Calorimetric studies of the growth of Desulfovibrio desulfuricans in the presence of nitrocellulose

Calorimetric results indicate that nitrocellulose (NC)-induced changes in the metabolism of Desulfovibrio desulfuricans 1388 are caused by both chemical (nitrate) and physical (biofilm formation) factors. Nitrate added to lactate-based culture medium with nitrocellulose competed for the electron flux from lactate and suppressed the bacterial sulfidogenesis and growth. The presence of an insoluble compound (carbon backbone of the polymer) induced the creation of a biofilm-like structure with its own metabolism.     

Thermal characteristics of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate in contact with nitrocellulose/nitroglycerine under continuous heat flow

Dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) and nitrocellulose/nitroglycerine (NC/NG) possess good energy properties, which were widely used in propellants, explosives and pyrotechnics. They are easy to contact with each other during their application and storage. However, their thermal characteristics under continuous heat flow have not been reported yet. Therefore, it is of great practical significance to study the thermal properties of TKX-50/NC/NG (mixture of TKX-50 and NC/NG). In this paper, the thermal characteristics and pressure behaviors of TKX-50/NC/NG, TKX-50 and NC/NG were characterized by high pressure differential scanning calorimetry (HPDSC) and adiabatic scanning calorimetry (ASC). The results showed that TKX-50 and NC/NG can promote each other to decompose under continuous heat flow, especially the thermal decomposition which affected by gases generation and heat feedback was more violent in the confined space. The decomposition peak temperature of TKX-50/NC/NG shifted to low temperature when the heat loss was ignored and the removal of decomposition gas was suppressed. The possible decomposition mechanism of TKX-50/NC/NG was speculated. It was considered that the intermediate products of TKX-50 and NC/NG decomposition under thermal stimulation would react with each other, which promoted TKX-50/NC/NG decomposition in one step at lower temperature. Thus, TKX-50 has high reactivity and high potential risk after contact with NC/NG under continuous heat flow. TKX-50 is not suitable for application with NC/NG. This study provides a reference for the structural design of nitrogen rich explosives and further broadens the researchers’ understanding of the application of TKX-50.     

Analytical techniques in the study of highly-nitrated nitrocellulose

This work presents an updated overview of the analytical techniques used to study highly-nitrated nitrocellulose, which is used in explosives and is of forensic interest. Most articles published in the past decade were designed:(1) to investigate polymeric parameters of nitrocellulose (e.g., molar mass distribution, viscosity and specific refractive index) by size-exclusion chromatography;(2) to determine the morphological and thermal characteristics of nitrocellulose using thermal and spectroscopic techniques; and,(3) to study the thermal, biological and mechanical degradation of nitrocellulose by thermal, spectroscopic, and mass spectrometric (MS) techniques, alone or coupled to gas chromatography.However, the few papers that focused on the determination of nitrocellulose used in explosives employed analytical techniques [e.g., vibrational techniques (infrared and Raman spectroscopy), MS and ion-mobility spectrometry (IMS) and liquid chromatography (LC) (high-performance LC and ion chromatography)]. Most of the information reported by these techniques has been qualitative. Only quantitative determination of nitrocellulose or its nitrogen content has been performed by measuring the nitrite and/or nitrate ions released from its basic hydrolysis.     

各色硝基铅笔漆中“可溶性”铅含量的测定

我们采用国家标准GB 9760[1]和GB9758.1[2]对各色硝基铅笔漆中"可溶性"铅含量进行了测定。本文对实验中酸萃取物的制备,样品的处理以及仪器最佳工作条件的选择等进行了研究。实验结果表明,只要根据样品实际情况,选择分离硝基漆中颜料效果最好的溶剂或混合溶剂,严格地遵守GB9760和CB9758.1实验步骤的全部细目等。就能得到足够的精密度,使实验获得成功。     

Swelling and dissolution of cellulose, Part V: cellulose derivatives fibres in aqueous systems and ionic liquids

The swelling and dissolution mechanisms of several cellulose derivatives (nitrocellulose, cyanoethylcellulose and xanthate fibres) are studied in aqueous systems (N-methylmorpholine-N-oxide—water with various contents of water, hydroxide sodium—water) and in ionic liquids. The results are compared with the five modes describing the swelling and dissolution mechanisms of cotton and wood cellulose fibres. The mechanisms observed for the cellulose derivatives are similar to the ones of cotton and wood fibres. Swelling by ballooning is also seen with cellulose derivatives, showing that this phenomenon is linked to the fibre morphology, which can be kept after undergoing a heterogeneous derivatisation. Patrick Navard and Thomas Heinze—Members of the European Polysaccharide Network of Excellence (EPNOE),     

提高MALDI-MS测量溶菌酶分子量灵敏度的研究

近 1 0年来 ,基质辅助激光解吸质谱 (MALDI- MS)作为一种新兴的“软电离”质谱技术 [1,2 ] ,已很快地应用于生物大分子特别是蛋白质研究领域 [3 ] .MALDI- MS可在 1 0 - 12 mol甚至 1 0 - 15mol的水平上 ,准确地测定分子量高达几万到几十万的生物大分子 ;还可通过改变基质、溶液条件和样品的制备方法等实现大分子蛋白质非共价复合物的质谱检测 [4 ] .MALDI- MS能够得到如此广泛的应用 ,在很大程度上要归功于基质的辅助效应 .基质的作用主要可以概括如下 [5～ 7] :(1 )削弱样品分子间的相互作用 ;(2 )与样品分子结合并使之快速结晶 …     

Determination of nitrocellulose by capillary electrophoresis with laser-induced fluorescence detection

The industrial application of nitrocellulose depends on its nitrogen content. When nitrocellulose presents high nitrogen content is used in the manufacture of explosives whereas nitrocellulose with low nitrogen content is used to make a wide range of daily and non-explosive products (e.g. cigarettes, paints, lacquers). This fact makes really important to develop a method for the determination and discrimination of nitrocellulose samples. This work reports, for the first time, the qualitative determination of nitrocellulose previously derivatized with 8-aminopyrene-1,3,6-trisulfonic acid (APTS) by capillary electrophoresis (CE-LIF) with laser-induced fluorescence detection (CE-LIF). APTS-labeled nitrocellulose was determined in lowly and highly nitrated nitrocellulose samples present in collodions and smokeless gunpowders, respectively, after their pulverization in liquid nitrogen. The method described enables the visual discrimination of different nitrocelluloses on the basis of the different electrophoretic profiles obtained, and provides a useful tool to determine nitrocellulose. Additionally, the use of field-amplified sample injection (FASI) enabled enhanced sample detection, which made it possible to determine nitrocellulose contained in ∼15 μg of gunpowder.     

A competitive immunochromatographic assay for testosterone based on electrochemical detection

An immunochromatographic assay using nitrocellulose membrane was combined with electrochemical detection using an electrode chip in order to quantitatively detect testosterone as a model analyte. The electrode chip consisted of a gold working electrode, a counter electrode and a pseudo-reference electrode, all fabricated on the bottom of a 3.2 mm × 3.2 mm well. Competitive immunoreactions on the membrane were initiated by flowing a solution containing testosterone and horseradish peroxidase (HRP)-labeled testosterone (a competitor) over the membrane. Prepared membrane was placed in a solution containing ferrocenemethanol (FcOH) and H₂O₂ in the well of the electrode chip, and the enzyme reaction was detected by amperometry. Labeled HRP captured on the membrane catalyzed the oxidation of FcOH to the oxidized form FcOH⁺, which was reduced electrochemically by the electrode chip. The electrochemical response of the reduction current decreased with increasing concentration of testosterone over the range 1–625 ng/ml.     

Use of UV-visible spectroscopy to monitor nitrocellulose degradation in thin films

Activation energies for nitrocellulose (NC) degradation have been determined from Arrhenius plots constructed using first-order rate constants measured at 40, 50 and 60 °C. The rate constants were obtained by monitoring the absorbance (A) at a wavelength in the visible region of an anthraquinone dye dispersed in NC thin films. The dye acts as a stabilizer and is slowly depleted as a result of its reaction with NO_x from the breakdown of the nitrate ester groups on NC. The data produced two linear regions in the first-order plots of ln(A₀/A_t) vs aging time. The first-region is attributed to the reaction of the dye with NO_x desorbed from the NC surface. The activation energy (∼73.5 kJ mol⁻¹) is in line with that found for NO_x surface desorption processes. The second linear region is thought to be due to the reaction of NO_x from the breakdown of the nitrate ester groups on the NC molecule. The activation energy (∼104.0 kJ mol⁻¹) is consistent with that for nitrate ester hydrolysis. The use of UV-visible spectroscopy has in this way made it possible to monitor the degradation of NC non-destructively without the need for stabilizer extraction and analysis.     

The effect of light on the viscosity and molecular mass of nitrocellulose

The photodegradation of a series of nitrocellulose (NC) samples with nitrogen contents ranging from 11.69% to 13.55% has been investigated by observing changes in molecular mass and viscosity using, respectively, size exclusion chromatography (SEC) and a modified cone and plate rheometer. When NC in γ-butyrolactone was subjected to UV light in the range 320-390 nm its specific viscosity (η_sp) was found to decrease noticeably, a change attributed to polymer chain scission and de-aggregation. This view was supported by an observed reduction in the mass average molecular mass (M_w). In contrast, irradiation with a single wavelength at 365 nm did not significantly change either η_sp or M_w and similar behaviour was observed when NC solutions were irradiated with visible light (400-500 nm). In the solid state, the photodegradation of water-wet NC is faster than that of the dried material, which is attributed to the catalytic effect of acids formed from the reaction between water and nitrogen oxides (NO_x) arising from NC decomposition. A higher degree of crystallinity in the NC, as found by X-ray diffraction (XRD), was shown to lead to a smaller decrease in viscosity and molecular mass. This is thought to be because the photodegradation reaction is suppressed in crystalline NC by more effective radical-radical recombination.