An Eco-Friendly alternative for voltammetric determination of creatinine in urine sample using copper(II) immobilized on biochar

Abstract

Creatinine (CRE) is the final product of creatine and phosphocreatine metabolism in mammals. CRE is primarily excreted by the kidneys, and a decrease in urinary creatinine content can be an indicator of kidney failure. Therefore, monitoring this biomarker in urine samples is crucial. For this purpose, an electrochemical sensor had been proposed for indirect determination of the target based on the immobilization of copper ions on biochar, an eco-friendly material. First, copper ions (Cu2+) were spontaneously preconcentrated at the surface of a biochar-modified carbon paste electrode. Next, CRE was spontaneously accumulated over this surface, resulting in the suppression of the copper voltammetric signal. This suppression was attributed to the formation of a creatinine-copper complex, and used as the analytical response. A linear dynamic range (LDR) of 300–700 µmol L−1 in the presence of a synthetic urine matrix was achieved, along with limits of detection (LOD) and quantification (LOQ) of 91.0 µmol L−1 and 300 µmol L−1, respectively. Selectivity was suitable for the most common metallic species found in urine and equimolar uric acid concentration. The standard addition method was adopted for CRE determinations in synthetic urine samples, and the recoveries values were 101 ± 7 % for the method's limit of quantification (LOQ) concentration (300 µmol L−1), and 100 ± 7 % for the usual creatinine concentration in urine after a dilution step, 500 µmol L−1. Therefore, an approach based on metal immobilization, using an eco-friendly material, was proposed for indirect creatinine determination, and successfully applied to biomarker analysis in a synthetic urine matrix.