Name: studying surfactant effects on hydrate crystallization at oil-water interfaces using a low-cost integrated modular peltier device
Uploaded: 2020-03-18T12:00:00
Description: Watch this Scientific Journal Video about Studying Surfactant Effects on Hydrate Crystallization at Oil-Water Interfaces Using a Low-Cost Integrated Modular Peltier Device at JoVE.com

The authors thank American Chemical Society - Petroleum Research Fund (ACS - PFR), grant number: PRF # 57216-UNI9, for financial support.

1. Hydrate formation on water droplet in cyclopentane
NOTE: The experimental procedure described below is for the study of hydrate formation on a water droplet in cyclopentane using the IMPd and hydrate visualization cell described in the introduction.
<ol>
	<li>Attach a 19 G needle to the 1 mL glass syringe (Figure 2b, C).</li>
	<li>Rinse the 1 mL glass syringe and 19 G needle 3x with DI water.</li>
	<li>Fill the syringe with DI water.</li>
	<l...

<ol>
	<li>Graham, B., 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=.">.</a> Deep water: The Gulf Oil disaster and the future of offshore drilling. Report to the President. , (2011).</li><li>Hammerschmidt, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+gas+hydrates+in+natural+gas+transmission+lines.">Formation of gas hydrates in natural gas transmission lines.</a> Industrial &amp; Engineering Chemistry. 26, 851-855 (1934).</li><li>Sloan, E. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+changing+hydrate+paradigm-from+apprehension+to+avoidance+to+risk+management.">A changing hydrate paradigm-from apprehension to avoidance to risk management.</a> Fluid Phase Equilibria. 228-229, 67-74 (2005).</li><li>Xiaokai, L., Latifa, N., Abbas, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-agglomeration+in+cyclopentane+hydrates+from+bio-+and+co-surfactants.">Anti-agglomeration in cyclopentane hydrates from bio- and co-surfactants.</a> Energy &amp; Fuels. 24, 4937-4943 (2010).</li><li>Sloan, E. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fundamental+principles+and+applications+of+natural+gas+hydrates.">Fundamental principles and applications of natural gas hydrates.</a> Nature. 426, 353-363 (2003).</li><li>Sloan, E. D., Koh, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Clathrate Hydrates of Natural Gases. , (2007).</li><li>Lee, J. D., Englezos, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unusual+kinetic+inhibitor+effects+on+gas+hydrate+formation.">Unusual kinetic inhibitor effects on gas hydrate formation.</a> Chemical Engineering Science. 61, 1368-1376 (2006).</li><li>Daimaru, T., Yamasaki, A., Yanagisawa, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+surfactant+carbon+chain+length+on+hydrate+formation+kinetics.">Effect of surfactant carbon chain length on hydrate formation kinetics.</a> Journal of Petroleum Science and Engineering. 56, 89-96 (2007).</li><li>Karanjkar, P. U., Lee, J. W., Morris, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surfactant+effects+on+hydrate+crystallization+at+the+water-oil+interface:+hollow-conical+crystals.">Surfactant effects on hydrate crystallization at the water-oil interface: hollow-conical crystals.</a> Crystal Growth &amp; Design. 12, 3817-3824 (2012).</li><li>Leopercio, B. C., de Souza Mendes, P. R., Fuller, G. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+kinetics+and+mechanics+of+hydrate+films+by+interfacial+rheology.">Growth kinetics and mechanics of hydrate films by interfacial rheology.</a> Langmuir. 32, 4203-4209 (2016).</li><li>Karanjkar, P. U., Lee, J. W., Morris, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calorimetric+investigation+of+cyclopentane+hydrate+formation+in+an+emulsion.">Calorimetric investigation of cyclopentane hydrate formation in an emulsion.</a> Chemical Engineering Science. 68, 481-491 (2012).</li><li>Mori, Y. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Harkins-brown+correction+factor+for+drop+formation.">Harkins-brown correction factor for drop formation.</a> AIChE Journal. 36, 1272-1274 (1990).</li><li>Dann, K., Rosenfeld, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surfactant+effect+on+hydrate+crystallization+at+oil-water+interface.">Surfactant effect on hydrate crystallization at oil-water interface.</a> Langmuir. 34 (21), 6085-6094 (2018).</li><li>Ibach, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Physics of Surfaces and Interfaces. , (2006).</li></ol>

In this article we describe an experimental technique to study hydrate crystallization at the oil-water interface in the presence of nonionic surfactants. The apparatus is comprised of a temperature control system and a visualization cell that includes a brass chamber with windows, CMOS camera, and pressure transducer. The temperature control system is comprised of a microcontroller, powerful Peltier plate, 120 mm CPU cooler as the heatsink, and a waterproof digital temperature sensor. A hydrate visualization brass cell ...

The incentive to understand the mechanism of hydrate crystallization and inhibition comes from the fact that hydrates occur naturally in oil pipelines and can result in difficulties in flow assurance. For example, the 2010 Gulf of Mexico oil spill1 was a result of hydrate accumulation in an underwater oil piping system, causing contamination to the environment. Hence, understanding hydrate formation and inhibition is crucial in order to prevent future environmental disasters. Much of the driving force for the study of hydrate crystallization in the past years is the oil industry&#39;s effort to prevent hydrate plug agglomeration and the subsequent blockage of flow. The first study to determine that hydrates were responsible for plugged flowlines was done by Hammerschmidt in 19342. To this day, oil producers find it highly important to understand and inhibit hydrate formation for flow assurance3.
One way to prevent hydrate formation is to insulate deep water pipelines so that ice does not form. However, it is expensive to adequately insulate the pipelines, and the additional costs can be in the order of $1 million/km3. Thermodynamic inhibitors, such as methanol, can be injected into wellheads to prevent the formation of hydrates. However, large volumetric ratios of water to alcohol, as great as 1:1, are needed in order to adequately prevent the formation of hydrates4. Recently, the global cost to use methanol for hydrate prevention has been reported as $220 million/year. This is not a sustainable amount of alcohol usage5. In addition, the use of methanol is problematic because it is environmentally hazardous, and cannot be used for large-scale transport5. Alternatively, kinetic inhibitors, such as surfactants, can suppress hydrate growth at small quantities and temperatures of up to 20 &#176;C6. Hence, surfactant presence can reduce the large amount of alcohols needed for hydrate prevention.
Surfactants are considered good inhibitors for hydrate crystallization due to two main reasons:
1) They can inhibit hydrate formation through surface property changes; and 2) They initially help the formation of hydrate cells but prevent further growth and agglomeration of the crystal down the pipeline7. Although surfactants have proved to be efficient inhibitors, there is still a large amount of information missing regarding the crystallization process in the presence of surfactants. While some studies have shown that the use of surfactants can extend the initial hydrate crystallization time at certain subcoolings, other studies have found exceptions at low surfactant concentrations. At low surfactant concentrations, the water droplets tend to coalesce and accelerate the process of hydrate formation8. The inhibition process has been explained by surfactant molecules interrupting planar hydrate growth, forcing the hydrate into hollow-conical crystal formation. The conical crystals form a mechanical barrier for crystal growth9, and thus inhibit the growth.
In this study we designed and implemented a low-cost, integrated modular Peltier device (IMPd) along with a hydrate visualization cell and used them to study cyclopentane hydrate formation in the presence of nonionic surfactants. The reason for using cyclopentane instead of low molecular weight gases (e.g., CH4 and CO2) that usually form hydrates in deep sea reservoirs, is that these gases require higher pressures and lower temperatures to form stable hydrates. Because cyclopentane forms hydrates at ambient pressure and temperatures up to ~7.5 &#176;C, it is often used as a model material for hydrate formation10.
The integrated modular Peltier device (IMPd) consists of an open-source microcontroller, Peltier plate, CPU cooler (heat sink), and waterproof digital temperature sensor. The device can deliver a maximum temperature differential of 68 &#176;C. The minimum temperature resolution is 1/16 &#176;C. The entire system, including the electrical circuitry and hardware, can be constructed for less than $200. The temperature sensor reports to the microcontroller, which sends output signals to the transistor. The transistor then passes current from the DC power source through the Peltier element. The heat sink helps cool the Peltier element by convecting the heat coming from the hot side of the Peltier to the ambient air. The assembled hardware components of the IMPd system are shown in Figure 1a,b. Figure 1c shows the wiring schematic with all the components of the control loop (proportional-integral-derivative [PID] controller) and the pin-outs. The output current of the microcontroller was limited with the gate resistor R1 to a maximum current of 23 mA (I = 5 V/220 W). The pull-down resistor R2 in Figure 1c allows the gate charge to dissipate and to turn the system off. To tune the PID controller, Ziegler-Nichols based methods combined with an iterative process are used11. Microcontroller integrated development environment (IDE) software is used to monitor and send commands to the microcontroller for temperature regulation.
Along with the IMPd, we applied a novel approach using visualization techniques and internal pressure measurements. The hydrate visualization cell, which is placed on top of the IMPd, is comprised of a brass cell equipped with two double-paned observation windows. The windows allow video recording of the hydrate formation process on the water droplet in cyclopentane. The complementary metal-oxide semiconductor (CMOS) camera is placed outside the window and the pressure transducer is connected to the water injection line in order to get the internal pressure measurements of the drop. A digital transducer application is used to get the readings from the pressure transducer. A camera viewer is used to capture the videos and images from the CMOS camera. The software controls the exposure and snapshot frequency. Image processing software programs are used to track the growth of the hydrate. Figure 2a shows a schematic description of the hydrate visualization cell and Figure 2b shows an overview of the entire experimental system. The seed hydrate (Figure 2a) is required for consistent nucleation and tracking of the hydrate growth rate. The seed hydrate is a small volume (e.g., 50&#8211;100 &#181;L) of pure water deposited on the floor of the hydrate cell. As the temperature decreases, the drop forms ice, which then turns to hydrate as the temperature increases. The small piece of the seed hydrate then contacts the water droplet. This process controls the initiation of the hydrate in the submerged water droplet. Silica desiccant is inserted into the gap between the two glass slides (Figure 2c), which serve as viewing windows. The silica desiccant helps reduce the amount of frosting and fogging on the windows. Anti-fog is also applied to the outer window to reduce fogging. Images are captured with a CMOS camera and a 28&#8211;90 mm lens. A 150 W fiber optic goose-neck lamp is used for illumination. An acrylic cover is placed on top of the brass cell in order to limit evaporation of cyclopentane. Plumbing consists of a combination of flexible polytetrafluoroethylene (PTFE) tubing and rigid brass tubing. A syringe pump with a 1 mL glass syringe and a 19 G needle control the flow of water and surfactant solution. A pressure transducer monitors the pressure changes inside the water surfactant solution droplet. 19 G PTFE tubing connects the syringe to the T-fitting and 1/16 in. (1.588 mm) brass tubing connects the transducer and brass hook to the T-fitting (Figure 2d). A brass hook, approximately 5 cm in length with a 180&#176; bend, generates the water/surfactant solution droplet. The bend ensures that the droplet generated by the syringe sits on top of the tube throughout the experiment. A 1/16 in. stainless steel T-fitting in conjunction with PTFE crush ferrules and PTFE thread tape seal the fittings.
Using this apparatus, we examined four different nonionic surfactants with different hydrophilic-lipophilic balances (HLB) that are commonly used in the oil industry: sorbitane monolaurate, sorbitane monooleate, PEG-PPG-PEG, and polyoxyethylenesorbitan tristearate.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1/16 in. Swagelok 316 stainless steel T-fitting</td>
			<td>Swagelok</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>19 gauge PTFE tubing</td>
			<td>Scientific Commodities, Inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>19-gauge needle (model: 1001 LTSN SYR)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1-Wire DS18B20 - waterproof digital temperature sensor</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Anti fog</td>
			<td>RainX</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Arduino Leonardo open-source microcontroller</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Brass tubing 1/16 in.</td>
			<td>K&#38;S Precision Metals</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Chemyx Fusion 100 Infusion Pump</td>
			<td>Chemyx</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>cMOS camera acA640-750um</td>
			<td>Basler</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cyclopentane 98% extra pure</td>
			<td>ACROS organics</td>
			<td>AC111481000</td>
			<td></td>
		</tr>
		<tr>
			<td>Fiber optic goose-neck lamp 150W</td>
			<td>AmScope</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fotodiox macro extension tubes, 35 mm</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hamilton glass syringe 1 mL</td>
			<td>Hamilton</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ImageJ software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Kipon EOS to C-mount adapter</td>
			<td>Kipon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Lens 28-90 mm</td>
			<td>Canon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mathematica software</td>
			<td>Mathematica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>OMEGA PX409-10WGUSBH pressure transducer</td>
			<td>OMEGA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Peltier plate TEC1-12715</td>
			<td>Amazon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pluronic L31 (PEG-PPG-PEG)</td>
			<td>Sigma Aldrich</td>
			<td>9003-11-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Pylon Viewer v5.0.0.6150</td>
			<td>Basler</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Span 20 (Sorbitan laurate, Sorbitan monolaurate)</td>
			<td>Sigma Aldrich</td>
			<td>1338-39-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Span 80 (Sorbitan Monooteate)</td>
			<td>Sigma Aldrich</td>
			<td>1338-43-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermaltake NiC C4 120mm CPU cooler</td>
			<td>Thermaltake</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tween 65 (Polyoxyethylenesorbitan Tristearate)</td>
			<td>Sigma Aldrich</td>
			<td>9005-71-4</td>
			<td></td>
		</tr>
		<tr>
			<td>variable Tooluxe DC power supply</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

studying surfactant effects on hydrate crystallization at oil-water interfaces using a low-cost integrated modular peltier device

We introduce an approach to study the formation and growth of hydrates under the influence of nonionic surfactants. The experimental system includes a temperature regulator, visualization techniques, and inner pressure measurements. The temperature control system contains a low-cost, programmable temperature regulator made with solid-state Peltier components. Along with the temperature control system, we incorporated visualization techniques and internal pressure measurements to study hydrate formation and inhibition in the presence of nonionic surfactants. We studied the hydrate-inhibiting ability of nonionic surfactants (sorbitane monolaurate, sorbitane monooleate, PEG-PPG-PEG, and polyoxyethylenesorbitan tristearate) at low (i.e., 0.1 CMC), medium (i.e., CMC), and high (i.e., 10 CMC) concentrations. Two types of crystals were formed: planar and conical. Planar crystals were formed in plain water and low surfactant concentrations. Conical crystals were formed in high surfactant concentrations. The results of the study show that conical crystals are the most effective in terms of hydrate inhibition. Because conical crystals cannot grow past a certain size, the hydrate growth rate as a conical crystal is slower than the hydrate growth rate as planar crystal. Hence, surfactants that force hydrates to form conical crystals are the most efficient. The goal of the protocol is to provide a detailed description of an experimental system that is capable of investigating the cyclopentane hydrate crystallization process on the surface of a water droplet in the presence of surfactant molecules.

Using this experimental system one can examine the hydrate formation at the oil-water interface and measure the interfacial stress associated with the crystallization process. Figure 6 shows a representative set of results that include both crystal formation and interfacial stress. In the planar shell growth (Figure 6a), the crystal grew from the two poles towards the equator. For that reason, in the planar crystal, the hydrate shell grew consta...

Watch this Scientific Journal Video about Studying Surfactant Effects on Hydrate Crystallization at Oil-Water Interfaces Using a Low-Cost Integrated Modular Peltier Device at JoVE.com

Studying Surfactant Effects on Hydrate Crystallization at Oil-Water Interfaces Using a Low-Cost Integrated Modular Peltier Device

We present a protocol to study the formation of hydrates in the presence of nonionic surfactants on the interface of a water droplet submerged in cyclopentane. The protocol consists of building a low-cost, programmable, temperature regulator. The temperature control system is combined with visualization techniques and internal pressure measurements.

We introduce an approach to study the formation and growth of hydrates under the influence of nonionic surfactants. The experimental system includes a ...

The protocol is applicable in studying the effect of surfactant inhibitors on hydrate crystals. It provides information on both the type of the crystal and the mechanism for inhibition. Attach a 19 gauge needle to a one milliliter glass syringe.Rinse the needle and syringe three times with deionized water and then fill the syringe with deionized water. Next, fill the hydrate visualization cell with 25 milliliters of cyclopentane. Using the syringe, insert a droplet of deionized water at the bottom of the hydrate visualization cell.This water droplet is the seed hydrate. Then, place the temperature sensor inside the hydrate visualization cell close to the bottom of the cell. To prevent evaporation of the cyclopentane, put the acrylic cover on the cell and screw the cover in place.Adjust the lights and the camera to focus on the seed hydrate. Using the temperature control device, set the temperature of the Peltier plate to negative five degrees Celsius. Monitor the values reported from the temperature sensor.When the temperature reaches negative five degrees Celsius, make sure the seed hydrate at the bottom of the hydrate visualization chamber turns to ice. Set the temperature of the Peltier plate to two degrees Celsius in increments of 0.5 degrees Celsius. When the temperature reaches two degrees Celsius, fill the plumbing with water using the syringe.Then, lower the brass hook into the cyclopentane and allow it to equilibrate for five minutes. Using the software for the pressure transducer, press the Start button to start the digital transducer recordings. Connect the syringe to the syringe pump, set the syringe pump to inject a volume of two microliters and activate it.The syringe will plunge the water into the cyclopentane bath to form a submerged water droplet. Use a needle tip to remove a small piece of the seed hydrate. Bring the needle tip with the piece of seed hydrate into brief contact with the water droplet to initiate the formation of the hydrate.Press Start Recording on the camera capture software. Record images of the crystallization process at one Hertz. To find the critical micelle concentration, begin by preparing standard solutions as described in the manuscript.To measure the surface tension of each surfactant solution using the stalagmometry method, program the pump to expel one milliliter of solution at a rate of 0.5 milliliters per minute. Place the syringe pump and syringe vertically and release the drops into the air. Count the number of drops and divide one milliliter by the number of drops to find the drop volume.For each solution, calculate the surface tension as described in the manuscript and plot the surface tension as a function of surfactant concentration. The concentration where the surface tension curve flattens is the CMC, the critical micelle concentration. Repeat the procedure used to measure hydrate formation on a water droplet, but use surfactant solutions of various concentrations.Use image processing software to open the first image in the sequence of the crystallization process. Use the length tool in the software to measure the diameter of the brass tube in the image. Set the scale in the image based on the known diameter of the brass tube, one sixteenth of an inch.Select 10 equally spaced images, which capture the process from nucleation to droplet conversion. For each image, use the software to manually detect the contour of the drop and mark the contour in red. Then, manually trace the contour of the hydrate and fill the contour with black.The camera only captures the 2D projection of the spherical droplet. Use mathematical modeling software to form a 3D reconstruction of the drop and the surface area covered by the hydrate. Using this experimental system, one can examine hydrate formation at the oil water interface and measure the interfacial stress associated with the crystallization process.In pure water and low surfactant concentrations, the hydrate formed a planar shell morphology, growing at a constant rate from the two poles towards the equator. As the hydrate grew, the same number of surfactant molecules occupied a smaller area, resulting in decreased interfacial stress over time. In high surfactant concentrations, the hydrate grew as a conical crystal.When the crystal became large enough, a portion of the cone broke free from the droplet surface. This growth pattern happened over and over again in an oscillatory manner. After the conical crystal reached a critical size and detached from the droplet's surface, the sudden increase in the available surface for surfactant molecules caused an increase in the interfacial stress.A crystal then started growing again, yielding an oscillatory pattern. Most surfactant solutions inhibited hydrate growth compared to pure water. A high concentration of polyoxyethylene sorbitan tristereate was the most effective inhibitor.This system can provide information on why some surfactants inhibit hydrates better than others. The system can also be used to study the general formation of crystals at interfaces.

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Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into ...

Rapid High-throughput Species Identification of Botanical Material Using Direct Analysis in Real Time High Resolution Mass Spectrometry

We demonstrate that direct analysis in real time-high resolution mass spectrometry can be used to produce mass spectral profiles of botanical material, and that these chemical fingerprints can be used for plant species identification. The mass spectral data can be acquired rapidly and in a high throughput manner without the need for sample extraction, derivatization or pH adjustment steps. The use of this technique bypasses challenges presented by more conventional techniques including lengthy chromatography analysis times and resource intensive methods. The high throughput capabilities of the direct analysis in real time-high resolution mass spectrometry protocol, coupled with multivariate statistical analysis processing of the data, provide not only class characterization of plants, but also yield species and varietal information. Here, the technique is demonstrated with two psychoactive plant products, Mitragyna speciosa (Kratom) and Datura (Jimsonweed), which were subjected to direct analysis in real time-high resolution mass spectrometry followed by statistical analysis processing of the mass spectral data. The application of these tools in tandem enabled the plant materials to be rapidly identified at the level of variety and species.

A method for species identification of botanical material by direct analysis in real time-high resolution mass spectrometry and multivariate statistical analysis is presented.

We demonstrate that direct analysis in real time-high resolution mass spectrometry can be used to produce mass spectral profiles of botanical material, ...

Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod

Aquatic sediment core subsampling is commonly performed at cm or half-cm resolution. Depending on the sedimentation rate and depositional environment, this resolution provides records at the annual to decadal scale, at best. An extrusion method, using a calibrated, threaded-rod is presented here, which allows for millimeter-scale subsampling of aquatic sediment cores of varying diameters. Millimeter scale subsampling allows for sub-annual to monthly analysis of the sedimentary record, an order of magnitude higher than typical sampling schemes. The extruder consists of a 2 m aluminum frame and base, two core tube clamps, a threaded-rod, and a 1 m piston. The sediment core is placed above the piston and clamped to the frame. An acrylic sampling collar is affixed to the upper 5 cm of the core tube and provides a platform from which to extract sub-samples. The piston is rotated around the threaded-rod at calibrated intervals and gently pushes the sediment out the top of the core tube. The sediment is then isolated into the sampling collar and placed into an appropriate sampling vessel (e.g., jar or bag). This method also preserves the unconsolidated samples (i.e., high pore water content) at the surface, providing a consistent sampling volume. This mm scale extrusion method was applied to cores collected in the northern Gulf of Mexico following the Deepwater Horizon submarine oil release. Evidence suggests that it is necessary to sample at the mm scale to fully characterize events that occur on the monthly time-scale for continental slope sediments.

An extrusion method using a calibrated threaded-rod is presented, which allows for mm scale subsampling of aquatic sediment cores. Millimeter-scale sampling is necessary to fully characterize recent event stratigraphy in sediment records.

Aquatic sediment core subsampling is commonly performed at cm or half-cm resolution. Depending on the sedimentation rate and depositional environment, ...

A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) hydrogen fuel cells. Researchers seeking to develop such systems require a method of measuring the generated hydrogen. Herein, we describe a simple, low-cost, and robust method to measure the hydrogen generated from the reaction of solids with aqueous solutions. The reactions are conducted in a conventional one-necked round-bottomed flask placed in a temperature controlled water bath. The hydrogen generated from the reaction in the flask is channeled through tubing into a water-filled inverted measuring cylinder. The water displaced from the measuring cylinder by the incoming gas is diverted into a beaker on a balance. The balance is connected to a computer, and the change in the mass reading of the balance over time is recorded using data collection and spreadsheet software programs. The data can then be approximately corrected for water vapor using the method described herein, and parameters such as the total hydrogen yield, the hydrogen generation rate, and the induction period can also be deduced. The size of the measuring cylinder and the resolution of the balance can be changed to adapt the setup to different hydrogen volumes and flow rates.

The study of methods to generate on-demand hydrogen for fuel cells continues to grow in importance. However, systems to measure hydrogen evolution from the reaction of chemicals with water can be complicated and expensive. This article details a simple, low-cost, and robust method to measure the evolution of hydrogen gas.

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) ...

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, ...

Green and Low-cost Production of Thermally Stable and Carboxylated Cellulose Nanocrystals and Nanofibrils Using Highly Recyclable Dicarboxylic Acids

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils (CNF) from bleached eucalyptus pulp (BEP) and unbleached mixed hardwood kraft pulp (UMHP) fibers using highly recyclable dicarboxylic solid acids. Typical operating conditions were acid concentrations of 50 - 70 wt% at 100 &#176;C for 60 min and 120 &#176;C (no boiling at atmospheric pressure) for 120 min, for BEP and UMHP, respectively. The resultant CNCs have a higher thermal degradation temperature than their corresponding feed fibers and carboxylic acid group content from 0.2 - 0.4 mmol/g. The low strength (high pKa of 1.0 - 3.0) of organic acids also resulted in CNCs with both longer lengths of approximately 239 - 336 nm and higher crystallinity than CNCs produced using mineral acids. Cellulose loss to sugar was minimal. Fibrous cellulosic solid residue (FCSR) from the dicarboxylic acid hydrolysis was used to produce carboxylated CNFs through subsequent mechanical fibrillation with low energy input.

Here we demonstrate a novel method for green and sustainable productions of highly thermally stable and carboxylated cellulose nanocrystals (CNC) and nanofibrils (CNF) using highly recyclable solid dicarboxylic acids.

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils ...

Phase Behavior of Charged Vesicles Under Symmetric and Asymmetric Solution Conditions Monitored with Fluorescence Microscopy

Phase-separated giant unilamellar vesicles (GUVs) exhibiting coexisting liquid-ordered and liquid-disordered domains are a common biophysical tool to investigate the lipid raft hypothesis. Numerous studies, however, neglect the impact of physiological solution conditions. On that account, the current work presents the effect of high-salinity buffer and trans-membrane solution asymmetry on liquid-liquid phase separation in charged GUVs grown from dioleylphosphatidylglycerol, egg sphingomyelin, and cholesterol. The effects were studied under isothermal and varying temperature conditions.
We describe equipment and experimental strategies applicable for monitoring the stability of coexisting liquid domains in charged vesicles under symmetric and asymmetric high-salinity solution conditions. This includes an approach to prepare charged multicomponent GUVs in high-salinity buffer at high temperatures. The protocol entails the option to perform a partial exchange of the external solution by a simple dilution step while minimizing the vesicle dilution. An alternative approach is presented utilizing a microfluidic device that allows for a complete external solution exchange. The solution effects on phase separation were also studied under varying temperatures. To this end, we present the basic design and utility of an in-house built temperature control chamber. Furthermore, we reflect on the assessment of the GUV phase state, pitfalls associated with it and how to circumvent them.

Experiments on phase separated giant unilamellar vesicles (GUVs) frequently neglect physiological solution conditions. This work presents approaches to study the effect of high-salinity buffer on liquid-liquid phase separation in charged multicomponent GUVs as a function of trans-membrane solution asymmetry and temperature.

Phase-separated giant unilamellar vesicles (GUVs) exhibiting coexisting liquid-ordered and liquid-disordered domains are a common biophysical tool to ...

Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering

We demonstrate a protocol to effectively monitor the gelation process of a high concentration solution of conjugated polymer both in the presence and absence of white light exposure. By instituting a controlled temperature ramp, the gelation of these materials can be precisely monitored as they proceed through this structural evolution, which effectively mirrors the conditions experienced during the solution deposition phase of organic electronic device fabrication. Using small angle neutron scattering (SANS) and ultra-small angle neutron scattering (USANS) along with appropriate fitting protocols we quantify the evolution of select structural parameters throughout this process. Thorough analysis indicates that continued light exposure throughout the gelation process significantly alters the structure of the ultimately formed gel. Specifically, the aggregation process of poly(3-hexylthiophene-2,5-diyl) (P3HT) nano-scale aggregates is negatively affected by the presence of illumination, ultimately resulting in the retardation of growth in conjugated polymer microstructures and the formation of smaller scale macro-aggregate clusters.

A protocol for the analysis of gels formed from the optoelectronic conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) using small and ultra-small angle neutron scattering in both the presence and absence of illumination is presented.

We demonstrate a protocol to effectively monitor the gelation process of a high concentration solution of conjugated polymer both in the presence and ...

Automated 90Sr Separation and Preconcentration in a Lab-on-Valve System at Ppq Level

A quick, automated and portable system for the separation and determination of radiostrontium in aqueous samples, using Sr-resin and multi sequential flow injection analysis, has been developed. The concentrations of radioactive strontium were determined by flow scintillation counting, allowing for on-line and also on-site determination. The proposed system can determine radioactive strontium at industrial relevant levels without further modification using overall analysis time of less than 10 min per aqueous sample. The limit of the detection is 320 fg&#183;g-1 (1.7 Bq/g).

Automated 90Sr Separation and Preconcentration in a Lab-on-Valve System at Ppq Level

Here, we present the portable autoRAD platform for quick radiometric separation and determination of 90Sr, an important fission product highly pertinent to nuclear waste.

A quick, automated and portable system for the separation and determination of radiostrontium in aqueous samples, using Sr-resin and multi sequential flow ...