their hydrolysis reactions in basic medium and on their different reaction rates. The endosulfan-endosulfan sulphate pair can be determined by allowing the mixture to hydrolyse at pH 11.0 and measuring the endosulfandiol peak for the determination of endosulfan. The analysis of the mixture dieldrin-endosulfan is based on endosulfan hydrolysis at pH 12.0 in which dieldrin is not hydrolysed. Dieldrin and endosulfan sulphate can also be determined simultaneously in a 0.5M sodium hydroxide medium. When determining one pesticide in binary mixtures containing a 5.0 x 10(-6)M concentration of the other pesticide, the lower limits of the calibrations obtained were: endosulfan-endosulfan sulphate mixture, 4.0 x 10(-6) and 1.0 x 10(-6)M respectively; heptachlor-endosulfan sulphate mixture, 2.0 x 10(-6)M for endosulfan sulphate; all other cases, 3.0 x 10(-6)M.     

Hexacyanoferrate(III) as a mediator in the determination of total iron in potable waters as iron(II)-1,10-phenanthroline at a single-use screen-printed carbon sensor device

Hexacyanoferrate(III) was used as a mediator in the determination of total iron, as iron(II)-1,10-phenanthroline, at a screen-printed carbon sensor device. Pre-reduction of iron(III) at −0.2 V versus Ag/AgCl (1 M KCl) in the presence of hexacyanoferrate(II) and 1,10-phenanthroline (pH 3.5-4.5), to iron(II)-1,10-phenanthroline, was complete at the unmodified carbon electrode surface. Total iron was then determined voltammetrically by oxidation of the iron(II)-1,10-phenanthroline at +0.82 V, with a detection limit of 10 μg l⁻¹.In potable waters, iron is present in hydrolysed form, and it was found necessary to change the pH to 2.5-2.7 in order to reduce the iron(III) within 30 s. A voltammetric response was not found at lower pH values owing to the non-formation of the iron(II)-1,10-phenanthroline complex below pH 2.5.Attempts to incorporate all the relevant reagents (1,10-phenanthroline, potassium hexacyanoferrate(III), potassium hydrogen sulphate, sodium acetate, and potassium chloride) into a modifying coated PVA film were partially successful. The coated electrode behaved very satisfactorily with freshly-prepared iron(II) and iron(III) solutions but with hydrolysed iron, the iron(III) signal was only 85% that of iron(II).     

Incorporation of Tetrazolium Blue (TB)/Gold Nanoparticles (GNPs) into Carbon Paste Electrode: Application as an Electrochemical Sensor for the Sensitive and Selective Determination of Sotalol in Micellar Medium

The electrochemical oxidation of Sotalol (SOT) based on Tetrazolium Blue (TB)/gold nanoparticles (GNPs)‐modified carbon paste electrodes (CPE) have been studied in the presence of sodium lauryl sulphate (SLS). Cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry and electrochemical impedance spectroscopy (EIS) techniques have all been utilized within this study. GNPs and TB have a synergetic effect‐giving rise to highly improved electrochemical responses and provide an advantageous platform for the basis of an electrochemical sensor with excellent performance. The experimental parameters, electrodeposition time, pH and scan rate have all been examined and optimized. The sensing of SOT via DPV is found to exhibit a wide linear dynamic range of 1.0×10⁻⁷–7.5×10⁻⁴ M in pH 2. LOD and LOQ were calculated and found to correspond to 2.5×10⁻⁸ M and 8.3×10⁻⁸ M, respectively. The suggested sensor has been used successfully for SOT determination in pharmaceutical samples and human urine as real samples. Satisfactory recoveries of analyte from these samples are demonstrated indicating that the suggested sensor is highly suitable for clinical analysis, quality control and a routine determination of SOT in pharmaceutical formulations.     

Precipitation of lead as lead sulphate by destructive oxidation of EDTA

Gravimetric determination of lead (5–100 mg) by homogeneous precipitation of lead sulphate from a solution containing lead(II), EDTA and sulphate by destructive oxidation of EDTA with hydrogen peroxide or sodium bromate is described. Aluminium(III), iron(III), zinc(II), manganese(II), copper(II), nickel(II), tin(II) and antimony(III) do not interfere in the method. The method can successfully be applied to the analysis of type metal.     

The determination of microgram amounts of sulphur in nitrate or chloride solutions

It is shown that μg quantities of sulphate can be “collected” with barium chromate when the latter is precipitated from solutions at a pH of about 1. The sulphate in this precipitate can be converted to hydrogen sulphide when the precipitate is treated at red heat with a mixture of hydrogen and hydrogen chloride vapour. The above procedure has been made the basis of a method for determining traces of sulphur, down to about 0.2 p.p.m. on a 10 g sample, when the hydrogen sulphide is determined absorptiometrically as Lauth's violet.     

Studies for simultaneous quantitative electrodeposition of plutonium and americium for alpha-spectrometry

For high resolution alpha-spectrometric studies, the sources of alpha-emitting actinides are generally prepared by electrodeposition. Usually, by electrodeposition of only one element can be achieved quantitatively. A method was developed for the simultaneous quantitative electrodeposition of plutonium and americium, in two hours using 0.005M oxalic acid with saturated ammonium chloride. The alpha-spectral characteristics of sources prepared by this method were better than those prepared by the drop deposition method. This electrodeposition procedure was validated with nuclear fuel samples containing plutonium and americium.     

Response Surface Optimization of the Critical Medium Components for Pullulan Production by <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis> FB-1

Culture conditions for pullulan production by Aureobasidium pullulans were optimized using response surface methodology at shake flask level without pH control. In the present investigation, a five-level with five-factor central composite rotatable design of experiments was employed to optimize the levels of five factors significantly affecting the pullulan production, biomass production, and sugar utilization in submerged cultivation. The selected factors included concentration of sucrose, ammonium sulphate, yeast extract, dipotassium hydrogen phosphate, and sodium chloride. Using this methodology, the optimal values for concentration of sucrose, ammonium sulphate, yeast extract, dipotassium hydrogen phosphate, and sodium chloride were 5.31%, 0.11%, 0.07%, 0.05%, and 0.15% (w/v), respectively. This optimized medium has projected a theoretically production of pullulan of 4.44%, biomass yield of 1.03%, and sugar utilization of 97.12%. The multiple correlation coefficient ‘R’ was 0.9976, 0.9761 and 0.9919 for pullulan production, biomass production, and sugar utilization, respectively. The value of R being very close to one justifies an excellent correlation between the predicted and the experimental data.     

Structure and Activity of RNase A in Sodium Dodecyl Sulphate Solutions

The structure and activity of RNase A in sodium dodecyl sulphate solutions were investigated at 25.0±0.1 and pH 7.00. The results show that with increasing sodium dodecyl sulphate concentration, the structure of RNase A is collapsed gradually, however, the activity of RNase A is first increased and then decreased. This is mainly due to the different effect of SDS at different SDS concentration.     

An electrode for the coulometric generation of hydrogen ion

The anodic generation of hydrogen ion on bright platinum in 1.0M sodium perchlorate is not quantitative owing to the formation of a chemical species With oxidizińg properties, presumably a peroxydiperchlorate, but 100% current efficiency can be obtained in the anodic generation of hydrogen in 0.25M sodium hydrazinium sulphate, Na(N(2)H(5))SO(4). Five hydrogen ions are formed for each four electrons passed. The efficiency of this "hydrazine-platinum anode" has been demonstrated by the high-precision coulometric titration of tris(hydroxymethyl)aminomethane.