Analytical element and method for theophylline determination using buffer in spreading zone

摘要

Theophylline can be determined with an analytical element and method which utilize the inhibition, by theophylline, of alkaline phosphatase activity on an appropriate substrate. The assay is carried out at a pH of 9 or less. The element comprises a porous spreading zone and at least one other zone in fluid contact with the spreading zone. The isoenzyme of alkaline phosphatase and a suitable substrate for the isoenzyme are located in different zones of the element. The element also contains a buffer for maintaining the pH at 9 or less, substantially all of which is located in the porous spreading zone.