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Analysis & Purity of Aspirin Tablets

Analysis & Purity of Aspirin Tablets


There are many different types of spectroscopy. Chemists typically use ultra-violet/visible spectroscopy (UV-Vis) to identify compounds and measure their purity. Pharmaceutical scientists use ultra-violet/visible spectroscopy for drug tests and purity assays while environmental chemists use ultra-violet/visible spectroscopy for environmental testing of water and soil.

In this laboratory experiment, your students will analyze over-the-counter aspirin tablets on the UV-Vis instrument to calculate their purity. They will use the aborbances from a set of standards, generate a calibration curve, and use the linear regression line to calculate the percent of aspirin in a tablet.  This value will then be compared to the USP (United States Pharmacopeia) regulations.  


    This U-PIK will include enough materials for four student groups.  Suggested group size is 4-5 students.  The U-PIK will include the following:


    • 4 UV-Vis units
    • 4 LabQuest 2 interfaces
    • 5 sets of quartz cuvettes
    • 4 boxes of Kimwipes
    • 5 vials of aspirin standard
    • 5 vials of aspirin tablets (2 per vial)
    • 5 sets of volumetric pipets
    • 5 sets of volumetric flasks
    • Methanol (used as a dissolving aid)
    • 5 Ziploc bags of transfer pipets (10 per bag)

    The ultra-violet/visible spectrometer can be easily used to support the concept wavelength and the electromagnetic spectrum.  The known samples will have a maximum wavelength between the ranges of 200-400 nm.  This range will highlight the importance of the ultraviolet region of the electromagnetic spectrum.  


    Students will be required to generate a calibration curve using Excel.  They will use the linear regression line to solve for the concentration of the aspirin sample.  This value will be converted into the percentage of aspirin and compared to the United States Pharmacopeia (USP) regulation.  Therefore a previous discussion of a calibration curve and the dilution equation is recommended.  We encourage you to complete the "Introducton to UV Spectroscopy" prior to this experiment.  


    Time:  Two laboratory periods (one period for sample preparation, one period for analysis on the instrument).  


    Student Level:

    INTERMEDIATE (Grades 9-12) 

  • UV Vis Manual

  • Lab Experiment: Preview Document

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