Solution reservoir

The limiting current of the polarogram was proportional to the square root of the height of aqueous-solution reservoir and to the concentration of FMN in the range... 

Figure 1 is a schematic diagram of a basic electrochemical flow deposition systems used for electrodepositing thin-films by EC-ALE, and Figure 2 is a picture showing the solution reservoirs, pumps, valves, and electrochemical cell. 

As deposition of most of the relevant atomic layers involves reduction at relatively low potentials, oxygen has proven to be a major problem. It has been repeatedly shown that if oxygen is not rigorously excluded, deposits are thinner or not formed at all. For this reason, extensive sparging of the solution reservoirs is critical. 

Torsi et al. [395] have carried out a systematic investigation to establish the potential value of such an apparatus. The apparatus is basically an electrothermal device in which the furnace (or the rod) is replaced by a small crucible made of glassy carbon. Figure 5.10 provides an overall view of the apparatus. Figure 5.11 shows a block diagram of the electrolysis circuit the crucible (6) acts a cathode, while the anode is a platinum foil dipped into either the sample solution reservoir (1) or the washing solution reservoir (2). Pre-elecrolysis was performed at constant current with a 500 V dc variable power supply (5). Under these conditions, the cathode potential is not controlled, so that other metals can be codeposited with lead. 

Alternatively, but not commonly, propulsion of the solutions can be achieved by gravity-based units, which rely on the difference in height between the solution(s) reservoir(s) and the flow lines of the manifold. Also, gas-pressure units, which rely on the action of pressure by an inert gas inside the vessels, which contain the solutions, can be used. Both these uncommon propulsion units yield pulse-free flow but require periodic refilling of solution reservoirs and adjustment of the desired flow rate is very difficult. 

Films at NASA GRC were deposited using homemade spray or aerosol-assisted chemical vapor deposition (AACVD) reactors to exploit the lower deposition temperature enabled by the simpler decomposition chemistry for the SSPs.6 9 AACVD is a simple and inexpensive process that offers the advantage of a uniform, large-area deposition, just like metal organic CVD (MOCVD), while also offering the low-temperature solution reservoir typical of spray pyrolysis methods. 

An Ostwald viscometer is similar to an Ubbelohde-type rheometer except that it is simpler in design and is less expensive. A schematic of an Ostwald viscometer is shown in Fig 3.6(b). It is characterized by a lower bulb that acts as a solution reservoir. A solution of known polymer concentration is placed in the lower bulb. A single capillary tube in which the measurement is taken is connected to the bottom of the bulb and to two small bulbs at the top of the capillary. Fluid is forced from the lower bulb through the capillary into the two small bulbs attached to the top of the capillary. There is a line between the two bulbs and at the exit of the lower bulb. The fluid is then allowed to drain back into the lower bulb through the capillary, and the time for the fluid to travel between the two lines is recorded. The time, if there were no end effects, is proportional to the kinematic viscosity (/j/p). 

Assessment of membrane damage was based on performance testing before and after chemical exposure. Testing was conducted in a small flat plate reverse osmosis unit designed to accommodate membrane discs of 45 mm diameter. Feed solution reservoir temperature was maintained at 25 1°C and the brine was continuously recirculated through a filter at the rate of 600 mL/min. Concentration polarization is considered negligible in this cell under these conditions. 

R, solution reservoir DP, N2 gas bubbling EC, electrochemical cell for flow electrolysis M, mixer FC, flow-type optical absorption cell L, light beam D, photodetector CV, control valve. 

Fissure Elution Experiments. The migration characteristics of americium by water transport in fissures fabricated from gray hornblende schist were determined. Fissures not used in the previous sorption experiments were used for these elution experiments. A diagram of the experimental apparatus is shown in Figure 4. Solution reservoirs were attached above the fissures and the small bore tubes affixed to the bottom of the fissures were connected to solution metering pumps. 

The basic elements needed for demineralization experiments are a demineralization cell, solution reservoir and pump, constant voltage power supply, conductivity cell (with temperature regulation) and bridge and voltage and current meters. A typical demineralization assembly is shown in Figure 2. 

The key part of the system is the multiport valve, which interconnects the different parts and solutions used by the system. The common port is connected to a reversible pump with the retention coil placed in between. The pump is connected to the carrier solution reservoir. The common port can access any of the other ports, which lead to sample, standard solutions or reagents, mixing chamber and sensor array, by electrical rotation of the valve. Since the system is bidirectional, volumes can not only be propelled directly to the detector, but also be injected into the retention coil, therefore merging accurate aliquots of different solutions. In order to assure proper mixing of the solutions not only via diffusion... 

The unsteady-state concentrations of lactic acid in the feed reservoir (C ), lactic acid in the stripping solution reservoir (C "), and amine (CA) and the complex (Clx) in the organic solvent reservoir can be found from the... 

In some devices no drilling was performed, but a circular coverslip was used with the end of channel protruding out of the coverslip to reach the solution reservoir [136,137],... 

Reversible bonding of PDMS to PMMA was also achieved [177,178,364]. A PDMS replica containing microchannels (< 100 pm deep) was sealed against a PMMA plate (or a PDMS replica of it) that had deep (300-900 pm) solution reservoirs machined in it [1042]. PDMS was also sealed against a patterned hydrophobic fluorocarbon film [179]. 

After glass bonding, solution reservoirs were created over access holes to hold reagents. The reservoirs were formed by various methods. Most commonly, short plastic or glass tubings were glued to the access holes using epoxy resin. Septa... 

On the other hand, thick PDMS slabs (with punched holes) have been directly placed on the chip and aligned with the access holes to create solution reservoirs [285,329,557,610,745,1017]. Usually, no sealant is needed, but in one report, a silicone sealant was used to attach the PDMS slab [813],... 

In order to avoid any change in the buffer concentration caused by solution evaporation, the solution reservoir was sealed with a thin rubber septum, in which there was a small hole in the septumfor Pt wire electrode insertion [107,148,286]. With this strategy, good reproducibility (RSD of peak area and migration time are less than 1.3% and 1.2%, respectively) can be maintained [107]. 

When high voltages are used, the solution reservoirs should be sufficiently apart to avoid electric arcing [107]. PDMS layers have also been employed to prevent arcing between adjacent electrodes which are inserted in the access holes [1007]. A graphite ink electrode was integrated on a COC chip at the reservoir locations for application of electric voltage for CE [291]. 

Pt electrodes for CE high voltage were embedded into PDMS pre-polymer cast against a mold. Upon curing, the Pt electrodes were well positioned at the solution reservoirs of the PDMS chip [292]. Metal electrodes were pierced through the PDMS well when the chip was mounted [293]. 

For a better flow control using only EOF, secondary hydrodynamic flow (HDF) should be avoided. This could be achieved by ensuring that all solution reservoirs were filled to the same liquid level to avoid HDF [159]. In addition, HDF could be prevented by closing the inlet reservoir to the atmosphere using a valve. In this way, better EOF control and more reproducible CE separation (RSD of migration time decreased by 10-30 times) can be achieved [631]. 

For continuous sample introduction, gated injection was adopted. With EK flow, the analyte continually flowed in parallel with a separation buffer to the analyte waste reservoir (see Figure 4.15). Injection of the sample analyte was achieved by interrupting the flow of the buffer for a short time (known as the injection time) so that the analyte stream was injected. This scheme was achieved by four reservoirs (without considering the reagent reservoir) and two power supplies [317], Gated injection has also been achieved using one power supply and three solution reservoirs [564]. 

FIGURE 7.10 Micromachined glass electrophoresis chip for SCOFT detection (a) schematic showing the solution reservoirs, one electrophoresis channel (4.5 cm long, 15 pm deep, 50 im wide at the top, 20 pm wide at the bottom), and patterned Cr layer with micromachined slits (300 pm-wide, 700 pm-spaced center to center) (b) scanned image of the actual 75-mm x 75-mm chip. The six different channel systems can be seen [698]. Reprinted with permission from the American Chemical Society. 

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