Methyl isobutyl ketone

About: Methyl isobutyl ketone is a research topic. Over the lifetime, 2071 publications have been published within this topic receiving 26976 citations. The topic is also known as: Hexone & Isobutyl methyl ketone.

Optimisation of the derivatization in cellulose-type chiral selectors for enantioseparation by centrifugal partition chromatography.

Abstract: Cellulose was chemically modified with hydrophobic dodecanoyl groups followed by 3,5-dimethylphenylcarbamoyl substituents forming mixed ester/carbamate derivatives in order to improve the solubility in lipophilic solvents compared to the corresponding homosubstituted cellulose tris(3,5-dimethylphenylcarbamate). Two mixed derivatives of different degree of substitution were prepared, tested as chiral selectors (CSs) in counter-current chromatography (CCC) and compared to the homo-substituted derivative. Alternatively, cellulose tris(3,5-dichlorophenylcarbamate), was synthesised and tested with the same purpose. The racemic drugs pindolol and warfarin were used as test compounds. Biphasic organic/aqueous solvent systems, composed of methyl isobutyl ketone, t-butyl methyl ether or ethyl acetate and aqueous ammonium acetate or sodium phosphate buffer, were used. Centrifugal partition chromatography, a variety of CCC, in the classical elution mode and the pH-zone-refining displacement mode was applied. The enantioseparation of pindolol and warfarin was achieved in the latter conditions. The presence of dodecanoyl chains on the CS increased solubility in the organic solvents used. The selectivity of the mixed dodecanoyl/3,5-dimethylphenylcarbamoyl cellulose derivative with low degree of dodecanoyl groups (degree of substitution 0.3/degree of substitution 2.6, respectively) was similar to that of the homo-substituted derivative. Furthermore, the loading capacity for pindolol was increased by a factor of three compared to cellulose tris(3,5-dimethylphenylcarbamate). Nevertheless, the increasing degree of substitution with dodecanoyl groups on the CS, although improved solubility in the stationary phase, contributed negatively to the enantioselectivity, where warfarin was more affected than pindolol.

Determination of Trace Metals in Sodium Dithionite-Citrate Extracts of Soils and Sediments by Atomic Absorption

Abstract: A general method has been developed for the analysis of Co, Cu, Ni, Mo, and Zn in dithionite-citrate extracts of soils and sediments. Because of the high Zn content of dithionite, it is necessary to preclean the dithionite-citrate solution before it is used to extract soils or sediments. This precleaning lowers the detection level significantly for other trace elements as well. Since Fe causes flame interferences in the determination of several first transition series elements by atomic absorption, the size of the individual sample aliquot taken to chelation-solvent concentration is varied to provide a constant quantity of Fe (5,000 µg). The standards and blanks are adjusted to the same Fe content. This approach is necessitated by the wide differences in the Fe concentrations of the dithionitecitrate extracts. Following pH adjustments and addition of ammonium-1-pyrrolidine dithiocarbamate, the trace metals (and Fe) are concentrated via two successive 10-ml methyl isobutyl ketone extractions. Quantities of Fe much greater than 5,000 µg interfere in the solvent concentration step. Natural organics released by the dissolution of free-Fe and -Mn oxides, to the extent that they are represented by fulvic acids, do not cause any significant interference in the ammonium-1-pyrrolidine dithiocarbamate methyl isobutyl ketone extraction of the trace metals due to the releasing effect of the Fe present.