PTCB Certified Pharmacy Technician (PTCE)MedicationsEasy
A pharmacy technician is preparing a non-sterile compound requiring 30 grams of an ingredient. The balance used has a sensitivity requirement of 6 mg and a minimum weighable quantity (MWQ) of 120 mg. To ensure accuracy, which of the following is the most appropriate action?
- ARequest a different balance with a higher sensitivity.
- BWeigh the 30 grams directly on the balance.
- CUse an aliquot method to weigh the ingredient.
- DRound the quantity to the nearest gram for easier measurement.
Show answer & explanationAnswer & explanation
Correct answer: B. Weigh the 30 grams directly on the balance.
The minimum weighable quantity (MWQ) is the smallest amount that can be weighed with acceptable accuracy on a given balance. Since 30 grams (30,000 mg) is significantly greater than the MWQ of 120 mg, the ingredient can be accurately weighed directly.
Why the other options are wrong
- A. A different balance is not necessary as the current balance is suitable for this quantity.
- C. The aliquot method is used when the desired quantity is less than the MWQ, which is not the case here.
- D. Rounding the quantity would introduce an inaccuracy and is not an appropriate method for compounding.
Minimum Weighable Quantity (MWQ)
The smallest amount of a substance that can be weighed with acceptable accuracy (typically within 5% error) on a specific balance.
- Calculated as (Sensitivity Requirement / Acceptable Error) * 100%
- Ensures accurate measurement for compounding.
- If quantity is below MWQ, aliquot method must be used.
Memory trick: Measure carefully, MWQ ensures no tiny slips.