Name: an inverse analysis approach to the characterization of chemical transport in paints
Uploaded: 2014-08-29T15:00:00.000+00:00
Duration: 8 min 42 s
Description: Watch this Scientific Journal Video about An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints at JoVE.com

The authors thank Dr. Wes Gordon (ECBC) for support in instrument design. This work represents the cumulative results from two research programs funded by Eric Lowenstein and Michael Roberts (Defense Threat Reduction Agency) under program CA08MSB317. The technical reports cited herein can be obtained at <a href="http://www.dtic.mil">http://www.dtic.mil</a>.

1. Condition Paint Substrates to the Desired Environment
<ol>
	<li>Preset the environmental chamber for substrate conditioning to the specified temperature and relative humidity (20 &#176;C, 50%). Ensure that the substrate conditions are consistently maintained since both temperature and water content can significantly influence absorption rates into materials.</li>
	<li>Coat 0.32 cm thick, 5.08 cm radius stainless steel discs with a surface area of 20.25 cm2 with a layer of paint (MIL-DTL-53039, a solvent-dispersible (SD) aliphatic polyurethane coating system6) with a total coating thickness (primer and top coat) of approximately 100 &#181;m. Place the substrates (with desired number of replicates) on stainless steel trays with the test surface to be exposed to a chemical agent facing upwards.</li>
	<li>Cover the substrates with Petri dishes. Place the trays containing the test substrates into the environmental chamber for at least 60 min but ideally O/N, if possible.</li>
</ol>
2. Contamination of Preconditioned Substrates
<ol>
	<li>Don personal protective equipment such as lab coat, safety glasses, and gloves.</li>
	<li>CAUTION: Obtain the chemical contaminants from cold storage and allow primary container vial to equilibrate to RT. The chemicals used in this protocol are Chemical Agent Standard Analytical Reference Material (CASARM, 98.0% purity) grade HD and CASARM (89.0% high purity) grade VX (both liquid phase). Obtain purity information from either nuclear magnetic resonance or gas chromatography/mass spectroscopy analyses and maintain on file. 
	NOTE: CAUTION: The handling of chemical warfare agents should only be performed by trained personnel at an approved facility using applicable safety, security, and surety precautions.</li>
	<li>CAUTION: Fit the agent delivery tool with a pipette tip and configure the tool to deliver a droplet of agent (e.g., 1 &#181;l). Uncap the contaminant vial, and place the cap on the hood surface, threads facing up. Pick up the pipette, and slowly lower the tip into the contaminant solution. Load the agent delivery tool with agent in accordance with the manufacturer&#8217;s directions. Gently place the loaded pipette onto the hood working surface, and recap the contaminant vial.</li>
	<li>CAUTION: Contaminate the test substrates.
	<ol>
		<li>Remove the trays containing the test substrates from the environmental chamber.</li>
		<li>Remove the Petri dishes from the test substrates, and set on the hood surface. Digitally photograph each test substrate to record the appearance of each substrate before contamination.</li>
		<li>Pick up the loaded pipette and deliver a single droplet (e.g., 1 &#181;l) of agent onto the first test substrate. Cover the contaminated material with a polystyrene Petri dish to minimize evaporation while contaminating additional substrates. Repeat for each substrate; reload the pipette tip (Step 2.3) as necessary. 
		NOTE: Collect pipette confirmation samples before and after dosing of substrates for analysis via chromatography to confirm contaminant mass delivery.</li>
		<li>Remove the Petri dishes from the test substrates and set on the hood surface. Digitally photograph each test substrate to record the initial contaminant-material interactions.</li>
		<li>Cover the test substrates with the Petri dishes.</li>
		<li>Place the tray of substrates back into the environmental chamber.</li>
	</ol>
	</li>
</ol>
3. Contaminant-material Interaction Aging Period
<ol>
	<li>Prior to aging the samples, vent the stainless steel high vacuum experimental chamber to prepare it for use in Section 4.</li>
	<li>Allow the contaminated substrates to age in the environmental chamber for the specified duration, which can be varied based on the chemical-material-environment interaction dynamics (e.g., 60 min).</li>
	<li>Remove substrates from the environmental chamber and place on the working surface of the hood. Remove the Petri dishes from the test substrates and digitally photograph each substrate to record the post-aging contaminant-material interactions.</li>
	<li>Double-contain the test samples (e.g., multiple airtight containers) and transfer to the working hood with high vacuum chamber.</li>
</ol>
4. High Vacuum Vapor Emission Chamber Measurement
The high vacuum chamber is a small volume vessel pumped by a turbo molecular drag pump and a diaphragm backing pump (Figure 2). A quadrupole mass spectrometer is mounted on a port that directly faces a temperature-controlled substrate holder and is used to measure real-time gas evolution from contaminated substrates under high vacuum conditions. Full details on the vacuum chamber specifications and materials are included in reference 4.
<ol>
	<li>Ensure that the chamber is properly vented.</li>
	<li>CAUTION: Unpackage the samples prepared in Section 3, and remove Petri dish from the test substrates. Place one test substrate into each temperature-controlled substrate holder using stainless steel tweezers.</li>
	<li>Seal the vacuum chamber and begin the pump down sequence. Perform this step such that the chamber is vacuum sealed at the specified age time (e.g., 60 min) in relation to when the substrate was contaminated.</li>
	<li>Begin recording selected mass fragment channels as a function of time (direct measure of mass flux) identified with specific mass per unit charge values (m/z). Measure specific background gas species in addition to the primary mass fragments from the molecules of interest (VX: m/z = 114; HD: m/z = 109) in real time at &#60;0.25 Hz until the contaminant partial pressure drops below detection limits of the mass spectrometer (10&#8722;8 Pa).</li>
	<li>Collect the emission curves for the duration of the emission of contaminant from the substrate.</li>
	<li>Stop recording emission curves with the mass spectrometer once the contaminant mass flux has decreased to the chamber pressure baseline.</li>
	<li>Vent the high vacuum chamber to atmospheric pressure.</li>
</ol>
5. Post-treatment Evaluation for Total Remaining Contaminant
<ol>
	<li>Open the high vacuum vapor emission chamber (HVVEC) instrument and remove the substrate from the chamber using stainless steel tweezers.</li>
	<li>Place the substrate into a glass extraction jar and add 20 ml of extraction solvent to the jar (e.g., isopropyl alcohol: VX; chloroform: HD). Cap the jar and swirl the jar three times. Leave the substrate in the extraction solvent for 60 min.</li>
	<li>Swirl the jar three times again and then uncap the jar. Using a clean, disposable, glass pipette, transfer approximately 1 to 2 ml of extraction solvent into an analytical vial for analysis via gas or liquid chromatography7 to measure the contaminant mass retained by the substrates.</li>
</ol>
6. Data Analysis and Modeling
<ol>
	<li>Convert raw mass spectrometry data (partial pressure derived from measured ion current) to mass flux from the substrate. Use a combination of the Hertz-Knudsen formula for converting partial pressure of detected gas species to incident vapor flux at the detector and include a scaling factor that accounts for the contaminated area on the substrate from the original contamination event.</li>
	<li>Use inverse methods (e.g., Levenberg-Marquardt algorithm) to determine the saturation concentration and diffusion constant values (key mass transport parameters) for the contaminant transport through the paint coating. Compare the experimentally determined vapor flux to a predicted vapor flux (an analytical solution to Fick&#8217;s second law with appropriate boundary conditions applied (see equation 4 from reference 4)).</li>
	<li>Use the mass transport parameters to predict the concentration profiles for the contaminant-material system.</li>
</ol>

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	<li>Willis, M. P., Mantooth, B. A., Lalain, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+Methodology+for+the+Estimation+of+Chemical+Warfare+Agent+Mass+Transport+Dynamics,+Part+II:+Absorption.">Novel Methodology for the Estimation of Chemical Warfare Agent Mass Transport Dynamics, Part II: Absorption.</a> J. Phys. Chem. C. 116, 546-554 (2011).</li><li>Felder, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimation+of+Gas+Transport-Coefficients+from+Differential+Permeation,+Integral+Permeation,+and+Sorption+Rate+Data.">Estimation of Gas Transport-Coefficients from Differential Permeation, Integral Permeation, and Sorption Rate Data.</a> J. Membr. 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Hazard Mater. 260, 907-913 (2013).</li><li>Lalain, T., Mantooth, B., Shue, M., Pusey, S., Wylie, 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> The Chemical Contaminant and Decontaminant Test Methodology Source Document. Second Edition. Report No. ECBC-TR-980. , (2011).</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> MIL-DTL-53039B: Coating Aliphatic Polyurethane, Single Component, Chemical Agent Resistant. , (2005).</li><li>Shue, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Low-Level Analytical Methodology Updates to Support Decontaminant Performance Evaluations. Report No. ECBC-TR-883. , (2011).</li><li>Schwope, A. D., Klein, J. M., Sidman, K. R., Reid, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sorption-Desorption+Phenomena+of+Chemicals+from+Polymer+(Paint)+Films.">Sorption-Desorption Phenomena of Chemicals from Polymer (Paint) Films.</a> J. Hazard. Mater. 13, 353-367 (1986).</li><li>Li, F., Niu, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+Volatile+Organic+Compounds+Indoors+-+Development+of+an+Integrated+Mass-Transfer-Based+Model+and+Its+Application.">Control of Volatile Organic Compounds Indoors - Development of an Integrated Mass-Transfer-Based Model and Its Application.</a> Atmos. 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The authors have nothing to disclose.

Mass transport parameters for HD and VX in the paint were determined via the numerical inverse analysis of vapor emission data. With calculated parameters, it was possible to then produce time-dependent concentration gradient maps for contaminant distribution in the paint coating. The inverse analysis results demonstrated that the solubility of HD in the SD paint was higher than VX, but the diffusivity was approximately 5x lower. The results suggest that the HD contamination was highly concentrated at the surface of t...

The mass transport mechanisms associated with contamination of materials by chemical warfare agents are driven by a variety of convolved processes including physical state transitions, chemical interactions between mobile species, and materials interfaces. To develop efficacious decontamination technologies, optimized decontamination procedures, and predictive models, it is vital that the contamination process is well understood, including the transport of contaminants into materials via absorption and the subsequent chemical emission back into the environment. Consequently, it is imperative that approaches are developed that can evaluate subsurface concentration profiles for contaminant-material pairs as a function of environmental conditions. A continuum-scale, physics-based model was developed to predict the concentration distribution of absorbed agent in a contaminated substrate. Experimentally derived mass transport parameters enable the prediction of the vapor emission from the contaminated material post decontamination. An ability to predict the concentration distribution in a material can facilitate the assessment of potential vapor hazards and, in turn, enable accurate diagnoses of toxicological hazards1. This approach allows for an estimation of contaminant-material pair specific mass transport parameters such as diffusivity and saturation concentration that in turn permit modeling for a other scenarios and conditions. In this study, we have treated the liquid phase contamination of solvent-dispersed, polyurethane paint coatings with chemical warfare agents bis(2-chloroethyl) sulfide (distilled mustard, blister agent HD) and O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX), an organophosphate nerve agent.
The developed methodology characterizes gas desorption profiles from contaminated materials, including chemical warfare agents like HD and VX, without many of the restrictions that hamper other approaches2,3. Time-resolved mass spectrometry measurements of contaminant evolution from contaminated substrates allow for a diffusive transport model with inverse analysis to calculate mass transport parameters for the contaminant in the material, including the absorbed concentration profile for the contaminant starting from the original permeation event. With the establishment of a predictive capability for delineating concentration profiles of contaminants in materials as a function of environmental conditions comes the ability to assess toxicological hazards and ultimately develop routes for efficacious decontamination. 
In this paper, the details associated with sample preparation are presented, including work with chemical warfare agent contaminants, as well as experimental data collection from contaminated materials and subsequent modeling4. Experimental runs were conducted as described in the chemical contaminant and decontaminant source document5 and will be discussed in the next section. A flow chart for sample preparation and analysis steps in included in Figure 1.

<table><tbody><tr><td>Stainless Steel Tray</td><td>McMaster Carr</td><td>4189T1</td><td>13-5/8&quot; L x 9-3/4&quot; W, http://www.mcmaster.com/#stainless-steel-trays/=p8dcgp</td></tr><tr><td>MIL-DTL-53039 solvent-dispersible aliphatic polyurethane coating system</td><td></td><td></td><td>Substrates supplied by internal source</td></tr><tr><td>Environmental Chamber</td><td></td><td></td><td>Custom Design. Full details on vacuum chamber specifications and materials included in reference 4.</td></tr><tr><td>bis(2-chloroethyl) sulfide</td><td>CASARM</td><td></td><td>TOXIC</td></tr><tr><td>&lt;em&gt;O&lt;/em&gt;-ethyl &lt;em&gt;S&lt;/em&gt;-[2-(diisopropylamino)ethyl] methylphosphonothioate</td><td>CASARM</td><td></td><td>TOXIC</td></tr><tr><td>Pipetter</td><td>Fisher Scientific</td><td>22260201</td><td>Range of 1.0 &amp;micro;l to 10 ml</td></tr><tr><td>Pipetter Tips</td><td>Fisher Scientific</td><td>13-683-709</td><td>0.1 ml Volume</td></tr><tr><td>Stainless Steel High Vacuum Experimental Chamber</td><td></td><td></td><td>Custom Design</td></tr><tr><td>Quadrupole Mass Spectrometer</td><td>ExTorr</td><td>RGA300</td><td></td></tr><tr><td>Stainless Steel Tweezers</td><td>McMaster Carr</td><td>5516A15</td><td>Any stainless steel tweezers are appropriate.</td></tr><tr><td>Glass Extraction Jar</td><td>Scientific Specialties</td><td>170808</td><td>Jar fits a ~5 cm diameter substrate. Different glass jars with teflon lined lids are appropriate for different sized substrates.</td></tr><tr><td>Chloroform</td><td>Sigma-Aldrich</td><td>650498</td><td>HARMFUL. The extraction solvent for HD may change depending on the analytical method.</td></tr><tr><td>Isopropanol</td><td>Sigma-Aldrich</td><td>650447</td><td>HARMFUL. The extraction solvent for VX may change depending on the analytical method.</td></tr><tr><td>Pasteur Pipette</td><td>VWR</td><td>14673-010</td><td>size = 5 3/4&quot;</td></tr></tbody></table>

an inverse analysis approach to the characterization of chemical transport in paints

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals (such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX.

The top panel of Figure 3 displays examples of the calculated mass flux of VX and HD from SD-painted substrates based on time-resolved mass spectrometry for the main mass fragments of VX and HD (mass-to-charge ratio, m/z = 114 and 109, respectively). A quadrupole mass spectrometer has three main components: an ionizer, a mass analyzer or filter, and a charge detector. Gas species are ionized via electron impact ionization (hot filament style electron source), and the produced ions are i...

Watch this Scientific Journal Video about An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints at JoVE.com

An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints

In this paper, a procedure for quantifying the mass transport parameters of chemicals in various materials is presented. This process involves employing an inverse-analysis based diffusion model to vapor emission profiles recorded by real-time, mass spectrometry in high vacuum.

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in ...

an-inverse-analysis-approach-to-characterization-chemical-transport

Universidad San Sebastian

Research

JoVE Journal

Chemistry

8.3K Views.  U.S. Army Edgewood Chemical Biological Center. In this paper, a procedure for quantifying the mass transport parameters of chemicals in various materials is presented. This process involves employing an inverse-analysis based diffusion model to vapor emission profiles recorded by real-time, mass spectrometry in high vacuum.

Video: An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints

A Whole Cell Bioreporter Approach to Assess Transport and Bioavailability of Organic Contaminants in Water Unsaturated Systems

Bioavailability of contaminants is a prerequisite for their effective biodegradation in soil. The average bulk concentration of a contaminant, however, is not an appropriate measure for its availability; bioavailability rather depends on the dynamic interplay of potential mass transfer (flux) of a compound to a microbial cell and the capacity of the latter to degrade the compound. In water-unsaturated parts of the soil, mycelia have been shown to overcome bioavailability limitations by actively transporting and mobilizing organic compounds over the range of centimeters. Whereas the extent of mycelia-based transport can be quantified easily by chemical means, verification of the contaminant-bioavailability to bacterial cells requires a biological method. Addressing this constraint, we chose the PAH fluorene (FLU) as a model compound and developed a water unsaturated model microcosm linking a spatially separated FLU point source and the FLU degrading bioreporter bacterium Burkholderia sartisoli RP037-mChe by a mycelial network of Pythium ultimum. Since the bioreporter expresses eGFP in response of the PAH flux to the cell, bacterial FLU exposure and degradation could be monitored directly in the microcosms via confocal laser scanning microscopy (CLSM). CLSM and image analyses revealed a significant increase of the eGFP expression in the presence of P. ultimum compared to controls without mycelia or FLU thus indicating FLU bioavailability to bacteria after mycelia-mediated transport. CLSM results were supported by chemical analyses in identical microcosms. The developed microcosm proved suitable to investigate contaminant bioavailability and to concomitantly visualize the involved bacteria-mycelial interactions.

A whole cell bioreporter assay with Burkholderia sartisoli RP037-mChe was developed to detect fractions of an organic contaminant (i.e., fluorene) available for bacterial degradation after active transport by mycelia bridging air-filled pores in a water unsaturated model system.

Bioavailability of contaminants is a prerequisite for their effective biodegradation in soil. The average bulk concentration of a contaminant, however, is ...

Environment

Diffuse Reflectance Infrared Spectroscopic Identification of Dispersant/Particle Bonding Mechanisms in Functional Inks

In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers. A typical inkjet ink is a colloidal dispersion containing approximately ten components including solvent, the nano to micron scale particles which will comprise the printed layer, polymeric dispersants to stabilize the particles, and polymers to tune layer strength, surface tension and viscosity. To rationally and efficiently formulate such an ink, it is crucial to know how the components interact. Specifically, which polymers bond to the particle surfaces and how are they attached? Answering this question requires an experimental procedure that discriminates between polymer adsorbed on the particles and free polymer. Further, the method must provide details about how the functional groups of the polymer interact with the particle. In this protocol, we show how to employ centrifugation to separate particles with adsorbed polymer from the rest of the ink, prepare the separated samples for spectroscopic measurement, and use Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) for accurate determination of dispersant/particle bonding mechanisms. A significant advantage of this methodology is that it provides high level mechanistic detail using only simple, commonly available laboratory equipment. This makes crucial data available to almost any formulation laboratory. The method is most useful for inks composed of metal, ceramic, and metal oxide particles in the range of 100 nm or greater. Because of the density and particle size of these inks, they are readily separable with centrifugation. Further, the spectroscopic signatures of such particles are easy to distinguish from absorbed polymer. The primary limitation of this technique is that the spectroscopy is performed ex-situ on the separated and dried particles as opposed to the particles in dispersion. However, results from attenuated total reflectance spectra of the wet separated particles provide evidence for the validity of the DRIFTS measurement.

Formulation of stable, functional inks is critical to expanding the applications of additive manufacturing. In turn, knowledge of the mechanisms of dispersant/particle bonding is required for effective ink formulation. Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) is presented as a simple, inexpensive way to gain insight into these mechanisms.

In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers.  A typical inkjet ink is a colloidal ...

Analyzing the Photo-oxidation of 2-propanol at Indoor Air Level Concentrations Using Field Asymmetric Ion Mobility Spectrometry

We demonstrate a versatile protocol to be used for determining the effectiveness of photocatalysts in degrading indoor air concentration (ppb) volatile organic carbons (VOCs), illustrating this with a titanium dioxide based catalyst, and the VOC 2-propanol. The protocol takes advantage of field asymmetric ion mobility spectroscopy (FAIMS), an analysis tool that is capable of continuously identifying and monitoring the concentration of VOCs such as 2-propanol and acetone at the ppb level. The continuous nature of FAIMS allows detailed kinetic analysis, and long-term reactions, offering a significant advantage over gas chromatography, a batch process traditionally used in air purification characterization. The use of FAIMS in photocatalytic air purification has only recently been used for the first time, and with the protocol illustrated here, the flexibility in allowing alternative VOCs and photocatalysts to be tested using comparable protocols offers a unique system to elucidate photocatalytic air purification reactions at low concentrations.

A protocol for determining the effectiveness of photocatalysts in degrading indoor air concentration (ppb) model volatile organic carbons such as 2-propanol is described.

We demonstrate a versatile protocol to be used for determining the effectiveness of photocatalysts in degrading indoor air concentration (ppb) volatile ...

Original Experimental Approach for Assessing Transport Fuel Stability

The study of fuel oxidation stability is an important issue for the development of future fuels. Diesel and kerosene fuel systems have undergone several technological changes to fulfill environmental and economic requirements. These developments have resulted in increasingly severe operating conditions whose suitability for conventional and alternative fuels needs to be addressed. For example, fatty acid methyl esters (FAMEs) introduced as biodiesel are more prone to oxidation and may lead to deposit formation. Although several methods exist to evaluate fuel stability (induction period, peroxides, acids, and insolubles), no technique allows one to monitor the real-time oxidation mechanism and to measure the formation of oxidation intermediates that may lead to deposit formation. In this article, we developed an advanced oxidation procedure (AOP) based on two existing reactors. This procedure allows the simulation of different oxidation conditions and the monitoring of the oxidation progress by the means of macroscopic parameters, such as total acid number (TAN) and advanced analytical methods like gas chromatography coupled to mass spectrometry (GC-MS) and Fourier Transform Infrared - Attenuated Total Reflection (FTIR-ATR). We successfully applied AOP to gain an in-depth understanding of the oxidation kinetics of a model molecule (methyl oleate) and commercial diesel and biodiesel fuels. These developments represent a key strategy for fuel quality monitoring during logistics and on-board utilization.

Oxidation stability of transport fuels has become a concern for future fuel development. This work presents an original methodology developed by IFP Energies Nouvelles for assessing fuel stability using two different reactors. This methodology was successfully applied to gain an in-depth understanding of the oxidation kinetics and pathways of model molecules and commercial fuels.

The study of fuel oxidation stability is an important issue for the development of future fuels. Diesel and kerosene fuel systems have undergone several ...

In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions

To help address production issues in refineries caused by the fouling of process units and lines, we have developed a setup as well as a method to visualize the behavior of petroleum samples under process conditions. The experimental setup relies on a custom-built micro-reactor fitted with a sapphire window at the bottom, which is placed over the objective of an inverted microscope equipped with a cross-polarizer module. Using reflection microscopy enables the visualization of opaque samples, such as petroleum vacuum residues, or asphaltenes. The combination of the sapphire window from the micro-reactor with the cross-polarizer module of the microscope on the light path allows high-contrast imaging of isotropic and anisotropic media. While observations are carried out, the micro-reactor can be heated to the temperature range of cracking reactions (up to 450 &#176;C), can be subjected to H2 pressure relevant to hydroconversion reactions (up to 16 MPa), and can stir the sample by magnetic coupling. 
Observations are typically carried out by taking snapshots of the sample under cross-polarized light at regular time intervals. Image analyses may not only provide information on the temperature, pressure, and reactive conditions yielding phase separation, but may also give an estimate of the evolution of the chemical (absorption/reflection spectra) and physical (refractive index) properties of the sample before the onset of phase separation.

In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions

This article describes a setup and method for the in situ visualization of oil samples under a variety of temperature and pressure conditions that aim to emulate refining and upgrading processes. It is primarily used for studying isotropic and anisotropic media involved in the fouling behavior of petroleum feeds.

To help address production issues in refineries caused by the fouling of process units and lines, we have developed a setup as well as a method to ...

Engineering

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds

Cyclic voltammetry (CV) is a technique used in the analysis of organic compounds. When this technique is combined with electron paramagnetic resonance (EPR) or ultraviolet-visible and near-infrared (UV-Vis-NIR) spectroscopies, we obtain useful information such as electron affinity, ionization potential, band-gap energies, the type of charge carriers, and degradation information that can be used to synthesize stable organic electronic devices. In this study, we present electrochemical and spectroelectrochemical methods to analyze the processes occurring in active layers of an organic device as well as the generated charge carriers.

In this article, we describe electrochemical, electron paramagnetic resonance, and ultraviolet-visible and near-infrared spectroelectrochemical methods to analyze organic compounds for application in organic electronics.

Cyclic voltammetry (CV) is a technique used in the analysis of organic compounds. When this technique is combined with electron paramagnetic resonance ...

Analyzing Mixing Inhomogeneity in a Microfluidic Device by Microscale Schlieren Technique

In this paper, we introduce the use of microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. The microscale schlieren system is constructed from a Hoffman modulation contrast microscope, which provides easy access to the rear focal plane of the objective lens, by removing the slit plate and replacing the modulator with a knife-edge. The working principle of microscale schlieren technique relies on detecting light deflection caused by variation of refractive index1-3. The deflected light either escapes or is obstructed by the knife-edge to produce a bright or a dark band, respectively. If the refractive index of the mixture varies linearly with its composition, the local change in light intensity in the image plane is proportional to the concentration gradient normal to the optical axis. The micro-schlieren image gives a two-dimensional projection of the disturbed light produced by three-dimensional inhomogeneity.
To accomplish quantitative analysis, we describe a calibration procedure that mixes two fluids in a T-microchannel. We carry out a numerical simulation to obtain the concentration gradient in the T-microchannel that correlates closely with the corresponding micro-schlieren image. By comparison, a relationship between the grayscale readouts of the micro-schlieren image and the concentration gradients presented in a microfluidic device is established. Using this relationship, we are able to analyze the mixing inhomogeneity from associate micro-schlieren image and demonstrate the capability of microscale schlieren technique with measurements in a microfluidic oscillator4. For optically transparent fluids, microscale schlieren technique is an attractive diagnostic tool to provide instantaneous full-field information that retains the three-dimensional features of the mixing process.

Herein, we describe a procedure that employs microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. Through calibration, distribution of concentration gradient can be derived from the micro-schlieren image.

In this paper, we introduce the use of microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. The microscale schlieren ...

Bioengineering

Imaging Corrosion at the Metal-Paint Interface Using Time-of-Flight Secondary Ion Mass Spectrometry

Corrosion developed at the paint and aluminum (Al) metal-paint interface of an aluminum alloy is analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS), illustrating that SIMS is a suitable technique to study the chemical distribution at a metal-paint interface. The painted Al alloy coupons are immersed in a salt solution or exposed to air only. SIMS provides chemical mapping and 2D molecular imaging of the interface, allowing direct visualization of the morphology of the corrosion products formed at the metal-paint interface and mapping of the chemical after corrosion occurs. The experimental procedure of this method is presented to provide technical details to facilitate similar research and highlight pitfalls that may be encountered during such experiments.

Time-of-flight secondary ion mass spectrometry is applied to demonstrate the chemical mapping and corrosion morphology at the metal-paint interface of an aluminum alloy after being exposed to a salt solution compared with a specimen exposed to air.

Corrosion developed at the paint and aluminum (Al) metal-paint interface of an aluminum alloy is analyzed using time-of-flight secondary ion mass ...

A Two-Step Pyrolysis-Gas Chromatography Method with Mass Spectrometric Detection for Identification of Tattoo Ink Ingredients and Counterfeit Products

Tattoo inks are complex mixtures of ingredients. Each of them possesses different chemical properties which have to be addressed upon chemical analysis. In this method for two-step pyrolysis online coupled to gas chromatography mass spectrometry (py-GC-MS) volatile compounds are analyzed during a first desorption run. In the second run, the same dried sample is pyrolyzed for analysis of non-volatile compounds such as pigments and polymers. These can be identified by their specific decomposition patterns. Additionally, this method can be used to differentiate original from counterfeit inks. Easy screening methods for data evaluation using the average mass spectra and self-made pyrolysis libraries are applied to speed up substance identification. Using specialized evaluation software for pyrolysis GS-MS data, a fast and reliable comparison of the full chromatogram can be achieved. Since GC-MS is used as separation technique, the method is limited to volatile substances upon desorption and after pyrolysis of the sample. The method can be applied for quick substance screening in market control surveys since it requires no sample preparation steps.

This method for two-step pyrolysis online coupled to gas chromatography with mass spectrometric detection and data evaluation protocol can be used for multi-component analysis of tattoo inks and discrimination of counterfeit products.

Tattoo inks are complex mixtures of ingredients. Each of them possesses different chemical properties which have to be addressed upon chemical analysis. ...

Applying Hyperspectral Reflectance Imaging to Investigate the Palettes and the Techniques of Painters

Reflectance Spectroscopy (RS) and Fiber Optics Reflectance Spectroscopy (FORS) are well-established techniques for the investigation of works of art with particular attention to paintings. Most modern museums put at the disposal of their research groups portable equipment that, together with the intrinsic non-invasiveness of RS and FORS, makes possible the in situ collection of reflectance spectra from the surface of artefacts. The comparison, performed by experts in pigments and painting materials, of the experimental data with databases of reference spectra drives the characterization of the palettes and of the techniques used by the artists. However, this approach requires specific skills and it is time consuming especially if the number of the spectra to be investigated becomes large as is the case of Hyperspectral Reflectance Imaging (HRI) datasets. The HRI experimental setups are multi-dimensional cameras that associate the spectral information, given by the reflectance spectra, with the spatial localization of the spectra over the painted surface. The resulting datasets are 3D-cubes (called hypercubes or data-cubes) where the first two dimensions locate the spectrum over the painting and the third is the spectrum itself (i.e., the reflectance of that point of the painted surface versus the wavelength in the operative range of the detector). The capability of the detector to simultaneously collect a great number of spectra (typically much more than 10,000 for each hypercube) makes the HRI datasets large reservoirs of information and justifies the need for the development of robust and, possibly, automated protocols to analyze the data. After the description of the procedure designed for the data acquisition, we present an analysis method that systematically exploits the potential of the hypercubes. Based on Spectral Angle Mapper (SAM) and on the manipulation of the collected spectra, the algorithm handles and analyzes thousands of spectra while at the same time it supports&#160;the user to unveil the features of the samples under investigation. The power of the approach is illustrated by applying it to Quarto Stato, the iconic masterpiece by Giuseppe Pellizza da Volpedo, held in the Museo del Novecento in Milan (Italy).

Hyperspectral Reflectance Imaging hypercubes include remarkable information into a large amount of data. Therefore, the request for automated protocols to manage and study the datasets is widely justified. The combination of Spectral Angle Mapper, data manipulation, and a user-adjustable analysis method constitutes a key-turn for exploring the experimental results.

Reflectance Spectroscopy (RS) and Fiber Optics Reflectance Spectroscopy (FORS) are well-established techniques for the investigation of works of art with ...

An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints

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A Whole Cell Bioreporter Approach to Assess Transport and Bioavailability of Organic Contaminants in Water Unsaturated Systems

Diffuse Reflectance Infrared Spectroscopic Identification of Dispersant/Particle Bonding Mechanisms in Functional Inks

Analyzing the Photo-oxidation of 2-propanol at Indoor Air Level Concentrations Using Field Asymmetric Ion Mobility Spectrometry

Original Experimental Approach for Assessing Transport Fuel Stability

In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds

Analyzing Mixing Inhomogeneity in a Microfluidic Device by Microscale Schlieren Technique

Imaging Corrosion at the Metal-Paint Interface Using Time-of-Flight Secondary Ion Mass Spectrometry

A Two-Step Pyrolysis-Gas Chromatography Method with Mass Spectrometric Detection for Identification of Tattoo Ink Ingredients and Counterfeit Products

Applying Hyperspectral Reflectance Imaging to Investigate the Palettes and the Techniques of Painters