阿司匹林的分光光度法测定

用紫外吸收测定商业片剂中的阿司匹林含量

Colorimetry Advanced (University) 75 分钟 ~$10.00

目标

水解为水杨酸盐后，用紫外分光光度法测定商业片剂中乙酰水杨酸（阿司匹林）的含量。

背景

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.

安全警告

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

所需PPE

goggles gloves lab_coat

材料

  • 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)

设备

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

步骤

1

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

10 分钟
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 分钟 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 分钟
4

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

5 分钟
5

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

15 分钟
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 分钟

预期结果

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.

清理

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

详情

类别
Colorimetry
难度
Advanced (University)
时长
75 分钟
预估费用
$10.00
步骤数
6
材料
6

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Frequently Asked Questions

What is the objective of 阿司匹林的分光光度法测定?
水解为水杨酸盐后，用紫外分光光度法测定商业片剂中乙酰水杨酸（阿司匹林）的含量。
How difficult is 阿司匹林的分光光度法测定?
This experiment is rated as Advanced (University). It takes approximately 75 minutes to complete.
What safety precautions are needed for 阿司匹林的分光光度法测定?
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 阿司匹林的分光光度法测定?
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 阿司匹林的分光光度法测定?
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.