Development of electrochemical biosensor for determination of formalin in fish samples; malabar red snapper (Lutjanus Malabaricus) and longtail tuna (Thunnus Tonggol)

• Main Author: Noor Aini Bohari
• Format: Thesis
• Language: English
• Published: 2016
• Subjects: QD Chemistry
• Online Access: https://eprints.ums.edu.my/id/eprint/11316/1/Development%20of%20electrochemical.pdf

Formaldehyde is used as preservative in fish by fisherman, in order to maintain its fresh look and prevent microbial spoilage, is a big risk to consumer's health. Formaldehyde is carcinogenic. Thus a simple, sensitive and rapid device for its determination is necessary based on electrochemical biosensor coupled with an enzyme and formaldehyde dehydrogenase (FDH). A novel electrochemical biosensor was developed by depositing an ionic liquid (IL) (e.g., 1-ethyl-3-methylimidazolium trifluoromethanesulfonate; [EMIM][Otf]), ZnO nanoparticles (ZnONPs), CaO nanoparticles (CaONPs), Au nanoparticles (AuNPs) and chitosan (CHIT) on a glassy carbon electrode (GCE) for determination of formaldehyde in fish. The enzyme requires β-nicotinamide adenine dinucleotide (NAD⁺) as a cofactor which is then reduced to NADH during enzymatic reaction. Formaldehyde Dehydrogenase (FDH) was immobilized through the entrapment technique and measured based on the reduction of NAD+ under a potential of 0.4 V. The morphological characteristics of microstructures of CHIT, NPs/[EMIM][Otf]/CHIT and FDH/NPs/[EMIM][Otf]/CHIT were observed under scanning electron microscopy (SEM). Methylene blue was used as a redox indicator to increase in the electron transfer capacity and stable in both the redox reaction. The enzyme electrode showed optimum response when operated at 25°C in 50 mM Tris-HCI buffer, pH 6.5 within 5 s. The storage stability was done for 5 weeks. A relative standard deviation for the slopes of 0.32% (n = 5) was obtained for reproducibility. Under the optimal conditions, the FDH/AuNPs/[EMIM][Otf]/CHIT/GCE was showed wider linear range of formaldehyde concentrations from 0.01 to 10 ppm within 5 s, with the detection limit of 0.1 ppm. The FDH/AuNPs/[EMIM][Otf]/CHIT was found more sensitive than FDH/ZnONPs/[EMIM][Otf]/CHIT and FDH/CaONPs/[EMIM][Otf]/CHIT. FDH/ AuNPs/[EMIM][Otf]/CHIT was used for the detection of formalin on-site in fish sample; Lutjanus malabaricus and Thunnus tonggol which were found below the safety level (5 ppm). The developed biosensor is a simple, rapid, economically, highly efficient, and high accuracy when compared to the existing technique.