PTCB Certified Pharmacy Technician (PTCE)MedicationsMedium
A pharmacy technician is preparing a non-sterile compound that requires 0.5 mL of a highly potent liquid ingredient. Which of the following measuring devices would provide the most accurate measurement for this volume?
- AA 100 mL beaker
- BA 10 mL graduated cylinder
- CA 1 mL tuberculin syringe
- DA 5 mL oral syringe
Show answer & explanationAnswer & explanation
Correct answer: C. A 1 mL tuberculin syringe
For measuring small, precise liquid volumes, a syringe offers the highest accuracy due to its narrow bore and fine graduations. A 1 mL tuberculin syringe is specifically designed for very small volumes (typically graduated in 0.01 mL increments), making it the most accurate choice for measuring 0.5 mL.
Why the other options are wrong
- A. A 100 mL beaker is designed for holding and mixing liquids, not for accurate measurement of any volume, especially not 0.5 mL.
- B. A 10 mL graduated cylinder is suitable for volumes of 1 mL or more, but its accuracy for 0.5 mL would be limited due to wider graduations.
- D. A 5 mL oral syringe is better than a graduated cylinder for small volumes, but a 1 mL tuberculin syringe provides even greater precision for 0.5 mL.
Measuring Small Liquid Volumes
The practice of selecting the most appropriate and accurate device for measuring small quantities of liquid ingredients in compounding, typically using syringes for precision.
- Syringes (especially tuberculin) offer highest accuracy for <1 mL.
- Graduated cylinders are for larger volumes, less accurate for small.
- Beakers and flasks are for mixing/holding, not accurate measurement.
Memory trick: Measure liquids right, small or large, choose the best tool's might.