PRELIM LEC: ANALYTICAL TECHNIQUES AND INSTRUMENTATION (TRANSES) Flashcards
TRANSES AND NOTES
-are described as photons of
energy traveling in waves
Electromagnetic Radiation
is the highest point while trough is the lowest point
Crest or peak
is the distance of two peaks/crest or troughs
when light travels in a wavelike manner
Wavelength
Units:
Angstrom (A)Millimicrons (mu) Nanometer (nm)
Conversion factors:
1 nm = 10 A; 1 nm = 1 mu; 1 A = 10 mu
is the number of waves that pass an observation point in a unit of time
Frequency
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
The shorter the wavelength,
the larger number of photons will
be contained in a given distance
More photons represents more energy, hence,
shorter wavelengths represent higher energy
Wavelength or frequency of the electromagnetic waves are
perceived as
color or hue
shorter wavelength = high frequency color
bluish colors
long wavelength = low frequency colors
reddish color
Height or amplitude of the electromagnetic waves are
perceived as
intensity or brightness
great amplitude=
bright colors
small amplitude =
dull colors
two kinds of wavelengths:
Visible Spectra
Invisible Spectra
can be observed at 340-700nm
Visible Spectra
wavelength of less
than 400nm
Invisible Spectra
ultraviolet
wavelength of greater than
700 nm
Invisible Spectra
Infrared
Other types of electromagnetic energy includes:
Cosmic Rays, Gamma Rays, X-rays and Appliances (Radio, TV, Microwave, Etc.)
Red (650-700)
Complementary Color
Green
Orange (600-650)
Complementary Color
Blue
Yellow (550-600)
Complementary Color
Indigo
Green (500-550)
Complementary Color
Red
Blue (450-500)
Complementary Color
Orange
Indigo (400-450)
Complementary Color
Yellow
Violet (350-400)
Complementary Color
Yellow
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
ratio of the radiant energy transmitted, divided by the radiant energy incident on the sample
%T
amount of light
absorbed
Absorbance (OD-optical density)
provides electromagnetic radiation as visible, infrared, or UV light
Light source
TYPE OF LIGHT SOURCE:
1.Tungsten/Tungsten-iodide lamp
2.Mercury Vapor Lamp
3.Deuterium Discharge Lamp
4.Infrared Energy Source
5.Quart Halide Lamp
6.Hollow Cathode Lamp
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
- ]can emit UV ligh
- exists narrow bands of energy at well defined places in the spectrum UV and visible light
Mercury Vapor Lamp
energy wavelength UV
range (down to 165nm)
Deuterium Discharge Lamp
above 800 nm
Infrared Energy Source
contains small amt of halogen such as iodine to prevent the decomposition of vaporized tungsten
Quart Halide Lamp
consists of a gas-tight chamber containing anode, a cylindrical cathode and insert gas such as helium
Hollow Cathode Lamp
reduces stray light and prevents scattered
light from entering the monochromator
Entrance Slit
solates the specific wavelength of choice
Monochromator
TYPES OF MONOCHROMATOR:
- Prism
- Gratings
- Colored Filters
- Interference Filters
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
Prism
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
Gratings
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
Colored Filters
band pass is 35-50nm or more
Colored Filters
enhances desired wavelength by constructive
interference and eliminates others by destructive interferences
Interference Filters
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
Interference Filters
band pass is 10-20nm
Interference Filters
where the light from the monochromator will pass through
exit slit
used to hold the solution in the instrument
whose concentration is to be measured
Analytical Cell
TYPES OF ANALYTICAL CELLS:
- Borosilicate Glass
- Quartz or Plastic
- Aluminum Silica Glass
- Soft glass
alkaline solution that do not etch
glass
Borosilicate Glass
best for wavelength below 320nm
PLASTIC CELLS - BOTH VISIBLE AND UV RANGE
Quartz or Plastic
best for visible light
Aluminum Silica Glass
best for acidic solution
Soft glass
- converts transmitted light energy into an equivalent amount of electrical energ
Detector
TYPES OF DETECTOR:
- Barrier layer cells
- Photoemission tube
- Photomultiplier tube
composed of film of light sensitive
material; no power source needed
Barrier layer cells
has photosensitive material that gives off electron when light energy strikes it; requires
an outside voltage for operation
Photoemission tube
used a series of electrodes to internally amplify the photosignal before leaving the tube
Photomultiplier tube
simplest method of displaying output of the detection system
Meter (read out device)