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K.A.U. FACULTY OF SCIENCE
BIOCHEMISTRY DEPARTMENT
BIOC 341
‫جتميع وتنسيق‬
‫أميمة نيازي‬
[email protected]
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Viscosity describes how a liquid resists the laminar movement of two
neighboring layers. This resistance to flow can be seen with gases, liquids and
even solids.
Stoke's law:
In laminar flow, a ball with diameter d moving through a liquid with viscosity
η has a speed proportional to the frictional force.
Fr = 3 π η d v
Intrinsic viscosity:
The intrinsic viscosity can be extrapolated by measuring several polymer
solutions with different concentrations. It corresponds to the viscosity of a
solution at concentration c=0. From this result, the molecular weight average
of a polymer can be determined using the Mark Houwink equation.
Viscosity can be readily followed using an
 Ostwald viscometer (Fig1).
 Falling ball viscometer
Ostwald viscometer: This, essentially, consists of a capillary tube down which
a known volume of protein solution is allowed to flow under gravity. The time
taken for this flow is measured (t1 and also that of the solvent (t0); the relative
viscosity is then given by:
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Relative viscosity ηrel =η1/η0 = ( t1/t0 ) X ( ρ1/ρ0)
where n1 is the viscosity of the protein solution of density p1 and n0 the
viscosity of the solvent of density ρ0. If the densities are taken to be the same
then the expression = ( t1/t0 )
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Fig. 1 The Ostwald viscometer
fig 2 BROOKFEILD VISCOMETER
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MATERIALS
1. Viscosity is very sensitive to temperature, so all solutions and the
viscometer must be kept at 30°C in the water bath.
2. Ostwald viscometer
3. Water bath at 20°C
4. Glucose
5. Dextran
6. Glycerine
7. Stop watch accurate to at least 0.1 s
250 ml
METHOD
,
Always handle the viscometer by one limb only and never squeeze the
two arms together. Rinse the viscometer with KC1 solution and place it in
position in water bath by carefully clamping one limb. Check that it is
vertical using a plumb line and introduce exactly 20 ml (or the volume
marked on the viscometer) of water at 20°C into the bulb A with a
syringe or pipette. Leave for 5 min to equilibrate, then either apply
positive pressure to the wide limb (I) or gentle suction to the other limb
(II) until the meniscus rises above the upper graduation mark B. Release
the pressure and measure the time (to the nearest 0.1 s) for the liquid to
flow between the two graduation marks B and C. Repeat the experiment
until the flow times agree within 0.2 s and calculate the average flow time
: (t0), which is the solvent, and then with the glycerin dissolved in the
water (T1. Select convenient concentrations of glycerin and calculate the
relative viscosities (tl/t0) using the values from the curves.
Ref.: D.T.Plummer, An introduction to Prac. Bioc. MC Grow Hill
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Name
Computer no.
Substance
T1
T0
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Rel. viscosity
-PolarimetryStereoisomerism:
Stereoisomerism occurs when two or more compounds have the same
molecular formula AND the same structural formula BUT differ in spatial
arrangements of their bonds. There are two main sub-divisions of
stereoisomerism:
(a)Geometrical Isomerism:
(b) Optical isomerism.
Alpha amino-acids:
RCH(NH2)COOH
RCH(+NH3)COO-
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Polarimetry Fundamentals
Polarimetry is a sensitive, nondestructive technique for measuring the
optical activity exhibited by inorganic and organic compounds. A
compound is considered to be optically active if linearly polarized light is rotated
when passing through it.
The amount of optical rotation is determined by then 1. molecular structure and
2.concentration of chiral molecules in the substance. Each optically active
substance has its own specific rotation as defined in
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Biots law
Matereal :Amino acids and carbohydrates solutions
Method: Polarimeter readings were taken at intervals of a 10 min.then every few
hours during 24 hours,. A Schmidt and Haentsch polarimeter was employed,and
a Zeiss electric sodium vapour lamp was used as asource of light (A= 5893 A.).
The polarimetric method is a simple and accurate means for determination and
investigation of structure in macro, semi-micro and micro analysis of expensive
and non-duplicable samples. Polarimetry is employed in quality control, process
control and research in the pharmaceutical, chemical, essential oil, flavor and
food industries. It is so well established that the United States Pharmacopoeia
and the Food & Drug Administration include polarimetric specifications for
numerous substances
Pharmaceutical Industry
Determines product purity by measuring specific
rotation and optical rotation of:
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Amino acids
Antibiotics
Dextrose
Steroids
Amino sugars
Cocaine
Diuretics
Tranquilizers
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Analgesics
Codeine
Serums
Vitamins
Flavor, Fragrance and Essential Oil Industry
Utilizes polarimetry for incoming raw materials
inspection of:
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Camphors
Gums
Orange oil
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
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Citric acid
Lavender oil
Spearmint oil
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Glyceric acid
Lemon oil
Food Industry
Ensures product quality by measuring the
concentration and purity of the following compounds in
sugar based foods, cereals and syrups:
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Lactose
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Raffinose
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Various Starches 
Carbohydrates
Fructose
Levulose
Sucrose
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Glucose
Maltose
Xylose
Natural mono-saccharides
Chemical Industry
Analyzes optical rotation as a means of identifying and
characterizing:
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Biopolymers
Natural polymers
Synthetic polymers
REFERENCES



http://www.rudolphresearch.com/polarimetry.htm
http://www.wpbschoolhouse.btinternet.co.uk/index.htm
07/03/2007A COMPARATIVE INVESTIGATION OF URINE-AND
SERUM-PROTEINS IN NEPHRITIS. BY ELSIE MAY
WIDDOWSON.From the Courtauld Institute of Biochemistry, the
Middlesex Hospital, london, W.
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Name
compound
time
Computer no.
Con.
Optical rotation
Sp.Rotation=
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L.
[α]λT
α
C
L
10
20.5
?
10CM
?
100
100MG% 20CM
5
10
100G%
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?
SCATTERING
LIGHT SCATTERING
Refractometery
PRICEPLE:
Refractometers are used to determine a concentration of a particular
substance within a given solution. They operate based on the principle
of refraction. When rays of light pass from one medium into another, they
are bent—either toward or away from a normal line— between the two
media.
www.labsupply.com
The angle between the normal ray and the incident ray is called the angle
of incidence. The angle between the normal ray and the refracted ray is
called the angle of refraction. The Figure up demonstrates this using a
pencil resting in a container of water. As you can see, the light ray passes
from the air into the water and is bent toward the normal ray or, the angle
of incidence.
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www.vallyventner.com
www.freeform
The angle of refraction is related to an index value called the index of
refraction. Each compound has a specific index of refraction. The angle
of refraction is dependent on the composition of the media and on the
temperature—this composition dependency is what makes refractometers
so useful. As the concentration of a particular
Compound in a solution increases, so does the degree to which the light is
bent. Also, it is important to determine the temperature of the testing
environment since temperature affects the angle of refraction.
Let’s say we want to determine the salinity (NaCl concentration) in a
brine solution. For each percent salinity value there is a corresponding
angle of refraction. First, we determine the angle of refraction. Then, we
convert the angle of refraction to percent salinity. This percentage is the
concentration of NaCl in our brine solution. To make the conversion
easier, refractometers are available with scales that are calibrated to read
the desired value directly—in this case, percent salinity.
Refractometers are available with a variety of scales:



Salinity: Mentioned above.
Brix: Measures percent sucrose. Used in the food and beverage
industry for quality control.
Coolant Freezing Point: Determines the effectiveness of ethylene
glycol and propylene glycol coolants.
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
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Clinical: Measures Serum albumen and Urine specific gravity (e.g.
to test for urine drug sample tampering).
Serum Protein
Specific Gravity
Calibration and Use
1. Calibrate the refractometer with a standard solution before use.
Since the reading will be affected by temperature changes, it is best
to calibrate at the temperature of the test environment. If this is not
possible, correction charts may be used to correct for this effect.
Some refractometers have automatic temperature correction
(ATC), a feature that allows the instrument to automatically correct
for temperature differences.
2. Place a small amount of liquid (usually 2-5 drops) on the prism and
secure the cover plate—this will evenly distribute the liquid on the
prism.
3. Point the prism end of the refractometer toward a light source and
focus the eyepiece until the scale is clearly visible.
4. Read the scale value at the point where the dark and light portions
meet.

References
Elements of Physics, Fifth Edition. George Shortly and Dudley Williams. Prentice Hall Publishers; 1971
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compound
Ref. Index
Con.
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Temp.
Principle
Turbidity refers to the number of suspended particles in a liquid.
Turbidity is tested using a turbidometer, a diagram of which is shown
below.
Fig ( 9 )
This turbidometer is also known as a nephelometer. In the turbidometer,
light shines through a sample of water. If the light strikes a colloid, the
light is scattered, bouncing off the colloid and reflecting upward. If the
light does not strike a colloid, it shines through the water sample. The
meter measures how much light is reflected off colloids in the water.
Clear water will reflect little light while turbid samples, like this one, will
reflect large amounts of light.
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MATERIALS
1. Dionized water
2. Distilled water
3. DIF Conc. OF sodium Chloride
METHOD
,
Tubidimeter Instructions:
Turbidity is measured with a turbidometer. A sample is collected in a
sample bottle. The turbidometer is calibrated with a "blank" (distilled
water) that allows 100% (all light passes through the water) transmission.
The blank is replaced by the sample. Suspended material in the sample
will block some of the light so the transmission reading should be less
than 100%. The more turbid the water is, the lower the transmission will
be.
1.Fill sample cell with sample water and cap.
2.Wipe cell with Kim Wipe to remove water and finger prints.
3.Press "I/O" to turn on instrument. Lay instrument on flat, level surface
for test. Do not hold in hand.
4.Put sample cell into cell compartment so the diamond mark aligns with
raised orientation mark on front of cell compartment. CLOSE COVER.
5. Press RANGE key to select "AUTO RNG" (automatic range selection).
6.Press SIGNAL AVERAGE key. "SIG AVG" will appear.
7.Press "READ". After the lamp symbol turns off, record turbidity in
NTUs (Nephelometric Turbidity Units)
Application:
Test is done to:
1.Determine water quality in a stream.
2.Dissolved Oxygen Test
3.Formation of antigen antibody complex.
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Maintenance
When not in use, the turbidometer and vials should be in kept their blue
field case. The instrument should be kept dry and clean both inside and
out. The vials should be kept clean and free of abrasions. After each
measurement, the vial and lid should be rinsed twice with deinonized
water and stored filled with deionized water.
Vials should never be stored inside the instrument.
Instruments should never be stored in temperatures below freezing or in
extremely hot temperatures.
http://water.me.vccs.edu/concepts/turbidity.html
http://www.owrb.ok.gov/quality/monitoring/bump/pdf_bump/sops_for_st
reams/turbidity.pdf.
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Name
Computer no.
Substance
Turbidity
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