Separation of the non-volatile noble metals by reversed-phase extraction chromatography.
The procedure involves the use of tri-n-butyl phosphate (TBP) adsorbed by Porasil C and stepwise elution with sulphuric acid and hydrochloric acid. The distribution coefficients for the two systems (TBP and hydrochloric acid and TBP and sulphuric acid) and the elution characteristics were studied. A description is given of a procedure applicable to the analysis of prills obtained from the fire assay of platinum-bearing ores.
Extraction chromatography of noble metals with use of mixtures of hydrochloric and nitric acid as mobile phases.
The chromatographic behaviour of the platinum metals and gold, silver and copper on paper strips treated with liquid anion-exchangers and eluted with mixtures of HNO(3) and HCl was investigated. It was found that increase of HNO(3) concentration in the acid mixture increases the R(F) values more significantly than does that of HCl. The presence of HNO(3) in the development solution prevents the reduction of iridium(IV). The R(F) values of the noble metals increase in the order Au(III) < Os(IV) < Ir(IV) < Pt(IV) < Pd(II) < Ru(III) < Rh(III) approximately Ir(III). Several separations of noble metals were carried out on paper strips treated with trioctylamine or quaternary alkylammonium salts, as well as the column separation of the mixture PtPdRh. The proposed chromatographic systems seem to be especially useful for the separation of non-volatile noble metals.
Mechanism of the depressor response to dopamine in the rat treated with phenoxybenzamine.
Alterations of hypotensive responses to dopamine by antagonists were characterized in alpha-blocked, anaesthetized rats. Responses were not affected by d-propranolol (0.1 mg/kg) whereas d,1-propranolol (0.1 mg/kg) or haloperidol (1.0 mg/kg) attenuated them; higher doses of inhibitors (1.0 mg/kg; 5.0 mg/kg, respectively) failed to produce a higher inhibition, but combinations of low doses abolished the depressor responses. In adrenalectomized rats, hypotensive responses decreased; haloperidol always attenuated the responses while d,1-propranolol became ineffective. Dopamine produced an enhancement of plasma adrenaline and noradrenaline levels, which was decreased by d,1-propranolol and increased by haloperidol. The data suggest that in rats the depressor component of dopamine is due to activation of both dopaminergic and beta-adrenoceptors. The beta component appears to be due to the release of adrenaline. The results also support the concept of the existence in sympathetic nerve endings and adrenal glands of stimulatory beta-adrenergic and inhibitory dopaminergic prejunctional receptors.