Morphological characteristics of flashing jet throughout superheated liquid release

Many release problems involve two-phase releases of hazardous materials of superheated liquids with high energy into the atmosphere. Such accidents are accompanied by violent phase transition and form catastrophic flashing jets. In this work, experimental and theoretical analyses were conducted to investigate dynamic characteristics of flashing jet morphology and their dependence on pressure-decay dynamics under different storage pressures, superheats, and nozzle diameters. Flashing jet morphology and angle throughout two-phase releases were captured by a high-speed camera, and the corresponding source pressure in the superheated liquid tank was measured simultaneously. Results show that three typical phases, expansion, stabilization, and decay, are characterized throughout two-phase release based on the evolution of flashing jet morphology. The jet initially expands gradually due to the enhancement of phase transition intensity, and then keeps stable when the intensity reaches its maximum, and terminally decays rapidly due to the depletion of superheated liquid. Phase transition intensity at the nozzle exit is mainly controlled by the pressure-decay dynamics. Bubbles nucleation inception sites gradually move upstream of the nozzle during the pressure decay process increasing the phase transition intensity. The increase of storage pressure, superheat and nozzle diameter promotes the mechanical and thermodynamic effects on the jet breakup. The significant increase of mechanical and thermodynamic effects effectively accelerates droplets evaporation and further affects flashing jet morphology.     

Experimental investigation of the lower flammability limit of volatile liquid fuel-aluminum powder mixtures in air

Aluminum powder was always chosen as an additive to improve the explosive performance. In this work, experiments were performed to investigate the lower flammability limit (LFL) of volatile liquid fuel-aluminum powder mixtures using a 20 L closed spherical stainless steel vessel at a temperature of 20 °C (293 K) and 40 °C (313 K). The volatile liquid fuels tested in the work were diethyl ether (DEE), epoxypropane (PO), n-pentane and n-hexane. DEE, PO and n-pentane are in the liquid phase at room temperature and can easily transition to the gas phase at 40 °C (313 K). Through a series of experiments carried out, it was found that the change in phase would affect the interaction between the components. Aluminum powder always has an inhibitory effect on the flammability of the mixtures when it is mixed with gas-phase fuels. The inhibition effect was most obvious when the aluminum powder concentration reached 200 g/m³. While the interaction between aluminum powder and liquid-phase volatile fuels was promotion and was influenced by the component proportion and the type of the volatile fuels.     

An LC-MS/MS method for creatine and creatinine analysis in paraquat-intoxicated patients

Abstract

A sudden increase in serum creatinine after paraquat intoxication has been reported in several clinical studies. However, this dramatic change of creatinine may be possibly due to an interconversion of creatine-creatinine in relation to paraquat toxicity. In order to investigate the creatine-creatinine relationship, a liquid chromatography tandem mass spectrometry in combination with electrospray ionization was developed and validated for simultaneous determination of creatine and creatinine in the serum. The chromatographic separation was achieved on a Gemini® C₆-Phenyl column with a gradient elution consisting of 0.1% formic acid in ultrapure water and methanol as the mobile phase. The method yielded suitable levels of specificity and selectivity, and calibration curves of creatine and creatinine in serum were linear over the concentration range of 0.5–200?µg mL^?1. The limit of quantification of both compounds was 0.5?µg mL^?1, and the method was accurate within the recovery range of 96.23–102.75%, indicating the robustness of the method. The method was successfully applied to toxicological samples from paraquat-intoxicated patients, and the concentrations of creatine and creatinine were quantified. High creatine concentrations in serum samples were observed which may lead to high serum creatinine despite normal kidney function as creatine is converted to creatinine in proportion to its concentration.     

高效液相色谱-三重四级杆/复合线性离子阱质谱法测定饮用水中22种邻苯二甲酸酯

建立了一种同时测定饮用水中22种邻苯二甲酸酯(PAEs)的高效液相色谱-三重四级杆/复合线性离子阱质谱方法:饮用水样品经针头过滤器过滤,选用Biphenyl液相色谱柱进行分离,以含0.1%甲酸的水溶液和含0.1%甲酸的甲醇溶液为流动相,电离模式为电喷雾正离子,选用多反应监测触发增强子离子扫描模式进行检测。结果表明,22种PAEs的灵敏度良好,定量限为0.001～0.1 μg/L。配制浓度为0.1～100.0 μg/L的混标溶液进行进样分析,分析结果显示,22种PAEs在该范围内的线性关系良好,相关系数均大于0.995,方法的平均回收率为82.9%～108.9%,相对标准偏差为0.9%～11.2%。同时,使用增强子离子扫描谱图进行搜库匹配,定性准确性高。该方法适用于饮用水中PAEs的检测。     

苦味酸测定中关键问题的研究

目前测定苦味酸的国标方法为《生活饮用水标准检验方法有机物指标》(GB/T 5750.8—2006)中的衍生物-液液萃取-气相色谱法,在实际测试过程中,发现水样pH值和基质效应会影响苦味酸测定。当pH值为8~12时,生成的氯化苦响应强度变化不大;在pH约为13时,响应强度最大。水质中除腐殖酸、硝基甲烷及2,4,6-三硝基甲苯会影响苦味酸测定外,硝基酚类和甲基酚类同样起到正干扰作用,因此,国标方法不能全面和准确地测定水中的苦味酸含量。     

超高效液相色谱法测定土壤中微量阿特拉津

采用超高效液相色谱仪,建立了土壤中微量阿特拉津的快速检测方法.研究结果表明:采用反相C18色谱柱,以甲醇/水(70:30,v/v)为流动相,流速为0.2 ml/min,柱温为30℃,检测波长为220 nm条件下,在12.5～1000μg/L质量浓度范围内线性关系良好(r=0.9999),检出限0.18×10-3 mg/...     

Dissipation of Endosulfan and Dichlorvos Residues In/On Cauliflower Curds

Dissipation behaviour of endosulfan and dichlorvos in/on cauliflower, variety Snowball-16, was studied during rabi season (Sep.–March) 2003–2004. Endosulfan and dichlorvos were sprayed @ 350 and 110g a.i. with 115 g a.i., respectively, 80 days after transplanting. Samples were taken at the interval of 0 (1h after spray), 3, 5, 7, and 10 days after spray (DAS) in triplicate and residues were estimated on GC-ECD system equipped with capillary column. The initial deposits of 3.452 and 0.295μgg⁻¹ of endosulfan and dichlorvos dissipated to 0.084 (97.56%) and 0.009 (96.95%), respectively after 10 DAS. Residues of endosulfan reached below maximum residue limit of 2μgg⁻¹ one day after spray and of dichlorvos were below MRL value of 0.5μgg⁻¹ even on 0 day. Dissipation pattern followed first order kinetics for both the insecticides with half life periods of 1.81 and 2.08 days for endosulfan and dichlorvos, respectively.     

液膜分离技术处理含Cr6+废水的研究

采用液膜分离技术处理Cr^6＋质量浓度为200—1000mg／L的废水,考察了膜溶剂、载体、内水相、外水相、pH、乳水比（乳液与废水的体积比）等因素对处理效果的影响,通过正交实验得出最佳实验条件。结果表明,在膜溶剂为煤油、载体为三辛胺、内水相为氯氧化钠、氢氧化钠质量分数为2％、pn为1、乳水比为1：4的最佳条件下,Cr^6＋的去除率可达98．4％。     

气相色谱法直接测定水中微量有机胺

用配有氢火焰离子化检测器（FID）的气相色谱仪直接测定水中多种微量有机胺。试样经过滤后直接进样,在气相色谱仪上使用CP7448毛细管柱,用外标法测定水中微量甲胺、二甲胺、一乙胺、二乙胺的含量。在所选择的色谱操作条件下,甲胺、二甲胺、一乙胺、二乙胺的质量浓度分别在一定范围内与峰面积呈良好的线性关系。4种组分的回收率分别为96.7％,99．0％,101．2％,99．2％;精密度分别为4．3％,3．7％,5．5％,3．1％;检出限分别为2．0,2．0,1．5,1．5mg/L。该方法操作简便,回收率、精密度高。     

分子印迹技术在环境科学领域中的应用

分子印迹技术（MIT）是一门新兴的边缘科学技术,它的产生与发展为环境科学打开了又一视角。介绍了MIT的产生与发展及基本原理,综述了MIT在环境科学领域中的应用,主要包括MIT在固相萃取、膜分离、色谱分析、传感器及分子印迹聚合物作为催化剂在环境修复中的应用。