Kinetic study and analytical application of the iodate-hypophosphite reaction in strongly acidic solutions

The iodate—hypophosphite reaction in strongly acidic solutions was studied spectrophotometrically. Reaction rate constants and the activation energy of the reaction are reported. A method for determining hypophosphite on the basis of this reaction is described. Hypophosphite in the range 0.06–4 mg (10^-3–6·10^-2 M) can be determined with a relative error and relative standard deviation of 2—3%.     

Structural Characterization of Graphene Nanosheets for Miniaturization of Potentiometric Urea Lipid Film Based Biosensors

The present article describes a miniaturized potentiometric urea lipid film based biosensor on graphene nanosheets. Structural characterization of graphene nanosheets for miniaturization of potentiometric urea lipid film based biosensors have been studied through atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements. UV‐Vis and Fourrier transform IR (FTIR) spectroscopy have been utilized to study the pre‐ and postconjugated surfaces of graphene nanosheets. The presented potentiometric urea biosensor exhibits good reproducibility, reusability, selectivity, rapid response times (～4 s), long shelf life and high sensitivity of ca. 70 mV/decade over the urea logarithmic concentration range from 1×10^?6 M to 1×10^?3 M.     

Working group report: Collider Physics

This is summary of the activities of the working group on collider physics in the IXth Workshop on High Energy Physics Phenomenology (WHEPP-9) held at the Institute of Physics, Bhubaneswar, India in January 2006. Some of the work subsequently done on these problems by the subgroups formed during the workshop is included in this report.     

Construction of a simple optical sensor based on air stable lipid film with incorporated urease for the rapid detection of urea in milk

This work describes the construction of a simple optical sensor for the rapid, selective and sensitive detection of urea in milk using air stable lipid films with incorporated urease. The lipid film is stabilized on a glass filter by polymerization using UV (ultra-violet) radiation prior its use. Methacrylic acid was the functional monomer, ethylene glycol dimethacrylate was the crosslinker and 2,2′-azobis-(2-methylpropionitrile) was the initiator. Urease is incorporated within this mixture prior to the polymerization. The presence of the enzyme in these films quenched this fluorescence and the colour became similar to that of the filters without the lipid films. A drop of aqueous solution of urea provided a “switching on” of the fluorescence which allows the rapid detection of this compound at the levels of 10⁻⁸ M concentrations. The investigation of the effect of potent interferences included a wide range of compounds usually found in foods and also of proteins and lipids. These lipid membranes were used for the rapid detection of urea in milk.     

Ultramicrodetermination of iridium by an automatic reaction-rate method

Summary An automatic spectrophotometric kinetic method is described for the ultramicrodetermination of iridium, based on its accelerating effect on the periodate photodecomposition. The time required for the reaction to consume a fixed amount of periodate is measured automatically and related directly to the iridium concentration. Ultramicroamounts of iridium in the range 80–800 ng (1.0×10^–7-1.0 x 10^–6 M) were determined with an average error of about 2%. The relative standard deviation for a 100-ppb iridium sample was 1.8%.

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Zusammenfassung Eine automatische, spektrophotometrische, kinetische Methode für die Ultramikrobestimmung von Iridium wurde beschrieben, die auf dessen beschleunigender Wirkung auf die Lichtzersetzung von Perjodat beruht. Die für den Verbrauch einer bestimmten Perjodatmenge erforderliche Zeit wird automatisch gemessen und unmittelbar in Beziehung zur Iridiumkonzentration gesetzt. 10^–7 bis 10^–6 M Iridium (80–800 ng) lassen sich auf etwa 2% genau bestimmen. Die relative Standardabweichung für 100 ppb Ir beträgt 1,8%.

     

On the singularity of Green's tensor for a perfectly conducting semi-infinite cone

This paper is intended to clarify a misunderstanding concerningthe source singularity of the electric Green's tensor for aperfectly conducting semi-infinite cone of circular cross-section.Tai's series expansion of the Green's tensor is known to lacka singular term at the source region. Jones has reconstructedthe solution to this problem and has pointed out the differencebetween his result and that of Tai. The aim of our paper isto demonstrate that, although Jones's closed-form solution iscorrect, there is a mistake in his comparison with Tai's seriessolution. We conclude that one of the two additional singularterms that Jones claims as missing from Tai's formula must beomitted. Besides, we compare Jones's closed-form solution withSmyshlyaev's solution to the very same problem. We concludethat the magnetic field expressions given by Jones and Smyshlyaevcoincide, but a singular term is missing from Smyshlyaev's expressionfor the electric field.     

A simple potentiometric method for the determination of reducing substances in urine with a copper-selective electrode

A potentiometric method for the determination of reducing substances in urine is described. Samples are treated with Stanley—Benedict reagent and the unused copper(II) is determined with a copper(II)-selective electrode by the standard addition technique. Glucose in the range 25–200 μg in 0.1ml samples can be determined with an average error of about 2%. The recovery of added glucose for six samples was 96–107% (average 100.5%). Comparison with the conventional titrimetric method shows good agreement. The effect of other non-glucose reducing substances present in urine is reported.     

A portable sensor for the rapid detection of naphthalene acetic acid in fruits and vegetables using stabilized in air lipid films with incorporated auxin-binding protein 1 receptor

The present technique describes the development of a simple sensitive spot optical test and the construction of a portable biosensor for the rapid one-shot detection of naphthalene acetic acid (NAA) using stabilized lipid films supported on a methacrylate polymer on a glass fiber filter with incorporated auxin-binding protein 1 receptor. The lipid films without the receptor provided fluorescence under a UV lamp. The use of the receptor in these films quenched this fluorescence and the colour became similar to that of the filters without the lipid films. A drop of aqueous solution of naphthalene acetic acid provided a “switching on” of the fluorescence which allows the rapid detection of this stimulant at the levels of 10⁻⁹ M concentrations. It was also possible to have quantitative data based on a calibration graph. The effect of potent interferences included a wide range of compounds. The results showed no interferences from these compounds in concentration levels usually found in real samples. The method was applied for the determination of NAA in fruits and vegetables and the reproducibility of the method was checked in about 50 samples. A quantitative method for the detection of NAA in crops that can be complimentary to HPLC methods is provided in the present paper. These lipid films can be used as portable biosensors for the rapid one-shot detection of NAA in fruits and vegetables by non-skilled personnel in the field.