Question

The composition of 1X TBE is: 89mM Tris (molar mass = 121.14 g/mol) 89mM Boric Acid (molar mass = 61.83 g/mol) 2mM EDTA (molar mass = 292.24 g/mol) However, TBE is commonly made as a concentration 10x buffer that is then diluted to 1X just prior to use.

1) What are the concentrations each of the components in the 10X TBE storage buffer? Tris:______________ Boric Acid:_________ EDTA:____________

2) Now calculate the amount of each components in grams needed to make 1L of th 10x TBE storage buffer. For full credit, show all of your work.

Answer 1

The composition 1X TBE buffer is: 89mM Tris (Molar mass = 121.14 g/mol) 89mM Boric acid (molar mass = 61.83 g/mol) 2mM EDTA (Molar mass = 292.24 g/mol)

1. The concentration of 1X TBE can be multiplied by 10 to arrive at 10X concentration. So molar concentrations are also multiplied by 10.

So, concentrations of each of the components in the 10X TBE buffer are:

Tris : 890mM = 0.890M

Boric acid : 890mM = 0.890M

EDTA : 20mM = 0.020M

2. To calculate the amount of each of the components in grams, multiply the molar concentrations with the respective molar masses. As these are molar concentrations, the calculated amount in grams will be for 1L of buffer solution.

Thus, Tris: 0.890 mol/L * 121.14 g/mol = 107.8 g 108 g

Boric acid : 0.890 mol/L * 61.83 g/mol = 55 g

EDTA : 0.020 mol/L * 292.24 g/mol = 5.84g 6 g