Beer-Lambert Law

CHEM 14BL

for volumetric glassware

report to the hundredth decimal place in mL (two decimal places)

advantages of beer-lambert law

rapid, easy to establish quality control measures for reliability, and lends itself to on-line monitoring

disadvantages of beer-lambert law

have to set up chemistry so that the absorption of light by the chemical species of interest will have a very different absorption profile than the other constituents in the solution

implication of beer’s law

if epsilon is constant, “A” should be directly proportional to “C”

epsilon in beer’s law is only constant if

wavelength is fixed during analysis and sample has a low concentration (absorbance)

absorbance for beer’s law falls within the range:

0.1 to 1.0

beer’s law graph at constant wavelength

starts at 0, slope is linear and is equal to epsilon x L

experimental response in beer’s law

how to solve the problem: beer’s law doesn’t work if the solution concentration is too high

dilute the sample to make sure absorbance falls between 0.1 and 1

how to solve the problem: need to take care of background interference

use a blank solution to take care of this, should contain all the chemical species except the one you want to measure

in beer’s law, how can you tell if an incorrect blank solution was used?

the y intercept on the graph is not zero