190 research outputs found
Effect Of Plasticizers On A Pvc Sensing Phase For Evaluation Of Water Contamination By Aromatic Hydrocarbons And Fuels Using Infrared Spectroscopy
No full textThe effects of di-2-ethylhexylsebacate (DOS), di-2-ethylhexylphthalate (DOP) and 2-nitro-phenyl-octylether (NPOE) plasticizers on a PVC sensing phase for evaluation of water contamination by aromatic hydrocarbons and fuels were investigated. The performance of each film was assessed by means of figures of merit obtained from analytical curves constructed in different wavenumbers. A mixture design (simplex centroid) with the BTEX compounds was performed in order to evaluate cross-interferences and interaction effects. For preparation of the sensing phase, a mixture of PVC with 25% of the plasticizer and 0.3% of the stabilizer Tinuvin P (2-2′-hydroxy-5-tert-octylphenyl-benzotriazol) dissolved in THF was used. The results show that NPOE and DOP plasticizers present similar performances, while DOS provides better values of sensitivity and detection limit for all compounds. With the use of DOS the detection limits were 2.4, 0.4, 1.5 and 1.2 mg L -1 for BTEX, respectively. Regarding the study of multi-component interactions, it was observed that benzene and xylenes do not show interferences from the other analytes of the mixture at the wavenumbers of 676 and 1522 cm -1, respectively. Ethylbenzene and toluene undergo spectral interferences and interaction effects in all peaks evaluated, requiring a multivariate calibration for their determination. In the analysis of water contaminated by fuels, a 3-D plot as a function of benzene, toluene and xylenes concentrations as well as the principal component analysis of the spectral data presented well-defined groups for each kind of contamination (gasoline A, gasoline C, diesel and diesel with 2% of biodiesel). These results demonstrate the potential of the proposed method, employing a PVC sensing phase, with transmittance measurements in the mid-infrared, for determination of contamination of waters by aromatic hydrocarbons. In conclusion, PVC films plasticized with DOS can be useful for studies of water contamination based on transmittance measurements in the mid-infrared region, avoiding the drawbacks of ATR methods. © 2009 Elsevier B.V. All rights reserved.1391222230Albuquerque, J.S., Pimentel, M.F., Silva, V.L., Raimundo Jr., I.M., Rohwedder, J.J.R., Pasquini, C., Silicone sensing phase for detection of aromatic hydrocarbons in water employing near-infrared spectroscopy (2005) Anal. Chem., 77, pp. 72-77Lima, K.M.G., Raimundo Jr., I.M., Pimentel, M.F., Improving the detection limits of near infrared spectroscopy in the determination of aromatic hydrocarbons in water employing a silicone sensing phase (2007) Sens. Actuators B, 125, pp. 229-233Heglund, D.L., Tilotta, D.C., Determination of volatile organic compounds in water by solid phase microextration and infrared spectroscopy (1996) Environ. Sci. Technol., 30, pp. 1212-1219Jakusch, M., Mizaikoff, B., Kellner, R., Towards a remote IR fiber-optic sensor system for the determination of chlorinated hydrocarbons in water (1997) Sens. Actuators B, 83, pp. 38-39Yang, J., Ramesh, A., Membrane-introduced infrared spectroscopic chemical sensing method for the detection of volatile organic compounds in aqueous solutions (2005) Analyst, 130, pp. 397-403Flavin, K., Hughes, H., Dobbyn, V., Kirwan, P., Murphy, K., Steiners, H., Mizaikoff, B., Mcloughlin, P., A comparison of polymeric materials as pre-concentrating media for use with ATR/FTIR sensing (2006) Int. J. Environ. Anal. Chem., 86 (6), pp. 401-415Gobel, R., Krska, R., Kellner, R., Seitz, R.W., Tomellini, S.A., Investigation of different polymers as coating materials for IR/ATR spectroscopic trace analysis of chlorinated hydrocarbons in water (1994) Appl. Spectrosc., 48, pp. 678-683Janotta, M., Karlowatz, M., Vogt, F., Mizaikoff, B., Sol-gel based mid-infrared evanescent wave sensors for detection of organophosphate pesticides in aqueous solution (2003) Anal. Chim. Acta, 496, pp. 339-348Eartan-Lamontagne, M.C., Lowry, S.R., Seitz, W.R., Tomellini, S.A., Polymer-coated tapered cylindrical ATR elements for sensitive detection of organic solutes in water (1995) Appl. Spectrosc., 49 (8), pp. 1170-1173Walsh, J.E., Maccraith, B.D., Meaney, M., Vos, J.G., Regan, F., Lancia, A., Artjushenko, S., Sensing of chlorinated hydrocarbons and pesticides in water using polymer coated mid-infrared optical fibres (1996) Analyst, 121, pp. 789-792Regan, F., Walsh, F., Walsh, J., Development of plasticised PVC sensing films for the determination of BTEX compounds in aqueous samples (2003) Int. J. Environ. Anal. Chem., 83, pp. 621-631McCue, R.P., Walsh, J.E., Walsh, F., Regan, F., Modular fibre optic sensor for the detection of hydrocarbons in water (2006) Sens. Actuators B, 114, pp. 438-444Silva, A.M.S., Pimentel, M.F., Raimundo Jr., I.M., Almeida, Y.M.B., A PVC sensing for determination of BTEX in water employing mid-infrared spectroscopy (2008) Vib. Spectrosc., 46, pp. 39-44Titow, W.V., (1984) PVC Technology. 4th ed., , Elsevier Applied Science, OxfordGäther, R., Müller, H., (1984) Plastic Additives Handbook. 2nd ed., , Hanser, New YorkRabello, M., (2000) Aditivação de Polímeros, , Ed. Artiliber, São PauloNeto, B.B., Scarminio, I.S., Bruns, R.E., Fazer Experimentos, C., (2003) Pesquisa e Desenvolvimento na Ciência e na Indústria, , 2a ed, Ed. Unicamp, Campinas, São PauloCornell, J.A., (1990) Experiments with Mixtures: Designs Models and the Analysis of Mixtures Data, , Wiley, New YorkScheffé, H., Simplex-centroid design for experiments with mixtures (1963) J. Roy. Stat. Soc. B, 25, pp. 235-263Coscione, A.R., de Andrade, J.C., May, G.M., O modelamento estatístico de misturas: experimento tutorial usando voltametria de redissolução anódica (2005) Quim. Nova, 28 (6), pp. 1116-1122Reis, C., de Andrade, J.C., Planejamento experimental para misturas usando cromatografia em papel (1996) Quim. Nova, 19 (3), pp. 313-319Rocha, G.B., Freire, R.O., Simas, A.M., Stewart, J.J.P., RM1: A reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I (2006) J. Comput. Chem., 27, pp. 1101-1111Armstrong, R.D., Covington, A.K., Proud, W.G., Solvent properties of PVC membranes (1988) J. Electroanal. Chem., 257, pp. 155-169Armstrong, R.D., Todd, M., The role of PVC in ion selective electrode membranes (1987) J. Electroanal. Chem., 237, pp. 181-185Armstrong, R.D., Wang, H., Todd, M., Solvent properties of PVC membranes (1989) J. Electroanal. Chem., 266, pp. 173-17
Use Of Nafion® Membranes For The Construction Of Optical Sensors For Ph Measurements [uso De Membranas De Nafion Para A Construção De Sensores ópticos Para Medidas De Ph]
No full textThe behaviour of Nafion® polymeric membranes containing acid-base dyes, 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.285932936Newcombe, D.T., Cardwell, T.J., Cattral, R.W., Kolev, S.D., (1999) Anal. Chim. Acta, 401, p. 137Mohr, J.G., Wolfbeis, O.S., (1994) Anal. Chim. Acta, 292, p. 41Madden, J.E., Cardwell, T.J., Cattral, R.W., Deady, L.W., (1996) Anal. Chim. Acta, 319, p. 129Borman, S.A., (1981) Anal. Chem., 53, pp. 1616ASotomayor, M.P.T., (1996), Dissertação de Mestrado, Universidade Estadual de Campinas, BrasilWolfbeis, O.S., (1991) Fiber Optic Chemical Sensors and Biosensors, 1. , CRC Press: Boca Raton, cap. 8Sotomayor, M.P.T., (2000), Dissertação de Doutorado, Universidade Estadual de Campinas, BrasilShulman, S.G., Chen, S., Bai, F., Leiner, L.W., Wolfbeis, O.S., (1995) Anal. Chim. Acta, 304, p. 165Weighl, B.H., Holobar, A., (1993) Anal. Chim. Acta, 282, p. 335Posch, H.E., Leiner, M.J.P., Wolfbeis, O.S., (1989) Anal. Chim. Acta, 334, p. 162Holobar, A., Weighl, B.M., Trettnak, T., Benes, R., Lehmann, H., Rodriguez, N.V., Wollschalager, A., Wolfbeis, O.S., (1993) Sens. Actuators, B, 11, p. 425Werner, T., Wolfbeis, O.S., (1993) Anal. Chim. Acta, 346, p. 564Zhujun, Z., Seitz, W.R., (1984) Anal. Chim. Acta, 160, p. 47Taib, M.N., Narayanaswamy, R., (1995) Analyst, 120, p. 1617Moreno, M.C., Jiménez, M., Conde, C.P., Cámara, C., (1990) Anal. Chim. Acta, 230, p. 35Lin, J., (2000) Trends Anal. Chem., 19, p. 541Oliveira, W.A., (1996) Quim. Nova, 19, p. 77Skoog, D.A., Holler, F.J., Nieman, T.A., (2002) Princípios Da Análise Instrumental, 5 a Ed., , Bookman: Porto AlegreGuthrie, A.J., Narayanaswamy, R., Welti, N.A., (1988) Talanta, 35, p. 157Lin, J., Liu, D., (2000) Anal. Chim. Acta, 408, p. 49Motellier, S., Toulhoat, P., (1993) Anal. Chim. Acta, 271, p. 323Walt, D.R., Gabor, G., (1993) Anal. Chim. Acta, 274, p. 47Taib, M.N., Andres, R., Narayanaswamy, R., (1996) Anal. Chim. Acta, 330, p. 31Chan, C.M., Fung, C.S., Wong, K.Y., Lo, W., (1998) Analyst, 123, p. 1843Sun, L.X., Okada, T., (2000) Anal. Chim. Acta, 421, p. 84Krause, C., Werner, T., Wolfbeis, O.S., (1998) Anal. Sci., 14, p. 163Bright, F.V., Poirier, G.E., Hiefje, G.M., (1988) Talanta, 35, p. 113Ertas, N., Akkaya, E.U., Ataman, O.Y., (2000) Talanta, 51, p. 693Mohan, H., Iyer, R.M., (1993) Analyst, 118, p. 929Allain, L.R., Xue, Z., (2000) Anal. Chem., 72, p. 1078Brook, T.E., Taib, M.N., Narayanaswamy, R., (1997) Sens. Actuators, B, 38-39, p. 272Sadaoka, Y., Matsugushi, M., Sakai, Y., Murata, Y., (1992) Sens. Actuators, B, 7, p. 443Sadaoka, Y., Matsugushi, M., Sakai, Y., Murata, Y., (1992) J. Mater. Sci., 27, p. 5095Sadaoka, Y., Matsugushi, M., Sakai, Y., Murata, Y., (1991) Sens. Actuators, A, 25-27, p. 489Sadaoka, Y., Matsugushi, M., Sakai, Y., Murata, Y., (1991) Chem. Lett., 4, p. 717Sadaoka, Y., Matsugushi, M., Sakai, Y., Murata, Y., (1991) J. Electrochem. Soc., 138, p. 614Sadaoka, Y., Matsugushi, M., Sakai, Y., Murata, Y., (1993) J. Mater. Sci., 3, p. 247Raimundo, I.M., Narayanaswamy, R., (1999) Analyst, 124, p. 1623Raimundo, I.M., Narayanaswamy, R., (2000) Quim. Anal., 19, p. 127Huber, C., Klimant, I., Krause, C., Werner, T., Mayr, T., Wolfbeis, O.S., (2000) Fresenius J. Anal. Chem., 368, p. 196Ballantine, D.S., Callahan, D., (1992) Talanta, 39, p. 1658Perrin, D.D., Dempsey, D., (1956) Buffers for pH and Metal Ion Control, , Chapman & Hall: Boston, cap.10Otsuki, S., Adachi, K., (1995) J. Appl. Polym. Sci., 56, p. 697Bishop, E., (1972) Indicators, , Pergamon Press: Oxford, cap. 4Sotomayor, P.T., Raimundo, I.M., Zarbin, A.J.G., Rohwedder, J.J.R., Oliveira, G., Alves, O.L., (2001) Sens. Actuators, B, 74, p. 157Baker, M.E.J., Naraynaswamy, R., (1995) Sens. Actuators, B, 29, p. 369Guan, J.Q., Dai, Z.F., Tung, C.H., Peng, B.X., (1998) J. Photochem. Photobiol., A, 114, p. 45John, S.A., Ramaraj, R., (1997) J. Appl. Polym. Sci., 65, p. 786Baldini, F., Falai, A., Gaudio, A.R., Landi, D., Lueger, A., Mencaglia, A., Scherr, D., Trettnak, W., (2003) Sens. Actuators, B, 90, p. 13
Near And Mid Infrared Optical Sensors [sensores ópticos Com Detecção No Infravermelho Próximo E Médio]
No full textOptical chemical sensors with detection in the near and mid infrared region are reviewed. Fundamental concepts of infrared spectroscopy and optical chemical sensors are briefly described, before presenting some aspects on optical chemical sensors, such as synthesis of NIR and IR reagents, preparation of new materials as well as application in determinations of species of biological, industrial and environmental importance.32616351643Kautsky, H., Hirsch, A., (1931) Berichte der Deutschen Chemischen Gesellschaft, 64, p. 2677Bergman, I., (1968) Nature, 218, p. 266Lubbers, D.W., Opitz, N., (1975) Z. Naturforsch., 30 C, p. 532Wolfbeis, O.S., (2008) Anal. Chem., 80, p. 4269Wolfbeis, O.S., (1991) Fiber Optic Chemical Sensors and Biosensors, 1-2. , CRC Press: Boca RatonPasquini, C., (2003) J. Braz. Chem. Soc., 14, p. 198Skoog, D.A., Holler, F.J., Crouch, S.R., (2007) Principles of Instrumental Analysis 6th ed, , Thomson Brooks: USAHerschel, W., (1800) Phil Trans. Roy. Soc. 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Evaluation Of Nafion-crystal Violet Films For The Construction Of An Optical Relative Humidity Sensor
No full textThe composition of Nafion-Crystal Violet films and casting processes were studied in order to optimise the performance of an optical relative humidity sensor. The films were immobilised on a glass disc support, by placing a 5.0 μL drop of a methanolic solution of a mixture of various compositions (molar ratio) of Nafion and Crystal Violet. The homogeneity of the films, and also their reversibility to humidity, increased when the molar ratio of Nafion to Crystal Violet was increased. The homogeneity was even further improved when these films were treated with a 5.0 μL drop of methanol, leading to films of higher durability. The durability of films decreased with decrease in the film thickness. A methanol-treated, 5 μm thickness film with a Nafion:Crystal Violet molar ratio of 10.1 showed a linear response range from 30 to 70% relative humidity (r2 > 0.99), with good stability and reversibility.1241116231627Narayanaswamy, R., (1993) Analyst, 118, p. 317Barkauskas, J., (1997) Talanta, 44, p. 1107Pérez, J.M.M., Freyre, C., (1997) Sens. Actuators B, 42, p. 27Matsuguch, M., Kuroiwa, T., Miyagishi, T., Suzuki, S., Ogura, T., Sakai, Y., (1998) Sens. Actuators B, 52, p. 53Feng, C.-D., Sun, S.-L., Wang, H., Segre, C.U., Stetter, J.R., (1997) Sens. Actuators B, 40, p. 217Qu, W., Meyer, J.-U., (1997) Sens. Actuators B, 40, p. 175Pelino, M., Cantalini, C., Sun, H.-T., Faccio, M., (1998) Sens. Actuators B, 46, p. 186Kharaz, A., Jones, B.E., (1995) Sens. Actuators A, 47, p. 491Ando, M., Kobayashi, T., Haruta, M., (1996) Sens. Actuators B, 32, p. 157Otsuki, S., Adachi, S., Taguchi, T., (1998) Sens. Actuators B, 53, p. 91Choi, M.M.F., Tse, O.L., (1999) Anal. Chim. Acta, 378, p. 127John, S.A., Ramaraj, R., (1997) J. Appl. Polym. Sci., 65, p. 777Van Der Wal, P.D., De Rooij, N.F., Koudelka-Hep, M., (1996) Sens. Actuators B, 35-36, p. 119Fabre, B., Burlet, S., Cespuglio, R., Bidan, G., (1997) J. Electroanal. Chem., 426, p. 75Pan, S., Arnold, M.A., (1996) Talanta, 43, p. 1157Casella, I.G., Guascito, M.R., Salvi, A.M., Desimoni, E., (1997) Anal. Chim. Acta, 354, p. 333Zen, J.-M., Hsu, C.-T., (1998) Talanta, 48, p. 1363Barroso-Fernandez, B., Lee-Alvarez, M.T., Seliskar, C.J., Heineman, W.R., (1998) Anal. Chim. Acta, 370, p. 221Otsuki, S., Adachi, K., (1995) J. Appl. Polym. Sci., 56, p. 697Kuswandi, B., Narayanaswamy, R., (1999) J. Environ. Monit., 1, p. 109Krause, C., Werner, T., Wolfbeis, O.S., (1998) Anal. Sci., 14, p. 163Bright, F.V., Poirier, G.E., Hieftje, G.M., (1988) Talanta, 35, p. 113Madden, J.E., Cardwell, T.J., Cattrall, R.W., Deady, L.W., (1996) Anal. Chim. Acta, 319, p. 129Mohan, H., Iyer, R.M., (1993) Analyst, 118, p. 929Chan, C.-M., Fung, C.-S., Wong, K.-Y., Lo, W., (1998) Analyst, 123, p. 1843Brook, T.E., Taib, M.N., Narayanaswamy, R., (1997) Sens. Actuators B, 38-39, p. 272Sadaoka, Y., Matsuguchi, M., Sakai, Y., Murata, Y., (1992) Sens. Actuators B, 7, p. 443Sadaoka, Y., Matsuguchi, M., Sakai, Y., Murata, Y., (1992) J. Mater. Sci., 27, p. 5095Sadaoka, Y., Matsuguchi, M., Sakai, Y., (1991) Sens. Actuators A, 25-27, p. 489Sadaoka, Y., Matsuguchi, M., Sakai, Y., Murata, Y., (1991) Chem. Lett., 4, p. 717Sadaoka, Y., Matsuguchi, M., Sakai, Y., (1991) J. Electrochem. Soc., 138, p. 614Sadaoka, Y., Sakai, Y., Murata, Y., (1993) J. Mater. Chem., 3, p. 247Brooks, T.E., Narayanaswamy, R., (1998) Sens. Actuators B, 51, p. 77Raimundo I.M., Jr., Narayanaswamy, R., Quím. Anal., , submitted for publicatio
Cholesteric Liquid Crystals For Detection Of Organic Vapours
No full textStudies on the use of cholesteric liquid crystals (CLCs) as sensing phase for detection of organic vapours in air are described. Stock solutions of 1.0% (w/v) cholesteryl nonanoate (CN) and cholesteryl chloride (CC) were prepared in tetrahydrofuran. Binary mixtures, with compositions ranging from 0.18 to 0.25% of CC and 0.82-0.75% of CN, respectively, were prepared by appropriate mixing of the stock solutions. Films were cast by pipetting three 10μl aliquots of the CLC solution mixture onto a glass disk, whose reverse side was made black to absorb unscattered light. The glass disk was adapted to the common end of a bifurcated optical fibre bundle and placed in a glass vial, which provided a headspace of organic vapours. Measurements were carried out at 27 ± 1 °C, a temperature in which the CLC mixtures maintain their liquid crystalline properties. The responses of the CLC mixtures to vapours of ethanol, acetone, benzene, pyridine and hexane were investigated. The colour of the sensing phases depended on their compositions and exposure to organic vapours gives rise to a change in the optical characteristics of liquid crystals. It was found that the CLC layers containing 0.23-0.25% of CC had no significant change in optical properties when exposed to organic vapours and that ethanol did not cause any optical changes in the liquid crystal layers. Benzene as well as hexane always turned all the coloured liquid crystalline layers to colourless. The CLC layers exhibited different behaviours to vapours of acetone and pyridine. For example, the wavelengths of maximum scattering for the 0.19% CC layer were 530nm in air, 545 nm in pyridine and 580 nm in acetone. The CLC layers showed reversibility. The lifetimes of these layers (interval of time in which the liquid crystalline phase exists, before crystallisation) were investigated by employing acetone and n-hexane vapours. Average lifetimes of 14-15 min were found for films in contact with these vapours, while a lifetime of 205 min was possible when the CLC film was exposed to air. © 2003 Elsevier Science B.V. All rights reserved.9001/03/155257Gardner, J.W., Bartlett, P.N., (1999) Electronic Noses: Principles and Applications, , Oxford University Press, OxfordSotzing, G.A., Briglin, S.M., Grubbs, R.H., Lewis, N.S., Preparation and properties of vapor detector arrays formed from poly(3,4-ethylenedioxy)thiophene-poly(styrene sulfonate)/insulating polymer composites (2000) Anal. Chem., 72, pp. 3181-3190Persaud, K.C., Khaffaf, S.M., Payne, J.S., Pisanelli, A.M., Lee, D.H., Byun, H.G., Sensor array techniques for mimicking the mammalian olfactory system (1996) Sens. Actuators B, 36, pp. 267-273Bariáin, C., Matías, I.R., Romeo, I., Garrido, J., Laguna, M., Behavioral experimental studies of a novel vapochromic materials towards development of optical fiber organic compounds sensor (2001) Sens. Actuators B, 76, pp. 25-31Casalini, R., Wide, J.N., Nagel, J., Oertel, U., Petty, M.C., Organic vapour sensing using thin films of a co-ordination polymer: Comparison of electrical and optical techniques (1999) Sens. Actuators B, 57, pp. 28-34Beenen, A., Niessner, R., Development of a photoacoustic trace gas sensor based on fiber-optically coupled NIR laser diodes (1999) Appl. Spectr., 53, pp. 1040-1044Walt, D.R., Dickinson, T., White, J., Kauer, J., Johnson, S., Engelhardt, H., Sutter, J., Jurs, P., Optical sensor arrays for odor recognition (1998) Biosens. Bioelectron., 13, pp. 697-699Nakagawa, M., Okabayashi, T., Fujimoto, T., Utsunomiya, K., Yamamoto, I., Wada, T., Yamashita, Y., Yamashita, N., A new method for recognizing organic vapor by spectroscopy image on cataluminescence-based gas sensor (1998) Sens. Actuators B, 51, pp. 159-162Granito, C., Wilde, J.N., Petty, M.C., Houghton, S., Iredale, P.J., Toluene vapour sensing using cooper and nickel phthalocyanine Langmuir-Blodgett films (1996) Thin Solid Films, 285, pp. 98-101Brehmer, T.H., Korkas, P.P., Weber, E., Fluorclathrands - A new type of chemical sensor materials for optical vapour detection (1997) Sens. Actuators B, 44, pp. 595-600Sutter, J.M., Jurs, P.C., Neural network classification and quantification of organic vapours based on fluorescence data from a fiber optic sensor array (1997) Anal. Chem., 69, pp. 856-862Dickert, F.L., Haunschild, A., Hofmann, P., Cholesteric liquid crystals for solvent vapour detection - Elimination of cross sensitivity by band shape analysis and pattern recognition (1994) Fresenius J. Anal. Chem., 350, p. 577Aliev, D.F., Gasanov, I.I., Liserskii, L.N., Characteristics of interactions of organic compound vapours with cholesteric liquid crystals (1989) Zh. Fiz. Khim., 63, pp. 558-561Bladek, J., Zmija, J., Detection of organic vapours by means of cholesteric liquid crystals (1982) Biul. Wojsk. Akad. Tech., 31, pp. 51-61Poziomek, F.J., Novak, T.J., Mackay, R.A., Use of liquid crystals as vapor detectors (1973) Mol. Cryst. Liq. Cryst., 27, pp. 175-185Toliver, W.H., Fergason, J.L., Sharpless, E., Hoffman, P.E., Liquid crystal trace contaminant vapor detector with an electronic input (1970) Aerosp. Med., 41, pp. 18-20Raimundo I.M., Jr., Narayanaswamy, R., Evaluation of nafion-crystal violet films for the construction of an optical relative humidity sensor (1999) Analyst, 124, pp. 1623-1627Raimundo I.M., Jr., Narayanaswamy, R., Simultaneous determination of relative humidity and ammonia in air employing an optical fibre sensor and artificial neural network (2001) Sens. Actuators B, 74, pp. 60-6
Ihwg-μnir: A Miniaturised Near-infrared Gas Sensor Based On Substrate-integrated Hollow Waveguides Coupled To A Micro-nir-spectrophotometer
No full textA miniaturised gas analyser is described and evaluated based on the use of a substrate-integrated hollow waveguide (iHWG) coupled to a microsized near-infrared spectrophotometer comprising a linear variable filter and an array of InGaAs detectors. This gas sensing system was applied to analyse surrogate samples of natural fuel gas containing methane, ethane, propane and butane, quantified by using multivariate regression models based on partial least square (PLS) algorithms and Savitzky-Golay 1st derivative data preprocessing. The external validation of the obtained models reveals root mean square errors of prediction of 0.37, 0.36, 0.67 and 0.37% (v/v), for methane, ethane, propane and butane, respectively. The developed sensing system provides particularly rapid response times upon composition changes of the gaseous sample (approximately 2 s) due the minute volume of the iHWG-based measurement cell. The sensing system developed in this study is fully portable with a hand-held sized analyser footprint, and thus ideally suited for field analysis. Last but not least, the obtained results corroborate the potential of NIR-iHWG analysers for monitoring the quality of natural gas and petrochemical gaseous products. This journal is © 2014 the Partner Organisations.1391435723576Zhao, Y., Bai, L., Zhang, Y.N., Hou, W., Wang, Q., (2012) Instrum. Sci. Technol., 40, pp. 385-401De Melas, F., Pustogov, V.V., Croitoru, N., Mizaikoff, B., (2003) Appl. Spectrosc., 57, pp. 600-606Cailteau, C., Pironon, J., De Donato, P., Vinsot, A., Fierz, T., Garnier, C., Barres, O., (2011) Anal. Methods, 3, pp. 877-887Hodgkinson, J., Smith, R., Ho, W.O., Saffell, J.R., Tatam, R.P., (2013) Sens. Actuators, B, 186, pp. 580-588Shemshad, J., Aminossadati, S.M., Kizil, M.S., (2012) Sens. Actuators, B, 171-172, pp. 77-92Shemshad, J., (2013) Sens. Actuators, B, 186, pp. 466-477Wan, B., Small, G.W., (2008) Analyst, 133, pp. 1776-1784Denzer, W., Hancock, G., Islam, M., Langley, C.E., Peverall, R., Ritchie, G.A.D., Taylor, D., (2011) Analyst, 136, pp. 801-806Mizaikoff, B., (2003) Anal. Chem., 75, pp. 258A-267APasquini, C., (2003) J. Braz. Chem. Soc., 14, pp. 198-219Hodgkinson, J., Tatam, R.P., (2013) Meas. Sci. Technol., 24, p. 012004Mizaikoff, B., (2013) Chem. Soc. Rev., 42, pp. 8683-8699Thompson, B.T., Inberg, A., Croitoru, N., Mizaikoff, B., (2006) Appl. Spectrosc., 60, pp. 266-271Kim, S., Menegazzo, N., Young, C., Chan, J., Carter, C., Mizaikoff, B., (2009) Appl. Spectrosc., 63, pp. 331-337Young, C.R., Menegazzo, N., Riley, A.E., Brons, C.H., Disanzo, F.P., Givens, J.L., Martin, J.L., Mizaikoff, B., (2011) Anal. Chem., 83, pp. 6141-6147Pogodina, O.A., Pustogov, V.V., De Melas, F., Haberhauer-Troyer, C., Rosenberg, E., Puxbaum, H., Inberg, A., Mizaikoff, B., (2004) Anal. Chem., 76, pp. 464-468Frey, C.M., Luxenburger, F., Droege, S., Mackoviak, V., Mizaikoff, B., (2011) Appl. Spectrosc., 65, pp. 1269-1274Wilk, A., Carter, J.C., Chrisp, M., Manuel, A.M., Mirkarimi, P., Alameda, J.B., Mizaikoff, B., (2013) Anal. Chem., 85, pp. 11205-11210Fortes, P.R., Wilk, A., Seichter, F., Cajlakovic, M., Koestler, S., Ribishit, V., Wachter, U., Mizaikoff, B., (2013) Proc. SPIE, 8570, pp. 85700Q-1Petruci, J.F.S., Fortes, P.R., Kokoric, V., Wilk, A., Raimundo Jr., I.M., Cardoso, A.A., Mizaikoff, B., (2013) Sci. Rep., 3, p. 3174Petruci, J.F.S., Fortes, P.R., Kokoric, V., Wilk, A., Raimundo Jr., I.M., Cardoso, A.A., Mizaikoff, B., (2014) Analyst, 139, pp. 198-203Perez-Guaita, D., Kokoric, V., Wilk, A., Garrigues, S., Mizaikoff, B., (2014) J. Breath Res., 8, p. 026003http://www.stellarnet.us/products_spectrometers_DWARF-Star-NIR.htm, accessed 19th March 2014http://www.oceanoptics.com/products/NIRQuest.asp, accessed 19th March 2014http://www.jdsu.com/en-us/Custom-Optics/Products/a-z-product-list/Pages/ miniature-near-infrared-Spectrometer.aspx, accessed 19th March 2014O'Brien, N.A., Hulsea, C.A., Friedrich, D.M., Van Milligen, F.J., Von Gunten, M.K., Pfeifer, F., Siesler, H.W., Proc. SPIE 8374 (2012) Next-Generation Spectroscopy Technologies v, , p. 837404Franco, C.M., Determinação de hidrocarbonetos majoritários presentes em no gás natural utilizando espectroscopia no infravermelho próximo e calibração multivariada (2008) Dissertação de Mestrado, , Unicam
Simultaneous Determination Of Zn(ii), Cd(ii) And Hg(ii) In Water
No full textThe use of artificial neural networks (ANNs) as a tool for simultaneous determination of Zn(II), Cd(II) and Hg(II) in water has been investigated, by employing an optode based on the 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (Br-PADAP) complex immobilised on Amberlite XAD-4 resin. Studies were performed with binary and ternary mixtures of Zn(II), Cd(II) and Hg(II) ions in the 0-3.0 mg l-1 range (prepared in pH 8.0 NH4Cl solution), in order to avoid sensing phase saturation. A 0.1 mol l-1 HCl solution was employed to regenerate the optode after each measurement. Reflectance measurements were recorded in the 400-800 nm region after pumping metal ion solution for 1, 1.5, 2.0, 2.5 and 3.0min. Spectra were smoothed by employing a weighted sliding average of three reflectance intensities (weights of 1:3:1) and normalised to the reflectance intensities of the immobilised reagent in the NH4Cl solution. A feed-forward ANN with error back-propagation training algorithm was employed for data treatment. The ANN was initially fed through seven inputs neurons, corresponding to reflectance intensities at 558, 568, 583, 590, 605, 615 and 623nm, and optimised with respect to the number of hidden neurons, momentum and learning rate. Binary mixtures of Zn(II) and Cd(II), and Hg(II) and Cd(II) were employed to evaluate the capability of prediction by the ANN. Measurements were carried out in triplicate leading to standard deviations (expressed in mg l-1) better than 0.29 for Cd(II), 0.38 for Hg(II) and 0.35 for Zn(II) and absolute errors better than 0.14 for Cd(II), 0.31 for Hg(II) and 0.36 for Zn(II). Similar results were obtained when solution mixtures containing all three metal ions were employed in the studies. These results indicate that ANN can be employed for simultaneous determination of metal ions in water. However, attention must be given to the leaching and to the saturation of the sensing phase, which limit the lifetime and analytical range of the sensor, respectively. © 2003 Elsevier Science B.V. All rights reserved.9001/03/15189197Narayanaswamy, R., Optical chemical sensors - Transduction and signal processing (1993) Analyst, 118, pp. 317-322Narayanaswamy, R., Chemical transducer based on fibre optics for environmental monitoring (1993) Sci. Total Environ., 135, pp. 103-113Oehme, I., Wolfbeis, O.S., Optical sensors for determination of heavy metals ions (1997) Mikrochim. Acta, 126, pp. 177-192Klimant, I., Otto, M., A fiber optical sensor for heavy metal ions based on immobilized xylenol orange (1992) Mikrochim. Acta, 108, pp. 11-17Oliveira, W.A., Narayanaswamy, R., A flow cell optosensor for lead based on immobilized dithizone (1992) Talanta, 39, pp. 1499-1503Ahmad, M., Narayanaswamy, R., Development of an optical fibre Al(III) sensor based on immobilised chrome azurol S (1995) Talanta, 42, pp. 1337-1344Madden, J.E., Cardwell, T.J., Cattrall, R.W., Deady, L.W., Nafion-based optode for the detection of metal ions in flow analysis (1996) Anal. Chim. Acta, 319, pp. 129-134Ayora-Cañada, M.J., Pascual-Reguera, M.I., Molina-Díaz, A., Continuous flow-through solid phase spectrophotometric determination of trace amounts of zinc (1998) Anal. Chim. Acta, 375, pp. 71-80Ahmad, M., Hamzah, H., Marsom, E.S., Development of an Hg(II) fibre-optic sensor for aqueous environmental monitoring (1998) Talanta, 47, pp. 275-283Malcik, N., Oktar, O., Ozser, M.E., Caglar, P., Bushby, L., Vaughan, A., Kuwansdi, B., Narayanaswamy, R., Immobilised reagents for optical heavy metal ions sensing (1998) Sens. Actuators, B, 53, pp. 211-221Kuswandi, B., Taib, M.N., Narayanaswamy, R., A new solid state instrument for optical toxic metal ions sensing (1999) Sens. Actuators, A, 76, pp. 183-190Jiang, Z.-T., Li, R., Xi, J.-B., Yi, B.-Q., Determination of trace amounts of manganese by β-cyclodextrin polymer solid phase spectrophotometry using 2-(5-bromo-pyridylazo)-5-diethylaminophenol (1999) Anal. Chim. Acta, 392, pp. 247-253Vaughan, A.A., Narayanaswamy, R., Optical fibre reflectance sensors for the detection of heavy metal ions based on immobilised Br-PADAP (1998) Sens. Actuators, B, 51, pp. 368-376Bos, M., Bos, A., Van der Linden, W.E., Data processing by neural networks in quantitative chemical analysis (1993) Analyst, 118, pp. 323-328Andrew, K.N., Worsfold, P.J., Comparison of multivariate calibration techniques for the quantification of model process streams using diode-array spectrophotometry (1994) Analyst, 119, pp. 1541-1546Natale, C.D., Davide, F., Brunink, J.A.J., D'Amico, A., Vlasov, Y.G., Legin, A.V., Rudnitskaya, A.M., Multicomponent analysis of heavy metal cations and inorganic anions in liquids by a non-selective chalcogenide glass sensor array (1996) Sens. Actuators, B, 34, pp. 539-542Chan, H., Butler, A., Falck, D.M., Freund, M.S., Artificial neural network processing of stripping analysis responses for identifying and quantifying heavy metals in the presence of intermetallic compound formation (1997) Anal. Chem., 69, pp. 2373-2378Alpízar, J., Cladera, A., Cerdà, V., Lastres, E., Garcia, L., Catasús, M., Simultaneous flow injection analysis of cadmium and lead with differential pulse voltammetric detection (1997) Anal. Chim. Acta, 340, pp. 149-158Bos, A., Bos, M., Van der Linden, W.E., Artificial neural networks as a multivariate calibration tool: Modeling the Fe-Cr-Ni system in X-ray fluorescence spectroscopy (1993) Anal. Chim. Acta, 277, pp. 289-295Ni, Y., Trace metal determination by spectrophotometry with a double chromogenic system and a chemometric approach (1993) Anal. Chim. Acta, 284, pp. 199-205Hernández, O., Jiménez, F., Jiménez, A.I., Arias, J.J., Determination of copper and zinc in serum and metal alloys (1996) Analyst, 121, pp. 169-172. , Multicomponent analysis by flow injection using a partial least-square modelBlanco, M., Coello, J., Iturriaga, H., Maspoch, S., Redón, M., Artificial neural networks for multicomponent kinetic determinations (1995) Anal. Chem., 67, pp. 4477-4483Izquierdo, A., Cueto, G.L., Medina, J.F.R., Ubide, C., Simultaneous determination of niobium and tantalum with 4-(2-pyridylazo) resorcinol using partial least squares regression and artificial neural networks (1998) Quim. Anal., 17, pp. 67-74Azubel, M., Fernández, F.M., Tudino, M.B., Troccoli, O.E., Novel application and comparison of multivariate calibration for the simultaneous determination of Cu, Zn and Mn at trace levels using flow injection diode array spectrophotometry (1999) Anal. Chim. Acta, 398, pp. 93-102Gao, L., Ren, S.X., Simultaneous spectrophotometric determination of manganese, zinc and cobalt by kernel partial least-squares method (1998) J. Autom. Chem., 20, pp. 179-183Zhao, S.L., Xia, X.Q., Yu, G., Yang, B., Simultaneous determination of iron and zinc by pH gradient construction in a flow-injection system (1998) Talanta, 46, pp. 845-850Chan, W.H., Lee, A.W.M., Kwong, D.W.J., Liang, Y.Z., Wang, K.M., Simultaneous determination of potassium and sodium by optode spectra and an artificial neural network algorithm (1997) Analyst, 122, pp. 657-661Lin, Z., Booksh, K.S., Burgess, L.W., Kowalski, B.R., Second-order fiber optic heavy metal sensor employing second-order tensorial calibration (1994) Anal. Chem., 66, pp. 2552-2560Kuswandi, B., Vaughan, A.A., Narayanaswamy, R., Simple regression model using an optode for simultaneous determination of zinc and cadmium mixtures in aqueous samples (2001) Anal. Sci., 17, pp. 181-186Raimundo I.M., Jr., Narayanaswamy, R., Simultaneous determination of relative humidity and ammonia in air employing an optical fibre sensor and artificial neural network (2001) Sens. Actuators, B, 74, pp. 60-68Vaughan, A.A., (1998) Optical Fibre Based Heavy Metal Ion Sensing Systems, , PhD. Thesis, DIAS, UMIST, Manchester, UKDespagne, F., Massart, D.L., Neural networks in multivariate calibration (1998) Analyst, 123, pp. 157R-178RCartwright, H.M., (1993) Applications of Artificial Intelligence in Chemistry, , Oxford Chemistry Primers 11, Oxford University Press, Oxfor
A Microfluidic Device With Integrated Fluorimetric Detection For Flow Injection Analysis
No full textThis work describes the development of flow analysis microsystems with integrated fluorimetric detection cells. Channels (width of 300-540 μm and depth of 200-590 μm) were manufactured by deep-UV lithography in urethane-acrylate (UA) resin. Plastic optical fibers (diameter of 250 μm) were coupled to a 2.0-mm-long detection channel in order to guide the excitation radiation from an LED (470 nm) and collect the emitted radiation at a right angle towards a photomultiplier. A single-line miniaturized system, with a total internal volume of 10.4 μL, was evaluated by means of standard fluorescein solutions (0.53-2.66 μmol L-1, pH 8.5). The analytical signals presented a linear relationship in the concentration range studied, with a relative standard deviation of 1.9% (n=5), providing a detection limit of 0.37 μmol L-1 and an analytical frequency of 60 samples/h, using a flow rate of 60 μL min-1. Optical microscopy images and videos acquired in real time for the hydrodynamic injection of 130 and 320 nL of sample solutions indicated the good performance of the proposed sampling strategy. Another microsystem with a total internal volume of 38 μL was developed, incorporating a confluence point for two solutions. This device was applied to the determination of the total concentration of Ca2+ and Mg 2+ in commercial mineral waters using the calcein method. Microscopy images and videos demonstrated the mixing efficiency of the solutions in the microchannels. A linear relationship was observed for the analytical signal in the Ca2+ concentration range from 25 to 125 μmol L-1, with relative standard deviations of 3.5%. The analysis of mineral waters with the proposed system provided results that did not differ significantly from those obtained by the EDTA titration method at a confidence level of 95%. These results demonstrate the viability of developing micro flow injection systems with an integrated fluorimetric detection cell. © 2009 Springer-Verlag.3962715723Dunec, A.F., Cheregi, M., Calatayud, J.M., Mateo, J.V.G., Eneim, H.Y.A., (2003) Crit Rev Anal Chem, 33 (1), pp. 57-68. , 10.1080/713609154 1:CAS:528:DC%2BD3sXitFajurg%3DDanet, A.F., Cheregi, M., Calatayud, J.M., Mateo, J.V.G., Eneim, H.Y.A., (2001) Crit Rev Anal Chem, 31 (3), pp. 191-222. , 10.1080/20014091076749 1:CAS:528:DC%2BD3MXnsVChtbo%3DCerda, V., Estela, J.M., Forteza, R., Cladera, A., Becerra, E., Altimira, P., Sitjar, P., (1999) Talanta, 50 (4), pp. 695-705. , 10.1016/S0039-9140(99)00196-4 1:CAS:528:DyaK1MXmvFCisrw%3DRuzicka, H., Hansen, E.H., (1984) Anal Chim Acta, 161 (1), pp. 1-25. , 10.1016/S0003-2670(00)85773-6 1:CAS:528:DyaL2cXmtVegtbg%3DBecker, H., Locascio, L.E., Polymer microfluidic devices (2002) Talanta, 56 (2), pp. 267-287. , DOI 10.1016/S0039-9140(01)00594-X, PII S003991400100594XLeelasattarathkul, T., Liawruangrath, S., Rayanakorn, M., Liawruangrath, B., Oungpipat, W., Youngvises, N., Greener analytical method for the determination of copper(II) in wastewater by micro flow system with optical sensor (2007) Talanta, 72 (1), pp. 126-131. , DOI 10.1016/j.talanta.2006.10.007, PII S0039914006006722Madou, M.J., (1997) Fundamentals of Microfabrication, , CRC Boca RatonBaeza, M.D.M., Ibanez-Garcia, N., Baucells, J., Bartroli, J., Alonso, J., Microflow injection system based on a multicommutation technique for nitrite determination in wastewaters (2006) Analyst, 131 (10), pp. 1109-1115. , DOI 10.1039/b605043cKruanetr, S., Liawruangrath, S., Youngvises, N., A simple and green analytical method for determination of iron based on micro flow analysis (2007) Talanta, 73 (1), pp. 46-53. , DOI 10.1016/j.talanta.2007.02.032, PII S0039914007001725Kuswandi, B., Nuriman, H.J., Verboom, W., Optical sensing systems for microfluidic devices: A review (2007) Analytica Chimica Acta, 601 (2), pp. 141-155. , DOI 10.1016/j.aca.2007.08.046, PII S0003267007014444Gotz, S., Karst, U., Recent developments in optical detection methods for microchip separations (2007) Analytical and Bioanalytical Chemistry, 387 (1), pp. 183-192. , DOI 10.1007/s00216-006-0820-8Reyes, D.R., Iossifidis, D., Auroux, P.-A., Manz, A., Micro total analysis systems. 1. Introduction, theory, and technology (2002) Analytical Chemistry, 74 (12), pp. 2623-2636. , DOI 10.1021/ac0202435Hata, K., Kichise, Y., Kaneta, T., Imasaka, T., Hadamard transform microchip electrophoresis combined with diode laser fluorometry (2003) Analytical Chemistry, 75 (7), pp. 1765-1768. , DOI 10.1021/ac026330eLeach, A.M., Wheeler, A.R., Zare, R.N., Flow injection analysis in a microfluidic format (2003) Analytical Chemistry, 75 (4), pp. 967-972. , DOI 10.1021/ac026112lDu, W.-B., Fang, Q., Fang, Z.-L., Microfluidic sequential injection analysis in a short capillary (2006) Analytical Chemistry, 78 (18), pp. 6404-6410. , DOI 10.1021/ac060714dDestandau, E., Lefevre, J.-P., Eddine, A.C.F., Desportes, S., Jullien, M.C., Hierle, R., Leray, I., Delaire, J.A., A novel microfluidic flow-injection analysis device with fluorescence detection for cation sensing. Application to potassium (2007) Analytical and Bioanalytical Chemistry, 387 (8), pp. 2627-2632. , DOI 10.1007/s00216-007-1132-3, Metal Vapor GenerationFonseca, A., Raimundo Jr., I.M., Rohwedder, J.J.R., Ferreira, L.O.S., Construction and evaluation of a flow injection micro-analyser based on urethane-acrylate resin (2007) Analytica Chimica Acta, 603 (2), pp. 159-166. , DOI 10.1016/j.aca.2007.09.051, PII S0003267007016121Ruzicka, J., Hansen, E.H., (1983) Anal Chim Acta, 145 (1), pp. 1-15. , 10.1016/0003-2670(83)80043-9 1:CAS:528:DyaL3sXhtFyls7Y%3DRuzicka, J., Hansen, E.H., (1981) Flow Injection Analysis, , Wiley New YorkHart, S.J., Jiji, R.D., (2002) Anal Bioanal Chem, 374 (3), pp. 385-389. , 10.1007/s00216-002-1525-2 1:CAS:528:DC%2BD38Xns1Cltr8%3DFonseca, A., Raimundo Jr., I.M., A multichannel photometer based on an array of light emitting diodes for use in multivariate calibration (2004) Analytica Chimica Acta, 522 (2), pp. 223-229. , DOI 10.1016/j.aca.2004.06.063, PII S0003267004008116Chimpalee, N., Chimpalee, D., Jarungapattananon, R., Lawratchavee, S.E., Burns, D.T., (1993) Anal Chim Acta, 271 (2), pp. 247-251. , 10.1016/0003-2670(93)80052-M 1:CAS:528:DyaK3sXptlCgsA%3D%3
Sampling Strategies In Sequential Injection Analysis: Exploiting The Monosegmented-flow Approach
No full textAn evaluation of different sampling techniques employing sequential injection analysis (SIA) is described. The reaction between Fe(II) and 1,10-phenanthroline, which needs a pH adjustment with acetate buffer and a prior reduction with hydroxylamine solution, was employed. As a general rule, sensitivity, compared to that of the usual SIA technique, can be enhanced with binary sampling, sandwich sampling and monosegmented flow, in that order. Under the employed conditions, signals 13, 31 and 58% higher than those provided by conventional SIA can be obtained with the binary, sandwich and monosegmented sampling, respectively. The monosegmented-flow approach was applied in determining iron in natural waters and results do not differ significantly from those obtained by ICP/AES at the 95% confidence level. The precision was 1.1%, expressed as relative standard deviation obtained by the measurement of nine replicates of 1.0mgl-1 Fe(III) reference solution. Copyright (C) 1998 Elsevier Science B.V.3661-3257262Skeggs, L.T., (1957) Am. J. Clin. Pathol., 28, p. 311Ruzicka, J., Hansen, E.H., (1975) Anal. Chim. Acta, 78, p. 145Pasquini, C., Oliveira, W.A., (1985) Anal. Chem., 57, p. 2575Karlberg, B., Thelander, S., (1978) Anal. Chim. Acta, 98, p. 1Bergamin F, H., Reis, B.F., Jacintho, A.O., Zagatto, E.A.G., (1980) Anal. Chim. Acta, 117, p. 81Olsen, O., Pessenda, L.C.R., Ruzicka, J., Hansen, E.H., (1984) Analyst, 108, p. 905Zagatto, E.A.G., Reis, B.F., Bergamin F, H., Krug, F.J., (1979) Anal. Chim. Acta, 109, p. 41Faria, L.C., Pasquini, C., (1987) Anal. Chim. Acta, 193, p. 19Reis, B.F., Jacintho, A.O., Mortatti, J., Krug, F.J., Zagatto, E.A.G., Bergamin F, H., Pessenda, L.C.R., (1981) Anal. Chim. Acta, 123, p. 221Ruzicka, J., Marshall, G.D., (1990) Anal. Chim. Acta, 237, p. 329Reis, B.F., Giné, M.F., Zagatto, E.A.G., Lima, J.L.F.C., Lapa, R.A., (1994) Anal. Chim. Acta, 293, p. 129Cladera, A., Torrias, C., Gómez, E., Estela, J.M., Cerdá, V., (1995) Anal. Chim. Acta, 302, p. 297Raimundo I.M., Jr., Pasquini, C., (1997) Analyst, 122, p. 103
An Organopalladium-pvc Membrane For Sulphur Dioxide Optical Sensing
No full textThe development of a sensing membrane for the determination of gaseous sulphur dioxide is described. An organopalladium complex, Pd2(dpm) 2Cl2 (dichloro-bis-(diphenylphosphine)-methane dipalladium I), was immobilised in a poly(vinyl chloride) thin film plasticised with ortho-nitrophenyloctylether (o-NPOE). Several membranes were prepared, using 20, 25 and 30% of PVC; 1, 5 and 8% of palladium complex and enough o-NPOE to make a total of 100 mg, which was dissolved in 1.0 mL of THF. The sensing membranes were obtained by manual deposition of 10, 15 and 20 μL of the solution onto cellulose acetate films, which were left to dry for 24 h and then stored in a desiccator sheltered from ambient light. The membrane was placed in an acrylic flow cell, in which the common end of a bifurcated optical fibre bundle was adapted and placed 1 mm from the membrane. Reflectance measurements were performed from 400 to 800 nm, after exposing the membrane to 0 to 500 ppm v of SO2 in air, at a flow rate of 500 mL min -1. The membrane composed of 20% PVC, 72% o-NPOE and 8% palladium complex showed the best performance and the film prepared from 20 μl of solution provided the highest signal (ca 160 mV upon exposure to 500 ppm v SO2). Measurements made at 530 nm showed a linear response range up to 300 ppmv, with a detection limit of 3.5 ppm v. By employing a flow rate of 500 mL min-1, response times (t90%) of 3 and 2 min were obtained for reaction of the membrane with SO2 and for reverse response upon exposure to dry nitrogen, respectively. Although the palladium complex also reacts with carbon monoxide in solution, this interference was not observed for concentrations up to 1000 ppmv of CO. The membrane showed a lifetime of ca. 2 months when stored in a desiccator. © 2004 Elsevier B.V. All rights reserved.1071 SPEC. 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