Metrohm

FIGURE 4-4 Microprocessor-controlled voltammetric analyzer, in connection with an autosampler. (Courtesy of Metrohm Inc.)... 

Measurement of pH was performed using a Metrohm model 691 pH meter equipped with a Metrohm combined LL micro pH glass electrode calibrated prior to use with pH = 2 and 9 buffers. The checkers found that adjustment to a lower pH led to product with higher amounts of inorganic impurities. The checkers also found that the use of pH paper results in different pH values as compared to the pH meter. 

FIG. 11 Titration plot of alkanesulfonates. Sample 60 wt % of Hostapur SAS 60, monosulfonates fraction contents ca. 140 mg/100 ml (10% MeOH) solution to be titrated 10 ml, 5 ml buffer pH 3 (Merck), 5 ml MeOH, diluted to 100 ml with water titrant 0.004 mol/l TEGOtrant A 100 (l,3-didecyl-2-methyl-imidazolium chloride, Metrohm 6.2317.000) titrator Titrino 716 DMS with automatic titrator 727 and propellant stirrer titration mode dynamic end point titration (DET), high-sense electrode Metrohm 6.0504.15Q, reference electrode Ag/AgCl Metrohm 6.0733.100, EP = end point. 

Metrohm Ltd., High Sense Surfactant Electrode, Herisau, 1993. 

Figure 4.10 Classification of liquid chromatographic methods depending on the polarity of the stationary and mobile phases. After Schaffer el at. [537]. Reproduced by permission of Metrohm AG, Herisau, Switzerland...

Anon, The Whole World of Ion Chromatography, Metrohm AG, Herisau (2004). 

For a few membrane electrodes the ion selectivity is limited, e.g., the Metrohm EA301-Me2+ electrode shows the same sensitivity for various divalent cations in fact, even non-selectivity may be accepted, e.g., where only one type of cation is present as in aqueous hydrofluoric acid where the pH can be determined with a cation-exchange resin electrode40. 

Fig. 2.13. Combined pH glass electrode Metrohm 121 (Courtesy of Metrohm).

Note from the definition is follows that the pH of the isotherm intersection point in Fig. 2.13 represents the isopotential pHf of the Metrohm EA121 combined electrode.)... 

Fig. 2.15. Commercial potentiometers, (a) Metrohm ion activity meter 610 and pH-meter E 588 (b) Orion Model 611 pH meter and Model 811 microprocessor pH meter. 

Although modern polarographs also permit the choice of short drop times (usually down to 0.5 s), the most attractive apparatus for rapid polarography is that supplied by Metrohm (Herisau, Switzerland) Wolf24, who was one of the first promoters of the technique, used the Polarecord E 261R together with the E 354 S polarography stand and its drop time controller (from 0.32 to 0.16 s in five steps) (see Fig. 3.27). Comparison of the normal and rapid (drop time 0.25 s)... 

Fig. 3.27. Conventional and rapid polarography of solution 5 10 4mol Cd2+, Ni2+, Zn2+ in 0.25M KH3/NH4C1, 0.02% gelatine curve a normal (strong damping -> t = 3.9s) and curve b rapid (weak damping - x = 0.6 s) (Courtesy of Metrohm).

In the newer Metrohm Polarecord E 506, which permits the application of almost the complete range of modem polarographic methods (see later) including the rapid technique, the drop time controller (from 6 to 0.4 s in eleven steps) has been built in. 

The data in Fig. 3.38 were obtained with a Metrohm E 506 polarograph (a) and a PARC Model 174 A polarograph (b). 

The Metrohm method may have the advantage that the residual current (iF effect) remains constant during the sampling steps, but the drop still grows (ic effect) both are miniscule effects. The PARC method can be combined with the PARC SMDE technique (see p. 136), which excludes ic alterations due to drop growth during sampling. 

Fig. 3.83. Potentiometric dead-stop (1) and reversed dead-stop (2) end-point titrations, (a) Metrohm Polarecord 626 PARC Model 174A Polarographic Analyzer, (b) Radiometer ISS 820 Ion Scanning System, (c) Tacussel PRG4 Polarograph. 

Pig. 4.20. Utilizable ranges of various voltammetric working electrodes (courtesy of Metrohm). 

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