Simple and fast solvent extraction system for selective and quantitative isolation of adrenaline, noradrenaline and...

A very simple solvent extraction system for the selective and quantitative isolation of adrenaline, noradrenaline and dopamine from plasma and urine is described. The extraction system makes use of the complex formation, in alkaline medium, between diphenylborate and the diol group in the catecholamines in combination with ion-pair formation. The influence of various parameters on the distribution coefficient was investigated by analysis of the liquid phases by high-performance liquid chromatography with electro-chemical detection. From these results the optimal extraction conditions can be selected. With hexane + 1% n-octanol containing 0.25% (w/v) of tetraoctylammonium bromide as extraction solvent, the catecholamines can be quantitatively isolated from plasma and urine at pH 8.6 in the presence of 0.1% (w/v) of diphenylborate. For urine the recovery was 101.5 + 1.9% for adrenaline, 100.6 +/- 2.0% for noradrenaline and 99.9 +/- 1.5% for dopamine. For plasma the recoveries were, respectively, 101.8 +/- 3.3%, 100.5 +/- 2.6% and 92.9 +/- 3.5%. The recovery of dihydroxybenzylamine, included in the study as internal standard, was determined to be 96.3 +/- 1.6% for urine and 89.9 +/- 2.7% for plasma. The applicability of the developed extraction system as clean-up and concentration step for the analysis of catecholamines in plasma and urine by high-performance liquid chromatography with electrochemical detection is demonstrated.