Identification of diazepam Potentiometric Titration( Non-aqueous titration)
Molecular Formula: C16H13CLN2O Molecular Mass: 284.7
Chemical Name: 7-Chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one
General Requirement: Diazepam contains not less than 99.0% and not more than 101.0% of C16H13CLN2O , calculated with reference to the dried substanceAssay
standard(0.1M)HCLO4 solution
Glacial acetic acid
Diazepam TabletApparatus
, Beaker, Magnetic stirrer and stirring bar, pH-meter
procedures
Accurately weight 250 mg or 0.55gm of sample( tablet ) and transfer to a 250 ml beaker
Add 30 ml of glacial acetic acid. and wait a few minutes .The tablet should crumble. To the tablet in the beaker now stir the tablet with a glass rod until it dissolves
Note: the white solid that dissolves slowly is starch and it may not dissolve completely
Place the beaker containing the sample on a magnetic stirrer
Titrate this solution using the procedure of the following
A. Wash the pH electrode off distilled water and dry carefully using a kimiwipe
B.
Carefully immerse the electrodes of previously standardized pH-meter into the Diazepam solutionC. Fill the burette with standard (0.1N) HCLO4
Note: before starting the magnetic stirrer be absolutely certain that the magnetic stirring bar will not strike the electrode
D. Determine the pH of the solution before adding any 0.1N HCLO4 titrant, and record this value
E. Add 3ml of (0.1N) HCLO4 of the beaker from burette. Stir the solution carefully and note the potential after 15 seconds, and record both milliliters of titrant and pH of the solution
F. Continue the procedure for every addition of 3ml of (0.1N) HCLO4 till the potential of the solution shows a tendency to increase rapidly, at this stage, add (0.1N) HCLO4 in increments of 0.3ml and note the PH after each addition, also note the increments which give the greatest difference in pH . This pH contains the equivalence point. When the PH increase is small, stop noting the PH
H. Prepare a graph by plotting pH values against volume of (0.1N)HCLO4. The end point of the titration may be determined graphically by drawing a vertical line from the midpoint of the steepest part of the titration curve to the X axis
The point where this line intersects the X axis is then taken as the volume of titrant consumed at the equivalence point.(…….A...ml)
I.Calculate the % Diazepam Tablet
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