Tailoring the particle size of monodispersed colloidal gold

Sulfite oxidase deficiency: Studies of a patient with mental retardation, dislocated ocular lenses, and abnormal urinary excretion of S-sulfo-l-cysteine, sulfite, and thiosulfate

The paper describes a convenient, rapid, and reproducible method for the synthesis of stable dispersions of uniform gold nanoparticles at ambient temperatures by mixing aqueous solutions of tetrachloroauric acid and iso-ascorbic acid. The influence of the experimental conditions on the size of the gold particles and the stability of the final sols was monitored by dynamic light scattering and UV-vis spectrophotometry. It was found that the size of the resulting nanoparticles is affected by the concentration and the pH of gold solution, while the stability of the electrostatically stabilized final sols is strongly dependent on the excess of reductant in the system, the ionic strength, and the temperature of the precipitation. Since the preparation process does not require the addition of a dispersing agent, the surface of the resulting gold nanoparticles can be easily functionalized to make them suitable for applications in medicine, biology, and catalysis.

Stabilizer-free nanosized gold sols.

Trace metal determination by chromatography

We describe the synthesis of the lesser-known stoichiometric oxidation reagent 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (1, Bobbitt's salt), as well as of 4-acetamido-(2,2,6,6-tetramethyl-piperidin-1-yl)oxyl (2, AcNH-TEMPO). Several representative oxidation reactions are also presented to demonstrate the salt's oxidative capabilities. Bobbitt's salt has a range of applications, from the oxidation of various alcohols to their corresponding carbonyl derivatives to the oxidative cleavage of benzyl ethers, whereas 2 has been shown to serve as a catalytic or stoichiometric oxidant. The oxyl radical can be obtained in 85% yield over two steps on a 1-mole scale from commercially available 4-amino-2,2,6,6-tetramethylpiperidine (5), and is far more cost-effective to prepare in-house than purchase commercially. An additional step converts the oxyl radical into the oxoammonium salt (1, Bobbitt's salt) in 88% yield, with an overall yield of 75%. The synthesis of the salt takes ∼5 d to complete. Oxoammonium salts are metal-free, nontoxic and environmentally friendly oxidants. Preparation of 1 is also inherently 'green', as water can be used as the solvent and the use of environmentally unfriendly materials is minimal. Moreover, after it has been used, the spent oxidant can be recovered and used to regenerate 1, thereby making the process recyclable.

Synthesis of 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate and 4-acetamido-(2,2,6,6-tetramethyl-piperidin-1-yl)oxyl and their use in oxidative reactions

Application of circular thin-layer chromatography to inorganic qualitative analysis

Identification of Forty Cations and Nineteen Anions by Circular Thin Layer Chromatography.

Colorimetric Determination of Iron, Chromium, Thallium, and Aromatic and Alpha, Beta-Unsaturated Aldehydes.

Simultaneous Colorimetric Determination of Iodate and Bromate.

Ascorbic acid reacts with 2,3,5-triphenyltetrazolium chloride in alkaline medium giving pink color having 5μg/ml as visual limit of identification. This color reaction has been utilized for the colorinietric determination of ascorbic acid from pharmaceutical preparations in minute quantities. The maximum tolerable amount of other vitamins, sugars and organic compounds during determination of ascorbic acid is reported.

M. H. Hashmi

Papers

Application of circular thin-layer chromatography to inorganic qualitative analysis

Identification of Forty Cations and Nineteen Anions by Circular Thin Layer Chromatography.

Colorimetric Determination of Iron, Chromium, Thallium, and Aromatic and Alpha, Beta-Unsaturated Aldehydes.

Simultaneous Colorimetric Determination of Iodate and Bromate.

Microdetermination of ascorbic acid and tryptophan by colorimetry.