A TE buffer contains 200 mMTris and 50 mM EDTA. Given the stock solutions – 0.5 M Tris and 0.5 M EDTA,
volumes of stock solutions required to make 1 liter of buffer solution are respectively:
(1) 400 ml, 100 ml
(2) 200 ml, 50 ml
(3) 500 ml, 125 ml
(4) 100 ml, 25 ml
How to Prepare a TE Buffer from Stock Solutions – A Step-by-Step Guide
TE buffer (Tris-EDTA buffer) is commonly used in molecular biology for storing DNA and RNA because it helps maintain pH and protects nucleic acids from degradation. The buffer typically contains Tris for pH stabilization and EDTA to chelate divalent metal ions (like Mg²⁺), which could otherwise degrade nucleic acids.
Here, we’ll learn how to prepare 1 liter of TE buffer that contains:
-
200 mM Tris
-
50 mM EDTA
Using stock solutions of:
-
0.5 M (500 mM) Tris
-
0.5 M (500 mM) EDTA
🧮 Step-by-Step Calculation
To find the required volume of each stock solution, use the dilution formula:
C1V1=C2V2 C_1V_1 = C_2V_2
Where:
-
C1C_1 = concentration of stock solution
-
V1V_1 = volume of stock solution to use
-
C2C_2 = desired final concentration
-
V2V_2 = final volume of solution
🔹 For Tris:
-
C1=0.5 MC_1 = 0.5 \, \text{M}
-
C2=0.2 MC_2 = 0.2 \, \text{M} (200 mM)
-
V2=1 L=1000 mLV_2 = 1 \, \text{L} = 1000 \, \text{mL}
V1=C2×V2C1=0.2×10000.5=400 mLV_1 = \frac{C_2 \times V_2}{C_1} = \frac{0.2 \times 1000}{0.5} = 400 \, \text{mL}
🔹 For EDTA:
-
C1=0.5 MC_1 = 0.5 \, \text{M}
-
C2=0.05 MC_2 = 0.05 \, \text{M} (50 mM)
-
V2=1000 mLV_2 = 1000 \, \text{mL}
V1=0.05×10000.5=100 mLV_1 = \frac{0.05 \times 1000}{0.5} = 100 \, \text{mL}
✅ Correct Answer: (1) 400 mL Tris, 100 mL EDTA
Now, add distilled or deionized water to bring the total volume to 1 liter.
TE Buffer Preparation Summary
| Component | Stock Concentration | Desired Final Concentration | Volume Needed |
|---|---|---|---|
| Tris | 0.5 M | 200 mM (0.2 M) | 400 mL |
| EDTA | 0.5 M | 50 mM (0.05 M) | 100 mL |
| Water | — | — | 500 mL |
| Total | 1000 mL |
Importance of TE Buffer
-
Tris maintains a stable pH (typically around pH 8.0).
-
EDTA binds divalent cations like Mg²⁺ and Ca²⁺ to prevent nucleases from degrading DNA/RNA.
-
Used in DNA extraction, storage, and enzymatic reactions.
Final Thoughts
Learning how to prepare common lab buffers like TE buffer from stock solutions is an essential skill for students, researchers, and lab technicians. This guide demonstrates how a bit of simple math using the dilution formula can help you precisely prepare the right concentrations.
Accurate buffer preparation = reliable results in experiments.
Whether you’re working in molecular biology, biochemistry, or biotechnology, mastering buffer calculations will boost both your confidence and credibility in the lab.
