meas. of radiant energy absorbed/given off by a molecule after illumination of a light source
PHOTOMETRY
should always be present
Light source
Class. of Clin Chem Instrumentation that measures EMR:
-Photometry
-Electrochemistry
Photometry
Spectrophotometry
Emission Flame Photometry/ Filter Photometry
Atomic Absorption Spectrophotometry
Fluorometry
Turbidity & Nephelometry
radiant energy frm short rays (gamma rays) to WL long rays (UV & microwave)
EMR (electromagnetic radiation)
- portions of energy traveling in a wavelength manner
- shorter wavelength, higher EM energy
Types of EMR:
cosmic rays, gamma rays, x-rays, UV rays, infrared, microwaves (radio, tv, radar)
Theory of Light Waves
- photon (E) or discrete packet of energy traveling in waves
- have a peak/crest & trough
distance bet 2 successive peaks/crests
- gives light its char. color
Wavelength
Nanometer (nm)
– 10-9m; SI unit
Millimicron (mu)
1nm
Angstrom (Å)
10-10m, 1nm=10Å
Kinds of wavelength
- visible spectra – 340-700nm
- invisible spectra – UV & IR
distance bet peak & trough
Amplitude
assoc. w/ spectro
Colorimetry
Colorimetry – assoc. w/ spectro
Primary considerations in analysis:
- Quality
- Intensity
not seen; complimentary to the color seen
Color absorbed
all colors are transmitted
White light
Kinds of colorimetry:
- visual
- Photoelectric: Spectro & Filter photometry
- uses eye in determining end pt
- very crude & subjective; less sophisticated & flexible
- intensity of color must be proportionate to conc. of the color-producing subs
- simplest colorimetric analysis using a simple device (comparison of unknown w/ standard)
- ex: Dubosq colorimeter, Sahli’s hemoglobinometer
VISUAL
- refined type of colorimeter
Dubosq Colorimeter:
Dubosq Colorimeter:
- refined type of colorimeter parts:
- light source
- 2 glass-bottomed cups
- 2 movable platforms
2 glass plungers - optical system
- 2 identical scales
- reading: 20 at platform scales for both cups - left cup: standard sol.
