DEPARTMENT OF PHARMACY

UNIVERSITY OF MALTA

Name: Group:

Pharmaceutics IV

PHR4308

Practicals Handbook

Practical 1: Effect of concentration on viscosity

Practical 2: Buffering Pharmaceutical Preparations

Practical 3: Industrial Practice 1: Weighing and Dispensing Techniques

Dimensions and Friability Testing

Practical 4: Industrial Practice 2: Particle Size Distribution

Pharmaceutics Co-ordinator: Dr. Maurice Zarb Adami

Compiled by Marie Clare Zammit

December 2009

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Practical 1

Effect of Concentration on Viscosity

Name: Group: Date:

AIM: To determine the effect of concentration on viscosity.

APPARATUS

• Beaker 250ml

• Bunsen Burner

• Electronic Balance

• Measuring Cylinder 1 x 100 ml

• Pipette 50ml

• Pipette filler

• Pipette with long spout

• Rubber tubing

• Stop watch

• Thermometer 0 -100°C

• U-Tube viscometer size C

• Volumetric flask 200ml x 2

• Water bath maintained at 37°C

MATERIALS

• Distilled water

• Sucrose

WARNING: The viscometer is a very fragile instrument. Handle with utmost of care.

METHOD

1. Prepare 200ml of Syrup BP by heating 667g of sucrose in water until it dissolves

and make up to 1000ml with hot water.

2. Fill the viscometer through arm L using the pipette with the long spout up to a

level a few mm above mark G while trying not to wet the sides.

3. Clamp the viscometer by arm N in the water bath ensuring that marks E and F

are visible and wait until the viscometer warms up.

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4. Bring the meniscus to level G by removing the excess fluid using the pipette with

the long spout.

5. Fit the rubber tubing to arm L and blow to push the level of the syrup a few mm

above mark E.

6. Stop blowing and measure the time for the fluid to fall from mark E to mark F.

7. Repeat steps 5 and 6 one more time.

8. Pipette 100 ml of the solution prepared in step 1, into a 200ml volumetric flask

and make up with water to 200ml while mixing.

9. Empty the viscometer and rinse it with a few mls of the solution prepared in step

8.

10. Repeat steps 2 to 7 but using the solution prepared in step 8.

11. Pipette 100ml of the solution prepared in step 8 into a 200ml volumetric flask

and make up to the mark with water while mixing.

12. Empty the viscometer and rinse it with a few ml of the solution prepared in step

11

13. Repeat steps 2 to 7 but using the solution prepared in step 11.

14. Pipette 100ml of the solution prepared in step 11 into a 200ml volumetric flask

and make up to the mark with water while mixing.

15. Empty the viscometer and rinse it with a few ml of the solution prepared in step

14.

16. Repeat steps 2 to 7 using the solution prepared in step 14.

17. Empty the viscometer and rinse it with water.

18. Repeat steps 2 to 7 but now using water.

RESULTS

Table 1: Time taken for fluid to fall from mark E to F

Time taken for fluid to fall from mark E to F (s) Solution T1(s) T2(s)

1 2 3 4 5

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CALCULATIONS

1. Determine the kinematic viscosity v for each solution using the following formula:

v=kt

Where: v = kinematic viscosity in (mm2s-1)

k = viscometer constant = 0.03mm2s-2

t = time in seconds

Table 2: Average kinematic viscosity

2. Calculate the sugar concentration for each solution

Table 3: Concentrations of each solution

3. Using the following formula check if the graph fits a straight line

R = Σ(x – x1) (y – y1)

√Σ(x – x1)2(y – y1) 2

Where: x1 = mean value for x y1 = mean value for y

Kinematic Viscosity Solution v1 (mm2s-1) v2 (mm2s-1) vav (mm2s-1)

1 2 3 4 5

Solution Concentration g/ml 1 2 3 4 5

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Table 4: Calculation for regression analysis

x (x – x1) (x – x1)2 y (y – y1) (y – y1) 2 (x – x1)2(y – y1)2

1

2

3

4

5

Summation Σ Σ Σ

R =

4. What do you conclude?

______________________________________________________________________

5. Plot a graph of kinematic viscosity against sugar concentration.

Table 5: Values for graph: kinematic viscosity vs sugar conc.

Sugar conc. (g/ml) Kinematic viscosity g/ml

1 2 3 4 5

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QUESTIONS

1. List 3 precautions.

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

2. List 1 source of error

______________________________________________________________________

3. Discuss the data obtained.

________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ ______________________________________________________________________

4. What is viscosity?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

5. Define kinematic viscosity?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

6. Give 5 examples of viscosity modifiers used to modify suspension viscosity.

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

7. Give an example where the viscosity of a formulation is important in the

administration of a drug.

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

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8. What happens to the viscosity of the following system on increasing the

temperature?

a) Gas _________________________________________________________

b) Liquid _______________________________________________________

9. List three parameters that are constant in this experiment.

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

10. Why are viscosity-increasing agents important in ophthalmic preparations? Give 2

examples of such agents

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

11. What are the maximum viscosity (in centipoises) that can be used in eye

preparations? What happens if this value is exceeded?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

12. What is the importance of viscosity in relationship to the bioavailability of drugs?

Explain giving 4 examples.

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

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13. Should the temperature be constant when measuring viscosity? Explain

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

14. How is the viscometer constant (k) for an Oswald-type viscometer determined?

Explain briefly.

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

Demonstrator Name Signature

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Practical 2

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. Accurately weight about 2.01g of citric acid.

ii. Dissolve in 50ml water using the magnetic stirrer.

iii. Place the pH meter electrode in the solution making sure that the stirrer does not hit the

electrode bulb (lower end of electrode)

iv. When the pH is steady take the reading.

v. Keeping the electrode in the citric acid solution and the solution stirred, add 1ml of 0.5M

sodium hydroxide solution from a burette making sure that the sodium hydroxide goes

directly in the solution.

vi. When the pH is steady, take the reading.

vii. Keep repeating step 5 and 6 until the pH is above 12.

viii. Accurately weight about 0.155g of boric acid and repeat steps 2 to 7 using 0.1M sodium

hydroxide. Continue until the pH is above 11.

ix. Take 50ml of the phosphoric acid provided in a beaker and place on the magnetic stirrer.

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x. Place the pH meter electrode in the solution making sure that the stirrer does not hit the

electrode bulb.

xi. When the pH is steady take the reading.

xii. 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.

xiii. When the pH is steady take the reading.

xiv. Keep repeating steps 12 and 13 until the pH is above 11.

xv. Accurately weight about 0.354g of potassium hydrogen phosphate.

xvi. Dissolve in 50ml water using the magnetic stirrer.

xvii. Place the pH meter electrode in the solution making sure that the stirrer does not hit the

electrode bulb.

xviii. When the pH is steady take the reading.

xix. 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.

xx. When the pH is steady, take the reading.

xxi. Keeping repeating steps 19 and 20 until the ph is above 11.5.

QUESTIONS 1. What is the molarity of each of the solutions used? Calculations

Solution Molarity

Boric acid Citric acid Phosphoric acid 2g/100ml Potassium Dihydrogen Phosphate

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 is meant by buffering capacity and how could the graphs obtained in 2 be related to it?

_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ 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? _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ 5. Discuss the use of buffers in the pharmaceutical industry. _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

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REFERENCES 1. Billany MR Solutions. In Aulton ME, ed. Pharmaceutics, The science of dosage form

design, New York: Churchill Livingstone, 1988: 262. 2. British Pharmacopeia. London: Her Majestys Stationary Office, Volume 2 1993: 746-7.

3. Food JL. Parenteral Products. In: Aulton ME, ed. Pharmaceutics, The science of

dosage form design, New York: Churchill Livingstone, 1988: 368-369.

4. Harvey SC. Blood, fluids, electrolytes and haematological drugs. In Gennaro AR, ed. Remington’s Pharmaceutical Science. 18th ed. Pennsylvania: Mack Publishing Company, 1990: 817-26

5. Martin A. Physical Pharmacy. 4th ed. Philadelphia: Lea and Febiger, 1993: 171-80.

6. Mullins JD, Hecht G. Ophthalmic preparations. In Gennaro AR, ed. Remington’s

Pharmaceutical Science. 18th ed. Pennsylvania: Mack Publishing Company, 1990: 1589.

7. Niebergall PJ. Ionic solutions and electrolyte equilibria. In: Gennaro AR, ed. Remington’s Pharmaceutical Sciences. 18th ed. Pennsylvania: Mack Publishing Company, 1990: 241-243, 246.

8. Richards JH. Solutions and their properties. In: Aulton ME, ed. Pharmaceutics, The

science of dosage form design, New York: Churchill Livingstone, 1988: 45.

Demonstrator Name Signature

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Practical 3

Industrial Practice 1a: Weighing and Dispensing Techniques

Name: Group: Date:

Dispensing in a manufacturing plant is performed in accordance to Good Manufacturing Practice (GMP). The persons performing the operation will follow a written approved procedure and a number of checks are normally performed before, during and after the actual weighing of raw materials.

i. Check the status of the dispensing area. Record your findings below, deleting as appropriate.

The dispensing area is clean / not clean. Sign ____________ Date ____________

ii. In industry, you would be performing such an activity under a laminar or cross-flow hood fitted with filters. In this case, you would normally be required to check that the resistance to flow through the hood is within limit.

A high reading would indicate that: ______________________________________________________________________

What action would you take?

______________________________________________________________________

A low reading would indicate that:

______________________________________________________________________

What action would you take?

______________________________________________________________________

iii. Record the operation being performed on the area log:

Room / Area: _____________________________

Activity: ______________________________________________________________________

Performed by: _______________________________ (sign/date)

Supervised by: _______________________________ (sign/date)

iv. Confirm that the balances being used are calibrated. Perform a check with the provided known weight.

Record the weight(s) used: _____________

Record the actual reading(s) on the scale(s): _________________

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For the purpose of this exercise, you are allowed a tolerance of +/- 1%. Can the balance(s) be used within the allowed parameters?

Yes / No _______________________________ (sign/date)

v. Log your activities on this abstract of the equipment log(s).

Balance Asset No.: _______________________

Date Activity Check Weight

Reading (if applicable)

Signature

Balance Asset No.: _______________________

Date Activity Check Weight

Reading (if applicable)

Signature

vi. Before weighing a material, you must perform a number of checks that are included in your Standard Operating Procedure (SOP). These will generally include checks to:

� Ensure that the correct material is being weighed (item number and description on identification label)

� Ensure that the material has been approved by Quality Control (status label)

� Ensure that the status granted by Quality Control has not expired (retest date)

vii. Select the correct balance for the weight being dispensed. This should fall within the range of the balance being used. Remember to allow for the tare weight of containers.

viii. Tare the container you are weighing in.

ix. Weigh, label the material weighed and reseal the bulk container. Document your activity below. Attach below a copy of the labels you have used to identify the materials dispensed.

Item No. Material Description Batch

No.

Dispensed by

(sign/date)

Checked by

(sign/date)

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Questions 1. Briefly explain the difference between an expiry date and a retest date. _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

2. With reference to EU-GMP, state why two signatures were required in various instances

of this operation. _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

3. Briefly explain what a Batch Manufacturing Record (BMR) is. _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

4. What is the significance of an item number and of a batch number? What is the

difference between them? _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ 5. A pharmaceutical manufacturing company uses lactose monohydrate in ten of its solid

dose formulations which were manufactured using wet granulation techniques. A new direct blend product is being developed by its R&D department which again requires lactose monohydrate. However, the lactose monohydrate to be used in this formulation is of a different specification. Briefly describe the systems that assure the correct grade will be used in the respective products in manufacture. Will testing the incoming material to the pharmacopoeial monograph alone provide sufficient reassurance that the new material meets the specifications set by the R&D Department? If not, what other tests will be required?

_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

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Industrial Practice 1b: Dimensions and Friability Testing Using a micrometer screw gauge, record the diameter and thickness of 6 tablets.

Tablet Diameter Thickness 1 2 3 4 5 6

i. Compare the results obtained with the limits for the sample, which have been displayed by the demonstrator on the white board. Does the sample meet the requirements with respect to dimensions?

Calculations _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

ii. Can you get variation in diameter during the production of a batch of tablets? Can you get variation in thickness during the production of a batch of tablets? Briefly explain your answers.

a. One of the tests used to measure the strength of a tablet is friability. This test is of particular importance for tablets which tend to cap on attrition.

iii. Examine the tablets you have been provided with. If they are dusty, place them on a coarse sieve and dust them lightly with a soft brush.

iv. Accurately weigh an amount of tablets which is as close as possible to 6.5g. Record this weight as W1.

W1 ___________________________

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v. Place the tablets in one section of the friabilator.

vi. Switch on the friabilator and rotate 100 times.

vii. Carefully transfer the tablets to a coarse sieve and dust lightly with a soft brush. Weigh the tablets and record this weight as W2.

W2 ___________________________

viii. Calculate the friability as follows:

a. Friability = (W1 – W2) x 100 % W1

Calculations

ix. Compare the results obtained with the limits for the sample, which have been displayed by the demonstrator on the white board (≤1.0%). Does the sample meet the requirements with respect to friability?

_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

x. What problems do you envisage if the tablets have a high friability? _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

Demonstrator Name Signature

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Practical 4

Industrial Practice 2: 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 this curve, the powder is separated into fractions depending on particle size. The method most often used for this is by 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 a 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 you will be using to the nearest 0.1g.

ii. Set up the nest of sieves on the mechanical shaker so that 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. Your report must include the total sieving time, the methodology used (Dry Sieving Method) and the set values for all variable parameters.

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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?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

3. What problems can be encountered if the particle size is finer than this?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

4. Which standard describes how to calibrate test sieves?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

5. What would you use to check the effective opening of test sieves?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

6. What is the commonest difficulty encountered when testing particle size by this method? How can this problem be overcome?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

7. What settings can be varied in this test?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

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8. Apart from mechanical and electro-magnetic shaking, what other method of oscillation can be used?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

9. How should sieves be cleaned?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

10. If electrostatic charge is affecting your analysis, what corrective action should you take?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

11. An R&D facility has obtained a very limited amount of an API which is very scarcely available. The particle size of this material needs to be assessed. Would you use 200mm diameter sieves or 76mm diameter sieves in this case?

______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________

Demonstrator Name Signature