2111 1. Introduction Diabetes, which is a disease called blood sugar and oc- curs when blood sugar is very high, it always significantly affects today’s public health and quality of life. Diabetes types can generally be classified as Type 1, Type 2 and Gesta- tional diabetes. People suffering from this disease should properly use these drugs. The drugs used in the treatment of diabetes are gener- ally divided into insulins and oral tablets 1 . Metformin (MET), which is one of the oral antidiabetic drugs commonly used in the treatment of Type 2 diabetes, is a drug that increases insulin sensitivity 2–4 . In the literature, several analytical methods have been reported on MET. Most of these studies, generally using UV 5 , HPLC 6–10 , mass spectroscopy 7–8 , electrophoresis 11 , Raman spectroscopy 12 and FTIR 13 ; it relates to the determination of MET in biological fluids and pharmaceutically. Although these techniques show high sensitivity and accuracy, they have disadvantages such as the need for very expensive devices, time consuming due to various routine analysis steps, high ICNTC-2020 Special Issue J. Indian Chem. Soc., Vol. 97, No. 10c, October 2020, pp. 2111-2117 New voltammetric strategy for determination and electrochemical behaviors of Metformin by pencil graphite electrode in the NaOH Yalç n Altunkaynak a , Ömer Yavuz b and Abdulkadir Levent* c a Department of Chemistry, Science Institute, Dicle University, 21280 Diyarbakir, Turkey a Vocational School of Technical Sciences, Batman University, 72100 Batman, Turkey b Department of Chemistry, Faculty of Science, Dicle University, 21280 Diyarbakir, Turkey c Department of Chemistry, Faculty of Sciences and Arts, Batman University, 72100 Batman, Turkey E- mail: leventkadir@hotmail.com Manuscript received online 20 October 2020, revised and accepted 31 October 2020 In this study, the electrochemical properties and determination of Metformin (MET), which is one of the drugs used as an antidiabetic agent, was carried out using pencil graphite electrode (PGE) in NaOH (0.1 M) medium. This compound gave an irreversible peak of oxidation at about +1.28 V. Using square wave voltammetry in NaOH environment, the current showed a linear correlation with a concentration of 2.76–24.8 M. At a concentration of 2.76 M ( n = 9), the limit of detection (LOD) of 9.03 nM (1.495 ng L –1 ) and a relative standard deviation of 3.25% were calculated. The developed voltammetric method has been successfully applied in pharmaceutical preparations and urine samples for the determination of MET. Keywords: Metformin, pencil graphite electrode, voltammetry, drug, urine. cost, and having an experienced analyst. Electrochemical methods are generally easy and do not require expertise. In addition, the sample to be determined can be analyzed directly without any pre-processing 14–16 . Voltammetric, one of the electrochemical methods can con- fidently meet the needs in this field because they provide safe, accurate, sensitive and reproducible results in the long term 17–20 . In the literature research, it is seen that electrochemical techniques recommended for the analysis of MET in biologi- cal fluid and drug forms. Furthermore, it is appearing that the electrodes used in these studies were modified. In the study using CuMW/CNT/PE electrode, it is seen that it gives two oxidation peaks in BR (pH 7.2) 21 . For the determination of MET, it was oxidized at +0.95 V in NH 3 /NH 4 Cl (pH 8.9) by using cyclic voltammetry (CV) technique and MWCNT/PE 22 . In another study in which MET was examined using CPE in 100 mM NaOH with CV technique, the oxidation peak was observed around +0.7 V 23 . In another study investigating the electrochemical behavior of MET using CPE in PBS (pH 12.0)