Analytical element and method for determination of theophylline by enzyme inhibition
First Claim
1. A dry analytical element for the determination of theophylline in a human biological fluid, said element comprising an absorbent carrier material, a buffer which maintains the pH at 9 or less during the determination and, in fluid contact, first and second zones, said first zone containing an isoenzyme of alkaline phosphatase which is capable of acting on a substrate for said isoenzyme at a pH of 9 or less, and said second zone containing a substrate for said isoenzyme.
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Abstract
Theophylline can be determined with an analytical element, composition, kit 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 an absorbent carrier material, a suitable buffer for maintaining the pH at 9 or less, and, in fluid contact, a first zone containing an isoenzyme of alkaline phosphatase which is capable of activity at pH 9 or less, and a second zone containing a substrate for the isoenzyme. Use of this invention avoids the effect of endogenous alkaline phosphatase found in human biological fluids which has no activity at pH 9 or less.
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Citations
15 Claims
- 1. A dry analytical element for the determination of theophylline in a human biological fluid, said element comprising an absorbent carrier material, a buffer which maintains the pH at 9 or less during the determination and, in fluid contact, first and second zones, said first zone containing an isoenzyme of alkaline phosphatase which is capable of acting on a substrate for said isoenzyme at a pH of 9 or less, and said second zone containing a substrate for said isoenzyme.
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6. A dry analytical element for the determination of theophylline in a human biological fluid, said element comprising a support having thereon, in order and in fluid contact,
a first layer containing an isoenzyme of alkaline phosphatase which is capable of acting on a substrate for said isoenzyme at a pH of 9 or less, and a buffer which maintains the pH at 9 or less during the determination, a radiation-blocking layer, a subbing layer, and a porous spreading layer containing a substrate for said isoenzyme.
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9. A method for the determination of theophylline in a human biological fluid, said method comprising the steps of:
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(A) at a pH of 9 or less, physically contacting a sample of said fluid with both an isoenzyme of alkaline phosphatase which is capable of acting on a substrate for said isoenzyme at a pH of 9 or less, and a substrate for said isoenzyme, to produce a detectable change, and (B) determining said detectable change as an indication of the amount of theophylline in said biological fluid. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification