Physical Properties of Highly Active Liquor Containing Molybdate Solids

The reprocessing of irradiated nuclear fuel at Sellafield produces a nitric acid based Highly Active Liquor (HAL) waste. The liquor, containing fission products and process additives, is concentrated in an evaporator in order to reduce the volume and is then stored in Highly Active Storage Tanks (HASTs) prior to vitrification. Caesium phosphomolybdate (CPM) is precipitated during the evaporation process and can convert to zirconium molybdate (ZM) during storage.During Post Operational Clean Out (POCO) of the HASTs, it is expected that their highly active content will be reduced by repeated cycles of washing using nitric acid and other reagents. Initial washings are likely to have a chemical composition comparable to concentrated HAL, becoming more dilute during the wash-out process. It is expected that the wash-out process will also recover significant quantities of molybdate solids (ZM, CPM or a mixture) from the HASTs.In order to determine the processing challenges from such washings during POCO, the physical properties of varying concentrations of non-active HAL simulants containing molybdate solids have recently been measured by the UK's National Nuclear Laboratory. The following measurements are presented and discussed:

• •Particle size distribution
• •Density
• •Settling behaviour of solids
• •Voidage of settled sediment beds
• •Viscosity
• •Yield stress
• •Influence of ZM morphology on physical properties

     

The Importance of Effective Predevelopment Plate Washing Techniques in Thin-Layer Chromatography

Abstract

Comparative studies were made of the two methods commonly used for predevelopment TLC plate cleaning. In separate studies TLC plates were washed by the two methods: ascending development and dip washing using several solvent and solvent combinations. Residues remaining on the surface of plates after washing were visualized by fluorescence techniques and scanned by densitometry. Evaluation of the two washing methods showed that plate dipping gave superior results in every case over ascending development. The most effective solvent for predevelopment TLC plate washing was found to be methanol.     

Immunochemical Determination of Mouse and Human IgG by Adsorption on C-8 and C-18 Columns

Abstract

Human and mouse IgG are adsorbed directly on a C-8 or C-18 column, followed by reaction on-column with horseradish tagged anti-IgG. Following washing, the enzyme label catalyzes the reaction of hydrogen peroxide with tetramethyl benzidine to produce a dye, which is eluted from the column for measurement.     

The effect of washing procedures on trace element content of human hair

The effects of four washing procedures on the concentrations of manganese, iron, copper, zinc and cadmium and were investigated for three pooled samples of human head hair. The solutions evaluated were a non-ionic detergent (Triton X-100), an ionic detergent (sodium lauryl sulfate), acetone and a complexing agent (EDTA). The results indicate that for every element determined there is a level below which the concentration cannot be reduced by further washings. The numbers of washings required to reach these levels vary considerably. This effect must be considered in the trace element analysis of hair.     

FluMag-SELEX as an advantageous method for DNA aptamer selection

Aptamers are ssDNA or RNA oligonucleotides with very high affinity for their target. They bind to the target with high selectivity and specificity because of their specific three-dimensional shape. They are developed by the so-called Systematic Evolution of Ligands by Exponential Enrichment (SELEX) process. We have modified this method in two steps—use of fluorescent labels for DNA quantification and use of magnetic beads for target immobilization. Thus, radioactive labelling is avoided. Immobilization on magnetic beads enables easy handling, use of very small amounts of target for the aptamer selection, rapid and efficient separation of bound and unbound molecules, and stringent washing steps. We have called this modified SELEX technology FluMag-SELEX. With FluMag-SELEX we have provided a methodological background for our objective of being able to select DNA aptamers for targets with very different properties and size. These aptamers will be applied as new biosensor receptors. In this work selection of streptavidin-specific aptamers by FluMag-SELEX is described. The streptavidin-specific aptamers will be used to check the surface occupancy of streptavidin-coated magnetic beads with biotinylated molecules after immobilization procedures.     

Quantitative determination of sodium perborate and sodium percarbonate in detergent powders by infrared spectrometry

Sodium perborate (SPB) and sodium percarbonate (SPC) are solid compounds which act as sources of H₂O₂ in solution for stain bleaching, being considered as oxidizing agents in washing powder. This research deals with the quantitative determination of SPB and SPC by an analytical procedure based on attenuated total reflectance Fourier transform infrared spectrometry, utilizing partial least squares for data processing in the 1600-800 cm⁻¹ spectral region. The statistical parameters such as R ², standard error of prediction and relative standard deviation have been evaluated, while number of factors, number of scans and resolution were optimized. The standard deviation of method was 0.006 and 0.010 for SPC and SPB, respectively.     

Effect of high-voltage electric pulses on yeast cells: factors influencing the killing efficiency

The decisive factors determining the killing efficiency of single rectangular electric pulses of 4–28 kV cm⁻¹ amplitude and 1–300 μs duration in Saccharomyces cerevisiae S6/1 are pulse amplitude and duration, cell size and growth phase, post-pulse temperature and medium conductivity. In S. cerevisiae, the minimum pulse duration ensuring substantial killing is about 10 μs, the minimum amplitude being about 2 kV cm⁻¹. The critical pulse-induced transmembrane breakthrough voltage is 0.75 V. A pulse-induced increase in membrane permeability for small species such as inorganic ions suffices to cause cell death. A preset killing rate can be achieved by varying pulse amplitude inversely to pulse duration. Comparison of killing data on S. cerevisiae S6/1 with those on the smaller-celled Kluyveramyces lactis showed the killing pulse amplitude to be roughly proportional to cell size except for low pulse amplitudes, at which smaller cells are much more killing-prone. In exponential S. cerevisiae cells increased pulse amplitude caused a sharp increase in killing while in stationary cells this effect was much lower and occurred only at pulse amplitude above 15–20 kV cm⁻¹. Elevated post-pulse temperature lowered the killing rate whereas lowered temperature promoted it, probably by affecting the pore resealing. Lowering medium conductivity from 66 to 46 μS m⁻¹ by suspension washing reduced the killing rate by 6–20%. Reproducible killing or electroporation therefore requires standardized cell concentration, and number of cell washings.     

Sol–gel coating of cellulose fibres with antimicrobial and repellent properties

Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres were prepared from a commercially available fluoroalkylfunctional water-born siloxane (FAS) (Degussa), nanosized silver (Ag) (CHT) and a reactive organic–inorganic binder (RB) (CHT). Two different application procedures were used: firstly, one stage treatment of cotton fabric samples by FAS sol (i), as well as by a sol mixture constituted from all three precursors (Ag–RB–FAS, procedure 1S) (ii), and secondly, two stage treatment of cotton by Ag–RB sol and than by FAS sol (Ag–RB + FAS, procedure 2S) (iii). The hydrophobic and oleophobic properties of cotton fabrics treated by procedures (i)–(iii) before and after consecutive (up to 10) washings were established from contact angle measurements (water, diiodomethane and n-hexadecane) and correlated with infrared and XPS spectroscopic measurements. The results revealed that even after 10 washing cycles cotton treated with Ag–RB + FAS (2S) retained an oleophobicity similar to that of the FAS treated cotton, while the Ag–RB–FAS (1S) cotton fibres exhibited a loss of oleophobicity already after the second washing, even though fluorine and C–F vibrational bands were detected in the corresponding XPS and IR spectra. The antibacterial activity of cotton treated by procedures (i)–(iii) was tested by its reduction of the bacteria Escherichia coli and Staphylococcus aureus following the AATCC 100-1999 standard method and EN ISO 20743:2007 transfer method. The reduction in growth of both bacteria was nearly complete for the unwashed Ag–RB and Ag–RB–FAS (S1), but for the unwashed Ag–RB + FAS (S2) treated cotton no reduction of S. aureus and 43.5 ± 6.9% reduction of E. coli was noted. After the first washing, the latter two finishes exhibited nearly a complete reduction of E. coli but for the Ag–RB treated cotton the reduction dropped to 88.9 ± 3.4. None of the finishes retained antibacterial properties after 10 repetitive washings. The beneficial and long-lasting low surface energy effect of FAS finishes in the absence of Ag nanoparticles, which led to the “passive” antibacterial properties of FAS treated cotton fabrics, was established by applying the EN ISO 20743:2007 transfer method. The results revealed a reduction in bacteria of about 21.9 ± 5.7% (FAS), 13.1 ± 4.8% (Ag–RB–FAS (S1)) and 41.5 ± 3.7% (Ag–Rb + FAS (S2)), while no reduction of the growth of bacteria was observed for cotton treated with Ag nanoparticles after 10 repetitive washings. The physical properties (bending rigidity, breaking strength, air permeability) of finished cotton samples were determined, and showed increased fabric softness and flexibility as compared to the Ag–RB treated cotton, but a slight decrease of breaking strength in the warp and weft directions, while air permeability decreased for all type of finishes.     

Determination of hydrocarbons in water by evanescent wave absorption spectroscopy in the near-infrared region

An home-made EFA (evanescent field absorbance)-sensor has been tested for the determination of hydrocarbons in water. The investigations have been performed both with crude oil emulsions and petrol solutions. Cuvette and evanescent wave spectra of crude oil and petrol in the near-infrared region are presented and discussed. The concentration of aromatic compounds in crude oil can be determined semiquantitatively by the standard addition method. The sorption behaviour of the hydrocarbons in the cladding of the fiberoptic sensor has been investigated and a correlation between the sensor signal and the concentration of the aqueous hydrocarbon emulsion/solution could be shown. The desorption of the enriched molecules after the measurements is also presented. The petrol molecules evaporate in ambient air so that the sensor is easily regenerated. In case of oil measurements the hydrocarbon molecules cannot be removed by rinsing the sensor with clear water or by evaporating them in ambient air. It has to be regenerated by washing it with a high volatile solvent instead.     

Binding and Removal of Aluminum Ions in Waters by an Algal Biomass

Abstract

A preliminary study on the binding and removal of trace concentrations of aluminum ions in waters by two species of algae, Chlorella Pyrenoidosa and Chlorella Vulgaaris, were investigated. Binding by the former was minimal over all pH ranges, but binding by the latter was effective with a maximum binding of 68% occurring at pH 5. Binding was lowered drastically below pH 2, and this may be used to remove aluminum from the algae. Optimum binding occurred after 20 minutes exposure time of algae to aluminum solution and 450 mg algae mass to 100 mL solution. Binding was reproducible and more efficient in waters with low suspended solids. High salt concentrations interfere with binding, and the Chlorella Vulgaris could be reused 7 times with washings between each binding before a noticeable decrease in binding efficiency was found.     

A Simplified Neutron Activation Analysis Method for Copper and Manganese

Abstract

An activation analysis procedure has been developed to determine manganese and copper serum values in one milliliter of serum or less rapidly and with good precision. The sample is irradiated in a neutron flux of 10¹²cm^?2 sec^?1 for two hours followed by nitric acid digestion. The activity plus carrier is absorbed from saturated lithium chloride solution on Dowexl-8 contained in a syringe. After washing the resin with more lithium chloride, the syringe is counted in a five inch well crystal multichannel spectrometer. The carrier is washed off the syringe by dilute acid and analyzed. The sample concentration is determined by comparison to irradiated standards correcting the unknown for decay and chemical yield.     

Synthesis of Schiff's bases in aqueous medium: a green alternative approach with effective mass yield and high reaction rates

Abstract

Schiff's bases constitute a class of pharmaceutical and medicinally important molecules. The conventional methods for the synthesis of Schiff's bases require long reaction times and use of organic solvents. We report a novel and eco-friendly condensation reaction method permitting the “green synthesis” of various Schiff's bases by stirring 1,2-diaminobenzene with various aromatic aldehydes in water as solvent. This method is experimentally simple, clean, high yielding, green, and with reduced reaction times. The product is purified by simple filtration followed by washing with water and drying processes.     

Direct Resolution of Secondary Tert-Butylphenylphosphine Oxide

Abstract

Secondary phosphine oxides constitute an important class of organophosphorus compounds and are higly useful as versatile phosphinoylating agents and as ligands ^[1,2] They are however not readily available in the optically active form.^[3–5] We wish to demonstrate that P-chiral secondary teri-butylphenylphosphine oxide (I) can be promptly resolved into enantiomers by means of its diastereoisomeric complexes with L-O,O-dibenzoyltanaric acid (L-DBTA) Dissolution of equimolar amounts of racemic I and L-DBTA in the 4 I benzene acetone mixture yields crystalline II complex containing exclusively the R-enantiomer of the starting phosphine oxide The complexed S-enantiomer is obtained from the mother liquor by crystallization from benzene The enantiomers of I are freed from their L-DBTA complexes by simple washing with aqueous NaOH Both enantiomers of 1 of very high optical purity are thus obtained from a single batch These enantiomers have subsequently been tested for their configurational stability in selected synthetic applications.     

Elimination of Human Chorionic Gonadotropin in Sandwich Enzyme Immunoassay for Human Thyroid-Stimulating Hormone in Serum

Abstract

A method to eliminate human chorionic gonadotropin (hCG) in the sandwich enzyme immunoassay for human thyroid-stimulating hormone (hTSH) in serum is described. hTSH in serum containing hCG was reacted with dinitrophenyl monoclonal mouse anti-hTSH β-subunit IgG₁, and the complex formed between the dinitrophenyl IgG₁ and hTSH was trapped onto affinity-purified rabbit (anti-dinitrophenyl bovine serum albumin) IgG-coated polystyrene balls. hCG in the test serum was largely eliminated by washing the polystyrene balls. Subsequently, the complex on the polystyrene balls was reacted with affinity-purified rabbit anti-hCG Fab′-peroxidase conjugate followed by washing. The complex of the dinitrophenyl IgG₁, hTSH and the conjugate was eluted with dinitrophenyl-L-lysine from the polystyrene balls, to which hCG had been nonspecifically adsorbed, and was trapped onto clean polystyrene balls coated with affinity-purified rabbit (anti-mouse IgG) IgG. Peroxidase activity bound to the (anti-mouse IgG) IgG-coated polystyrene balls in the absence and presence of hTSH was not significantly affected by the presence of up to 75,000 IU of hCG per liter of serum. As a result, serum hTSH could be sensitively measured with little interference by hCG.     

LCMS/MS and TOF-SIMS identification of the color bodies on the surface of a polymer

The source of discoloration on a polymer surface can often be identified by washing the surface of the discolored polymer to collect the color bodies, then analyzing the washings using liquid chromatography-mass spectrometry (LCMS), with an in-line ultraviolet (UV) detector set at the optimum wavelength for the particular color bodies. A reference sample having no discoloration is also analyzed in the same way. In this paper, results from this methodology are compared with direct time of flight-secondary ion mass spectrometry (TOF-SIMS) analysis of a discolored polymer. The benefits and shortcomings of each methodology are discussed.     

Liquid-Solid Extraction of Vitamin D3 Metabolites from Plasma for Analysis by HPLC,GC/MS and Protein Binding Techniques

Abstract

Liquid-solid extraction of vitamin D₃ metabolites from human plasma using octadecylsilane bonded silica has been studied. Steroid-protein interactions were minimized by diluting the plasma (or serum) with two volumes of saline and passing the solution through the sorbent at 64°C. Highly purified secosteroid fractions were obtained by washing with aqueous methanol, drying the sorbent in situ with a stream of nitrogen for one minute and eluting with mixtures of hexane/chloroform. Recoveries of vitamin D₃ metabolites were essentially quantitative. Applications to the rapid analysis of 25-hydroxy- and 1α, 25-dihydroxy-vitamin D in plasma by high-performance liquid chromatography, gas chromatography-mass spectrometry or by a receptor protein assay are reported.     

Reusable Amperometric Immunosensor for the Determination of Cortisol

Abstract

A novel reusable amperometric immunosensor was developed for the determination of cortisol by co-immobilizing horseradish peroxidase (POD) and cortisol-antibody on a chemically activated affinity membrane which is mounted over the tip of an oxygen electrode. The enzymatic electrocatalytic current response to the respective substrate is inhibited by the association of the antigen to the co-immobilized antibody. The sensor can be regenerated to facilitate several assays by washing with dilute hydrochloric acid solution. The advantages of the sensor include rapid-response, simple analysis methodology and high selectivity. The calibration curve for cortisol is linear in the concentration range of 1 × 10^?7 – 1 × 10^?5M. The optimal conditions of immobilization and pH have been studied. The inhibition of enzymatic activity was confirmed by luminescence measurement utilizing the luminol- H₂O₂-POD system.     

Spectrophotometric determination of selenium(IV) with 4-methyl-<Emphasis Type="Italic">o</Emphasis>-phenylenediamine based on piazselenol formation

A method has been developed for the spectrophotometric determination of selenium(IV) using 4-methyl-o-phenylenediamine (MOPDA) as a chromogenic reagent. In hydrochloric acid media at about pH 2, MOPDA forms a piazselenol complex with selenium(IV), which gives an absorption maximum at 332 nm. After transfer of the formed piazselenol complex into organic phase with n-hexane, the absorbance of the piazselenol complex was measured by a UV-Vis spectrophotometer. The effective parameters of the experimental conditions such as pH, formation time of the complex, amount of MOPDA, ionic strength, volume of sample and effects of diverse ions, were investigated. The detection limit of the proposed method was found to be 0.95 μg/L Se(IV) (n = 14, 3σ). The method was successfully applied to tap water, sea water and wastewater samples from washings of flue gases with satisfactory results.     

Modified silica gels as recyclable adsorbents of aqueous polycyclic aromatic hydrocarbons

ABSTRACT

Polycyclic aromatic hydrocarbons (PAHs), a class of toxic organic molecules containing multiple fused aromatic rings, are found in air, soil and water as a by-product from the incomplete combustion of organic matter. We report on the modification of silica gel using lipophilic molecules containing carboxylic acids, for anchoring to the surface via hydrogen bonds. The lipophilic component captures aqueous PAH, specifically phenanthrene, through the agency of π–π and π–sp³ interactions. The structure–sorption-relationships suggest optimum phenanthrene adsorption is achieved with unsaturated bonds in linear chains or two phenyl rings. Examples include linoleic acid or 2,3-diphenylpropionic acid with removal values of 281 and 283?ng PAH per gram of silica gel, respectively. Saturation adsorption is achieved within four hours. Proposed modes of binding of the new reverse phase silica gels with phenanthrene are described. Recycling of the silica gel is accomplished by washing with organic solvents to remove PAH.     

Simultaneous Determination of Seven Toxic Trace and/or Ultratrace Metals in Environmental Plants by Differential Pulse Voltammetry Without Change of Solution and Electrode

Abstract

A simple and reliable procedure simultaneously to determine seven trace and/or ultratrace toxic metals in a single sample of environmental plants has been presented. The procedure is based on the simultaneous determination of Cu, Pb and Cd by differential pulse anodic stripping voltammetry, of Zn and Mn by differential pulse voltammetry and of Ni and Co by differential pulse adsorption voltammetry at the hanging mercury drop electrode. The details of sampling, washing and drying of samples and the approach of digestion and preparation of samples for voltammetric determination have been investigated. The method has been applied to determination of the seven metals in grass and hucerne from different environments.