Isoconduction

It follows that there must be a condition where the two fluxes Just cancel. At this special value of Du, = 0 and particle and solution are isoconducting. 

Addition of isoconductlng particles to an electrolyte solution does not alter the conductivity. The isoconduction state plays a similar role in non-equilibrium double layers as the point of zero charge does for equilibrium double layers. For large ica Isoconduction is observed for Du = 1. In this case =-Er cos0. 

Consider two eluents with different elution power containing the same eluent ions but different cations with their respective equivalent conductivities A + and A2+. Under isoconductive conditions, the background conductivity Gx of the weaker eluent equals that of the stronger eluent G2. Taking Gx = G2 Eq. (97) may be rearranged so that the concentrations cx and c2 of both eluents are related to the corresponding equivalent conductivities ... 

Fig. 3-126. Comparison of the conductivity change resulting from a pure concentration gradient (A) with that obtained under isoconductive conditions (B). - Separator column Waters IC-Pak Anion eluent see Fig. 3-23 (taken from [135]).

In comparing the concentration gradient concept with subsequent chemical suppression, the chromatogram of various inorganic anions in Fig. 3-127 that was obtained with isoconductive eluents clearly shows the limitation of this technique. Although the analysis time for the separation shown is shorter than under isocratic conditions, an improvement in the resolution between the signals, especially in the first part of the... 

Fig. 3-127. Separation of various inorganic anions with an isoconductive eluent. - Separator column Waters IC-PAK Anion eluent see Table 3-23 (eluent switching at the time of injection) detection direct conductivity injection volume 100 pL solute concentrations 1 ppm fluoride (1), 2 ppm carbonate (2) and chloride (3), 4 ppm nitrite (4), bromide (5), and nitrate (6), 6 ppm orthophosphate (7), 4 ppm sulfate (8) and oxalate (9), 10 ppm chromate (10), and molybdate (11) (taken from [135]).

Figure 8 Formulation-composition bidimensional map indicating isoconductivity lines (left) and region labeling (right) the bold tine is the emulsion inversion locus. (From Ref. 172.)...

The conductivity at the isoconductivity point has to be used for both ion-ex-change resins and membranes. 

The ion activity can be replaced by concentration to a first approximation. The co-ion concentration can be calculated with the Donnan equation based on the capacity of an ion-exchange membrane. It is more difficult to determine the ions mobility ratio. The counterion mobility can be calculated based on isoconductivity point for the appropriate ionic form. The mobility of co-ions can be determined based on a seh-diffusion coefficient measurement. 

The electrical transport properties of crystalline ZrP were studied in different laboratories using isoconductance, a.c.-impedance and... 

Specifically, isoconductance measurements showed that surface proton mobility was higher than that of the bulk protons by a factor of at least 10, while the conductivity of microcrystalline ZrP pellets, determined by a.c.-impedance, was dependent on the size of the crystals and the relative density of the pellets. A systematic investigation was also carried out on pellets at relative humidities (RH) between 5 and 90% . With increased surface hydration the conductivity turned out to be enhanced by about two orders of magnitude (Fig. 16.3a) and the activation energy, determined between 20 and — 20 °C, decreased from 0.52 eV to 0.26 eV (Fig. 16.3b). Based on the reported data it is concluded that the conductivity of crystalline ZrP at 20 °C can vary between 10and 10 ) cm depending on hydration and surface area. However, at 20 °C and 90% RH, the conductivity of highly... 

Table 3.28 Eluent composition for a concentration gradient (A) and an isoconductive eluent (B) according to Figure 3.206.

Figure 3.207 Separation of various inorganic anions with an isoconductive eluent. Separator column Waters IC-PAK Anion eluent see Table 3.28 (eluent switching at the time of injection) detection nonsuppressed conductivity injection volume lOOpL peaks 1 mg/L fluoride (1), 2 mg/L each of carbonate (2) and...

Consider two eluants of different elution strength containing the same eluant anions but different cations with equivalent conductances Xi and X. Under isoconductive conditions, the background conductivity, Gi, of the weaker eluant equals that of the stronger eluant Gz. Given Gi = G2, Eq. (100) may be rearranged, so that the concentrations, Ci and Cz, of both eluants are related to the corresponding equivalent conductances ... 

P.N. Nesterenko and A.V. Ivanov. Detection of transition metals during their separation in an isoconductive pH gradient. Journal of Chromatography A 671 95-99,1994. 

Fig. 12.6 Arrhenius plot of conductivity of BaCeo.9Mo.1O3 a(M = Y, Tm, Yb, Lu, In, or Sc) in moist H2 closed symbols) and O2 (open symbols) in the temperature range of 400°-900°C P(H20)=1.9x 10 Pa. Dashed lines indicate isoconductivity lines in S cm (Reprinted from [5] with permission from Electrochemical Society)...

Dakshinamwite, C., and Chandool, D. E. (1966). Isoconductivity Values and Cation Exchange Capacity of Soils and Clays. Soil Sci. 102(2), 123-130. 

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