Development of electrochemicalbiosensor for determination offormalin in fish samples; malabarred snapper (Lutjanus Malabaricus) andlongtail tuna (Thunnus Tonggol)
2016
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.
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