Solid phase extraction of morphine from whole blood by means of Bond Elut Certify columns

The use of Bond Elut Certify columns for the isolation of morphine from whole blood was evaluated. In order to monitor possible losses and the elution profile of morphine, a small amount of the tritiated analogue was added to the samples. Four sample pretreatment methods, three protein precipitation methods and one sonication/dilution method, were tested. The latter one gave the best results. The blood sample was applied onto the column at pH 3.3 after sonication and dilution with 0.1 M phosphate buffer (pH 3.3). The retention of morphine was affected by the pH of the samples, and the loss of morphine during sample application was minimized at low pH (3.3). The interferences were removed by washing the column with the phosphate buffer, 0.01 M acetic acid (pH 3.3), and methanol, sequentially. Ammoniated methanol, 2 mL at 2%, was selected to elute morphine. As a result, more than 80% of 3H-morphine was recovered for concentrations of morphine ranging from 5 to 4000 ng/mL.