With pH indicators

The absence of any variation of these characteristics of the electrode reaction with pH indicates that it is the species which predominates in the bulk of the solution which undergoes the electron transfer at the electrode surface. Conversely, a variation shows that the electrode process is... 

Nitrous fiunes reagent 225, 226 Nondestructive detection 42 ff -with fluorescent reagents 44 -with iodine 46 -with pH-indicator 45 Noradrenaline 76, 240, 393 — 396 Norephedrine 76 Norfenefnne 76 Norfenfluramine derivatives 45 1 l-Nor-d -THC-9-carboxy lie acid 289,292 Novonal 339 Nucleosides 364... 

Most probably, the first - but non-fiberoptic - sensors for continuous use where those for pH and for oxygen. It has been known for decades that cellulosic paper can be soaked with pH indicator dyes to give pH indicator strips which, however, leached and thus were of the "single-use" type. The respective research and development is not easily traced back since it is not well documented in the public literature. However, in the 1970s, indicator strips became available where they pH indicator dye was covalently linked to the cellulose matrix, usually via vinylsulfonyl groups. These "nonbleeding" test strips allowed a distinctly improved and continuous pH measurement, initially by visual inspection. In the late 1980 s instruments were made available that enabled the color (more precisely the reflectance) of such sensor strips to be quantified and related to pH. Respective instruments are based on the use of LEDs and are small enough to be useful for field tests in that they can be even hand-held. This simple and low cost detection system is still superior to many of the complicated, if not expensive optical pH sensors that have been described in the past 20 years. 

Also, in complex electrode reactions involving multistep proton and electron transfer steps, the electrochemical reaction order with respect to the H+ or HO may also vary with pH, indicating a change of mechanism with pH. In this respect, the use of schemes of squares outlined in Sect. 2.2 is very useful in the analysis of these complex kinetics [13]. 

Pass this solution over the Dowex 1 column. Wash the column with water. The eluate stays basic (control with pH indicator strip) as long as 8 comes out. About 1 L of water is necessary. 

Total organie acids have also been determined in blood serum by techniques adapted from that deseribed by Van Slyke and Palmer for urine, the titration being done mostly with the aid of a pH meter rather than with pH indicators (C17, D4, G2, Mil, N8, P3). Just as in the case of urine, other authors extract the organie aeids into an organic solvent before titrating them (B7). 

The reaction of the proton with the environment is monitored by its interaction with pH indicators, dye release by the ground-state anion of the proton (4>0 ), or even the geminate recombination of H+ with the excited anion (4>0 ) (for reviews, see references 2 and 3). 

Figure 20.10 Development of realkalisation detected with pH-indicator [28,84]...

A) Measurements with pH-indicating dye neutral red at 548 nm, indicating lumenal acidification after a flash of light. Open triangles CF -depleted tylakoids. Filled triangles same material, but after incubation with DCCD. The bar indicates relative change of transmitted intensity, S lO. ... 

CM-chitin, indicating that the amino group could increase the reactivity of CM-chitin derivatives. The reaction rate of CM-chitin and CM-chitosan with OH radical was found to decrease at lower pH when polymers chains tend to the coiled conformation. In comparison, the rate constant of the reaction of 804" radicals with CM-chitin or CM-chitosan decreased with pH, indicating that CM-chitin or CM-chitosan has a higher reactivity with the 804 radical at low pH due to the protonation of the amino group. 

Brief Review of the Methods for the ApH Measurements with pH-Indicating Probes... 

There are two most frequently used methods for ApH determination in energy-transducing organelles with pH-indicating probes ... 

At an electrolyte pH of 8, the passivation region extended for over 0.5 V. Electrochemical tests were performed on acid etched, bare A1 2024-T3 panels with artificial pits as a control experimental to determine if the increased passivation with increasing electrolyte pH was a result of self-passivation of the bare aluminum alloy surface (Fig. 6.12(b)). The polarization curves for the bare A12024-T3 showed no appreciable passivation and no significant difference with pH, indicating that the passivation observed in the primers was not a result of self-passivation of the substrates, but activity from the primer. This behavior provides important clues not only to the inherent electrochemical properties of the initial coatings, but also the mechanisms responsible for corrosion protection. 

Rinse thoroughly in running water until a neutral test is produced when touched with pH indicator paper... 

Henze (1911) and confirmed by measurements made in 1912 and 1913 with pH indicators (Bruening et al, 1986). Subsequently, it became dear that vanaditim is mainly present in certain spedes of the orders Phlebobranchia and Stohdobranchia. The presence of this element is characteristic of only a limited number of species the most studied are listed in Table 28.13. 

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