气相色谱仪检定装置的使用方法

依据JJG 700–1999《气相色谱仪检定规程》介绍气相色谱仪检定装置的使用方法。检定项目包括载气流速稳定性、柱箱温度稳定性和程序升温重复性、衰减器换挡误差以及检测器的灵敏度。给出了热导检测器(TCD)、火焰离子化检测器(FID)、火焰光度检测器(FPD)、电子俘获检测器(ECD)和氮磷检测器(NPD)检定时的色谱条件及使用注意事项。正确使用气相色谱仪检定装置能保证仪器测量数据的准确可靠。     

关于气相色谱仪检定的几个问题

在对气相色谱仪进行检定的过程中,遇到了有关色谱柱,标准样品,积分仪和色谱数据工作站数据采集等实际问题,为了既不影响生产工艺分析任务的进行,又能及时完成对仪器性能的检定工作,采取了相应的措施和办法,较快地完成了对气相色谱仪的检定,并对某些测试数据进行了比较和讨论。     

变压器油中溶解气体分析专用气相色谱仪的检定与校准

为解决检定变压器油中溶解气体分析专用气相色谱仪时遇到样品进样量计算不准,检测器对甲烷气体标准物质无响应,专用软件分析方法不能更改等问题,建立变压器油中溶解气体分析专用气相色谱仪的检定与校准方法。当进样模式为一次进样双柱分流时,按分流比计算分流到检测器的样品体积,其它进样模式按进样体积计算进样量;因色谱软件禁止积分导致CH_4在热导检测器上无响应时,应采用有证标准物质中的H_2或O_2进行检定与校准。以7890B型专用气相色谱仪为例,详细说明了变压器油中溶解气体分析专用气相色谱仪的检定与校准流程。该法为检定人员检定该类专用仪器时提供了参考。     

气相色谱仪FID检定过程中的常见故障及排除

气相色谱仪氢火焰离子化检测器（FID）检定过程中常见故障为仪器无法正常点火、仪器进样重复性差、仪器基线噪声漂移大,对这些故障原因进行了分析并提出了解决办法。     

色谱检定用测量仪研制及应用

介绍色谱检定用测量仪的工作原理、结构设计及模型建立,研制了精密温度测量电路、单片机控制电路及数据处理显示电路等,详细叙述了色谱检定用测量仪的软、硬件设计,通过实验证明了该仪器测量的准确性和可靠性。     

薄层色谱扫描仪检定方法探讨

为了解决薄层色谱扫描仪没有统一的量值溯源方法和标准装置的问题,建立薄层色谱扫描仪检定方法。通过对薄层色谱扫描仪各部分的结构进行分析,建立了薄层色谱扫描仪检定项目及计量性能要求。采用低压汞灯为标准器进行波长示值误差和重复性检定,采用薄层色谱标准板进行仪器重复性和线性检定。该检定方法能准确评价薄层色谱扫描仪的性能,为薄层色谱扫描仪的量值溯源提供技术支持。     

气相色谱仪检定结果的不确定度评定

气相色谱仪检定结果的不确定度主要来源于流速稳定性、柱箱温度稳定性、基线噪声、定量重复性和标准物质进样量的不确定度。以TCD检测器为例进行分析,对气相色谱仪检定结果的不确定度进行评定,相对扩展不确定度为5%。     

天然气气相色谱仪检定装置的建立

为了保证天然气工业用气相色谱仪分析结果准确可靠和量值溯源有效,依据JJG 1055—2009《在线气相色谱仪》、JJF1033—2016《计量标准考核规范》等规程规范要求,配置建标所需计量标准器,研究开展了重复性试验、不确定度评定、检定结果的验证等工作,建立了天然气气相色谱仪检定装置,通过了国家市场监督管理总局的现场考...     

非色散原子荧光光度计计量检定规程中相关问题的探讨

探讨了非色散原子荧光光度计检定中部分技术指标与检测方法对高灵敏度、智能化新型仪器的适应性,提出了相关修改补充建议。经实际计量检定证明行之有效,较好的解决了实际工作中遇到的无法实施或检定指标与具体检测要求不相适应的问题,保证了计量检定后仪器分析结果的准确程度与公正性。     

浅谈环境监测仪器设备的检定管理

在环境监测领域,仪器检定管理没有统一、细化、规范化的操作准则,导致检定管理水平存在较大差异。为了减小这种差异,从资料搜集,台帐建立,法定检定单位的合理选择,检定计划的制定,计量仪器的送检、验收、发放等方面,总结出一套操作性较强的管理模式,使计量工作的管理更到位,检定和监测的关系更协调,保证监测数据的准确有效。     

Calculation of tri-critical points

Procedures are presented for calculating higher order critical points in thermodynamic models. The procedures arise from an analysis of the Gibbs tangent plane criterion for phase stability. New methods are proposed for evaluating the functions that must be zero at critical points and the ease with which these functional evaluations can be carried out is the major element in permitting calculation of higher order critical points in mixtures of any number of components. Comparison is made between experimental data and tri-critical points for ternary mixtures as calculated with the Peng-Robinson and SRK equations.     

Triple points and plutonium equilibrium

Summary Equilibrium prevails at all points in plutonium predominance region diagrams. Triple points combine equilibrium with equal fractions of three Pu oxidation states. A rearrangement equation can be used to describe plutonium at a triple point. Two-reaction-product disproportionation equations are not satisfactory for that purpose.     

Melting points of lanthanide trichlorides

The melting temperatures and absolute values of melting enthalpies of lanthanide trichlorides decrease from LaCl₃to TbCl₃and then increase to LuCl₃. The preceding decrease cannot be explained by the lattice energies of the trichlorides, since they increase continuously from the lanthanum to the lutetium compounds. However, it may be attributed to the structural features of the liquid state. The liquids near the melting points consist of clusters of complex units, which become larger with decreasing radii of the metal ions. To prove this assumption additional quantitative investigations are necessary.     

Saturation points of specified entropy

A new algorithm to find the saturation conditions of a pure substance or mixture of specified entropy is proposed. An interesting aspect is that the type of saturation point, whether a dew or bubble point, is a priori unknown. This poses particular challenges to providing good initial estimates that ensure numerical convergence of the phase equilibrium equations. A safe initialization procedure is proposed. The examples show applications of the model to computations with pure methane, pure carbon dioxide, natural gas, and contaminated carbon dioxide. The algorithm succeeds in determining the saturation condition in all of these cases.     

The melting points of oligomethylenes

Quantitative structure-property relationships (QSPR) between the melting points of oligomethylenes and quantum chemical data calculated by the semiempirical method CNDO/2 were investigated. A linear relationship between the average net charges of hydrogen and carbon atoms in the molecules and the melting points could be established, achieving good fit as well as predictability. Further, the relation between the net charges and the chain length was evaluated. The evaluated net charges of polyethylene lead to a calculated melting point of 141.4°C (experimental: 141.4°C). © 1996 John Wiley & Sons, Inc.     

QSPR-modeling of oligophenylene melting points

QSPR-modeling of melting temperatures has been performed for oligophenylenes of diverse structures and different molecular weights. It has been shown that optimization of correlation weights of graph local invariants can be used for prediction of melting points of oligomers. The best statistical quality of the model is observed for correlation weights calculated using third-order Morgan degrees.     

The melting points of chain polymers

The molecular characteristics which determine the melting points of high polymer crystals are considered, and it is shown that the properties of monomeric crystals often throw light on those of the polymers. The principal factors controlling melting points appear to be molar cohesion energy (of the whole molecule for monomers, or per chain unit for polymers), molecular flexibility (due to rotation round bonds), and molecular shape effects. Figures for the cohesion energy increments of a number of chain units and substituent groups are given, and melting points of polymer series are correlated with cohesion energy per chain unit. The flexibility factor is less easy to assess; barriers to rotation in appropriate monomer molecules are relevant, but available data are very rough. The approach therefore is mainly by empirical and comparative methods. When plotted against cohesion energy per chain unit, the melting points of various series of aromatic polyesters and polyurethans fall within the same band, while those of the polyamides lie on the whole higher and those of the aliphatic polyesters, polyethers, polythioethers and polydisulfides much lower. The differences are attributed to difference of molecular flexibility arising from the presence of easily rotating O?C, S?C and S?S bonds. The low melting points of rubber and other unsaturated polymers are attributed to the fact (which can now be regarded as definitely established by independent evidence) that rotation round single bonds which are adjacent to double C? C bonds is easier than in saturated chains. Easily rotating bonds which are inclined to each other, as in cis isomers, confer greater chain flexibility than the parallel bonds in trans isomers, and thus lead to lower melting points. The marked odd-even effects in saturated molecules which run through the whole of organic chemistry (the even members always melting higher than the odd) are attributed to similar effects arising from the fact that the end bonds of an odd CH₂ sequence are inclined to each other while those at the ends of an even sequence are parallel.