Name: minimum burning pressures of water-based emulsion explosives
Uploaded: 2017-10-31T13:00:00
Description: Watch this Scientific Journal Video about Minimum Burning Pressures of Water-based Emulsion Explosives at JoVE.com

The development of the testing protocol reported in this publication results from a joint research project between Natural Resources Canada (CanmetCERL, Explosives R&#38;D Section) and Orica Mining Services. Permission of Orica Mining Services to publish non-proprietary information on this subject is fully acknowledged. The participation of CanmetCERL&#39;s Analytical Section to the physical characterization of the various AWEs prepared throughout the present work is also gratefully acknowledged.

NOTE: The materials and equipment used here are listed in the Table of Materials.
1. Preparation of Ignition Wire Assemblies
NOTE: Wearing nitrile gloves is recommended for this operation.
<ol>
	<li>Measure a pre-determined length of nichrome (NiCr) wire and cut using a wire cutter. Cut 85 mm lengths for 76.2 mm (3&#34;) long test cells.</li>
	<li>Using needle nose pliers, bend the NiCr wire to make a small loop at each end. With a proper crimping tool, splice eac...

<ol>
	<li>Bluhm, H. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ammonium+nitrate+emulsion+blasting+agent+and+method+of+preparing+same.">Ammonium nitrate emulsion blasting agent and method of preparing same.</a> US Patent. , (1969).</li><li>Persson, P. -. A., Holmberg, R., Lee, 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> Rock Blasting and Explosives Engineering. , 86 (1993).</li><li>Perlid, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pump+Safety+Tests+Regarding+Emulsion+Explosives.">Pump Safety Tests Regarding Emulsion Explosives.</a> Proceedings of the 22nd Annual Conference on Explosives and Blasting Techniques, International Society of Explosives Engineers. 2, 101-107 (1996).</li><li>Chan, S. K., Kirchnerova, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ignition+and+Combustion+Characteristics+of+Water-gel+Explosives.">Ignition and Combustion Characteristics of Water-gel Explosives.</a> Proceedings of the 18th Explosives Safety Seminar, U.S. DOD. , 193-200 (1978).</li><li>Guidelines for the Pumping of Water-Based Explosives. Natural Resources Canada, Explosives Regulatory Division, Minister of Public Works and Government Services Canada, Catalog no. M37-53/2003E Available from: <a target="_blank" href="https://miningandblasting.files.wordpress.com/2009/09/canadian-guidelines-for-pumping-of-water-based-explosives.pdf">https://miningandblasting.files.wordpress.com/2009/09/canadian-guidelines-for-pumping-of-water-based-explosives.pdf</a> (2016)</li><li>. Guidelines for the Pumping of Bulk, Water-Based Explosives Available from: <a target="_blank" href="https://miningandblasting.files.wordpress.com/2009/09/pumping-of-water-based-explosives-june-2010.pdf">https://miningandblasting.files.wordpress.com/2009/09/pumping-of-water-based-explosives-june-2010.pdf</a> (2010)</li><li>Wang, 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> Ignition and Combustion Characteristics of Emulsion Explosives under Pressure. , (1991).</li><li>Hirosaki, Y., Suzuki, S., Takahashi, Y., Kato, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Burning+Characteristics+of+Emulsion+Explosives+(I)+–+Pressurized+Vessel+Test.">Burning Characteristics of Emulsion Explosives (I) – Pressurized Vessel Test.</a> Kayaku Gakkaishi. 61, 35-41 (2000).</li><li>Turcotte, R., Lightfoot, P. D., Badeen, C. M., Vachon, M., Jones, D. E. 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+Pressurized+Vessel+Test+to+Measure+the+Minimum+Burning+Pressure+of+Water-Based+Explosives.">A Pressurized Vessel Test to Measure the Minimum Burning Pressure of Water-Based Explosives.</a> Propellants, Explos., Pyrotech. 30, 118-126 (2005).</li><li>Turcotte, R., Goldthorp, S., Badeen, C., Chan, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hot-wire+Ignition+of+AN-based+Emulsions.">Hot-wire Ignition of AN-based Emulsions.</a> Propellants, Explos., Pyrotech. 33, 472-481 (2008).</li><li>Chan, S. K., Turcotte, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Onset+Temperatures+in+Hot-wire+Ignition+of+AN-Based+Emulsions.">Onset Temperatures in Hot-wire Ignition of AN-Based Emulsions.</a> Propellants, Explos., Pyrotech. 34, 41-49 (2009).</li><li>Goldthorp, S., Turcotte, R., Badeen, C. M., Chan, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Minimum+Pressure+for+Sustained+Combustion+in+AN-based+Emulsions.">Minimum Pressure for Sustained Combustion in AN-based Emulsions.</a> Proceedings of the 35th International Pyrotechnics Seminar. , 385-394 (2008).</li><li>Turcotte, R., Goldthorp, S., Badeen, C. M., Feng, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+Physical+Characteristics+and+Ingredients+on+the+Minimum+Burning+Pressure+of+Ammonium+Nitrate+Emulsions.">Influence of Physical Characteristics and Ingredients on the Minimum Burning Pressure of Ammonium Nitrate Emulsions.</a> Propellants, Explos., Pyrotech. 35, 233-239 (2010).</li><li>Badeen, C. M., Goldthorp, S., Turcotte, R., Feng, H., Chan, S. K. <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+Formulation+Changes+on+the+Minimum+Burning+Pressure+of+Ammonium+Nitrate+Emulsions.">Effect of Formulation Changes on the Minimum Burning Pressure of Ammonium Nitrate Emulsions.</a> Proceedings of the "10i&#232;me Congr&#232;s International de Pyrotechnie", in conjunction with the 37th International Pyrotechnics Seminar (Europyro 2011) , Session S1a. , (2011).</li><li>Turcotte, R., Goldthorp, S., Badeen, C. M., Johnson, C., Feng, H., Chan, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+Physical+Characteristics+and+Ingredients+on+the+Minimum+Burning+Pressure+of+Ammonium+Nitrate+Emulsions.">Influence of Physical Characteristics and Ingredients on the Minimum Burning Pressure of Ammonium Nitrate Emulsions.</a> , 197-206 (2009).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria. , 200-207 (2015).</li><li>The Minimum Burning Test for Ammonium Nitrate Emulsions. SAFEX Newsletter Available from: <a target="_blank" href="https://www.safex-international.org/safex/page-newsletter.html">https://www.safex-international.org/safex/page-newsletter.html</a> (2016)</li></ol>

Our work demonstrated that the linear hot-wire geometry with 0.5 mm diameter NiCr straight wire and 10 to 16 A ignition current was adequate to ignite AWEs with water contents up to 25 mass %. For high viscosity formulations (such as packaged emulsion products), horizontal and vertical configurations provide almost identical results 17. However, for low viscosity formulae (such as bulk emulsion products) gravity effects in vertical configuration induce emulsion flow which disturbs the ignition pro...

The ammonium nitrate water-based emulsion (AWE) explosive was invented in 1961. It consists of microscopic droplets of a liquid oxidizer solution surrounded by a continuous oil phase. The first stable and practically useful emulsion blasting explosive was developed by Harold F. Bluhm in the USA (1969) 1,2. However, the successful commercialization of this type of explosive did not really happen before the beginning of the 1980s.
With the large scale of modern mining operations and the advent of fast bulk explosive loading methodology, very large volumes of AWE explosives have to be manufactured and transported. One tanker load typically transports 20 tons of AWE and many such truck loads are usually necessary to load only one blast. Accidental initiation of such large quantities of explosives would be particularly disastrous and, therefore, a good knowledge of their hazardous properties is required to design corresponding safe handling systems. While it is well known that emulsions are relatively insensitive to mechanical events (i.e. impact and friction events), accidental explosions have still been reported 3 while handling this type of explosive, particularly in pumping applications.
It has been known since the 1970&#39;s 4 that a minimum ambient pressure is required for self-sustained combustion to take place into water-based explosives. This latter value has usually been termed the &#34;Minimum Burning Pressure&#34; (MBP). From a safety point of view, knowledge of this threshold could allow manufacturers to better estimate safe operating pressures for various handling equipment.
The Department of Natural Resources of the Government of Canada has published &#34;Guidelines for the Pumping of Water-Based explosives&#34; 5, which state that using pumping pressures well below the MBP of the emulsions or watergels is a good safety practice. It should be noticed that these guidelines were designed with the collaboration of most commercial manufacturers and that, in the USA, the Institute of Makers of Explosives (IME) has also published very similar guidelines 6. However, in these documents, there was no description or prescription on how the MBP should be measured.
In the last decades, only a few studies related to MBP measurements have been reported. Chan et al. 4 reported the results of MBP measurements for watergel explosives, which are also ammonium nitrate and water-based. They have concluded that the MBP can have a strong dependency on several formulation factors such as water content, presence of chemical sensitizers or metallic powders. In another study, Wang 7 described a 2.5 L pressure vessel pressurized with N2 and used a Bruceton up-and-down method to determine the MBP for basic AWEs. With this system, MBP values of the order of 15 MPa were measured for a basic emulsion having a water content of 16 mass %.
Using a similar pressurized vessel test, Hirosaki et al. 8 have reported the results of some MBP measurements for AWE explosives. They have noted that the nature (i.e. glass or resin) of the micro-spheres being used to sensitize the explosives also has a strong influence on the results. More recently, Turcotte et al. 9 have developed a system similar to that of Wang and Hirosaki et al. and have attempted to use it to measure the MBP of some AWEs. However, they have found many possible problems that may lead to erroneous MBP determinations. In particular, it was noted that the ignition source geometry (nichrome wire coil) had never been properly validated for AWEs. In 2008, Turcotte et al. 10 and Chan et al. 11, have developed both an apparatus based on a calibrated ignition wire system and an associated methodology to measure the MBP of AWEs. They have also used the facility to study the ignition characteristics of typical AWEs, measured the energy requirements to obtain reliable ignitions 12 and studied the influence of physical characteristics and ingredients on the MBP of a wide variety of AWE explosives 13,14. This MBP measurement technique is presently being proposed as a standard test within the United Nation Transport of Dangerous Goods (UN TDG) Tests and Criteria for the classification for transport of AWEs 15.

<table>
	<tbody>
		<tr>
			<td>Nitrile gloves (100/pk)</td>
			<td>Fisher Scientific</td>
			<td>19149863B</td>
			<td>https://www.fishersci.ca/shop/products/purple-nitrile-exam-gloves-6/19149863b?searchHijack=true&#38;searchTerm=19149863B&#38;searchType=RAPID&#38;matchedCatNo=19149863B</td>
		</tr>
		<tr>
			<td>NiCr60 wire 24 AWG (200 feet per roll)</td>
			<td>Omega Engineering</td>
			<td>NIC60-020-200</td>
			<td>http://www.omega.ca/pptst_eng/NI60.html</td>
		</tr>
		<tr>
			<td>Wire cutters: Mini Diagonal Cutting Pliers, 5 in.</td>
			<td>Canadian Tire</td>
			<td>Product #058-4736-0</td>
			<td>http://www.canadiantire.ca/en/pdp/mastercraft-mini-diagonal-cutting-pliers-0584736p.html#srp</td>
		</tr>
		<tr>
			<td>Mini needle nose pliers, 5 in.</td>
			<td>Canadian Tire</td>
			<td>Product #058-4731-0</td>
			<td>http://www.canadiantire.ca/en/pdp/mastercraft-mini-needle-nose-pliers-0584731p.html#srp</td>
		</tr>
		<tr>
			<td>Crimping tool, 8.5 in.</td>
			<td>Canadian Tire</td>
			<td>Product #058-4617-4</td>
			<td>http://www.canadiantire.ca/en/pdp/mastercraft-8-in-crimping-tool-0584617p.html#srp</td>
		</tr>
		<tr>
			<td>Bare copper wire (14AWG)</td>
			<td>Electronics Plus</td>
			<td>2000BC-14-5/5 lb roll</td>
			<td>Bare (uninsulated) copper wire</td>
		</tr>
		<tr>
			<td>Non-insulated butt-splice connectors (100 units)</td>
			<td>Electrosonic</td>
			<td>Panduit BS14-C</td>
			<td>http://www.alliedelec.com/panduit-bs14-c/70044299/?mkwid=si03ezhXY&#38;pcrid=64596948257&#38;pkw=panduit%20bs14-c&#38;pmt=b&#38;pdv=c&#38;gclid=CM_1jO-DsdMCFZKIswodMugASw</td>
		</tr>
		<tr>
			<td>Stainless Steel pipe nipples (10 - 20 units)</td>
			<td>Wolseley Inc.</td>
			<td>SSNKX3</td>
			<td>sample cells: 76.2 mm long x 12.7 mm od (3&#34; long x 0.5&#34; od) with 3 mm slit machined along the length of the cell, painted inside and out with two coats of non-conductive paint (e.g., high-heat barbeque Armor Coat or Krylon brands).</td>
		</tr>
		<tr>
			<td>High-temperature non-conductive paint</td>
			<td>Canadian Tire</td>
			<td>Product #048-0648-8</td>
			<td>http://www.canadiantire.ca/en/pdp/armor-coat-bbq-paint-0480648p.html#srp</td>
		</tr>
		<tr>
			<td>Solid green neoprene stoppers (size 0; 1 package of 68)</td>
			<td>Cole-Palmer</td>
			<td>OF-62991-04</td>
			<td>https://www.coleparmer.ca/i/cole-parmer-solid-green-neoprene-stoppers-standard-size-0-68-pk/6299104?searchterm=OF-62991-04</td>
		</tr>
		<tr>
			<td>Spatula, stainless steel</td>
			<td>Fisher Scientific</td>
			<td>14-375-10</td>
			<td>https://www.fishersci.ca/shop/products/fisherbrand-spoonula-lab-spoon/1437510?searchHijack=true&#38;searchTerm=1437510&#38;searchType=RAPID&#38;matchedCatNo=1437510</td>
		</tr>
		<tr>
			<td>7.5 L Pressure Vessel</td>
			<td>Autoclave Engineers</td>
			<td>40A-9104, 9122, 40C-1365, 2376</td>
			<td>minimum internal diameter of 127 mm; equipped with 20.7 MPa (3000 psi) rupture disc assembly; Solenoid&#38; air operated valve on the outlet; http://www.autoclaveengineers.com/products/pressure_vessels/PV_Bolted_Closure/index.html</td>
		</tr>
		<tr>
			<td>Electrodes (set of 2)</td>
			<td>Electo-meters</td>
			<td>Conax EG-375-A-SS-T, 25.4 cm (10&#34;) conductor</td>
			<td>with Teflon sealing glands; https://www.conaxtechnologies.com/wp-content/uploads/2016/03/5001D-80-105-Flanges-and-Accessories.pdf</td>
		</tr>
		<tr>
			<td>Rupture disc</td>
			<td>Oseco</td>
			<td>39859-3-1</td>
			<td>http://www.oseco.com/imgUL/files/STD_0515.pdf</td>
		</tr>
		<tr>
			<td>Universal safety head (rupture disc assembly)</td>
			<td>Autoclave Engineers</td>
			<td>SS-4600-1/2F</td>
			<td>http://www.autoclave.com/products/accessories/universal_safety_heads/index.html</td>
		</tr>
		<tr>
			<td>High-pressure valve (air-operated, fail-open)</td>
			<td>Autoclave Engineers</td>
			<td>1/2&#34; SW8XXX-CM</td>
			<td>http://www.autoclave.com/aefc_pdfs/OM_P1_Manual_Air_Valve.pdf?zoom_highlightsub=air+operated+valve#search=&#34;air operated valve&#34;</td>
		</tr>
		<tr>
			<td>Pressure transducer</td>
			<td>Omega Engineering</td>
			<td>PX176-3KS5V</td>
			<td>Amplified Voltage Output Transducer for Absolute; 0-20.7 Mpa (0-3000 psi) sealed gauge, 91 cm (36&#34;) cable http://www.omega.ca/pptst_eng/PX176.html</td>
		</tr>
		<tr>
			<td>Digital multimeter</td>
			<td>Amazon.com</td>
			<td>Fluke Model 110 Plus</td>
			<td>https://www.amazon.com/Fluke-110-Plus-essential-multimeter/dp/B01JX912I2</td>
		</tr>
		<tr>
			<td>Data acquisition Interface</td>
			<td>IOTECH</td>
			<td>Model Daqlab 2000 with DBK15 acquisition board</td>
			<td>http://www.mccdaq.com/products/daqlab2000s</td>
		</tr>
		<tr>
			<td>Personal Computer with monitor and National Instruments DASYLab Software (V13, basic) installed</td>
			<td>DELL</td>
			<td>CORETMi7 vProTM</td>
			<td>Computer must meet requirements for Dasylab 13: 1GHz + x86 compatible; Windows 7 or 8, 32-bit or 64-bit; 2 GB+ RAM</td>
		</tr>
		<tr>
			<td>oscilloscope</td>
			<td></td>
			<td></td>
			<td>Any storage oscilloscope with 2 input channels (0-10 V), 12k samples per channel and acquisition frequency of 10 ms/sample.</td>
		</tr>
		<tr>
			<td>Precision Shunt Resister</td>
			<td>Canadian Shunt Industries</td>
			<td>LA-20-100</td>
			<td>(20 A, 100 mV) Enclosed in custom box http://www.cshunt.com/pdf/la.pdf</td>
		</tr>
		<tr>
			<td>Constant Current Power Supply</td>
			<td>Agilent</td>
			<td>N6700B Low-Profile MPS Mainframe, 400W; N6754A DC Power Supply with High Speed Test Extensions option</td>
			<td>http://www.keysight.com/en/pd-1125217-pn-N6754A/high-performance-autoranging-dc-power-module-60v-20a-300w?cc=CA&#38;lc=eng</td>
		</tr>
		<tr>
			<td>Inlet valve</td>
			<td>Ottawa Valves and Fittings</td>
			<td>Swagelok SS-43GS4-PT</td>
			<td>https://www.swagelok.com/en/catalog/Product/Detail?part=SS-43GS4</td>
		</tr>
		<tr>
			<td>Full face mask</td>
			<td>Cooper Safety</td>
			<td>3M 7800 series</td>
			<td>http://www.coopersafety.com/product/3m-7800-series-full-face-respirator-1124.aspx</td>
		</tr>
		<tr>
			<td>General purpose cartridges</td>
			<td>Cooper Safety</td>
			<td>3M 60923</td>
			<td>http://www.coopersafety.com/product/3m-60923-organic-vapor-acid-gas-p100-cartridge-1533.aspx?sid=101950</td>
		</tr>
	</tbody>
</table>

minimum burning pressures of water-based emulsion explosives

This manuscript describes a protocol to measure the minimum pressure required for sustained burning of water-based emulsion explosives. Pumping water-based emulsion explosives for blasting applications can be very hazardous, as demonstrated by a number of pump accidents around the globe in the last decades, including some that resulted in fatalities. In Canada, the recognition of this hazard has led to the development of pumping guidelines that were endorsed by both the explosives industry and the Explosive Regulatory Division of the Canadian government. In these guidelines, it was noted that the minimum burning pressures (MBP) measured in a laboratory would provide a good guide to characterize the behaviour of these products in pumping systems. The same guidelines also call for the design of pump systems that prevent, whenever possible, pressures from exceeding the MBP of the product being pumped. At the time of publication of these guidelines, a methodology existed for measuring such MBP values but it had never been validated to measure the MBP of ammonium nitrate water-based emulsions (AWEs). AWEs are now used much more widely than any other water-based explosives and precursors in on-site bulk loading operations.
The Canadian Explosives Research Laboratory (CanmetCERL) has been conducting research over the last ten years to develop a validated testing protocol to measure and interpret representative MBP values for AWEs. The test, as it is performed today, will be described and the critical components will be justified by reference to recent published data. Results of MBP measurements, for a range of AWE products, will be presented. Inclusion of the MBP test in the test standards for the authorization of high explosives in Canada will also be discussed.

Typical raw signals from a test resulting in a fully propagated event (i.e. &#34;go&#34;) are shown in Figure 6. The ignition current (blue curve) is seen to come on at t0 = 0 and to stay on until the NiCr wire burns at tb = 19.1 s. The computed average ignition current (i.e. average of all data points between t0 and tb is Ihw = 10.59 A. On the pressure record (red curve), the first sign...

Watch this Scientific Journal Video about Minimum Burning Pressures of Water-based Emulsion Explosives at JoVE.com

Minimum Burning Pressures of Water-based Emulsion Explosives

We present an apparatus based on hot-wire ignition in a pressurized enclosure and an associated methodology to measure the minimum pressure required to induce sustained combustion in water-based emulsion explosives. This method improves product characterization to allow one to use them more safely during pumping and mixing operations.

This manuscript describes a protocol to measure the minimum pressure required for sustained burning of water-based emulsion explosives. Pumping ...

The overall goal of this procedure is to measure the minimum pressure required for self sustained combustion in water-based emulsion explosives which is called the minimum burning pressure. The minimum burning pressure is a parameter that can guide the estimation of safe operating pressures for the manufacturing, handling and pumping of emulsion explosives. The main advantage of this technique is that it requires only 20 to 30 grams of explosives.It can therefore be performed in a laboratory environment. The installation of MBP facilities in other laboratories would facilitate inter-laboratory MBP testing, which could lead to the establishment of standard reference material for performance validation. To begin preparing the test cell components, cut an 85 millimeter length of Nichrome wire.Use needle nosed pliers to bend each end of the wire into a small loop. Use uninsulated butt end splice connectors and a crimping tool to splice the ends of the Nichrome wire into 50 centimeter lengths of number 14 American wire gauge solid core bared copper wire. Prepare 10 to 15 ignition wire assemblies in this way.Verify that the resistance measured across each assembly is less than 0.5 Ohms. Next, obtain 10 to 15 small cylindrical steel pipes, each with a three millimeter wide slit machined along the long axis. Paint the interior of each cell with two coats of high temperature, non-conductive paint.For each cell, cut off the narrow ends of two number zero neoprene stoppers to obtain 16 millimeter long stoppers. Punch a hole six millimeters in diameter through the center of each stopper. Verify that the holes are wide enough to accommodate the copper wire and splice connectors.Then, insert an ignition wire assembly into the dried painted cell through the three millimeter wide slit. Thread a neoprene stopper onto each copper wire. Carefully insert the stoppers into each end of the cell without compressing or twisting the ignition wire.Pull the ignition wire taut. Bend the copper wires by about 90 degrees at the ends of the stoppers to fix the ignition wire in place. Repeat this process to assemble the remaining test cells.To begin preparing the cell for the test carefully introduce the emulsion into a test cell through the three millimeter wide slit. Once the cell is full, remove any air pockets by tamping down the sample with a small spatula and tapping the cell against a hard surface. Continue filling the cell and settling the sample in this way until no more sample can be packed into the cell.Then, place the loaded cell horizontally in a remotely operated pressure vessel with the slit facing upwards. Connect the copper wires to the electrodes in the pressure vessel, ensuring that the wires do not contact the body of the vessel. Use a multimeter to verify that there is no electrical contact between each electrode and the body of the pressure vessel.Then, close and seal the vessel. In a protected instrument room, verify that the data acquisition card is connected to the pressure transducer and the voltage signal across a high precision shunt resistor. Confirm that the shunt resistor is connected in series with a constant current source and that this series is connected to the pressure vessel electrodes.Then, start the data acquisition software. Remotely close the pressure vessel outlet valve and begin pressurizing the vessel with argon. Once the vessel has reached the starting test pressure, close the inlet valve.Monitor the system for five to ten minutes to verify that there are no significant leaks. Once the vessel has passed the leak check, open the inlet valve to adjust the pressure to the desired initial value and then close the valve. Flow a constant current of 10.5 amps through the ignition wire until the sample ignites, melting the ignition wire and halting the current flow.Turn off the current power supply once ignition has occurred and the pressure starts increasing. During the test, the pressure may reach one or two minima or maxima before continuously decreasing. Wait ten minutes after the start of the continuous pressure decrease before performing additional manipulations.At the completion of the test, open the outlet valve to vent the combustion gasses to exhaust. Set the argon regulator to about 50 psi and open the inlet valve. Allow a gentle flow of argon to circulate for two to three minutes to purge the vessel of toxic gasses, then allow the vessel to return to ambient pressure.Lock out the constant current supply by disconnecting the AC power or with a lockout key before returning to the pressure vessel room. Put on a face mask with appropriate general purpose cartridges before opening the pressure vessel. Open the vessel and disconnect the copper wires from the electrodes.Visually inspect the cell and pressure vessel to determine the extent to which the sample burned. Document the results in writing and with photographs. If the combustion front reached the test cell walls and little to no sample remains on the neoprene stoppers, the result is considered a go and the pressures should be decreased for the next test.Otherwise, the result is considered a no-go and the pressure should be increased for the next test. Following the visual inspection, perform additional analyses using the recorded current and pressure data. Repeat the test with additional samples while gradually decreasing the pressure increments or decrements to precisely determine the MBP.Clean the pressure vessel after each test. At 17.3 seconds into the test shown here the pressure began increasing from an initial average of 4.924 mega pascals. The dropping current corresponding to the burning of the ignition wire occurred at 19.1 seconds.The maximum pressure of 6.095 mega pascals occurred at 33.7 seconds. Five identical AWEs with varying water contents were among the samples tested with this method. The MBPs for these emulsions were observed to increase with increasing water content.Greater variance was observed in the MBP data for AWEs with lower water contents. This may have been caused by non-uniformity in the samples as their comparatively higher crystallization temperatures may make these samples more prone to crystallization when manipulated. The MBP test described here has been added to the requirements for the authorization of high explosives in Canada by the Explosive Regulatory Division of Natural Resources Canada.Once mastered, a full MBP measurement consisting of ten to twelve experiments can be completed in two days if it's performed properly. While attempting this procedure, remember to always release vessel pressure and lock out the current source before returning to the pressure vessel room. Electrocution and projectiles from sudden decompression are your greatest hazards.

minimum-burning-pressures-of-water-based-emulsion-explosives

Research

JoVE Journal

Chemistry

Determination of the Gas-phase Acidities of Oligopeptides

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

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

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

Synthesis of Indoxyl-glycosides for Detection of Glycosidase Activities

Indoxyl glycosides proved to be valuable and versatile tools for monitoring glycosidase activities. Indoxyls are released by enzymatic hydrolysis and are rapidly oxidized, for example by atmospheric oxygen, to indigo type dyes. This reaction enables fast and easy screening in vivo without isolation or purification of enzymes, as well as rapid tests on agar plates or in solution (e.g., blue-white screening, micro-wells) and is used in biochemistry, histochemistry, bacteriology and molecular biology. Unfortunately the synthesis of such substrates proved to be difficult, due to various side reactions and the low reactivity of the indoxyl hydroxyl function. Especially for glucose type structures low yields were observed. Our novel approach employs indoxylic acid ester as key intermediates. Indoxylic acid esters with varied substitution patterns were prepared on scalable pathways. Phase transfer glycosylations with those acceptors and peracetylated glycosyl halides can be performed under common conditions in high yields. Ester cleavage and subsequent mild silver mediated glycosylation yields the peracetylated indoxyl glycosides in high yields. Finally deprotection is performed according to Zempl&#233;n.

Indoxyl glycosides are well-established and widely used tools for enzyme screening and enzyme activity monitoring. Especially for glucose type structures previous syntheses proved to be challenging and low yielding. Our novel approach employs indoxylic acid esters as precious intermediates to yield a considerable number of indoxyl glycosides in good yields.

Indoxyl glycosides proved to be valuable and versatile tools for monitoring glycosidase activities. Indoxyls are released by enzymatic hydrolysis and are ...

Visualization of Ambient Mass Spectrometry with the Use of Schlieren Photography

This manuscript outlines how to visualize mass spectrometry ambient ionization sources using schlieren photography. In order to properly optimize the mass spectrometer, it is necessary to characterize and understand the physical principles of the source. Most commercial ambient ionization sources utilize jets of nitrogen, helium, or atmospheric air to facilitate the ionization of the analyte. As a consequence, schlieren photography can be used to visualize the gas streams by exploiting the differences in refractive index between the streams and ambient air for visualization in real time. The basic setup requires a camera, mirror, flashlight, and razor blade. When properly configured, a real time image of the source is observed by watching its reflection. This allows for insight into the mechanism of action in the source, and pathways to its optimization can be elucidated. Light is shed on an otherwise invisible situation.

This paper presents a protocol for the visualization of gaseous streams of an ambient ionization source using schlieren photography and mass spectrometry.

This manuscript outlines how to visualize mass spectrometry ambient ionization sources using schlieren photography. In order to properly optimize the mass ...

Preparation of Hollow Polystyrene Particles and Microcapsules by Radical Polymerization of Janus Droplets Consisting of Hydrocarbon and Fluorocarbon Oils

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) and fluorocarbon oil (perfluoro-n-octane, PFO) in aqueous surfactant (sodium dodecylsulfate, SDS) solutions. Since fluorocarbon oils are immiscible with hydrocarbon oils, the two oils are separated. Emulsions are prepared by stirring styrene/PFO/aqueous SDS solution mixtures at 80 &#176;C. The type of emulsions and the morphology of droplets in the emulsions are observed by light microscope and scanning confocal fluorescence microscope. It is found that oil droplets with Janus-type morphologies consisting of mutually immiscible styrene and PFO are formed in aqueous SDS solutions. Polystyrene particles are fabricated by radical polymerization of the ternary mixtures of styrene/PFO/aqueous SDS solution at 80 &#176;C. The morphologies of the polystyrene are confirmed by scanning electron microscopy and scanning transmission electron microscopy observations. These observations show the preparation of hollow polystyrene particles with a single hole on the surface. To our knowledge, this method is a novel strategy using the immiscibility of hydrocarbon and fluorocarbon oils. The hollow particles can also be applied to the preparation of microcapsules.

A protocol for the fabrication of hollow polymer particles and microcapsules by radical polymerization using emulsions consisting of styrene, perfluoro-n-octane, and aqueous SDS (sodium dodecylsulfate) solution is presented.

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) ...

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F&#8722;

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound electrons with neutral molecules/atoms. State-of-the-art in vacuo anion generation techniques allow application to a broad range of atomic, molecular, and cluster anion systems. These are separated and selected using time-of-flight mass spectrometry. Electrons are removed by linearly polarized photons (photo detachment) using table-top laser sources which provide ready access to excitation energies from the infra-red to the near ultraviolet. Detecting the photoelectrons with a velocity mapped imaging lens and position sensitive detector means that, in principle, every photoelectron reaches the detector and the detection efficiency is uniform for all kinetic energies. Photoelectron spectra extracted from the images via mathematical reconstruction using an inverse Abel transformation reveal details of the anion internal energy state distribution and the resultant neutral energy states. At low electron kinetic energy, typical resolution is sufficient to reveal energy level differences on the order of a few millielectron-volts, i.e., different vibrational levels for molecular species or spin-orbit splitting in atoms. Photoelectron angular distributions extracted from the inverse Abel transformation represent the signatures of the bound electron orbital, allowing more detailed probing of electronic structure. The spectra and angular distributions also encode details of the interactions between the outgoing electron and the residual neutral species subsequent to excitation. The technique is illustrated by the application to an atomic anion (F&#8722;), but it can also be applied to the measurement of molecular anion spectroscopy, the study of low lying anion resonances (as an alternative to scattering experiments) and femtosecond (fs) time resolved studies of the dynamic evolution of anions.

Here, we present a protocol for photoelectron imaging of anionic species. Anions generated in vacuo and separated by mass spectrometry are probed using velocity mapped photoelectron imaging, providing details of anion and neutral energy levels, anion and neutral structure and the nature of the anion electronic state.

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound ...

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for specialized equipment to achieve modest pressures, and can even be used to achieve higher pressures in more specialized equipment and sturdier reaction vessels. At the end of the reaction, the vials can be easily depressurized by opening at room temperature. In the present example CO2 serves as both a putative directing group as well as a way to passivate amine substrates, thereby preventing oxidation during the organometallic reaction. In addition to being easily added, the directing group is also removed under vacuum, obviating the need for extensive purification to remove the directing group. This strategy allows the facile &#947;-C(sp3)-H arylation of aliphatic amines and has the potential to be applied to a variety of other amine-based reactions.

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Here we present a protocol for performing reactions in simple reaction vessels under low-to-moderate pressures of CO2. The reactions can be performed in a variety of vessels simply by administering the carbon dioxide in the form of dry ice, without the need for costly or elaborate equipment or set-ups.

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for ...

Enzymatic Synthesis of Epoxidized Metabolites of Docosahexaenoic, Eicosapentaenoic, and Arachidonic Acids

The epoxidized metabolites of various polyunsaturated fatty acids (PUFAs), termed epoxy fatty acids, have a wide range of roles in human physiology. These metabolites are produced endogenously by the cytochrome P450 class of enzymes. Because of their diverse and potent biological effects, there is considerable interest in studying these metabolites. Determining the unique roles of these metabolites in the body is a difficult task, as the epoxy fatty acids must first be obtained in significant amounts and with high purity. Obtaining compounds from natural sources is often labor intensive, and soluble epoxide hydrolases (sEH) rapidly hydrolyze the metabolites. On the other hand, obtaining these metabolites via chemical reactions is very inefficient, due to the difficulty of obtaining pure regioisomers and enantiomers, low yields, and extensive (and expensive) purification. Here, we present an efficient enzymatic synthesis of 19(S),20(R)- and 16(S),17(R)-epoxydocosapentaenoic acids (EDPs) from DHA via epoxidation with BM3, a bacterial CYP450 enzyme isolated originally from Bacillus megaterium (that is readily expressed in Escherichia coli). Characterization and determination of purity is performed with nuclear magnetic resonance spectroscopy (NMR), high-performance liquid chromatography (HPLC), and mass spectrometry (MS). This procedure illustrates the benefits of enzymatic synthesis of PUFA epoxy metabolites, and is applicable to the epoxidation of other fatty acids, including arachidonic acid (AA) and eicosapentaenoic acid (EPA) to produce the analogous epoxyeicosatrienoic acids (EETs) and epoxyeicosatetraenoic acids (EEQs), respectively.

We present a method useful for large-scale enzymatic synthesis and purification of specific enantiomers and regioisomers of epoxides of arachidonic acid (AA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) with the use of a bacterial cytochrome P450 enzyme (BM3).

The epoxidized metabolites of various polyunsaturated fatty acids (PUFAs), termed epoxy fatty acids, have a wide range of roles in human physiology. These ...

Tuning the Acidity of Pt/ CNTs Catalysts for Hydrodeoxygenation of Diphenyl Ether

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid nanosheets, a series of Pt/xHMNO6/CNTs with different solid acid compositions (x = 5, 20 wt%; M = Nb, Ta; N = Mo, W) have been prepared by carbon nanotube pretreatment, protonic exchange, solid acid exfoliation, aggregation and finally Pt particles impregnation. The Pt/xHMNO6/CNTs are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and NH3-temperature programmed desorption. The study revealed that HNbWO6 nanosheets were attached on CNTs, with some edges of the nanosheets being bent in shape. The acid strength of the supported Pt catalysts increases in the following order: Pt/CNTs &#60; Pt/5HNbWO6/CNTs &#60; Pt/20HNbMoO6/CNTs &#60; Pt/20HNbWO6/CNTs &#60; Pt/20HTaWO6/CNTs. In addition, the catalytic hydroconversion of lignin-derived model compound: diphenyl ether using the synthesized Pt/20HNbWO6 catalyst has been investigated.

A protocol for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs is presented.

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid ...

Comparison of Two Different Synthesis Methods of Single Crystals of Superconducting Uranium Ditelluride

Single crystal specimens of the actinide compound uranium ditelluride, UTe2, are of great importance to the study and characterization of its dramatic unconventional superconductivity, believed to entail spin-triplet electron pairing. A variety in the superconducting properties of UTe2 reported in the literature indicates that discrepancies between synthesis methods yield crystals with different superconducting properties, including the absence of superconductivity entirely. This protocol describes a process to synthesize crystals that exhibit superconductivity via chemical vapor transport, which has consistently exhibited a superconducting critical temperature of 1.6 K and a double transition indicative of a multi-component order parameter. This is compared to a second protocol that is used to synthesize crystals via the molten metal flux growth technique, which produces samples that are not bulk superconductors. Differences in the crystal properties are revealed through a comparison of structural, chemical, and electronic property measurements, showing that the most dramatic disparity occurs in the low-temperature electrical resistance of the samples.

Here, we present a protocol to synthesize two types of UTe2 crystals: those exhibiting robust superconductivity, via chemical vapor transport synthesis, and those lacking superconductivity, via molten metal flux synthesis.

Single crystal specimens of the actinide compound uranium ditelluride, UTe2, are of great importance to the study and characterization of its dramatic ...

Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch

Photoswitching organic molecules that undergo light-driven structural transformations are key components to construct adaptive molecular systems, and they are utilized in a wide variety of applications. In most studies employing photoswitches, several important photophysical properties such as maximum wavelengths of absorption and emission, molar attenuation coefficient, fluorescence lifetime, and photoisomerization quantum yield are carefully determined to investigate their electronic states and transition processes. However, measurement of the photoisomerization quantum yield, the efficiency of photoisomerization with respect to the absorbed photons, in a typical laboratory setting is often complicated and prone to error because it requires the implementation of rigorous spectroscopic measurements and calculations based on an appropriate integration method. This article introduces a set of procedures to measure the photoisomerization quantum yield of a bistable photoswitch using a photochromic hydrazone. We anticipate that this article will be a useful guide for the investigation of bistable photoswitches that are being increasingly developed.

Photoisomerization quantum yield is a fundamental photophysical property that should be accurately determined in the investigation of newly developed photoswitches. Here, we describe a set of procedures to measure the photoisomerization quantum yield of a photochromic hydrazone as a model bistable photoswitch.

Photoswitching organic molecules that undergo light-driven structural transformations are key components to construct adaptive molecular systems, and they ...