TITRIMETRIC Analysis third year pharmacy

Titrimetric analysis

1. Titrimetric Analysis

2. Basic Terminologies
Analyte(orActiveConstituent)isthechemicalentity
underassay.
Titrantisthesolutionofknownstrength(or
concentration)employedintheassay.
or
Theacidorbaseofknownamountandconcentrationthat
isaddedtotheunknownsolutionduringanacid-base
titration.

3. EndPointisthepointatwhichthereappearsan
abruptchangeincertaincharacteristicoftheprevailing
reactionmixtureorachangethatiseitherascertained
electrometricallyorisvisiblyspottedbytheuseof
indicators.
EquivalencePoint(orStoichiometricPoint)isa
theoreticalpointatwhichequivalentamountofeach
reactanthavereactedduringtitration
Standardizationistheactualdeterminationofeither
thenormalityorthemolarityofasolution.
Basic Terminologies…

4. Titer:istheweightofasubstancechemically
equivalentto1mlofastandardsolution.
Titration:Anexperimentwhereanunknown
concentrationofacidorbaseisneutralizedwitha
knownvolumeandconcentrationofacidorbaseto
determinetheconcentrationoftheunknown.
TitrationCurve:AplotofsolutionpHversus
titrantvolumeduringatitration.
Basic Terminologies…

5. ALGEBRAIC RELATIONSHIP
AT THE EQUIVALENCE POINT
Equivalent A = Equivalent B
Basic Terminologies…

6. Primary Standard is the substance of known purity,
whose carefully weighed quantity helps in the
standardization of an unknown solution (normality or
molarity).
Secondary Standard is another standard solution that
is used for standardization of an unknown solution.
Example : An unknown solution of HCl may be
standardized volumetrically in two ways, namely :
(i) by the help of ‘Anala R’-grade Na2CO3 i.e., purity is
known-‘Primary Standard’, and
(ii) by the help of another standard solution of NaOH
‘Secondary Standard’.
Basic Terminologies…

7. Properties of Primary standard
•High purity
•Atmospheric stability
•Independent of humidity
•Modest cost
•Large molar mass
Basic Terminologies…

8. Indicator : is a chemical substance
sensitive enough to display an apparent
change in color very close to the point in the
ongoing titration process at which equivalent
quantities of analyte and titrant have almost
virtually reacted with each other.
Basic Terminologies…

9. Basic Terminologies…

10. Basic Terminologies…

11. Basic Terminologies…
Acidimetry
It is the measurement of quantity of a base by
titration with a suitable standard acid.
Potassium hydrogen phthalate, oxalic acid and
benzoic acid are examples of standard acids.
Alkalimetry
It is the measurement of quantity of an acid by
titration with a suitable standard base.
Anhydrous sodium carbonate, borax are examples
of standard bases.

12. •Burette
•Volumetric flask
•Beaker
•Pipette
•Funnel
•Indicator

13. EQUIPMENT

14. Burette titration procedures

15. TITRIMETRIC METHODS OF
ANALYSIS

16. It includes a group of analytical methods
that are based upon determining the
quantity of a reagent of unknown strength
that is required to react completely with the
analyte.
Titrimetric Methods

17. Type of Titrimetric Methods/Analysis
Classified into five major divisions
1.Neutralization or Acid-base titrations
2. Non-aqueous titrations
3. Redox (Reduction-Oxidation) titrations
4.Complexometric titrations
5.Precipitation titrations

18. 1. Neutralization or Acid-base titrations
It involves the neutralization of an acid with a base
or vice versa. It has further two types.
➢Acidimetric Titrations
➢Alkalimetric Titrations

19. Acidimetric Titrations
It is a direct or residual volumetric analysis of a
base with a standard acid.
➢Direct Acidimetric Titration
➢Residual Acidimetric Titration
Neutralization or Acid-base titrations…

20. Direct Acidimetric Titration
It is a direct titration of reactant with
standard solution of another reactant.
Example:
Standard acid solution taken in burette
which is titrated with solution of base being
assayed e.g assay of sodium bicarbonate
Acidimetric Titrations…

21. Back-Acidimetric titration/Residual Acidimetric
titration
A process in which the excess of a standard
solution used to react with an analyte is
determined by titration with a second
standard solution.
Example
Ammonia solution is treated with an accurately
measured standard acid and the standard acid is
back titrated with a standard alkali by using methyl
red as indicator
Neutralization or Acid-base titrations…

22. Alkalimetric Titrations
It is a direct or residual volumetric analysis of an
acid with a standard alkali(base).
Or
It is an estimation of acid/acidic drugs by titration
with standard alkali.
➢Direct Alkalimetric Titration
➢Residual Alkalimetric Titration
Neutralization or Acid-base titrations…

23. ASSAY OF DRUGS
•A few typical examples of alkalimetric
titrations, employing ‘Direct titration
method’ (DTM) and
•‘Residual titration method’ (RTM)
from the ‘Pharmacopoeias ’ are described
here :

24. ASSAY TEST OF IBUPROFEN TABLETS

25. INTRODUCTION:
Ibuprofen is a non-steroidal anti-inflammatory
agent, belongs to the aryl alkanoic acid derivatives,
mainly used as analgesic and anti-inflammatory
drug in rheumatoid arthritis and moderate pain.

26. PHYSIOCHEMICAL PROPERTIES
•It is a white crystalline
powder.
• insoluble in water, but freely
soluble in organic solvents
such as acetone, ether,
methanol and chlorinated
hydrocarbons.
•As an acid, it can react with
bases such as sodium
hydroxide to form the water
soluble ibuprofen sodium salt.
•Its molecular weight equals
206.3 g/mole.
•melting point is 75 °C.

27. AVAILABLE DOSAGE FORMS:
Exists as cream, gel, oral suspension and tablets or
capsules.

28. ASSAY TEST:
➢Weigh 20 tablets, and then grind them using a
mortar and a pestle.
➢From the powder, take equivalent amount
containing 0.4 g ibuprofen; dissolve in 20 ml
chloroform for 15 minutes.
➢Filter the solution under reduced pressure, and
wash the residue with three times (5 ml) chloroform.
➢Evaporate the filtrate to dryness under current air
(inside the hood).
➢Dissolve the solid residue in 80 ml absolute
ethanol.
➢ Titrate with 0.1M NaOH using phenolphthalein as
indicator.

29. CALCULATIONSThe chemical equation for the titration step should be:

30. CALCULATIONS
Note: Each 1 ml of 0.1 M NaOH is equivalent to
20.63 mg of Ibuprofen.
 According to BP, Ibuprofen tablets should
contain not less than 95% and not more than
105% of the labelled amount of Ibuprofen.
According to USP, Ibuprofen tablets should
contain not less than 90% and not more than
110% of the labelled amount of Ibuprofen.

31. SOURCE OF ERRORS
❑Intrinsic errors (end point # eq. point)
❑Systematic errors (Temp)
❑Instrumental errors(vol. glassware accuracy)
❑Method errors( non-ideal chemical behavior)
❑Personal errors (misreading the volume)
❑Gross errors (personal carelessness)

32. Residual Titration
In this method, acid is treated with excess of
accurately measured quantity of base. The
unreacted base is then titrated with a
standard acid.
Assay of Aspirin
It contains not less than 99.5% and not more
than the equivalent of 100.5% of aspirin
calculated with reference to the dried
substance.

33. Assay of Aspirin…
Procedure
Weigh accurately aspirin (1.5 g), dissolve in
95% ethanol (15ml) add 0.5M NaOH
solution(50ml) and boil for 10 minutes. Cool
the solution and titrate the excess of alakali
with 0.5M HCl solution using phenol red
indicator.

34. On boiling with NaOH solution, aspirin is
hydrolyzed into salicylic acid and acetic acid.
The liberated acid reacts with NaOH to form
sodium salt.
Assay of Aspirin…

35. The excess of unreacted NaOH is titrated
with 0.5M HCl solution. At the end point, a
slight excess of the acid reacts with the
indicator to produce colour change.
Factor : Each ml of 0.5M NaOH = 0.04504 g
of C9H8O4
Assay of Aspirin…