Indirect kinetic spectrophotometric determination of hydroxylamine based on its reaction with iodate.

A simple, precise and accurate method is proposed for rapid determination of trace amounts of hydroxylamine based on the reaction of hydroxylamine with iodate in acidic media. The reaction of neutral red by the produced nitrite ion was used to monitor the reaction spectrophotometrically at 525 nm by a fixed time method. Hydroxylamine in the range of 0.0400-1.200 microg mL(-1) could be determined. The relative standard deviation for 10 determinations of 0.500 microg mL(-1) hydroxylamine was 1.81% and the limit of detection was 0.010 microg mL(-1). The proposed method was applied to the determination of hydroxylamine in water samples with satisfactory results.     

Synthesis of New Dibenzosulfide and Dibenzosulfoxide Macrocyclic Compounds

Some new dibenzosulfo, dibenzosulfoxo macrocyclic diamides are synthesized.     

Simultaneous kinetic-spectrophotometric determination of hydrazine and acetylhydrazine in micellar media using the H-point standard addition method.

The H-point standard addition method (HPSAM), based on a spectrophotometric measurement for the simultaneous determination of hydrazine and acetylhydrazine, is described. This method is based on the difference between the rates of their reactions with N,N-dimethylaminobenzaldehyde (DAB) in the presence of sodium dodecyl sulfate (SDS) in acidic media. The results showed that hydrazine and acetylhydrazine could be determined simultaneously in the range of 0.020 - 0.70 and 0.20 - 5.0 mg L(-1), respectively. Under the working conditions, the proposed method was successfully applied to the simultaneous determination of hydrazine and acetylhydrazine in several synthetic mixtures and plasma and water samples.     

Syntheses of 5‐alkylthio‐1,3‐diaryl‐1,2,4‐triazoles

Arylation of the readily available 3‐alkythio‐5‐aryl‐1,2,4‐triazoles gave 5‐alkylthio‐1,3‐diaryl‐1,2,4‐triazoles in moderate yield. The structures of the latter were confirmed by NOE and ¹³C‐NMR.     

Hyers-Ulam-Rassias stability of homomorphisms in quasi-Banach algebras associated to the Pexiderized Cauchy functional equation

In this paper, we prove the Hyers-Ulam-Rassias stability of homomorphisms in quasi-Banach algebras associated to the Pexiderized Cauchy functional equation. This is applied to investigate homomorphisms between quasi-Banach algebras. The concept of Hyers-Ulam-Rassias stability originated from Th.M. Rassias' stability theorem that appeared in his paper [Th.M. Rassias, On the stability of the linear mapping in Banach spaces, Proc. Amer. Math. Soc. 72 (1978) 297-300].     

Crystallographic report: Bis{µ‐[O‐cyclopentyl(4‐methoxyphenyl)dithiophosphonato]1κ:S,2κ:S‐[O‐cyclopentyl(4‐methoxyphenyl)dithiophosphonato]‐1κ2S,S′}dicadmium(II)

The centrosymmetric title compound, [Cd₂{CH₃OC₆H₄P(OC₅H₉)S₂}₄], features an eight‐membered [? Cd? S? P? S? ]₂ ring owing to the presence of bridging dithiolate ligands. Tetrahedral coordination geometries for cadmium are completed by chelating ligands. Copyright © 2004 John Wiley & Sons, Ltd.     

Headspace SPME–GC Method for Acetone Analysis and its Biomedical Application

A new method for extraction and analysis of acetone in human urine based on headspace solid phase microextraction using a mixture of activated carbon and zeolite as sorbents in a PVC matrix coated on a silver wire and its application to the determination of ketone bodies is described. Unlike commercial fibers, which are coated on fused silica, the coating adheres strongly to the silver wire and is thermally stable up to 250 °C. After optimization of coating composition and microextraction conditions the fiber was used for the analysis of acetone in human urine.     

A turbidimetric method to measure isoelectric points and particles deposition onto massive substrates

A simple experimental approach was developed to determine the adhesion rate of particles onto massive substrate. Turbidimetry measurements are used to follow the evolution of particle concentration in a suspension in dynamic contact with the walls of a vessel made of different materials. This method allows to rapidly obtain qualitative results about the adhesion of metallic oxides particles on massive substrates. Adhesion of particles of charged latex onto glass was used to validate the approach and was shown to be a method to determine isoelectric points (IEP) of massive substrates. Then, the adhesion of an iron oxide (hematite) particles onto several substrates was studied to determine the reactivity of current labware (glass, polypropylene) and on a metal (aluminum) commonly found in industrial fouling problems. Adhesion of hematite was found to be pH-dependant, and occurs only below ca. 6 (glass) or 7 (polypropylene), and above 7 (aluminum). DLVO calculations were performed to model the hematite/water/glass system and are consistent with the experimental results. Experiments at temperature 7–50 °C have shown an increasing of the adhesion rate from 7 to 40 °C, then a constant value until 50 °C.