Spektrophotometrische Bestimmung von Aspirin

Messung des Aspiringehalts in Handelstabletten durch UV-Absorption

Colorimetry Advanced (University) 75 Min. ~$10,00

Ziel

Die Menge an Acetylsalicylsäure (Aspirin) in Handelstabletten durch UV-Spektrophotometrie nach Hydrolyse zu Salicylat bestimmen.

Hintergrund

Aspirin (acetylsalicylic acid) can be quantified by first hydrolyzing it to salicylic acid, which forms an intensely purple complex with iron(III) chloride. This complex absorbs strongly at 530 nm. By comparing the absorbance of hydrolyzed tablet solutions with a calibration curve of standard salicylic acid solutions, students determine whether commercial tablets contain the labeled amount of aspirin.

Sicherheitswarnungen

  • NaOH and HCl are corrosive
  • Do not ingest any laboratory samples
  • FeCl₃ stains skin and clothing
  • Handle hot solutions with care

Erforderliche PSA

goggles gloves lab_coat

Materialien

  • Aspirin tablets (commercial) (3 tablets)
    325 mg or 500 mg labeled
  • Salicylic acid standard (1 g)
    For calibration
  • Iron(III) chloride (FeCl₃) solution (1%) (100 mL)
    Color reagent
  • NaOH (1M) (50 mL)
    For hydrolysis
  • HCl (1M) (50 mL)
    For acidification
  • Distilled water (500 mL)

Ausrüstung

Spectrophotometer Cuvettes Volumetric flasks (100 mL, 8 total) Hot plate or water bath Mortar and pestle Analytical balance Filter paper and funnel

Durchführung

1

Prepare salicylic acid standards: 0, 5, 10, 20, 30, 40 ppm in 100 mL volumetric flasks.

10 Min.
2

Crush one aspirin tablet and dissolve in 10 mL of 1M NaOH. Heat gently on a water bath for 15 minutes to hydrolyze the ester bond.

20 Min. Handle hot solution carefully
3

Cool the solution, acidify with 10 mL of 1M HCl, and filter into a 100 mL volumetric flask. Dilute to an expected concentration within the calibration range.

10 Min.
4

Add 5 mL of 1% FeCl₃ solution to each standard and sample flask. A purple color develops.

5 Min.
5

Allow 5 minutes for full color development. Measure absorbance at 530 nm, blanking with the 0 ppm standard.

15 Min.
6

Plot the calibration curve. Determine the salicylic acid concentration in the tablet solution, then calculate back to the original aspirin mass (accounting for hydrolysis stoichiometry and dilution).

15 Min.

Erwartete Ergebnisse

The calibration curve should be linear. The calculated aspirin content should be close to the labeled amount (typically 95–105% of the stated dose). The purple FeCl₃ complex confirms salicylate presence.

Aufräumen

Neutralize acid/base waste before disposal. Collect FeCl₃ waste separately. Rinse all glassware thoroughly.

Details

Kategorie
Colorimetry
Schwierigkeit
Advanced (University)
Dauer
75 Min.
Geschätzte Kosten
$10,00
Schritte
6
Materialien
6

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Frequently Asked Questions

What is the objective of Spektrophotometrische Bestimmung von Aspirin?
Die Menge an Acetylsalicylsäure (Aspirin) in Handelstabletten durch UV-Spektrophotometrie nach Hydrolyse zu Salicylat bestimmen.
How difficult is Spektrophotometrische Bestimmung von Aspirin?
This experiment is rated as Advanced (University). It takes approximately 75 minutes to complete.
What safety precautions are needed for Spektrophotometrische Bestimmung von Aspirin?
Key safety precautions include: NaOH and HCl are corrosive; Do not ingest any laboratory samples; FeCl₃ stains skin and clothing.
What materials are needed for Spektrophotometrische Bestimmung von Aspirin?
The main materials required are: Aspirin tablets (commercial), Salicylic acid standard, Iron(III) chloride (FeCl₃) solution (1%), NaOH (1M), HCl (1M).
What results should I expect from Spektrophotometrische Bestimmung von Aspirin?
The calibration curve should be linear. The calculated aspirin content should be close to the labeled amount (typically 95–105% of the stated dose). The purple FeCl₃ complex confirms salicylate presence.