Quenching of the fluorescence of substituted benzenes by halomethanes

Khwaja, Haider A.; Semeluk, G. P.; Unger, I.

doi:10.1139/v83-336

Cited by 9 publications

(4 citation statements)

References 5 publications

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“…3 eV-I is obtained from Fig. 3, a value similar to that obtained by us (6,30) for the quenching Solvent viscosity has been postulated to have an effect on the rate of formation and dissociation of exciplexes (3 1). Though not extensive, our study indicates that solvent viscosity does not play an important role in exciplex formation in the C6H6-halocarbon systems.…”

Section: Liquid Phasesupporting

confidence: 82%

Quenching of the singlet and triplet state of benzene in condensed phase

Khwaja¹,

Semeluk²,

Unger³

1984

Can. J. Chem.

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Quenching of the fluorescence of benzene by halocarbons in methanol, ethanol, acetonitrile, and cyclohexane has been investigated. It proceeds via a reversible exciplex intermediate formed between excited singlet benzene and ground state halocarbon. Quenching is controlled by the polarity of the medium. Excited singlet benzene interacts with acetonitrile solvent and a longer wavelength emission due to this complex is observed.The effect of CCl4, CH3CN, CHCl3, and CH3CCl3 on the triplet and singlet excited states of benzene in a methylcyclohexane–isopentane mixture at 77 K has been examined. Carbon tetrachloride and acetonitrile are far more effective quenchers than either CHCl3 or CH3CCl3. In the case of the latter pair enhanced intersystem crossover competes with complex formation.

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Section: Liquid Phasesupporting

confidence: 82%

Quenching of the singlet and triplet state of benzene in condensed phase

Khwaja¹,

Semeluk²,

Unger³

1984

Can. J. Chem.

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“…Quenching of polyaromatics by alkyl or aryl halides has been studied in several cases (21)(22)(23)(24)(25)(26)(27)(28)(29), but not with halothane. In fact it has been stated (30) that this anesthetic does not interfere in the fluorometric oxygen sensor.…”

Section: Resultsmentioning

confidence: 99%

“…The precision of the halothane assay is again the same as that of the halothane evaporator and may become better with a more precise vaporizer. DISCUSSION Quenching of polyaromatics by alkyl or aryl halides has been studied in several cases (21)(22)(23)(24)(25)(26)(27)(28)(29), but not with halothane. In fact it has been stated (30) that this anesthetic does not interfere in the fluorometric oxygen sensor.…”

Section: Indicators a Variety Of Polycyclic Aromatic Hydrocarbonsmentioning

confidence: 99%

Fiber optical fluorosensor for determination of halothane and or oxygen

Wolfbeis¹,

Posch²,

Kroneis³

1985

Anal. Chem.

131

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A flber optical fluoroescence sensor for measurlng concentrations of the wldeiy used lnhalatlon narcotic halothane In the presence of varying concentratlons of oxygen is presented. I t Is based on dynamlc fluorescence quenching and consists of a highly halothane-sensltive indlcator layer exposed to the sample. Interferences by molecular oxygen are taken Into account by a second, polytetrafluoroethylene-covered fluorescent indlcator layer highly sensltlve toward oxygen. Haiothane concentrations can be calculated wlth the help of an extended Stern-Volmer relation (eq 10). The two-sensor technlque presented here allows the determination of halothane, or oxygen, or both wlth a preclslon of 1 5 % for halothane and 13.5% for oxygen In the concentration range encountered in practlce. The probe Is practlcally speclflc for the two anaiytes, since other gases present in inhalatlon gases or blood including carbon monoxlde, dlnltrogen monoxlde, or fluorans do not interfere. The method is thought to be applicable to various other quenching analyte couples as well.Halothane (2-bromo-2-chloro-l,l,l-trifluoroethane) is the inhalation narcotic most frequently used in anesthetics (1). Numerous methods for its determination in breath gas and blood have been described. They are based on quite different analytical techniques such as gas chromatography (2,3), UV (4, 5 ) , mass (6, 71, or NMR spectrometry (81, and surface plasmon resonance (9). A commercially available monitor for anesthetic gases ("EMMA") is based on the absorption of, e.g., halothane, by a thin oil film. The physical parameter measured in this case is the mass of the film which is monitored with a piezoelectric crystal (10). The Datex anesthetic agent monitor measures halothane (or other anesthetic gases) in air via their characteristic IR absorption.Unfortunately, all of these methods either do not allow continuous determination of halothane or are not suitable for use in probes or catheters. We have taken advantage of the observation that halothane is able to quench the fluorescence of polycyclic aromatic hydrocarbons and have devised a fiber-optical sensor suitable for ita continuous monitoring. Since all indicators were also quenched by molecular oxygen-a process that is frequently observed and can be used for sensing oxygen (1 l-l6)-the Stern-Volmer equation has to be modified to take into account multiple quenching. Fluorescence quenching of oxygen-sensitive indicators by halothane has already been noticed (16), a fact that makes all oxygen sensors based on dynamic fluorescence quenching halothane-sensitive and can lead to considerable bias in clinical routine.We report here on the first sensor that is able to probe both oxygen and halothane with practically no mutual interference. Its fiber optical design can be quite similar to that reported by Peterson et al. (16), except that two fibers are required and the mathematics is slightly more complicated. THEORY Halothane in Air. Dynamic fluorescence quenching is known to obey the Stern-Volmer equation (eq l), whi...

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“…Castano et al (1983) suggest that a charge transfer encounter complex in which the quencher acts as an acceptor is responsible for fluorescence quenching of pyrene by organic halides. Polyhaloalkane quenching of fluorescence of substituted benzenes in the vapor phase, on the basis of an extensive set of data, follows a similar mechanism (Khwaja et al, 1983), as d o e s t h e solution-phase quenching of pfluorotoluene fluorescence by amines (Al-Ani and Al-Sabti, 1983). The latter study shows that secondary amines are better quenchers than tertiary or primary amines in acetonitrile.…”

Section: Physical and Instrumental Aspectsmentioning

confidence: 84%