PRELIM 1: ANALYTICAL TECHNIQUES AND INSTRUMENTATION Flashcards
is the highest point
Crest or peak
is the lowest
point
trough
is the number of waves that pass an observation
point in a unit of time
Frequency
is the distance of two peaks/crest or troughs
when light travels in a wavelike manner
Wavelength
is the distance between two adjacent peak and
trough
Amplitude
is inversely proportional to the frequency of
the light wave
Wavelength
is inversely proportional to the wavelength of light
Energy
Wavelength or frequency of the electromagnetic waves are perceived as
color or hue
Height or amplitude of the electromagnetic waves are
perceived as
intensity or brightness
There are two kinds of wavelengths: ______which
can be observed at 340-700nm and the_____
which could either be Ultraviolet with a wavelength of less
than 400nm or Infrared with a wavelength of greater than
700 nm.
Visible Spectra, Invisible Spectra
Principle: Measures the amount of light transmitted to determine the concentration of the light-absorbing substance in the solution; the measurement of the light transmitted by a
solution to determine the concentration of the light-absorbing
substance in the solution
Spectrophotometry
states that the concentration of
substance is directly proportional to the amount of light absorbed but inversely proportional to the logarithm of transmitted light
Beer-Lamberts Law
= amount of light
absorbed
Absorbance (OD-optical density)
-provides electromagnetic radiation as visible,
infrared, or UV light
Light source
type of light source can emit UV light
Mercury Vapor Lamp
type of light source ideal for emission
of light within the visible region (iodide prolongs stability of Tungsten); produces energy wavelength from 340-700nm (visible region); used for moderately
diluted solution
Tungsten/Tungsten-iodide lamp
type of light source energy wavelength UV
range (down to 165nm)
Deuterium Discharge Lamp
Types of light source
-Tungsten/Tungsten-iodide lamp
-Mercury Vapor Lamp
-Deuterium Discharge Lamp
-Infrared Energy Source
-Quart Halide Lamp
-Mercury vapor Lamp
-hallow cathode lamp
type of light source above 800 nm
Infrared Energy Source
- reduces stray light and prevents scattered light from entering the monochromator
Entrance Slit
type of light source contains small amt of halogen such as iodine to prevent the decomposition of vaporized tungsten
Quart Halide Lamp
type of light source exists narrow bands of energy at well defined places in the spectrum UV and visible light
Mercury Vapor Lamp
Spectophotometer components
-light source
-entrance slit
-monochromator
-exit slit
-analytical cell
-detector
-meter
type of light source consists of a gas-tight
chamber containing anode, a cylindrical cathode and
insert gas such as helium
Hollow Cathode Lamp
- isolates the specific wavelength of choice
Monochromator
types of monochromator
-prism
-gratings
-colored filters
-interference filters
commonly used type of monochromator
diffraction gratings
-wedge-shaped pieces of glass, quartz, or sodium chloride that allows transmission of light wherein each side of the prism has different thickness allowing selection of wavelength of light
-disperses white light into a continuous spectrum of colors based on variation of refractive index for different wavelength
Prism
-has small grooves cut at such an angle that each grooves behave like a very small prism and the wavelengths are bent as they pass a sharp corner
-separate white light into various color comp.
Gratings
-made of glass that absorbs some portion of the electromagentic spectrum and transmit others wherein
light energy is absorbed by dye components on the class and is dissipated as heat
-band pass is 35-50nm or more
Colored Filters
- used to hold the solution in the instrument
whose concentration is to be measured
Analytical Cell
-enhances desired wavelength by constructive
interference and eliminates others by destructive
interferences
-utlizes the wave cx of light to enhance the intensity of
the desired wavelength by constructive interference and
eliminates others by destructive interference and reflections
-band pass is 10-20nm
Interference Filters
type of analaytical cell for alkaline solution that do not etch
glass
Borosilicate Glass
type of analaytical cell best for wavelength below 320nm
Quartz or Plastic
type of analaytical cell best for visible light
Aluminum Silica Glass
type of analaytical cell best for acidic solution
Soft glass
- converts transmitted light energy into an equivalent
amount of electrical energy
Detector
type of detector composed of film of light sensitive
material; no power source needed
Barrier layer cells
type of detector has photosensitive material that gives off electron when light energy strikes it; requires
an outside voltage for operation
Photoemission tube
type of detector used a series of electrodes to
internally amplify the photosignal before leaving the tube
Photomultiplier tube
Principle: measures the light emitted when electrons in an
atom become excited by heat energy produced by the flame
Flame Emission Spectrophotometry
simplest method of displaying output
of the detection system
Meter (read out device)
Measures electrolytes with a 1+ charge: Na, K, Li
Flame Emission Spectrophotometry
Excited atoms return to ground state by emitting light energy
that is characteristic of that atom
Flame Emission Spectrophotometry