惰气熔融-热导法测定钕铁硼永磁材料中的氢

建立惰气熔融-热导法测定钕铁硼永磁材料中氢的分析方法。当氧-氢比例大于50:1时,CO对氢的测定结果产生一定的干扰,加入舒茨试剂可消除此干扰。采用标准坩埚,称样0.05g,熔融功率为2.85 kW,选择高纯镍篮和锡片做助熔剂,钕铁硼中氢释放完全。以普通钢铁参考物质建立氢校准曲线,线性相关系数r～2=0.9999,检出限为0.75μg/g。该法用于钕铁硼样品中氢的测定,测定结果与脉冲熔融飞行时间质谱-气体元素分析仪测定结果基本一致,测定结果的相对标准偏差为1.4%(n=5)。该方法可以准确测定钕铁硼永磁材料中的氢,能满足日常分析的要求。     

脉冲熔融-红外/热导法测定钛合金粉末微注射成形脱脂坯中氧氮氢

准确测定钛合金粉末微注射成形脱脂坯中氧氮氢含量对钛合金的粉末微注射工艺改进有很大指导作用。采用工业镍板经过表面打磨、酸洗、加工成固定质量的镍粒来代替市售的镍助熔剂,通过自制镍粒预先加入设备预脱气减少空白影响的方式建立了脉冲熔融-红外/热导法测定钛合金粉末微注射成形的脱脂坯中氧氮氢含量的方法。试验表明：镍粒助熔剂与石墨坩埚经二次脱气,可确保镍粒助熔剂的空白降至极低值以代替市售的镍篮、镍屑等助熔剂。钛合金粉末微注射成形脱脂坯采用振动磨形式加工至80目以下,镍粒的加入量为1.5 g,分析功率为5300 W时,可以获得稳定准确的结果。采用实验方法对脱脂坯实际样品进行测定,其相对标准偏差(RSD,n=6)分别为0.08%~0.47%、0.2 %~1.32%和1.6 %~2.02%;采用加入钛合金标准样品进行加标回收试验,氧氮氢回收率分别在 99%~10%、97%~99%及 97%~ 103%之间。方法满足脱脂坯中的氧氮氢快速检测要求的同时极大降低了分析成本。     

基于脉冲加热-红外吸收/热导法测定烧结氮化硅陶瓷材料中晶格氧含量

基于脉冲加热-红外吸收/热导法,比较分析了恒定式、斜线式及阶梯式3种功率控制升温模式在烧结氮化硅陶瓷材料氧氮含量测定中的特点。优化后选择阶梯式功率控制升温模式并设置合理的分析参数,获得了分离良好的氧氮分量峰。结合在脉冲加热熔融样品过程中特定点位取样的X射线衍射物相分析,确定了烧结氮化硅材料的晶格氧分量峰位置及含量。测试得出Yb₂O₃做助剂的烧结氮化硅陶瓷晶格氧含量为0.094%,相对标准偏差为1.6%,与此材料的热导率水平(88.61 W/m·K)相符合。本方法适用于多种非氧化物陶瓷材料中晶格氧含量的测定。     

脉冲加热-红外吸收光谱法测定钒铝合金中氢

对脉冲加热-红外吸收法测定钒铝合金中氢的分析方法进行了研究。通过实验对分析功率、称样量和校正标样等测试条件进行了讨论。实验表明钒铝合金中的氢易释放,对于AlV85样品中氢,热提取法和熔融法测定结果一致;但AlV50样品中氢,热提取法的结果略高于熔融法,故实验中选用热提取法测定钒铝合金中氢量。热提取法用0.75g金属锡作助熔剂,于4.0kW分析功率条件下测定钛标准样品中氢来确定氢工作曲线的校正系数,在1.5kW分析功率下测定钒铝合金中氢,测定结果与高频感应-热导法(用5g钢标准样品对氢的测定进行校正)结果吻合。对3个钒铝合金中氢量进行了测定,结果的相对标准偏差为2.2%～6.5%(n=8)。     

惰气熔融-红外吸收/热导法同时测定无烟煤中氮和氢

首次使用惰气熔融-红外吸收/热导法实现无烟煤中氮、氢元素的同时、快速、准确测定.探究分析条件,发现当称样量为0.030 0 g,分析功率为5 500 W,氮元素的积分延迟时间为15 s,集成时间为55 s,氢元素的积分延迟时间为5 s,集成时间为85 s,且使用石墨套埚时,氮氢元素的释放最完全、合理.方法中氮、氢校准曲线的相关系数分别为0.994 9、0.994 0,检出限分别为0.321%、0.189%,定量限分别为0.326%、0.194%,精密度分别为3.60%、0.63%,满足线性关系及方法要求.惰气熔融-红外吸收/热导法重复性好、高效便捷、操作和维护简单,可用于无烟煤中氮、氢元素的定量检测.     

惰性气体熔融-红外/热导法测定二硼化钛增强铝基复合材料粉中氧、氮

建立惰性气体熔融-红外/热导法测定增材制造用TiB_2增强铝基复合材料粉中氧和氮含量的分析方法。采用单因素法,对仪器功率、助熔剂种类和称样量等实验条件进行优化选择。以镍箔-镍篮为空白样品,以11次空白样品测定结果标准偏差的3倍作为检出限,计算得氧、氮检出限分别为0.000 8%、0.001 0%。实际样品测定结果的相对标准偏差均小于5%(n=7),氧、氮的加标回收率为95.8%～106.6%。该方法操作过程简单,满足TiB_2增强铝基复合材料粉中氧、氮元素含量的测定要求。     

粉状铝中氧的测定

测定铝中氧的经典方法是高频加热的真空熔融法和惰气熔融法,但尚存在一些问题;脉冲加热惰气熔融法极少报导,应引起重视。作者采用脉冲加热惰气熔融-库仑定氧仪探讨了粉状铝中氧的测定方法。粉状铝在空气中易氧化生成稳定的Al_2O_3薄膜。根据热力学理论推算结果和实验结果,确定了下述提取粉状铝中氧的机理:     

惰气脉冲熔融热导法测定铌钛合金中氢含量

为准确测定铌钛合金中氢含量,使用LECO-404氢分析仪,采用惰性气氛脉冲加热熔融试样,热导法测定。研究了不同的脱气功率对空白值和试样分析值的影响,选择了脱气功率为4 500 W。通过助熔剂实验,选择了0.50g锡作为铌钛合金中氢释放的助熔剂。验证了钛标准样品的适用性。确定了分析功率为3 500 W,最短积分时间为60s。精密度实验中氢含量测定的相对标准偏差(RSD)为2.5%~5.5%,加标回收率为97.82%~104.5%,可以准确测定铌钛合金中氢含量。研究结果对准确测定铌钛合金中氢含量具有指导意义。     

氢化钛中氧的分析方法研究

氢化钛中氢的理论含量可达4％。本文将着重探讨大量氢存在下,对氧测定的影响,以及为了克服这种影响,采用了事先真空加热预处理氢化钛试样的方法。建立了高频加热惰气熔融测定氢化钛中氧的分析方法。实验部分 (一)高含量氢对氧测定的影响试验表明,采用高频加热惰气熔融库仑滴定法测定氢化钛中氧时,随着试样重量的增加,亦即试样中含氢量的增加,测得氧含量明显地偏低。为了观察氢含量对氧测定的实际影响,将氢化钛试样在高真空下,用不同温度加热处     

氧、氮、氢分析仪校准方法探讨

建立了氧、氮、氢分析仪的校准方法,介绍了氧、氮、氢分析仪的工作原理、校准要求、校准用标准物质.以北京纳克分析仪器有限公司生产的ON-3000氧氮分析仪和H-3000氢分析仪作为校准对象,对校准方法进行了验证.该方法已作为评价氧、氮、氢分析仪的依据并得到认可.     

鲁米诺-H2O2体系化学发光对邻氯代苯亚甲基丙二腈和丙二腈的研究

基于鲁米诺-过氧化氢体系对邻氯代苯亚甲基丙二腈(CS)和丙二腈的化学发光的检测,考察了其反应动力学曲线,详细研究了pH值,鲁米诺浓度,过氧化氢浓度,本底信号的稳定性对化学发光强度的影响.CS的检测线性范围为10-2～10-5mol/L,绝对检测限为1.1ng(S/N=3/1).丙二腈的检测线性范围为10-3～10-6mol/L,绝对检测限为0.5ng(S/N=3/1).建立了鲁米诺-过氧化氢体系对液相化学发光对CS和丙二腈的分析方法,对CS的沙土样品进行测定,结果令人满意.     

Simultaneous determination of oxygen, nitrogen and hydrogen in metals by pulse heating and time of flight mass spectrometric method

The inert gas fusion and infrared absorption and thermal conductivity methods are widely used for quantitative determination of oxygen(O), nitrogen(N) and hydrogen(H) in metals. However, O, N and H cannot be determined simultaneously with this method in most cases and the sensitivity cannot meet the requirement of some new metal materials. Furthermore, there is no equipment or method reported for determination of Argon(Ar) or Helium(He) in metals till now. In this paper, a new method for simultaneous quantitative determination of O, N, H and Ar(or He) in metals has been described in detail, which combined the pulse heating inert gas fusion with time of flight mass spectrometric detection. The whole analyzing process was introduced, including sample retreatment, inert gas fusion, mass spectral line selection, signal acquisition, data processing and calibration. The detection limit, lower quantitative limit and linear range of each element were determined. The accuracy and precision of the new method have also been verified by measurements of several kinds of samples. The results were consistent with that obtained by the traditional method. It has shown that the new method is more sensitive and efficient than the existing method.     

Detection of hydrogen peroxide in rainwater based on Mg-Al-carbonate layered double hydroxides-catalyzed luminol chemiluminescence

Using a green catalyst of luminol chemiluminescence (CL), Mg-Al-carbonate layered double hydroxides (denoted as Mg-Al-CO(3) LDHs), a novel, sensitive and rapid CL method was developed for the determination of hydrogen peroxide (H(2)O(2)). The corresponding linear regression equation was established in the range of 0.05-10 μM for H(2)O(2). The detection limit (S/N = 3) is 0.02 μM and the relative standard deviation (RSD) for nine repeated measurements of 1.0 μM H(2)O(2) was 2.9%. This proposed method has been successfully applied to detect H(2)O(2) in rainwater samples with good accuracy and precision. The novel methodology is expected to provide a general protocol for the determination of H(2)O(2) as well as for numerous other oxidase-based reactions giving H(2)O(2) as a product (e.g., glucose).     

Reveal E. coli 2.0 method for detection of Escherichia coli O157:H7 in raw beef

Reveal E. coli 2.0 is a new lateral-flow immunodiagnostic test for detection of E. coli O157:H7 and O157:NM in raw beef trim and ground beef. Compared with the original Reveal E. coli O157:H7 assay, the new test utilizes a unique antibody combination resulting in improved test specificity. The device architecture and test procedure have also been modified, and a single enrichment protocol was developed which allows the test to be performed at any point during an enrichment period of 12 to 20 h. Results of inclusivity and exclusivity testing showed that the test is specific for E. coli serotypes O157:H7 and O157:NM, with the exception of two strains of O157:H38 and one strain of O157:H43 which produced positive reactions. In internal and independent laboratory trials comparing the Reveal 2.0 method to the U.S. Department of Agriculture-Food Safety and Inspection Service reference culture procedure for detection of E. coli O157:H7 in 65 and 375 g raw beef trim and ground beef samples, there were no statistically significant differences in method performance with the exception of a single internal trial with 375 g ground beef samples in which the Reveal method produced significantly more positive results. There were no unconfirmed positive results by the Reveal assay, for specificity of 100%. Results of ruggedness testing showed that the Reveal test produces accurate results even with substantial deviation in sample volume or device incubation time or temperature. However, addition of the promoter reagent to the test sample prior to introducing the test device is essential to proper test performance.     

MCM-56分子筛催化苯与丙烯液相烷基化反应性能

在晶化釜内动态水热合成了MCM-56分子筛, 采用过氧化氢回流处理方法脱除模板剂, 获得了高比表面积分子筛MCM-56[MCM-56(H2O2)]. 采用XRD, N2气吸附-脱附, NH3-TPD和FTIR等对其结构和酸性进行表征, 考察了HMCM-56(H2O2)分子筛在苯与丙烯液相烷基化合成异丙苯中的催化性能. 研究结果表明, 过氧化氢回流处理能够有效去除模板剂. 与焙烧去除模板剂的HMCM-56(C)相比, HMCM-56(H2O2)分子筛的BET比表面积达到563 m2/g, 外表面积提高近2倍. 酸性表征说明, 与HMCM-56(C)相比, HMCM-56(H2O2)的总酸量较高而酸强度分布不变. 在苯与丙烯液相烷基化反应中, HMCM-56(H2O2)分子筛表现出更好的低温活性和更高的异丙苯选择性.     

阻抑动力学光度法测定痕量邻苯二酚的研究

在硫酸介质中,Ｃｕ（Ⅱ）能催化Ｈ２Ｏ２氧化偶氮胂（Ⅰ）的褪色反应,但加入邻苯二酚后,邻苯二酚能灵敏地阻抑该氧化褪色反应。作者研究了该阻抑褪色反应的动力学条件,从而建立了一种新的测定痕量邻苯二酚的方法。该法的测定范围为０．０～２００ｎｇ／Ｌ,检出限为９０．７ｎｇ／Ｌ。用于实验样品中邻苯二酚的测定,获得了满意的结果。     

Mixed hemimicelles solid-phase extraction based on cetyltrimethylammonium bromide-coated nano-magnets Fe3O4 for the determination of chlorophenols in environmental water samples coupled with liquid chromatography/spectrophotometry detection

Mixed hemimicelles solid-phase extraction (SPE) based on cetyltrimethylammonium bromide (CTAB)-coated nano-magnets Fe3O4 was investigated for the preconcentration of four chlorophenols (CPs) in environmental water samples prior to HPLC-spectrophotometry determination in this paper. By the rapid isolating (about 5 min) of Fe3O4 nanoparticles (NPs) through placing a Nd-Fe-B strong magnet on the bottom of beaker, the time-consuming preconcentration process of loading large volume sample in conversional SPE method with a column can be avoided. The unique properties of Fe3O4 NPs such as high surface area and strong magnetism were utilized adequately in the SPE process. This novel separation method produced a high preconcentration rate and factor. A comprehensive study of the adsorption conditions such as the Fe3O4 NPs zeta-potential, CTAB added amounts, pH value, standing time and maximal extraction volume was also presented. Under optimized conditions, four analytes of 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (TCP) and pentachlorophenol (PCP) were quantitatively extracted. The method was then used to determine four CPs in five real environmental water samples. High concentration factors (700) were achieved for each of the analytes, with observed detection limits ranging between 0.11 and 0.15 microg L(-1). The accuracy of method was evaluated by recovery measurements on spiked samples. Good recovery results (83-98%) with satisfactory relative standard deviation (RSD) were achieved. It is important to note that satisfactory preconcentration factors and extraction recoveries for the four CPs were obtained with only a little amount of Fe3O4 NPs (0.1g) and CTAB (60 mg). To the best of our knowledge, this was the first time a mixed hemimicelles SPE method based on Fe3O4 NPs magnetic separation had been used for the pretreatment of environmental water samples.     

化学法快速测定铁基非晶合金中硼含量的试样分解方法研究

用化学法测定铁基非晶合金中硼元素时,因合金试样难溶性及硼的某些特性,存在试样分解难的问题。利用H2O2强氧化性及硼既溶于酸又溶于碱的性质,通过试验确定了用H2O2(30%)与HCl(密度约1.19g/mL)分解试样,试样溶解完全。将该方法用于测定硼质量分数大于0.5%的铁基非晶合金中的硼,测定结果与ICP-AES法测定结果相符,测定结果的相对标准偏差小于1.5%(n=10)。     

脉冲流光放电激发解离H2O分子的动力学过程

采用色散荧光光谱、时间分辨光谱和空间分辨光谱方法, 在标准大气压(1.013×10⁵ Pa)下, 对以N2气为载气的H2O蒸气脉冲流光放电等离子体激发解离反应动力学过程进行了实验研究. 将所得色散荧光谱归属于N2(C3∏u→B3∏g)、·OH(A2∑+→X2∏)、H(n=3→n=2)的辐射跃迁; 并对N2*、·OH*、H*三种活性粒子的指纹灵敏谱线(337.2、308.4、656.5 nm)荧光信号进行了时间分辨测量. 结果表明,·OH*和H*荧光信号分别滞后N2*荧光信号7.4 ns 和17.6 ns, 由此推断H2O分子的激发解离通道为: H2O分子与高能电子发生非弹性碰撞激发, 被激发到第一激发电子态的高振动能级, 然后自解离成激发态的·OH*自由基和基态的H原子. 空间分辨测量结果表明, 在距负电极0.5 mm附近, 活性荧光粒子浓度最高, 正好对应流光放电的负辉区, 该区域电子温度和电子浓度最高, 更有利于活性粒子的产生.