Alcohols, analysis dodecyl

Similarly to quantitative determination of high surfactant concentrations, many alternative methods have been proposed for the quantitative determination of low surfactant concentrations. Tsuji et al. [270] developed a potentio-metric method for the microdetermination of anionic surfactants that was applied to the analysis of 5-100 ppm of sodium dodecyl sulfate and 1-10 ppm of sodium dodecyl ether (2.9 EO) sulfate. This method is based on the inhibitory effect of anionic surfactants on the enzyme system cholinesterase-butyryl-thiocholine iodide. A constant current is applied across two platinum plate electrodes immersed in a solution containing butyrylthiocholine and surfactant. Since cholinesterase produces enzymatic hydrolysis of the substrate, the decrease in the initial velocity of the hydrolysis caused by the surfactant corresponds to its concentration. Amounts up to 60 pg of alcohol sulfate can be spectrometrically determined with acridine orange by extraction of the ion pair with a mixture 3 1 (v/v) of benzene/methyl isobutyl ketone [271]. 

However, while using microemulsion as an eluent, it should be remembered that several factors such as concentration of surfactants, co-surfactants and organic phase, pH of the aqueous phase, column temperature can influence the resolution and retention of the compounds. The microemulsions described so far are based on sodium dodecyl sulphate, short-chain alcohols such as butanol and octanol and aqueous phase of different pH values [78, 159-161]. The utility of w/o microemulsions in the normal phase HPLC analysis has also been described [162]. The microemulsion liquid chromatography (MELC) has been used for resolution of several API such as paracetamol, loratidine, simvastatin, niacinamide, fosinoprilat from their impurities or degradants or metabolic products [159-162]. 

DNA Extraction and Analysis. Intracellular extrachromosomal HBV DNA was extracted from cells by the method of Hirt (256) as adopted by Gripon et al. (257). Briefly, cells were lysed in buffer containing 0.5% (w/v) sodium dodecyl sulfate (SDS), 10 mM Tris-HCl (pH 8.0), 10 mM NaCl, 10 mM EDTA and 200 /ig/ml proteinase K, and incubated overnight at 37°C. NaCl was added to the lysate to a final concentration of 1 M, and the mixture was stored overnight at 4 C to allow cellular DNA to precipitate. Chromosomal DNA was pelleted at 29,(XX) X g for 1 hr at 4°C. The supernatant was extracted twice with an equal volume of phenol chloroform isoamyl alcohol (25 24 1, v/v/v) followed by two extractions with chloroform. isoamyl alcohol (24 1, v/v). Sodium acetate (pH 5.5) was added to the aqueous phase to a final concentration of 0.3 M, and nucleic acids were precipitated with 2 volumes of ethanol. Pellets recovered after centrifugation at 29,000 x g for 10 min were dissolved in 10 mM Tris-HCl (pH 7.4) containing 1 mM EDTA. 

This is concerned not with volumetric analysis but with the sort of data that might emerge from a chromatogram or a mass spectrum. Suppose a sample consisted of five components in the following proportions. The molecular weights are consistent with an ethylene oxide adduct of dodecyl alcohol, but the proportions are not. 

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