Studi penggunaan kurkumin sebagai modifier elektroda pasta karbon untuk analisis timbal (II) secara stripping voltammetry

ABSTRAK Studi untuk mengetahui kemampuan kurkumin sebagai modifier elektroda pasta karbon untuk mendapatkan analisis timbal (II) yang mudah, murah, sensitif, dan memiliki limit deteksi yang rendah telah dilakukan. Analisis timbal (II) dilakukan secara voltametri pelucutan kembali (stripping voltammetry). Modifikasi elektroda pasta karbon dilakukan dengan metode bulk modified, yakni dengan mencampurkan grafit, minyak parafin dan kurkumin dengan perbandingan 3:4:3, 3:3:4, dan 3:2:5. Pengukuran dilakukan dengan mencelupkan elektroda ke dalam sel voltametri yang berisi 25 mL larutan timbal (II) dan larutan elektrolit KCl 0.05 M dalam buffer asetat. Pengukuran dilakukan dalam dua tahapan. Tahap pertama yaitu tahap deposisi, dilakukan pada potensial -0.6 V dengan variasi pH 3, 4, 5, 6, 7, 8 dan variasi waktu deposisi 0, 15, 30, 60, 120 detik. Tahap kedua adalah tahap stripping, pada tahap ini dilakukan variasi kecepatan scan pengukuran 5, 10, 20, 30, 40, 50 mV/detik. Daerah konsentrasi linier diselidiki pada rentang konsentrasi 0-70 ppb. Adanya gangguan logam lain seperti tembaga (II) dan kadmium (II) diselidiki. Respon arus puncak timbal (II) diberikan oleh elektroda pasta karbon termodifikasi kurkumin pada -0,493 V vs Ag/AgCl (KCl jenuh). Komposisi elektroda terbaik adalah dengan perbandingan grafit : minyak parafin : kurkumin = 3:2:5, dimana timbal (II) dapat terukur pada skala ppb secara differential pulse voltammetry. Kondisi optimum pengukuran diperoleh pada buffer asetat pH 4, waktu deposisi 60 detik, dan kecepatan scan 10 mV/detik. Daerah konsentrasi linier diperoleh pada rentang konsentrasi 4,995 – 49,504 ppb dengan limit deteksi 1,3438 ± 0,0096 ppb dan R2 = 0,9966. Interferensi dari logam tembaga (II) dan kadmium (II) mempengaruhi arus puncak timbal (II) masing-masing sebesar 59,60 % dan 56,74%. Kata kunci : timbal (II), voltametri, kurkumin, elektroda pasta karbon. ABSTRACT Curcumin was studied to know its abilities as modifier of carbon paste electrodes to reach a low cost, simple, good sensitivity, and low detection limit for lead (II) analysis. Lead (II) analysis was done by stripping voltammetry. Carbon paste electrodes were modified by bulk modified method, where weighed amounts of graphite powder, paraffine oil, and curcumin were mixed in 3:4:3, 3:3:4, and 3:2:5. The electrode was dipped into a voltammetric cell which was filled with 25 mL solution of lead (II) and KCl 0.05 M as supporting electrolyte in acetate buffer for measurements. The measurements were done in two steps. The first step was deposition, it was done at potential -0.6 V with pH variation of 3, 4, 5, 6, 7, 8 and deposition time variation of 0, 15, 30, 60, 120 s. The second step was stripping, it was done by variation of scan rate 5, 10, 20, 30, 40, 50 mV/s. A linier range was studied at concentration 0-70 ppb. Interference from another metal ions such as copper (II) and cadmium (II) in lead (II) analysis were also studied. Voltammetric responses of lead (II) were resulted by carbon paste electrodes modified with curcumin at potential -0.493 V vs Ag/AgCl (saturated KCl). The best composition of electrodes were the electrodes with weighed amounts of graphite powder: paraffine oil: curcumin in 3:2:5, where the measurements of lead (II) showed good results in ppb by differential pulse voltammetry. The optimum operating conditions and parameters were achieved on pH 4 of acetate buffer, in 60 s of accumulation time, and on 10 mV/s of scan rate. A linier concentration area of lead (II) was in range of 4.995 – 49.504 ppb with lower detection limit on 1.3438 ± 0.0096 ppb and correlation factor 0.9966. Copper (II) and cadmium (II) interferenced the peak current of lead (II) 59.60% from copper (II) and 56.74% from cadmium (II). Keywords : lead (II), voltammetry, curcumin, carbon paste electrode