Introduction,instruments used,applications,advantages & disadvantages of polarimetry.

1. Presented by
Rakesh B.Ahuja
Guide
Prof. K. B.Gabhane
VidyaBharati College Of Pharmacy, Amravati-444601
2019-2020
POLARIMETRY

2. INDEX
 A. Introduction
 B. Plane Polarised Light
 C. Optical Activity
 D. Theory of Optical Activity
 E. Polarimeter
 F. Applications

3. INTRODUCTION
 Polarimetry is one of the important instrumental
methods employed in analysis. This measures the
rotation of the polarized light as it passes through
an optically active compound. This technique
involves the measurement of change in the
direction of vibration of polarized light when interact
with an optically active compound. A substance is
said to be optically active if it rotates the plane of
the polarized light.

4. PLANE POLARISED LIGHT
 According to wave theory of light, an ordinary ray
light is considered to be vibrating in all planes at
right angle to the direction of propagation. If this
ordinary ray of light is passed through a Nicol
prism, the emergent ray has its vibration only in one
plane. This light having wave motion in only one
plane is known as Plane Polarised Light.
 • NICOL Prism – Iceland Spar
Calcite ( CaCO3 form ) (or) Polaroid

7.  A plane polarized light which consists of two
components of fixed magnitude rotating in opposite
directions to one another.
• The right circulatory polarized light
• The left circulatory polarized light
• Plane polarized light is the vector sum of these two
components

8. OPTICAL ACTIVITY
 Definition:-“The property of rotating the plane of
polarization of plane-polarized light.”
• It Has found that magnitude of rotation depend upon
the following factors:
1.Nature of Substance
2.Length of liquid column ( l ) through which light
passes.
3.Concentration of the solution.
4.Nature of the solvent.
5.Temperature of the solution (t)
6.Wavelength of the light used.

9.  The Rotatory Power of a given solution is generally
expressed as specific rotation. It is the number of
degress of rotation of plane polarized light
produced by one gram of the substance per ml. The
measurements is carried out at temp using sodium
light. The Specific rotation can be Calculated by the
following relation:
 [α] = specific rotation, T = temperature,
 λ = wavelength, θ= optical rotation, c = concentration in
g/100ml,
 l = optical path length in dm.

10. TYPES OF MOLECULES ANALYSED BY
POLARIMETRY:
 .Molecule must be Optically active.
 Optically Active molecule contain asymmetric
carbon atom.

11. THEORY OF OPTICAL ACTIVITY
 An optically active substance is one that rotates the
plane of polarized light
Example: (1) Lactic acid
Dextro= right designated by ‘d’, (+), clockwise Levo= left designated by ‘l’, (-),
counterclockwise

12.  LEFT IMAGE:- J.B. Biot (1774-1862), who discovered optical activity in
liquids and promoted its application in the sugar industry.
 RIGHT IMAGE:- A simple diagram explaining the operation of a polarimeter.
Unpolarized light from a bulb or a flame is made linearly polarized by a
polarizer (a Nicol prism until after 1940). The direction of polarization rotates
progressively on its way through a tube containing a sugar solution. The angle
of rotation is measured by the observer, using a rotatable Nicol prism or a
combination of a quartz wedge and a fixed Nicol prism.

13. INSTRUMENTATION
 Optical activity may be detected & measured by an
instrument → Polarimeter

15.  Light source – Sodium vapor lamp
• Analyzer– another Nicol prism aligned to intercept
the linearly polarized ray as it emerges from the
sample solution
• A polarimeter consists of a polarized Light source –
Sodium vapor lamp, Polarizer –quartz prism material
and Analyzer – Nicol prism aligned to intercept the
linearly polarized ray as it emerges from the sample
solution, a graduated circle- to measure the rotation
angle, and sample tubes.

16. POLARIMETER

18. APPLICATIONS
^Quantitative application
If the specific rotation of sample is known its
concentration in the solution can be estimated.
^Qualitative application.
Optical activity is the only parameter available for
distinguishing between D and L isomeric forms.
^Saccharimetry
important practical application of polarimetry
determination of high conc. of sugars visual
saccharimeters called POLAROSCOPES

19. POLARIMETRY IS USED IN MANY INDUSTRIES
 Food industries
Polarimetry is used in food industries for quality control of
original, intermediate, and final products, the determination
of concentrations, and purity control.
 • Sugar industries: sugar (sucrose, levulose, glucose,
etc.), sugar syrups, starch, sugar-free sweeteners like
isomalt, etc.
 • Dairy: lactose, sucrose, lactoglobuline, lactic acid,
esters, etc. • Vine industries: analysis of sugar on the
vine, tartaric acid, esters, etc.
 • Fruit: analysis of sugar in fruit syrups (levulose), acids
and esters (malic acid, etc.), essential oils, etc.

20.  Pharmaceutical industries
Polarimetry is used in pharmaceutical industries for
purity control and determination of concentration of
substances according to the requirements of the
European and American Pharmacopeia by
measurement of both specific and optical rotation.
• Alkaloids: cocaine, codeine, nicotine, morphine
sulphate, etc.
• Amino acids: asparagine, glutamic acid, etc.
• Organic compounds: ascorbic acid, menthol,
camphor, etc.
Others: steroids, antibiotics, serums, vitamins, etc.

21.  Medicine
• Research of sugar and albumin in urine
• Hormone research
•Enzymology and toxicology research
Cosmetic Industries
Control of purity and identification of optically active
essential oils and essences like lemon oil, orange oil,
lavender oil, spearmint oil, etc.

22.  Research applications
• Analysis of optically active compound structure analysis
• Determination of configuration changes of solved
macromolecules
• Monitoring changes in concentration of an optically active
component in a reaction mixture, as in enzymatic scission
• Distinction of optical isomers
• Investigating kinetic reactions by measuring optical
rotation as a function of time
• Analyzing molecular structure by determining optical
rotation dispersion

23. CASE STUDY
“POLARIMETRIC DETERMINATION OF STARCH IN
RAW MATERIALS AND DISCHARGED WASTE FROM
BEER PRODUCTION”
 Abstract. Brewer’s spent grain (BGS) is a by-
product of the brewing process, consisting of the
solid fraction of barley malt remaining after
separation of worth. In this research, raw materials
and discharged waste from beer production were
evaluated on the basis of starch content, using
Ewers polarimetric method.
 Keywords: starch, polarimeter, optical rotation, malt,
brewers’ spent grain, black beer.

24.  Introduction. In preparation for brewing, barley is malted in a
controlled germination process, which serves to increase the
enzymatic content of the grain. During malting, enzymes break
down the cell structure of the endosperm, releasing nutrients
necessary for yeast growth and making the starch available for
enzyme degradation during mashing. Starch, accounting for
about 60 to 65% of the malt’s weight, is composed of amylose,
which is reduced to maltose and maltotriose and amylopectins
that decompose into glucose (Bamforth, 2003). Brewer’s spent
grain (BGS) is a by-product of the brewing process, consisting of
the solid residue remaining after mashing and lautering; it
consists primarily of grain husks and other residual compounds
not converted to fermentable sugars by the mashing process
(Xiros and Christakopoulos, 2009). BSG is produced in the
largest quantity, corresponding to around 85 % of the total
generated and it is estimated that about 200 t of wet spent grain
with 70 to 80 % water content are produced per 10.000 hl of
produced beer (Kunze, 1996).

25.  Aims and objectives. Raw materials and discharged waste from beer
production were evaluated on the basis of starch content, using Ewers
polarimetric method. This method was used because it provides accurate
results even in samples which contain proteins, sugars and hemicellulose in
high quantities. Materials and methods. All the materials (malt, brewers’ spent
grain) were supplied by the microbrewery of the Faculty of Food Science and
Technology. The BSG used in this work was obtained from a process
employing 100 % malt, without addition of other cereal adjuncts. Caramelized
and black malt are added in smaller quantities (5-10 %) to obtain darker
colors and to enhance flavor characteristics. The polarimetric determination of
starch content is based on the optically activity of starch. Due to the fact, that
starch cannot be dissolved in water, hydrochloric acid is used. After
dissolution, the sample needs to be clarified, filtrated and measured in a
polarimeter. The optical rotation of all samples was measured at 20°C by
using a sample cell of 200 mm optical path length. Results are presented as
the mean of two replications with standard deviation. Moisture was
determined by weight difference before and after heating at 130 ºC for 1.5 h.

26.  Results and Discussion.
Chemically, BSG is rich in polysaccharides, protein
and lignin. Robertson et al., 2010 stated that residual
starch can contribute up to 13% of the dry weight and
the spent grain from lager malts has higher protein
content than that from ale. The starch level present in
brewers spent grain was negligible, 5.09±0.08 % due
to extensive amylolysis during mashing, compared
with the level found in malt (57.78±0.34 %, w/w). A
similar value was also reported in studies of
Makowska et al., 2013, which identified the grains
starch content of 4.56±0.42 %; similar values were
also reported, both for malts and brewers spent grain
by Waters et al., 2012.

28.  Conclusion.
Chemical composition of BSG varies according to
barley variety, harvest time, malting and mashing
condition, type and quality of secondary raw materials
and the brewing process. Methods used to determine
the starch provides accurate results which are in
accordance with values reported in the literature.


29. THANK YOU…