Flow electrolytic column

As presently under discussion, the SISAK system coupled to a recoil separator [4] (see Sect 2.2.3. and Experimental Techniques ) may provide an alternative approach for continuously separating and detecting two oxidation states in Sg. The flow electrolytic column chromatography developed by Toyoshima et al. [117], which was successfully applied in on-line redox experiments of the heaviest actinides [118], may be adaptable to SISAK and may provide an interesting alternative approach for an electrochemical reduction of Sg. 

Figure 19.10. (a) Principle of electrolytical stimulation of chloroethene biodegradation, (b) Electrochemical prodnction of hydrogen and oxygen down-gradient the electrodes in a model aquifer, (c) ElectrolyticaUy stimulated biodegradation of PCE in a flow-through column system. DC, direct current C, cathodic colnmn A, anodic column in, influent out, effluent n.d., not detected. 

Siemes and Weiss (SI4) investigated axial mixing of the liquid phase in a two-phase bubble-column with no net liquid flow. Column diameter was 42 mm and the height of the liquid layer 1400 mm at zero gas flow. Water and air were the fluid media. The experiments were carried out by the injection of a pulse of electrolyte solution at one position in the bed and measurement of the concentration as a function of time at another position. The mixing phenomenon was treated mathematically as a diffusion process. Diffusion coefficients increased markedly with increasing gas velocity, from about 2 cm2/sec at a superficial gas velocity of 1 cm/sec to from 30 to 70 cm2/sec at a velocity of 7 cm/sec. The diffusion coefficient also varied with bubble size, and thus, because of coalescence, with distance from the gas distributor. 

Gas holdup may be of the same magnitude in the various operations, although for bubble-columns, the presence of electrolytes or surface-active agents appears to be a condition for high gas holdup. The gas residence-time distribution resembles that of a perfect mixer in the stirred-slurry operation, and comes close to piston flow in the others. 

FIGURE 16.2 Representative base peak electropherograms from CZE runs of RPLC fractions, (a) Fraction 15 (5 peptide identifications) and (b) fraction 20 (19 peptide identifications). Column, bare fused silica capillary, 60 cm x 180 pm ODx30pm i.d. separation voltage, 15 kV observed CZE current, 1.91 p.A running electrolyte, 200 mm acetic acid + 10% isopropanol temperature, 22°C injection time, 10 s at 2 psi ( 4 nL total injection volume) supplementary pressure, 2 psi flow rate, 25nL/min spray voltage, 1.5 kV (reprinted with permission from Electrophoresis). 

The GI system is responsible at its most basic level for providing a continual supply of water, electrolytes, minerals, and nutrients. This is achieved by a myriad of specialized cells and coordinated interplay of motility, secretion, digestion, absorption, blood flow, and lymph flow. These components are under elaborate control of the central and enteric nervous systems, endocrine and paracrine regulation of hormones. The highly complex nature of GI function is clearly illustrated by the estimate that 80 to 100 million neurons exist within the enteric nervous system, a number comparable to that found within the spinal column, hence described as a "second brain."171... 

Separation is carried out by applying a high potential (10-30 kV) to a narrow (25-75 pm) fused silica capillary filled with a mobile phase. The mobile phase generally contains an aqueous component and must contain an electrolyte. Analytes migrate in the applied electric field at a rate dependent on their charge and ionic radius. Even neutral analytes migrate through the column due to electro-osmotic flow, which usually occurs towards the cathode. 

Recently flow coulometry, which uses a column electrode for rapid electrolysis, has become popular [21]. In this method, as shown in Fig. 5.34, the cell has a columnar working electrode that is filled with a carbon fiber or carbon powder and the solution of the supporting electrolyte flows through it. If an analyte is injected from the sample inlet, it enters the column and is quantitatively electrolyzed during its stay in the column. From the peak that appears in the current-time curve, the quantity of electricity is measured to determine the analyte. Because the electrolysis in the column electrode is complete in less than 1 s, this method is convenient for repeated measurements and is often used in coulometric detection in liquid chromatography and flow injection analyses. Besides its use in flow coulometry, the column electrode is very versatile. This versatility can be expanded even more by connecting two (or more) of the column electrodes in series or in parallel. The column electrodes are used in a variety of ways in non-aqueous solutions, as described in Chapter 9. 

In order to determine the number of electrons, the flow-coulometric method described in Section 5.6.3 is also useful. The solution of the supporting electrolyte is flowing through the column-type cell for rapid electrolysis (Fig. 5.34) and the potential of the carbon fiber working electrode is kept at a value at which the de-... 

The halogenated method employs a packed column of 1% SP-1000 on Carbopak-B (60-80 mesh) as its primary analytical column. The column is 8-ft X 0.1-in. i.d. It is operated at a helium flow rate of 40 mL/min under programmed temperature conditions of 45 °C isothermal for 3 min, then 8 °C/min to 220 °C, and then held at 220 °C for 15 min or until all compounds have eluted. An electrolytic conductivity detector operated in the halide-specific mode is used for measurement. 

Figure 26-7 Anion separation by ion chromatography with a gradient of electrolytically generated KOH and conductivity detection after suppression. Column Dionex lonPac AS11 diameter = 4 mm flow = 2.0 mL/min. Eluent 0.5 mM KOH for 2.5 min, 0.5 to 5.0 mM KOH from 2.5 to 6 min 5.0 to 38.2 mM KOH from 6 to 18 min. Peaks (1) quinate, (2) F, (3) acetate, (4) propanoate, (5) formate,...

Fig. 4. Analysis of an anion standard solution by IC (a) and CE (b) [48]. IC conditions aVydac 302IC4.6 column, a flow-rate of 2.5 ml/min, an injection volume of 25 xl, an isophthalic acid mobile phase, UV detection at 280 nm. CE conditions an electrolyte of potassium dichromate, sodium tetraborate, boric acid and the DETA (diethylenetriamine) EOF modifier, pH 7.8 65 cmX75 xm I.D. capillary 20 kV indirect UV detection at 280 nm. Anions 1, chloride 2, nitrite 3, chlorate 4, nitrate 5, sulfate 6, thiocyanate 7, perchlorate 8, bromide.

In Fig. 2, the columns were IonPac ICE-AS6 (250X9-mm i.d.), AG9-HC (concentrator, 50X4-mm i.d.) and AG9-HC/AS9-HC (analytical, 250X2-mm i.d.). The ion exclusion sample treatment eluent was deionized water and the flow rate was 0.55 ml/min. The sample volume was 750 pi. The ion exchange eluent was 8.0 mM sodium carbonate and 1.5 mAf sodium hydroxide. The flow rate on the 2-mm analytical column was 0.25 ml/ min. Detection was by suppressed conductivity using the ASRS -I electrolytically regenerated suppressor in the external water mode. 

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