5
Change the Settings in Logger
Pro
3
Spectrometer Dialog Box
The Spectrometer dialog box lists all the settings for the device. To display this box
choose Set Up Sensors
►
Spectrometer from the Experiment menu.
For most experiments, the default settings work well.
There are four parameters listed in the dialog box.
Sample Time: this is similar to the shutter speed of a camera. Logger
Pro
3
automatically selects the proper sample time during calibration.
Note:
For
emission studies, you may need to change the sample time manually.
Wavelength Smoothing: the number of adjacent readings on either side of a given
value that is used to calculate an average value.
Note
: Be careful adjusting this
parameter as it may shift your wavelength values slightly.
Samples to Average: the number of readings taken at a given wavelength to
calculate an average reading.
Wavelength Range: the range is determined by the type of spectrometer in use.
By clicking on the picture of the spectrometer in this dialog box, you will gain
access to four options: calibrate, configure data collection, go to the support web
page, and units of measure. Click on an item to select it.
Use the Vernier Spectrometer with LabQuest
Getting Started
1. Ensure the proper LabQuest App software is installed on your LabQuest before
using the Vernier Spectrometer. Version 2.0 or newer, is required for LabQuest 2
and version 1.1, or newer, is required for the original LabQuest.
2. Use the USB cable to connect the Spectrometer to LabQuest.
3. Turn on LabQuest. The LabQuest App will launch automatically and the Meter
screen will be displayed.
Select the Type of Data (or Units) You Want to Measure
The default data type is absorbance. If you want to measure the absorbance of a
solution, proceed directly to the Calibrate section.
If you want to measure %T or intensity, do the following:
1. From the Sensors menu, choose Change Units
►
USB: Spectrometer.
2. Select the unit or data type you wish to measure.
Calibrate the Spectrometer (Not Required if Measuring Intensity)
1. Choose Calibrate
►
USB: Spectrometer from the Sensors menu.
Note
: For best
results, allow the Spectrometer to warm up for a minimum of five minutes.
2. Fill a cuvette about ¾ full with distilled water (or the solvent being used in the
experiment) to serve as the blank. After the Spectrometer has warmed up, place
the blank cuvette in the Spectrometer. Align the cuvette so a clear side of the
cuvette is facing the light source.
3. Follow the instructions in the dialog box to complete the calibration, and then
click
.
Measurement
vs
. Wavelength (Generate a Spectrum)
1. Fill a cuvette about ¾ full of the solution to be tested and place it in the
Spectrometer.
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2. Start data collection by tapping on the green Start button in the lower left corner
of the screen. Tap the red Stop button to end data collection.
3. Select wavelength.
Note:
The wavelength of maximum absorbance (
λ
max) is
automatically selected. This
λ
max will be used for any subsequent data
collection, such as a Beer’s law experiment (abs
vs.
conc.) or a kinetics
experiment (abs
vs
. time). If you wish to choose another wavelength, you can tap
on the graph to select a new wavelength. Another way to change the wavelength
is to navigate to the Meter screen, tap on the meter itself, and select Change
Wavelength. Enter the wavelength of your choice and select OK. If the
wavelength you type in is not measured by the unit, the LabQuest will
automatically choose the wavelength closest to your choice.
4. To store the spectrum data, tap on the file cabinet icon in the upper right of your
screen.
Measurement
vs
. Concentration (Beer’s law Studies)
1. Generate a spectrum as described above. On the Meter screen, tap Mode. Change
the mode to Events with Entry.
2. Enter the Name (e.g., Concentration) and Units (e.g., mol/L). Select OK.
3. A message will appear warning you to either save or discard the full spectrum run.
Make your choice and proceed with data collection.
4. Place your first Beer’s law standard solution in the Spectrometer. Start data
collection. After the absorbance reading stabilizes, tap Keep. Enter the
concentration of the solution and select OK.
5. Place your second standard sample in the Spectrometer. After the absorbance
readings stabilize, tap Keep. Enter the concentration of the second sample and
select OK.
6. Repeat Step 5 for the remaining standard samples. After you have tested the final
standard, tap the red Stop button to end data collection.
7. To calculate a best fit line equation for your standards, choose Curve Fit from the
Analyze menu. Select Linear for the Fit Equation, and then select OK. The graph
screen will appear again with the linear regression equation displayed.
8. Place a cuvette containing an unknown sample of solution in the Spectrometer.
Tap the Meter tab and write down the displayed absorbance value. Tap the Graph
tab and choose Interpolate from the Analyze menu. Trace the linear regression
equation to determine the concentration of the unknown.
Measurement
vs
. Time (Kinetics)
1. Generate a spectrum as described above. On the Meter screen, tap Mode. Change
the data-collection mode to Time Based.
2. You can change the rate, interval, and/or duration of time of data collection, if
desired. Select OK when you are ready to proceed.
3. A message will appear warning you to either save or discard the full spectrum run.
Make your choice and proceed with data collection.
4. Mix the reactants, transfer ~2 mL of the reaction mixture to a cuvette and place
the cuvette in the Spectrometer. Start data collection. You may tap the red Stop
button to end data collection early.
5. To calculate a function for your data, choose Curve Fit from the Analyze menu.
Select the Fit Equation, and then select OK. The graph screen will appear again.
