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Determination of Available Fe in Fresh Water Sample

Students will determine the total concentration of free iron in freshwater and/or municipal drinking water via visible absorption spectrophotometry. This exercise will require students to create standards of Fe(phen) 3 2+ (phen = 1,10-phenanthroline), measure the absorption of these standards at the wavelength of maximum absorbance, and plot a calibration curve. This information will then be used to measure the amount of iron in provided samples via a similar process. The experiment will introduce concepts in absorption spectroscopy, sample preparation, and data analysis – framed within a real-life question relevant to environmental and public health considerations (i.e. “How much iron is in our water?”). Insight into the behavior of complex ions will be discussed with regards to the formation of Fe(phen) 3 2+ and its purpose in the experiment.

Get the Lab Procedure Handout                  Get the Data Analysis Worksheet

 

Teacher Notes  

These notes include instructions for solution preparation as well as examples of data from the videos below.

The Overview:

 


Safety Precautions

  • Make sure to wear safety goggles and gloves whenever you handle chemicals. In addition to wearing gloves, always wash your hands after handling chemicals.
  • Use caution when handling concentrated acid such as sulfuric acid.
  • Two of the reagents used in this lab (1,10-phenanthroline and hydroxylamine hydrochloride) are considered toxic! Handle these solutions with gloves, and wash your hands immediately if you spill them on yourself.

Material List

  • Laptop with Vernier Spectral Analysis installed
  • Vernier Go Direct SpectroVis Plus Spectrophotometer
  • cuvette
  • Kimwipes (or lint-free optic cleaning wipes)
  • Masking tape and markers for labeling
  • Safety goggles and gloves 

Additionally, each group will need the glassware and solutions outlined in the Lab Procedure Handout.


Lab Preparation and Procedure

Procedure - Preparing the Water Sample

Timing: Approximately 1 hour. Ideally, the sample should be prepared in the morning of the day that the lab procedure will be taking place.

 


Procedure - Preparing the Standards

Timing: Approximately 1 hour. 

 


Procedure - Filtering the Water Sample

Timing: Approximately 1 hour. Ideally, the sample should be filtered in the morning of the day that the lab procedure will be taking place. 


Procedure - Final Preparation of the Water Sample

Timing: Approximately 15 minutes.  


Data Collection and Analysis of Fe(II)

Timing: Approximately 30 minutes.

 

This lab was created by the Ren Research group at Purdue University with funding from the National Science Foundation grant NSF CHE 2102049.

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