Flow-injection determination of inorganic pyrophosphate with use of an enzyme thermistor containing immobilized inorganic pyrophosphate

Inorganic pyrophosphate immobilized on controlled-pore glass is used in a simple flow enzyme thermistor system. The heat produced in hydrolysis of pyrophosphate is enhanced. by using Tris-HCl buffer, pH 7.2, containing 1 mM magnesium chloride, as carrier stream. The calibration graph is linear for 0.1–20 mM pyrophosphate; 500 assays are possible without loss of enzyme activity. For 0.5-ml injections of 10 mM pyrophosphate, the relative standard deviation was 2.0% (n=30). A single determination takes 6 min. Calcuim and strontium interfere.