DEPARTMENT OF PHARMACY
UNIVERSITY OF MALTA
Pharmaceutics IV
PHR4308
Practicals Handbook
Practical 1: Buffering Pharmaceutical Preparations
Practical 2: Extemporaneous Preparations
Practical 3: Particle Size Distribution
Pharmaceutics Co-ordinator: Prof Anthony Serracino-Inglott
Compiled by Marie Clare Zammit
Updated by Nicolette Bartolo
January 2012
PHR 4308
Practical 1
BUFFERING PHARMACEUTICAL PREPARATIONS
Name:
Group:
Date:
AIM
Investigation of the buffering capacity of systems of interest to the pharmaceutical industry
APPARATUS
Beakers 4 x 100ml
Burette 1 x 50ml
Electronic balance
Magnetic stirrer
Measuring cylinder 1 x 50ml
pH meter
MATERIALS
Boric acid
Citric acid
Phosphoric acid 2g/100ml
Potassium Dihydrogen Phosphate
Sodium Hydroxide 0.1M
Sodium Hydroxide 0.5M
WARNING: The pH meter electrode is very fragile. Handle with care. Always rinse well with
water after using it. Leave in fresh distilled water when ready.
METHOD
i.
Fill two burettes, one with the 0.1M and the other with the 0.5M sodium hydroxide
solution.
ii.
Accurately weight about 0.155g of boric acid.
iii.
Dissolve the boric acid in 50ml water using a magnetic stirrer.
iv.
Place the pH meter electrode in the solution making sure that the stirrer does not hit the
electrode bulb (lower end of electrode).
v.
When the pH is steady take the reading.
vi.
Add 1ml of 0.1M sodium hydroxide solution, from the burette, to the boric acid solution
while stirring and keeping the pH meter electrode in the solution. When adding the
sodium hydroxide solution, make sure that it goes directly into the solution.
vii.
Take the reading of the pH when it is steady.
viii.
Keep repeating step v and vi until the pH is above 11.
ix.
Accurately weight about 2.01g of citric acid and repeat steps ii to vii using 0.5M sodium
hydroxide. Continue until the pH is above 12.
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x.
Place 50ml of phosphoric acid in a beaker and use a magnetic stirrer to mix the
solution.
xi.
Place the pH meter electrode in the solution making sure that the stirrer does not hit the
electrode bulb.
xii.
When the pH is steady take the reading.
xiii.
Keeping the electrode in the solution and the solution stirred, add 1.0ml of 0.5M sodium
hydroxide solution from a burette making sure that the sodium hydroxide goes directly in
the solution.
xiv.
When the pH is steady take the reading.
xv.
Keep repeating steps xii and xiii until the pH is above 11.
xvi.
Accurately weight about 0.354g of potassium dihydrogen phosphate.
xvii.
Dissolve in 50ml water using the magnetic stirrer.
xviii.
Place the pH meter electrode in the solution making sure that the stirrer does not hit the
electrode bulb.
xix.
When the pH is steady take the reading.
xx.
Keeping the electrode in the solution and the solution stirred, add 1.0ml of 0.1M sodium
hydroxide solution from a burette making sure that the sodium hydroxide goes directly in
the solution.
xxi.
When the pH is steady, take the reading.
xxii.
Keeping repeating steps xix and xx until the pH is above 11.5.
QUESTIONS
1. Calculate the molarity of each of the solutions used.
Calculations
Solution
Molarity
Boric acid
Citric acid
Phosphoric acid 2g/100ml
Potassium Dihydrogen Phosphate
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2. Plot a graph of pH against volume of sodium hydroxide added for each solution.
Comment on the graphs obtained.
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3. What inferences can be made from the graphs obtained in 2?
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4. Using a mixture of the buffers studied, how would it be possible to have a buffer capable
of buffering between pH 2 and pH 9?
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REFERENCES
1. Aulton ME, ed. Pharmaceutics: The science of dosage form design. 2nd ed. New York:
Churchill Livingstone; 2002.
2. European Pharmacopoeia. 7th ed. Germany: Druckerei CH Beck, Volume1 2010:746-7.
3. Remington: The science and practice of pharmacy. 21st ed. UK: Pharmaceutical press;
2011.
4. Sinko PJ. Martin’s physical pharmacy and pharmaceutical sciences. 6th ed. US:
Lippincott Williams & Wilkins; 2011.
Demonstrator Name
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Signature
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Practical 2
EXTEMPORANEOUS PREPARATIONS
Name:
Group:
Date:
AIM
To make an extemporaneous preparation of an ointment and suspension
APPARATUS
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Electronic balance
Glass plate
Wooden spatula
Plastic container
Mortar and pestle
Glass funnel
Glass bottle
Labels
Gloves
MATERIALS
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Petroleum jelly
Salicylic acid
Tablet X 100mg
Sodium benzoate
METHOD
Ointment preparation
i.
Calculate the amount of petroleum jelly and salicylic acid required to produce 10g of
ointment containing 1% salicylic acid.
ii.
Clean and dry well the glass plate.
iii.
Place the glass plate on the balance and press Tare.
iv.
Weigh accurately the amount of petroleum jelly required, as calculated.
v.
Remove the glass plate from the balance and put the plastic container instead and
press tare.
vi.
Weigh accurately the amount of salicylic acid required, as calculated.
vii.
Put the salicylic acid on the ointment and mix them by moving the spatula in the figure
of 8 repeatedly.
viii.
Collect the prepared ointment using the wooden spatula and place it in the plastic
container used to weigh the salicylic acid.
ix.
Mix the ointment again in the plastic container to ensure that any traces of salicylic
acid powder previously left in the container are amalgamated well into the ointment.
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x.
Label the ointment produced.
xi.
Repeat steps ii to ix to prepare 10g of ointment containing petroleum jelly and salicylic
acid at a ratio of 11:0.25 respectively.
Calculations:
Amount of salicylic acid required for preparation 1: ________g
Amount of salicylic acid required for preparation 2: ________g
Suspension preparation
A patient came to the pharmacy with the following prescription:
Joe Borg
Borg Street
Msida
Age: 50
Rx
1/1/2012
Compound a 10mg/ml of suspension X
pt to take 50mg bd x5 days
Dr Borg Reg No 0000
Clinic Street
Msida
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
x.
Provided that the dosage strength of the tablets available containing substance X is
100mg, calculate the amount of tablets X and volume of water required to produce a
10mg/ml suspension.
Calculate the weight of sodium benzoate required (0.1% w/v) for the suspension, to act
as a preservative.
Mix the sodium benzoate with the calculated volume of water (referred to as vehicle).
Pulverise the tablets using a mortar and pestle.
Add one third of the vehicle to the pulverised tablets and triturate the powder until a
uniform suspension is achieved.
Transfer the suspension produced into the glass bottle using a funnel.
Use one third of the vehicle to rinse the mortar and pestle by a triturating motion and
transfer the vehicle to the bottle.
Use the remaining volume of vehicle to rinse the funnel.
Shake the produced suspension well.
Label the bottle containing the produced suspension.
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Calculations:
Quantity of tablets X required: ________
Volume of suspension required: ________ml
Weight of sodium benzoate required: ________g
Questions
1. What information should be included on the label of extemporaneous preparations?
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2. What is the shelf-life of the extemporaneous preparations produced?
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3. Why is the ointment slab used made of glass?
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4. What volume of suspension X should be taken daily?
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5. What type of tablets should not be used for the preparation of suspension? Why?
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6. Describe the ideal containers for the storage of extemporaneous ointments and syrups.
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REFERENCES
1.
Roche®. Tamiflu® (oseltamivir) – Product information. [Online]. [cited 2012 Feb 1].
Available from: URL: http://www.roche-australia.com/fmfiles/re7229005/downloads/antivirals/tamiflu-pi.pdf
Demonstrator Name
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Signature
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Practical 3
Particle Size Distribution
Name:
Group:
Date:
Powders generally consist of particles with irregular shapes and non-uniform sizes. This
means that size distributions are often complex. Particle size is therefore described by
determining the number of particles in successive size ranges. The distribution is often
represented by a histogram in which the width of the bar represents the size range and the
height represents the frequency of occurrence in each range. A smooth curve can then be
drawn through the midpoints of the tops of the bars. A particle size distribution curve is
obtained in this way.
In order to obtain a distribution curve, the powder is separated into fractions depending on
particle size. The most frequently used method to separate powders is sieving. Basically,
this technique consists of placing a nest of sieves of different aperture on top of one another
with the finest aperture sieve being placed at the bottom and subsequent sieves being
placed in ascending degrees of coarseness. The sieves are then shaken mechanically or
electromagnetically. The sieve motion applied can be oriented horizontally which tends to
loosen the packing of the particles in contact with the sieve surface, or vertically which tends
to agitate and mix the particles.
Method
i.
Accurately weigh each sieve to be used, to the nearest 0.1g.
ii.
Set up the nest of sieves on the mechanical shaker in an ascending order i.e. the
finest sieve is at the bottom and the coarsest sieve is on top.
iii.
Accurately weigh out approximately 25g, 50g and 100g of the powder.
iv.
Place the first sample carefully on the topmost sieve and close the cover.
v.
Shake the powder through the sieves at 50% amplitude for 5 minutes. Then clean
the sieves and repeat for each sample size so as to determine what sample size
should be used.
vi.
Accurately weigh the approximate sample size to be tested. Clean and accurately
weigh once again each sieve.
vii.
Place the sample on the top most sieve, close the lid and vibrate at 50% amplitude
until the end-point is reached. This is achieved when the weight held on each one of
the sieves does not change by more than 5% or 0.1g (or 20% if the weight on that
particular sieve is less than 5% of the test sample size).
viii.
If any sieve is found to hold more than 50% of the test sample, then the test is to be
repeated with the inclusion of an additional sieve of intermediate coarseness
between this sieve and the next coarser one. You should repeat the test if more
than 5% of your sample is lost.
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ix.
Your report must include the total sieving time, the methodology used (Dry Sieving
Method) and the set values for all variable parameters.
Questions
1. Draw a histogram of your particle size distribution and a particle size distribution
curve. Comment on the shape of this curve.
Comment on the shape of this curve.
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2. What is the finest particle size you would normally use this method for?
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3. What problems can be encountered if the particle size is finer than this?
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4. What is the commonest difficulty encountered when testing particle size by this
method? How can this problem be overcome?
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5. What settings can be varied in this test?
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6. How should sieves be cleaned?
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7. If electrostatic charge is affecting your analysis, what corrective action should you
take?
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Demonstrator Name
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Signature
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