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METEORMETRICS LIMITED

Specialising in custom-designed, precision scientific instruments, built, programmed and calibrated to the most exacting standards. The range includes precision dataloging barographs, with built-in statistical analysis, Barographic Transient Event Recorders and computer-interfaced detectors and sensors for environmental monitoring & process control.

DrKFS.net

A site dedicated to scientific techniques, experimental methods, & investigative tools for the inventor, researcher and laboratory pioneer. Articles on glassblowing, electronics, metalcasting, magnetic measurements with new material added continually. Check it out! www.drkfs.net

THE SPECTRO-PAEDIA

click on any item in the list for its wikipedia entry if available.


absorbance
adsorption
Atomization
bandwidth
Beamsplitters
bioluminescence
chemiluminescence
chromatography
electroluminescence
electromagnetic
emission
Emissivity
Fluorescence
luminescence
Michelson
monochromators
photo-multiplier
Phosphorescence
photodiodes
photoelectric
photoluminescence
Rayleigh
Raman
spectrofluorometer
spectrometer
spectrophotometer
Spectrum
Transmittance
ultraviolet
Visible
wavelength
Wavenumber
UV Light
Beer's Law
Diode Array
Deuterium Discharge Lamp
Low Pressure Zinc Discharge Lamp
High Pressure Mercury Discharge Lamp
Low Pressure Cadmium Lamp
Tungsten Halogen Lamp
Lens and Window Material in Spectrometers
Cuvettes
Luminescence
Photoluminescence
Fluorescence
Phosphorescence
Bioluminescence
Radioluminescence
Electroluminescence
Fluorescence Reagents
Spectrum
Diffraction Grating
Interferogram
Fourier Transform IR Spectrometer
FT-IR
Halide Disks
Mull Samples
Film Samples for IR Spectroscopy
Light Pipes
Attenuated Total Reflectance Spectroscopy
Multiple Internal Reflectance
External Reflectance
Specular Reflectance
Diffuse Reflectance
Photoacoustic Spectroscopy
Beam Splitter
Raman Scattering
Rayleigh Scattering
Raman Spectroscopy
Atomic Spectroscopy
Atomic Emission Spectroscopy
Atomic Absorption Spectroscopy
The Inductively Coupled Plasma Torch
The Helium Plasma Torch
Emission Spectrometer
Atomic Absorption Spectrometry
Flame Atomic Absorption Spectrometer
Flame AA
Hollow Cathode Lamp
Electrothermal Atomization
Graphite Furnace
L’vov Platform
Electron Paramagnetic Resonance
Zeeman Effect
Continuous Wave
Electron Paramagnetic Resonance
Pulsed EPR
Electron Spin Echo
Multple Resonance Spectroscopy
Magnetic Resonance Spectroscopy
NMR
Precessing
Nucleus Spin Decoupling in NMR
Superconducting Magnets
NMR Microcells
Electron Impact Ionisation
Chemical Ionization
Inductively Coupled Plasma Ionization
Secondary Ion Mass Spectrometry
Fast Atom Bombardment
Plasma Desorption Mass Spectrometry
Laser Desorption Mass Spectrometry
Matrix Assisted Desorption mass Spectrometry
Field Desorption Ionization
Thermospray Ionization
Electrospray Ionization
Atmospheric Pressure Ionization
Particle Beam Interface
Permeable Membrane Interface
Sector Mass Spectrometer
Quadrupole Mass Spectrometer
Ion Trap Mass Spectrometer
Time of Flight Mass Spectrometer
Optical RotationCircular Dichroism
Circularly Polarized Light
Verdet Constant
Faraday Effect
 

Experimental Fluorescence Spectroscopy

The sample cells used for fluorometric measurements must be constructed of materials that are transparent to the wavelength of light being measured. Even very pure materials may still have traces of fluorescent contaminants and new or replacement cells should always be examined for background Fluorescence. Cells and other glassware employed in fluorescent measurements should be well cleaned and preferably boiled in 50% nitric acid solution followed by careful rinsing with distilled water. Any solvents employed must be checked for background Fluorescence; if inherent Fluorescence is found present in a solvent it can often be removed by distillation. If water is to be used as the solvent it should be deionized distilled water. Plastic containers should be assiduously avoided as trace florescent materials can be leached from the plastic by any solvents stored in them. High quality solvents should always be used and blank fluorescent measurements taken before use. Although commonly used for cleaning glass apparatus, commercial detergents should be avoided, as some are strongly fluorescent; if detergents are used, then their fluorescent properties should be evaluated prior to use. Fluorescent contaminants can arise from stopcock grease, filter paper and from micro organisms developing over time in buffer solutions. Dilute solutions are basically unstable and should be prepared immediately prior to use from strong standard solutions that may be stored with some confidence over extended periods of time. The surface of glass and other types of containers can absorb substances onto their surface and if the concentration of those substances is very small, adsorption can remove a significant amount of the analyte from solution and impair the accuracy of any measurement. For example glass surfaces have strongly polar interactive sites and if an aromatic hydrocarbon dissolved at very low concentrations in a dispersive solvent (e.g. n-heptane, or petroleum ether ) is stored in a glass bottle, the glass surface will become saturated with adsorbed aromatic hyrdrocarbon. Thus, its concentration in the dispersive solvent will be significantly reduced and any analysis of the solution will give low results. Under certain circumstances the intensity of the excitation light can cause analyte decomposition. This effect can be reduced employing an appropriate shutter between the light source and the sample cell and this shutter is only opened for a short time during measurement. Better alternatives are to identify a wavelength for the excitation light that does not cause sample decomposition or reduce the excitation light intensity by using a narrower slit. Finally, the presence of oxidising agents (e.g. dissolved oxygen or the presence of peroxides ) may initiate a reaction with the Fluorescence substance and consequently reduce the Fluorescence. Care must be taken to ensure such oxidising agents are absent from the sample.

A typical example of a Fluorescence spectrometer is that manufactured by SHIMADZU for routine research and routine analytical purposes and is shown in figure 11. The compact, high sensitivity model of this range can handle extremely small samples and easily detect and determine trace concentrations of pollutants. Capillary cells having volumes of 5 μl or less are also available.

Figure 11. The Shimadzu RF-1501 Fluorescence Spectrometer

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About the Author
RAYMOND PETER WILLIAM SCOTT was born on June 20 1924 in Erith, Kent, UK. He studied at the University of London, obtaining his B.Sc. degree in 1946 and his D.Sc. degree in 1960. After spending more than a decade at Benzole Producers, Ltd. Where he became head of the Physical Chemistry Laboratory, he moved to Unilever Research Laboratories as Manager of their Physical Chemistry department. In 1969 he became Director of Physical Chemistry at Hoffmann-La Roche, Nutley, NJ, U.S.A. and subsequently accepted the position of Director of the Applied Research Department at the Perkin-Elmer Corporation, Norwalk, CT, U.S.A.
In 1986 he became an independent consultant and was appointed Visiting Professor at Georgetown
University, Washington, DC, U.S.A. and at Berkbeck College of the University of London; in 1986 he retired but continues to write technical books dealing with various aspects of physical chemistry and physical chemical techniques. Dr. Scott has authored or co-authored over 200 peer reviewed scientific papers and authored, co-authored or edited over thirty books on various aspects of physical and analytical chemistry. Dr. Scott was a founding member of the British chromatography Society and received the American Chemical society Award in chromatography (1977), the M. S. Tswett chromatography Medal (1978), the Tswett chromatography Medal U.S.S.R., (1979), the A. J. P. Martin chromatography Award (1982) and the Royal Society of Chemistry Award in Analysis and Instrumentation (1988).
Dr. Scott’s activities in gas chromatography started at the inception of the technique, inventing the Heat of Combustion Detector (the precursor of the Flame Ionization Detector), pioneered work on high sensitivity detectors, high efficiency columns and presented fundamental treatments of the relationship between the theory and practice of the technique. He established the viability of the moving bed continuous preparative gas chromatography, examined both theoretically and experimentally those factors that controlled dispersion in packed beds and helped establish the gas chromatograph as a process monitoring instrument. Dr. Scott took and active part in the renaissance of liquid chromatography, was involved in the development of high performance liquid chromatography and invented the wire transport detector. He invented the liquid chromatography mass spectrometry transport interface, introduced micro-bore liquid chromatography columns and used them to provide columns of 750,000 theoretical plates and liquid chromatography separations in less than a second. Dr. Scott has always been a “hands-on” scientist with a remarkable record of accomplishments in chromatography ranging from hardware design to the development of fundamental theory. He has never shied away from questioning “conventional wisdom” and his original approach to problems has often produced significant breakthroughs.

gamma rays