A brief introduction to the titration technique used to know the concentration of unknown solutions. different types, indicators used and its application in foods and nutrition is also described.

1. >>PRINCIPLES & APPLICATIONS OF
INSTRUMENTS & TECHNIQUES<<
By: Saloni Shroff
Semester 1 – Roll no. 04
FN (Nutrigenomics)

2. INTRODUCTION . . .
 Titration is a technique to determine the
concentration of an unknown solution.
 Titration is the slow addition of one solution of a
known concentration (called a titrant or titrator) to a
known volume of another solution of unknown
concentration (called a titrand or analyte) until the
reaction reaches neutralization, which is often
indicated by a color change.
 Also known as Titrimetry or Volumetric Titration.

3. Elements of Titration . . .
 The standard solution: the
solution of known
concentration.
An accurately measured
amount of standard solution is
added during titration to the
solution of unknown
concentration until the
equivalence or endpoint is
reached.
 The analyte: the solution of
unknown concentration is
known as the analyte.
During titration the titrant is
added to the analyte in order to
achieve the equivalence point
and determine the
concentration of the analyte.

4.  The equivalence point: the point when the reactants are
done reacting.
The equivalence point is the ideal point for the
completion of titration. At the equivalence point the
correct amount of standard solution must be added to
fully react with the unknown concentration.
 The end point: it indicates once the equivalence point
has been reached. It is indicated by some form of
indicator which varies depending on what type of titration
being done. For example, if a color indicator is used, the
solution will change color when the titration is at its end
point.

6. Equivalence point & End point are not
necessarily equal.
 An endpoint is indicated by some form of indicator at
the end of a titration.
 An equivalence point is when the moles of a
standard solution (titrant) equal the moles of a
solution of unknown concentration (analyte).

7.  The calibrated burette: it is the main
piece of equipment required for a titration
method. Calibration is important because
it is essential for the burette to be as
accurate as possible in order to dispense
very precise amounts of liquid into the
sample.
A burette is a long cylindrical piece of
glass with an open top for pouring in the
titrant. At the bottom there is a carefully
formed tip for dispensing.
Burettes usually have a plastic stopper
that can easily be turned to deliver mere
fractions of a drop of titrant, if needed.
Burettes come in many sizes and are
marked in millilitres and fractions of
millilitres.

8.  The Indicator: the use of an indicator is key in performing a
successful titration reaction. The purpose of the indicator is to show
when enough standard solution has been added to fully react with
the unknown concentration.
Indicators must only be added to the solution of unknown
concentration when no visible reaction will occur. Depending on the
solution being titrated, the choice of indicator can become key for the
success of the titration.

9. Titration with an Indicator . . .

11. MATERIALS . . .
~Erlenmeyer flask or Beaker
~Excess amount of standard solution (titrant)
~A precisely measured amount of analyte; this will be
used to make the solution of unknown concentration
~Indicator
~Calibrated Burette
~Burette Stand

13. PROCEDURE . . .
Obtain all necessary materials and clean all
necessary items with distilled water
Measure out a precise amount of analyte &
make up the solution of unknown
concentration
Quantitatively transfer the analyte into a
beaker or Erlenmeyer flask
Add additional distilled water until the
analyte is fully dissolved. Measure and
record volume of aqueous solution
Add four to five drops of the appropriate
color indicator into the beaker

14. Swirl the beaker in order to mix the aqueous
solution of the analyte and the drops of
indicator
Fill the burette with an excess amount of
titrant, the standard solution of known
concentration and should be in aqueous form
Clamp the burette carefully to a burette stand.
The tip of the burette should not be touching
any surfaces
Place the beaker containing the aqueous
solution of unknown concentration under the
burette
Record the initial volume of the burette. Make
sure to measure at the bottom of the
meniscus

15. Turn on the stopcock (tap) of the burette so that
standard solution is added to the beaker. This
should cause a color change so be sure to swirl the
beaker until the color disappears
Repeat the above step until the color does not
disappear. This means you have reached the
endpoint
Stop when you've reached endpoint, which is the
point when the reactant within the solution of
unknown concentration has been completely
neutralized
Measure and record your final volume of the burette.
Calculate the volume of standard solution used by
subtracting the initial volume measurement from the
final volume measurement of the burette
Now perform the necessary calculations in order to
obtain the concentration of the unknown solution

16. TYPES Of Titrations . . .
 There are many types of titrations with different
procedures and goals.
Acid – Base titration
Redox titration
Gas phase titration
Complexometric titration
Back titration
Karl Fischer titration
(Potentiometric)

17. Acid – Base titration:
 Acid-base titrations depend on the neutralization
between an acid and a base when mixed in solution.
 In addition to the sample, an appropriate indicator is
added to the titration chamber, reflecting the pH
range of the equivalence point.
 The acid-base indicator indicates the endpoint of the
titration by changing color.

18. The final solution after titration should be neutralized and
contain equal moles of hydroxide and hydrogen ions. So
the moles of acid should equal the moles of base:

19. Some common Indicators used in acid –
base titration:

20. Redox titration:
 Redox titrations are based on a reduction-oxidation
reaction between an oxidizing agent and a reducing
agent.
 A potentiometer or a redox indicator is usually used to
determine the endpoint of the titration.
 Some redox titrations do not require an indicator, due to
the intense color of the constituents.
 For instance, in permanganometry a slight persisting pink
color signals the endpoint of the titration because of the
color of the excess oxidizing agent potassium
permanganate

21. Gas phase titration:
 Gas phase titrations are titrations done in the gas
phase, specifically as methods for determining
reactive species by reaction with an excess of some
other gas, acting as the titrant.
 In one common gas phase titration, gaseous ozone
is titrated with nitrogen oxide according to the
reaction.
 After the reaction is complete, the remaining titrant
and product are quantified (e.g., by ) - this is
used to determine the amount of analyte in the
original sample.

22. Complexometric titration:
 Complexometric titrations
rely on the formation of a
complex between the
analyte and the titrant.
 In general, they require
specialized indicators that
form weak complexes with
the analyte.
 Common examples are
Eriochrome Black T for the
titration of calcium and
magnesium ions, and the
chelating agent EDTA used
to titrate metal ions in
solution.

23. Back titration:
 Back titration is a titration done in reverse- instead of
titrating the original sample, a known excess of
standard reagent is added to the solution, and the
excess is titrated.
 A back titration is useful if the endpoint of the reverse
titration is easier to identify than the endpoint of the
normal titration, as with precipitation reactions.
 Back titrations are also useful if the reaction between
the analyte and the titrant is very slow, or when the
analyte is in a non-soluble solid.

24. Karl Fischer titration:
 A potentiometric method
to analyze trace amounts
of water in a substance.
 A sample is dissolved in
methanol, and titrated with
Karl Fischer reagent. The
reagent contains iodine,
which reacts
proportionally with water.
 Thus, the water content
can be determined by
monitoring the potential of
excess iodine.

25. Titration CURVES . . .
 The graphs of titration curves effectively show the
relationship between the pH of the solution of
unknown concentration as the standard solution is
added to it in order to reach neutralization.

29.  In biodiesel: Waste vegetable oil (WVO) must be
neutralized before a batch may be processed. A
portion of WVO is titrated with a base to determine
acidity, so the rest of the batch may be properly
neutralized. This removes free fatty acids from the
WVO that would normally react to make soap
instead of biodiesel.
 Kjeldahl method: A measure of nitrogen content in a
sample. Organic nitrogen is digested into ammonia
with sulfuric acid and potassium sulfate. Finally,
ammonia is back titrated with boric acid and then
sodium carbonate.

30.  Winkler test for dissolved oxygen: Used to determine
oxygen concentration in water. Oxygen in water
samples is reduced using manganese(II) sulfate,
which reacts with potassium iodide to produce
iodine. The iodine is released in proportion to the
oxygen in the sample, thus the oxygen concentration
is determined with a redox titration of iodine with
thiosulfate using a starch indicator.
 Vitamin C: Also known as ascorbic acid, vitamin C is
a powerful reducing agent. Its concentration can
easily be identified when titrated with the blue dye
Dichlorophenolindophenol (DCPIP) which turns
colorless when reduced by the vitamin.

31.  Ester value (or ester index): A calculated index. Ester
value = Saponification value – Acid value.
 Acid value: The mass in milligrams of potassium
hydroxide (KOH) required to neutralize carboxylic
acid in one gram of sample. An example is the
determination of free fatty acid content. These
titrations are achieved at low temperatures.
 Saponification value: The mass in milligrams of KOH
required to saponify carboxylic acid in one gram of
sample. Saponification is used to determine average
chain length of fatty acids in fat. These titrations are
achieved at high temperatures.

32.  Benedict's reagent: Excess glucose in urine may
indicate diabetes in the patient. Benedict's method is
the conventional method to quantify glucose in urine
using a prepared reagent. In this titration, glucose
reduces cupric ions to cuprous ions which react with
potassium thiocyanate to produce a white
precipitate, indicating the endpoint.

33. . . REFERENCES
http://www.metrohmusa.com/Products/Titration/Food-Titration.html
http://ca.mt.com/ca/en/home/applications/Application_Browse_Laboratory_Analytics/Application_f
am_browse_main.tabs.applications.html
http://www.ehow.com/list_5772040_titration-used-industry_.html
http://www.pprc.org/research/rapidresDocs/RR_Salt_Content.pdf
http://www.labmanager.com/white-papers-and-application-notes/2011/05/metrohm-usa-inc-analysis-
of-sodium-in-foodstuffs-by-thermometric-titration?fw1pk=2#.VBv51pTOJ7w
http://www.aquaculture.ugent.be/Education/coursematerial/online%20courses/ATA/analysis/mine_
ana.htm
http://www.machinerylubrication.com/Read/984/analyzing-water-oil
http://www.ehow.com/about_5406434_purpose-titration.html
http://web.vscht.cz/~kohoutkj/ENG/LAPP_Detn_mineral_elements_v5.pdf
http://www.ehow.com/list_5772040_titration-used-industry_.html