Learn how to construct calibration curve of Paracetamol by using UV-spectroscopic method with theory and procedure.
Calibration curve of Paracetamol by UV
To construct calibration curve of Paracetamol using UV spectroscopic method.
Requirements
- Chemicals: Standard Paracetamol powder, distilled water
- Apparatus: UV spectrophotometer, test tubes, pipette, measuring cylinder, volumetric flask, electronic balance, filter paper
Theory
In analytical chemistry, calibration curve help to determine the concentration of a substance in an unknown sample by comparing unknown to a set of standard samples of known concentrations. In spectrophotometric analysis a series of standard solutions of known concentrations are prepared and the absorbance is measured using spectrophotometer instrument to determine the unknown concentration of sample by beer’s law.
Procedure
Preparation of Stock solution:
- Weigh 5 mg paracetamol powder by using electronic balance.
- Take this powder in a 50 ml volumetric flask and fill with distilled water up to the mark.
- Shake the flask until the paracetamol powder was dissolved. This solution is stock solution
Preparation of working standard :
- Take 0 to 9 test tubes.
- Mark serially from 1-9
- Keep in a test tube holder.
- Take the marked 1 test tube and add with 10 ml of distilled water. No stock solution is require in this test tube.
- Now, take test tube no. 2 and add 0.5 ml of stock solution and 9.5 ml of distilled water.
- Conduct the dilution process for the rest of the test tubes.
Absorbance Determination:
- Turn on UV spectrophotometer and wait for the complete calibration
- Fill 2/3rd of the cell with distilled water; set the wavelength at 249 nm and press the auto zero button.
- Record absorbance of all the dilutions of the stock solutions.
- Plot the concentration in X-axis and absorbance in Y-axis and form a standard curve using excel in computer.
- From the standard curve find the straight-line equation and regression (R2) value.
| Test tube No. | Stock solution (ml) | Distilled water (ml) | Concentration (μg/ml) | Absorbance |
|---|---|---|---|---|
| 1 | 0 | 10 | 0 | 0 |
| 2 | 0.5 | 9.5 | 5 | 0.314 |
| 3 | 1 | 9 | 10 | 0.526 |
| 4 | 1.5 | 8.5 | 15 | 0.759 |
| 5 | 2 | 8 | 20 | 0.824 |
| 6 | 2.5 | 7.5 | 25 | 0.98 |
| 7 | 3 | 7 | 30 | 1.5 |
| 8 | 3.5 | 6.5 | 35 | 1.6 |
| 9 | 4 | 6 | 40 | 1.9 |
Result
Calibration curve of paracetamol equation is 0.968.
You may also like to read Simultaneous estimation of ibuprofen and paracetamol by UV spectroscopy.