Mix 77.0 mL of 0.2 M sodium hydroxide, 250.0
mL of a solution containing 6.8 g of potassium
dihydrogen phosphate R, and 500 mL of water R. Add 10.0 g of pancreas powder R, mix and adjust the pH if necessary.
Dilute to 1000.0 mL with water R.
Simulated gastric
fluid
Dissolve 2.0 g of sodium
chloride R and 3.2 g of pepsin powder R in water R, add 80 mL of 1 M hydrochloric acid and dilute to 1000.0 mL with water R. If
required, pepsin powder may be omitted.
Increasing pH
For a test involving
increasing pH, one of the following sequences may be used:
To achieve this pH
variation, it is possible either:
— to substitute one
buffer solution for another (whole substitution);
— to remove only half
of the medium each time (half change method) and replace it with a buffer solution of higher pH: the
initial pH is 1.2 and the second solution is
phosphate buffer solution pH 7.5; or,
— to an initial
solution at pH 1.5, to add a dose of a powder mixture containing tris
(hydroxymethyl)aminomethane R and anhydrous sodium acetate R to obtain pH
4.5 and a second dose to obtain pH 7.2,
as described below:
— hydrochloric acid pH 1.5: dissolve 2 g of sodium chloride R in water
R, add 31.6 mL of 1 M hydrochloric acid and dilute to 1000.0 mL with water R;
— buffer solution pH 4.5: mix 2.28 g of tris(hydroxymethyl)aminomethane
R with 1.77 g of anhydrous sodium acetate R; dissolve this mixture in the
hydrochloric acid pH 1.5 described above;
— buffer solution pH 7.2: mix 2.28 g of tris(hydroxymethyl)aminomethane
R with 1.77 g of anhydrous sodium acetate R; dissolve this mixture in the
buffer solution pH 4.5 described above.
The
flow-through cell may be used for the continuous change of pH.
