How much of a 200 mg/dL stock creatinine solution is needed to make 100 mL of a 10 mg/dL solution?

Dilution Calculation for Creatinine Solution

To make 100 mL of a 0.1 mg/mL solution from a 200 mg/dL stock creatinine solution, you need 5 mL of the stock solution.

Step-by-Step Calculation Process

1. First, convert the target concentration to the same units as the stock solution:

   • Target: 0.1 mg/mL = 10 mg/dL (since 1 dL = 100 mL)

2. Apply the dilution formula V₁C₁ = V₂C₂:

   • V₁ = volume of stock solution needed
   • C₁ = concentration of stock solution (200 mg/dL)
   • V₂ = final volume desired (100 mL = 1 dL)
   • C₂ = final concentration desired (10 mg/dL)

3. Solve for V₁:

   • V₁ = (V₂ × C₂) ÷ C₁
   • V₁ = (1 dL × 10 mg/dL) ÷ 200 mg/dL
   • V₁ = 10 mg/dL ÷ 200 mg/dL
   • V₁ = 0.05 dL = 5 mL

4. Therefore, you need to add 5 mL of the 200 mg/dL stock solution to enough diluent to make a final volume of 100 mL.

Important Considerations for Laboratory Dilutions

• When preparing laboratory solutions, always use calibrated pipettes and volumetric flasks for accurate measurements.
• For volumes less than 0.1 mL, special attention is needed as these small volumes are prone to measurement errors 1.
• Always document the dilution process and label the final solution with concentration, date of preparation, and expiration date.
• For clinical laboratory work, follow standardized protocols to ensure consistency and reliability in test results.

Verification of Calculation

To verify the calculation:

• 5 mL of 200 mg/dL solution contains 10 mg of creatinine
• When diluted to 100 mL, the concentration becomes 10 mg/100 mL = 0.1 mg/mL

This dilution approach ensures accurate preparation of the desired creatinine solution for laboratory testing or research purposes.