This work was supported by the European Fuel Cells and Hydruogen Joint Undertaking under collaborative project BOR4STORE (Grant Agreement No. 303428) and infrastructure program H2FC (Grant Agreement No. FP7-284522).

1. Apparatus
<ol>
	<li>Use a basic supercritical drying (ScD) apparatus comprised of four primary components connected by high pressure gas tubing: the gas supply, a vacuum system, sensors (temperature and pressure), and the sample environment (which can be submersed in a bath). Ensure that the construction is of high-quality stainless steel valves, fittings, and tubing, pressure-rated to at least 10 MPa within the temperature range between 80-300 K. 
	Note: A schematic is shown in Figure 1.</li>
	<li>For nitrogen ScD (NScD) treatments, ensure that the gas supply is research purity (&#62;99.999%) nitrogen gas fitted with a pressure regulator for outlet pressure control between 0-10 MPa. Attach a 50 L bottle (20 MPa) to the apparatus, and purge the system with pure nitrogen multiple times before use.</li>
	<li>Ensure that the vacuum system is capable of achieving vacuum pressures down to &#60;0.1 Pa and is connected to the apparatus with a fine-control needle valve. Preferably, use an oil-free roughing pump and a molecular-drag turbo pump, placed in series.</li>
	<li>Use at least two pressure sensors for accurate measurement of the pressure during ScD treatments: a low pressure sensor for vacuum measurement and a high pressure sensor to achieve a total measurable pressure range between 0.1-107 Pa.</li>
	<li>Use at least two temperature sensors for the minimal accuracy necessary to perform typical ScD treatments: a sensor in thermal contact with the sample and a sensor within the primary gas dosing manifold for accurate measurements between 77-300 K (e.g., K-type thermocouples).</li>
	<li>Check that the sample holder has an appropriate inner volume to contain the amount of sample necessary for treatment, and is constructed of stainless steel. 
	Note: A lengthened cylindrical design aids in thermal contact with the bath.</li>
	<li>Ensure that the fitting that closes the sample container is appropriate for high pressures and repeated use (e.g., Swagelok VCR). Connect the sample container volume to a valve for isolation from the outside environment via an appropriate length of tubing (the dip tube) for complete immersion of the sample holder into the bath.</li>
</ol>
<img alt="Figure 1" src="/files/ftp_upload/52817/52817fig1.jpg" /> 
Figure 1. Supercritical Nitrogen Drying (NScD) Apparatus. A schematic depiction of the simplified NScD apparatus for use in the typical laboratory: (A) at ambient temperature and (B) after submersion of the sample in the bath. The gas supply for the process described in this work is nitrogen, but this general apparatus is generalizable to other ScD fluids with a critical point lying within a practical range of temperature and pressure, such as CO2. The components are labeled for consistency with the protocol described herein. <a href="https://www.jove.com/files/ftp_upload/52817/52817fig1highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
2. Preparation
<ol>
	<li>Load 0.2-0.5 g of sample (&#947;-Mg(BH4)2, in powder form, following wet-chemical synthesis and standard drying methods) into the sample holder under appropriate conditions, typically in an inert atmosphere such as an argon glovebox, at ambient temperature or below. Close the sample holder (fitting F2) with a filter gasket and then close the valve (valve V4). Transfer the sample holder to the apparatus and attach (fitting F1).</li>
	<li>Open the dosing manifold to vacuum via V2 and evacuate. Open V3 and evacuate. Purge the apparatus with nitrogen via V1 and evacuate via V2. Open V4 and evacuate the sample at RT for up to 24 hr, to reach the minimum pressure of the system (&#60;0.1 Pa).</li>
	<li>Install the sample bath (see Figure 2) around the sample holder. Perform this by raising the bath into position on a scissor lift, or similar mechanism.</li>
	<li>Set the heater to the desired future liquid temperature (Tl, see step 3.1) of 110 K, and continue to evacuate the apparatus until the temperature equilibrates.</li>
</ol>
<img alt="Figure 2" src="/files/ftp_upload/52817/52817fig2.jpg" /> 
Figure 2. Cryogenic Furnace Sample Bath. A schematic depiction (left) and photograph (right) of a cryostatic thermal bath environment appropriate for containing the sample holder during NScD processing, permitting measurement and control of the sample temperature between 77-298 K. <a href="https://www.jove.com/files/ftp_upload/52817/52817fig2highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
3. Supercritical Nitrogen Exposure
<ol>
	<li>For NScD processing of &#947;-Mg(BH4)2, (the subject of demonstration in this protocol) select a liquid temperature (Tl) of 110 K. This corresponds to a moderate liquid solvent density (~0.6 g ml-1); Adjust as necessary for the application of this protocol to other NScD treatment processes (see the Note below).</li>
	<li>Close off the system to vacuum by closing V2. Throttle open V1 slowly, allowing the pressure to increase into the liquid region of the phase diagram. Equilibrate the system at 2 MPa and Tl.</li>
	<li>Soak the sample in liquid N2 for 4 hr.</li>
	<li>Set the heater to 150 K with a ramp &#8804;2 K min-1. Allow the pressure to increase no higher than the maximum rated pressure of the apparatus (this Pmax should be &#8805;10 MPa); if necessary, carefully vent the excess pressure to vacuum via V2. Equilibrate the system at Pmax and 150 K.</li>
	<li>Soak the sample in supercritical N2 for 1 hr.</li>
</ol>
<img alt="Figure 3" src="/files/ftp_upload/52817/52817fig3.jpg" /> 
Figure 3. Phase Diagram of Nitrogen. A detailed phase diagram of nitrogen, where the fluid density (shown in linear greyscale) is calculated using Refprop (a modified Webb-Benedict-Rubin equation of state).41 Various lines of constant density are shown in purple. The solid phase boundaries and boiling transition lines are shown in red. The blue lines indicate the boundary of the region of the phase diagram that is relevant for drying or extraction processing using N2. <a href="https://www.jove.com/files/ftp_upload/52817/52817fig3highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Note: For the application of this protocol to other materials, establish an appropriate NScD treatment scheme by choosing the conditions necessary for effective solvation of the target species. Refer to the phase diagram of N2, shown in Figure 3. To achieve a high fluid density in the liquid phase (e.g., 0.8-1 g ml-1), select a Tl of 80-90 K. For moderate liquid density (e.g., 0.6-0.8 g ml-1), select a Tl of 90-115 K. A trial and error approach may be necessary.
4. Supercritical Nitrogen Release
<ol>
	<li>Carefully crack the system to vacuum by throttling V2, allowing the pressure to decrease as slowly as possible. Repeatedly crack the system to higher vacuum rates as necessary to achieve a gradual decline to high vacuum (&#60;0.1 Pa) in the approximate time span of 12-24 hr.</li>
	<li>Remove the sample bath and fully open V2 to completely evacuate the sample. Equilibrate at RT and high vacuum (&#60;0.1 Pa).</li>
	<li>Degas the sample at RT and &#60;0.1 Pa for 1-24 hr, as desired.</li>
</ol>
5. Post Treatment
<ol>
	<li>Close valves V3 and V4, and remove the sample holder from the apparatus (fitting F1).</li>
	<li>Transfer the sample holder to an inert environment for handling, such as an argon-filled glovebox. Remove the sample from the sample holder (fitting F2) and store in a sealed container at ambient temperature or below.</li>
</ol>

<ol>
	<li>McHugh, M. A., Krukonis, V. 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> Supercritical Fluid Extraction. , (1986).</li><li>Schneider, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physicochemical+Principles+of+Extraction+with+Supercritical+Gases.">Physicochemical Principles of Extraction with Supercritical Gases.</a> Angew. Chem. lnt. Ed. 17, 716-727 (1978).</li><li>Williams, D. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+with+Supercritical+Gases.">Extraction with Supercritical Gases.</a> Chem. Eng. Sci. 36 (11), 1769-1788 (1981).</li><li>Eckert, C. A., Knutson, B. I., Debenedetti, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supercritical+fluids+as+solvents+for+chemical+and+materials+processing.">Supercritical fluids as solvents for chemical and materials processing.</a> Nature. 383, 313-318 (1996).</li><li>Cooper, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymer+synthesis+and+processing+using+supercritical+carbon+dioxide.">Polymer synthesis and processing using supercritical carbon dioxide.</a> J. Mater. Chem. 10, 207-234 (2000).</li><li>Klesper, E., Corwin, A. H., Turner, D. 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+gas+chromatography+above+critical+temperatures.">High pressure gas chromatography above critical temperatures.</a> J. Org. Chem. 27, 700-701 (1962).</li><li>Tucker, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solvent+Density+Inhomogeneities+in+Supercritical+Fluids.">Solvent Density Inhomogeneities in Supercritical Fluids.</a> Chem. Rev. 99 (2), 391-418 (1999).</li><li>Hubert, P., Vitzthum, O. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluid+Extraction+of+Hops,+Spices,+and+Tobacco+with+Supercritical+Gases.">Fluid Extraction of Hops, Spices, and Tobacco with Supercritical Gases.</a> Angew. Chem. Int. Ed. 17 (10), 710-715 (1978).</li><li>Zosel, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+with+Supercritical+Gases:+Practical+Applications.">Separation with Supercritical Gases: Practical Applications.</a> Angew. Chem. Int. Ed. 17 (10), 702-709 (1978).</li><li>Nelson, A. P., Farha, O. K., Mulfort, K. L., Hupp, J. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supercritical+Processing+as+a+Route+to+High+Internal+Surface+Areas+and+Permanent+Microporosity+in+Metal&#8722;Organic+Framework+Materials.">Supercritical Processing as a Route to High Internal Surface Areas and Permanent Microporosity in Metal&#8722;Organic Framework Materials.</a> J. Am. Chem. Soc. 131, 458-460 (2009).</li><li>Liu, B., Wong-Foy, A. G., Matzger, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+and+enhanced+activation+of+microporous+coordination+polymers+by+flowing+supercritical+CO2.">Rapid and enhanced activation of microporous coordination polymers by flowing supercritical CO2.</a> Chem. Commun. 49, 1419-1421 (2013).</li><li>Cooper, A. I., Rosseinsky, 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=Metal&#8211;organic+frameworks:+improving+pore+performance.">Metal&#8211;organic frameworks: improving pore performance.</a> Nat. Chem. 1, 26-27 (2009).</li><li>Totten, R. K., 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=Enhanced+Catalytic+Activity+through+the+Tuning+of+Micropore+Environment+and+Supercritical+CO2+Processing:+Al(Porphyrin)-Based+Porous+Organic+Polymers+for+the+Degradation+of+a+Nerve+Agent+Simulant.">Enhanced Catalytic Activity through the Tuning of Micropore Environment and Supercritical CO2 Processing: Al(Porphyrin)-Based Porous Organic Polymers for the Degradation of a Nerve Agent Simulant.</a> J. Am. Chem. Soc. 135, 11720-11723 (2013).</li><li>Savage, P. E., Gopalan, S., Mizan, T. I., Martino, C. J., Brock, E. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactions+at+supercritical+conditions:+Applications+and+fundamentals.">Reactions at supercritical conditions: Applications and fundamentals.</a> AIChE J. 41 (7), 1723-1778 (1995).</li><li>Baiker, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supercritical+Fluids+in+Heterogeneous+Catalysis.">Supercritical Fluids in Heterogeneous Catalysis.</a> Chem. Rev. 99 (2), 453-474 (1999).</li><li>Jessop, P. G., Ikariya, T., Noyori, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Homogeneous+Catalysis+in+Supercritical+Fluids.">Homogeneous Catalysis in Supercritical Fluids.</a> Chem. Rev. 99 (2), 475-494 (1999).</li><li>Giddings, J. C., Myers, M. N., McLaren, L., Keller, R. 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+Gas+Chromatography+Of+Nonvolatile+Species.">High Pressure Gas Chromatography Of Nonvolatile Species.</a> Science. 162 (3849), 67-73 (1968).</li><li>Gere, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supercritical+Fluid+Chromatography.">Supercritical Fluid Chromatography.</a> Science. 222, 253-259 (1983).</li><li>Kistler, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coherent+Expanded+Aerogels+and+Jellies.">Coherent Expanded Aerogels and Jellies.</a> Nature. 127, 741-741 (1931).</li><li>Biener, 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=Advanced+carbon+aerogels+for+energy+applications.">Advanced carbon aerogels for energy applications.</a> Energy Environ. Sci. 4, 656-667 (2011).</li><li>Mor&#232;re, 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=Deposition+of+Pd+into+mesoporous+silica+SBA-15+using+supercritical+carbon+dioxide.">Deposition of Pd into mesoporous silica SBA-15 using supercritical carbon dioxide.</a> J. Supercrit. Fluids. 56 (2), 213-222 (2011).</li><li>Sathish, M., Mitani, S., Tomai, T., Honma, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supercritical+fluid+assisted+synthesis+of+N-doped+graphene+nanosheets+and+their+capacitance+behavior+in+ionic+liquid+and+aqueous+electrolytes.">Supercritical fluid assisted synthesis of N-doped graphene nanosheets and their capacitance behavior in ionic liquid and aqueous electrolytes.</a> J. Mater. Chem. A. 2, 4731-4738 (2014).</li><li>Toews, K. L., Shroll, R. M., Wai, C. M., Smart, N. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=pH-Defining+Equilibrium+between+Water+and+Supercritical+CO2.+Influence+on+SFE+of+Organics+and+Metal+Chelates.">pH-Defining Equilibrium between Water and Supercritical CO2. Influence on SFE of Organics and Metal Chelates.</a> Anal. Chem. 67 (22), 4040-4043 (1995).</li><li>Barbaras, G., Barbaras, G. D., Finholt, A. E., Schlesinger, H. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cause+Of+Explosions+Occasionally+Observed+During+Evaporation+Of+Solutions+Of+Aluminum+Hydride+And+Related+Compounds.">Cause Of Explosions Occasionally Observed During Evaporation Of Solutions Of Aluminum Hydride And Related Compounds.</a> J. Am. Chem. Soc. 70, 877 (1948).</li><li>Burr, J. G., Brown, W. G., Heller, H. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Reduction+of+Carbon+Dioxide+to+Formic+Acid.">The Reduction of Carbon Dioxide to Formic Acid.</a> J. Am. Chem. Soc. 72 (6), 2560-2562 (1950).</li><li>Hugelshofer, C. L., 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=Gas&#8722;Solid+Reaction+of+Carbon+Dioxide+with+Alanates.">Gas&#8722;Solid Reaction of Carbon Dioxide with Alanates.</a> J. Phys. Chem. C. 118, 15940-15945 (2014).</li><li>Orimo, S. I., Nakamori, Y., Eliseo, J. R., Z&#252;ttel, A., Jensen, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complex+Hydrides+for+Hydrogen+Storage.">Complex Hydrides for Hydrogen Storage.</a> Chem. Rev. 107 (10), 4111-4132 (2007).</li><li>Gross, K. J., Thomas, G. J., Jensen, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Catalyzed+alanates+for+hydrogen+storage.">Catalyzed alanates for hydrogen storage.</a> J. Alloys Compd. 330-332, 683-690 (2002).</li><li>Li, H. W., Yan, Y., Orimo, S. I., Z&#252;ttel, A., Jensen, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+Progress+in+Metal+Borohydrides+for+Hydrogen+Storage.">Recent Progress in Metal Borohydrides for Hydrogen Storage.</a> Energies. 4 (1), 185-214 (2011).</li><li>Frankcombe, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proposed+Mechanisms+for+the+Catalytic+Activity+of+Ti+in+NaAlH4.">Proposed Mechanisms for the Catalytic Activity of Ti in NaAlH4.</a> Chem. Rev. 112, 2164 (2012).</li><li>Vajo, J. J., Olson, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+storage+in+destabilized+chemical+systems.">Hydrogen storage in destabilized chemical systems.</a> Scr. Mater. 56, 829 (2007).</li><li>Zhang, Y., 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=LiBH4+nanoparticles+supported+by+disordered+mesoporous+carbon:+Hydrogen+storage+performances+and+destabilization+mechanisms.">LiBH4 nanoparticles supported by disordered mesoporous carbon: Hydrogen storage performances and destabilization mechanisms.</a> Int. J. Hyd. Energ. 32 (16), 3976-3980 (2007).</li><li>Christian, M. L., Aguey-Zinsou, K. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Core&#8211;Shell+Strategy+Leading+to+High+Reversible+Hydrogen+Storage+Capacity+for+NaBH4.">Core&#8211;Shell Strategy Leading to High Reversible Hydrogen Storage Capacity for NaBH4.</a> ACS Nano. 6 (9), 7739-7751 (2012).</li><li>Stadie, N. 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=Supercritical+N2+Processing+as+a+Route+to+the+Clean+Dehydrogenation+of+Porous+Mg(BH4)2.">Supercritical N2 Processing as a Route to the Clean Dehydrogenation of Porous Mg(BH4)2.</a> J. Am. Chem. Soc. 136 (23), 8181-8184 (2014).</li><li>Borgschulte, A., 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=Impurity+Gas+Analysis+of+the+Decomposition+of+Complex+Hydrides.">Impurity Gas Analysis of the Decomposition of Complex Hydrides.</a> J. Phys. Chem. C. 115, 17220-17226 (2011).</li><li>Filinchuk, Y., 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=Porous+and+Dense+Magnesium+Borohydride+Frameworks:+Synthesis,+Stability,+and+Reversible+Absorption+of+Guest+Species.">Porous and Dense Magnesium Borohydride Frameworks: Synthesis, Stability, and Reversible Absorption of Guest Species.</a> Angew. Chem. Int. Ed. 50, 11162-11166 (2011).</li><li>Li, H. W., 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=Dehydriding+and+rehydriding+processes+of+well-crystallized+Mg(BH4)2+accompanying+with+formation+of+intermediate+compounds.">Dehydriding and rehydriding processes of well-crystallized Mg(BH4)2 accompanying with formation of intermediate compounds.</a> Acta Mater. 56 (6), 1342-1347 (2008).</li><li>Sch&#252;th, F., Bogdanovic, B., Felderhoff, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+metal+hydrides+and+complex+hydrides+for+hydrogen+storage.">Light metal hydrides and complex hydrides for hydrogen storage.</a> Chem. Comm. , 2249-2258 (2004).</li><li>Vitillo, J. G., Groppo, E., Bardaj&#237;, E. G., Baricco, M., Bordiga, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+carbon+dioxide+recycling+by+reaction+with+&#947;-Mg(BH4)2.">Fast carbon dioxide recycling by reaction with &#947;-Mg(BH4)2.</a> Phys. Chem. Chem. Phys. 16, 22482-22486 (2014).</li><li>Paskevicius, M., 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=In-Situ+X-ray+Diffraction+Study+of+&#947;-Mg(BH4)2+Decomposition.">In-Situ X-ray Diffraction Study of &#947;-Mg(BH4)2 Decomposition.</a> J. Phys. Chem. C. 116, 15321-15240 (2012).</li><li>Lemmon, E. W., Huber, M. L., McLinden, M. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NIST+standard+reference+database+23:+reference+fluid+thermodynamic+and+transport+properties.">NIST standard reference database 23: reference fluid thermodynamic and transport properties.</a> Standard Reference Data Program. , (2008).</li><li>Moquin, P. H. L., Temelli, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetic+modeling+of+hydrolysis+of+canola+oil+in+supercritical+media.">Kinetic modeling of hydrolysis of canola oil in supercritical media.</a> J. Supercrit. Fluid. 45, 94-101 (2008).</li><li>Myers, M. N., Giddings, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultra-High-Pressure+Gas+Chromatography+in+Micro+Columns+to+2000+Atmospheres.">Ultra-High-Pressure Gas Chromatography in Micro Columns to 2000 Atmospheres.</a> Sep. Sci. 1 (6), 761-776 (1966).</li><li>McLeary, E. E., Jansen, J. C., Kapteijn, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zeolite+based+films,+membranes+and+membrane+reactors:+Progress+and+prospects.">Zeolite based films, membranes and membrane reactors: Progress and prospects.</a> Microporous Mesoporous Mater. 90, 198-220 (2006).</li><li>Richter, B., Ravnsb&#230;k, D. B., Tumanov, N., Filinchuk, Y., Jensen, T. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Manganese+borohydride;+synthesis+and+characterization.">Manganese borohydride; synthesis and characterization.</a> Dalton Trans. , (2015).</li><li>Liang, S., Tilotta, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+of+petroleum+hydrocarbons+from+soil+using+supercritical+argon.">Extraction of petroleum hydrocarbons from soil using supercritical argon.</a> Anal. Chem. 70 (3), 616-622 (1998).</li></ol>

The authors have nothing to disclose.

Perhaps due to its relatively low critical temperature (126 K), N2 has historically been overlooked as an effective ScD solvent. In earlier reports,3,17,42,43 it has only been alluded to in the context of processing temperatures at or above ambient, where it exhibits only modest solvation power due to its low fluid density in this region of its phase diagram (except at extremely high pressures43). The key step in realizing the practical utility of N2 as a supercritical solvent ...

Supercritical fluid extraction (SFE) and drying (ScD) methods are well established in a wide range of practical applications, especially in the food and petroleum industries, but also in chemical synthesis, analysis, and materials processing.1-6 The use of drying or extraction media at conditions above their critical points is often faster, cleaner, and more efficient than traditional (liquid) techniques, and has the added advantage of being highly tunable with respect to the solvation power of the fluid by slight adjustment of the operating conditions.3,7 A simple ScD method consists of three basic steps. The first step is exposing the solid (or perhaps liquid) starting material which contains the target impurity compound to an appropriately chosen ScD fluid in its liquid (or near-liquid supercritical) phase, where its high density corresponds to a high (and perhaps selective7) solvent power with respect to the target species. The second step is heating and compressing the system above the chosen ScD fluid&#8217;s critical point in a closed container so that the fluid and its dissolved target species do not pass a phase boundary which might result in separation. The final step is slowly reducing the pressure of the ScD fluid to vacuum at a temperature above the critical temperature, allowing the fluid solution containing the target species to escape, again without encountering a phase boundary or any detrimental surface tension effects along the way.
The starting material is left depleted of the target species and may be subjected to iterated treatments if necessary. In cases of supercritical fluid extraction, the target solute species is the desired product, and is collected from solution for further use.8,9 In other cases, the dried or purified starting material is the desired product, and the extracted impurities are discarded. This latter scenario, referred to herein as the ScD approach, was discovered to be an effective strategy for the pretreatment of high surface area, microporous materials such as metal-organic frameworks (MOFs), where traditional heat-treatment methods under vacuum are in many cases not sufficient in clearing the pores of all unwanted guests, or result in pore collapse.10 Carbon dioxide ScD (CScD) processing is now a routine post-synthetic process for MOFs,11 leading to increases in nitrogen-accessible surface areas over untreated materials of up to 1,000%12 and other improvements, such as in catalytic activity.13 Other notable supercritical fluid applications are as a widely tunable medium for chemical reactions,14-16 supercritical fluid chromatography (SCFC)6,17,18 and synthesis of aerogels and advanced composite materials.19-22
For drying applications, a ScD fluid is chosen based on two criteria: a) the proximity of its critical point to ambient conditions (for convenience and to reduce energy costs or process complexity) and b) its solvation power with respect to the target species. Carbon dioxide (CO2) has proven to be a convenient ScD fluid in many applications since it is nontoxic, nonflammable, and cheap, and can be tuned to exhibit a high solvation power toward a number of common organic target species in its near-liquid state (at pressures of &#60;10 MPa and temperatures of 273-323 K).1-3,7-9 Other common supercritical solvents (or co-solvents) include water (spanning a remarkable range of solvent properties between its ambient and supercritical state23), acetone, ethylene, methanol, ethanol, and ethane, covering the spectrum from polar (protic and aprotic) to nonpolar, and having critical points relatively near to ambient conditions.
Carbon dioxide is by far the most common ScD fluid used. In established CScD methods, the reactivity of the starting material is not an inhibitive factor since CO2 is only very weakly reactive at temperatures near its critical point. However, certain classes of materials such as so-called complex hydrides (e.g., alanates and borohydrides) present unique challenges in handling due to their strong reactivity in the presence of water or CO2 in addition to their (perhaps intentionally tailored) instability under heating.24-26 Moreover, there is great international interest in such materials as high-density hydrogen storage compounds,27-30 and therefore also in nanostructured and/or porous varieties31-33. For the effective purification of such reactive, unstable, and nanostructured materials, ScD methods are a promising strategy.34 A ScD fluid must be used which has a small molecular diameter appropriate for penetration into narrow cavities and which also has a high solvation power toward the target impurities, while remaining unreactive toward the starting material itself. Herein, the use of supercritical nitrogen (N2) as an effective fluid for such extraction and especially drying applications is presented. A specific supercritical nitrogen drying (NScD) methodology is described below for the purification of &#947;-phase magnesium borohydride where the target species include both diborane and an n-butyl compound (similar to but not specifically identifiable as n-butane). The following protocol can be easily modified for general extension to other supercritical nitrogen drying or extraction processes.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Compressed Nitrogen Gas</td>
			<td>Messer Schweiz AG</td>
			<td></td>
			<td>50 L bottle, purity &#62; 99.999%, &#60;3 ppmv H2O</td>
		</tr>
		<tr>
			<td>Liquid Nitrogen</td>
			<td>Pan Gas AG</td>
			<td></td>
			<td>Bulk storage, on site</td>
		</tr>
		<tr>
			<td>Custom Supercritical Drying Apparatus</td>
			<td>Empa</td>
			<td></td>
			<td>Swagelok (compression fitting and VCR) components</td>
		</tr>
		<tr>
			<td>Custom Cryogenic Furnace Bath</td>
			<td>Empa</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Custom Labview Interface</td>
			<td>Empa</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

supercritical nitrogen processing for the purification of reactive porous materials

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. Herein, nitrogen is presented as a novel supercritical drying fluid for specialized applications such as in the processing of reactive porous materials, where carbon dioxide and other fluids are not appropriate due to their higher chemical reactivity. Nitrogen exhibits similar physical properties in the near-critical region of its phase diagram as compared to carbon dioxide: a widely tunable density up to ~1 g ml-1, modest critical pressure (3.4 MPa), and small molecular diameter of ~3.6 &#197;. The key to achieving a high solvation power of nitrogen is to apply a processing temperature in the range of 80-150 K, where the density of nitrogen is an order of magnitude higher than at similar pressures near ambient temperature. The detailed solvation properties of nitrogen, and especially its selectivity, across a wide range of common target species of extraction still require further investigation. Herein we describe a protocol for the supercritical nitrogen processing of porous magnesium borohydride.

Alkali and alkaline earth metal borohydrides are potential hydrogen storage materials, which deliver a large content of gaseous hydrogen upon decomposition.27,29 Other decomposition products such as diborane have also sometimes been detected in the gas desorbed, but their origin is not a priori clear; it is possible they are products of the pure phase decomposition, but may also be impurities or products of reactions of impurities leftover from chemical synthesis.35 The porous phase of magnesium bor...

Watch this Scientific Journal Video about Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials at JoVE.com

Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials

Nitrogen is an effective supercritical fluid for extraction or drying processes due to its small molecular size, high density in the near-liquid supercritical regime, and chemical inertness. We present a supercritical nitrogen drying protocol for the purification treatment of reactive, porous materials.

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. ...

supercritical-nitrogen-processing-for-purification-reactive-porous

Research

JoVE Journal

Chemistry

14.6K vistas.  Empa, Swiss Federal Laboratories for Materials Science and Technology.  El nitrógeno es un fluido supercrítico eficaz para procesos de extracción o de secado debido a su pequeño tamaño molecular, de alta densidad en el régimen supercrítico-cerca de líquido, e inercia química. Se presenta un protocolo de secado de nitrógeno supercrítico para el tratamiento de purificación de materiales reactivos, porosos. 

Video: Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials

Folding and Characterization of a Bio-responsive Robot from DNA Origami

The DNA nanorobot is a hollow hexagonal nanometric device, designed to open in response to specific stimuli and present cargo sequestered inside. Both stimuli and cargo can be tailored according to specific needs. Here we describe the DNA nanorobot fabrication protocol, with the use of the DNA origami technique. The procedure initiates by mixing short single-strand DNA staples into a stock mixture which is then added to a long, circular, single-strand DNA scaffold in presence of a folding buffer. A standard thermo cycler is programmed to gradually lower the mixing reaction temperature to facilitate the staples-to-scaffold annealing, which is the guiding force behind the folding of the nanorobot. Once the 60 hr folding reaction is complete, excess staples are discarded using a centrifugal filter, followed by visualization via agarose-gel electrophoresis (AGE). Finally, successful fabrication of the nanorobot is verified by transmission electron microscopy (TEM), with the use of uranyl-formate as negative stain.

DNA origami is a powerful method for fabricating precise nanoscale objects by programming the self-assembly of DNA molecules. Here we describe a protocol for the folding of a bio-responsive robot from DNA origami, its purification and negative staining for transmission electron microscopic imaging (TEM).

The DNA nanorobot is a hollow hexagonal nanometric device, designed to open in response to specific stimuli and present cargo sequestered inside. Both ...

Preparation of Highly Porous Coordination Polymer Coatings on Macroporous Polymer Monoliths for Enhanced Enrichment of Phosphopeptides

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous polymer monoliths. The developed approach is based on the preparation of a macroporous polymer containing carboxylic acid functional groups and the subsequent step-by-step solution-based controlled growth of a layer of a porous coordination polymer on the surface of the pores of the polymer monolith. The prepared metal-organic polymer hybrid has a high specific micropore surface area. The amount of iron(III) sites is enhanced through metal-organic coordination on the surface of the pores of the functional polymer support. The increase of metal sites is related to the number of iterations of the coating process.
The developed preparation scheme is easily adapted to a capillary column format. The functional porous polymer is prepared as a self-contained single-block porous monolith within the capillary, yielding a flow-through separation device with excellent flow permeability and modest back-pressure. The metal-organic polymer hybrid column showed excellent performance for the enrichment of phosphopeptides from digested proteins and their subsequent detection using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The presented experimental protocol is highly versatile, and can be easily implemented to different organic polymer supports and coatings with a plethora of porous coordination polymers and metal-organic frameworks for multiple purification and/or separation applications.

A procedure for the preparation of porous hybrid separation media composed of a macroporous polymer monolith internally coated by a high surface area microporous coordination polymer is presented.

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous ...

On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes

The shift to heavy crude oils and the use of alternative fossil resources such as shale oil are a challenge for the petrochemical industry. The composition of heavy crude oils and shale oils varies substantially depending on the origin of the mixture. In particular they contain an increased amount of nitrogen containing compounds compared to the conventionally used sweet crude oils. As nitrogen compounds have an influence on the operation of thermal processes occurring in coker units and steam crackers, and as some species are considered as environmentally hazardous, a detailed analysis of the reactions involving nitrogen containing compounds under pyrolysis conditions provides valuable information. Therefore a novel method has been developed and validated with a feedstock containing a high nitrogen content, i.e., a shale oil. First, the feed was characterized offline by comprehensive two-dimensional gas chromatography (GC &#215; GC) coupled with a nitrogen chemiluminescence detector (NCD). In a second step the on-line analysis method was developed and tested on a steam cracking pilot plant by feeding pyridine dissolved in heptane. The former being a representative compound for one of the most abundant classes of compounds present in shale oil. The composition of the reactor effluent was determined via an in-house developed automated sampling system followed by immediate injection of the sample on a GC &#215; GC coupled with a time-of-flight mass spectrometer (TOF-MS), flame ionization detector (FID) and NCD. A novel method for quantitative analysis of nitrogen containing compounds using NCD and 2-chloropyridine as an internal standard has been developed and demonstrated.

A method combining comprehensive two-dimensional gas chromatography with nitrogen chemiluminescence detection has been developed and applied to on-line analysis of nitrogen containing compounds in a complex hydrocarbon matrix.

The shift to heavy crude oils and the use of alternative fossil resources such as shale oil are a challenge for the petrochemical industry. The ...

Insights into the Interactions of Amino Acids and Peptides with Inorganic Materials Using Single-Molecule Force Spectroscopy

The interactions between proteins or peptides and inorganic materials lead to several interesting processes. For example, combining proteins with minerals leads to the formation of composite materials with unique properties. In addition, the undesirable process of biofouling is initiated by the adsorption of biomolecules, mainly proteins, on surfaces. This organic layer is an adhesion layer for bacteria and allows them to interact with the surface. Understanding the fundamental forces that govern the interactions at the organic-inorganic interface is therefore important for many areas of research and could lead to the design of new materials for optical, mechanical and biomedical applications. This paper demonstrates a single-molecule force spectroscopy technique that utilizes an AFM to measure the adhesion force between either peptides or amino acids and well-defined inorganic surfaces. This technique involves a protocol for attaching the biomolecule to the AFM tip through a covalent flexible linker and single-molecule force spectroscopy measurements by atomic force microscope. In addition, an analysis of these measurements is included.

Here we present a protocol to measure the force of interactions between a well-defined inorganic surface and either peptides or amino acids by single-molecule force spectroscopy measurements using an atomic force microscope (AFM). The information obtained from the measurement is important to better understand the peptide-inorganic material interphase.

The interactions between proteins or peptides and inorganic materials lead to several interesting processes. For example, combining proteins with minerals ...

Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be covalently and site-specifically linked via their end facets, resulting in polymer-like linear or branched chains. The linking procedure begins with a cation-exchange process in which the end facets of the cadmium chalcogenide NCs are first converted to silver chalcogenide. This is followed by the selective removal of ligands at their surface. This results in cadmium chalcogenide NCs with highly reactive silver chalcogenide end facets that spontaneously fuse upon contact with each other, thereby establishing an interparticle facet-to-facet attachment. Through the judicious choice of precursor concentrations, an extensive network of linked NCs can be produced. Structural characterization of the linked NCs is carried out via low- and high-resolution transmission electron microscopy (TEM), as well as energy-dispersive X-ray spectroscopy, which confirm the presence of silver chalcogenide domains between chains of cadmium chalcogenide NCs.

A protocol detailing how shape-anisotropic colloidal cadmium chalcogenide nanocrystals can be covalently linked via their end facets is presented here.

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be ...

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three preparation methods are described: (a) the incorporation of metal salts into silica or alumina wet gels using an impregnation method; (b) the incorporation of metal salts into alumina wet gels using a co-precursor method; and (c) the addition of metal nanoparticles directly into a silica aerogel precursor mixture. The methods utilize a hydraulic hot press, which allows for rapid (&#60;6 h) supercritical extraction and results in aerogels of low density (0.10 g/mL) and high surface area (200-800 m2/g). While the work presented here focuses on the use of copper salts and copper nanoparticles, the approach can be implemented using other metal salts and nanoparticles. A protocol for testing the three-way catalytic ability of these aerogels for automotive pollution mitigation is also presented. This technique uses custom-built equipment, the Union Catalytic Testbed (UCAT), in which a simulated exhaust mixture is passed over an aerogel sample at a controlled temperature and flow rate. The system is capable of measuring the ability of the catalytic aerogels, under both oxidizing and reducing conditions, to convert CO, NO and unburned hydrocarbons (HCs) to less harmful species (CO2, H2O and N2). Example catalytic results are presented for the aerogels described.

Here we present protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms. Methods for preparing materials using copper salts and copper-containing nanoparticles are featured. Catalytic testing protocols demonstrate the effectiveness of these aerogels for three-way catalysis applications.

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three ...

Deposition of Porous Sorbents on Fabric Supports

A microwave deposition technique for silanes, previously described for production of oleophobic fabrics, is adapted to provide a fabric support material that can be subsequently treated by dip coating. Dip coating with a sol preparation provides a supported porous layer on the fabric. In this case, the porous layer is a porphyrin functionalized sorbent system based on a powdered material that has been demonstrated previously for the capture and conversion of phosgene. A representative coating is applied to cotton fabric at a loading level of 10 mg/g. This coating has minimal impact on water vapor transport through the fabric (93% of the support fabric rate) while significantly reducing transport of 2-chloroethyl ethyl sulfide (CEES) through the material (7% of support fabric rate). The described approaches are suitable for use with other fabrics providing amine and hydroxyl groups for modification and can be used in combination with other sol preparations to produce varying functionality.

This report details a microwave-initiated approach for deposition of porphyrin functionalized porous organosilicate sorbents on a cotton fabric and demonstrates reduction in 2-chloroethyl ethyl sulfide (CEES) transport through the fabric resulting from this treatment.

A microwave deposition technique for silanes, previously described for production of oleophobic fabrics, is adapted to provide a fabric support material ...

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 &#176;C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications.
In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

Here, we present a protocol for the synthesis of porous barium titanate (BaTiO3) thin film by a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles are used as an organic template.

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its ...

Synthesis and Bioconjugation of Thiol-Reactive Reagents for the Creation of Site-Selectively Modified Immunoconjugates

Maleimide-bearing bifunctional probes have been employed for decades for the site-selective modification of thiols in biomolecules, especially antibodies. Yet maleimide-based conjugates display limited stability in vivo because the succinimidyl thioether linkage can undergo a retro-Michael reaction. This, of course, can lead to the release of the radioactive payload or its exchange with thiol-bearing biomolecules in circulation. Both of these processes can produce elevated activity concentrations in healthy organs as well as decreased activity concentrations in target tissues, resulting in reduced imaging contrast and lower therapeutic ratios. In 2018, we reported the creation of a modular, stable, and easily accessible phenyloxadiazolyl methyl sulfone reagent &#8212; dubbed &#8216;PODS&#8217; &#8212; as a platform for thiol-based bioconjugations. We have clearly demonstrated that PODS-based site-selective bioconjugations reproducibly and robustly create homogenous, well-defined, highly immunoreactive, and highly stable radioimmunoconjugates. Furthermore, preclinical experiments in murine models of colorectal cancer have shown that these site-selectively labeled radioimmunoconjugates exhibit far superior in vivo performance compared to radiolabeled antibodies synthesized via maleimide-based conjugations. In this protocol, we will describe the four-step synthesis of PODS, the creation of a bifunctional PODS-bearing variant of the ubiquitous chelator DOTA (PODS-DOTA), and the conjugation of PODS-DOTA to the HER2-targeting antibody trastuzumab.

In this protocol, we will describe the synthesis of PODS, a phenyoxadiazolyl methyl sulfone-based reagent for the site-selective attachment of cargos to the thiols of biomolecules, particularly antibodies. In addition, we will describe the synthesis and characterization of a PODS-bearing bifunctional chelator and its conjugation to a model antibody.

Maleimide-bearing bifunctional probes have been employed for decades for the site-selective modification of thiols in biomolecules, especially antibodies. ...

Evaluation of Oxidative Stress in Biological Samples Using the Thiobarbituric Acid Reactive Substances Assay

Despite its limited analytical specificity and ruggedness, the thiobarbituric acid reactive substances (TBARS) assay has been widely used as a generic metric of lipid peroxidation in biological fluids. It is often considered a good indicator of the levels of oxidative stress within a biological sample, provided that the sample has been properly handled and stored. The assay involves the reaction of lipid peroxidation products, primarily malondialdehyde (MDA), with thiobarbituric acid (TBA), which leads to the formation of MDA-TBA2 adducts called TBARS. TBARS yields a red-pink color that can be measured spectrophotometrically at 532 nm. The TBARS assay is performed under acidic conditions (pH = 4) and at 95 &#176;C. Pure MDA is unstable, but these conditions allow the release of MDA from MDA bis(dimethyl acetal), which is used as the analytical standard in this method. The TBARS assay is a straightforward method that can be completed in about 2 h. Preparation of assay reagents are described in detail here. Budget-conscious researchers can use these reagents for multiple experiments at a low cost rather than buying an expensive TBARS assay kit that only permits construction of a single standard curve (and thus can only be used for one experiment). The applicability of this TBARS assay is shown in human serum, low density lipoproteins, and cell lysates. The assay is consistent and reproducible, and limits of detection of 1.1 &#956;M can be reached. Recommendations for the use and interpretation of the spectrophotometric TBARS assay are provided.

The goal of the thiobarbituric acid reactive substances assay is to assess oxidative stress in biological samples by measuring the production of lipid peroxidation products, primarily malondialdehyde, using visible wavelength spectrophotometry at 532 nm. The method described here can be applied to human serum, cell lysates, and low density lipoproteins.

Despite its limited analytical specificity and ruggedness, the thiobarbituric acid reactive substances (TBARS) assay has been widely used as a generic ...