Question

1X TAE buffer is commonly used as a buffer for DNA gel electrophoresis. You will preform the calculations necessary to prepare a 50X concentrated stock to store and use throughout the semester. The composition of a 50X TAE stock buffer is 2 M Tris, 1 M acetic acid, 50 mM EDTA, pH 8. Determine how much of each component you will need to make 100 ml of a 50X stock buffer. Show your calculations and construct a table which contains all your calculated values. You will use solid Tris base, glacial acetic acid (stock concentration = 17.5 M), and 0.5 M EDTA.

Answer 1

The 50X TAE stock buffer contains:

2.0M of Tris buffer

1.0M of acetic acid

50mM of EDTA

pH=8.0

To start solving its exercise, I am going to calculate the mass of Tris (m_Tris) to take from stock to be added to the TAE buffer. It is needed to calculate the moles of Tris (n_Tris) before calculating its mass.

Then, we need to calculate the acetic acid volume and EDTA volume to be taked from its stocks solutions by applying the mass conservation.

V_T=0.1L=100.0ml

[EDTA]_Stock=0,5M

[EDTA]_Buffer=50,0mM=0,05M

V_T=100,0ml=0,1L

Stock	Take from the stock
Tris	24.228g
Acetic acid	5.714ml
EDTA	10.00ml