فهرست مطالب

دانش آزمایشگاهی ایران - سال یکم شماره 1 (پیاپی 13، بهار 1395)

مجله دانش آزمایشگاهی ایران
سال یکم شماره 1 (پیاپی 13، بهار 1395)

  • 40 صفحه،
  • تاریخ انتشار: 1395/03/20
  • تعداد عناوین: 7
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  • Marzieh Rezaei, Maryam Yousefi, Mahmoud Naderi Page 5

    Liquid Chromatography-Mass Spectrometry (LC-MS) is an analytical chemistry laboratory technique for identification, quantitation and mass analysis of materials. This technique allows for the structural elucidation of unknown molecules through fragmentation. Similar to HPLC, LC/MS utilizes a compound's intrinsic affinity for both a "mobile phase" and a "stationary phase". Once the sample is in the solvent flow, it travels through an analytical column. The compounds present in the sample mixture are then separated depending on their affinity to the coated particles in the column. After the components in the sample are separated, they pass through a mass detector. Three ionization types are available for sample analysis, Electrospray Ionization (ESI), Atmospheric Pressure Chemical Ionization (APCI) and Atmospheric Pressure Photo Ionization (APPI). Both ESI and APCI are similar in that the ionization of the analyte(s) of interest occurs at atmospheric pressure. The differences between the two techniques lie in the way the analyte(s) of interest are ionized. The m/z analyzer (mass analyzer) is used to separate the ions according to their m/z ratio based on their characteristic behavior in electric and/or magnetic fields. More specifically, quadrupoles, quadrupole ion traps and time-of-flight (TOF) s have undergone numerous modifications and improvements over the past decade in order to be interfaced with ESI.

    Keywords: Liquid Chromatography-Mass Spectroscopy(LC-MS), Ion Sources, Mass Analyzers
  • Fatemeh Khakrah, Sedigheh Sadeghhassani, Samira Sadat Mirjalili, Azar Khazaiepoor Page 13

    Piezoresponse force microscope (PFM) is a kind of atomic force microscope that allows imaging of new ferroelectric domains with a few nanometers lateral resolutions. Various types of PFM are made that considerably influenced the measurements at the nanoscale. In this paper, the advanced PFM modes and some of the limitations of conventional methods and their solutions are introduced.

    Keywords: Piezoresponse force microscopy, piezoelectric, domain, imaging
  • Maryam Khaninour, Behnaz Kaveh, Roghayeh Zabihi Page 20

    Obtained information is from X-rays by energy or wavelength of them, according to that two type of X-ray detection system will be: EDS system as the energy dispersive spectrometer and the WDS system as the wavelength dispersive spectrometer.EDS systems often use different types of semiconductor detectors, such as Si (Li), HPGe and SDD, on the other hand detectors used in WDX usually are gas detectors such as proportional counters or scintillation detectors. Although the performance of the detectors and X-ray detection is quite different, but the ultimate goal in both types of spectroscopy is detection energy or wavelength of characteristic X-ray emitted and elemental analysis in the desire sample in scanning electron microscopy.

    Keywords: Scanning electron microscope, Energy DispersiveSpectroscopy, Wavelength DispersiveSpectroscopy, Semiconductor Detector, GasDetector, Scintillation Detector
  • Fatemeh Sharifi Aref, Azar Khazaee Pour Page 28

    Several definitions have been provided for the calibration of national standards in section "General metrology" calibration is defined as: comparison with a standard reference laboratory instrumentation under standard conditions to ensure the accuracy and integrity, and determining the error rate by compared to the standard and set the standard. In fact create effective system calibration parameters to control the accuracy of instruments and test devices, measuring instruments and all equipment that affects their performance on the quality of that in order to ensure the implementation of international standards used measurements. Control and maintenance of process measurement done by the measuring device is required. Usually by uncertainty over time and with repeated use increases. Identify the gradual growth and increased uncertainty it easily possible unless underwritten by users. The ultimate goal of establishing calibration traceability as measurement and control system has been in international trade is essential. Traceability is: Ability to communicate the result of a measurement standard or a national and international reference, through a continuous chain of comparisons, all of which have certain uncertainty in national or international event or marked.

    Keywords: Calibration, Standard, Metrology, Measurement