A low-cost optical sensing device based on paired emitter–detector light emitting diodes

An inexpensive flow injection analysis system for determining low concentration levels of nitrite employing the Griess reagent spectrophotometric method is reported. The novel photometric detector applied within this manifold is a highly sensitive, low cost, miniaturized light emitting diode (LED) based flow detector. This colorimetric detector employs two LEDs, operating one as a light source and the other as a light detector. The emitter LED is forward biased and the detector reverse biased. The emitter and detector LED had a λ max of 530 nm and 623 nm respectively. The emission spectrum of the emitter LED efficiently overlapped with the absorbance spectrum of 9 µM NO 2 and Griess reagent complex. A simple timer circuit measures the time taken for the photocurrent generated by the emitter LED to discharge the detector LED from 5 V (logic 1) to 1.7 V (logic 0). The Griess reagent method employed for nitrite determination is based on the formation of an azo dye, the intensity of which is directly related to nitrite concentration. The linear range, reproducibility and limit of detection were investigated. Detection limits in the nanomolar range were achieved using the Paired Emitter-Detector Diode (PEDD) flow analysis device. For a comparative study the linear range and limit of detection were also investigated using a platewell reader. Higher sensitivity and improved precision were obtained from the PEDD compared to the commercially available plate well reader.

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“…The measurement is based on the following theoretical model (Equation 1), which has been derived by Lau et al 24 .…”

Section: (λ Max 530 Nm) Peddmentioning

confidence: 99%

Detection of nitrite by flow injection analysis using a novel paired emitter-detector diode (PEDD) as a photometric detector

et al. 2007

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“…While functional, not all are suitable for the applications outlined earlier in terms of practicality, portability and scalability. Previous reports by Lau [38], Shepherd [39] and O'Toole et al [40] have reported the advantages of implementing a paired emitter-detector diode (PEDD) arrangement as a colorimetric chemical detection system. A PEDD system consists of two LEDs wherein one is used as the light source (emitter) and the other is used in reverse bias as the light detector.…”

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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

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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...

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“…The sensing technique employed with the PEDD sensor was as previously reported [21,22]. The detector LED in output mode was charged up to 5 V for 100 µs and then switched to high impedance input mode.…”

Section: Absorbance Measurement Using a Paired Emitter-detector Diodementioning

confidence: 99%

“…The detector LED in output mode was charged up to 5 V for 100 µs and then switched to high impedance input mode. Photons from the emitter LED generate a photocurrent in the reverse biased detector LED, which discharges a capacitance based voltage from an initial value of 5 V (logic 1) to a preset value of 1.7 V (logic 0) [21,22].…”

Section: Absorbance Measurement Using a Paired Emitter-detector Diodementioning

confidence: 99%

“…A PEDD consists of two LEDs, whereby one serves as the light source and the other in reverse bias mode as the light detector. 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 from 5 V (logic 1) to 1.7 V (logic 0) to give digital output directly without using an A/D converter or operation amplifier [21,22]. This method achieves excellent sensitivity and signal-tonoise ratio in comparison to the more commonly employed method of coupling an LED to a photodiode [23].…”

Section: Introductionmentioning

confidence: 99%

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Inkjet printed LED based pH chemical sensor for gas sensing

O'Toole

Shepherd

Wallace

et al. 2009

Analytica Chimica Acta

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A low-cost optical sensing device based on paired emitter–detector light emitting diodes

Cited by 74 publications

References 16 publications

Detection of nitrite by flow injection analysis using a novel paired emitter-detector diode (PEDD) as a photometric detector

Detection of nitrite by flow injection analysis using a novel paired emitter-detector diode (PEDD) as a photometric detector

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

Inkjet printed LED based pH chemical sensor for gas sensing

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