Analytical element for theophylline determination using buffer in a subbing 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, a subbing zone and at least one other zone. The zones are in fluid contact with each other. The isoenzyme of alkaline phosphatase and a suitable substrate for the isoenzyme are located in different zones of the element. The subbing zone contains polyvinylpyrrolidone and a buffer for maintaining a pH of 9 or less.