Tujuan penyelidikan ini adalah untuk menentukan pemilihan membran nilon-6 berasaskan biosensor elektrokimia bagi mengesan asid askorbik (AA). Membran nilon-6 disintesis daripada manik nilon-6 (polimer) pada 18wt%, 76wt% asid formik (pelarut) serta 6wt% metanol sebagai bukan pelarut. Dalam kajian ini, kesan kepekatan asid askorbik (80Mm, 60mM, 40mM, 20mM dan 10mM) dan pemilihan bagi peratusan isipadu yang berlainan bagi asid sitrik (CA) kepada AA (0/100, 15/85, 30/70, 70/30, 85/15 dan 100 / 0) telah dinilai melalui Cyclic Voltammetry (CV) dan Electrochemical Impedance Spectroscopy (EIS). Membran nilon-6 juga telah dicirikan dengan menggunakan Scanning Electron Microscopy (SEM), Fourier-Transform Infrared (FTIR) dan porometer untuk menentukan permukaan morfologi, kumpulan berfungsi dan ciri-ciri liang membran. Hasil SEM menunjukkan membran nilon-6 dengan liang-mikron yang terpapar pada permukaan membran. Sementara itu, hasil FTIR menunjukkan bahawa membran yang mempunyai kumpulan fungsi membran nilon-6 yang utama manakala porometer mendedahkan taburan saiz liang yang sempit. Berdasarkan analisis elektrokimia membran melalui CV, didapati bahawa semakin tinggi kepekatan AA, semakin tinggi arus dikesan. Begitu juga, untuk ujian pemilihan, semakin tinggi peratusan isi padu AA, semakin besar arus puncak terhadap AA. Kepekatan AA dan pemilihan CA kepada AA didapati berkadar terus secara linear dengan arus puncak, masing-masing dengan nilai R2 iaitu 0.9897 dan 0.9379. Tambahan pula, keputusan EIS untuk semua sampel campuran CA dan AA telah ditunjukkan dalam garisan secara linear, yang membuktikan rintangan yang lebih rendah untuk pemindahan caj elektron dengan peningkatan kinetik untuk pemindahan ion. Akhirnya, dengan menggunakan lengkung penentukuran, kepekatan AA dan jumlah peratusan AA dalam sampel sebenar, buah oren masing-masing adalah 1.94 mM dan 2.33 v%.
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The aim of this research is to determine the selectivity of nylon 6 membrane-based electrochemical biosensor to detect ascorbic acid (AA). The nylon 6 membrane is synthesized from nylon 6 beads (polymer) at 18wt%, 76wt% of formic acid (solvent) as well as 6wt% of methanol as the non-solvent. In this work, the effect of AA concentration (80Mm, 60mM, 40mM, 20mM and 10mM) and selectivity for different volume percentage of citric acid (CA) to AA (0/100, 15/85, 30/70, 70/30, 85/15 and 100/0) were evaluated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The nylon 6 membrane has also been characterized using scanning electron microscopy (SEM), fourier-transform infrared (FTIR) and porometer to determine the surface morphologies, functional group and pore characteristics of the membrane, respectively. SEM result shown nylon-6 membrane with micron-pores distributed on the membrane surface. Meanwhile, FTIR results indicated that the membrane possess with important functional group of nylon-6 membrane and porometer revealed narrower pore size distribution. Based on the electrochemical analysis of membrane through CV, it was found that the higher the concentration of AA, the higher the current detected. Similarly, for selectivity test, the higher the volume percentage of AA, the higher the current peak for AA. Concentration of AA and selectivity of CA to AA were found linearly proportional to the peak current, with R2 of 0.9897 and 0.9379, respectively. Furthermore, EIS results for all mixed samples of CA and AA had demonstrated in linear lines, which indicate lower resistance for electron charge transfer with increased kinetic for the ions transfer. Finally, by using the calibration curve, the concentration of AA and the percentage volume of AA in the real sample, orange fruit was found to be 1.94 mM and 2.33 v%, respectively.
Determine the selectivity of membrane - based electrochemical biosensor to detect ascorbic acid / Nur Najwa Syazwani Awang