Question

You have the following buffer recipe and decide to make up some concentrated solutions first so that you won't have to weigh out dry ingredients, wait for them to dissolve, and correct the pH every time you make it. How much dry ingredients do you use for each of the following 4 stock solutions? Show you work and include units in your calculations. The Buffer Recipe is: 150 mM NaCl (formula weight 58.44 g) 10 mM Tris pH 8.0 (formula weight 121 g) 2 mM EDTA (formula weight 292 g) 0.2% bovine serum albumin Stock 1 of 4: 3 M NaCl, 100 mL ________ ?

Answer 1

to calculate weight of ingridents we use following folmula -: w = (E*N*V) / 1000

so,         w= (Molecular weight * molarity * volume) / 1000

where w=weight of ingredient, E = equivalent weight (E=Molecular weight/ no. of moles), N= normality (N=No.of moles * M molarity), V= volume of solution

(1) for NaCl, w= (Molecular weight * molarity * volume) / 1000

w = 58.44* 150mM *100ml / 1000ml = 58.44* (150*10^-3)M *100ml / 1000ml = 0.8766 g

(2) for Tris, w =121* 10mM * 100ml /1000ml = 0.121 g

(3) for EDTA, w = 292* 2mM *100ml / 1000ml = 0.0584 g

(4) 0.2% bivine serum albumin stock means 2g/l BSA. to make it for 100ml solution we use following calculations-

in 1L (1000ml) bovine serum albumin = 2g

so in 100ml bovine serum albumin = 2g *100ml /1000ml = 0.2 g

so we will add 0.2g bovine serum albumin in our solution at the end then again correct/maintain the desirable pH.