共查询到19条相似文献,搜索用时 625 毫秒
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主要介绍了原子荧光分光光度计检定/校准的过程中常见故障,如联机故障、载气故障、点火故障和自动进样器故障等,针对无信号强度、荧光强度偏低、空白强度较高、仪器不稳定和重复性较差、线性不好等常见问题进行剖析并提出相应解决方法,根据工作经验和仪器工作原理提出了原子荧光光度计检定/校准过程中仪器参数和溶液配制方法。 相似文献
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介绍了化学测量仪器的分类、特点、检定/校准的必要性及化学计量检定/校准的现状,分析了化学计量标准的特点、探讨了化学计量最高标准的划定和考核的在关问题。 相似文献
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JJG 395–1997《定碳定硫分析仪检定规程》中的部分技术要求和检定项目已不能满足现代碳硫分析仪器检定/校准的要求。对规程的适用性、称量稳定性、示值误差、标准物质、重复性、分析时间等进行了探讨,并给出了修订建议。探讨了评定仪器检测空白的可能性,提出了依据碳硫测定基准国标方法的仪器检定/校准方法,以评定不同用途的测试仪器,并扩展了仪器检定/校准的范围。为计量部门修订规程提供参考,同时也为实验室合理评价,验收碳硫分析仪,及时掌握仪器的运行状况,保证分析数据的准确性、一致性和溯源性提供借鉴。 相似文献
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Temperature calibration of DSCs is usually carried out on heating. In order to accurately control the temperature during cooling experiments, the calibration has to be carried out on cooling. Therefore, three high-purity, thermally stable liquid crystals were used to perform a temperature calibration of an electrcial compensation DSC on cooling. All three liquid crystals have several liquid crystalline phases, and they all were purified to a 99.9% lovel. Temoperatures of the isotropic to nematic or cholesteric and the mesophase to mesophase transitions were used. It was verified that these liquid crystals have sufficient thermal stability for carrying out the calibration on cooling. The dependence of the real temperature on the indicated temperature has been established for all the combinations of the heating and cooling rates of practical interest. It is also shown that the vant's Hoff equation can only be applied to the crystal to a liquid crystal transition, but not to the liquid crystal to liquid crystal or liquid crystal to isotropic transitions. 相似文献
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In this paper, it is made a study of the accuracy of an isothermal titration calorimeter in the operating mode of ‘continuous
injection’. The experimental equipment has been a TAM2277-201/2250 by Thermometric AB and the liquid mixtures used in the
calibration have been the mixture cyclohexane+benzene and the mixture water+ethanol. The calibration contemplates different
effects that affect the uncertainty in the determination of the sensitivity, the effect of the liquid injection, the treatment
of the calorimetric signal, the variation of the experimental baseline and the different noises included in the calorimetric
signal. 相似文献
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利用研制的三通道渗透管装置发生摩尔分数范围为0.1~1.0μmol/mol的硫化氢、甲基硫醇、二甲基硫醚混合气体,用于校准检测口腔气体检测仪。校准装置可以在固定输出总流量不变的情况下,快速改变发生硫化物的摩尔分数。对校准装置的温控系统和流量系统进行了测试,通过总硫分析仪对校准装置发生的低含量硫化物的量值进行了比较和验证。该校准装置发生的低含量硫化物量的相对扩展不确定度不大于6.8%(k=2)。 相似文献
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The temperature calibration on cooling of thermal analysis instruments is important for the accurate study of the non-isothermal crystallization kinetics of semi-crystalline polymers. In previous works, a methodology was proposed for performing the calibration on cooling of differential scanning calorimeters (DSCs) with standard metals, and the calibration errors were checked using transitions of high-purity liquid crystals. In this work, alternative, physically meaningful, procedures for carrying out the calibration on cooling are analyzed and validated. The calibration errors are evaluated also with liquid crystalline transitions, when the calibration is performed with standard metals, in a wide temperature range, and when due account is taken for the need of isothermal corrections to the temperature measurements. It is shown that any pair of standard metals may be used to calibrate on cooling, that the calibration errors increase for wider working temperature ranges and that, providing that certain conditions are fulfilled, both calibration procedures yield similar results. 相似文献
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Sarah K. Himes Marta Concheiro Karl B. Scheidweiler Marilyn A. Huestis 《Analytical and bioanalytical chemistry》2014,406(7):1945-1955
Presence of fatty acid ethyl esters (FAEE), ethyl glucuronide (EtG), and ethyl sulfate (EtS) in meconium, the first neonatal feces, identifies maternal alcohol consumption during pregnancy. Current meconium alcohol marker assays require separate analyses for FAEE and EtG/EtS. We describe development and validation of the first quantitative liquid chromatography tandem mass spectrometry assay for 9 FAEEs, EtG, and EtS in 100 mg meconium. For the first time, these alcohol markers are analyzed in the same meconium aliquot, enabling comparison of the efficiency of gestational ethanol exposure detection. 100 mg meconium was homogenized in methanol and centrifuged. The supernatant was divided, and applied to two different solid phase extraction columns for optimized analyte recovery. Limits of quantification for ethyl laurate, myristate, linolenate, palmitoleate, arachidonate, linoleate, palmitate, oleate, and stearate ranged from 25–50 ng/g, with calibration curves to 2,500–5,000 ng/g. EtG and EtS linear dynamic ranges were 5–1,000 and 2.5–500 ng/g, respectively. Mean bias and between-day imprecision were <15 %. Extraction efficiencies were 51.2–96.5 %. Matrix effects ranged from ?84.7 to 16.0 %, but were compensated for by matched deuterated internal standards when available. All analytes were stable (within ±20 % change from baseline) in 3 authentic positive specimens, analyzed in triplicate, after 3 freeze/thaw cycles (?20 °C). Authentic EtG and EtS also were stable after 12 h at room temperature and 72 h at 4 °C; some FAEE showed instability under these conditions, although there was large inter-subject variability. This novel method accurately detects multiple alcohol meconium markers and enables comparison of markers for maternal alcohol consumption. Figure
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R. J. Sengwa Abhilasha N. M. More S. C. Mehrotra 《Journal of Polymer Science.Polymer Physics》2005,43(9):1134-1143
Dielectric studies of poly(vinyl pyrrolidone)/ethyl alcohol (PVP–E) binary mixtures with concentration variations were carried out in the frequency range of 10 MHz to 10 GHz by time domain reflectometry at 15, 25, 35, and 45 °C. One relaxation process, corresponding to ethyl alcohol molecules in the poly(vinyl pyrrolidone) (PVP) matrix, was observed in this frequency range for all the mixtures. The static dielectric constant of the PVP–E mixtures decreased linearly with an increase in the weight fraction of PVP. The observed anomalous increase in the value of the relaxation time (τ) of these mixtures was interpreted by the consideration of the variation in the local structure of self‐associated ethyl alcohol molecules and also the PVP behavior as a geometric constraint for the rotational motion of ethyl alcohol molecules. Furthermore, the τ values of these mixtures were independent of the viscosity. The energy parameters for the dielectric relaxation process (the free energy, enthalpy, and entropy of activation for the dipolar orientation) were determined to confirm the transient behavior of the heterogeneous species due to the breaking and re‐forming of hydrogen bonds with the internal rotation of ? OH groups in the ordered structure of the PVP–E mixtures. On the basis of the evaluated dielectric parameters, the formation of supermolecular structure in the PVP–E mixtures in dynamic equilibrium was sketched and examined by the consideration of the hydrogen bonding between the terminal hydroxyl groups of self‐associated ethyl alcohol flexible chains and the carbonyl groups of monomer units of PVP coiled chains. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1134–1143, 2005 相似文献