Introduction:
The BeerLambert Law is used to show the relationship between
absorbance and concentration. The BeerLambert Law can be quantitavely expressed by
the following equation:
A=
ε
bc
The “A” in this equation is used to signify the measured absorbance, the “c” is used to
denote the concentration, the “b” is the path length or the width of the cuvet, and the “
ε
”
is a constant called the molar absorptivity. The molar absorptivity is constant for a
particular chemical compound at a specific wavelength. Usually, there is one wavelength
that corresponds to the maximum epsilon value. The molar absorptivity value can be
derived from a graph that has the concentration values on the xaxis and the absorbance
values on the yaxis. This graph has a linear relationship between these two values and
can be written in the form y=mx+b (where b, the intercept, is zero). The slope of this line
is equivalent to εb.
Typically there are two types of dilutions that are commonly employed. A serial
dilution involves a series of solutions where each of the solutions that are made becomes
the source solution for the following solution in the series. One advantage behind
conducting a serial dilution is that a number of concentrations can be accomodated if this
approach is used. A parallel dilution is where a series of solutions are made from the
original solution. The advantage behind conducting a serial dilution is that there are fewer
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 Spring '08
 Shaheen
 Food coloring, allura red dye, Tartrazine Yellow Dye

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