Colorimetric indicator

Only slightly less accurate ( 0.3—0.5%) and more versatile in scale are other titration techniques. Plutonium maybe oxidized in aqueous solution to PuO " 2 using AgO, and then reduced to Pu" " by a known excess of Fe", which is back-titrated with Ce" ". Pu" " may be titrated complexometricaHy with EDTA and a colorimetric indicator such as Arsenazo(I), even in the presence of a large excess of UO " 2- Solution spectrophotometry (Figs. 4 and 5) can be utilized if the plutonium oxidation state is known or controlled. The spectrophotometric method is very sensitive if a colored complex such as Arsenazo(III) is used. Analytically usehil absorption maxima and molar absorption coefficients ( s) are given in Table 10. Laser photoacoustic spectroscopy has been developed for both elemental analysis and speciation (oxidation state) at concentrations of lO " — 10 M (118). Chemical extraction can also be used to enhance this technique. 

The other method is less accurate but more rapid and involves direct Nessleri2ation of the sample for colorimetric deterrnination. Other colorimetric indicators with more sensitivity, such as indophenol, have been used in place of Nessler s reagent. Ion-selective electrodes have also found use in analysis for trace ammonia (93). 

Direct reading samplers include simple devices such as colorimetric indicating tubes in which a color change indicates the presence of the contaminant in air passed through the tube, or instruments which are more or less specific for a particular substance. In the latter category are carbon monoxide indicators, combustible gas indicators (explosimeters) and mercury vapor meters, as well as a number of other instruments. 

Since no device is completely specific for the substances of interest, care must be taken that interferences do not invalidate the sampling results. Many common gases and vapors react with the same chemicals, or have similar physical properties, so that the instrument may give falsely high or low readings for the substance being sampled. The manufacturer s data for colorimetric indicating tubes lists those substances which may interfere with the desired determination. 

Kirkbright G.F., Narayanaswamy R., Welti N.A., Fiber-optic pH probe based on the use of an immobilized colorimetric indicator, Analyst 1984 109 1052. 

Colorimetric indicator tubes required 5. Flammable vapor detection apparatus ... 

Lungs, brain, blood Gases (carbon monoxide, cyanide) Direct-reading colorimetric indicator tubes Head-space Microdiffusion GC... 

In conjunction with the discussion of the receptor assay system, it is logical to discuss the variations of the plate assay systems and/or growth systems using colorimetric indicators of inhibition of metabolism or growth. 

Carbon monoxide, cyanide Direct reading colorimetric indicator Not available... 

Dichromate test for ethanol, aldehydes, and ketones colorimetric indicator tube (e.g Alcotest) Fujiwaratest fortibhloro-com pounds... 

Colorimetric Indicators, Useful when one of the species is capable of being in rapid equilibrium with a dye substance such that the dye color is affected by the amount of the species present. 

Coupling of A-Fmoc-F2Pmp-OH can be difficult and may not go to completion. Following one standard coupling cycle, the resin should be checked using the Kaiser test, which provides a colorimetric indicator of unreacted terminal amines (25). A step-by-step protocol for performing the Kaiser test is available (26) and alternatives are reported in this book (see Chapters 1 and 5). 

Haines T. A., Akielaszek J. J., Norton S. A., and Davis R. B. (1983) Errors in pH measurement with colorimetric indicators in low alkalinity waters. Hydrobiologia 107, 57-61. 

The discovery and coordination chemistry of phenanthrolines closely followed that of the bipyridines throughout the early twentieth century, much as it does today. F. Blau1 and Gerdiessen2 are credited with the earliest published syntheses of 1,10-phenanthrolines (phen, (1)) in the late nineteenth century. While the colored metal complexes of these compounds had been reported, their utility as colorimetric indicators was not discussed until 1931.3 For the next several decades, phenanthroline derivatives served primarily as colorimetric indicators for many transition metals. Throughout this period, the contributions of G. F. Smith,4-7 F. H. Case,8-10 A. A. Schilt,11 and others toward the chemistry of these complexes resulted in a wealth of synthetic routes for derivatives of (1). The flourishing studies of polypyridyl-coordinated metal complexes provided inspiration for preparing unique phenanthrolines with a wealth of pendant photo- and electro-active molecules.12-16... 

Consistent with much of the early work regarding (1) and its derivatives as colorimetric indicators for transition-metal ions, various phenanthrolines have recently been developed as ion-selective... 

The use of Cp2TiCl2 as a colorimetric indicator for inert atmosphere techniques through the synthesis of the titanium(ni) complex [Cp2Ti(NCMe)2]+ has been described.1135... 

The chimeric genes obtained were used to transform E. coli cells, with each single clone expressing one variant of PQQ-glucose dehydrogenase. The enzyme was isolated and assayed in a buffer containing PQQ to form the holoenzyme, and a colorimetric indicator. Enzymatic activity was assayed for different substrates, and the effect of EDTA and thermal stability were investigated. When... 

Cinchona diimides have also been used to develop a simple colorimetric indicator displacement assay for the determination and chiral discrimination of tartaric acid. Thus, conjugation of 72 with bromophenol blue 73 resulted in the formation of a dark blue complex (A,m lx at 597 nm) that after treatment by an appropriate acid released the protonated form of the indicator with a well-separated absorption maximum at 426 nm. This assay allowed to determine (R,R)-tartaric acid with the detection limit as low as 0.02 mg/ml and efficiently discriminated the enantiomers of tartaric adds,... 

According to the Part 9 of ISO 787, a 10% suspension of filler is made up in freshly distilled water at room temperature and pH measurement of suspension is made. In an ASTM standard method, a suspension is made with warm water and cooled to room temperature for measurement. An alternative method allows one to use colorimetric indicators in the measurement. 

Additional experiments with compleximetric, redox, or precipitation-based titrations have been designed using the same concepts as described above, employing colorimetric indication of the end point. Pertinent details can be found in Ref. 183, in Chapter 2.4.4 (Fig. 2.23), Chapter 4.9... 

Saltzman, B. E. Direct Reading Colorimetric Indicators in Air Sampling Instruments, Cincinnati, OH, Industrial Conference of Governmental Industrial Hygienists 1972 ... 

Direct Reading Colorimetric Indicator Tubes Manual, Akron, OH, American Industrial Hygiene Assoc. 1976... 

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