Xác Định Aspirin Bằng Quang Phổ

Đo hàm lượng aspirin trong viên nén thương mại bằng hấp thụ UV

Colorimetry Advanced (University) 75 phút ~$10,00

Mục tiêu

Xác định lượng axit axetylsalixylic (aspirin) trong viên nén thương mại bằng quang phổ UV sau khi thủy phân thành salixylat.

Bối cảnh

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.

Cảnh báo an toàn

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

PPE cần thiết

goggles gloves lab_coat

Vật liệu

  • 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)

Thiết bị

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

Quy trình

1

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

10 phút
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 phút 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 phút
4

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

5 phút
5

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

15 phút
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 phút

Kết quả dự kiến

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.

Dọn dẹp

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

Chi tiết

Danh mục
Colorimetry
Độ khó
Advanced (University)
Thời gian
75 phút
Chi phí ước tính
$10,00
Số bước
6
Vật liệu
6

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Frequently Asked Questions

What is the objective of Xác Định Aspirin Bằng Quang Phổ?
Xác định lượng axit axetylsalixylic (aspirin) trong viên nén thương mại bằng quang phổ UV sau khi thủy phân thành salixylat.
How difficult is Xác Định Aspirin Bằng Quang Phổ?
This experiment is rated as Advanced (University). It takes approximately 75 minutes to complete.
What safety precautions are needed for Xác Định Aspirin Bằng Quang Phổ?
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 Xác Định Aspirin Bằng Quang Phổ?
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 Xác Định Aspirin Bằng Quang Phổ?
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.