Study Set Content:
is the path length
b
is the analyte concentration
c
According to the Beer-Lambert Law the absorbance is ____ to the concentration of the substance in solution and as a result UV-visible spectroscopy can also be used to measure the concentration of a sample.
proportional
When working in concentration units of molarity, The Beer-Lambert Law can be expressed in the form of the following equation:
A = εLc
is the amount of light absorbed for a particular wavelength by the sample.
A
is the molar extinction coefficient
ε
is the distance covered by the light through the solution
L
is the concentration of the absorbing species
c
If the absorbance of a series of sample solutions of known concentrations are measured and plotted against their corresponding concentrations, the plot of absorbance versus concentration should be_____ if the Beer-Lambert Law is obeyed.
linear
Limitations of the Beer-Lambert Law
The linearity of the Beer-Lambert law is limited by chemical and instrumental factors. Causes of nonlinearity include:
deviations in absorptivity coefficients at ____ (>0.01M) due to electrostatic interactions between molecules in close proximity.
high concentrations
due to particulates in the sample
scattering of light
fluorescence or ____ of the sample
phosphorescence
changes in ____ at high analyte concentration
refractive index
shifts in chemical equilibria as a function of
concentration.
_____ deviations can be minimized by using a relatively flat part of the absorption spectrum such as the maximum of an absorption band.
stray light
non-monochromatic radiation,
typically employ different light sources for the ultraviolet and visible regions of the spectrum.
UV/VIS spectrometers
