Determination of theophylline based on monitoring the oxidation intermediate by a stopped-flow kinetic spectrophotometric method

A new stopped-now kinetic spectrophotometric method for determination of reactants based on monitoring the signal change of intermediates for successive reactions is proposed. Using this method,we have determined theophylline based on monitoring the maximum absorbance(lambda=525nm)of the oxidation intermediate using a stopped-now technique. A mechanism explaining this method is discussed. Results show that this method is simple,fast and free from the interference of other alkaloid derivatives especially caffeine,which always coexists with theophylline. The linear range is 5.0x10(-5)-3.5x10(-3)mol/L of theophylline with detection limit of 4.5x10(-6)mol/L.