A polarographic method for fluoride

A polarographic method is proposed for the determination of fluoride, based on the action of fluoride on a complex formed between thorium and o-nitrobenzenearsonic acid. Increasing amounts of fluoride liberate increasing amounts of the organic compound, of which the polarographic wave is utilised. The wave-height therefore increases with increasing amounts of fluoride, in contrast to existing polarographic methods for the ion.     

Rapid polarographic method for the microdetermination of organically- bound phosphorus

An indirect polarographic method for the microdetermination of phosphorus in organophosphorus compounds is described. Alkaline hypobromite is used as oxidizing absorbent. Quinoline phosphomolybdate is precipitated with a measured excess of standard molybdate solution. The unreacted Mo(VI) is determined polarographically. Nitrogen, chlorine, bromine and sulphur do not interfere. One determination takes 40 min. The results obtained fall generally within the acceptable limits of error.     

Rapid polarographic method for determining arsenic in steel

A simple and sensitive polarographic method for determining arsenic in steel is presented. The steel is dissolved in HNO(3), and arsenic reduced with Na(2)S(2)O(5)-K.I. The polarographic wave is recorded for an electrolyte at pH 3.0 and containing Fe(II), Mn(II). citric and ascorbic acids. Levels of 0.2% and 0.003% As can be determined with a coefficient of variation of +/- 6%.     

一种高效、洁净的还原醛的新方法

报道了在超临界CO2中，实现氢转移反应的新方法，这一方法以水为氢授体， 锌粉为电子授体，高选择性地还原对甲基苯甲醛为相应的醇，并初步研究了反应温 度、反应体系中CO2的压力、反应时间对还原反应的转化率的影响。     

Rapid polarographic method for determination of arsenic in ferrotungsten

A simple and sensitive method for determining arsenic in ferrotungsten is presented. The alloy is dissolved in aqua regia and the arsenic reduced with K(2)S(2)O(5). The polarographic wave is recorded for an electrolyte at pH 3.0 and containing Fe(II), Mn(II), citric acid and ascorbic acid. Levels of 0.2%, and 0.003% As can be determined with errors of +/- 8 and +/- 20% respectively. The limit of detection is 0.003%.     

Assessment of a new method for the differential pulse polarographic determination of silicon in steel

A procedure is described by which silicon in steel may be determined by differential pulse polarography after removal of iron. Silicomolybdic acid is formed within 20 min by reaction of the silicon with molybdate in the presence of methyl ethyl ketone: subsequent addition of citrate buffer prevents interference from phosphate and excess of molybdate. At the levels present in high-purity iron ( approximately 0.002%) the precision for silicon is better than that usually quoted for the molybdenum blue method. The steel is dissolved by standard procedures but iron must be removed before the silicon is determined. The lower limit imposed by the polarography is about 10(-5)% silicon, but the practical lower limit is probably set by the difficulty of removing the last traces of iron.     

A new simple sensitive differential pulse polarographic method for the determination of acrylamide in aqueous solution

A new simple sensitive differential pulse polarographic (DPP) method was investigated for the determination of acrylamide (AA) directly in a neutral aqueous solution. The AA showed a well-defined and well-resolved peak in pure aqueous LiCl at −1.84 V in the potential range from −1.6 V to −1.97 V at nitrogen pressure of 0.5 kg cm⁻². Among the various electrolytes studied, the AA showed good DPP response in the presence of LiCl and tetra methyl ammonium iodide, while it showed poor response in the presence of tetra butyl ammonium hydroxide and tetra butyl ammonium bromide due to their strong adsorption on the surface of electrode which hindered its reduction. The effect of LiCl concentration, the cyclic voltammetric response and the drop time study showed that AA exhibited an irreversible adsorptive electrochemical behavior. The good electrochemical response in pure aqueous medium suggested that hydrogen bonding might be involved which may favor the electrode reaction. Under optimized conditions, the peak current was linear in the entire concentration range from 0.2 mg L⁻¹ to 20 mg L⁻¹ with the correlation coefficient of R² = 0.9998. The method showed good reproducible results with R.S.D. of 0.3% (n = 16). The detection limit (LOD) was 27 μg L⁻¹. The influence of various interfering agents was also studied. The method was applied successfully for the quantification of AA in water samples without any interference effect from alkali metals.     

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.     

Rapid method for the preparation of a robust optical pH sensor

A simple and rapid method for the preparation of a fluorescence-based optical pH sensor is described. The sensor is based on excitation ratiometric detection of a methacryloyl-modified analog of the well-known fluorescent pH indicator dye, 8-hydroxy-1,3,6-pyrene trisulfonic acid (HPTS). The modified dye, 6-methacryloyl-8-hydroxy-1,3-pyrene disulfonic acid (MA-HPDS), is similar in structure and function to HPTS. However, unlike HPTS, the presence of the methacrylate moiety allows MA-HPDS to participate as a comonomer in a free radical polymerization reaction. Covalent immobilization by this method is simple, as the preparation of the modified dye is accomplished in a single reaction step and its subsequent reaction with a comonomer results in simultaneous immobilization and purification. Sensors were prepared by copolymerization of the MA-HPDS with poly(ethylene glycol) diacrylate. Minimal leaching of the immobilized dye was observed from the HPDS-PEG matrix. The copolymer of HPDS and PEG-DA is fully autoclavable. The sensor is useful over the pH range of 6-9, with excellent reproducibility. Ionic strength effects on the apparent pKa of the immobilized dye are small and predictable.     

A novel method for the assay of alpha-glucosidase inhibitory activity using a multi-channel oxygen sensor.

The quantification of glucose by using a multi-channel dissolved oxygen (DO) meter (DOX96) with immobilized glucose oxidase (GOD) and mutarotase (MUT) was performed. An evaluation of the inhibitory activities for alpha-glucosidase (AGH) by modifying our batch-type pseudo-in vivo assay system [Oki et al.; Biol Pharm. Bull., 2000, 232, 1084] was also performed using a DOX96. When 45 U/well GOD and 18.75 U/well MUT were immobilized on the surface of a gelatin membrane on the electrodes, the response shown by the decrease percent of DO (%) obtained with 8 electrode wells in the same row was linear with the glucose concentration up to 3.3 mM and a correlation coefficient larger than 0.9. To estimate the AGH inhibitory activity, AGH-immobilized Sepharose supports in the well of a silent screen plate were used. The IC50 values of acarbose and 1-deoxynojirimycin, a medicinal inhibitor for diabetes, were 0.70 +/- 0.08 microM and 0.40 +/- 0.13 microM, respectively, and coincided well with those by a pseudo-in vivo assay.     

A polarographic study of dihydronaphthoxazoles

The polarographic behavior of four dihydronaphthoxazoles that have not been studied previously has been investigated. It has been shown that the dihydronaphthoxazoles are reduced at higher positive potenials than the corresponding diaryloxazoles because of the increase in conjugation of the substituent in position 5 with the oxazole nucleus. The mechanism of the reduction of dihydronaphthoxazoles is similar to that of the reduction of diaryloxazoles.     

The polarographic behaviour of the 1,4-benzodiazepines, oxazepam and lorazepam, and a method for quality control

The polarographic behaviour of the drugs, oxazepam and lorazepam, has been investigated over a wide pH range. Different types of wave are obtained depending on the pH. The pK_a, values calculated are in good agreement with those obtained from u.v. spectroscopic measurements. For analytical purposes, the optimal pH is 4.7 (acetate supporting electrolyte), the 4-electron reduction wave being measured. A quality control method for the two drugs in different formulations containing 0.5–15 mg of active constituent is described.     

A polarographic study of dihydronaphthoxazoles

The polarographic behavior of four dihydronaphthoxazoles that have not been studied previously has been investigated. It has been shown that the dihydronaphthoxazoles are reduced at higher positive potenials than the corresponding diaryloxazoles because of the increase in conjugation of the substituent in position 5 with the oxazole nucleus. The mechanism of the reduction of dihydronaphthoxazoles is similar to that of the reduction of diaryloxazoles.     

A method for determination of hydrogen content in uranium dioxide samples using a semiconductor sensor

Measurements of H₂ content in UO₂ samples have been carried out on the basis of a technique using a hydrogen sensitive sensor of Pd–SiO₂–Si. A specially made set up allowed to register the amount of H₂ in UO₂ samples up to 10^–10, g. Measured H₂ content in investigated samples was 8, 32 and 102 ppb (mass) at 400, 800 and 1600°C, respectively.