ELEKTRODA PASTA KARBON TERMODIFIKASI BENTONIT UNTUK PENENTUAN KADAR ION LOGAM Pb(II) DAN Cd(II) PADA KUBIS UNGU (Brassica Oleracea L.) SECARA POTENSIOMETRI

Abstract

Potentiometry is an analytical technique capable of detecting analytes at very low concentrations. In this method, a carbon paste electrode (CPE) is used as the working electrode and can be modified to enhance its ability to detect analytes at trace levels. The objective of this study is to enhance the sensitivity of the CPE toward the heavy metals Pb(II) and Cd(II) by modifying the CPE with bentonite (CPEB) using potentiometry. The optimal composition of bentonite in the carbon paste is the key parameter to be optimized. Validation of the measurements includes determining the linear concentration range, detection limit (LoD), quantification limit (LoQ), and assessing accuracy, precision, and selectivity. The results indicate that the optimal bentonite compositions are 40% for Pb(II) and 45% for Cd(II). The linear concentration range for measuring Pb(II) and Cd(II) metal potentials using CPE and CPEB is 5–2000 µg/L. The LoD and LoQ values for Pb(II) ions using CPEB are higher than those using CPE, while the LoD and LoQ values for Cd(II) ions using CPEB are lower compared to CPE. The CPE and CPEB working electrodes have good repeatability, with Horwitz ratios less than two. The recovery percentages obtained were in the range of 80–110%. Selectivity coefficient values were less than one. CPEB was used to determine Pb(II) and Cd(II) concentrations in purple cabbage (Brassica oleracea L.) samples. Results showed that the purple cabbage sample contained Pb(II) at (382,10±0,04) mg/kg and Cd(II) at (510,56±0,02) mg/kg. The levels of Pb(II) and Cd(II) metals exceed the threshold based on SNI No. 7387:2009 concerning the Maximum Limit of Metal Contaminants in Fruits and Vegetables and Their Processed Products, which sets 0.5 mg/kg for Pb(II) and 0.2 mg/kg for Cd(II).