1. Assembly of the Sapphire Cell
<ol>
	<li>Place a 116 size backing ring and 210 size O-ring onto the piston. Verify that O-ring material is compatible with chemicals used during the experiment prior to assembly.
	<ol>
		<li>Some backing rings have a flat and a curved edge. If this is the case, place the flat edge down and the curved edge against the O-ring.</li>
	</ol>
	</li>
	<li>Thread rod into the bottom of the piston using a rod with a threaded tip (Figure 3).</li>
	<li>Wrap the rod with a layer of lab towel (or other nonabrasive lab wipes) to prevent scratching while inserting the piston into the cell.</li>
	<li>Insert the piston in the cell. This step can be difficult, so force must be used. However, it is important to ensure that only the O-ring comes in contact with the cell wall.</li>
	<li>Place an 8210 size backing ring and 210 size O-ring onto the top and bottom end cap (Figure 4). Note: the bottom end cap is the water side with the fitting attached. Be careful that while inserting the end caps, only the O-ring comes in contact with the cell wall.</li>
	<li>Align end caps and insert two bolts through the mounting bracket and through the aluminum spacers.</li>
	<li>Loosely attach nuts.</li>
	<li>Insert the remaining two bolts through aluminum spacers and end cap holes.</li>
	<li>Loosely attach nuts.</li>
	<li>Tighten all nuts to 8-10 ft/lbs torque.</li>
	<li>Mount assembled cell to bracket on rotating shaft by screwing bolts through the bottom of the sapphire cell and then through the rotating shaft. 
	Safety Notes:
	<ol>
		<li>Mount assembled cell so that the opening of the valve on the top end cap (for sample addition) is facing away from the user should a catastrophic failure occur.</li>
		<li>Place the top of the needle valve specifically to face away from the user.</li>
	</ol>
	</li>
	<li>Attach all high pressure fittings, tubing and the thermocouple to top and bottom end cap. Attach high pressure tubing to include a pressure relief valve on the pressurizing side of the sapphire cell. Located the pressure relief valve away from the user and electrical equipment (pressure relief will result in the release of water).</li>
</ol>
2. Safe Handling of the Sapphire Cell
Note:&#160;Do not handle the sapphire cell with bare hands. The transfer of oil from skin can result in micro-cracks or scratches. Do not place the sapphire cell on the lab bench unprotected. The hard surface will likely scratch the cell, or there is risk of the cell rolling. Always inspect the cell for any cracks or defects prior use. Place the air-bath in the down position when operating the cell under pressure. The airbath serves two purposes: (1) to control temperature when necessary and (2) to provide a barrier between the individual and the pressurized contents of the cell in case of catastrophic failure.
<ol>
	<li>Pressure-test the sapphire cell every 12 pressure cycles. A pressure cycle is increasing the pressure above atmospheric and then depressurizing. If not used frequently, pressure-test the cell every four months. Complete pressure testing with the operating side full of water. 
	Safety Note:&#160;Pressure testing must be completed with an incompressible fluid (e.g. water) should the apparatus fail while under pressure.
	<ol>
		<li>Attach water-filled high pressure syringe pump to the sample inlet connection (top of the cell) and fill the cell completely.</li>
		<li>Close the sample inlet valve.</li>
		<li>Run the syringe pump so that a few drops of water leave the high pressure tubing. This is to ensure no air is in the line prior to connection.</li>
		<li>Attach the tubing to the sapphire cell fitting at the bottom of the sapphire cell.</li>
		<li>Fill the bottom cell with water to pressurize and monitor pressure to detect any possible pressure drop.</li>
		<li>Gradually increase pressure 0.1 MPa over the setting of the pressure relief valve. Collect water that is released from the pressure relief valve in a small container.</li>
		<li>Reduce pressure to atmospheric.</li>
		<li>Reset the pressure relief valve and high pressure syringe pumps.</li>
	</ol>
	</li>
</ol>
3. Operation of the Sapphire Cell Apparatus
<ol>
	<li>Fill the high pressure syringe pump approximately half full with water. The amount of water that will be required will be determined by the pressures at which the experiment will be run. Note: Do not completely fill the high pressure syringe pump so that the system may be depressurized if required.</li>
	<li>Run the high pressure syringe pump so that a few drops of water leave the tubing. This is to ensure no air is in the line prior to connection.</li>
	<li>Attach the tubing to the sapphire cell fitting.</li>
	<li>Open the gas inlet valve.</li>
	<li>Fill the cell with water until the piston is at a level that liquid height may be measured with the cathetometer. Note: If the gas inlet valve is not open the system will become pressurized.</li>
	<li>Close the gas inlet valve.</li>
	<li>Attach an air-tight syringe to the sample inlet connection (open) and evacuate the cell by pulling back 10 ml.</li>
	<li>Close the sample inlet valve.</li>
	<li>Apply slight pressure on the airtight syringe while slowly opening the sample inlet valve</li>
	<li>Inject a volume of sample by again using an airtight syringe attached to the sample inlet. Note: depending on the syringe size, the sapphire cell may need to be inverted on the rotating shaft as the airbath cannot be raised completely above the cell.</li>
	<li>Close the valve.</li>
	<li>Mass the syringe before and after addition of the sample. Measure the amount of sample by recording the mass of the syringe before and after addition. There is a small error associated with this method due to an unknown amount of sample left in the tubing and fittings.</li>
	<li>Set air bath at the desired temperature.</li>
	<li>Allow sample to come to equilibrium prior to taking first height measurement with the cathetometer. To ensure equilibrium was reached repeat measurements until no change is observed for at least 3x. The time to reach equilibrium is highly dependent on the system and may range from minutes to hours. Complete a preliminary study in which the system is observed for an extended period of time (24 hr) to ensure equilibrium has been achieved.</li>
	<li>Prime the line with CO2. Add CO2 by first running the high pressure syringe pump to eject any air from the line (not attached the inlet valve).</li>
	<li>Attach the tube to the gas inlet valve.</li>
	<li>Open the gas inlet valve to the sapphire cell. Measure the amount of CO2 added to the system by recording the volume of the high pressure syringe pump before and after CO2 addition.</li>
	<li>Check that the flow-rate on the water high pressure syringe pump is zero (after equilibrium is reached) to ensure there are no leaks.</li>
	<li>Bring pressure to desired value by adjusting the pressurizing fluid (water) with the high pressure syringe pump.</li>
</ol>
4. Cleaning the Sapphire Cell
Following the completion of the experiment, clean the sapphire cell. Clean the cell by repeatedly washing with solvents. Disassemble cell (see Protocol 5) to clean if needed.
<ol>
	<li>Inject approximately 10 ml&#160;of solvent in which the sample is soluble.</li>
	<li>Shake the cell on the rotating shaft to clean the walls and piston.</li>
	<li>Invert the sapphire cell and open the sample inlet valve to empty the contents of the cell.</li>
	<li>Repeat procedure.</li>
	<li>Repeat procedure with acetone as solvent.</li>
	<li>Dry cell: open all valves and heat the airbath.</li>
</ol>
5. Disassembling the Sapphire Cell
<ol>
	<li>Remove the tubing from the fittings. Note: Water will drain from the bottom of the sapphire cell. Removing the piston from the sapphire cell is difficult if it is halfway up the cell once the system is dismantled.</li>
	<li>Run back the water into the high pressure syringe pump.
	<ol>
		<li>Close the sample inlet valve and pressurize the cell with CO2.</li>
		<li>Refill high pressure syringe pump (&#60;5 ml/min).</li>
		<li>Do not refill the high pressure syringe pump if the cell is not pressurized. If the cell is still pressurized after running the water back to the high pressure pump: open the gas inlet valve to vent into the hood.</li>
		<li>Remove the tubing supplying the water from the sapphire cell.</li>
	</ol>
	</li>
	<li>Loosen the nuts and the spacer bolts.</li>
	<li>Take out the bolts. Ensure that no metal comes in contact with the cell.
	<ol>
		<li>If the bolts do not come out easily, tap the bolts.</li>
		<li>Take the end caps straight off without touching the cell.</li>
	</ol>
	</li>
	<li>Remove the piston with the threaded rod wrapped in a towel.</li>
</ol>

<ol>
	<li>Hallett, J. P., Pollet, P., Eckert, C. A., Liotta, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recycling+homogeneous+catalysts+for+sustainable+technology.">Recycling homogeneous catalysts for sustainable technology.</a> Catal. Org. React. 115, 395-404 (2007).</li><li>Hallett, J. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydroformylation+catalyst+recycle+with+gas-expanded+liquids.">Hydroformylation catalyst recycle with gas-expanded liquids.</a> Ind. Eng. Chem. Res. 47, 2585-2589 (2008).</li><li>Pollet, P., Hart, R. J., Eckert, C. A., Liotta, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organic+Aqueous+Tunable+Solvents+(OATS):+A+Vehicle+for+Coupling+Reactions+and+Separations.">Organic Aqueous Tunable Solvents (OATS): A Vehicle for Coupling Reactions and Separations.</a> Accounts Chem. Res. 43, 1237-1245 (2010).</li><li>Fadhel, A. Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exploiting+Phase+Behavior+for+Coupling+Homogeneous+Reactions+with+Heterogeneous+Separations+in+Sustainable+Production+of+Pharmaceuticals.">Exploiting Phase Behavior for Coupling Homogeneous Reactions with Heterogeneous Separations in Sustainable Production of Pharmaceuticals.</a> J. Chem. Eng. Data. 56, 1311-1315 (2011).</li><li>Briones, J. A., Mullins, J. C., Thies, M. C., Kim, B. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ternary+Phase-Equilibria+for+Acetic+Acid-Water+Mixtures+with+Supercritical+Carbon+Dioxide.">Ternary Phase-Equilibria for Acetic Acid-Water Mixtures with Supercritical Carbon Dioxide.</a> Fluid Phase Equilib. 36, 235-246 (1987).</li><li>Wendland, M., Hasse, H., Maurer, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiphase+High-Pressure+Equilibria+of+Carbon-Dioxide-Water-Isopropanol.">Multiphase High-Pressure Equilibria of Carbon-Dioxide-Water-Isopropanol.</a> J. Supercrit. Fluid. 6, 211-222 (1993).</li><li>Traub, P., Stephan, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-Pressure+Phase-Equilibria+of+the+System+CO2+Water+Acetone+Measured+with+a+New+Apparatus.">High-Pressure Phase-Equilibria of the System CO2 Water Acetone Measured with a New Apparatus.</a> Chem. Eng. Sci. 45, 751-758 (1990).</li><li>Peng, D. -. Y., Robinson, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+New+Two-Constant+Equation+of+State.">A New Two-Constant Equation of State.</a> Ind. Eng. Chem. Fund. 15, 59-64 (1976).</li><li>Stryjek, R., Vera, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PRSV+-+An+Improved+Peng-Robinson+Equation+of+State+with+New+Mixing+Rules+for+Strongly+Nonideal+Mixtures.">PRSV - An Improved Peng-Robinson Equation of State with New Mixing Rules for Strongly Nonideal Mixtures.</a> Can. J. Chem. Eng. 64, 334-340 (1986).</li><li>Michelsen, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Modified+Huron-Vidal+Mixing+Rule+for+Cubic+Equations+of+State.">A Modified Huron-Vidal Mixing Rule for Cubic Equations of State.</a> Fluid Phase Equilib. 60, 213-219 (1990).</li><li>Lazzaroni, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-pressure+phase+equilibria+of+some+carbon+dioxide-organic-water+systems.">High-pressure phase equilibria of some carbon dioxide-organic-water systems.</a> Fluid Phase Equilib. 224, 143-154 (2004).</li><li>Lazzaroni, M. J., Bush, D., Brown, J. S., Eckert, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-pressure+vapor-liquid+equilbria+of+some+carbon+dioxide+plus+organic+binary+systems.">High-pressure vapor-liquid equilbria of some carbon dioxide plus organic binary systems.</a> J. Chem. Eng. Data. 50, 60-65 (2005).</li><li>Lazzaroni, M. J., Bush, D., Eckert, C. A., Glaser, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-pressure+vapor-liquid+equilibria+of+argon+plus+carbon+dioxide+2-propanol.">High-pressure vapor-liquid equilibria of argon plus carbon dioxide+2-propanol.</a> J. Supercrit. Fluid. 37, 135-141 (2006).</li><li>Laugier, S., Richon, D., Renon, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+Determination+of+Vapor-Liquid+Equilibiria+and+Volumetric+Properties+of+Ternary+Systems+with+a+New+Experimental+Apparatus.">Simultaneous Determination of Vapor-Liquid Equilibiria and Volumetric Properties of Ternary Systems with a New Experimental Apparatus.</a> Fluid Phase Equilib. 54, 19-34 (1990).</li><li>Fontalba, F., Richon, D., Renon, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+determination+of+vapor--liquid+equilibria+and+saturated+densities+up+to+45+MPa+and+433.">Simultaneous determination of vapor--liquid equilibria and saturated densities up to 45 MPa and 433.</a> 55, 944-951 (1984).</li><li>Lazzaroni, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Georgia Institute of Technology. , (2004).</li><li>Diandreth, J. R., Ritter, J. M., Paulaitis, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental-Technique+for+Determining+Mixture+Compositions+and+Molar+Volumes+of+3+or+More+Equilibrium+Phases+at+Elevated+Pressures.">Experimental-Technique for Determining Mixture Compositions and Molar Volumes of 3 or More Equilibrium Phases at Elevated Pressures.</a> Ind. Eng. Chem. Res. 26, 337-343 (1987).</li></ol>

The authors&#160;do not have competing financial interest or conflicts of interests.

The sapphire cell apparatus is a unique tool for measuring phase behavior without sampling, and thus equilibrium is not disturbed. To ensure accurate repeatable data, there are critical steps in the protocol (Protocol 4 entitled &#8220;Operation of the Sapphire Cell Apparatus&#8221;) that must be followed. For any system in which phase composition is measured, it is critical to reach equilibrium prior to measurement. The sapphire cell is placed on a rotating shaft that facilitates mixing to more rapidly achieve equilibri...

When reactions are being conducted with a hydrophilic catalyst and a hydrophobic substrate to form a hydrophobic product, it is quite common to employ mixed solvents in order to provide a homogeneous reaction system. For example, THF-water and acetonitrile-water are commonly mixed solvent vehicles for these homogenous reaction processes. Ideally, it would be advantageous to develop a process in which the reaction is performed under homogeneous conditions followed by an induced phase split to separate the aqueous and organic solvent components. The hydrophilic catalyst would then be located in the aqueous phase and the hydrophobic product in the organic phase. The overall process would enable a facile separation/isolation of product and a means to recycle the catalyst. Organic Aqueous Tunable Solvents (OATS) provide a vehicle to accomplish this strategy. The first step in developing OATS was to understand the phase behavior of the organic-aqueous solution as a function of organic/water proportion, CO2 pressure and temperature. The efficiency of the phase separation upon addition of CO2&#160;(i.e.&#160;the cross-solubility in each phase) is important to quantify. In fact from a process standpoint, cross-solubility can translate directly to product and catalyst losses in the undesired, respective phases. Therefore, knowing phase composition as a function of pressure is key information for &#8220;real-world&#8221; applications. Sampling methods are available;5-7&#160;however, direct sampling from high pressure systems may alter the equilibrium of the system and result in phase separation or flashing as a result of abrupt changes in pressure or temperature in the sample line. Therefore, a method that does not disturb the system and enables fast acquisition and reproducible data was preferable. The high pressure sapphire cell apparatus is indeed a versatile tool to measure phase behavior without sampling. Using a cathetometer, very precise volume measurements can be recorded. These experimental volume measurements are then used with the Peng-Robinson cubic equation of state (modifications of Stryjek and Vera) and modified Huron-Vidal mixing rules to effectively calculate volume expansion and phase compositions as a function of temperature and pressure8-10. This technique was specifically designed to measure phase equilibria of vapor-liquid-liquid systems. It should be highlighted that the sapphire cell is not suited to study systems that involve solids. The data acquired with the high-pressure sapphire cell guided the choice of experimental conditions for OATS mediated reactions, separations and catalyst recycling. Furthermore, the sapphire cell was also used to (1) measure solvent expansion (or swelling) as a function of CO2 pressure with organic solvents and ionic liquids, (2) determine catalyst partitioning in multiphase systems as a function of pressure, solvent system and temperature and (3) understand phase behavior in complex reaction systems conducted under pressure. Herein, we report (1) the description of high- pressure sapphire cell apparatus, (2) the possible limitations and safety precautions, (3) its operating protocol, and (4) specific proof of principle results.
The high-pressure sapphire cell discussed above was custom made (Figure 1). The equilibrium cell consists of a hollow sapphire cylinder (50.8 mm O.D. x 25.4&#177;0.0001 mm I.D. x 203.2 mm L). The cell is divided into two chambers separated by a piston. The bottom cell contains water used as a pressurizing fluid (dyed blue for demonstrative purposes) and the top cell contains the equilibrium components (Figure 2). The air bath was custom-constructed of Plexiglas to fit specific setting and hood-size. The cell is placed inside a temperature controlled airbath, which is maintained with a digital temperature controller. The temperature of the airbath is monitored with thermocouples (Type K) and digital readouts. There is an additional thermocouple (Type K) inside the sapphire cell that is also monitored with a digital readout. The pressures were measured with a pressure transducer and digital readout. Two high pressure, 500 ml, syringe pumps capable of maintaining pressure up to 10 MPa were required for operation. The first high pressure syringe pump contains water that is used to pressurize the system. The second high pressure pump was used to introduce CO2&#160;(or other gas) to the system. The gas inlet is at the top of the sapphire cell. The pressure is controlled with the high pressure syringe pump to achieve equilibrium pressure on both sides of the piston. The cell is mounted on a rotating shaft, and mixing is achieved by manually rotating the entire cell.
Liquid and vapor volumes are calculated by measuring the height of the meniscus with a micrometer cathetometer. For displacements less than 50 mm, the accuracy is 0.01 mm; for larger displacements, the accuracy is 0.1 mm.

<table border="0" cellpadding="0" cellspacing="0" width="623">
	<colgroup>
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:245px;">Hollow sapphire cylinder</td>
			<td style="width:379px;">50.8 mm O.D. &#215; 25.4&#177;0.0001 mm I.D. &#215; 203.2 mm L</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Pressurizing fluid</td>
			<td>Water</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Syringe pumps</td>
			<td>Teledyne Isco Model 500D</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Digital temperature controller</td>
			<td>Omega CN76000</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Digital readouts</td>
			<td>HH-22 Omega</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Thermocouples</td>
			<td>Omega Type K</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Pressure transducer &#38; readout</td>
			<td>Druck, DPI 260, PDCR 910</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CO2</td>
			<td>SCF grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cathetometer</td>
			<td>Gaertner Scientific corporation or any scientific lab suppliers.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Relief valve</td>
			<td>Spring loaded releive valve (swagelok)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mounting bracket</td>
			<td>UNISTRUT&#160; bracket</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hollow spacers</td>
			<td>3/4 inch</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4 stainless steel bolts, 4 nuts, 2 washers</td>
			<td>3/4 inch</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3 O-rings&#160;</td>
			<td>Kalrez, 210 size&#160;&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3 backing rings&#160;</td>
			<td>116 size for piston; 2 8210 size for end caps</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1 multi-port fitting</td>
			<td>HiP</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">High pressure tubing</td>
			<td>Stainless steel, 1/16 in.</td>
		</tr>
	</tbody>
</table>

high-pressure sapphire cell for phase equilibria measurements of co2/organic/water systems

The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. Specifically, the sapphire cell enables visual data collection from multiple loadings to solve a set of material balances to precisely determine phase composition. Ternary phase diagrams can then be established to determine the proportion of each component in each phase at a given condition. In principle, any ternary system can be studied although ternary systems (gas-liquid-liquid) are the specific examples discussed herein. For instance, the ternary THF-Water-CO2 system was studied at 25 and 40&#160;&#176;C and is described herein. Of key importance, this technique does not require sampling. Circumventing the possible disturbance of the system equilibrium upon sampling, inherent measurement errors, and technical difficulties of physically sampling under pressure is a significant benefit of this technique. Perhaps as important, the sapphire cell also enables the direct visual observation of the phase behavior. In fact, as the CO2 pressure is increased, the homogeneous THF-Water solution phase splits at about 2 MPa. With this technique, it was possible to easily and clearly observe the cloud point and determine the composition of the newly formed phases as a function of pressure.
The data acquired with the sapphire cell technique can be used for many applications. In our case, we measured swelling and composition for tunable solvents, like gas-expanded liquids, gas-expanded ionic liquids and Organic Aqueous Tunable Systems (OATS)1-4. For the latest system, OATS, the high-pressure sapphire cell enabled the study of (1) phase behavior as a function of pressure and temperature, (2) composition of each phase (gas-liquid-liquid) as a function of pressure and temperature and (3) catalyst partitioning in the two liquid phases as a function of pressure and composition. Finally, the sapphire cell is an especially effective tool to gather accurate and reproducible measurements in a timely fashion.

The schematic of the high-pressure sapphire cell is shown in Figure 2, along with a picture of the cell. The sample is in the top cell and in the bottom cell is water with blue dye for demonstration purposes. The liquid components are fed via a syringe and valve, while the CO2 (gas component) is pumped through a high pressure syringe pump. The pressure can be controlled through the piston (the water is also fed via high pressure syringe pump in our setup). The liquid and gas phases can be clea...

Watch this Scientific Journal Video about High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems at JoVE.com

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

The high pressure sapphire cell apparatus is a unique tool to study, without sampling, phase behavior under a wide range of pressures. Using a cathetometer, very precise volume measurements can be recorded to measure liquid expansion and phase composition. Thus, this synthetic method enables the study of (1) phase equilibria of multi-component mixtures and (2) the partition behavior of catalyst or model compounds as a function of pressure.

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. ...

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13.4K Views.  Georgia Institute of Technology. The high pressure sapphire cell apparatus is a unique tool to study, without sampling, phase behavior under a wide range of pressures. Using a cathetometer, very precise volume measurements can be recorded to measure liquid expansion and phase composition. Thus, this synthetic method enables the study of (1) phase equilibria of multi-component mixtures and (2) the partition behavior of catalyst or model compounds as a function of pressure. 

Video: High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

Determination of the Gas-phase Acidities of Oligopeptides

Amino acid residues located at different positions in folded proteins often exhibit different degrees of acidities. For example, a cysteine residue located at or near the N-terminus of a helix is often more acidic than that at or near the C-terminus 1-6. Although extensive experimental studies on the acid-base properties of peptides have been carried out in the condensed phase, in particular in aqueous solutions 6-8, the results are often complicated by solvent effects 7. In fact, most of the active sites in proteins are located near the interior region where solvent effects have been minimized 9,10. In order to understand intrinsic acid-base properties of peptides and proteins, it is important to perform the studies in a solvent-free environment.
We present a method to measure the acidities of oligopeptides in the gas-phase. We use a cysteine-containing oligopeptide, Ala3CysNH2 (A3CH), as the model compound. The measurements are based on the well-established extended Cooks kinetic method (Figure 1) 11-16. The experiments are carried out using a triple-quadrupole mass spectrometer interfaced with an electrospray ionization (ESI) ion source (Figure 2). For each peptide sample, several reference acids are selected. The reference acids are structurally similar organic compounds with known gas-phase acidities. A solution of the mixture of the peptide and a reference acid is introduced into the mass spectrometer, and a gas-phase proton-bound anionic cluster of peptide-reference acid is formed. The proton-bound cluster is mass isolated and subsequently fragmented via collision-induced dissociation (CID) experiments. The resulting fragment ion abundances are analyzed using a relationship between the acidities and the cluster ion dissociation kinetics. The gas-phase acidity of the peptide is then obtained by linear regression of the thermo-kinetic plots 17,18.
The method can be applied to a variety of molecular systems, including organic compounds, amino acids and their derivatives, oligonucleotides, and oligopeptides. By comparing the gas-phase acidities measured experimentally with those values calculated for different conformers, conformational effects on the acidities can be evaluated.

The determination of the gas-phase acidities of cysteine-containing oligopeptides is described. The experiments are performed using a triple quadrupole mass spectrometer. The relative acidities of the peptides are measured using collision-induced dissociation experiments, and the quantitative acidities are determined using the extended Cooks kinetic method.

Amino acid residues located at different positions in folded proteins often exhibit different degrees of acidities. For example, a cysteine residue ...

Synthetic Methodology for Asymmetric Ferrocene Derived Bio-conjugate Systems via Solid Phase Resin-based Methodology

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. The most common techniques utilized are imaging modalities such as Magnetic Resonance Imaging (MRI), Positron Emission Topography (PET), and Computed Topography (CT) and are optimal for understanding the physical structure of the disease but can only be performed once every four to six weeks due to the use of imaging agents and overall cost. With this in mind, the development of &#8220;point of care&#8221; techniques, such as biosensors, which evaluate the stage of disease and/or efficacy of treatment in the clinician&#8217;s office and do so in a timely manner, would revolutionize treatment protocols.1 As a means to exploring ferrocene based biosensors for the detection of biologically relevant molecules2, methods were developed to produce ferrocene-biotin bio-conjugates described herein. This report will focus on a biotin-ferrocene-cysteine system that can be immobilized on a gold surface.

The synthesis of asymmetric species of ferrocene is challenging using solution techniques. This report focuses on the methods carried out to produce a ferrocene-biotin bioconjugate using facile and clean reactions accomplished via solid-phase synthesis. Incorporation of a thiolate moiety is shown to impart the ability for immobilization on gold surfaces.

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. ...

High Precision Zinc Isotopic Measurements Applied to Mouse Organs

We present a procedure to measure with high precision zinc isotope ratios in mouse organs. Zinc is composed of 5 stable isotopes (64Zn, 66Zn, 67Zn, 68Zn and 70Zn) which are naturally fractionated between mouse organs. We first show how to dissolve the different organs in order to free the Zn atoms; this step is realized by a mixture of HNO3 and H2O2. We then purify the zinc atoms from all the other elements, in particular from isobaric interferences (e.g., Ni), by anion-exchange chromatography in a dilute HBr/HNO3 medium. These first two steps are performed in a clean laboratory using high purity chemicals. Finally, the isotope ratios are measured by using a multi-collector inductively-coupled-plasma mass-spectrometer, in low resolution. The samples are injected using a spray chamber and the isotopic fractionation induced by the mass-spectrometer is corrected by comparing the ratio of the samples to the ratio of a standard (standard bracketing technique).&#160;This full typical&#160;procedure produces an isotope ratio with a 50 ppm (2 s.d.) reproducibility.

We present the technique to measure with high precision zinc isotope ratios in mouse organs.

We present a procedure to measure with high precision zinc isotope ratios in mouse organs. Zinc is composed of 5 stable isotopes (64Zn, 66Zn, 67Zn, 68Zn ...

Dissolution Dynamic Nuclear Polarization Instrumentation for Real-time Enzymatic Reaction Rate Measurements by NMR

The main limitation of NMR-based investigations is low sensitivity. This prompts for long acquisition times, thus preventing real-time NMR measurements of metabolic transformations. Hyperpolarization via dissolution DNP circumvents part of the sensitivity issues thanks to the large out-of-equilibrium nuclear magnetization stemming from the electron-to-nucleus spin polarization transfer. The high NMR signal obtained can be used to monitor chemical reactions in real time. The downside of hyperpolarized NMR resides in the limited time window available for signal acquisition, which is usually on the order of the nuclear spin longitudinal relaxation time constant, T1, or, in favorable cases, on the order of the relaxation time constant associated with the singlet-state of coupled nuclei, TLLS. Cellular uptake of endogenous molecules and metabolic rates can provide essential information on tumor development and drug response. Numerous previous hyperpolarized NMR studies have demonstrated the relevancy of pyruvate as a metabolic substrate for monitoring enzymatic activity in vivo. This work provides a detailed description of the experimental setup and methods required for the study of enzymatic reactions, in particular the pyruvate-to-lactate conversion rate in presence of lactate dehydrogenase (LDH), by hyperpolarized NMR.

The sensitivity enhancement provided by dissolution dynamic nuclear polarization (DNP) enables following metabolic processes in real time by NMR and MRI. The characteristics and performances of a dedicated dissolution DNP setup designed for study enzymatic reactions are discussed.

The main limitation of NMR-based investigations is low sensitivity. This prompts for long acquisition times, thus preventing real-time NMR measurements of ...

High Pressure Single Crystal Diffraction at PX^2

In this report we describe detailed procedures for carrying out single crystal X-ray diffraction experiments with a diamond anvil cell (DAC) at the GSECARS 13-BM-C beamline at the Advanced Photon Source. The DAC program at 13-BM-C is part of the Partnership for Extreme Xtallography (PX^2) project. BX-90 type DACs with conical-type diamond anvils and backing plates are recommended for these experiments. The sample chamber should be loaded with noble gas to maintain a hydrostatic pressure environment. The sample is aligned to the rotation center of the diffraction goniometer. The MARCCD area detector is calibrated with a powder diffraction pattern from LaB6. The sample diffraction peaks are analyzed with the ATREX software program, and are then indexed with the RSV software program. RSV is used to refine the UB matrix of the single crystal, and with this information and the peak prediction function, more diffraction peaks can be located. Representative single crystal diffraction data from an omphacite (Ca0.51Na0.48)(Mg0.44Al0.44Fe2+0.14Fe3+0.02)Si2O6 sample were collected. Analysis of the data gave a monoclinic lattice with P2/n space group at 0.35 GPa, and the lattice parameters were found to be: a = 9.496 &#177;0.006 &#197;, b = 8.761 &#177;0.004 &#197;, c = 5.248 &#177;0.001 &#197;, &#946; = 105.06 &#177;0.03&#186;, &#945; = &#947; = 90&#186;.

In this report, we describe detailed procedures for carrying out single crystal X-ray diffraction experiments with a diamond anvil cell at the GSECARS 13-BM-C beamline at the Advanced Photon Source. ATREX and RSV programs are used to analyze the data.

In this report we describe detailed procedures for carrying out single crystal X-ray diffraction experiments with a diamond anvil cell (DAC) at the ...

A Straightforward Method for Glucosinolate Extraction and Analysis with High-pressure Liquid Chromatography (HPLC)

Glucosinolates are a well-studied and highly diverse class of natural plant compounds. They play important roles in plant resistance, rapeseed oil quality, food flavoring, and human health. The biological activity of glucosinolates is released upon tissue damage, when they are mixed with the enzyme myrosinase. This results in the formation of pungent and toxic breakdown products, such as isothiocyanates and nitriles. Currently, more than 130 structurally different glucosinolates have been identified. The chemical structure of the glucosinolate is an important determinant of the product that is formed, which in turn determines its biological activity. The latter may range from detrimental (e.g., progoitrin) to beneficial (e.g., glucoraphanin). Each glucosinolate-containing plant species has its own specific glucosinolate profile. For this reason, it is important to correctly identify and reliably quantify the different glucosinolates present in brassicaceous leaf, seed, and root crops or, for ecological studies, in their wild relatives. Here, we present a well-validated, targeted, and robust method to analyze glucosinolate profiles in a wide range of plant species and plant organs. Intact glucosinolates are extracted from ground plant materials with a methanol-water mixture at high temperatures to disable myrosinase activity. Thereafter, the resulting extract is brought onto an ion-exchange column for purification. After sulfatase treatment, the desulfoglucosinolates are eluted with water and the eluate is freeze-dried. The residue is taken up in an exact volume of water, which is analyzed by high-pressure liquid chromatography (HPLC) with a photodiode array (PDA) or ultraviolet (UV) detector. Detection and quantification are achieved by conducting comparisons of the retention times and UV spectra of commercial reference standards. The concentrations are calculated based on a sinigrin reference curve and well-established response factors. The advantages and disadvantages of this straightforward method, when compared to faster and more technologically advanced methods, are discussed here.

A Straightforward Method for Glucosinolate Extraction and Analysis with High-pressure Liquid Chromatography HPLC

Here, we describe in great detail an established and robust protocol for the extraction of glucosinolates from ground plant materials. After an on-column sulfatase treatment of the extracts, the desulfoglucosinolates are eluted and analyzed by high-pressure liquid chromatography.

Glucosinolates are a well-studied and highly diverse class of natural plant compounds. They play important roles in plant resistance, rapeseed oil ...

Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene

The precise details of the interaction of intense X-ray pulses with matter are a topic of intense interest to researchers attempting to interpret the results of femtosecond X-ray free electron laser (XFEL) experiments. An increasing number of experimental observations have shown that although nuclear motion can be negligible, given a short enough incident pulse duration, electronic motion cannot be ignored. The current and widely accepted models assume that although electrons undergo dynamics driven by interaction with the pulse, their motion could largely be considered &#39;random&#39;. This would then allow the supposedly incoherent contribution from the electronic motion to be treated as a continuous background signal and thus ignored. The original aim of our experiment was to precisely measure the change in intensity of individual Bragg peaks, due to X-ray induced electronic damage in a model system, crystalline C60. Contrary to this expectation, we observed that at the highest X-ray intensities, the electron dynamics in C60 were in fact highly correlated, and over sufficiently long distances that the positions of the Bragg reflections are significantly altered. This paper describes in detail the methods and protocols used for these experiments, which were conducted both at the Linac Coherent Light Source (LCLS) and the Australian Synchrotron (AS) as well as the crystallographic approaches used to analyse the data.

We describe an experiment designed to probe the electronic damage induced in nanocrystals of Buckminsterfullerene (C60) by intense, femtosecond pulses of X-rays. The experiment found that, surprisingly, rather than being stochastic, the X-ray induced electron dynamics in C60 are highly correlated, extending over hundreds of unit cells within the crystals1.

The precise details of the interaction of intense X-ray pulses with matter are a topic of intense interest to researchers attempting to interpret the ...

A Convenient Method for Extraction and Analysis with High-Pressure Liquid Chromatography of Catecholamine Neurotransmitters and Their Metabolites

The extraction and analysis of catecholamine neurotransmitters in biological fluids is of great importance in assessing nervous system function and related diseases, but their precise measurement is still a challenge. Many protocols have been described for neurotransmitter measurement by a variety of instruments, including high-pressure liquid chromatography (HPLC). However, there are shortcomings, such as complicated operation or hard-to-detect multiple targets, which cannot be avoided, and presently, the dominant analysis technique is still HPLC coupled with sensitive electrochemical or fluorimetric detection, due to its high sensitivity and good selectivity. Here, a detailed protocol is described for the pretreatment and detection of catecholamines with high pressure liquid chromatography with electrochemical detection (HPLC-ECD) in real urine samples of infants, using electrospun composite nanofibers composed of polymeric crown ether with polystyrene as adsorbent, also known as the packed-fiber solid phase extraction (PFSPE) method. We show how urine samples can be easily precleaned by a nanofiber-packed solid phase column, and how the analytes in the sample can be rapidly enriched, desorbed, and detected on an ECD system. PFSPE greatly simplifies the pretreatment procedures for biological samples, allowing for decreased time, expense, and reduction of the loss of targets. 
Overall, this work illustrates a simple and convenient protocol for solid-phase extraction coupled to an HPLC-ECD system for simultaneous determination of three monoamine neurotransmitters (norepinephrine (NE), epinephrine (E), dopamine (DA)) and two of their metabolites (3-methoxy-4-hydroxyphenylglycol (MHPG) and 3,4-dihydroxy-phenylacetic acid (DOPAC)) in infants' urine. The established protocol was applied to assess the differences of urinary catecholamines and their metabolites between high-risk infants with perinatal brain damage and healthy controls. Comparative analysis revealed a significant difference in urinary MHPG between the two groups, indicating that the catecholamine metabolites may be an important candidate marker for early diagnosis of cases at risk for brain damage in infants.

We present a convenient solid-phase extraction coupled to high-pressure liquid chromatography (HPLC) with electrochemical detection (ECD) for simultaneous determination of three monoamine neurotransmitters and two of their metabolites in infants' urine. We also identify the metabolite MHPG as a potential biomarker for the early diagnosis of brain damage for infants.

The extraction and analysis of catecholamine neurotransmitters in biological fluids is of great importance in assessing nervous system function and ...

Development and Validation of Chromium Getters for Solid Oxide Fuel Cell Power Systems

Degradation of cathode in solid oxide fuel cells (SOFC) remains a major concern for the long-term performance stability and operational reliability. The presence of gas phase chromium species in air has demonstrated significant cathode performance degradation during long-term exposure due to unwanted compound formation at the cathode and electrolyte interface which retards the oxygen reduction reaction (ORR). We have demonstrated a novel method to mitigate the cathode degradation using chromium getters which capture the gas phase chromium species before it is ingested in the cathode chamber. Low-cost getter materials, synthesized from alkaline earth and transition metal oxides, are coated on the cordierite honeycomb substrate for application in the SOFC power systems. As-fabricated getters have been screened by chromium transpiration tests for 500 h in humidified air atmosphere in presence of chromium vapor. Selected getters have been further validated utilizing electrochemical tests. Typically, electrochemical performance of SOFCs (lanthanum strontium manganite (LSM) &#449; yttria stabilized zirconia (YSZ) &#449; Pt) was measured at 850 &#176;C in the presence and absence of Cr getter. For the 100 h cell tests containing getters, stable electrochemical performance was maintained, whereas the cell performance in the absence of Cr getters rapidly decreased in 10 h. Analyses of Nyquist plots indicated significant increase in the polarization resistance within the first 10 h of the cell operation. Characterization results from posttest SOFCs and getters have demonstrated the high efficiency of chromium capture for the mitigation of cell degradation.

Cathode poisoning from airborne contaminants in trace levels remains a major concern for long-term stability of high-temperature electrochemical systems. We provide a novel method to mitigate the cathode degradations using getters, which capture airborne contaminants at high temperature before entering electrochemically active stack area.

Degradation of cathode in solid oxide fuel cells (SOFC) remains a major concern for the long-term performance stability and operational reliability. The ...

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional &#960;-conjugate Systems

Femtosecond time-resolved stimulated Raman spectroscopy is a promising method of observing the structural dynamics of short-lived transients with near infrared (near-IR) transitions, because it can overcome the low sensitivity of spontaneous Raman spectrometers in the near-IR region. Here, we describe technical details of a femtosecond time-resolved near-IR multiplex stimulated Raman spectrometer that we have recently developed. A description of signal generation and optimization, measurement, data acquisition, and calibration and correction of recorded data is provided as well. We present an application of our spectrometer to analyze the excited-state dynamics of &#946;-carotene in toluene solution. A C=C stretch band of &#946;-carotene in the second lowest excited singlet (S2) state and the lowest excited singlet (S1) state is clearly observed in the recorded time-resolved stimulated Raman spectra. The femtosecond time-resolved near-IR stimulated Raman spectrometer is applicable to the structural dynamics of &#960;-conjugate systems from simple molecules to complex materials.

Details of signal generation and optimization, measurement, data acquisition, and data handling for a femtosecond time-resolved near-IR stimulated Raman spectrometer are described. A near infrared stimulated Raman study on the excited-state dynamics of &#946;-carotene in toluene is shown as a representative application.

Femtosecond time-resolved stimulated Raman spectroscopy is a promising method of observing the structural dynamics of short-lived transients with near ...