Indicator, acid-base fluorescence

See alsa Chemiluminescence Overview Liquid-Phase. Fluorescence Overview. Indicators Acid-Base. 

Acid-base fluorescent indicator (pH 12-14) used as an aq. soln. of salt. Needles + 4H2O (H2O). Sol. H2O. 

Used as an aq. soln. as acid-base fluorescent indicator (pH range 3-4 colour change non fl.- blue pH range 10-12 colour change blue- yellow-green). Needles (H O). 

Used as 0.05% soln. in EtOH as acid-base fluorescent indicator (pH range 9.5-13.0, colour change dark blue - white/blue). Cryst. Mp 241°. p/C, 1.48 pA, 10.71 (25°). 

Amide [13261-51-3]. 5-Amino-2-naphthalenesulfonamide C10H10N2O2S M 222.267 Acid base fluorescent indicator (pH range 1.9-3.9, colour change no fluorescence -> green pH range 9.6-... 

Acid-base fluorescence indicator (pH range 0-1.7 colour change yellowgreen). Used as a 1% soln. in EtOH. Orange cryst. (C H, ). Sol. EtOH, Mc2CO, acids, C H insol. H2O. 

Intermed. in manuf. of ball point pen inks and azo dyes. Resolving agent for amino acids. Used as an aq. soln. of salt as acid-base fluorescent indicator. Cryst. + 1 or 2H2O. Mp 129° (monohydrate), Mp 118° (dihydrate),... 

Me ether [86-68-0]. 6-Methoxy-4-quinolinecarboxylic acid. Quininic acid C H,N03 M 203.197 Used as a satd. aq. soln. as acid-base fluorescent indicator (pH range 4.0-5.0 colour change yellow blue). Yellow prisms (dil. HCl). Spar. sol. H2O sol. acids, alkalis. Mp 285° dec. pA 3.05. Yellow col. in acid soln. Blue fluor. in EtOH destroyed by H2O or acids. 

Alkaloid from Peganum harmala, several Banisteriopsis spp., Passiflora edulis and several other spp. (Zygophyllaceae, Malphigiaceae, Passifloraceae). Used as an acid-base fluorescence indicator (pH 7.2-8.9, colour change blue - yellow). Cryst. Mp 264-265 259°). 

Formerly used as a coupling agent for the prep, of azo dyestuffs and in rubber manuf. Manuf. and use now banned owing to carcinogenic properties. Acid-base fluorescent indicator (pH range 2.8-4.4). Leaflets (H2O). Sol. H.O. Mp 113°. Bp 294°. pA 9.69. Steam-volatile. 

Used as acid-base fluorescent indicator (colour change no fluoresc. yellow pH range 8.6-10.0). Dark red cryst. powder. Sol. EtOH, Me2CO, EtOAc, alkalis si. sol. 

The intensity and colour of the fluorescence of many substances depend upon the pH of the solution indeed, some substances are so sensitive to pH that they can be used as pH indicators. These are termed fluorescent or luminescent indicators. Those substances which fluoresce in ultraviolet light and change in colour or have their fluorescence quenched with change in pH can be used as fluorescent indicators in acid-base titrations. The merit of such indicators is that they can be employed in the titration of coloured (and sometimes of intensely coloured) solutions in which the colour changes of the usual indicators would... 

The interest in colour indicators has recently increased as they are used for the direct determination of pH (acid-base indicators) and free calcium ions (fluorescent derivatives based on the calcium chelator EGTA as metallochromic indicators) in biological systems at cellular level. 

The first pH indicators studied possessed the acid-base site (phenol, aniline, or carboxylic acid) as an integral part of the fluorophore. Structurally, in the most general sense, pH sensitivity is due to a reconfiguration of the fluorophorets re-electron system that occurs on protonation. Consequently, the acid and the base forms often show absorption shifts and also, when the two forms fluoresce, emission shifts or at least, when only one form emits, a pH-dependent fluorescence intensity. This class of compounds has been reviewed 112 and the best structures have to be designed according to the medium probed and the technique used. After a short consideration of physiological pH indicators we will describe the main photophysical processes sensible to protonation. 

If no direct measurement of the fluorescence lifetime is available the relations between the radiative lifetime and the fluorescence and absorption spectra can be used in conjunction with the quantum yield to obtain an indication of the fluorescence lifetime. Birks and Munro (1967) have reviewed the methods of calculating the radiative lifetime. In general these methods are limited to specific groups of compounds. For example, Favaro et al. (1973) applied Stickler and Berg s (1962) formula to the spectral data obtained from an excited state acid-base study of some styrylpyridines and found a lack of quantitative agreement between the measured and calculated lifetimes. 

Emphasis was therefore put on analytical procedures able to determine many elements in parallel and/or requiring almost no previous separation. procedures preferred were X-ray fluorescence using a Am source and Si(Li)-detector, atomic absorption spectrophotometry, gamma spectrometry using tracer isotopes and Ge(Li)-detector and acid-base titrations with recording of the pH-volume derivative. Table 2 summarises the use of these methods for the different elements, and it also gives a rough indication of interferences, sensitivity and accuracy obtained. 

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