Carbon Paste Electrode Modified by Dibenzo 18-crown-6 for the Determination of Pb in Carrot Using Differential Pulse Voltammetry

In this research, the modification of carbon paste electrode (CPE) using dibenzo 18-crown-6 was carried out to detect Pb level in carrot. The purpose of this electrode modification is to increase the sensitivity of the measurement. The optimized parameters were scan rate, composition of dibenzo 18-crown-6 in carbon paste, and supporting electrolyte. Measurements were validated by determining the linear concentration range, detection limit (LoD), quantification limit (LoQ), repeatability, selectivity, and recovery. At the best measurement conditions, the modified CPE (CPE-Dbc) was applied to determine Pb in carrot. The optimum measurements conditions were obtained the optimum concentration of crown ether in carbon paste was 0.8%, the scan rate using CPE at 15 mV/s, increased to 20 mV/s, and H2SO4 solution as supporting electrolyte. The linear concentration was found in the range of 5-100 µg/L using CPE and became wider to 5-2000 µg/L using CPE-Dbc. The values of LoD and LoQ measurement using CPE were 0,3575 µg/L and 0,3583 µg/L, and decreased to 0,1265 µg/L and 0,1266 µg/L using CPE-Dbc. CPE and CPE-Dbc had good precision with Horwitz ratio values were 0,2231 and 0,2183, which is smaller than two. The percentage of recovery of Pb in the mixture of standard and sample solutions was (88,97 ± 2,76)%. The presence of Cu, Cd and Na in the solution did not interfere the measurement of Pb. The concentration of Pb in carrot sample was (1,8423 ± 0,0002) mg/kg, which was higher than the acceptable concentration according to SNI No. 7387:2009, which is 0,5 mg/kg.