By Emil W. Ciurczak, Contributing Editor In fact, when HPLC is used for analysis of dosage forms, the spectrum of the analyte, combined with the retention time, may be used as the “specificity” portion of the analysis. HPLC has also been incorporated (since the 1980s) as a process technique in bioprocessing. Eli Lilly was a pioneer in the field, using LC on-line to monitor the formation and purification of insulin. The earliest process equipment was designed and built by Lilly for this work. While LC is not instantaneous, several minutes is, in effect, real-time when a process (especially a biological-type) takes days. In the 20+ years since its inception, process HPLC has come a long way. While fluorescence spectra resemble vibrational spectra, they are considered electronic because of the mode of their mechanism. Energy (in the form of photons) is absorbed, causing the electrons to become excited and move to a higher level. The electron excitation depends on the incident light (higher light flux causes higher peaks) while the emitted light can be strongly influenced by the matrix and temperature. Emitted photons may be reabsorbed or the excited electrons may interact with solvent at higher temperatures and not emit a photon at all. However, unlike the very simple UV and visible spectra, fluorescence spectra are “rich.” That is, they contain many more peaks and give more structural information than are seen in either visible or ultraviolet spectra. Since the mechanism of fluorescing is “multidirectional,” the detectors are placed perpendicular to the incident light. Thus, unlike UV/Vis, small absorbances (followed by emission) and not the total ouput of the light source are seen against a “dark” background. This allows for detection of trace amounts of analyte. Where applicable, these monitors (grating or filter) can give molecular information with little interference from the
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Spectrometers are analytical instruments which disperse an emission (such as particles or radiation) according to some property of the emission (such as mass or energy) in order to measure the amount of the dispersion. This product area includes Portable / Miniature
, visible, infrared (IR), ultraviolet (UV), atomic absorption (AA), optical emission (OE), Raman, X-ray fluorescence (XRF) and mass spectrometers. Specific search forms are also available.
High performance liquid chromatograph (HPLC) detectors pass a beam of light through a column effluent as the fluid passes through a low-volume flow cell. Variations in light intensity are recorded and a chromatograph is generated.
High Performance Liquid Chromatographs (HPLC)
High performance liquid chromatographs (HPLC) use a liquid mobile phase to separate the components of a mixture. The components are dissolved in a solvent and forced to flow through a chromatographic column under high pressure.
UV and Visible Spectrometers
UV and visible spectrometers measure the amount of ultraviolet (UV) and visible light transmitted or absorbed by a sample placed in the spectrometer.
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By Emil W. Ciurczak, Contributing Editor Process analytical technology (PAT) and Quality by Design (QbD) have engendered an era of scientific growth and experimentation within the pharmaceutical...
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2.8 Electron Energy Loss Spectroscopy of Nanoparticles
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2.4 QUANTUM INTERFERENCE
Consider an atom with only one electron at the outer orbit [e.g., Sodium (Na)] and
on the lowest energy level or state S1. Then, when a photon of energy E12 is...
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