PHARMACEUTICS PRACTICAL 3 – METHODS + DILUTIONS
1. Stock Solution
Weigh 100 mg paracetamol standard.
Dissolve in distilled water.
Make up to 100 mL in a volumetric flask.
Stock concentration = 1 mg/mL
2. Calibration Curve Dilutions
Prepare the following solutions:
Solution | Volume of Stock | Final Volume | Final Concentration |
|---|---|---|---|
1 | 1 mL | 100 mL | 0.01 mg/mL |
2 | 2 mL | 100 mL | 0.02 mg/mL |
3 | 3 mL | 100 mL | 0.03 mg/mL |
4 | 4 mL | 100 mL | 0.04 mg/mL |
5 | 5 mL | 100 mL | 0.05 mg/mL |
6 | 6 mL | 100 mL | 0.06 mg/mL |
7 | 7 mL | 100 mL | 0.07 mg/mL |
Measure absorbance at 243 nm.
Measure each sample in triplicate.
Plot:
Absorbance vs Concentration
3. Dissolution Method
Add 500 mL distilled water to each dissolution vessel.
Allow medium to equilibrate at 37°C.
Withdraw blank sample (T0).
Place 1 suppository into each basket.
Start dissolution apparatus (USP Apparatus 1) at 50 rpm.
Withdraw 10 mL samples at:
0, 10, 20, 30, 45, 60, 80, 100, 120, 150, 180 min.
Filter samples using 0.45 µm filter.
Measure absorbance at 243 nm using UV spectrophotometer.