Non-aqueous titrations allow for the titration of weakly acidic or basic substances using non-aqueous solvents. This provides sharper endpoints compared to aqueous titrations. Common non-aqueous solvents include acetic acid, acetonitrile, alcohols, and dimethylformamide. Indicators are also used that change color at the titration endpoint. Examples given are the titration of ephedrine hydrochloride and sodium benzoate using perchloric acid in acetic acid with crystal violet indicator.

1. NON AQUEOUS
TITRATION
PROF. MISS YASMIN MOMIN
ASSISTANT PROFESSOR
Annasaheb Dange College of
B.Pharmacy Ashta

2.  Non- aqueous titrations are the titrations in which
weakly acidic or basic substances are carried out
using non–aqueous solvents to get sharp end point.
• The moisture content in non–aqueous titrations
should not be more than 0.05%.
• Moisture and carbon dioxide are to be avoided in
non– aqueous methods.

3. Water behaves as both a weak acid and a weak base thus,
in an aqueous environment, it can compete effectively with
very weak acids and bases with regard to proton donation
and acceptance, as shown below:
H2O + H+ ⇌ H3O+
Competes with : RNH2 + H+ ⇌ RNH3+
H2O + B ⇌ OH− + BH+
Competes with : ROH + B ⇌ RO− + BH+
This which makes the endpoint detection relatively more
difficult. That’s why very weak acid/base can’t be titrated
in water

4. The difficulties encountered in the titration of a dilute solution of a
weak acid with alkali solution are:
• The inflection on the pH-neutralization curve is small.
• The phenolphthalein colour fades away at the end point
(gives rise to confusion).
• Interference due to CO2.
The above difficulties can be overcome if by some means the
dissociation constant of the weak acid can be increased so that it
behaves like a strong acid.
This can be done by using a suitable non-aqueous solvent in
place of water.

5. Levelling Effect : The acidity of the weak acids can be
enhanced using basic solvents because the basic solvent has
higher affinity to take up protons from acid. So, acetic acid
behaves as a strong acid in ammonia solution. Also the
Basicity of the weak bases can be enhanced in the presence of
acidic solvent. This is called the levelling effect of the
solvent.

6. Classification of Non aqueous solvents
They are following types:-
1. Aprotic Solvent
2. Protogenic Solvent
3. Protophillic Solvent
4. Amphiprotic Solvent

7. Aprotic solvent are most important solvent in this
titration.
• This solvent are chemically inert.
• Neither acidic nor basic (inert solvent).
• They have low dielectric constant and do not react with
either acid or base and therefore do not favor ionization.
The most important examples of Aprotic solvent are
• Chloroform
• Benzene
• Dioxan
• Ethyl acetate

8. Protogenic solvent
 Are acidic in nature and they can
 Donate the proton.
 Used to dissolved basic analyte.
 They have high dielectric constant and ionized
 Examples of Protogenic solvent are:
 Glacial acetic acid, formic acid, Propionic acid

9. Protophillic solvent
 Are basic in nature.
 Which possess a high affinity for proton.
 Used to dissolved acidic analytes.
 Examples:- Amines and ketone. Pyridine, Ethylene
diamine, DMF

10. Amphiprotic solvent
• Are those solvent they work as a both mean Protogenic
or Protophillic.
• It means Amphiprotic solvent are acidic and basic in
nature.
• And they are accept the proton and donate the proton.
For examples:-
Alcohols and weak organic acids, amino acids, HCO3−,
H2PO4
–

11. Major solvents used in non aqueous titration
(1) Glacial acetic acid
(2) Acetonitrile (CH3CN)
(3) Alcohols
(4) Dioxane
(5) DMF

12. NON AQUEOUS INDICATORS
The ionized form and unionized form or different resonant
form of indicators generally apply equally for non-aqueous
titration, but the colour change at the end point vary from
titration to titration, as they depend on the nature of the
titrant.
The end point may be determined either by potentiometric
titration or by Titrimetric analysis.

14. B. INDICATOR METHOD: Detection of End point
• The important indicator used for non-aqueous titration are
follow:-
1. Crystal violet:-
• It is considered as the most common indicators in the titration
of the bases.
• It is used as 0.5% solution in glacial acetic acid, it gives violet
colour in basic medium and yellowish green in acidic medium.
It is most widely use for the titration of pyridine with Perchloric
acid.

15. 2. Oracet Blue B Indicator:- It is prepared o.5% glacial acetic acid.
It gives blue colour in basic medium while pink colour in acidic
medium.
3. Quinaldine Red: it is employed as indicator in the determination
of the drug substance in dimethyl formamide (DMF). It is used as
0.1% w/v solution in ethanol. The colour change is from purple red
to pale green.
4. Thymol Blue: it is used as 0.2% w/v solution in methanol. The
colour change is from yellow to blue. Used as an indicator for the
titration of substances acting as acids in DMF.

17. Selection of Solvent for NAT
Acetic acid: used for titration of weak bases, Nitrogen
containing compounds
Acetonitrile / with ACOH: Metal ethanoates
Alcohols (IPA, n -Butanol) : Soaps and salts of organic
acids.
DMF: Benzoic acid, amides etc

18. Titrant for NAT
• Perchloric acid in acetic acid
Amines, amine salts, amino acids, salts of acids
• Potassium Methoxide in Toluene-Methanol
• Quan ammonium hydroxide in Acetonitrilepyridine
Acids, enols, imides & sulphonamides

19. Acidimetry in Non-Aqueous Titrations
Selection of solvent system for weak base and strong acid titration is
important parameter for sharp end point.
Titration of Weak Bases by Non Aqueous Titration
Following points should be considered: -
1. Titrant used.
2. Preparation of 0.1N (HClO4) and it standardization.
3. Solvent used.
4. Practical examples of weak bases along with indicators.
5. Typical example of assay of weakly basic substance e.g.
ephedrine HCl.
6. Titrant used: Solution of HClO4 in either glacial acetic acid or
Dioxane solution is used for titration of weak bases. Generally HClO4 with
a normality of 0.1N to 0.05N is used.

20. Alkalimetry in Non-Aqueous Titrations
By using suitable non-aqueous solvent system weakly acidic substances
can be titrated with a sharp end-point. Examples of organic compounds
include anhydride, acids, amino acids, acid halides, enols
sulphonamides, phenols, imides. However, a weak inorganic acid e.g.,
boric acid, can be estimated conveniently employing ethylene diamine
as the non-aqueous solvent.

21. Alkalimetric Assays: Non-Aqueous Titrations using Lithium
Methoxide/Sodium Methoxide either Potentiometrically or Titrimetrically.
Preparation of 0.1 N Sodium Methoxide in toluene-methanol :
Cool 150 ml of anhydrous methanol in ice water and add in small portions,
about 2.5 gm of freshly cut sodium. When the metal has dissolved, add
sufficient toluene, previously dried over sodium wire to produce 1000 ml.
Standardization of 0.1 N Methoxide Solution
Transfer 10 ml of DMF in a conical flask and add to it 3 to 4 drops
of Thymol blue. Quickly introduce 0.06g of benzoic acid and titrate
immediately with methoxide in toluene-methanol.

22. Estimation of Sodium Benzoate by NAT :-
Sodium Benzoate :
Formula : C7H5NaO2
Mol. Wt. 144.1
Sodium Benzoate contains not less than 99.0 per cent and not more than 100.5
per cent of C7H5NaO2, calculated on the dried basis.
Preparation of 0.1N solution of HClO4 and its standardization: Dissolve 8.5 ml
of 72% HClO4 in about 900 ml glacial acetic acid with constant stirring, add
about 30 ml acetic anhydride and make up the volume (1000 ml) with glacial
acetic acid and keep the mixture for 24 hour. Acetic anhydride absorbed all the
water from HClO4 and glacial acetic acid renders the solution virtually
anhydrous. HClO4 must be well diluted with glacial acetic acid before adding
acetic anhydride because reaction between HClO4 and acetic anhydride is
explosive.

23. Standardization of HClO4 :To 500 mg of potassium hydrogen
phthalate add 25 ml of glacial acetic acid add few drops of 5% w/v
crystal violet in glacial acetic acid as indicator. This solution is
titrated with 0.1 HClO4. The colour changes from blue to blue
green.
Assay Procedure : Weigh accurately about 0.25 g of Sodium
Benzoate, dissolve in 20 ml of anhydrous glacial acetic acid, warming
to 50O C if necessary, cool. Titrate with 0.1 M Perchloric acid, using
0.05 ml of 1-naphtholbenzein solution as indicator. Carry out a blank
titration.
Equivalent or I.P factor : 1 ml of 0.1 M Perchloric acid is equivalent
to 0.01441 g of C7H5NaO2.

24. Estimation of Ephedrine Hydrochloride by NAT :-
Ephedrine Hydrochloride :
Formula : C10H15NO,HCl
Mol. Wt. 201.7
Ephedrine Hydrochloride contains not less than 99.0 per cent and
not more than 101.0 per cent of C10H15NO,HCl calculated on the
dried basis.
Assay Procedure : Weigh accurately about 0.17 g of Ephedrine
Hydrochloride, dissolve in
10 ml of mercuric acetate solution, warming gently, add 50 ml of
acetone and mix. Titrate with 0.1 M Perchloric acid, using 1 ml of
a saturated solution of methyl orange in acetone as indicator, until
a red colour is obtained. Carry out a blank titration.
Equivalent or I.P factor : 1 ml of 0.1 M Perchloric acid is
equivalent to 0.02017 g of C10H15NO,HCl.