Novel fused-LEDs devices as optical sensors for colorimetric analysis

Lau, King Tong

doi:10.1016/j.talanta.2003.10.034

Cited by 78 publications

(73 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…3 using the amount of light I reaching the detector and the amount I 0 in the absence of indicator membrane [41]. The value t 0 corresponds to the discharge time obtained in the absence of the indicator membrane and t to the discharge time of the membrane at any CO2 concentration.…”

Section: Instrument Response To Carbon Dioxidementioning

confidence: 99%

“…In this technique the photocurrent generated by the emitter LED and later modified by the sample, discharges the detector LED at a rate which is related to the intensity of light that reaches the detector, which can be tracked by a simple microprocessor circuit. Therefore, instead of measuring the photocurrent directly, a simple timer circuit is used to measure the time taken for the photocurrent generated by the emitter LED to discharge the detector LED to give a digital output directly without using an A/D converter or operation amplifier [41][42][43].…”

mentioning

confidence: 99%

See 1 more Smart Citation

A new light emitting diode–light emitting diode portable carbon dioxide gas sensor based on an interchangeable membrane system for industrial applications

Vargas-Sansalvador

Fay

Phelan

et al. 2011

Analytica Chimica Acta

View full text Add to dashboard Cite

A new system for CO2 measurement (0-100%) by based on a paired emitter-detector diode arrangement as a colorimetric detection system is described. Two different configurations were tested: configuration 1 (an opposite side configuration) where a secondary inner-filter effect accounts for CO2 sensitivity. This configuration involves the absorption of the phosphorescence emitted from a CO2-insensitive luminophore by an acid-base indicator and configuration 2 wherein the membrane containing the luminophore is removed, simplifying the sensing membrane that now only contains the acid-base indicator. In addition, two different instrumental configurations have been studied, using a paired emitter-detector diode system, consisting of two LEDs wherein one is used as the light source (emitter) and the other is used in reverse bias mode as the light detector. The first configuration uses a green LED as emitter and a red LED as detector, whereas in the second case two identical red LEDs are used as emitter and detector. The system was characterised in terms of sensitivity, dynamic response, reproducibility, stability and temperature influence. We found that configuration 2 presented a better CO2 response in terms of sensitivity.Key words. Carbon dioxide sensor; Gas sensor; Optical sensor; Paired emitter detector-diode sensor; Portable instrumentation. INTRODUCTIONCO2 is an important industrial gas for many different uses that include production of chemicals (e.g. urea ), inert agent for food packaging (to extend the shelf-life of meat, cheese, etc.), beverages, refrigeration systems, welding systems, fire extinguishers, water treatment processes, and many other smaller scale applications [1;2]. In the agro-food industry CO2 is widely used in modified-atmosphere packaging where its task is to inhibit growth of spoilage bacteria [3;4]. For instance, in active packaging technologies a CO2 generating system can be considered as a technique complimentary to oxygen scavenging [5]. High CO2 levels (10-80 %) are desirable for foods such as meat and poultry in order to inhibit surface microbial growth and to extend their life time. The maintenance of CO2 concentration within packages in food [6], as instance using inserted sachets [7;8], must be carefully monitored since CO2 permeability is 3-5 times higher than that of oxygen for most of the plastic films and because CO2 is absorbed by many foods like meat and poultry. Real-time process monitoring is fundamental for effective process control. The rapid development of bioprocess applications together with the agro-food industry have led to an intensive search for new sensors capable of providing real-time information about the state of the processes. Conventional methods for CO2 determination include, among others, infrared spectrometry [9] or electrochemical sensors based on liquid (Severinghaus-type electrodes) or solid electrolytes [10;11]. The most popular sensors used for CO2 gas sensing in biotechnological applications are based on electrochemical measurements that can...

show abstract

Section: Instrument Response To Carbon Dioxidementioning

confidence: 99%

mentioning

confidence: 99%

A new light emitting diode–light emitting diode portable carbon dioxide gas sensor based on an interchangeable membrane system for industrial applications

Vargas-Sansalvador

Fay

Phelan

et al. 2011

Analytica Chimica Acta

View full text Add to dashboard Cite

show abstract

“…A common, 660-nm LEDs served as detector as the LED is sufficiently sensitive through the spectrum below the emission wavelength. (Lau et al 2004) 3. Results and Discussion…”

Section: Portable Centrifugal Microfluidic Analytical System (Cmas)mentioning

confidence: 99%

A portable centrifugal analyser for liver function screening

Nwankire

Czugala

Burger

et al. 2014

Biosensors and Bioelectronics

View full text Add to dashboard Cite

Mortality rates of up to 50% have been reported after liver failure due to drug-induced hepatotoxicity and certain viral infections (Gao et al. 2008). These adverse conditions frequently affect HIV and tuberculosis patients on regular medication in resource-poor settings. Here, we report full integration of sample preparation with read-out of a 5-parameter liver assay panel (LAP) on a portable, easy-to-use, fast and costefficient centrifugal microfluidic analysis system (CMAS). Our unique, dissolvable-film based centrifugopneumatic valving was employed to provide sample-to-answer fashion automation for plasma extraction (from finger-prick of blood), metering and aliquoting into separate reaction chambers for parallelized colorimetric quantification during rotation. The entire LAP completes in less than 20 minutes while using only a tenth the reagent volumes when compared with standard hospital laboratory tests. Accuracy of in-situ liver function screening was validated by 96 separate tests with an average coefficient of variance (CV) of 7.9% compared to benchtop and hospital lab tests. Unpaired two sample statistical t-tests were used to compare the means of CMAS and benchtop reader, on one hand; and CMAS and hospital tests on the other. The results demonstrate no statistical difference between the respective means with 94% and 92% certainty of equivalence, respectively. The portable platform thus saves significant time, labour and costs compared to established technologies, and therefore comply with typical restrictions on lab infrastructure, maintenance, operator skill and costs prevalent in many field clinics of the developing world. It has been successfully deployed in a centralised lab in Nigeria. IntroductionLiver is the largest solid organ in the body and is largely responsible for metabolism and detoxification. (Gao et al. 2008) Liver function tests are widely used in clinical chemistry to assess therapeutic effects and potential medication-induced liver damage, especially when taking medications for HIV, tuberculosis and cancer. (Landis et al. 2013;Rahmioglu et al. 2009; Vella et al. 2012) Literature reports suggest that a mortality rate of 2 -28% can be linked with medication-induced liver damage. (Vella et al. 2012) As a result, monitoring of liver function when on certain medications has become common practice in developed countries but can be expensive in poor resource areas. This has prompted local governments and international funding agencies to set up centralised laboratories for liver function monitoring tests especially for HIV patients. Nonetheless, transport logistics and accessibility remains a significant challenge for the majority of these patients. Thus it is very important to develop portable point-of-care (PoC) devices that could be used for liver function screening in the field. Currently, there are only a handful of sample-to-answer PoC devices available for deployment in the field. Recently, Vella et al.(Vella et al. 2012) demonstrated an innovative micropatterned paper device fo...

show abstract

“…380-900nm), have a long lifetime, robust and easy to fabricate into various configurations. When used as light detectors for chemical sensing by measuring the intensity-dependent discharge of capacitance, they have been found to be highly sensitive and could detect sub micro molar of dye 3 .…”

Section: Introductionmentioning

confidence: 99%

“…Mims et al [16][17] first investigated using LED as a crude light detector to measure photocurrent generated by direct sunlight. Previously, we demonstrated the use of a Paired Emitter Detector Diode (PEDD) device for colour and pH measurements in static solution 3 .…”

Section: Introductionmentioning

confidence: 99%

Photometric detection in flow analysis systems using integrated PEDDs

Toole

Lau

Diamond

2005

Talanta

Self Cite

View full text Add to dashboard Cite

A novel inexpensive optical sensing technique has been developed for colorimetric flow analysis. This sensing system employs two LEDs whereby one is used as the light source and the other as a light detector. The LED used as light detector is reverse biased with a 5V supply so that the photocurrent generated by the incident light discharges the capacitance. Direct digital output is provided by a simple timer circuit that measures the time taken for this discharge process from 5V (logic 1) to 1.7V (logic 0). This sensing concept has been applied in flow analysis by constructing an optical flow cell with a pair of LEDs. Calibration of the integrated optical flow cell using a dye resulted in a linear response that obeys the Beer-Lambert Law. The flow rate, dynamic range, sensitivity and limits of detection were investigated. The system was also used for pH determination in the range of pH 2.5 -6.8 using bromocresol green (BCG). The pK a of BCG was successfully determined by this technique.

show abstract

Novel fused-LEDs devices as optical sensors for colorimetric analysis

Cited by 78 publications

References 15 publications

A new light emitting diode–light emitting diode portable carbon dioxide gas sensor based on an interchangeable membrane system for industrial applications

A new light emitting diode–light emitting diode portable carbon dioxide gas sensor based on an interchangeable membrane system for industrial applications

A portable centrifugal analyser for liver function screening

Photometric detection in flow analysis systems using integrated PEDDs

Contact Info

Product

Resources

About