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M-11
Following the procedure outlined below, calibrate the spectrophotometer and read the
absorbance of the [Fe(Bipy)3]
2+
complex at each different wavelength for the absorption
spectra.
i.
To begin, set the instrument to a wavelength of 350 nm using the vertical arrows to
increase (
)or decrease (
) the wavelength. To change the setting quickly, hold the
button down firmly.
ii.
Insert the cuvette containing the “BLANK” solution into the cuvette holder with the
“ARROW” on the cuvette oriented to the LEFT.
iii.
Press “CAL” so the instrument will compensate for any Absorbance due to the
background solution.
The value of “A” for the blank at any given wavelength equals 0.000 once the
calibration has occurred.
iv.
Remove the BLANK and insert the cuvette containing the standard
solution #2,
again with the arrow facing LEFT. The absorbance of the solution is displayed on
the screen. Record the absorbance of this solution at this wavelength on your
Observations Sheet.
v.
Adjust the wavelength to 400 nm and repeat steps i. to iv. to determine the
absorbance at this wavelength. Continue to determine the absorbance of standard
solution #2 at 50 nm intervals to 700 nm.
5.
Identify the region of the spectra where the
max
is likely to occur and determine the
exact wavelength of
max
by measuring the absorbance of the standard
solution #2
at
5 nm intervals for 25 nm above and below this apparent maximum.
6.
From this information, decide on the wavelength of
max
for the [Fe(Bipy)3]
2+
(aq)
complex
that will be used for the calibration curve in Part III. Check the absorbances at the
wavelengths surrounding
max
to be sure it is identified correctly.
Part III:
Calibration Curve
1.
Set the spectrophotometer wavelength control to the wavelength of
max
for
the
[Fe(Bipy)3]
2+
complex.
2.
Using the correct procedure, fill clean cuvettes with the remaining standard solutions.
Wipe the cuvettes dry, then in sequence, align each in the sample holder and measure and
record the absorbance of each standard solution.
