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3 results on '"Ling-Ling Tan"'

1. Highly Sensitive Fluorescence Sensor for Carrageenan from a Composite Methylcellulose/Polyacrylate Membrane

Author

Ling Ling Tan, Riyadh Abdulmalek Hassan, and Lee Yook Heng

Subjects
Letter, 02 engineering and technology, 010402 general chemistry, lcsh:Chemical technology, 01 natural sciences, Biochemistry, Analytical Chemistry, fluorescence sensor, chemistry.chemical_compound, lcsh:TP1-1185, Electrical and Electronic Engineering, Instrumentation, chemistry.chemical_classification, Detection limit, Acrylate, Chromatography, Polymer, polymer blend, 021001 nanoscience & nanotechnology, Atomic and Molecular Physics, and Optics, 0104 chemical sciences, Carrageenan, Membrane, chemistry, Reagent, carrageenan, methylene blue, Polymer blend, 0210 nano-technology, Methylene blue
Abstract

Carrageenans are linear sulphated polysaccharides that are commonly added into confectionery products but may exert a detrimental effect to human health. A new and simpler way of carrageenan determination based on an optical sensor utilizing a methylcellulose/poly(n-butyl acrylate) (Mc/PnBA) composite membrane with immobilized methylene blue (MB) was developed. The hydrophilic Mc polymer membrane was successfully modified with a more hydrophobic acrylic polymer. This was to produce an insoluble membrane at room temperature where MB reagent could be immobilized to build an optical sensor for carrageenan analysis. The fluorescence intensity of MB in the composite membrane was found to be proportional to the carrageenan concentrations in a linear manner (1.0–20.0 mg L−1, R2 = 0.992) and with a detection limit at 0.4 mg L−1. Recovery of spiked carrageenan into commercial fruit juice products showed percentage recoveries between 90% and 102%. The optical sensor has the advantages of improved sensitivity and better selectivity to carrageenan when compared to other types of hydrocolloids. Its sensitivity was comparable to most sophisticated techniques for carageenan analysis but better than other types of optical sensors. Thus, this sensor provides a simple, rapid, and sensitive means for carageenan analysis.

Published
2020

2. Electrochemical Biosensor for Nitrite Based on Polyacrylic-Graphene Composite Film with Covalently Immobilized Hemoglobin

Author

Raja Zaidatul Akhmar Raja Jamaluddin, Kwok Feng Chong, Lee Yook Heng, and Ling Ling Tan

Subjects
02 engineering and technology, Biosensing Techniques, Electrochemistry, lcsh:Chemical technology, 01 natural sciences, Biochemistry, Reference electrode, Article, Analytical Chemistry, Matrix (chemical analysis), chemistry.chemical_compound, Hemoglobins, Succinimide, lcsh:TP1-1185, Electrical and Electronic Engineering, Nitrite, nitrite, Instrumentation, Electrodes, Nitrites, edible bird’s nest, Detection limit, electrochemical biosensor, graphene, hemoglobin, 010401 analytical chemistry, Electrochemical Techniques, 021001 nanoscience & nanotechnology, Enzymes, Immobilized, Atomic and Molecular Physics, and Optics, 0104 chemical sciences, chemistry, Electrode, Graphite, 0210 nano-technology, Biosensor, Nuclear chemistry
Abstract

A new biosensor for the analysis of nitrite in food was developed based on hemoglobin (Hb) covalently immobilized on the succinimide functionalized poly(n-butyl acrylate)-graphene [poly(nBA)-rGO] composite film deposited on a carbon-paste screen-printed electrode (SPE). The immobilized Hb on the poly(nBA)-rGO conducting matrix exhibited electrocatalytic ability for the reduction of nitrite with significant enhancement in the reduction peak at −0.6 V versus Ag/AgCl reference electrode. Thus, direct determination of nitrite can be achieved by monitoring the cathodic peak current signal of the proposed polyacrylic-graphene hybrid film-based voltammetric nitrite biosensor. The nitrite biosensor exhibited a reproducible dynamic linear response range from 0.05–5 mg L−1 nitrite and a detection limit of 0.03 mg L−1. No significant interference was observed by potential interfering ions such as Ca2+, Na+, K+, NH4+, Mg2+, and NO3− ions. Analysis of nitrite in both raw and processed edible bird’s nest (EBN) samples demonstrated recovery of close to 100%. The covalent immobilization of Hb on poly(nBA)-rGO composite film has improved the performance of the electrochemical nitrite biosensor in terms of broader detection range, lower detection limit, and prolonged biosensor stability.

Published
2018

3. Determination of Ammonium Ion Using a Reagentless Amperometric Biosensor Based on Immobilized Alanine Dehydrogenase.

Author

Ling Ling Tan, Musa, Ahmad, and Yook Heng Lee

Subjects
*AMMONIUM ions, *CONDUCTOMETRIC analysis, *BIOSENSORS, *ALANINE dehydrogenase, *PYRUVATES, *NAD+ synthase, *ELECTROLYTIC oxidation, *STANDARD deviations
Abstract

The use of the enzyme alanine dehydrogenase (AlaDH) for the determination of ammonium ion (NH4+) usually requires the addition of pyruvate substrate and reduced nicotinamide adenine dinucleotide (NADH) simultaneously to effect the reaction. This addition of reagents is inconvenient when an enzyme biosensor based on AlaDH is used. To resolve the problem, a novel reagentless amperometric biosensor using a stacked methacrylic membrane system coated onto a screen-printed carbon paste electrode (SPE) for NH4+ ion determination is described. A mixture of pyruvate and NADH was immobilized in low molecular weight poly(2-hydroxyethyl methacrylate) (pHEMA) membrane, which was then deposited over a photocured pHEMA membrane (photoHEMA) containing alanine dehydrogenase (AlaDH) enzyme. Due to the enzymatic reaction of AlaDH and the pyruvate substrate, NH4+ was consumed in the process and thus the signal from the electrocatalytic oxidation of NADH at an applied potential of +0.55 V was proportional to the NH4+ ion concentration under optimal conditions. The stacked methacrylate membranes responded rapidly and linearly to changes in NH4+ ion concentrations between 10-100 mM, with a detection limit of 0.18 mM NH4+ ion. The reproducibility of the amperometrical NH4+ biosensor yielded low relative standard deviations between 1.4-4.9%. The stacked membrane biosensor has been successfully applied to the determination of NH4+ ion in spiked river water samples without pretreatment. A good correlation was found between the analytical results for NH4+ obtained from the biosensor and the Nessler spectrophotometric method. [ABSTRACT FROM AUTHOR]

Published
2011
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