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Le Touquet – Paris-Plage, France

Alinat E.,Chimie Paristech | Alinat E.,Central Laboratory of Police Prefecture LCPP | Alinat E.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Alinat E.,Paris-Sorbonne University | And 9 more authors.
Carbohydrate Polymers | Year: 2015

Specific viscosities for a set of six nitrocellulose (NC) standards comprising three different mass-average molar masses (between 20,000 and 300,000 g mol-1) of two different nitrogen contents (11.2 and 12.1%) were measured at 20°C in tetrahydrofuran, using capillary electrophoresis instrumentation as a bench-top viscometer in frontal mode. Intrinsic viscosities were derived applying Huggins' and Kraemer's models, showing excellent convergence of both models at infinitely diluted polymer concentration. Good overall consistency was shown between viscosity data experimentally acquired by this new protocol and the mass-average molar masses provided by the manufacturers. This simple protocol should be of interest for a better understanding of the solvent interaction given by this complex polymer, and beyond this, for tailoring NC solutions devoted to film deposition, and for the determination of mass-average molar masses of unknown NC samples. © 2015 Elsevier Ltd.All rights reserved. Source


Alinat E.,ESPCI ParisTech | Alinat E.,Central Laboratory of Police Prefecture LCPP | Alinat E.,CNRS Chemistry, Biology and Innovation Laboratory | Jemmali S.,ESPCI ParisTech | And 7 more authors.
Electrophoresis | Year: 2015

This work focuses on the development of a CE method allowing, for the first time, the simultaneous separation of the underivatized first seven cellodextrin oligomers (glucose, cellobiose, cellotriose, cellotetraose, cellopentaose, cellohexaose, and celloheptaose), with a view to analyze the hydrolysates obtained after partial acid depolymerization of nitrocellulose, and eight carbohydrates (ribose, xylose, fructose, mannose, galactose, maltose, lactose, and sucrose), which might be potential interfering compounds in explosives samples. Separation was achieved with a highly alkaline BGE containing sodium chloride and direct mid-UV-absorbance detection was performed after photo-oxidation in the detection window. EOF was reversed to speed up the analysis using a dynamic capillary coating by hexadimethrine bromide. A central composite design was carried out to determine the effects of BGE conductivity and sodium hydroxide concentration on resolutions between neighboring peaks, and analysis time. A desirability analysis on modeled responses was applied to maximize resolutions and to minimize analysis time. The simultaneous analysis in 20 min total runtime of the 15 carbohydrates plus internal reference (naphthalene sulfonate) was carried out at 25°C with a BGE composed of 77.4 mM NaOH and 183 mM NaCl to adjust the conductivity at the optimum value. Finally, the resolution robustness was checked. This new method should also be of interest to monitor food and nonfood crop products. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Alinat E.,ESPCI ParisTech | Alinat E.,Central Laboratory of Police Prefecture LCPP | Alinat E.,CNRS Chemistry, Biology and Innovation Laboratory | Delaunay N.,ESPCI ParisTech | And 9 more authors.
Journal of Chromatography A | Year: 2015

Fine characterization of nitrocellulose (NC) remains a challenge, especially in forensic analysis, and a strategy consisting in obtaining representative fingerprints by a separation technique, as for proteins, is of prime interest. In this work, we first established that NCs (especially of high molar mass) cannot be representatively derivatized by 8-aminopyrene-1,3,6-trisulfonic acid (APTS), because of their poor solubility in the medium required for APTS derivatization. Therefore, a partial acid depolymerization step was considered, prior to derivatization by APTS, in an attempt to generate a mixture of oligosaccharides retaining information on the initial NC sample and/or on the cellulose used to prepare it. Acid depolymerization conditions (time and acid concentration) as well as APTS derivatization conditions (time, temperature, APTS/NC and reducing agent/APTS molar ratios) were investigated for lowly-nitrated NCs. The best compromise between depolymerization yields, speed, and pertinency of the resulting oligosaccharidic mixture was obtained using fuming hydrochloric acid (37%, w/w) at 50. °C for 30. min. The most effective procedure for APTS derivatization of oligosaccharides obtained after partial acid depolymerization of NC was achieved at 70. °C for 2. h. The resulting APTS-derivatized oligosaccharides were then separated by capillary electrophoresis (CE) using a background electrolyte composed of 60. mM 6-aminocaproic acid, pH 4.5 (adjusted with acetic acid). +. 0.02% hydroxypropyl methyl cellulose. Finally, for the first time, they were identified using APTS-derivatized cellodextrin standards and by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS). © 2015 Elsevier B.V. Source


Alinat E.,Chimie Paristech | Alinat E.,Central Laboratory of Police Prefecture LCPP | Alinat E.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Alinat E.,University Pierre and Marie Curie | And 9 more authors.
Talanta | Year: 2014

Nitrocellulose (NC) is a nitrate cellulose ester polymer whose nitrogen content determines its physical and chemical properties and its industrial applications. For the first time, capillary electrophoresis (CE) was used to quantify nitrite and nitrate ions released after the alkaline hydrolysis of NC to determine its nitrogen content. This article focuses on the development and validation of the CE method adapted to the determination of these anions in basic matrices in 3 min total runtime. Molybdate anion was used as internal standard. The matrix effect in sodium hydroxide solution was statistically studied, demonstrating that no significant effect occurred in 0.5 M sodium hydroxide solution. RSDs on normalized migration times (n=20) were 0.05% for both anions, while RSDs on normalized corrected areas (n=20) were 0.8% and 0.7% for nitrite and nitrate ions, respectively. The selectivity of the CE method was checked in the presence of 10 other anionic species potentially present in post-blast residues. Excellent linearities for normalized corrected areas (R2>0.999, residual standard deviations of ca 0.05) were obtained for both anions in the range 5-100 mg L-1. Finally, the optimized CE method was successfully applied to calculate the denitration yields of two NC standards belonging to the non-explosive and explosive classes, and to determine the nitrogen content of a NC contained in a single-base gunpowder. CE, with its speed, low running costs, and simplicity of use, appears as a valuable alternative to ion chromatography for the nitrogen content determination of pure NCs and NC-based explosives, and more generally, for the determination of nitrite and nitrate ions in other highly alkaline matrices. © 2014 Elsevier B.V. Source


Alinat E.,Chimie Paristech | Alinat E.,Central Laboratory of Police Prefecture LCPP | Alinat E.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Alinat E.,University Pierre and Marie Curie | And 10 more authors.
Forensic Science International | Year: 2015

The nitrogen content is of paramount importance to predict the explosive or non-explosive character of nitrocellulose (NC), and hence its applications. There are still quite a few really effective analytical methodologies allowing its determination, due to great NC molecular complexity. One of the approaches giving access to nitrogen content consists in releasing the nitrogenic moieties through alkaline hydrolysis. For the first time, this work reports on the optimization of the denitration yield by means of an experimental design within reasonable ranges of sodium hydroxide concentration, temperature, and time. The experiments were conducted with non-explosive and explosive NC standards. An original capillary electrophoresis (CE) method was used to monitor nitrite and nitrate ions released during hydrolysis. Because of their very different chemical properties, denitration conditions were optimized separately for both sub-classes of NCs to maximize their denitration yields, applying desirability analysis on modeled denitration yields. Mild, safe, and robust optimized conditions were drawn. The denitration yields (95% for non-explosive NCs, 92% for explosive NCs) experimentally obtained under these conditions were in good agreement with model predictions. For practical purposes, correction factors based on these maximal denitration yields are proposed for the first time to correct the determination of nitrogen content, based on preliminary alkaline denitration. This new strategy was successfully applied to determine nitrogen contents of NCs in real explosive samples (smokeless gunpowders). © 2015 Elsevier Ireland Ltd. Source

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