Lian-Sai Chia

Analysis and biological activities of anthocyanins.

Anthocyanins are naturally occurring compounds that impart color to fruits, vegetables, and plants. They are probably the most important group of visible plant pigments besides chlorophyll. Apart from imparting color to plants, anthocyanins also have an array of health-promoting benefits, as they can protect against a variety of oxidants through a various number of mechanisms. However, anthocyanins have received less attention than other flavonoids, despite this. This article reviews their biological functions and pre-clinical studies, as well as the most recent analytical techniques concerning anthocyanin isolation and identification.

Renewable silica sol-gel derived carbon composite based glucose biosensor

Abstract An amperometric mediated glucose biosensor has been developed based on a sol–gel derived carbon composite material. Glucose oxidase and the mediator vinylferrocene have been immobilised within the porous, rigid and organically modified silicate network in the composite material. The organic group in the silicate network controls the hydrophobicity of the electrode surface and thus limits the wettability of the electrode surface. Various important fabrication factors controlling the biosensor performance have been investigated systematically. The glucose biosensor can be renewed easily in a reproducible manner by a simple polishing step and it has a long operational lifetime. Applicability of the biosensor has been demonstrated in real samples and the results obtained by this biosensor corroborate well with a classical UV spectrophotometric technique.

Mediated amperometric glucose sensor modified by the sol-gel method

Abstract An amperometric mediated glucose sensor has been developed via the sol-gel technique in a new ‘sandwich’ configuration: sol-gel-ferrocene:glucose oxidase (GOx):sol-gel using a carbon paste electrode as the primary electrode. The process parameters for the fabrication of a glucose sensor based on tetramethoxysilane (TMOS) sol-gel thin films utilizing ferrocene as a mediator have been optimized. In the sol-gel matrix, the results demonstrate that GOx still retains its activity, and ferrocene is efficient at shuttling the electrons between the enzyme redox centre and the electrode. Cyclic voltammetric and amperometric measurements have been used to study the response of the glucose sensor, which has a fast response and good reproducibility. The effect of oxygen on the sensor response has been investigated. The selectivity, lifetime and fabrication reproducibility of the sensor have also been evaluated.

THE PREDICTING ROLE OF COGNITIVE VARIABLES IN PROBLEM SOLVING IN MOLE CONCEPT

This work is an extension of the two previous studies which aims at verifying the importance of the cognitive variables to problem solving in Chemistry across topics and levels. The previous studies show that the five cognitive variables namely, Specific Knowledge, Non-Specific but Relevant Knowledge, Concept Relatedness, Idea Association and Problem Translating Skill, are the important predictors of problem-solving performance in the topic of Grade 12 Electrochemistry. This present study involved 115 Grade 9 Chemistry students, aged between 13 and 16, solving Mole Concept problems with the familiarity levels ranging from familiar to partially familiar. Four of the five cognitive variables, Specific Knowledge, Concept Relatedness, Idea Association and Problem Translating Skill, have been found to be significant in predicting problem-solving performance with Idea Association being the most significant. The study also suggests that the difference in the topics and levels appeared to have little effect on the importance of these variables on problem-solving performance. [Chem. Educ. Res. Pract. Eur.: 2001, 2, 285-301]

Secondary Students' Perceptions about Learning Qualitative Analysis in Inorganic Chemistry.

Grade 10 students in Singapore find qualitative analysis one of the more difficult topics in their external examinations. Fifty-one grade 10 students (15-17 years old) from three schools were interviewed to investigate their perceptions about learning qualitative analysis and the aspects of qualitative analysis they found difficult. The results showed that students found qualitative analysis tedious, difficult to understand and found the practical sessions unrelated to what they learned in class. They also believed that learning qualitative analysis required a great amount of memory work. It is proposed that their difficulties may arise from not knowing explicitly what is required in qualitative analysis, the content of qualitative analysis, the lack of motivation to understand qualitative analysis, cognitive overloading, and the lack of mastery of the required process skills.

A new ent-kauranoid from Isodon lophanthoides var. geradianus

A new ent-kaurane diterpenoid, lophanthodin G (1) and one known abietanoid, 6α-hydroxyferruginol (2), were isolated from the leaves of Isodon lophanthoides var. geradianus. The structure of the new compound 1 was established using spectroscopic methods including extensive 1D and 2D NMR analysis.

A chemical equation as a representation of a class of linear Diophantine equations and a system of homogeneous linear equations

A chemical equation, comprising nelements interspersed among mspecies (reactants + products) and where the stoichiometric coefficients are represented by algebraic symbols, is shown to be equivalent to a class of linear Diophantine equations as well as a system of khomogeneous linear equations in munknowns, where k^ n.The use of conservation conditions for the elements in the chemical equation affords a non‐conventional approach for the generation of some of the integral solution sets of the Diophantine equations and the integral solutions of the system of homogeneous linear equations.