Direct assay for creatine kinase by reversed-phase high-performance liquid chromatography

A direct assay for creatine kinase (CK) activity was developed based on the separation and quantitation of adenosine triphosphate (ATP) by high-performance liquid chromatography. The total incubation time is 13 min and the elution time for ATP is 16 min. Using lyophilized CK as the sample, a sensitivity in the range of 8 U/l (units/liter) was obtained. The method presented also has clinical significance in that CK levels in serum can easily be determined with minimal sample preparation. Using serum samples from a healthy patient and a heart attack victim, activities of 26.6 U/l and 609.0 U/l, respectively, were obtained. Because of the direct measurement of ATP, this method eliminates the coupled reactions encountered in the common spectrophotometric and colorimetric methods of analysis resulting in a simpler and inexpensive assay.