AMPEROMETRIC BIOSENSOR FOR THE RAPID-DETERMINATION OF ACETAMINOPHEN IN WHOLE-BLOOD

A method for the rapid determination of acetaminophen (paracetamol) in whole blood is described. The assay uses aryl acylamidase (E.C. 3.5.1.13) to convert acetaminophen to 4-aminophenol. The formation of 4-aminophenol is monitored amperometrically by oxidation at +250 mV vs. Ag/AgCl and the size of the integrated oxidation current (charge) is related to the concentration of acetaminophen in the sample. The reagents are incorporated into the working electrode of a disposable, single-use, screen-printed dry-strip. Measurements can be made on a 20-mu-l drop of blood within 1 min. The functional range of the assay is up to 3 mM acetaminophen, sufficient for the measurement of blood acetaminophen levels which would occur after a very large overdose. Interference is caused by elevated levels of thiols in blood, which can occur after the administration of the antidote to acetaminophen poisoning, N-acetylcysteine. To prevent this interference glutathione is incorporated into a modified design of electrode strip at a concentration which causes saturating elevation of charge values, so that any elevated concentration of thiol in a blood sample produces no further effect.