Page 13 - FAR 222 Laboratory Manual V2 2019

FAR 222/3 Dosage Form II Semester 1/ 2019-2020

Option 2: Sorensen’s phosphate vehicle via White Vincent
Calculation 1: The best
30 mL V Weight NaCl
Pilocarpine HCl 1 % 0.3 g 0.3×111.1×0.24 = 8 8/(111.1x1)= 0.072
(0.5% pH 3.8-5.2) mL g
Benzalkonium 0.01 % 15 mL (0.02% -
chloride stock)
Sorensen’s 100 mL 100 mL 30 mL
isotonic vehicle
Sodium acid NaH2PO4 40 mL 0.416 g 0.125 g
phosphate 2 H2O
1.04
%w/v or
0.0667 M
or mol/L
(MW
156)
Sodium phosphate Na2HPO4 60 mL 1.434 g 0.43 g
12 H2O
2.39
%w/v or
0.0667 M
(MW
358.1)
Sodium chloride NaCl 0.46 g 0.46 g Amt needed = 0.46
– 0.072 =0.388 g
Distilled water qs ad 30 mL
100 mL

30 mL
Pilocarpine HCl (0.5% pH 3.8-5.2) 1 % 0.3 g
Benzalkonium chloride 0.01 % 15 mL (0.02% stock)
Sodium acid phosphate NaH2PO4 2 H2O 0.125 g
1.04 %w/v or
0.0667 M or mol/L
(MW 156)
Sodium phosphate Na2HPO4 12 H2O 0.43 g
2.39 %w/v or
0.0667 M (MW
358.1)
Sodium chloride NaCl 0.388 g
Distilled water qs ad 100 mL 30 mL

OR

Calculation 2: The limitation to this approach is that the final formulation pH may be different than the
desired pH. The final pH will depend on the two pHs and buffer capacities of the Sorensen's buffer and the
aqueous drug solution.

30 mL V
Pilocarpine HCl 1 % 0.3 g 0.3×111.1×0.24 = 8
(0.5% pH 3.8-5.2) mL
Benzalkonium 0.01 % 15 mL (0.02% -
chloride stock)
SPV needed = 30 – 8 = 22 mL
Sorensen’s 100 mL 100 mL 22 mL needed
isotonic vehicle
Sodium acid NaH2PO4 40 mL 0.416 g 0.092 g
phosphate 2 H2O

8