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.     

Semimicro spectrophotometric determination of nitroglycerine in propellants by use of 2,4-xylenol

A semimicro spectrophotometric method using 2,4-xylenol is proposed for the determination of nitroglycerine in propellants. The propellant is extracted with methylene chloride, the extract is diluted, and a 10-ml aliquot is evaporated just to dryness. Then 2,4-xylenol reagent and 63% v/v sulphuric acid are added to hydrolyse the nitroglycerine to nitrate and form 6-nitro-2,4-xylenol which is steam-distilled in a Parnas-Wagner Kjeldahl distillation apparatus into a water-ammonia-isopropyl alcohol mixture. The absorbance of the yellow solution of the anion of the 6-nitro-2,4-xylenol is measured. The calibration curve is prepared from potassium nitrate and an empirical factor (5.50) is used to convert from nitrogen content to nitroglycerine (the theoretical factor is 5.40). The 2,4-xylenol should be added before the sulphuric acid in order to prevent interference from diphenylamine and ethyl centralite. The method is designed for the usual nitrocellulose double-base propellants containing 8-50% of nitroglycerine.     

The determination of nitrogen in nitrocellulose

A method for the determination of nitrogen in nitrocellulose has been developed. The sample is dissolved in concentrated sulphuric acid and a salicylic acid solution is added. The nitrosalicylic acid formed is reduced at room temperature with an excess of titanous chloride solution and the excess is estimated by titration with ferric alum. Statistically designed experiments were used to establish the conditions necessary for accurate results. The procedure is more rapid than the usual nitrometer method and gives results of high precision; e.g. on a mean result of about 13.8% nitrogen, the standard deviation is 0.014.     

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.     

Determination of the nitrogen content of nitrocellulose from smokeless gunpowders and collodions by alkaline hydrolysis and ion chromatography

In this work, a method to determine the nitrogen content of nitrocellulose from gunpowders and collodions is proposed. A basic hydrolysis of nitrocellulose with 1.0% (m/v) NaOH at 150 °C during 30 min was carried out for nitrocellulose from gunpowders (after its previous isolation by a protocol optimized by our research group) and from collodion samples. The concentration of nitrate and nitrite ions in the hydrolysate was determined by ion chromatography with suppression and conductimetric detection. The nitrogen content of nitrocellulose was calculated from the values of the concentration of both ions. The quantitative method was evaluated in terms of selectivity, sensitivity, robustness, limits of detection and quantification, and precision, measured as repeatability and intermediate precision. These parameters were good enough to demonstrate the validity of the method and its applicability to the determination of the nitrogen content of nitrocellulose contained in different types of gunpowders (single- and double-base gunpowders, manufactured from 1944 to 1997) and in commercial collodion samples. For gunpowders, the nitrogen content determined with the optimized method was compared with the values reported by the official label of the ammunition (obtained by a digestion/titration method) and errors, by defect, ranging from 1% to 15.2% (m/m) were calculated. The highest errors were obtained for the oldest gunpowders and could be attributed to the loss of nitro groups in the nitrocellulose molecule during aging. For collodion samples, errors could not be calculated since the real nitrogen content for these samples was not given in the label. In addition, the analysis time (2 h for nitrocellulose isolation, 1.5 h for nitrocellulose hydrolysis, and 0.2 h for chromatographic separation) was about 10 times lower than in the digestion/titration method nowadays used for gunpowder samples.     

A reproducible method for determination of nitrocellulose in soil

A reproducible analytical method for determination of nitrocellulose in soil is described. The new method provides the precision and accuracy needed for quantitation of nitrocellulose in soils to enable worker safety on contaminated sites. The method utilizes water and ethanol washes to remove co-contaminants, acetone extraction of nitrocellulose, and base hydrolysis of the extract to reduce nitrate groups. The hydrolysate is then neutralized and analyzed by ion chromatography for determination of free nitrate and nitrite. A variety of bases for hydrolysis and acids for neutralization were evaluated, with 5N sodium hydroxide and carbon dioxide giving the most complete hydrolysis and interference-free neutralization, respectively. The concentration of nitrocellulose in the soil is calculated from the concentrations of nitrate and nitrite and the weight percentage of nitrogen content in nitrocellulose. The laboratory detection limit for the analysis is 10mg/kg. The method acceptance range for recovery of nitrocellulose from control samples is 78-105%.     

Miscibility of polyester/nitrocellulose blends: A DSC and FTIR study

The miscibility of polyester/nitrocellulose blends was investigated by differential scanning calorimetry and Fourier-transform infrared (FTIR) spectroscopy. Two nitrocelluloses (NC) derived from wood and having different nitrogen contents (12.62 and 13.42%) were used. On the basis of the glass transition temperature criterion, poly(?-caprolactone) (PCL), poly(valerolactone), poly(ethylene adipate), and poly(butylene adipate) are miscible with nitrocellulose, whereas poly(α-methyl α-propyl β-propiolactone) and poly(α-methyl β-proiolactone) are immiscible. The T_g versus composition curves of PCL/NC blends do not follow a monotone function but exhibit a singular point at a critical PCL volume fraction of 0.51 for NC-1342 and 0.45 for NC-1262 in agreement with Kovacs' theory. A shift of 17 cm^-1 of the carbonyl stretching band was observed with PCL/NC blends and is taken as evidence for hydrogen bonding interaction between the PCL carbonyl group and NC hydroxyl group. The frequency difference between the free hydroxyl absorbance and the absorbances of the hydrogen-bonded species was found to be 85 cm^-1 in pure NC and 125 cm^-1 in PCL/NC blends; it indicates that the average strength of this interaction is stronger than the corresponding self-associated hydrogen bonding in pure NC. The presence of a dipole-dipole interaction between the nitrate-ester groups of NC and the carbonyl groups of the polyesters is reported. The relative strength of the hydrogen bonding and dipole-dipole interactions is discussed and correlated with polymer miscibility.     

Studies on graft copolymerization onto cellulose derivatives. XXVII. Photo-induced graft copolymerization onto nitrocellulose

Photo-induced graft copolymerization was investigated using nitrocellulose having a different nitrogen content, especially by a noncatalytic method. The effects of a sample nitrogen content, reaction temperature, and monomer, sample, solvent and photosensitizer concentrations on the degree of grafting, the grafting efficiency, and the apparent number of grafted chains were examined. Methyl methacrylate (MMA) and methyl acrylate (MA) easily polymerized, but acrylamide (AAm), vinyl acetate (VAc), and styrene (St) scarcely polymerized. The apparent activation energies were 4.1–11.5 kcal/mol, indicating the small value in the high nitrogen content sample. The degree of grafting and the apparent number of grafted chains increased with increasing monomer and sample concentrations. In every case, the grafting efficiency was at a high level, above 90%. The polymerization did not occur without the sample in the same condition. Furthermore, a part of nitro groups split off by the irradiation of light. With respect to these results, the mechanisms of the photo graft copolymerization was discussed.     

Determination of arsenic in organic compounds rapid micro and semimicro methods

Rapid micro and semimicro methods for determination of arsenic in organic compounds have been developed using 28% chloric acid as the digesting agent for the organic arsenical. This wet acid digestion procedure does not lead to loss of arsenic even in the presence of 4 M chloride.The semimicro method completes the assay by reduction of the pentavalent arsenic with iodide, destruction of the iodine liberated with thiosulfate and re-oxidation to pentavalent arsenic with iodine in a buffered solution. The micro method completes the assay by development of a heteropoly molybdenum blue using a single solution reagent at room temperature. The color is reproducible so that only a single calibration curve for the instrument used is necessary.     

氢化物发生-原子荧光光谱法测定岩石中砷和锑

应用氢化物发生-原子荧光光谱法测定了岩石中砷和锑的含量。样品预先粉碎至通过孔径为0.25～0.42mm的细筛,称取此粉碎的样品0.1000～0.3000g,先于盐酸-硝酸(3+1)混合酸8mL中浸泡30 min,然后放入沸水浴中消解2 h,将溶液及不溶物一起移入50 mL容量瓶中,加水定容。移取上清液5.00mL置于10mL容量瓶中,加入100g·L~(-1)硫脲及抗坏血酸混合溶液2.5mL,用盐酸(5+95)溶液定容,分取此溶液1.0mL进样按选定的仪器条件进行分析。用20g·L~(-1)硼氢化钾溶液作为产生砷及锑的氢化物的还原剂,砷(Ⅲ)及锑(Ⅲ)的质量浓度依次在0.50～60μg·L~(-1)和0.50～80μg·L~(-1)范围内与其相应的荧光强度呈线性关系。应用此方法测定了两种岩石标准物质(GBW 07106及GBW 07108)中的砷及锑量,其测定值与认定值一致,相对标准偏差(n=5)均小于3.5%。     

Kinetic Flow Injection Spectrophotometric Determination of Nitrite by its Catalytic Effect on the Oxidation of Chlorophosphonazo-pN by Bromate

Abstract

A flow injection kinetic method has been developed for the determination of nitrite, based on its catalytic effect on bromate oxidation of chlorophosphonazo-pN in H₂SO₄ medium. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance at 551 nm. The sampling frequency was 83 h^?1. The calibration curve was linear between 0.050 and 1.00 μg/ml, and the detection limit was 0.018 μg/ml. The proposed method was applied to the determination of nitrite in waters and soil with satisfactory results.     

电感耦合等离子体质谱法测定新型抗菌不锈钢在生理盐水和磷酸盐缓冲液中的镓溶出量

建立了电感耦合等离子体质谱法测定新型抗菌不锈钢在生理盐水和磷酸盐缓冲液中的镓溶出量的分析方法. 为了消除盐沉积的影响,在进样系统中引入了Burgerner AriMist耐高盐雾化器和加厚嵌片. 同时,通过稀释样品并使用铟作为内标校正了基体干扰. 在选定的分析条件下,校准曲线的线性相关系数大于0.999,方法检出限为0.08 μg/L,测定结果的相对标准偏差小于3.0%（n=6）,加标回收率为98.3%~105.4%. 方法操作简单快速,可用于生理盐水和磷酸盐缓冲液中痕量镓的快速测定.     

超高效液相色谱-串联质谱法同时测定牛肉中18种食源性兴奋剂类药物残留

建立了超高效液相色谱-串联质谱（UHPLC-MS/MS）检测牛肉中18种食源性兴奋剂类药物残留的方法。牛肉组织经酸化乙腈提取,Captiva小柱脱脂净化后,用无水硫酸镁干燥,上清液氮吹浓缩,残渣用甲醇-水（7：3,v/v）溶解。采用Agilent Zorbax Phenyl-Hexyl色谱柱分离,以5 mmol/L醋酸铵水溶液（含0.01%（v/v）醋酸）和甲醇-乙腈（7：3,v/v）作为流动相进行梯度洗脱,在电喷雾正负离子切换模式下以多反应监测（MRM）方式检测,用基质匹配标准曲线外标法定量。结果表明,18种食源性兴奋剂类药物在0.10~50 μg/L范围内线性关系良好,相关系数（R²）≥ 0.9950;在0.4、1.0和2.0 μg/kg添加水平下的回收率为57.3%~117.5%,相对标准偏差为3.1~15.6%（n=5）;方法的检出限和定量限分别为0.0006~0.0900 μg/kg和0.0020~0.3000 μg/kg。该法可以实现对牛肉样本中18种兴奋剂类药物残留的定性定量分析,具有简单、快速、准确性高的特点。     

Determination of arsenic in sediments, coal and fly ash slurries after ultrasonic treatment by hydride generation atomic absorption spectrometry and trapping in an iridium-treated graphite tube

A simple and reliable method for the determination of arsenic in sediment and in coal without sample digestion, based on hydride generation from slurry samples is proposed. After grinding the samples to a particle size of 50 μm, the sample powder was mixed with aqua regia and hydrofluoric acid in an ultrasonic bath for 30 min. After diluting the mixture with hydrochloric acid, the slurry was allowed to stand for 48 h, and an aliquot was used for hydride generation with sodium borohydride. More than 80% of the arsenic was leached to the aqueous phase under these conditions, except for one sediment sample with very high silica content. The generated arsine was collected in a graphite tube, treated with 0.5 mg of iridium as a permanent modifier, and the arsenic determination was carried out by electrothermal atomic absorption spectrometry. The same tube could be used for at least 160 cycles without any re-treatment. The greatest advantage of the method was that only a minimum of reagents and sample handling were required, reducing the risks of contamination and/or analyte loss. However, the addition calibration technique had to be used in order to obtain results within the 95% confidence level for 11 certified reference materials, 5 sediments, 5 coals and one coal fly ash. One certified sediment slurry was spiked with the analyte and the resulting addition calibration curve was used for the analysis of the certified sediments. Similarly, one certified coal was used to obtain the addition calibration curve for the coal and coal fly ash samples. The recoveries of the certified values, except for one sediment, were between 91 and 115%. The limits of detection in the samples were 0.54 and 0.7 μg g⁻¹ for the coal and sediment samples, respectively, obtained for 1 ml of slurry containing 1 mg of sample.     

Development of a slurry atomization method for the determination of cadmium in food samples by electrothermal atomization atomic-absorption spectrometry

Matrix modifiers have been compared for the determination of cadmium in foodstuffs by ETA-AAS with the sample injected in the form of a slurry. Addition of 800 mug/ml Pd stabilized cadmium to a similar extent as did ammonium dihydrogen phosphate, but avoided the increase in background signal associated with the latter. An analytical procedure was developed, based on palladium matrix modification, platform atomization with a pre-atomization cooling step and integrated absorbance measurements. The method allowed the analysis of milk, liver and olive leaf slurries at concentrations up to at least 50 mg/ml by direct calibration with aqueous standards. The accuracy of the analytical results was within 15% and the detection limit for cadmium in analysis of a 50 mg/ml slurry was 10 ng/g.     

Standard-addition determination of nitrogen in coal with an ammonia-sensitive electrode

After semimicro Kjeldahl digestion of the coal sample with a K(2)SO(4)-V(2)O(5)-Se catalyst and sulphuric acid, the digest is cooled, diluted with water, neutralized and then made alkaline with NaOH/EDTA solution. The ammonia thus formed is determined by measuring the potential of a properly conditioned ammonia-sensitive electrode containing an appropriate filling solution; a gravimetric standard-addition technique is used. Known additions of 1-2 mug of N per g to blank solutions enables all measurements of potential to be made in the linear region of the electrode-response curve. The electrode measurement procedure gives blank-corrected recoveries of between 99.0 and 101.0% for synthetic sample solutions. Results obtained for nitrogen in reference coal samples by the electrode procedure have been found to agree well with those obtained by other methods.     

Volumetric determination of primary arylamines and nitrites, using an internal indicator system

A new nitrite titration method is presented. The titration is performed in the presence of a standard solution of 4,4'-sulphonyl-dianiline and diphenylamine, which is used as an internal indicator. An intense red colour develops during the titration as a result of a simultaneous diazotization and coupling process. A very sharp end-point is given by a colour change to yellow. The titration is performed at a temperature of about 45 degrees in the presence of large amounts of nitrate. The method is specific and precise. It is suitable for the direct volumetric determination of various easily diazotized primary arylamines, sulphonamides and other amino-compounds which can be determined by nitrite titration. It is suitable also for the indirect determination of nitrites. The method is applicable on the semimicro and macro scales.     

Determination of Tellurium by Gas Phase Molecular Absorption Spectrometry After Hydrogen Telluride Generation

Abstract

A method for determination of tellurium(IV) or tellurium(VI) is described that involves hydrogen telluride generation by reduction with sodium tetrahydro-borate(III), evolution of hydride with HCl solution, transport into a flow-cell placed in a UV-visible molecular absorption spectrophotometer and measurement of gas at 190 nm. Hydride generation and determination procedures are optimized, based on height and area of absorbance versus time profile of hydrogen telluride generated. Using the best experimental conditions found the calibration curve is linear from 5 to 100 μg/ml of tellurium, 1.1 μg/ml of tellurium(IV) or 3.1 μg/ml of tellurium(VI) can be detected, and relative standard deviation ranges from 4 to 7%. The method is applied to the analysis of additives for synthetic rubber making.     

高效液相色谱法测定地榆中金丝桃甙的含量

采用高效液相色谱法测定了地榆中金丝桃甙的含量。色谱柱为Ｓｈｉｍ－ｐａｃｋＣＬＣ－ＯＤＳ柱,以甲醇－０．０２５ｍｏｌ／Ｌ磷酸（５０５０）为流动相,检测波长３７０ｎｍ,测定组分与其它组分的色谱峰达到基线分离。加样回收率平均值为９８．７％,ＲＳＤ为１．９％。为控制中药地榆的内在质量提供了新的测定指标和可靠的方法。     

神经保护剂3β,5α,6β-雄甾三醇原料药中3种非对映异构体的分离与含量测定

建立了分离与测定3β,5α,6β-雄甾三醇(YC-6)原料药中3种非对映异构体的气相色谱方法。进行了分离条件的优化及方法学验证。研究结果表明:该方法可对YC-6与各非对映异构体进行分离,专属性良好(分离度≥1.5),精密度高(RSD≤2.0%);YC-6在6.0~30.0 mg/L质量浓度范围内线性关系良好。测定了非对映异构体的响应因子(1.59,1.32和1.41),并采用加校正因子的主成分自身对照内标法以峰面积计算各非对映异构体的含量。该方法操作简便,结果准确,可用于YC-6原料中各非对映异构体的分离及含量测定。