LIQUID-CHROMATOGRAPHIC DETERMINATION OF THE ADENOSINE RECEPTOR AGONIST CGS-21680 IN BLOOD USING ONLINE SOLID-PHASE EXTRACTION ON A PHENYLBORONIC ACID SUPPORT AND FLUORESCENCE DETECTION

An analytical method is described for the selective determination of A , or A, adenosine receptor agonists in blood. By implementing solid-ph ase extraction using immobilized-phenylboronic acid (PBA) in sample pr etreatment, all adenosine derivatives' are retained via their intact c is-diol group. On-line desorption of the analytes from the PBA support to the C,, analytical column is performed by injection of a small plu g of perchloric acid. Fluorescence and UV detection are employed for t he different adenosine derivatives. The method is applied to the deter mination of )phenylethylamino]-5'-N-ethylcarboxyamidoadenosine (CGS 21 680, I) in blood using fluorescence detection. The only off-line sampl e handling step is the extraction of blood with ethyl acetate and subs equent evaporation of the extraction solvent. The detection limit of t he method was 0.25 ng (signal-to-noise ratio 3:1) and the determinatio n limit for I in blood (pretreatment of 100 mu l) was 5 ng/ml. The met hod was validated and used to study the pharmacokinetics of I in rats.