Solvent extraction and QSPR of catecholamines with a bis(2-ethylhexyl) hydrogen phosphate

In order to develop an effective separation process for catecholamine (CA), a basic investigation on solvent extraction of dopamine (DA), adrenaline ( Ad) and noradrenaline (NA) from hydrochloric acid solution and their stripp ing is conducted at 30 degrees C employing bis(2-ethylhexyl) hydrogen phosp hate (D2EHPA) in chloroform, n-hexane and toluene as the organic diluents. From the dependencies of the distribution ratios on the concentrations of r eactant species, i.e. CA, hydrogen ion and D2EHPA, it is elucidated that CA (RNH2) is extracted with D2EHPA (HR') according to the ion exchange mechan ism, as the complex type, RNH3R'(HR')(3), and the equilibrium constants (K- ex,CA) for the extraction reactions are also evaluated. The quantitative st ructure property relationship (QSPR) of K-ex,CA values for each organic dil uent is discussed using molecular modeling with semi-empirical molecular or bital calculations considering the solvent effect.