Analyze absorbance

Measure the wavelengths of light that a solution absorbs and transmits.

Note

For a more detailed experiment procedure, see the Analyzing the absorption spectrum of leaves sample experiment. Classroom-ready experiments are also available in the PASCO Experiment Library.

Procedure

Part 1: Prepare the samples for analysis

1. Fill the cuvettes ¾ full with the sample solutions, then cap the cuvettes.

2. Prepare a reference solution by filling one cuvette ¾ full with the solvent used to make the sample solutions.

   Note

   Handle the cuvettes only by the lined sides to avoid getting fingerprints on the smooth sides, which could interfere with results.

Part 2: Connect and calibrate the spectrometer

1. Start Chemvue, then connect your spectrometer to the program. The software should automatically open to the solution spectra page of the Spectrometry Module.
2. Cover the spectrometer's sample chamber to block ambient light, then select the Calibrate Dark button.
3. Insert the reference solution cuvette into the spectrometer's sample chamber, then select Calibrate Reference .

Part 3: Collect data

1. Insert a sample into the spectrometer's sample chamber and select Start .
2. In the Tools panel, adjust the Smoothing and Number of Scans to Average sliders as needed.
3. When you are satisfied with the results, select Stop to end data recording.

Part 4: Analyze the data

1. Select Coordinates to add a coordinates data target to the graph.
2. Use the data target to locate the peak(s) for each sample.
3. Use the other graph tools as needed to perform further analysis.

Classroom-ready experiments

Plant Pigments

Students analyze spinach pigments and chloroplasts using paper chromatography, a colorimeter, and a spectrometer to understand how plants capture light for photosynthesis.

Chemical Equilibrium

Students use the results of a spectrometer and a temperature sensor to control the direction of a reversible chemical reaction.