A New Method for the Determination of Creatinine in Urine Samples Based on Disposable Pipette Extraction

A method based on disposable pipette extraction (DPX) was successfully applied to creatinine determination in urine samples analysis using liquid chromatography with ultraviolet spectrophotometric detection (DPX/LC-UV). DPX variables, number of draw/eject cycles, sample pH, and type of the desorption solvent, were employed in a factorial experimental design to optimize the sorption equilibrium and time analysis. Among the evaluated DPX variables, the highest extraction efficiency was obtained with 500 µL of urine sample mixed with 1 mL of borate solution (pH 9) with one draw/eject cycle followed by liquid desorption of 1 mL of methanol in seven draw/eject cycles. The developed DPX/LC-UV method showed a linear response from the limit of quantification of 0.317 to 3.390 g L-1 with r2 = 0.996 and inter-day precision with a coefficient of variation below 8.8%. Based on these results, the proposed method can be a useful tool for determining the creatinine levels in urine samples.