Analytical intro + Spectro Flashcards
- radiant energy; photons of energy traveling in a wavelike manner
- exists as ____ waves
- streams of particles called _____ - distance between two peaks as the light travels in wavelike manner
- expressed in ___,____,____
- 1nm = ___
- 1nm = ____ - visible spectra
- non visible spectra:
- UV region
- infrared region - relies on acuity to determine end point
- ELECTROMAGNETIC ENERGY
- Maxwells waves
- PHOTONS - WAVELENGTH
- nanometers, angstroms, millimicron
- 10A
- 1millimicron - 340nm-700nm
4.
- below 340nm
- above 700nm - Visual Colorimetry
- measurement of light intensity in a much narrower wavelength
- makes use of ___ or ___ as monochromator - measurements of light intensity of multiple wavelength
- makes use of ___ to isolate part of spectrum
- Spectrophotometry
- prisms/ diffraction gratings - Filter photometry
- filters
PRINCIPLE of SPECTROPHOTOMETRY (LAW OF COLORIMETRY)
1. light passes thru ____ to provide a selection of the desired region of the spectrum to be used for measurements
2. ____ are used to isolate a narrow beam of light and to improve its chromatic purity
3. light next passes thru ______ where portion of radiant energy is absorbed, depending upon the nature and concentration of solution
4. any light not absorbed is transmitted to _____, which converts the light energy to electrical energy that can be registered on a meter or a digital
read-out
- MONOCHROMATOR
- SLITS
- ABSORPTION CELL
- DETECTOR
- BEERS LAW
- conc of the sol’n is ______ proportional to the amount of light absorbed
- conc of the sol’n is ______ proportional to log of transmitted light
- ratio of radiant energy transmitted; divided by radiant energy incipient on sample
- amount of light absorbed - BOUGUERS LAW
- aka
- ABSORBANCE is ______ proportional to length of light path - ABSORBANCE FORMULA:
- proportionality constant or molar absorptivity or extinction coefficient
- molar concentration of absorbing substance
- length of light path in cm
- BEERS LAW
- DIRECTLY
- INVERSELY
- %T
- ABSORBANCE/ Optical Density - BOUGUERS LAW
- LAMBERTS
- DIRECTLY - ABSORBANCE FORMULA:
- a
- c
- b
Components of Spectro:
_____: provides a continuous spectrum of white light which can be separated at different
wavelengths
- produces energy wavelength from 340 – 700 nm (visible region); used
for moderately diluted solution - contains small amounts of halogen such as iodine to prevent the
decomposition of the vaporized tungsten from the very hot filament - provides energy source with high output in the UV range (down to
165 nm) - used above 800nm
- electrically heated rod of rare earth element oxides
- uses silicon carbide - emits narrow bands of energy at well-defined places in the spectrum (UV and visible)
- consists of a gas-tight chamber containing anode, a cylindrical cathode, and inert gas such as helium or argon
LIGHT SOURCE
1. TUNGSTEN IODIDE LAMP
2. QUARTZ HALIDE LAMP
3. DEUTERIUM DISCHARGE LAMP
4. INFRARED ENERGY SOURCE
- MERST GLOWER
- GLOBAR
5. MERCURY VAPOR LAMP
6. HOLLOW CATHODE LAMP
Components of Spectro:
______: isolates a narrow beam of radiant energy; prevents stray light from entering the monochromator
______: wavelength selector; isolates radiant energy of desired wavelength and exc that of other wavelengths
- wedge-shaped pieces of glass, quartz, NaCl, or some other material that allows transmission of light
- disperses white light into a continuous spectrum of colors by
- for visible region
- for uv region - consist of a thin layer of aluminum-copper alloy on the surface of a flat
glass plate that has many small parallel grooves ruled into the metal coating - colored glass or colored gelatin sandwiched between two glass plates
- band pass - dielectric material (e.g. NaF) sandwiched between two half silvered pieces of glass
- band pass
ENTRANCE SLIT
MONOCHROMATOR
- PRISM
- REFRACTION
- GLASS PRISMS
- QUARTZ PRISMS - DIFFRACTION GRATINGS
- TRANSMISSION FILTERS
- 35-50nm - INTERFERENCE FILTERS
- 10-20nm
Components of Spectro:
_____: used to hold the solution whose conc is to be measured
- for solutions that do not etch glass
- does not absorb UV radiation at wavelength below 320 nm
- good for 340 nm and above (visible region)
ANALYTICAL / ABSORPTION CELL / CUVETTE
1. BOROSILICATE GLASS
2. QUARTZ/PLASTIC
3. ALUMINA SILICATE GLASS
Components of Spectro:
_____: measure light intensity by converting light signal into electrical signal
- composed of a film of light sensitive material (e.g. Selenium) on an iron plate with a transparent layer of silver; generate their own electrical output directly from light energy
- aka
- positive electrode
- negative electrode - photosensitive material that gives off electrons when light energy strikes it
- aka - device whose electrical resistance decreases as the level of incident light is raised
- aka
- ____ are light-sensitive materials typically used for the
visible region - capable of significantly amplifying current
- ____ is negative light-sensitive metal that absorbs light and emits electrons in proportion to the radiant energy that strikes the surface
- electrons go to dynodes, where electrons produces ___ additional electrons
- electrons are collected at ____
DETECTORS
- BARRIER-LAYER CELL
- PHOTOCELL/PHOTOVOLTAIC CELL
- IRON BASE
- SELENIUM W/ SILVER - PHOTOEMISSIVE TUBE
- PHOTOTUBE - PHOTOCONDUCTIVE TUBE
- PHOTORESISTIVE TUBE
- CADMIUM SULFIDE/SELENIDE - PHOTOMULTIPLIER TUBE
- CATHODE
- 4-6
- FINAL ELECTRODE (Positive)
Components of Spectro:
_____: where electrical energy from a detector is displayed
- output of the detector is used to drive a sensitive meter directly
without further amplification - output of the detector is balanced against the output of a reference
circuit - numerical display of absorbance or converted values of concentrations
- ________
READ OUT DEVICES
- DIRECT READING SYSTEM
- NULL POINT SYSTEM
- DIGITAL READ OUT
- MICROPROCESSOR
DOUBLE BEAM SPECTROPHOTOMETERS
- beams of light pass through different components but at the same time
- all components are duplicated except - two beams of light pass through different components but not at the same time
- uses _____ (rotating wheel) with alternate silvered sections and cut out sections, inserted after the exit slit
- Double Beam-In-Space
- Light source - Double Beam-In-Time
- Light beam chopper
