溶剂解吸-气相色谱法测定空气中苯含量测量不确定度评定

在实际测定空气中苯的含量的过程中,影响测定准确性的因素较多,如何控制这些因素,降低测定过程的误差,是做好测定工作的关键。通过对溶剂解吸-气相色谱测定空气中苯的不确定度进行分析,可以找出其主要的影响因素。所以有必要对其进行评价，以如实反映测量的置信度和准确性。     

固相微萃取-气相色谱联用法在气态物质定值中的应用

固相微萃取是新型样品前处理手段,可与气相色谱法联用,用于测定体系中痕量物质的量。文章以氮气中苯含量的测定为例,介绍固相微萃取-气相色谱联用法定值的一般过程,并对测量结果的不确定度进行评定。通过结果分析可以发现,利用固相微萃取-气相色谱联用法可对体系中痕量有效成分浓度进行测定,此方法在痕量标准物质定值中具有较高的应用价值。     

固相微萃取— 气相色谱联用法测量痕量苯不确定度的评定

通过建立数学模型,对固相微萃取—气相色谱联用法测量痕量苯的测量结果不确定度进行了评定。通过对影响不确定度的各分量进行分析,得出固相微萃取—气相色谱联用法测量痕量苯的测量结果不确定度为4. 8%。通过对各不确定度分量的分析可以得知气相色谱仪及色谱条件对测量结果的不确定度影响最大。     

HPLC测定工作场所空气中3,4-苯并(a)芘的不确定度评估

为建立高效液相色谱测定工作场所空气中3,4-苯并(a)芘的不确定度评定方法,依据JJF1059-1999《测量不确定度评定与表达》~([1])分析并识别测定过程中的不确定度的主要来源,评定结果表明不确定度主要来源工作曲线拟合,配制标准溶液和采集样品过程中,该不确定度评价方法对HPLC测定工作场所空气中3,4-苯并(a)芘的质量控制有实际意义。     

溶剂萃取/气相色谱-质谱法测定热熔胶中苯系物

目的建立一种溶剂萃取/气相色谱-质谱联用法测定热熔胶中苯系物残留量的方法。方法优化溶剂萃取条件和仪器分析条件,热熔胶样品依次经超声萃取、冷冻离心后,萃取液通过气相色谱-质谱联用法测定并得到热熔胶中苯系物的残留量,并与顶空-气相色谱/质谱法测定结果进行比较。结果采用文中方法测定了6种苯系物的线性相关系数大于0.9992,定量限为0.03~0.07 mg/kg,回收率为89.1%~103.1%。文中方法与顶空进样法对实际样品的测定结果一致,并利用文中方法对70个市售热熔胶样品进行了测定,苯检出率为4.3%,残留量低于0.18 mg/kg,甲苯、乙苯、对-二甲苯、间-二甲苯、邻-二甲苯检出率大于92.9%,其残留量在0.10~58.68 mg/kg。结论文中方法具有简单、快速、准确度高等优点,适用于热熔胶中苯系物残留量的测定。     

气相色谱-质谱法测定醋酸纤维滤棒中的苯系物

建立了气相色谱-质谱法测定醋酸纤维滤棒中苯系物的方法.样品以正戊烷萃取,用对溴氟苯作为内标,以DB-WAXetr柱分离,用选择离子方式检测,以标准加入法定性、内标法定量进行检测.方法在0.005～0.1 μg/mL范围内具有良好的线性关系,拟合度为0.992 9～0.9995,检出限为0.010～0.025 μg/g;样品的RSD≤6.1％,回收率为94.1％～96.6％.结果表明:该方法能够快速、准确地测定醋酸纤维滤棒中的苯系物.     

探讨吹扫捕集气相色谱法测定饮用水中苯系物

吹扫捕集气相色谱法测定饮用水中的苯系物无需进行萃取等繁琐的样品前处理,操作简单灵敏。本文在设定的色谱和吹扫条件下,苯系物各组分线性方程的相关系数均大于0.9990,方法检出限在0.10～0.21μg·L-1,加标回收率在97～102%之间,适用于饮用水低浓度挥发性苯系物的测定。     

固相萃取富集—高效液相色谱法分析水中多环芳烃(PAHs)

采用固相萃取与高效液相色谱联用技术,测定了水中的多环芳烃。实验中使用Supelco固相萃取过滤装置和Supelco C_(18)固相萃取小柱,100％的甲醇作为流动相。对于萤蒽(FLU),苯并(b)萤蒽(BbF),苯并(K)萤蒽(BkF),苯并(ghi)(BPer)及茚并(1,2,3-cd)芘(IP)的检测限分别为4.1,3.8,1.6,14.4,和3.8ng/L。     

超声辅助-乳化液液微萃取-气相色谱法测定水体中7种苯系物

采用正己烷为萃取剂,乙腈为乳化剂,建立超声辅助-乳化液液微萃取-气相色谱法(USA-ELLME-GC)检测水中甲苯、乙苯、对二甲苯、间二甲苯、邻二甲苯、1,3,5-三甲苯,1,2,4-三甲苯的分析方法。当萃取剂正己烷为150μL,乳化剂乙腈为400μL,超声时间为12 min时,50 m L水溶液中苯系物被成功萃取到正己烷中,富集倍数达到333倍。色谱条件为:DB-5MS(30 m×0.25 mm,0.25μm)毛细管柱,进样口温度220℃,检测器(FID)温度250℃,程序升温(初始45℃保持3 min,3°C/min升温至70℃,再以30℃/min升至200℃保持2 min),氢气流量10m L/min,尾吹气流量30 m L/min,分流比30∶1。在优化的萃取和色谱条件下,7种苯系物在0.08~1.00 mg/L浓度范围内与峰面积呈线性关系,相关系数均0.9980,方法检出限为0.005~0.01 mg/L,质量浓度均为0.10 mg/L的苯系物的7次前处理及测定结果相对标准偏差RSD为1.5%~4.7%。建立的方法应用于学校内湖水和实验室废水中7种苯系物的测定,平均回收率为86.5%~110.4%,测定结果满足分析化学痕量分析要求。     

塑料包装材料中邻苯类化合物提取方法的比较

用气相色谱-质谱法(GC-MS)测定了塑料包装材料中邻苯类化合物。比较了正己烷、二氯甲烷等提取溶剂,分别考察索式抽提、超声提取、振荡提取、微波萃取等4种提取方法和提取时间等因素,对提取塑料包装材料中16种邻苯类化合物的影响。选用了正己烷超声提取,气相色谱-质谱法分析,并选择离子扫描(SIM)定量。该方法简便、快捷、准确,适用于各类塑料包装材料中邻苯类化合物的检测。     

食品级二氧化碳中苯含量气相色谱分析方法的研究

实验采用气相色谱法分析二氧化碳中的痕量级组分气体——苯。主要影响因素有进样口温度、毛细柱温度、检测器温度、毛细柱流速、尾吹,对各项优化后测得精密度为0．2％,线性误差不大于±2％。该方法快速、准确,可应用于该标准物质的分析定值。     

壳聚糖/聚己内酯-聚乳酸多孔支架制备和表征

为调控骨组织工程支架的力学性能和降解性能,采用相分离方法,以冰醋酸-水为共溶剂配制聚合物溶液,以NaOH溶液为凝固剂,以CS为添加剂制备壳聚糖(CS)/聚己内酯(PCL)-聚乳酸(PLA)三维多孔支架,研究了聚合物质量比对支架结构、形貌、孔隙率、力学性能和降解性能的影响。实验结果表明,CS和基体存在相互作用,CS有利于形成三维相互贯通的微孔结构,但CS的存在会使基体中各组分的熔点降低。随着PCL和PLA用量比例的改变,孔径范围和微孔形貌发生了一系列的变化。当PCL∶PLA为2∶4和3∶3时,所制备的支架孔隙率均大于90%,当进一步增大PCL质量比时,孔隙率迅速下降。抗压测试表明,所制备的支架弹性模量为0.8～8.0 MPa。降解性能分析表明,4周以后,当PCL∶PLA为3∶3时,质量损失率最大,达到5.94%。该分析表明采用相分离法,通过调节PCL和PLA的质量比可制备形貌、孔隙率、降解速率和力学性能满足要求的三维多孔支架材料,有望应用在软骨组织工程上。     

Evolution in the number of authors of computer science publications

This article analyses the evolution in the number of authors of scientific publications in computer science (CS). This analysis is based on a framework that structures CS into 17 constituent areas, proposed by Wainer et al. (Commun ACM 56(8):67–63, 2013), so that indicators can be calculated for each one in order to make comparisons. We collected and mined over 200,000 article references from 81 conferences and journals in the considered CS areas, spanning a 60-year period (1954–2014). The main insights of this article are that all CS areas witness an increase in the average number of authors, in every decade, with just one slight exception. We ordered the article references by number of authors, in ascending chronological order and grouped them into decades. For each CS area, we provide a perspective of how many groups (1-author papers, 2-author papers and so on) must be considered to reach certain proportions of the total for that CS area, e.g., the 90th and 95th percentiles. Different CS areas require different number of groups to reach those percentiles. For all 17 CS areas, an analysis of the point in time in which publications with n + 1 authors overtake the publications with n authors is presented. Finally, we analyse the average number of authors and their rate of increase.     

考虑疲劳效应的伤员应急手术调度模型及算法

为了解决城市突发事件应急救援中批量应急手术的调度问题,并考虑医生长时间连续手术对手术持续时间和挽救病人生命的成功率带来的恶化效应,提出了三阶段批量手术调度模型,将应急手术调度看作是存在并行机的流水车间调度问题。利用改进的飞蛾扑火算法对应急手术模型进行求解,并通过实证来测试模型和算法的有效性。为了验证算法的性能,将经典飞蛾扑火算法、粒子群算法和布谷鸟算法与其对比,取20次运行结果,得知最大手术完成时间均值中改进的飞蛾扑火算法为最小,调度模型给出的调度方案中,3个救治阶段在时间维度上保持连贯。仿真结果表明,改进的飞蛾扑火算法能很好地求解批量手术调度模型,获得较好的调度结果。     

Characterization of collagen II fibrils containing biglycan and their effect as a coating on osteoblast adhesion and proliferation

Collagen has been used as a coating material for titanium-based implants for bone contact and as a component of scaffolds for bone tissue engineering. In general collagen type I has been used, however very little attention has been focussed on collagen type II. Collagen-based coatings and scaffolds have been enhanced by the incorporation of the glycosaminoglycan chondroitin sulphate (CS), however the proteglycan biglycan, which is found in bone and contains glycosaminoglycan chains consisting of CS, has not been used as a biomaterial component. The study had the following aims: firstly, five different collagen II preparations were compared with regard to their ability to bind CS and biglycan and the changes in fibril morphology thereby induced. Secondly, the effects of biglycan on the adhesion of primary rat osteoblasts (rO) as well as the proliferation of rO, primary human osteoblasts (hO) and the osteoblast-like cell line 7F2 were studied by culturing the cells on surfaces coated with collagen II fibrils containing biglycan. Fibrils of the collagen II preparation which bound the most biglycan were used to coat titanium surfaces. Bare titanium, titanium coated with collagen II fibrils and titanium coated with collagen II fibrils containing biglycan were compared. It was found that different collagen II preparations showed different affinities for CS and biglycan. In four of the five preparations tested, biglycan reduced fibril diameter, however the ability of a preparation to bind more biglycan did not appear to lead to a greater reduction in fibril diameter. Fibrils containing biglycan promoted the formation of focal adhesions by rO and significantly enhanced the proliferation of hO but not of rO or 7F2 cells. These results should encourage further investigation of biglycan as a component of collagen-based scaffolds and/or coatings.     

Chitosan-based membrane chromatography for protein adsorption and separation

A chitosan-based membrane chromatography was set up by using natural chitosan/carboxymethylchitosan (CS/CMCS) blend membrane as the matrix. The dynamic adsorption property for protein (lysozyme as model protein) was detailed discussed with the change in pore size of the membrane, the flow rate and the initial concentration of the feed solution, and the layer of membrane in membrane stack. The best dynamic adsorption capacity of lysozyme on the CS/CMCS membrane chromatography was found to be 15.3 mg/mL under the optimal flow conditions. Moreover, the CS/CMCS membrane chromatography exhibited good repeatability and reusability with the desorption efficiency of ~ 90%. As an application, lysozyme and ovalbumin were successfully separated from their binary mixture through the CS/CMCS membrane chromatography. This implies that such a natural chitosan-based membrane chromatography may have great potential on the bioseparation field in the future.     

Use of the cross-section technique linked with multivariate calibration methods to resolve complex pesticide mixtures

The potential of the cross-section (CS) approach in combination with the partial least squares (PLS) and principal component regression (PCR) was assessed in the resolution of a complex pesticide mixture showing twelve overlapped components in High Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD). Careful selection of the CS through the three-dimensional (3D) (A, lambda, t) data matrix gave two-dimensional (2D) signals with the best sensitivity for the determination of each pesticide. In all cases, the application of the PLS method demonstrated a better quantitative prediction ability than that of the PCR method. The CS-PLS approach is a powerful analytical tool. Ten pesticides were well-resolved, while for the other two pesticides of the mixture prediction ability was poor, and they could not be determined, probably due to their low net analytical signal. The CS-PLS model was evaluated by predicting the concentrations of independent test set samples. Finally, the proposed model was successfully applied for the determination of these pesticides in groundwater.     

Permeation studies comparing cobra skin with human skin using nicotine transdermal patches

Cobra skin (Naja Naja Khaotia) was used as a barrier for an in vitro permeation study using nicotine. Fluxes of nicotine that permeated from Nicotinell through cobra skin (CS) taken from the head, body, and tail were 233.93 +/- 16.08, 206.87 +/- 19.00, and 211.26 +/- 22.93 micrograms/cm2/hr1/2, respectively (n = 6). This indicated no significant difference (p > .05). Abdominal human epidermis (HE), obtained from cadavers, and the CS provided identical permeation kinetics for nicotine, which can be described by Mt = 4M alpha (Dt/pi L2)1/2. The mean flux of nicotine formulated as an acrylic transdermal patch that permeated through HE was 137.92 +/- 67.79 micrograms/cm2/hr1/2 (4 specimens, n = 12), whereas that through CS was 180.13 +/- 41.05 micrograms/cm2/hr1/2 (4 specimens, n = 15). The ratio of the fluxes of nicotine from formulated patches having three different nicotine contents using CS and HE was 1.22 to 1, respectively, for each of the patches irrespective of nicotine content. The coefficients of variation of the nicotine permeated were 22.79% and 49.15% for CS and HE, respectively, that is, a narrower variation of results was obtained with CS. This indicated that CS could be used for nicotine permeation studies.     

Chromatography with two mobile phases

Experimental results for the investigation of chromatographic columns containing two mobile phases are presented. The eluent was composed of mixtures of methanol and carbon dioxide. The column was an uncoated fused-silica-lined stainless steel capillary column. At certain experimental conditions, the eluent divided into two phases, both of which moved through the column. The predominant component of the liquid phase was methanol whereas the gas phase was composed of at least 93 mol % CO2. The columns were studied over a range of feed compositions (45-95 mol % CO2), pressures (61-101 bar), and temperatures (30-100 degrees C). The compositions and densities of each phase were calculated from the Peng-Robinson equation of state. The residence times of the two mobile phases were determined by tracer pulse chromatography. The partition coefficients of a probe solute, benzene, were measured along with the retention times of neon and the total volume of the chromatographic column as a function of temperature, pressure, and stoichiometric feed composition. The calculated column volumes, that is the volume of the liquid and gas, were constant over the full range of feed composition. The partition coefficient of benzene was constant at fixed pressure and temperature, varied logarithmically with density at fixed temperature and feed composition, and displayed a maximum at intermediate temperatures at fixed pressure and feed composition. The measured retention times of neon were consistently equivalent to the calculated residence times of the gas phase, indicating that neon did not dissolve in the liquid phase and could thus serve as an accurate dead time marker. The implementation of chromatography with two mobile phases produces a chromatographic "window". There is a lower limit for the retention volume of all solutes, viz., the residence time of the gas phase, exactly the same as normal chromatography. However, elimination of the stationary phase produces an upper limit to the retention volumes of solutes. This upper limit is the residence time of the liquid phase, so there is a retention window such that tG < or = ti < or = tL for all solutes.     

钛酸酯偶联剂对磷灰石/壳聚糖多孔生物材料性能的影响

以螯合型焦磷酸钛酸酯偶联剂(NDZ-311)为改性剂对壳聚糖(CS)进行改性,采用真空冷冻干燥法制备了HA-TCP/CS多孔生物材料,研究了NDZ-311的用量与多孔生物材料抗压强度和孔隙率的关系,并采用SEM、XRD、IR等对材料进行了分析测试.结果表明,NDZ-311中-O-链状醚键官能团能发生各种类型的酯基转化反应,与CS填料产生交联,材料的抗压强度得到提高,CS填料添加量可达50%以上,且不会发生相分离.随着NDZ-311含量的增加,多孔生物材料的抗压强度先逐渐降低然后升高,孔隙率先逐渐升高然后降低.当m(HA-TCP):m(CS)=7:3时,NDZ-311质量分数为1%时抗压强度为2.3MPa,孔隙率升至最高84.8%,此时多孔生物材料的抗压强度和孔隙率匹配较好,孔隙呈层错板条搭接,且分布均匀,HA-TCP颗粒均匀分散在CS模板上,材料的相结构变化不大,只是材料中各相对应的特征衍射峰的强度略有增强.