Extending the response range of an optical fibre pH sensor using an artificial neural network

Taib, Mohd Nasir; Andres, Roberto T.; Narayanaswamy, Ramaier

doi:10.1016/0003-2670(96)00149-3

Cited by 66 publications

(24 citation statements)

References 13 publications

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“…Chlorophenol red indicator changes its colour from yellow to purple in a narrow interval of 4.0-7.0 pH units. To solve this problem especially in optical fiber optic pH sensor research, a lot of approach has been used such as using multiple pH indicators 2,3 , the use of indicators with multiple steps of acid dissociation and ANN technique [4][5][6] .…”

Section: Introductionmentioning

confidence: 99%

The Use of Artificial Neural Network to Optimize The pH Response Range of Chlorophenol Red

Wong

Ahmad

Heng

2017

AJSTD

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Artificial Neural Network (ANN) had been used in this study to extend the response range of the pH indicator. The input from absorbance values of the absorbance spectra of chlorophenol red at different pH was used to train the ANN. During the training process, the coefficient values of the ANN will be adjusted to obtain the desire output. In this research, back propagation algorithm had been used for optimizing the response range of the pH indicator chlorophenol red in solution. The result indicates that the use of ANN enable the pH response range to be extended from 4.8-6.8 to 1.0-10.0.Keywords : Artificial neural network, back-propagation algorithm, pH indicator,chlorophenol red. INTRODUCTIONChlorophenol red is a pH indicator, which gradually changes its colour over a range called "visual transition interval" 1 . Most of the pH indicators determine the pH changes indirectly in limited linear dynamic range, often 2-4 pH units only. Chlorophenol red indicator changes its colour from yellow to purple in a narrow interval of 4.0-7.0 pH units. To solve this problem especially in optical fiber optic pH sensor research, a lot of approach has been used such as using multiple pH indicators 2,3 , the use of indicators with multiple steps of acid dissociation and ANN technique 4-6 .The original works on ANN were published more than 50 years ago by McCulloch and Pitts 7,8 and Webb 9 . Lately, ANN has been shown to provide a superior alternative mechanism for modeling non-linear systems [10][11][12][13][14] . Application of ANNs is similar to conventional non-linear modeling techniques that require a model-structure design and parameter-estimating cycle to calibrate the model but ANNs use more general modeling approach, i.e. model structure need not to be defined explicitly 12 .

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Section: Introductionmentioning

confidence: 99%

The Use of Artificial Neural Network to Optimize The pH Response Range of Chlorophenol Red

Wong

Ahmad

Heng

2017

AJSTD

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“…It is useful in spectral analyses because the simultaneous inclusion of multiple spectral intensities can greatly improve the precision and applicability of quantitative spectral analysis of multicomponent mixtures that can not be resolved by conventional spectrometry. In recent years multivariate calibration has become an important tool in resolution of mixtures of components in many different fields including biomedical 20,21 environmental 22,23 and drug analysis 24,25 . This paper describes an analytical methodology for simultaneous determination of Sulfamethoxazole and Trimethoprim using spectrophotometric method with preprocessing by direct orthogonal signal correction (DOSC).…”

Section: Introductionmentioning

confidence: 99%

Direct Orthogonal Signal Correction-Partial Least Squares for Simultaneous Spectrophotometric Determination of Sulfamethoxazole and Trimethoprim in Pharmaceutical Formulation and Synthetic Samples

Goodarzi

Shahbazikhah

Sohrabi

et al. 2009

J. Chil. Chem. Soc.

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This work describes a very simple, novel and selective spectrophotmetric method for simultaneous determination of sulfamethoxazole and trimethoprim in pharmaceutical preparation and synthetics samples using direct orthogonal signal correction-partial least squares (DOSC-PLS). The all factors affecting on the sensitivity were optimized and the linear dynamic range for determining of these drugs was found. The PLS modeling was used for the multivariate calibration of the spectrophotometric data and DOSC was used for preprocessing of data matrices and the prediction results of model. The experimental calibration matrix was designed by measuring the absorbance over the range 200-400 nm for 32 samples of 2.0-15.0 and 0.4-6.0 μg mL -1 of sulfamethoxazole and trimethoprim, respectively. The root mean square error of prediction for sulfamethoxazole and trimethoprim using DOSC-PLS and PLS were 0.02212, 0.02363 and 0.17014, 0.01660,μg mL -1 respectively. Application of the method to synthetic samples of standard solutions and in pharmaceutical formulation was performed and satisfactory results were obtained.

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“…Os optodos para medidas de pH estão baseados nas mudanças de absorbância, reflectância ou fluorescência 5,15 de um indicador sensível ao pH e que reage reversivelmente com os prótons da amostra 5,21 . Muito embora os indicadores ácido-base utilizados nas titulações clássicas apresentem a desvantagem inerente de fornecer mudanças ópticas numa faixa não maior do que 2 unidades de pH (pKa ± 1), eles ainda têm sido investigados para a construção de optodos, uma vez que mistura de indicadores 22 e métodos quimiométricos 23 podem ser empregados para ampliar esta faixa.…”

Section: Introductionunclassified

Uso de membranas de Nafion para a construção de sensores ópticos para medidas de pH

Pinheiro¹,

Raimundo²

2005

Quím. Nova

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, bromothymol blue (BB) and methyl violet (MV), were studied aiming at constructing an optical sensor for pH measurement. BB revealed to be inadequate for developing sensing phases due to the electrostatic repulsion between negative groups of their molecules and the negative charge of the sulfonate group of the Nafion ® , which causes leaching of the dye from the membrane. On the other hand, MV showed to be suitable due to the presence of positive groups in its structure. The membrane prepared from a methanolic solution whose Nafion ® /dye molar ratio was 20 presented the best analytical properties, changing its color from green to violet in the pH range from 0.6 to 3.0. The membrane can be prepared with good reproducibility, presenting durability of ca. 6 months and response time of 22 s, making possible its use for pH determination in flow analysis systems.Keywords: optical sensor; optode; pH sensor. INTRODUÇÃOOs sensores químicos de fibras ópticas, também conhecidos como optodos 1-3 ou optrodos 4 , combinam as vantagens oferecidas pelas fibras ópticas com sistemas químicos de transdução. Nestes sensores, a fase sensora (transdutor químico) é constituída por um reagente imobilizado, sensível e preferencialmente seletivo a um dado analito, que gera o sinal óptico, o qual é relacionado à concentração da espécie de interesse.A imobilização de um reagente pode ser realizada fisicamente, por adsorção, oclusão ou atração eletrostática, ou quimicamente, através de ligação covalente 5 . A imobilização física do reagente por adsorção na superfície é a mais simples de ser efetuada, sendo assim, empregada com regularidade. Entretanto, tem como principal desvantagem o baixo tempo de vida útil do sensor, pois o reagente pode ser facilmente lixiviado, dado que sua interação com o suporte é relativamente fraca 6 . A oclusão do reagente em uma matriz polimérica, embora, a princípio, possa aumentar o tempo de resposta do sensor em função da espessura da membrana, permite a obtenção de fases sensoras de maior durabilidade, pois o reagente permanece preso no interior da membrana, sendo lixiviado com maior dificuldade 5 . A imobilização covalente do reagente 2,7 na matriz adequada é considerada eficiente, pois minimiza a perda do reagente por lixiviação. A literatura relata o uso de vários materiais poliméricos adequados para imobilizar o reagente covalentemente, sendo mais comumente usados os derivados da celulose 2,8-13 . As membranas assim obtidas oferecem optodos com tempos de resposta curtos, vida útil longa e grande estabilidade.Os métodos que empregam sensores ópticos são baseados nas mudanças das propriedades ópticas do reagente imobilizado, por meio de medidas de reflexão, dispersão, difusão de luz, interferên-cia, absorção, refração e difração. Quando um destes fenômenos acontece, as mudanças nas propriedades ópticas resultam na modulação de uma ou mais das seguintes propriedades: comprimento de onda (cor), amplitude, fase ou polarização 14 . O princípio de funcionamento básico dos optodos é simples. A luz de uma fonte ...

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Extending the response range of an optical fibre pH sensor using an artificial neural network

Cited by 66 publications

References 13 publications

The Use of Artificial Neural Network to Optimize The pH Response Range of Chlorophenol Red

The Use of Artificial Neural Network to Optimize The pH Response Range of Chlorophenol Red

Direct Orthogonal Signal Correction-Partial Least Squares for Simultaneous Spectrophotometric Determination of Sulfamethoxazole and Trimethoprim in Pharmaceutical Formulation and Synthetic Samples

Uso de membranas de Nafion para a construção de sensores ópticos para medidas de pH

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