Anal. Methods Environ. Chem. J. 6 (2) (2023) 55- 70 Research Article, Issue 2 Analytical Methods in Environmental Chemistry Journal Journal home page: www.amecj.com/ir AMECJ Modifed carbon paste electrode based on nanotechnology for determining phenol in the liquid solutions by cyclic voltammetry and comparing to high-performance liquid Chromatography Khalil Ibrahim Alabid a ,* and Hajar Naser Nasser a a Department of Chemistry, Faculty of Science, Tishreen University, Syria ABSTRACT In this paper, phenol was determined in a liquid solution based on fabricating a phenol-selective electrode by cyclic voltammetry (CV). The carbon paste electrode was modifed with nickel oxide nanoparticles (NiO) which were doped with nitrogen carbon quantum dots (NCQD) as the NiO-NCQD nanocomposite. The modifed carbon paste electrode was manufactured in a laboratory and the efect of pH was studied. In the optimized condition, the best results were created at pH 7.0 and 4.0 using KH 2 PO 4 bufer solution. By voltammetry, the voltage was optimized, and the best value for the voltages was obtained at 0.04166V and 0.05991V for pH 4 and 7, respectively. The scan rate (SR) was studied and the best SR was achieved at 100 mv s -1 for both pH. Due to the results, a wide linear dynamic range between 10 to 1000 μM was obtained. Also, the standard phenol solution was analyzed by high-performance liquid chromatography (HPLC). The retention time (RT), the wavelength maximum (λ max: nm), and the peak area equation of HPLC were achieved at 2.982 min, 270 nm, and (Area=40420C Phenol + 43.557), respectively by the concentration range of 0.1-5.0 mg L -1 . The modifed carbon paste electrode with NiO- NCQD was used for determining phenol by cyclic voltammetry and compared with the HPLC technique. The results showed that there was no signifcant diference between the two methods. Keywords: Phenol, Cyclic voltammetry, Modifed carbon paste electrode, Nickel oxide Nanoparticles, High-performance liquid chromatography ARTICLE INFO: Received 15 Feb 2023 Revised form 26 Apr 2023 Accepted 22 May 2023 Available online 28 Jun 2023 *Corresponding Author: Khalil Ibrahim Alabid Email: khalilibrahimalabid@gmail.com https://doi.org/10.24200/amecj.v6.i02.240 ------------------------ 1. Introduction Phenol is an aromatic organic compound [1-2], it has the formula C 6 H 6 O [3], phenolic compounds are widely found in water, soil, and air. These compounds are not biodegradable [4], which are dangerous compounds, it is found everywhere in the environment, including in aerosols due to combustion emissions [5]. It is very toxic [6-8], phenol and its derivatives are pollutants [9], when a person is exposed to phenol for long periods, it enters his body through inhalation, ingestion, or through direct contact with the skin, and causes severe damage such as: including damage to the liver, kidneys, urinary and reproductive tracts, lungs, shortness of breath, neurological problems, severe abdominal pain, irritation of the digestive system, nausea, vomiting, diarrhea, and sweating, Coma and death. The lethal dose of phenol is ingestion of 1 g [10 -14]. Phenol disrupts endocrine function and, in addition, causes cancer [15], the maximum permissible level of phenol according to the world health organization (WHO) that its concentration does not exceed 0.1 µg L -1 in drinking water [16]. Phenol oxidizes to give an electron and a proton,