Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund for partial support of this research. We are grateful to the National Science Foundation (CHE-0619275 and CHE-0963165) for renovation and instrumentation grants that supported this research.

1. Standard Protocol for The Separation of Aromatic Aldehydes from a Mixture. Example: Separation of Benzyl Butyrate from a 1:1 Mixture with Anisaldehyde.
<ol>
	<li>Dissolve 175 &#956;L of anisaldehyde and 250 &#956;L of benzyl butyrate in 5 mL of methanol and transfer the solution to a separatory funnel. 
	Caution: Sodium bisulfite can generate sulfur dioxide gas, thus this protocol should be carried out with proper ventilation, such as in a fume hood.</li>
	<li>Add 1 mL of saturated aqueous sodium bisulfite and shake vigorously for approximately 30 s.</li>
	<li>Add 25 mL of deionized water and 25 mL of 10% ethyl acetate/hexanes and shake vigorously.</li>
	<li>Separate the layers. Dry the organic layer with anhydrous magnesium sulfate. Filter the solution to remove magnesium sulfate and concentrate in vacuo using a rotary evaporator.</li>
</ol>
2. Separation of Aliphatic Aldehydes and Ketones from a&#160;Mixture. Example: Separation of Benzyl Butyrate from a&#160;1:1 Mixture with Benzylacetone.
<ol>
	<li>Dissolve 213 &#956;L of benzylacetone and 250 &#956;L of benzyl butyrate in 10 mL of dimethylformamide and transfer the solution to a separatory funnel. 
	Caution: Sodium bisulfite can generate sulfur dioxide gas, thus this protocol should be carried out with proper ventilation, such as in a fume hood.</li>
	<li>Add 25 mL of saturated aqueous sodium bisulfite and shake vigorously for approximately 30 s.</li>
	<li>Add 25 mL of deionized water and 25 mL of 10% ethyl acetate/hexanes and shake vigorously.</li>
	<li>Separate the layers. Return the aqueous layer to the separatory funnel, add 25 mL of 10% ethyl acetate/hexanes and shake vigorously. Drain the aqueous layer, leaving the organic layer in the separatory funnel. Add the previous organic layer back to the separatory funnel.</li>
	<li>Wash the combined organic layers three times with deionized water (10 mL for each wash). Dry the organic layer with anhydrous magnesium sulfate. Filter the solution to remove magnesium sulfate and concentrate in vacuo using a rotary evaporator.</li>
</ol>
3. Separation of Aldehydes from a&#160;Mixture Containing an Alkene. Example: Separation of Benzyl Butyrate from a 1:1 Mixture with Citronellal.
<ol>
	<li>Dissolve 255 &#956;L of citronellal and 250 &#956;L of benzyl butyrate in 10 mL of dimethylformamide and transfer the solution to a separatory funnel. 
	Caution: Sodium bisulfite can generate sulfur dioxide gas, thus this protocol should be carried out with proper ventilation, such as in a fume hood.</li>
	<li>Add 25 mL of saturated aqueous sodium bisulfite and shake vigorously for approximately 30 s.</li>
	<li>Add 25 mL of deionized water and 25 mL of hexanes and shake vigorously.</li>
	<li>Separate the layers. Return the aqueous layer to the separatory funnel, add 25 mL hexanes and shake vigorously. Drain the aqueous layer, leaving the organic layer in the separatory funnel. Add the previous organic layer back to the separatory funnel.</li>
	<li>Wash the combined organic layers three times with deionized water (10 mL for each wash). Dry the organic layer with anhydrous magnesium sulfate. Filter the solution to remove magnesium sulfate and concentrate in vacuo using a rotary evaporator.</li>
</ol>
4. Re-isolation of Aldehydes from a Mixture. Example: Separation of Piperonal from a 1:1 Mixture with Benzyl Butyrate.
<ol>
	<li>Dissolve 217 mg of piperonal and 250 &#956;L of benzyl butyrate in 5 mL of methanol and transfer the solution to a separatory funnel. 
	Caution: Sodium bisulfite can generate sulfur dioxide gas, thus, this protocol should be carried out with proper ventilation, such as in a fume hood.</li>
	<li>Add 1 mL of saturated aqueous sodium bisulfite and shake vigorously for approximately 30 s.</li>
	<li>Add 25 mL of deionized water and 25 mL of 10% ethyl acetate/hexanes and shake vigorously.</li>
	<li>Separate the layers. Return the aqueous layer back to the separatory funnel.
	<ol>
		<li>Optional: Wash aqueous layer once with 25 mL of 10% ethyl acetate/hexanes to remove the small amount of remaining benzyl butyrate.</li>
	</ol>
	</li>
	<li>Add 25 mL of ethyl acetate and then add 50% sodium hydroxide until a pH strip indicates that the pH is 12. Shake vigorously. 
	Caution: Gas evolution has been observed during this step and can cause pressure build-up. Make sure to properly vent the separatory funnel. Scaling up this procedure will make gas evolution more pronounced. Use caution.</li>
	<li>Separate the layers. Return the aqueous layer to the separatory funnel and add 25 mL of ethyl acetate. Shake vigorously.</li>
	<li>Separate the layers. Combine the organic layer with the organic layer from the previous step. Dry the combined organic layer with anhydrous magnesium sulfate. Filter the solution to remove magnesium sulfate and concentrate in vacuo using a rotary evaporator.</li>
</ol>

<ol>
	<li>Boucher, M. M., Furigay, M. H., Quach, P. K., Brindle, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liquid-Liquid+Extraction+Protocol+for+the+Removal+of+Aldehydes+and+Highly+Reactive+Ketones+from+Mixtures.">Liquid-Liquid Extraction Protocol for the Removal of Aldehydes and Highly Reactive Ketones from Mixtures.</a> Org. Process Res. Dev. 21 (9), 1394-1403 (2017).</li><li>Lauer, G. G., Pratt, R. S., Wilson, W. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+Aldehydes+and+Ketones.">Separation of Aldehydes and Ketones.</a> , (1951).</li><li>Hsu, W. 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> Separation of Aldehydes from Ketones via Acid-Catalyzed Cyclotrimerization of the Aldehyde. , 4701561 (1987).</li><li>Schreiber, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Process+for+Separating+Aldehydes+and+Ketones.">Process for Separating Aldehydes and Ketones.</a> , (1942).</li><li>Bludworth, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+Aldehyde-Ketone+Mixtures.">Separation of Aldehyde-Ketone Mixtures.</a> , (1944).</li><li>Masilamani, D., Manahan, E. H., Vitrone, J., Rogic, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organic+Reactions+of+Sulfur+Dioxide.+Reactions+with+Nucleophilic+Double+Bonds+Leading+to+the+Isomerization,+Aromatization,+Selective+Hydrogen-Deuterium+Exchange,+and+Electron-Transfer+Proceses.">Organic Reactions of Sulfur Dioxide. Reactions with Nucleophilic Double Bonds Leading to the Isomerization, Aromatization, Selective Hydrogen-Deuterium Exchange, and Electron-Transfer Proceses.</a> J. Org. Chem. 48 (25), 4918-4931 (1983).</li><li>Masilamani, D., Rogic, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organic+Reactions+of+Sulfur+Dioxide.+4.+A+Facile+Regiospecific+Hydrogen-Deuterium+Exchange+in+Olefins.+Consequence+of+the+Intermediacy+of+Allylic+Sulfinic+Acids+in+the+Ene+Reaction+of+Sulfur+Dioxide+with+Double+Bonds.">Organic Reactions of Sulfur Dioxide. 4. A Facile Regiospecific Hydrogen-Deuterium Exchange in Olefins. Consequence of the Intermediacy of Allylic Sulfinic Acids in the Ene Reaction of Sulfur Dioxide with Double Bonds.</a> J. Am. Chem. Soc. 100 (14), 4634-4635 (1978).</li><li>Makitra, R. G., Kal'muk, S. D., Bryk, D. V., Polyuzhin, I. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+Controlling+Sulfur+Dioxide+Solubilities+in+Organic+Solvents.">Factors Controlling Sulfur Dioxide Solubilities in Organic Solvents.</a> Russ. J. Inorg. Chem. 55 (8), 1322-1329 (2010).</li><li>van Dam, M. H. H., Lamine, A. S., Roizard, D., Lochon, P., Roizard, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+Sulfur+Dioxide+Removal+Using+Organic+Solvents.">Selective Sulfur Dioxide Removal Using Organic Solvents.</a> Ind. Eng. Chem. Res. 36 (11), 4628-4637 (1997).</li><li>Li, H., Jiao, X., Chen, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solubility+of+Sulphur+Dioxide+in+Polar+Organic+Solvents.">Solubility of Sulphur Dioxide in Polar Organic Solvents.</a> Phys. Chem. Liq. 52 (2), 349-353 (2014).</li><li>Trost, B. M., Brindle, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Direct+Catalytic+Asymmetric+Aldol+Reaction.">The Direct Catalytic Asymmetric Aldol Reaction.</a> Chem. Soc. Rev. 39 (5), 1600 (2010).</li></ol>

The authors have nothing to disclose.

Initial attempts to use the bisulfite reaction as a method to remove aldehydes using a typical two-phase extraction led to very low levels of removal. We hypothesized that the reaction was not fast enough to occur during the very limited time that the two layers were in contact. To increase the contact between the reactants, we developed a two-stage extraction protocol in which a water-miscible solvent is used initially to allow sufficient mixing of the reactants prior to the introduction of an immiscible solvent. The in...

The separation of components of mixtures from one another is essential to the preparation of pure materials. The method described herein allows for the facile separation of aldehydes and sterically unhindered cyclic and methyl ketones from other organic molecules1. The technique relies on the reactivity of bisulfite with the carbonyl group to create a charged adduct that can be separated into an aqueous layer, while other components separate into an immiscible organic layer. The key to achieving reactivity between bisulfite and the carbonyl is the use of a miscible solvent, which allows the reaction to take place prior to the separation into separate phases. Without the addition of the miscible solvent minimal separation is obtained, presumably due to poor contact between the hydrophilic bisulfite and the hydrophobic organics.
The advantage of this separation method for purification is the ease of the protocol. Liquid-liquid extraction is a simple operation to perform, and can be carried out on large scale. Alternative purification techniques, such as column chromatography, are much more expensive, time-consuming, and challenging to perform on large scale and require sufficient differentiation of the components in terms of polarity. Purifying by recrystallization or distillation requires sufficient differentiation between the solubility or boiling points of the components of the mixture, respectively. Because bisulfite extraction relies on the difference in reactivity of the carbonyl group of aldehydes and ketones, compounds with similar solubility, boiling points, or polarities can be effectively separated. Other chemical separation methods exist for the selective separation of aldehydes and ketones from mixtures, for example, the selective formation of oximes2, cyclic acetals3, or mercaptal4 formation. These methods require an additional step to separate the formed species from the mixture, because the product is not water soluble and therefore cannot be separated by a simple extraction protocol. Aldehyde oxidation to form removable carboxylic acids is another reported technique5, but the required oxidation step is less chemoselective than the mild bisulfite conditions described herein, and requires the use of oxygen gas and a cobalt catalyst.
This method is applicable to the separation of aldehydes (Figure 1) and sterically-unhindered cyclic and methyl ketones (Figure 2) from molecules that do not contain these functional groups. Particularly reactive ketones, such as &#945;-keto esters are also removed using this process. Alkanes, alkenes, dienes, alkynes, esters, amides, carboxylic acids, alkyl halides, alcohols, phenols, nitriles, benzyl chlorides, epoxides, anilines, acetals, and slightly hindered, &#945;,&#946;-unsaturated, or aryl ketones are all unreactive under the conditions and can be separated from the aldehyde or reactive ketone component of the mixture (Figures 2 and Figure 3). Ethyl ketones or &#945;-substituted cyclic ketones, for example, are sufficiently hindered and are therefore separable from aldehydes and more reactive ketones. When using alkenes, hexane is recommended as the immiscible solvent to prevent unwanted decomposition due to sulfur dioxide present in the bisulfite solution. The functional group compatibility of the bisulfite extraction protocol is extremely broad, and is therefore applicable to an extremely wide range of separations, if the carbonyl contaminant to be separated from the mixture is either an aldehyde or an unhindered methyl or cyclic ketone. Less reactive ketones do not react with bisulfite under these conditions and are therefore not removed.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>sodium bisulfite</td>
			<td>Fisher</td>
			<td>AC419440010&#160;</td>
			<td>1 kg</td>
		</tr>
		<tr>
			<td>benzyl butyrate</td>
			<td>Fisher</td>
			<td>AAB2424130&#160;</td>
			<td>250 g</td>
		</tr>
		<tr>
			<td>anisaldehyde</td>
			<td>Fisher</td>
			<td>AC104801000&#160;</td>
			<td>100 mL</td>
		</tr>
		<tr>
			<td>magnesium sulfate</td>
			<td>Fisher</td>
			<td>M65-500&#160;</td>
			<td>500 g</td>
		</tr>
		<tr>
			<td>ethyl acetate</td>
			<td>Fisher</td>
			<td>E195-4&#160;</td>
			<td>4 L</td>
		</tr>
		<tr>
			<td>hexanes</td>
			<td>Fisher</td>
			<td>H292-4&#160;</td>
			<td>4 L</td>
		</tr>
		<tr>
			<td>methanol&#160;</td>
			<td>Fisher</td>
			<td>A456-1&#160;</td>
			<td>1 L</td>
		</tr>
		<tr>
			<td>dimethylformamide</td>
			<td>Fisher</td>
			<td>D119-1&#160;</td>
			<td>1 L</td>
		</tr>
		<tr>
			<td>citronellal</td>
			<td>Fisher</td>
			<td>AAL15753AE&#160;</td>
			<td>100 mL</td>
		</tr>
		<tr>
			<td>benzylacetone&#160;</td>
			<td>Fisher</td>
			<td>AC105832500&#160;</td>
			<td>250 mL</td>
		</tr>
		<tr>
			<td>deionized water</td>
			<td>Fisher</td>
			<td>BP28194&#160;</td>
			<td>4 L</td>
		</tr>
		<tr>
			<td>piperonal&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>P49104-25G</td>
			<td>25 G</td>
		</tr>
		<tr>
			<td>sodium hydroxide</td>
			<td>Fisher</td>
			<td>S318-1&#160;</td>
			<td>1 kg</td>
		</tr>
		<tr>
			<td>separatory funnel with cap</td>
			<td>Fisher</td>
			<td>10-437-5B&#160;</td>
			<td>125 mL</td>
		</tr>
		<tr>
			<td>ring stand</td>
			<td>Fisher</td>
			<td>03-422-215</td>
			<td>3 aluminum rods</td>
		</tr>
		<tr>
			<td>ring clamp</td>
			<td>Fisher</td>
			<td>12-000-104&#160;</td>
			<td>5 cm</td>
		</tr>
		<tr>
			<td>cork ring</td>
			<td>Fisher</td>
			<td>07-835AA&#160;</td>
			<td>8 cm outer dimension</td>
		</tr>
		<tr>
			<td>round bottom flask</td>
			<td>Fisher</td>
			<td>31-501-107&#160;</td>
			<td>100 mL</td>
		</tr>
		<tr>
			<td>rotary evaporator with accessories</td>
			<td>Fisher</td>
			<td>05-000-461&#160;</td>
			<td>cold trap bondenser</td>
		</tr>
		<tr>
			<td>bump trap 14/20 joint</td>
			<td>Fisher</td>
			<td>CG132201</td>
			<td>14/20 joint</td>
		</tr>
		<tr>
			<td>funnel</td>
			<td>Fisher</td>
			<td>05-555-6&#160;</td>
			<td>organic solvent compatible</td>
		</tr>
		<tr>
			<td>cotton</td>
			<td>Fisher</td>
			<td>22-456-881</td>
			<td>non-sterile</td>
		</tr>
		<tr>
			<td>glass pipets</td>
			<td>Fisher</td>
			<td>13-678-20A&#160;</td>
			<td>borosilicate 5.75&#34;</td>
		</tr>
		<tr>
			<td>two 250 microliter syringes</td>
			<td>Fisher</td>
			<td>14-813-69&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>4 erlenmeyer flasks</td>
			<td>Fisher</td>
			<td>10-040D&#160;</td>
			<td>125 mL</td>
		</tr>
		<tr>
			<td>fume hood&#160;</td>
			<td>Fisher</td>
			<td>13-118-370&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>nitrile gloves</td>
			<td>Fisher</td>
			<td>19-149-863B&#160;</td>
			<td>medium</td>
		</tr>
		<tr>
			<td>safety goggles</td>
			<td>Fisher</td>
			<td>17-377-403&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>spatula</td>
			<td>Fisher</td>
			<td>14-357Q</td>
			<td></td>
		</tr>
		<tr>
			<td>balance</td>
			<td>Fisher</td>
			<td>01-912-403&#160;</td>
			<td>120 g capacity</td>
		</tr>
	</tbody>
</table>

separation of aldehydes and reactive ketones from mixtures using a bisulfite extraction protocol

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer by generating a charged structure provides an opportunity to use extraction as a simple purification technique. By combining the use of a miscible organic solvent with saturated sodium bisulfite, aldehydes and reactive ketones can be successfully transformed into charged bisulfite adducts that can then be separated from other organic components of a mixture by the introduction of an immiscible organic layer. Here, we describe a simple protocol for the removal of aldehydes, including sterically-hindered neopentyl aldehydes and some ketones, from chemical mixtures. Ketones can be separated if they are sterically unhindered cyclic or methyl ketones. For aliphatic aldehydes and ketones, dimethylformamide is used as the miscible solvent to improve removal rates. The bisulfite addition reaction can be reversed by basification of the aqueous layer, allowing for the re-isolation of the reactive carbonyl component of a mixture.

Procedure 1 for aldehyde removal is used for aromatic aldehydes. Procedure 2, in which dimethylformamide is used as the miscible solvent, should be used for aliphatic aldehydes and ketones. Procedure 2 should also be used for mixtures that are not fully soluble in methanol. The material obtained from each of the protocols is analyzed for purity using 1H NMR integration analysis and for recovery rate by mass. Typical purities an...

Watch this Scientific Journal Video about Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol at JoVE.com

Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol

Here, we present a protocol to remove aldehydes and reactive ketones from mixtures by a liquid-liquid extraction protocol directly with saturated sodium bisulfite in a miscible solvent. This combined protocol is rapid and facile to perform. The aldehyde or ketone can be re-isolated by the basification of the aqueous layer.

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer ...

separation-aldehydes-reactive-ketones-from-mixtures-using-bisulfite

Research

Education

JoVE Journal

JoVE Core

Chemistry

Introduction: Matter and Measurement

SCIENTISTS IN ACTION

33.7K Views.  Trinity College. Here, we present a protocol to remove aldehydes and reactive ketones from mixtures by a liquid-liquid extraction protocol directly with saturated sodium bisulfite in a miscible solvent. This combined protocol is rapid and facile to perform. The aldehyde or ketone can be re-isolated by the basification of the aqueous layer.

Video: Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol

A Simple and Rapid Protocol for Measuring Neutral Lipids in Algal Cells Using Fluorescence

Algae are considered excellent candidates for renewable fuel sources due to their natural lipid storage capabilities. Robust monitoring of algal fermentation processes and screening for new oil-rich strains requires a fast and reliable protocol for determination of intracellular lipid content. Current practices rely largely on gravimetric methods to determine oil content, techniques developed decades ago that are time consuming and require large sample volumes. In this paper, Nile Red, a fluorescent dye that has been used to identify the presence of lipid bodies in numerous types of organisms, is incorporated into a simple, fast, and reliable protocol for measuring the neutral lipid content of Auxenochlorella protothecoides, a green alga. The method uses ethanol, a relatively mild solvent, to permeabilize the cell membrane before staining and a 96 well micro-plate to increase sample capacity during fluorescence intensity measurements. It has been designed with the specific application of monitoring bioprocess performance. Previously dried samples or live samples from a growing culture can be used in the assay.

A simple protocol to determine the neutral lipid content of algal cells using a Nile Red staining procedure is described. This time-saving technique offers an alternative to traditional gravimetric-based lipid quantification protocols. It has been designed for the specific application of monitoring bioprocess performance.

Algae are considered excellent candidates for renewable fuel sources due to their natural lipid storage capabilities. Robust monitoring of algal ...

Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures

The behavior of confined colloidal suspensions with attractive interparticle interactions is critical to the rational design of materials for directed assembly1-3, drug delivery4, improved hydrocarbon recovery5-7, and flowable electrodes for energy storage8. Suspensions containing fluorescent colloids and non-adsorbing polymers are appealing model systems, as the ratio of the polymer radius of gyration to the particle radius&#160;and concentration of polymer control the range and strength of the interparticle attraction, respectively. By tuning the polymer properties and the volume fraction of the colloids, colloid fluids, fluids of clusters, gels, crystals, and glasses can be obtained9.&#160;Confocal microscopy, a variant of fluorescence microscopy, allows an optically transparent and fluorescent sample to be imaged with high spatial and temporal resolution in three dimensions. In this technique, a small pinhole or slit blocks the emitted fluorescent light from regions of the sample that are outside the focal volume of the microscope optical system. As a result, only a thin section of the sample in the focal plane is imaged. This technique is particularly well suited to probe the structure and dynamics in dense colloidal suspensions at the single-particle scale: the particles are large enough to be resolved using visible light and diffuse slowly enough to be captured at typical scan speeds of commercial confocal systems10. Improvements in scan speeds and analysis algorithms have also enabled quantitative confocal imaging of flowing suspensions11-16,37.&#160;In this paper, we demonstrate confocal microscopy experiments to probe the confined phase behavior and flow properties of colloid-polymer mixtures. We first prepare colloid-polymer mixtures that are density- and refractive-index matched. Next, we report a standard protocol for imaging quiescent dense colloid-polymer mixtures under varying confinement in thin wedge-shaped cells. Finally, we demonstrate a protocol for imaging colloid-polymer mixtures during microchannel flow.

Confocal microscopy is used to image quiescent and flowing colloid-polymer mixtures, which are studied as model systems for attractive suspensions. Image analysis algorithms are used to calculate structural and dynamic metrics for the colloidal particles that measure changes due to geometric confinement.

The behavior of confined colloidal suspensions with attractive interparticle interactions is critical to the rational design of materials for directed ...

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.

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. ...

Preparation of Biopolymer Aerogels Using Green Solvents

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers (gelatin, agar, cellulose), only recently have biomasses been recognized as an abundant source of chemically diverse macromolecules for functional aerogel materials. Biopolymer aerogels (pectin, alginate, chitosan, cellulose, etc.) exhibit both specific inheritable functions of starting biopolymers and distinctive features of aerogels (80-99% porosity and specific surface up to 800 m2/g). This synergy of properties makes biopolymer aerogels promising candidates for a wide gamut of applications such as thermal insulation, tissue engineering and regenerative medicine, drug delivery systems, functional foods, catalysts, adsorbents and sensors. This work demonstrates the use of pressurized carbon dioxide (5 MPa) for the ionic cross linking of amidated pectin into hydrogels. Initially a biopolymer/salt dispersion is prepared in water. Under pressurized CO2 conditions, the pH of the biopolymer solution is lowered to 3 which releases the crosslinking cations from the salt to bind with the biopolymer yielding hydrogels. Solvent exchange to ethanol and further supercritical CO2 drying (10 - 12 MPa) yield aerogels. Obtained aerogels are ultra-porous with low density (as low as 0.02 g/cm3), high specific surface area (350 - 500 m2/g) and pore volume (3 - 7 cm3/g for pore sizes less than 150 nm).

A new way for the production of biopolymer-based aerogels by carbon dioxide (CO2) induced gelation is shown. The technique utilizes pressurized carbon dioxide (5 MPa) for the production of biopolymer hydrogels and supercritical CO2 (12 MPa) to convert gels into aerogels. The only solvents needed besides CO2 are water and ethanol.

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers ...

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), is demonstrated. The ligand is synthesized as the chloride salt (BBIG-Cl) by in situ imine condensation of terephthalaldehyde with aminoguanidinium chloride in water, followed by crystallization as the sulfate salt (BBIG-SO4). Alternatively, BBIG-Cl is synthesized ex situ in larger scale from ethanol. The sulfate separation ability of the BBIG ligand is demonstrated by selective and quantitative crystallization of sulfate from seawater. The ligand can be recycled by neutralization of BBIG-SO4 with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into BBIG-Cl with aqueous HCl and reused in another separation cycle. Finally, 35S-labeled sulfate and &#946; liquid scintillation counting are employed for monitoring the sulfate concentration in solution. Overall, this protocol will instruct the user in the necessary skills to synthesize a ligand, employ it in the selective crystallization of sulfate from aqueous solutions, and quantify the separation efficiency.

A protocol for in situ aqueous synthesis of a bis(iminoguanidinium) ligand and its utilization in selective separation of sulfate is presented.

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, ...

Capillary Electrophoresis to Monitor Peptide Grafting onto Chitosan Films in Real Time

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. Compared to other analytical separation techniques, such as chromatography, CE is cheap, robust and effectively requires no sample preparation (for a number of complex natural matrices or polymeric samples). CE is fast and can be used to follow the evolution of mixtures in real time (e.g., chemical reaction kinetics), as the signals observed for the separated compounds are directly proportional to their quantity in solution.
Here, the efficiency of CE is demonstrated for monitoring the covalent grafting of peptides onto chitosan films for subsequent biomedical applications. Chitosan&#39;s antimicrobial and biocompatible properties make it an attractive material for biomedical applications such as cell growth substrates. Covalently grafting the peptide RGDS (arginine - glycine - aspartic acid - serine) onto the surface of chitosan films aims at improving cell attachment. Historically, chromatography and amino acid analysis have been used to provide a direct measurement of the amount of grafted peptide. However, the fast separation and absence of sample preparation provided by CE enables equally accurate yet real-time monitoring of the peptide grafting process. CE is able to separate and quantify the different components of the reaction mixture: the (non-grafted) peptide and the chemical coupling agents. In this way the use of CE results in improved films for downstream applications.
The chitosan films were characterized through solid-state NMR (nuclear magnetic resonance) spectroscopy. This technique is more time-consuming and cannot be applied in real time, but yields a direct measurement of the peptide and thus validates the CE technique.

Free solution capillary electrophoresis is a fast, cheap and robust analytical method that enables the quantitative monitoring of chemical reactions in real time. Its utility for rapid, convenient and precise analysis is demonstrated here through analysis of covalent peptide grafting onto chitosan films for improved cell adhesion.

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. ...

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents warrants proper technique, thorough training, and proper personal protective equipment. To aid in the training of researchers using organolithium reagents, a thorough, step-by-step protocol for the safe and effective use of tert-butyllithium on an inert gas line or within a glovebox is described. As a model reaction, preparation of lithium tert-butyl amide by the reaction of tert-butyl amine with one equivalent of tert-butyl lithium is presented.

The safe and proper use of organolithium reagents is described.

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents ...

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 ...

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. Recently, we have developed a two-step strategy for ketone enolate umpolung that has enabled the development of methods for chlorination, azidation, and amination using azoles. In addition, we have developed C-C bond&#8211;forming arylation and allylation reactions. At the heart of these methods is the preparation of the intermediate and highly reactive enolonium species prior to addition of a reactive nucleophile. This strategy is thus reminiscent of the preparation and use of metal enolates in classical synthetic chemistry. This strategy allows the use of nucleophiles that would otherwise be incompatible with the strongly oxidizing hypervalent iodine reagents. In this paper we present a detailed protocol for chlorination, azidation, N-heteroarylation, arylation, and allylation. The products include motifs prevalent in medicinally active products. This article will greatly assist others in using these methods.

A two step one-pot protocol for the umpolung of ketone enolates to enolonium species and addition of a nucleophile to the &#945;-position is described. Nucleophiles include chloride, azide, azoles, allyl-silanes, and aromatic compounds.

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. ...

Reactive Inkjet Printing and Propulsion Analysis of Silk-based Self-propelled Micro-stirrers

In this study, a protocol for using reactive inkjet printing to fabricate enzymatically propelled silk swimmers with well-defined shapes is reported. The resulting devices are an example of self-propelled objects capable of generating motion without external actuation and have potential applications in medicine and environmental sciences for a variety of purposes ranging from micro-stirring, targeted therapeutic delivery, to water remediation (e.g., cleaning oil spills). This method employs reactive inkjet printing to generate well-defined small-scale solid silk structures by converting water soluble regenerated silk fibroin (silk I) to insoluble silk fibroin (silk II). These structures are also selectively doped in specific regions with the enzyme catalase in order to produce motion via bubble generation and detachment. The number of layers printed determines the three-dimensional (3D) structure of the device, and so here the effect of this parameter on the propulsive trajectories is reported. The results demonstrate the ability to tune the motion by varying the dimensions of the printed structures.

This protocol demonstrates the ability to utilize reactive inkjet printing to print self-motile biocompatible and environmentally friendly micro-stirrers for use in biomedical and environmental applications.

In this study, a protocol for using reactive inkjet printing to fabricate enzymatically propelled silk swimmers with well-defined shapes is reported. The ...