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Article
Publication date: 22 June 2012

Helmi Wasoh, Lee Yook Hengb, Fatimah Abu Bakar, Rahman Wagiran, Abu Bakar Salleh, Nor Azah Yusof, Norhisam Misrond and Fatin Hazimah Abdul Rahmane

The purpose of this paper is to describe a capacitive biosensor device consisting of an enzyme electrode and a simple detector which has been developed for histamine measurement.

495

Abstract

Purpose

The purpose of this paper is to describe a capacitive biosensor device consisting of an enzyme electrode and a simple detector which has been developed for histamine measurement.

Design/methodology/approach

In this analysis, degradation of histamine through enzymatic reaction produces signal that is monitored using a simple detector equipped with “astable” multivibrator operation circuit (in capacitor‐resistor circuit).

Findings

Different frequency (f) readings have been obtained for glucose, alcohol and histamine in different concentration levels, showing the ability of this simple device system to measure their dielectric constant (k) as formulated by the equation f=(1.44d)/ [kA (R1+2R2)]. The analysis using smaller electrode gap (d) produces higher value of f, indicating that d, is directly proportional to f. For histamine, by using immobilized enzyme electrode, the results show that the change of dielectric properties during the 300‐second reaction period could also be monitored. A linear relationship is obtained between concentration and frequency from 50 to 200 ppm.

Practical implications

Based on this result, an enzyme electrode and “astable” operation circuits have the potential to be used in the development of a simple capacitive biosensor device.

Originality/value

The paper is an outcome of experimental work carried out to observe capacitive sensing behavior using an immobilized enzyme, to measure biological samples, especially histamine.

Details

Sensor Review, vol. 32 no. 3
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 19 January 2015

Alif Syarafi Mohamad Nor, Mohd Amri Md Yunus, Sophan Wahyudi Nawawi, Sallehuddin Ibrahim and Mohd Fua'ad Rahmat

The purpose of this study is to determine the contamination level in natural water resources because the tremendous development in the agriculture sector has increased the amount…

336

Abstract

Purpose

The purpose of this study is to determine the contamination level in natural water resources because the tremendous development in the agriculture sector has increased the amount of contamination in natural water sources. Hence, the water is polluted and unsafe to drink.

Design/methodology/approach

Three types of sensor arrays were suggested: parallel, star and delta. The simulation of all types of sensor array was carried out to calculate the sensors’ impedance value, capacitance and inductance during their operation to determine the best sensor array. The contamination state was simulated by altering the electrical properties values of the environmental domain of the model to represent water contamination.

Findings

The simulation results show that all types of sensor array are sensitive to conductivity, σ, and permittivity, ɛ (i.e. contaminated water). Furthermore, a set of experiments was conducted to determine the relationship between the sensor’s impedance and the water’s nitrate and sulphate contamination. The performance of the system was observed where the sensors were tested, with the addition of distilled water with different concentrations of potassium nitrate and potassium sulphate. The sensitivity of the developed sensors was evaluated and the best sensor was selected.

Practical implications

Based on the outcomes of the experiments, the star sensor array has the highest sensitivity and can be used to measure nitrate and sulphate contaminations in water.

Originality/value

The star sensor array presented in this paper has the potential to be used as a useful low-cost tool for water source monitoring.

Details

Sensor Review, vol. 35 no. 1
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 11 July 2022

Linda Lin, Dennis Foung and Julia Chen

This study aims to examine the impact of the transformation of an assessment on students’ performance and perspectives in an English for Academic Purposes course in Hong Kong. The…

332

Abstract

Purpose

This study aims to examine the impact of the transformation of an assessment on students’ performance and perspectives in an English for Academic Purposes course in Hong Kong. The assessment was changed from the traditional pen-and-paper mode to an unproctored online mode.

Design/methodology/approach

Using mixed methods, the research team analysed the differences between the assessment performances of those who took the course before the pandemic (n = 664) and those who took it during the pandemic (n = 702). Furthermore, focus group interviews were conducted with seven students regarding their perspectives on the unproctored assessment.

Findings

The results revealed that, although there were no major differences in the overall grades of the two groups, students who were assessed online during the pandemic performed significantly better in terms of their English use. Nevertheless, the shift to online assessment had several negative effects on the students.

Originality/value

Previous studies on unproctored online assessments (UOA) were concerned with potential learning quality issues, such as plagiarism and grade inflation. This study, however, provided empirical evidence that high-quality assessment delivery can be provided via UOA if the question types and assessment arrangements are carefully decided.

Details

Quality Assurance in Education, vol. 31 no. 1
Type: Research Article
ISSN: 0968-4883

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