OTHER TYPES SPECTROPHOTOMETRY Flashcards
OTHER TYPES SPECTROPHOTOMETRY
● Double beam spectrophotometry
● Flame emission spectrophotometry
● Atomic absorption spectrophotometry
● Light is directed forward in two directions by a rotating chopper.
DOUBLE BEAM SPECTROPHOTOMETRY
One light path is directed forward the_____ cuvette, while, simultaneously the other is directed towards the_____ cuvette
DOUBLE BEAM SPECTROPHOTOMETRY
sample
reference
● The intensity of the two light beams is then measured by one or two photodetectors.
● The sample beam is then compared to that of the reference beam
Double beam spectrophotometer
TWO FUNDAMENTAL INSTRUMENT DESIGNS of Double Beam Spectrophotometer
Double Beam in Space
Double Beam in Time
uses two photo detectors (one for the sample and one for the reference beam)
sample and reference are measured simultaneously and the signal from the reference is subtracted from the transmittance of light of the sample
Double Beam in Space
one photo detector and alternately passes the monochromatic radiation through the sample cuvette to the reference cuvette using a chopper
each beam consisting of a pulse of radiation breaks up separated in time by a dark interval
Double Beam in Time
■ device consist of circular disk
■ is a rotating sector of mirror that breaks up or rotates radiation beams
Chopper
Chopper
⅓ of the disk is_____;
⅓ is________ and the remaining
⅓ is______
opaque
transparent
mirrored
Splits the monochromatic beam of light into 2 beams of equal intensities
Chopper
measures Group 1 Metals that contains plus 1 in charge
FLAME EMISSION SPECTROPHOTOMETRY
Principle: “Involves measurement of electromagnetic radiation emitted by the excited atoms in the flame”
measures light emitted by excited atoms
FLAME EMISSION SPECTROPHOTOMETRY
The measurement of emitted light when electrons in an atom become excited by heat energy produced by the flame and returns to ground state.
Flame emission spectrophotometry
are no longer routinely used in clinical chemistry due to the development of iron selective electrodes ( Sodium, Potassium and Lithium)
Flame Photometers
Components of flame emission spectrophotometry
Atomizer
Flame
¡ breaks up the solution into finer droplets so that the atom will absorb heat energy from the flame and get excited
Atomizer
convert the analyte of the liquid sample into vapour state (breaks the chemical bonds to produce atoms)
source of energy that will be absorbed by the atoms to enter the excitation state
Flame