Determination of Lead(II) in Liver Corpse of a Slaughtered Cattle with Preconcentration on a Chelating Sorbent
The copolymer of the maleic anhydride-styrene is modified at the presence of 4-amino-2-thiouracil and formaldehyde and the new polymeric sorbate with spatial structure is received. The received sorbate is identified by the IR-spectroscopy method. The complete static sorption capacitance was studied (CSSC+K= 7.8 mmol/g) and the ionization constants of ionic groups in a sorbate link was defined by electrometric method. Ionization constants were determined by potentiometric titration of the sorbent (). Sorption and desorption of the received sorbent with a lead ion (II) are investigated and optimum concentration conditions are defined: рНopt. = 5, ionic force μ = 0.8 pier/l, full sorption balance 4 hours, optimum eluent 5 ml of 0.5 M HCl.
Концентрирование свинца(II) хелатообразующим сорбентом, содержащим фрагменты метафенилендиамина
A   sorbent   based   on   a   copolymer   of   maleic   anhydride   with   styrene,   containing m-phenylenediamine fragments was synthesised. After drying at 50–60 ° С , the obtained sorbent was identified using IR spectroscopy. Further, a study of lead sorption by a synthesised sorbent was conducted. For this purpose, the effect of pH, time, ionic strength and metal concentration on sorption was determined. According to the experiment, the maximum sorption was established at рН = 6. Complete sorption of lead (II) wasobtained following 3 hours of metal contact with the sorbent. The effect of increase in ionic strength to 0.6 mol/L on sorption was shown to be insignificant, with a subsequent increase leading to a critical decrease in sorption value. The isotherm of lead sorption by the synthesised sorbent was constructed and the optimal concentration conditions studied. The analysis results demonstrated an increase in the concentration of lead (II) ions in the solution to provide higher values of sorbed metal concentration with the maximum occurring at a concentration of 6·10 -3 mol/L (pH = 6, С Pb +2 = 6·10 -3 mol/L, V sample = 20 mL, m sorb. = 0.05 g, CE = 405 mg/g). Under optimal conditions, the extraction degree of lead (II) ions exceeds 95 %. The study of sorption was carried out both under static and dynamic conditions. Additionally, the effect of various mineral acids (HClO 4 , H 2 SO 4 , HNO 3 , HCl) of the equal concentration on the desorption of lead (II) from the sorbent was studied. The maximum desorption of lead (II) was obtained in sulphuric acid. Thus, the proposed express technique including preliminary concentration of lead (II) with a synthesised sorbent provides quantitative isolation of lead (II) from a large sample volume with a complex background composition.
Sterol metabolism. XLI. Cholesterol A-ring autoxidations
Abstract Chromatographic and spectral evidence is adduced for the presence of cholest-5-en-3-one, cholest-4-en-3-one, and cholest-4-ene-3,6-dione in samples of cholesterol aged naturally in air or subjected to irradiation in air by 60 Co gamma radiation. These findings establish an additional mode of air oxidation of cholesterol to A-ring 3-ketones. Moreover, the oxidation by air of cholest-5-en-3-one induced by 60 Co gamma radiation yielded cholest-4-en-3-one, cholest-4-ene-3,6-dione, and the epimeric 3-oxocholest-4-ene-6-hydroperoxides. Cholest-4-en-3-one was not altered by irradiation in air, nor was cholesterol isomerized to cholest-4-en-3β-ol upon irradiation. From these observations it is deduced that the radiation-induced A-ring dehydrogenation of cholesterol yields initially cholest-5-en-3-one which upon isomerization yields cholest-4-en-3-one not further oxidized and which by a second oxidation yields the epimeric 3-oxocholest-4-ene-6-hydroperoxides which decompose to cholest-4-ene-3,6-dione.