FLUOROMETRIC-FLOW INJECTION DETERMINATION OF THEOPHYLLINE BASED ON ITS INHIBITORY EFFECT ON IMMOBILIZED ALKALINE-PHOSPHATASE

A fluorimetric method for the determination of low levels of theophyll ine based on the inhibition of the enzyme activity of alkaline phospha tase is proposed. The approach used is a flow-injection configuration where bovine alkaline phosphatase is immobilized on controlled pore gl ass. The enzymatic reaction is based on the hydrolysis of 1-methylumbe lliferone phosphate with fluorimetric monitoring of the 4-methylumbell iferone formed at lambda(ex) = 365 nm and lambda(em) = 445 Mn. The pre sence of theophylline in the samples inhibits the catalytic effect of alkaline phosphatase. The linear determination range was found to be b etween 0.1 and 200 mu mol l(-1), with a relative standard deviation < 3.5%. The main common interferent species in serum were tested and the y did not produce disturbance at their normal concentration in serum. The applicability of the method was checked by adding the analyte to h uman serum. The recoveries found were between 93 and 105%.