Electrophoretic precipitation

Fodisch et al. [156] applied electrophoretic precipitation of industrial catalyst powders at 100 V (DC). After 2 min, uniform deposition of the catalyst powder on the surface was achieved. As an alternative to impregnation methods, palladium was deposited... 

Figure 38-4. Examples of three types of missense mutations resulting in abnormal hemoglobin chains. The amino acid alterations and possible alterations in the respective codons are indicated. The hemoglobin Hikari p-chain mutation has apparently normal physiologic properties but is electrophoretically altered. Hemoglobin S has a p-chain mutation and partial function hemoglobin S binds oxygen but precipitates when deoxygenated. Hemoglobin M Boston, an a-chain mutation, permits the oxidation of the heme ferrous iron to the ferric state and so will not bind oxygen at all.

The oak lignin was electrophoretically analyzed after every precipitation. Under identical conditions (pH 10, KC1 = 0-1 M, sodium... 

As further examples of electrophoretically homogeneous lignins the electrophoretic patterns of cork lignin and commercial indulin purified by fractional precipitation are presented in Fig. 7. 

Electrostatic vs. Chemical Interactions in Surface Phenomena. There are three phenomena to which these surface equilibrium models are applied regularly (i) adsorption reactions, (ii) electrokinetic phenomena (e.g., colloid stability, electrophoretic mobility), and (iii) chemical reactions at surfaces (precipitation, dissolution, heterogeneous catalysis). 

Modifications of surface layers due to lattice substitution or adsorption of other ions present in solution may change the course of the reactions taking place at the solid/liquid interface even though the uptake may be undetectable by normal solution analytical techniques. Thus it has been shown by electrophoretic mobility measurements, (f>,7) that suspension of synthetic HAP in a solution saturated with respect to calcite displaces the isoelectric point almost 3 pH units to the value (pH = 10) found for calcite crystallites. In practice, therefore, the presence of "inert" ions may markedly influence the behavior of precipitated minerals with respect to their rates of crystallization, adsorption of foreign ions, and electrokinetic properties. 

Figure 7.6 Rocket electrophoresis. At pH 8.6 most proteins move towards the anode and precipitation occurs where the antigen and the antibody (in the gel) are in equivalent proportions. The size of the resulting rocket -shaped pattern of precipitate is proportional to the original concentration of antigen. The immunoglobulins show very little electrophoretic mobility at pH 8.6 and so remain in the gel during the process.

Figure 11.15 Immunoelectrophoresis of human serum proteins. The proteins are separated electrophoretically from wells cut in a suitable gel. After electrophoresis, a trough is cut in the gel parallel to the direction of migration and filled with an antiserum. The components are allowed to diffuse for 24-48 hours for precipitation lines to develop. Human serum contains many proteins, among which the immunoglobulins can be identified.

The DNA band is cut from the gel and placed in a dialysis bag containing a small volume of buffer. The bag is placed in an electrophoretic tank and, when the current is switched on, the DNA passes out of the gel. The polarity of the current is reversed for a few moments to cause any DNA actually on the dialysis membrane to move back into the buffer within the bag. The DNA in the buffer is then precipitated with ethanol. 

Urinary GAGs are precipitated before TLC is performed. Separation of the GAGs is achieved by exploiting the different solubility of their calcium salts in various concentrations of ethanol [18, 35, 42]. TLC can provide an inexpensive alternative to electrophoretic techniques, especially when such equipment is not available. 

Alternatively, electrophoretic separation in one direction may be followed by a second electrophoresis in a perpendicular direction, the latter into a gel containing antibodies. This technique is called crossed immunoelectrophoresis and combines high resolution with the possibility of quantification by measuring the area of the precipitate formed. Figure 12.15 is a... 

The protected nonapeptide Boc-Cys(S-Acm)-Phe(4-NHZ)-Phe-Gln-Asn-Cys(S-Acm)-Pro-Arg(7VG-Tos)-Gly-NH2 (500 mg, 370 pmol) was dissolved in anhyd TFA (10 mL) containing DMS (310 pL, 5 mmol) and anisole (540 pL, 5 mmol). The soln was kept for 10 min at 20 °C and then TfOH (1-1.5 mL) was added dropwise until the soln had a violet color. After 4h at 20 °C, the soln was poured into anhyd Et20 (100mL) and the precipitate was either collected by filtration or by decantation, washed with Et20, and dried in vacuo over P205. Paper electrophoresis at pH 1.6 showed one product with electrophoretic mobility of 0.64 (ratio of the distance from the origin for the sample and the reference arginine at the same pH). 

The adsorption of Co(II) at the silica-water interface has been studied as a function of pH, ionic strength, and total Co(II) concentration. The adsorption data, together with electrophoretic mobility and coagulation data suggest that the free aquo Co(II) ion is not specifically adsorbed without participation of surface hydroxyls. Evidence for polymeric Co(OH)2 at the quartz surface is presented together with evidence of mutual coagulation of the quartz and precipitated cobalt hydroxide. 

The variation with pH of the electrophoretic mobility of quartz in 10"4M cobalt (II) perchlorate and a comparison of the mobility of quartz in 10 4M KC1 is shown in Figure 5. Included in Figure 5 is the variation with pH of electrophoretic mobility of precipitated cobalt (II) hydroxide. It can be seen that the silica surface with adsorbed Co (II) acts as cobalt (II) hydroxide for pH values above 8.0. The turbidity vs. pH behavior at 10 4M Co(C104)2 is shown in Figure 6. The two curves represent the behavior for increasing and decreasing pH and within experimental error the curves superimpose. 

ZETA POTENTIAL. The potential across the interface of all solids and liquids. Specifically, the potential across the diffuse layer of ions surrounding a charged colloidal particle, which is largely responsible for colloidal stability. Discharge of the zeta potential, accompanied by precipitation of the colloid, occurs by addition of polyvalent ions of sign opposite to that of the colloidal particles. Zeta potentials can be calculated from electrophoretic mobilities, i.e., the rates at which colloidal particles travel between charged electrodes placed in the solution. 

The same reaction can be done on mucoproteins. These are first precipitated from the protein solution, dialyzed, and concentrated. Then they are separated electrophoretically at pH 4.5 and stained on the paper either with Schiff reagent or with amido black (S22). 

In close vicinity to the salting out phase transition, the effective charge density was determined by conductivity measurements in combination with the known and estimated electrophoretic mobilities of the counterions and the polyions, respectively. The procedure is based on the fact that, shortly before the precipitation of the polyion, the conductivity comprises contributions of polyions, free counterions and added salt. After precipitation of the polyion by reducing the temperature the conductivity is given solely by the supernatant aqueous salt solution, thus the difference Act is due to polyions and free counterions... 

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