Multivariate Calibration for the Determination of Creatine in Urine Using UV Absorption Spectroscopy

A reagent-free Partial Least Squares (PLS)-based analysis of creatine in urine using UV absorption spectroscopy is described. Creatine and creatinine standards were used to demonstrate the feasibility of the method, giving plots of predicted versus actual values which had R² values of 0.999. Fifty-six individual urine samples, some collected over 24 hours and some collected over shorter time periods, were analyzed by HPLC, and their UV absorption spectra from 200 to 310 nm were run and used for calibration of a PLS-based analysis. Plots of predicted versus actual concentration had R ² values of 0.967 for creatine, but only 0.874 for creatinine.