Question

A prescription calls for 50 mg of chlorpheniramine maleate. Using a prescription balance with a sensitivity requirement of 6 mg, explain how you would obtain the required amount of chlorpheniramine maleate with an error not greater than 5%?

Answer 1

To obtain the required amount of chlorpheniramine maleate with an error not greater than 5%, we need to use the prescription balance with a sensitivity requirement of 6 mg. Here's the step-by-step process:

1. Prepare the balance: Ensure that the prescription balance is clean and calibrated. Make sure the sensitivity requirement is set to 6 mg.

2. Tare the balance: Place an empty container (such as a weighing boat) on the balance pan and press the "Tare" or "Zero" button to reset the balance to zero with the empty container on it. This will ensure that only the substance's weight is measured, not the container.

3. Weigh the chlorpheniramine maleate: Carefully add the chlorpheniramine maleate to the weighing boat on the balance pan until it reaches approximately 50 mg. Slowly add the substance in small increments to avoid overshooting the target weight.

4. Fine-tune the measurement: When you approach the approximate target weight (around 45-50 mg), add the substance more carefully, one small increment at a time, until the balance indicates a reading of around 50 mg. Make sure to wait for the balance to stabilize after each addition.

5. Check the accuracy: Once you have the approximate target weight, carefully observe the balance reading. If the reading is not within the acceptable range (50 mg ± 5% = 47.5 mg to 52.5 mg), adjust the amount of chlorpheniramine maleate accordingly.

6. Correct any errors: If the initial measurement goes beyond the acceptable range, you can carefully remove a small quantity of the substance using a spatula or another suitable tool until the weight is within the desired range.

7. Final check: After making any adjustments, recheck the weight on the balance to ensure it falls within the acceptable range (50 mg ± 5%).

8. Record the measurement: Once you have successfully weighed the required amount of chlorpheniramine maleate within the desired tolerance, carefully transfer it to an appropriate container, such as a medicine vial, and label it accurately.

By following these steps and being cautious with your measurements, you can obtain the required 50 mg of chlorpheniramine maleate with an error not greater than 5% using the prescription balance with a sensitivity requirement of 6 mg.