PHAN LAB FINALS 2 Flashcards
It is a method of analysis that deals with the measurement of spectra.
Spectrometry
It is a branch of spectrometry that embraces the measurement of the absorption by chemical species of radiant energy
SPECTROPHOTOMETRY
It is the distance between two consecutive peaks or
crests
Wavelength
What are the ranges of wavelengths
UV 220 – 380 nm
Visible 380 – 780 nm
Near IR 780 – 3000 nm
Medium IR 3.0 – 15 um
Far IR 15 – 300 um
It is the number of waves passing through any point
per second.
Frequency (n)
Principles of wavelengths
Every substance absorbs or transmits certain wavelengths of radiant energy but not other wavelengths.
The intensity of the transmitted radiant energy is a function of the concentration.
Components of a colorimeter
Light Source
Condenser
Monochromator (Prism)
Slit
Sample Holder (Cuvette)
Detector (Photocell)
Display
It is the ratio of the amount of light transmitted to the amount of light that initially fell on the surface.
Transmittance
It is the negative logarithm of transmittance.
Absorbance and transmittance bear an inverse relationship.
Absorbance
This law states that the power of a TRANSMITTED radiant beam DECREASES exponentially as the CONCENTRATION of the solution containing the absorbing chemical species increases
arithmetically.
Beer’s Law
This law states that the power of a TRANSMITTED radiant beam DECREASES exponentially as the THICKNESS of the solution containing the absorbing chemical species increases arithmetically.
Lambert’s / Bouguer’s Law
This law is a combination of the the two laws and relates the power of the incident and the transmitted radiant beam to the thickness and concentration of the solution
Beer-Bouguer’s Law
Beer-Lambert
Wave length of UV Region
100nm - 400 nm
Wavelength of Visible Region
400nm - 750nm
The light source for UV - VIS
tungsten filament lamps and hydrogen-deuterium
lamps are the most widely used and suitable light sources as they cover the whole UV region.
UV instrumentation that is composed of prisms and slits
Monochromator
Instrumentation made of either silica or quartz. Glass can’t be used for the cells as it absorbs light in the
UV region.
Sample and reference cells
Instrument that is generally, two photocells serve the purpose of the detector in UV spectroscopy.
Detector
Instrument that amplify the signals many times to get a clear and recordable signal.
Amplifier
Instrument that stores all the data generated and
produces the spectrum of the desired compound.
Recording Device
Light source for UV Spectrometry
- Hydrogen-deuterium lamp
- Mercury lamp
Light Sources for VIS spectrometry
Tungsten Lamp
Applications of UV-VIS
- Detection of impurities
- Quantitative determination of compounds that absorb UV radiation
- Study of kinetics of reactions
- Drug and raw materials assay
