Investigation of Interfering Substances in Determination of Creatine by the Folin method.

Abstract

We have previously reported that there was a great difference between urinary creatine values obtained by our enzymatic method and by the Folin method. In order to clarify causes of the discrepancy, specificity of the both methods was investigated.
A satisfactory recovery of creatine addewsd to urine specimens suggested that substances other than creatine did not interfere with the enzymatic method.
On the other hand, guanidinoacetic acidand guanidinosuccinic acidwhi chmight occur in urine specimens were demonstrated to give positive error in the Jaffé reaction when treated with hydrochloric acid under the conditions of creatine determination by the Folin method. The reason why guanidinoac etic acid and guanidinosuccinic acid gave the positive error in the Folin method was also discussed.