Download 224 PHT student`s handout

Laboratory Handout
PHT 224
Laboratory Instructions and Regulations:
1.
2.
3.
4.
Practice good manners in the laboratory all times.
Lab coats must be clean and worn by all students.
Hair must be tied back.
Personal cleanliness and neatness are important. This includes a clean
lab coat and hands.
5. Each student must have a metric weights set.
6. Lab notes must be available in each lab.
7. Never work in laboratory sections other than your own without first
obtaining permission from the instructor in charge of the laboratory.
8. Learn how to use balances and other equipments in the lab properly
and take care of them.
9. Keep your desk orderly at all times. Clean your equipments, bottles,
desk, and shelf area daily.
10.Return all stocks bottles, special equipments and books to their proper
location when through with them.
11.Do not place insoluble solids such as ointments or oils in the sink.
Wrap these substances in paper towels and place in trash containers.
12.Keep general lab areas neat and clean. Pay special attention to sinks,
floors, and shelves.
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Lab No: 1
Prescription Balance:
 Definition of a balance:
It is an instrument used for determination of the relative weights of
substances.
 Types of balances:
1. Analytical balance: for very fine weights.
2. Class A: which is most commonly used and any pharmaceutical
department has it.
3. Bulk balance: used for higher weights.
 Structure of a torsion balance.
The balance consists of:
1. Two pans.
2. Two beams.
3. 2 leveling screws or thumb screws.
4. Central lock.
5. Graduated scale (0.1g -1 g = 100 mg - 1000 mg) so the balance is capable
of weighing from 0.1 to 1 g without using external weights.
6. Plate index that contains the pointer.
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 Sensitivity requirement or sensibility reciprocal of a prescription balance:
Is the mass (in mgs) required to produce a pointer deflection of one scale
division from the rest point. i.e. It is the smallest weight which change the
pointer one division.
The smaller the weight required to produce this one division displacement,
the more sensitive the balance is.
% Error = Sr / wt
 Balance capacity:
Is the maximum quantity that can be weighed on the balance.
Capacity of a balance is usually written on the metal plate attached to the
balance. If not, it is assumed to be 15.5 g.
How to use the prescription balance:
The balance is probably one of the most important and extensively employed
instruments in the practice of modern pharmacy. It is a sensitive and expensive
instrument; that is why it is important to learn how to manipulate and maintain it properly
at all times.
Fundamental Techniques for Using the Balance:
1. Before attempting any weighing, you should understand the underlying principles
of the balance and how does it work.
2. The balance should be locked when not in use to take any stress off the
mechanism.
3. The balance should first be properly cleaned. All spilled materials should be
wiped off and the balance pans cleaned and polished. After cleaning, the balance
should be carefully checked to see that the pans have been properly placed in their
places and that the balance is ready for operation.
4. Level the balance by adjusting the leveling screws under the front corners. This is
done by looking at the pointer, if it is to the right side, rotate the front leveling
screws to the inside and vice versa.
5. Suitable weighing papers of equal size should be folded diagonally and placed on
each of the pans. Never weigh a substance directly upon the pans.
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 Why do we use weighing papers?
1. Protect the pans from chemicals, as it could be corrosive.
2. Prevent contamination of one substance with another.
3. Help in fine transfer (it serve as a transfer funnel).
4. No need to wash pans.
 What are the propertied of weighing paper?
1. Glazy surface so the powder won’t stick to it.
2. Its size should be relative to the amount of substance to be weighed.
3. The two wax papers should be of the same size and folded diagonally
to take the shape of a dish.
6. The amount of the substance to be weighed should be computed and the correct
weights chosen and checked. These weights are placed upon the right hand pan
of the balance.
7. After the proper weights have been placed upon the right hand pan, approximately
the correct amount of material should be placed on the weighting paper on the left
pan.
 The material to be weighed should be transferred directly from the
container to the balance’s pan by means of a spatula.
 Holding the container close to the pan so as to avoid any spilling of the
substance.
 Release the locking device and check if you need to add or take away
materials. You have to keep in mind that the balance should be locked
between each addition or subtraction of materials from the balance
until the exact amount is measured.
 In transferring a material by spatula, the material may be lightly tapped
from the spatula when the correct amount to be measured is nearly
approached.
8. After the balance comes to rest and the exact amount has been weighed, lock the
balance. Remove the weights from the balance pan and check the weights again to
see that the correct amount has been weighed. Replace the weights in the weight
box.
9. Remove the substance weighed and place it in a suitable container to be used in
the preparation or label the materials by writing the name and weight of the
substance on the weighing paper.
10. Remove the weighing papers and discard if no further weightings are to be made.
11. Check to see that the balance is locked and in the case of glass-enclosed balances,
close the glass lid.
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12. The preceding rules apply to liquids to be weighed as well as to solids.
Techniques are often employed in weighing liquids depending upon the type of
liquid. If the liquid is a heavy liquid of tarry consistency, a suitable wax cup or
was weighing paper should be used. And in the weighing of less viscous liquids,
such as glycerin, it is often advantageous to use a tarred vessel such as a beaker
which is counterbalanced.
Problems:
1- Suppose the balance pointer rests at the zero mark with no mass, and at 2.5 divisions
following the addition of 20 mg. Calculate balance sensitivity.
2- If the sensibility reciprocal of a balance is 3 mg. What is the minimum permissible
quantity that can be weighed on the balance? (Assume a ±5 % error unless other wise
stated).
3- Calculate the % error involved in weighing 200 mg on a balance having a sensitivity of
6 mg.
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Laboratory Handout
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Trituration
Definition:
Trituration is the process of reducing substances to fine particles by rubbing them
in a mortar with a pestle.
Or it is the process whereby a mixture of fine powders is intimately mixed in a
mortar.
Benefits of Trituration:
The circular mixing motion of the pestle in the powders contained in a mortar result
in:

Blending them.

Breaking up soft aggregates of powders.
One should never add several components to a mortar all at once instead select the
granular or crystalline materials and grind each individually to as fine a state as
possible.
Uses:
Trituration is used in diluting potent medicinal substances. These dilutions offer
a means of obtaining conveniently and accurately small quantities of potent drugs
for compounding purposes.
N.B. always use a glass mortar for colored materials.
Geometric Dilution:
To blend the powders together, use the geometric dilution method as follows:
 Add the ingredients of the smallest bulk volume to the mortar first.
 Follow it with equal volumes (visually estimated) of the remaining
ingredients.
 Each addition is carefully triturated.
In this manner equal distribution of the smallest quantities among the larger more bulky
components is assured.
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Laboratory Handout
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Aliquot Method of Measuring
When a degree of precision in measurement is required that is beyond the
capacity of the instrument at hand, the pharmacist may achieve the desired precision by
measuring and calculating in terms of aliquot parts.
Definition:
An Aliquot Part is any part that is contained a whole number of times in a quantity.
Thus, 2 is an aliquot part of 10; and since 10 / 2 = 5, 2 is called the fifth aliquot of 10.
Again, 4 is an aliquot part of 16 “the 4th aliquot of 16”.
.)‫الجزء الذي يتكرر عدد صحيح من المرات في كميه معينه (مضاعفات العدد‬
When To use the Aliquot Method of weighing?
The aliquot method of weighing is used when small quantities of a substance are
to be weighed within the degree of accuracy obtained. It is very useful specially when
dealing with very potent drugs such as atropine sulfate.
Procedure:
1. Select some multiple of the desired quantity that can be weighed with the required
precision. This is done by calculating the smallest quantity of the substance that
can be weighed with the required precision.
2. Dilute the multiple quantity with an inert substance (diluent) that is compatible
with the given preparation.
3. Weigh the aliquot part of the dilution that contains the desired quantity.
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Exercises on Triturating and Aliquot Method of Weighing:
Example # 1:
Rx
Potent drug (Cu so4)
0.0005 gm
Lactose
Q.S.
DTD caps # 12
Prepare only the aliquot in the above preparation.
SR = 6 mg
% Error (degree of accuracy) =  5%
Show all calculations.
Example # 2
A torsion prescription balance has a SR of 4 mg. Explain how you would weigh 5
mg of a potent drug with an accuracy of  5%, using lactose as the diluent.
Example # 3
Explain how you would weigh 15 mg atropine so4 (13 mg dose is ineffective and
17 is lethal) on a torsion balance having a SR of 6 mg and with a degree of
accuracy of  5%.
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Lab No: 2
Measurement of Volume of Liquids
Liquid measurement can be carried out by using graduates, burettes, and graduated
pipette.
Demonstrate to the students:
1. Burettes and their stands.
2. Pipettes: graduated or bulbed, which is more accurate.
3. The two types of graduates, which are:
 Conical graduates: conical measure and conical flask.
 Cylindrical graduates: Such as measuring cylinder. These are preferred to
conical graduates because the smaller the diameter at the measuring point,
the greater the degree of accuracy obtained.
 Beakers are not accurate.
Graduated systems available for both cylindrical and conical graduates:
 Apothecary single scale (¼, ½, ¾ ounces).
 Metric single scale (ml).
 Apothecary and Metric double scale.
General notes:
-Single scale graduated cylinder is the most accurate. (Since the curvature at the lower
portion and the sloping sides of the conical graduate introduce errors).
-The degree of error in measuring increases as the volume you are measuring decreases.
-It is recommended that a volume not less than one-fifth the volume of a graduate be
measured (20%).
-It is important to pick the right graduate to optimally measure a particular volume of
fluid.
-Choose a graduate which has a maximum capacity closest to but greater than the volume
you wish to measure.
What graduate would you use to measure 60 ml?
-The graduates are designed to take into account the small amount of fluid that will
adhere and remain on the side of the graduate after delivery.
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The Meniscus:
It is the curved surface of the liquid formed by the attraction of the liquid to the
sides of the graduate.
Always read the bottom of the meniscus. If the liquid is opaque, read the top of the
meniscus.
Upper Meniscus
Lower Meniscus
Accuracy in measuring volume of liquids depend on:
1- The quantity of the liquids being measured (less quantity → more
error).
2- The nature of the liquid being measured (viscous or watery).
3- The type of graduate used (conical or cylindrical).
4- The size of graduate used (suitable to the volume measured).
5- The care and skill of the pharmacist.
Dropper Experiment:
Calibrate the commercial dropper in a 1 oz. Dropper-service bottle by counting
the number of drops of distilled water required to fill the 2 ml mark of the cylindrical
graduate. Be sure to hold the dropper in a vertical position. Repeat holding the dropper
at a 45o angle. Repeat using glycerin and Tr. Belladonna. Be sure to wash the dropper
out carefully between determinations.
Number of drops / 2 mL
Liquid
Vertical
Water (watery, aqueous)
Glycerin (viscous)
Tr. Belladonna (alcoholic)
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45o
Laboratory Handout
PHT 224
Labeling
Types of Labels:
1. Red Labels: used for preparations intended for external use (e.g. ointments,
creams, lotions….).
2. White Labels: used for preparations intended for oral or internal use (e.g. syrups,
suspensions….).
Directions for Preparing a Label:
1.
2.
3.
4.
All labels should be typed.
A label is selected in proper size to the container (not too large).
It should be neat, clear, and accurate.
Labels should be attached to the container so that the top of the label is from ¼ to
¾ of an inch from the top of the bottle.
5. Use appropriate accessory labels such as: Shake the Bottle, Take With Full Glass
of Water, It May Cause Drowsiness….
In the laboratory, the following information should appear upon the label:
Non-prescription drugs:
1. The official title of the preparation and whether it is U.S.P., N.F., or Non-official.
2. Your full name.
3. Date.
Preparation
Student Name:
Date:
Prescription drugs:
1.
2.
3.
4.
5.
6.
7.
The prescription number (desk number).
Doctor’s initials and last name.
The name of the patient.
Rx No.
Directions to the patient.
Patient Name:
Official title of the preparation
Directions to patient:
Student’s First and last name.
.
.
.
.
Date.
Preparation:
Student Name:
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Date:
Date:
Doctor:
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Laboratory Handout
PHT 224
Reducing and Enlarging Formulas
Formulas that specify amounts of ingredients
Total amount specified
in formula
=
Quantity of each ingredient
in formula
Total amount desired
x
x = Quantity of each ingredient in amount desired
Example:
From the following formula, calculate the quantity of each ingredient required to
make 240 mL of calamine lotion.
Rx
Calamine
Zinc Oxide
Glycerin
Bentonite Magma
Calcium Hydroxide solution, to make
80 g
80 g
20 g
250 mL
1000 mL
Formulas that specify Proportional Parts
Total number of parts
in formula
Number of parts of
each ingredient
Total amount desired
=
x
x = Quantity of each ingredient in amount desired
Example:
From the following formula, calculate the quantity of each ingredient required to
make 1000 g of Ointment.
Rx
Coal Tar
Zinc Oxide
Hydrophilic Ointment
5 parts
10 parts
50 parts
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What should be available to you in the lab?
Measuring cylinder.
Beaker.
Conical flask.
Funnel (regular and separating).
Funnel stand.
Filter papers.
Water bottle.
Porcelain mortar and pestle.
Glass mortar and pestle.
Glass rod.
Plastic spatula.
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Lab No: 3
Solutions
Solution for oral dosage form can be Elixir, Linctus, Mixture and oral
solution.
Elixirs: are solutions for oral administration. The vehicle usually contains
syrup, ethanol or other cosolvents to give a clear solution and pleasant taste.
Linctuses: are formulated with syrup as the vehicle and are designed to
soothe sore mucous membrane in the treatment of cough.
Mixtures: are liquid preparations for oral administration and contain
medicaments dissolved and/ or suspended in water.
Oral solutions: contain one or more ingredients dissolved in a suitable
vehicle
Advantages:
1) Absorption of the drug is rapid
2) Easy to swallow
3) Uniform distribution, no need to shake.
Disadvantages:
1) The drug is less stable in the solution form
2) Unpleasant taste may be difficult to mask
3) Measurement depends on the accuracy and reliability of the patient.
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Cough Mixture
Rx
Ammonium Chloride
Potassium Iodide…………..aa……… 2.5g
Codeine Phosphate…………………...0.18 g
Simple Syrup……………………….. 10 ml
Color & flavor
………………………. Q.S
Purified water…………….To……… 60 ml
Fiat: Mist
Sig: 5 ml q 3-4 hr prn cough
Calculations:
Procedure:
1. In 2/3 amount of vehicle, dissolve NH4CL, KI, and Codeine
phosphate.
2. Filter if necessary through a cotton wool wetted with water.
3. Add syrup and color.
4. Complete to volume with water.
5. Transfer to a clean bottle and fix the label.
Labeling:
Name:
Date:
Uses:
Antitussive mixture.
Role of Each Ingredient:
 NH4CL: is an expectorant and it works by increasing the
volume of bronchial secretions and therefore this volume will
facilitate the removal of sputum.
 KI: liquefy sputum (mucolytic).
 Codeine phosphate: Cough suppressant.
 Simple syrup: sweetening agent.
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Laboratory Handout
PHT 224
Cough Mixture for Diabetic Patients
Rx
Ammonium Chloride
Potassium Iodide……………………….aa…………2.5g
Codeine Phosphate………………………………….0.18g
Water………………………………………………..10 ml
Saccharine Sodium (1% solution)…………………..0.018g
Color & flavor
………………………………… Q.s
Methyl cellulose 1%……………………To……… 60 ml
Calculation:
Procedure:
1. In 10 ml water, dissolve Ammonium Chloride, Potassium
Iodide, and Codeine Phosphate.
2. Filter if necessary through a cotton wool wetted with water.
3. Add saccharine solution and coloring agent.
4. Complete to volume with methyl cellulose.
5. Transfer to a clean bottle and fix the label.
Labeling:
Name:
Date:
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Uses:
Antitussive mixture.
Role of each ingredient:
 NH4CL: is an expectorant and it works by increasing the
volume of bronchial secretions and therefore this volume will
facilitate the removal of sputum.
 KI: liquefy sputum (mucolytic).
 Codeine phosphate: Cough suppressant.
 Saccharine Sodium: artificial sweetening agent used to mask
the better taste of the active ingredient.
 Methyl cellulose: increase the viscosity of the mixture
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PHT 224
Lab No: 4
Aspirin Solution
Rx
Aspirin
Potassium Citrate
Spirit Chloroform
Simple Syrup
Purified Water
1.25 g
2g
1 ml
10 ml
60 ml
To
Fiat: solution
Sig.: fl  i q 4 hr
fl  i  4ml  5ml only in Sig.
Calculations:
Procedure:
1. Suspend Aspirin in about 1/3 amount of vehicle in a small beaker.
2. In another container, dissolve potassium Citrate in another 1/3 the
amount of vehicle  16 ml of water.
3. Add the citrate solution (in # 2) gradually to the suspension of aspirin
(in # 1) with stirring until complete dissolving of aspirin takes place
 clear solution.
4. Filter, if necessary, through a cotton wool wetted with water.
5. Add spirit chloroform and simple syrup.
6. Complete to volume (60ml) with the rest amount of water.
7. Transfer to a clean bottle and fix the label.
Uses:
Aspirin is used as an analgesic and antipyretic agent.
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Label:
Name:
Date:
Role of each ingredient:
1.
2.
3.
4.
Aspirin: analgesic and antipyretic (the active constituent).
Potassium Citrate: Solubilizing agent.
Spirit Chloroform: flavoring agent.
Simple Syrup: Sweetening agent.
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PHT 224
Calcium Lactate Solution
Rx
Calcium Lactate
Ephedrine HCl (1:10)
Antazoline HCl
Liquid extract of liquorice
Simple syrup
Water
to
0.5 g
0.015 g
0.05 g
1 ml
5 ml
15 ml
Fiat: Solution.
Sig: One flzss t.d.s
Mitte: V doses
Calculations:
Procedure:
1. Heat about 2/3 of water at 70o C and dissolve Calcium Lactate in it.
2. Cool the solution and dissolve Ephedrine Hcl and Antazoline Hcl in it.
3. Filter if necessary through a cotton wool wetted with water.
4. Add the extract and the syrup to the filtrate.
5. Complete to volume with water.
6. Transfer to a clean bottle and fix a label.
Label:
Name:
Uses:
Antiallergenic and antihistaminic.
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Date:
Laboratory Handout
PHT 224
Role of each ingredient:
 Calcium Lactate: Excellent source of calcium ion in treatment of
calcium deficiency and antiallergenic.
 Ephedrine Hcl: Bronchodilator.
 Antazoline Hcl: Antihistaminic
 Liquid extract of Liquorice: Has slightly aromatic sweetening taste
and flavoring action so it is used to mask the better taste of
Ephedrine Hcl and Antazoline Hcl.
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Lab No: 5
Iron Ammonium Citrate Mixture
Rx
Iron Ammonium Citrate
Tincture of Nux Vomica
Simple Syrup
Peppermint Water
To
5g
3 ml
10 ml
90 ml
Fiat: mixture
Sig: flzss t.i.d. p.c.
Mitte: 45 ml
Theory:
When Iron Ammonium Citrate is added to water, its ions will make grouping
(agglomeration) forming an insoluble mass, which is difficult to be
dissolved.
So the addition of Iron should be gradual by sparkling small amounts and
stirring continuously.
Calculations:
Procedure:
1. Weigh the calculated amount of Iron Ammonium Citrate.
2. In a beaker, put 2/3 amount of vehicle.
3. Sprinkle Iron Ammonium Citrate in small amounts to avoid formation
of undissolved mass. Stir after each addition.
4. Filter through cotton wool wetted with water.
5. Add tincture of Nux Vomica and simple syrup.
6. Complete to volume with peppermint water.
7. Transfer to a clean bottle and fix the label.
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Laboratory Handout
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Label:
Name:
Date
Uses:
As a tonic solution used in iron deficiency anemia.
Role of Each Ingredient:
 Iron Ammonium Citrate: The active ingredient.
 Tincture of Nux Vomica: Appetizer because the alkaloid in it
stimulate gastric acid secretion.
 Simple Syrup: Sweetening agent.
 Peppermint Water: Vehicle and flavoring agent.
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Laboratory Handout
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Potion Reviere
Example of an acid-base reaction
It is an example of effervescent mixture containing a recently
prepared salt by combining an acid and a bicarbonate or carbonate at the
time of administration and producing by this means a mixture charged with
Carbon dioxide.
Sodium Bicarbonate + Citric acid
Sodium Citrate Salt + Water +
Carbon dioxide
CH2-CooH
3 NaHco3 + CoH-CooH
CH2-CooH
CH2-CooNa
COH-CooNa + 3H2O + 3 CO2
CH2-CooNa
Solution # 1
Sodium bicarbonate Solution
Rx
Sodium Bicarbonate
Simple Syrup
Water
To
grV
Fl  ss
flzss
Solution # 2
Citric acid solution
Rx
Citric acid
Syrup of lemon
Water
To
grV
Fl  ss
flzss
Fiat: mist
Mitte: III doses
Sig: One flzss of each bottle O. sec. H.
Calculations:
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Laboratory Handout
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Procedure:
1. In 2/3 amount of vehicle (25 ml water) dissolve NaHco3.
2. Filter if necessary through cotton wool wetted with water.
3. Add syrup.
4. Complete to volume with water.
5. Transfer to a clean bottle and fix the label.
6. Repeat the same procedure for solution # 2 in a separate bottle.
Label:
Name:
Date:
Name:
Date:
Uses:
Carbon dioxide has an antiemetic effect due to relaxation of smooth
muscle of the stomach.
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Lab No: 6
Effect of temperature on the dissolution rate
Dissolution: is the release rate of the drug from the dosage form per unit
time using special apparatus (Dissolution Apparatus) with specific condition
stated by the pharmacopeia.
There are two dissolution apparatus:
1. Apparatus I : contain basket
2. Apparatus II: contain paddle
The condition will specify the following:
 Dissolution medium
 Volume of the dissolution medium
 Temperature
 speed
 Time interval for sample withdrawal
Practical procedure:
 You will be provided with acetaminophen granules with different
particle size.
 Dissolution condition:
1. Apparatus II
2. Dissolution medium: 900 ml phosphate buffer pH 5.8
3. Temperature 37oC and 25oC
4. Speed : 50 rpm
5. Time interval ( 5, 10, 15, 20, 25, 30,45)
 Weigh 270 mg of the granules and put it in the dissolution flask
 Take 5 ml sample in each time, make the required dilution and
measure the absorbance at 243nm using spectrophotometer.
 Calculate the concentration and the % release of the drug
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Results:
Time
Abs
Conc
%release =
=(abs/E1%)*(900/100)*d.f
(conc/original) *100
5
10
15
20
25
30
45
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Lab No: 7
Surface tension (
Cohesive Force: is that which occurs between molecules of one phase.
Adhesive Force: is that which occurs between molecules of two phases.
Surface Tension: is the force per unit length (dyne/ cm) that must be applied
parallel to the surface so as to counter balance the net inward pull of
molecules of interface together.
Method of determination of surface tension:
1. Drop weigh method
2. Drop number method
3. Capillary rise method
4. Differential capillary height method
Drops weigh method:
The surface tension of the liquid is related to the weight of the drop of that
liquid which falls freely from the end of a pipette.
Procedure:
1. Take a clean dry beaker and weigh (W1)
2. Using clean pipette , put 10 drops of water in the beaker and weigh
(W2)
3. Calculate the weight of 10 drops = (W2 – W1= W3)
4. Calculate the weight of one drop= (W3 / 10)
5. Repeat the same procedure using other liquids
6. Calculate the surface tension of the other liquids
(m: mass of one drop)
liquid
W1
W2
W3
Water
Olive oil
Oleic acid
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Weight of
one drop
Laboratory Handout
PHT 224
Drop number method:
The surface tension of the unknown solution may be obtained by counting
the number of the drops in certain volume of the liquid.
Procedure:
1. Using graduated pipette, take 0.5 ml of water and count the number of
drops in this volume (n1)
2. Wash the pipette and repeat the procedure using other liquids
liquids
Number of drops
Water
Olive oil
Oleic
acid
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Lab No: 8
Interfacial tension
Definition: it is the force per unit length existing at the interface between tow immiscible
phases.
 Interfacial tension is less then surface tension because the adhesive force between
tow liquid phases forming the interface is greater than when a liquid and gas exist
together.
 If the tow liquid is miscible so, no interfacial tension will exist between them.
Determination of interfacial tension:
You will be provided with water, olive oil and oleic acid.
Density: d olive oil = 0.91,
d oleic acid = 0.887
Procedure:
1. Take a clean 1 ml graduated pipette and measure 0.5 ml of heavier liquid (water).
2. Dip the pipette in a beaker contains the lighter liquid (olive oil) and count the
number of the drop of this volume.
3. Calculate the volume of one drop
4. Repeat the same procedure using the other liquid.
Calculation:




V: volume of one drop
D1: the density of heavier liquid
D2: the density of lighter liquid
K: constant
Calculate K then calculate the interfacial tension between water and oleic acid.
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Lab No: 9
Adsorption isotherm
Determination of the Adsorption Parameters of Oxalic acid on Charcoal
Objectives:
To demonstrate the adsorption phenomena and to show students how to
determine the adsorption parameters.
Theory :
Colloidal dispersions have to the property of adsorption solutes at their
surfaces. Thermodynamically such adsorption process occurs to reduce the
surface free energy of the dispersion and therefore increase its stability.
The degree of adsorption of a solute (adsorbate) on the adsorbent depends
on the chemical nature of the adsorbent and the adsorbate, the specific
surface area of the adsorbent, the temperature and the concentration or the
pressure of the adsorbate.
At constant temperature the relation between the amount adsorbed and
concentration in a limited concentration range may be represented by one of
the three adsorption isotherms of Freundlich (Eq. 5), Langmuir (Eq. 7)
and BET (Brunauer Emmett and Teller).
Freundlicn isotherm
y = x/ m = kC1/n
(5)
Where x = weight of adsorbate in grams, adsorbed by m grams of the
adsorbent.
K & n = are constants for a given substance and solid.
Ce = equilibrium concentration.
Ym = weight of the adsorbate in grams, adsorbed by one gram of the
adsorbent to form a monolayer.
b= Equilibrium constant of the adsorption process.
Freundlich equation can be linearized by taking the logarithmic form ( Eq. 6) of
Eq .5. However langmuir equation can be linearized by taking the reciprocal of the
equation as shown in equation 7 & 8:
Log (x/m) = (1/n) Log C +LogK
(6)
32
Laboratory Handout
PHT 224
Langmuir isotherm
In the contrary of frendlich isotherm ; langmuir is based on a theoretical
consideration of the process of adsorption. These consideration are:
1. A maximum of monolayer will be adsorbed .
2. The adsorption surface is homogeneous with each site having the same affinity for
adsorption .
3. There are a finite number of site to which molecules can be absorbe .
4. There is a competition between solvent and solute molecules for the adsorption site.
5. Adsorption is a function of the number of adsorption site available and therefore
the rate of adsorption (or the occupation of these sites) will decrease with time.
Cm/x = C/k- + ( 1/k-.k )
Adsorption Of Oxalic Acid On Charcoal
In this experiment oxalic acid will be used as the adsorbate and charcoal will be used as
the adsorbent .
Procedure:
1. In each 5 stoppard reagent bottles, place 5 g of finely divided charcoal.
2. Add 50 mL of standard oxalic acid solution to each of the 5 bottles, changing the
concentration from 0.1, 0.2, 0.4, 0.6, 0.8 and 1 N respectively.
3. Shake the bottles 15 minutes and set aside to achieve equilibrium.
4. Filter the contents of each bottle separately through a small filter paper and reject
the first 10 mL of each filtrate (to minimize the loss due to adsorption by the filter
paper).
5. Titrate accurately measured portions (20 mL) of each filtrate with standard N/2
sodium hydroxide solution.
6. Calculate the amount adsorbed in each case and list your result in Table .
Results:
1. Plot the relationship between log X/m and log C to verify Freundlich
adsorption isotherm.
2. To verify Langmuir adsorption isotherm, plot a curve relating Cm/X and C.
33
Laboratory Handout
PHT 224
Table:
Oxalic
acid
Initial
conc.
(Ci)
1N
2.25
0.8N
1.8
0.6N
1.35
0.4N
0.9
0.2N
0.45
0.1N
0.225
End
point of
N/2
NaOH
Free
oxalic
acid (C0)
Amount
adsorbed
34
X/m g
oxalic
acid
adsorbed
Cm/X
Log
(Ci)
Log
X/m
Laboratory Handout
PHT 224
Lab No: 10
Determination of critical micelle concentration (CMC) of a surface active agent by
surface tension method
Surface active agent: is a molecule or ion that has certain affinity for both polar and nonpolar solvent. Therefore they arrange themselves at the interface and lower the surface
tension.
Surface active agent = surfactant = amphiphile
Surfactant when present in a liquid medium at a low concentration, they exist separately
and are of such a size to be sub-colloidal and as the concentration increase aggregate
occurs over a narrow range of concentration. These aggregate called micelles.
Critical micelle concentration (CMC): is the concentration at which the micelle formed.
Also, it is the concentration of the surfactant above which it will migrate to the bulk and
start to form micelle and show the minimum value of surface tension.
Procedure:
1. Select 6 clean test tubes and wash it with distilled water.
2. Put in each test tube different concentration of SAS (0 – 0.5%)
And you be provided with a stock solution 1%
Concentration of SAS (0%, 0.005%, 0.01%, 0.05%, 0.2%, 0.3%, 0.5%), and the
volume in each test tube should be 10 ml.
3. To prepare the test tube:
1) 0% SAS = 10 ml distilled water.
2) 0.005% SAS
C*V= C1* V1
0.005 * 10 = 1 * V1
V1 = 0.05 ml SAS and 9.95 ml water
4. After preparing the test tubes (start from the lower concentration), mix well and
count the number of drops of 0.5 ml of the mixture.
5. Plot surface tension VS SAS concentration and determine the CMC.
35
Laboratory Handout
Test
tube
PHT 224
SAS
SAS ml Distilled # of drops in
concentration
water ml
0.5 ml
1
0%
0
10ml
2
0.005%
0.05ml
9.95ml
3
0.01%
0.1ml
9.9ml
4
0.05%
0.5ml
9.5ml
5
0.2%
2ml
8ml
6
0.3%
3ml
7ml
7
0.5%
5ml
5ml
36
Laboratory Handout
PHT 224
Lab No: 10
Effect of temperature on the rate of hydrolysis of aspirin
In this experiment the students will be divided into six groups.
Each two groups will determine the rat constant and the half - life
(of the alkaline hydrolysis of aspirin) at different temperature
.
°
Therefore two groups will study the aspirin hydrolysis at 50 C others
at 60°C and the last two groups at 70 °C.
The dimension of a first-order rate constant is time-'; and the usual
units are sec-1 .
Procedure:
1- In a dry stoppered measuring (volumetric) flask, place 50 ml
5%sodium citrate solution (by burette).
2- Place the flask in a constant temperature water bath adjusted at 50°C,
60°C and 70°C.
3- When sodium citrate solution reaches the assigned temperature,
checked by thermometer, dissolve 1 g of aspirin accurately weighed.
4- After complete dissolution of aspirin (by chaking), Withdraw 5ml from
the flask (by pipette) at 0, 10, 20, 30, 45, 60 minutes from the beginning
of the experiment.
5- The samples are added to 30 ml distilled water and titrated against
N/10 NaOH using phenol phthaline indicator (4 drops).
6. Plot log C t % against t, and calculate k value at the assigned
temperature.
7- Comment on your result.
Calculation:
Since aspirin hydrolysis follows first order rate kinetics:
Log Ct = log C 0 – (kt/2.303)
Aspirin remaining at any time t (C t) = 2x-y
37
Laboratory Handout
PHT 224
% aspirin remaining (C t%) = (2x-y/x)*100
Where x is the E.p t time = 0
Y is the E.p at time = t
Results
Time interval
(t) (min)
End point
(ml)
Ct
0
10
20
30
45
60
38
Ct %
log Ct %
Laboratory Handout
PHT 224
Lab No: 11
Isotonic Solutions
 Definitions.
 Isotonic Solution: is a solution having the same osmotic
pressure as a body fluid. Ophthalmic, nasal, and parenteral
solutions should be isotonic.
 Hypotonic solution: is a solution of lower osmotic pressure
than that of a body fluid. These solutions lead to swelling
and bursting of RBCs, which in turn leads to hymolysis.
 Hypertonic solution: is a solution having a higher osmotic
pressure than that of a body fluid. These solutions lead to
shrinkage of the RBCs.
Isotonic solutions Calculations:
I.
Procedure for Calculation of Isotonic Solutions Using Sodium
Chloride Equivalents:
a. Calculate amount in grams of NaCl represented by the ingredients
in prescription. Multiply the amount in grams of each substance
by its NaCl equivalent “either from tables or by calculation”.
b. Calculate amount in grams of NaCl, alone, that would be contained
in an isotonic solution of the total volume specified in prescription.
i.e. 0.9  100 because 0.9% solution of NaCl is isotonic.
X  total of the prescription.
c. Subtract the amount of NaCl represented by the ingredients in the
prescription (step#1) from the amount of NaCl needed to prepare
isotonic solution (step#2) i.e. step # 2 – step # 1.
d. If an agent other than sodium chloride such as boric acid, dextrose,
sodium or potassium nitrate is to be used to make a solution
isotonic, divide the amount of NaCl (step 3) by NaCl equivalent of
the substance used to adjust Isotonicity i.e.
39
NaCl from step # 3
.
E  value
Laboratory Handout
II.
PHT 224
II. Calculation of Sodium Chloride equivalent of a substance (if it
is not tabulated):
Sodium Chloride equivalent =
M.Wt of NaCl
i factor of substance
*
i factor of NaCl
M.Wt of substance
Problems on calculating the dissociation factor (i) of an electrolyte:
1. Zinc Sulfate ZnSO4 is a 2-ion electrolyte, dissociation 40% in a certain
concentration. Calculate its dissociation factor.
2. Zinc Chloride (ZnCl2) is a 3-ion electrolyte; dissociation 80% in a certain
concentration, calculate (i).
In general, we may use the following tabulated values in case of solutions of 80% or
higher concentrations:
(i)
Nonelectrolytes, slightly dissociated subs.
1
Substances that dissociate into two ions
1.8
Substances that dissociate into three ions
2.6
Substances that dissociate into four ions
3.4
Substances that dissociate into five ions
4.2
Problem on calculating the E-value of a substance:
Papavarine HCl (mwt = 376) is a 2-ion electrolyte dissociating 80%. Calculate its
E-value (Sodium Chloride equivalent), where its dissociation factor (i) = 1.8
Problems on isotonic solutions calculations using the NaCl E-value:
1. How many grams of NaCl should be used in compounding the following
prescription:
Pilocarpine nitrate
0.3 g
E =0.23
Sod. Chloride
Q.S.
Purified water ad
30 ml
Make isotonic solution.
40
Laboratory Handout
PHT 224
Example:
How many grams of boric acid should be used in compounding the following:
1. Phenacaine HCl
1%
E (0.2)
Chlorobutanol
0.5% E (0.24)
Boric acid
Q.S. E (0.52)
Purified water ad
60 ml
Make isotonic solution
2. Oxytetracyline HCl
0.5%
E = 0.12
Tetracaine HCl 2% solution 15 ml
Sodium Chloride
Q.S.
Purified water ad
30 ml
Make isotonic solution
2% solution of Tetracaine HCl is isotonic. How many mls of 0.9% solution of
Sodium Chloride should be used?
3. Tetracaine HCl
0.5%
E(0.18)
Epinephrine bitartarate 1:1000 solution
10 ml
Boric acid
Q.S
E(0.52)
Purified water
ad
30
Make isotonic solution
The solution of Epinephrine bitartarate (1:1000) is already isotonic. How many
grams of boric acid should be used in compounding the prescription?
II. Isotonic Solutions Calculations using Freezing Point Data:
The calculations involved in preparing isotonic solutions may be made in terms of data
relating to the colligative properties “freezing point depression, osmotic pressure,
elevation of boiling point” of solutions. A comparison of freezing points for example
may be used for this purpose.
1-How many mg each of NaCl and dibucaine HCl are required to prepare 30 ml of a 1%
solution of dibucaine HCl isotonic with tears?
From tables:
1% NaCl
Tf = 0.58
1% Dibucaine HCl
Tf = 0.08
Freezing point of blood and lachrymal fluid is – 0.52 oC.
41
Laboratory Handout
PHT 224
2- How many grams of NaCl should be used in compounding the following prescription:
Rx
Naphazoline HCl
1%
NaCl
Q.S.
Purified water
ad
30ml
Make isotonic solution. Use the freezing point depression method.
Tf blood = 0.52
Tf 1% NaCl = 0.58
Tf 1% Naphazoline HCl = 0.16
III. Isotonic Solutions Calculations using White-Vincent Method:
Computing tonicity involves the addition of water to a specified amount of drug to make
isotonic solution, followed by the addition of an isotonic buffered diluting vehicle to
bring the solution to the final volume:
V = W * E * 111.1
Where:
W = grams of drug.
E = sodium chloride equivalent (tabulated).
V = volume in ml of isotonic solution that may be prepared by mixing drug with
water.
Make the following solution isotonic with respect to membrane. Provided that you have
isotonic diluting solution:
Phenacaine HCl
0.06 g (E 0.2)
Boric acid
0.3 g (E 0.52)
Sterilized water
to
100 ml
42