Author: Lillian Yeo

UNIVERSITI KEBANGSAAN MALAYSIA

 

LABORATORY REPORT

DEVELOPMENT OF PHARMACEUTICAL PRODUCT I

(NFNF 2213)

 

TITLE                        : CHARACTERISATION OF EMULSION FORMULATIONS

GROUP                     : 2

NAME                       : MUHAMMAD RASYDAN BIN BUCHEK    A168185

                                  FARINA ZAHIDAH BINTI ABD AZIZ         A168417

                                  NUR AQILAH BINTI ABDUL KADIR         A169046

                                  LILLIAN YEO FANG FANG                       A167802

 

LECTURER’S NAME : PROF. MADYA DR. NG SHIOW FERN

 

SEMESTER I, SESSION 2019-2020

FACULTY OF PHARMACY

 

TITLE

Characterisation of emulsion formulations  

 

DATE

7th October 2019              

 

OBJECTIVE  

To determine:

1. The effects of HLB of surfactant on the stability of the emulsion.

2. The effects of different oil phases used in the formulation on the physical characteristics and stability of the emulsion.  

 

INTRODUCTION      

     An emulsion is a mixture of two or more liquids that are normally immiscible where one liquid contains a dispersion of the other liquids. Emulsion has two phases where one of them is internal or dispersed phase, which dispersed homogeneously in another liquid called external or continuous phase. In other words, an emulsion is a special type of mixture made by combining two liquids that normally don’t mix. Emulsions are part of a more general class of two-phase systems of matter called colloids. Emulsions usually appear cloudy or white because light is scattered off the phase interphases between the components in the mixture.        

     There are two types of emulsion, known as oil in water (o/w) and water in oil (w/o) emulsions. The type of emulsion depends on the properties of the dispersed phase and continuous phase. If the oil phase is dispersed in a continuous aqueous phase, it is known as oil in water emulsion. If the aqueous phase is the dispersed phase and the oil phase is the continuous phase, it is known as water in oil emulsion. Meanwhile, the boundary between the phases is called the interface.        

     Most emulsions are unstable, with components that won’t mix on their own or remain suspended indefinitely. Therefore, emulsifiers need to be added into emulsion formulation. This is because emulsifiers have the unique ability to attract water (hydrophilic) and oil (lipophilic), forming a film over one phase in a mixture to form globules that repel each other. Thus, this allow the molecules to coat the dispersed phase and keep it uniformly suspended in the continuous phase. When added to an o/w emulsion, emulsifiers will surround the oil droplet with non-polar tails extending into the oil, and polar head groups facing the water. For w/o emulsion, non-polar tails extend outward into the oil phase, while polar head groups point into the water droplet. In this way, emulsifiers lower the interfacial tension between the oil and water phases, stabilizing the droplets and preventing them from coalescing. Different emulsifiers have different Hydrophilic–Lipophilic Balance, HLB values which enable to predict the ability to stabilize various kinds of emulsion. HLB is the balance of the size and strength of the hydrophilic and lipophilic moieties of a surfactant molecule. The HLB scale ranges from 0 to 20. Emulsifiers with HLB values greater than 10 are more hydrophilic and thus better at stabilizing o/w emulsions. In contrast, emulsifiers with HLB values less than 10 are more hydrophobic and therefore better suited for w/o emulsions.  

 

HLB   value   =	(quantity surfactant 1)(HLB surfactant 1) + (quantity surfactant 2)(HLB surfactant 2)
	Quantity surfactant 1 + quantity  surfactant 2

 

APPARATUS AND MATERIALS

Apparatus

8 Test tubes                                                                        1 set of 5ml pipette and bulb

A 50ml measuring cylinder                                           1 50ml beaker

2 sets of pasture pipettes and droppers                 1 15ml centrifugation tube

Vortex mixer                                                                       Centrifugation apparatus

Weighing boat                                                                    Viscometer

1 set of mortar and pestle                                              Water bath (45°C)

Light microscope                                                              Refrigerator (4°C)

Microscope slides     

 

Materials

Palm oil                                                                                  Span 20

Arachis oil                                                                             Tween 80

Olive oil                                                                                  Sudan III solution (0.5%)

Mineral oil                                                                   

Distilled water

 

PROCEDURE

1. Each of the test tubes were labelled and 1cm line were marked on each test tube. 2. 4ml of oil and 4ml of distilled water were added into the test tubes.  

Group	Oil
1,5,9	Palm oil
2,6,10	Arachis oil
3,7,11	Olive oil
4,8,12	Mineral oil

 

For our group we were using Arachis oil.   3. Span 20 and Tween 80 were added to the mixture of oil and water in each of the test tube.  The mixture was closed and the content was mixed by using a vortex mixer for 45 seconds. The time for the interface to reach 1cm was recorded and HLB value of each mixture was calculated and determined. Step 1 to 3 were repeated to obtain the average value of HLB.  

 

Tube no.	1	2	3	4	5	6	7	8
Span 20 (drops)	15	12	12	6	6	3	0	0
Tween 80 (drops)	3	6	9	9	15	18	15	0

 

4. A few drops of Sudan III solution was added to the most stable emulsions in weighing boat and homogeneously mixed. Some of the mixture was spread on the glass slide and observed under the light microscope under magnification x10. The appearance of the emulsion was captured by taking a picture of it. 

5. The Mineral Oil Emulsion (50g) was prepared as the formulation given by using wet gum method.

 

Emulsion	Group	Mineral Oil (ml)
I	1,5,9	20
II	2,6,10	25
III	3,7,11	30
IV	4,8,12	35

For our group, we are using 25ml of Mineral oil.  

 

Mineral Oil	25ml
Acacia	6.25g
Syrup	5ml
Vanillin	2g
Alcohol	3ml
Distilled water	to 50ml

 

6. The emulsion was placed into the 50ml beaker and stirred by using magnetic stirrer on a plate stirrer for 2 minutes.

7. 2g of emulsion was placed into a weighing boat and labelled. A few drops of Sudan III solution was added and mixed. The texture, consistency, degree of oily appearance and colour spreading in the sample were compared under the light microscope with magnification x10.

8. The viscosity of the emulsion formed after homogenization was determined by adding 15ml of emulsion into 50ml beaker by using viscometer. The viscometer was calibrated with spindle LV-4 type. The emulsion was exposed into the water bath with a temperature 45 °C for 10-15 minutes then into the refrigerator which temperature 4 °C for another 10-15 minutes. Lastly in the room temperature for 10-15 minutes. The viscosity of emulsion was determined after the temperature cycle.

9. 5g of homogenized emulsion was added into the centrifugation tube and centrifuged with 4500 rpm for 10 minutes under 25 °C. The separation height was measured and the ratio of the height separation was determined. 

 

RESULT

1. Time needed for the interface to reach 1cm.

Sample	Palm Oil (Group 1)	Arachis Oil (Group 2)	Olive Oil (Group 3)	Mineral Oil (Group 4)
	Time needed (min)
1	136.5	Does not form interface after 120 minutes	64.45	Interface does not reach 1 cm after 90 minutes
2	62.5	Does not form interface after 120 minutes	Does not form interface after 120 minutes	Interface does not reach 1 cm after 90 minutes
3	112	Interface does not reach 1 cm after 120 minutes	93.27	Interface does not reach 1 cm after 90 minutes
4	50.5	50	19.92	Interface does not reach 1 cm after 90 minutes
5	19.5	Interface does not reach 1 cm after 120 minutes	24.78	Interface does not reach 1 cm after 90 minutes
6	63.5	93	16.73	10.0
7	60.5	19	25	7.0
8	3	25	3.7	0.22

Table 1

 

  2. Average HLB Value for each sample.

Sample	1	2	3	4	5	6	7	8
HLB Value	9.67	10.73	11.34	12.44	13.17	14.09	15.00	0

Table 2

 

3. Appearance of emulsion under light microscope.

Size of globule: uniform and evenly distributes (except for palm oil).  

Palm Oil (Group 1)	Arachis Oil (Group 2)
Olive Oil (Group 3)	Mineral Oil (Group 4)

Table 3

 

4. Appearance of emulsion.

Mineral Oil (mL)	Picture of magnification (10x)	Texture	Consistency	Degree of oily appearance	Spreading of colour
20 (Group 1)		Smooth milky and homogenous mixture	Consistent and easy to pour	Large and small globules appear and a layer of oil floods on top of mixture	The red colour is evenly spread within the small and big droplets
25 (Group 2)		Less viscous and watery	Thick and easy to pour	Appears as oily	The red colour is slowly and evenly spread
30 (Group 3)		Homogeneous, smooth, shiny and milky	Very consistent	Little greasy	Shiny and evenly spread
35 (Group 4)		Look pale, very viscous	Flowy	Large and small globules appears	Uneven colour of spreading

Table 4

 

5. Viscosity of the emulsion formed after homogenization.

Viscosity (cP)
Mineral Oil (mL)	Before Temperature Cycle			Average	After Temperature Cycle			Average	Difference (%)
20 (Group 1)	186	204	228	206	162	144	144	150	37.33
25 (Group 2)	18	18	18	18	35	37	42	38	52.63
30 (Group 3)	23.9	25.1	–	24.5	59.0	56.4	–	57.7	57.54
35 (Group 4)	684	678	680	680.67	900	930	970	933.33	27.07

Table 5

 

6. Ratio of separation phase.

Mineral Oil (ml)	Ratio of separation phase			Average
20 (Group 1)	0.78	0.78	0.79	0.78
25 (Group 2)	0.62	0.65	0.62	0.63
30 (Group 3)	0.54	0.57	0.56	0.56
35 (Group 4)	0.40	0.39	0.41	0.40

Table 6

 

DISCUSSION

     An emulsion is a colloid of two or more immiscible liquids where one liquid contains a dispersion of the other liquids. In other words, an emulsion is a special type of mixture made by combining two liquids that normally do not mix. The excipient is added to the emulsion to stabilize the emulsion that prepared. In this experiment, HLB value of each test tube that have different number of drops of Span 20 and Tween 80 is calculated. There are also four different types of oil which is palm oil, Arachis oil, olive oil and mineral oil. 

 

     HLB stands for Hydrophilic-Lipophilic Balance. The HLB method is used to determine the quantity and type of surfactant that is needed to prepare a stable emulsion. The experiment that we have done has clearly shown the effects of HLB surfactant on the stability of the emulsion. Emulsifier with low HLB value (below 9.0) is lipophilic in character while the one that is hydrophilic in nature possesses a high HLB value (above 11.0). Those with an HLB value in between 9-11 are intermediate.

 

     The first experiment conducted is to observe the average time taken for the interface between two phases in emulsion with various HLB to reach 1 cm. Generally, the emulsion contains 50% (4 ml) water and 50% (4 ml) oil with various ratio of combination of surfactants to produce emulsion with various HLB. The Span emulsifiers are usually lipophilic and the Tween products are usually hydrophilic. In this experiment, eight simple emulsions were prepared in eight test tubes with each have the same amount of oil and distilled water. The test is conducted with different types of oil which includes Palm Oil, Arachis Oil, Olive Oil, and Mineral Oil. Different amounts of Tween and Span were added to the test tubes. Theoretically, the HLB value required Palm oil is 8, Arachis oil 6, Olive oil is 7 and mineral oil emulsion is 10. The HLB value required means as the most optimum or ideal HLB value of surfactant /combination of surfactant that can maximise the stability of the emulsion in given system of using particular oil.

 

    During the experiment, our group (Group 2) conducted this experiment using Arachis oil. From the result obtained, the test tube 1 and 2 produced among the most stable emulsion as it takes longest time for phase separation to reach 1 cm which is do not form interface after 90 minutes while test tube 3, 4, 5, 6, 7, and 8 is the less stable as it takes a shorter duration of time for phase separation to reach 1 cm.  Even if the HLB value of test tube 1, 2, and 3 which are 9.67, 10.73, and 11.34 respectively is further from HLB value required of Arachis oil which is 6, the result still can be accepted as the nature of surfactant is said can also be influenced by temperature and other factors.

 

      Other than that, in Table 1, it is shown that the result for Palm oil from Group 1. As we can see from the table, test tube 1 has the longest time taken for the interface to reach 1 cm which indicates that it is the most stable emulsion. It is because the separation of phase need the longest time to occur. These show that the ratio of surfactants used are the most closest to the ideal ratio of surfactant needed to stabilize palm oil emulsion. Next, test tube 3 shows intermediate stability which the phase separation take shorter time than test tube 1 but longer time that the others (test tube 2, 4, 5, 6, 7and 8). It is shows that test tube 2,4,5,6,7 and 8 did not suitable ratio to stabilize the emulsion.

 

For olive oil, we can observe from the Table 1 that the test tube 2 and 3 produced among the most stable emulsion as it takes longest time for phase separation to reach 1 cm while test tube 1 have intermediate emulsion stability. Test tube 4, 5, 6, 7, and 8 is the less stable as it takes a shorter duration of time for phase separation to reach 1 cm. These shows that the ratio of surfactants in test tube 2 and 3 is suitable to produce stable olive oil-based emulsion. The HLB required for olive oil is 7.

 

  Furthermore, based on the Mineral oil emulsion result shows that test tube 1,2,3,4,5 have the longest time time taken for the interphase to reach 1 cm while test tube 6,7 and 8 have the shortest time taken . It is indicates that test tube 1,2,3,4 and 5 have the most stable surfactant ratios to stabilize the emulsion. The best ratio of the surfactant must have HLB value that closest to the HLB value required for Mineral oil emulsion.

 

      Sudan III is a fat soluble dye which stains the oil molecule red. Sudan III test can be used to determine the type of emulsion, shape and size of the globules in the emulsion. If a red background is observed in the emulsion, it is a w/o emulsion as oil is the continuous phase whereas if red globules are present in a clear background, it is an o/w emulsion. In test tube 1 of Arachis oil, the size of globules formed are relatively uniform and evenly distributed. A few medium and large globules are seen. Sudan III solution or red colour solution is slowly and evenly spread in test tube 1. This is due to the difficulty of the Sudan III molecule to penetrate the surfactant barrier around the oil molecule. Therefore, we can conclude that emulsion 1 is the most stable due to the appropriate amount of emulsifier.

 

     The next experiment is preparing mineral oil emulsion using wet gum method to produce oil in water (o/w) type of emulsion. The emulsion was produced with different amounts of mineral oil which is 20ml, 25ml, 30ml and 35 ml. Several excipients were incorporated into the emulsion to ensure good stability of the emulsion such as acacia, vanillin, alcohol and syrup. Acacia acts as a surface active agent to ensure the dispersed phase can be dispersed and incorporate evenly in the continuous phase. Acacia also increase the kinetic stability of an emulsion so that the size of the droplets does not change significantly with time and lower the possibilities of emulsion to undergo creaming or breaking process. Syrup is used to increase the viscosity of the emulsion and responsible as a sweetening agent. Vanillin is used as a flavouring agent besides increase patient’ acceptability. Alcohol is used as an antimicrobial agent to prolong the storage time of the emulsion by preventing the growth of microorganisms. 

 

        The purpose of homogenization is to homogenize two immiscible liquid into a smooth emulsion by making the droplets into extremely small particles dispersed evenly in the continuous phase. In this experiment, homogenization plays it role by further breaking the droplets into extremely small droplets.  The unstable emulsion will only become stable after the homogenization because vibration force applied to the big globules can break them into smaller globules which is more stable. Sudan III solution is added to the emulsion to act as a dye which color the oil phase to give a better view under the microscope. From the results obtained, in general, the texture of all the four emulsions will become smooth and more consistent, less oily and the more viscous after homogenization. 

     

After  homogenization, the viscosity of each emulsion is determined. Based on the result for 25 ml of mineral oil shows that the average viscosity before temperature cycle is 18cP while after temperature cycle is 38cP. The difference percentages of viscosity of 25 ml mineral oil is 52.63%. Theoretically, emulsion that have higher amount of oil as dispersed phase will have higher viscosity as oil is more viscous than water. The temperature cycle will also affect the viscosity of the emulsion as it disrupts the adsorbed layer of emulsifying agent at the oil/water interphase. However, the result has shown that some of the viscosities of emulsions produced are not proportional to the amount of oil incorporated as this is observed from the trend for both before and after temperature cycle result. From the result, it can be seen that the result varies significantly between groups which may be due to some errors done when taking viscometer reading or during the experiment. A good and stable emulsion should have a low difference in percentage between before and after the temperature cycle. 

    

Moreover, centrifugation is a separating process to separate aqueous phase and the oily phase. To produce a stable and homogenous emulsion, the phase separation ratio must always be kept at a minimum level, so that the drug can be dispersed uniformly in the emulsion and the administration of accurate dose can be achieved. The higher the viscosity, the lesser the phase separation of emulsion, thus the more stable emulsion. From the experiment, the ratio of separation phase of 20 ml mineral oil shows the highest ratio of separation which is 0.78 because of less viscous. For average ratio of separation emulsion that have mineral oil of 25 ml is 0.62, 25ml is 0.56 and 35 ml is 0.4. From the result of separation phase ratio, it can be concluded that viscosity correlates with the separation phase ratio. Therefore, the viscosity must be kept at a good level to obtain a low separation phase ratio.

    Lastly, several precautions should be taken in this experiment to reduce errors and improve accuracy in the results. Firstly, the emulsion should be mixed homogeneously by using a mortar and pestle. Secondly, eyes must be perpendicular to measuring cylinder’s reading to prevent any parallax error. The rotor at the viscometer should be rinsed before being dipped into another emulsion to prevent any error in viscosity reading. Besides, the emulsion should be stirred well before testing its viscosity.

 

CONCLUSION

     The HLB value required on maintaining a stable can be determined by the type of oil used. For arachis oil, the HLB value required is 6 and the most stable emulsion for this emulsion is Test tube 1 which has the nearest number to 6 which is 9.67. 

     The amount of oil in formulation determined the physical characteristics and stability of the emulsion. If more oil is added into the formulation, the appearance will look oily as the oil becomes the continuous phase. Vice versa, if oil is in small amounts, it becomes the dispersed phase and the appearance become watery. 

     The viscosity of the mixtures increase with the amount of oil added. Oil is more viscous than water. The large viscosity maintains the stability of the emulsion after the centrifugation providing 35 mL of mineral oil in the emulsion is the most stable emulsion with 27.07%, the smallest difference within temperature cycle the smallest ratio of separation which is 0.4 after the centrifugation.

 

REFERENCES

1. https://www.aocs.org/stay-informed/inform-magazine/featured-articles/emulsions-making-oil-and-water-mix-april-2014

2. https://en.m.wikipedia.org/wiki/Emulsion

3. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/centrifugation

UNIVERSITI KEBANGSAAN MALAYSIA

 

 

 

LABORATORY REPORT

DEVELOPMENT OF PHARMACEUTICAL PRODUCTS 1

(NFNF 2213)

 

TITLE                        : THE USE OF WETTING AGENT IN SUSPENSION

GROUP                     : 2

NAME                       : MUHAMMAD RASYDAN BIN BUCHEK     A168185

                                  FARINA ZAHIDAH BINTI ABD AZIZ          A168417

                                  NUR AQILAH BINTI ABDUL KADIR          A169046

                                  LILLIAN YEO FANG FANG                        A167802

 

LECTURER’S NAME  : PROF. MADYA DR. HALIZA BINTI KATAS

 

SEMESTER I, SESSION 2019-2020

FACULTY OF PHARMACY

 

TITLE:

The use of wetting agent in suspension  

 

DATE:

3rd October 2019  

 

OBJECTIVES:

To identify the effect of concentration of tragacanth to the rate of sedimentation of suspensions.  

 

INTRODUCTION:

      The suspension is a heterogeneous mixture where the solute is not dissolved in the solvent but it is suspended in the continuous phase either in liquid or gas form. Mostly, suspension is used for drugs that is not soluble to water and drugs having unpleasant taste and odour. Suspension can be used in oral administration as a flavoured and sweetened formulation which patients able to use them. It is also can be used for non oral administration such as lotion and parenteral medication. 

      Suspension is physically unstable due to they tend to settle after a period of time without agitation. This may lead to lack of uniformity of the drug dispersity and might lead to therapeutic effects. A good suspension should be easily homogeneously dispersed when shaken to prevent therapeutic effects, pourable, have pleasant taste and texture and also uniform particle size. Besides, they should also easy to redispersion of settled solid particles, physically and chemically stable and resistant against microbial contamination. To produce better suspension, a few important aspects regarding particle size distribution, specific surface area, inhibition of crystal growth and changes in the polymorphic form should’ve been given attention. This to make the suspension keep stable even after a long period of storage.

      The amount of suspending agent used in formulation is depends on the volume of vehicle used. It does not vary with the amount of powder in the preparation. A suspending agent function is to increase the viscosity of the vehicle and therefore reduces sedimentation rates and reduce the surface tension. Another way to reduce the sedimentation rate is by decreasing the particle size of the powder in suspension. The most common suspending agents used Tragacanth and sodium lauryl sulphate. For this experiment we are using tragacanth as suspending agents to observe the relationship between concentration of tragacanth and sedimentation rate of suspension.  

 

APPARATUS:

1 x 1 mL graduated pipette	1 x 100 mL beaker
1 x pipette bulb	Parafilm®
1 x weighing boat	1 x Weighing balance
1 x set of mortar and pestle	1 x Viscometer
1 x 50 mL graduated cylinder
1 x 200 mL graduated cylinder

 

MATERIALS:

Chalk	Double strength chloroform water
Tragacanth	Distilled water
Concentrated peppermint water (or any flavoring agent)	Syrup BP

 

PROCEDURE:

1. A suspension of Pediatric Chalk Mixture (150 mL) was prepared according to the following formula:

INGREDIENT		Suspension
	A	B	C	D	D
Chalk (g)	3	3	3	3	–
Tragacanth (g)	0.0	0.01	0.03	0.05	0.1
Concentrated peppermint water (mL)	0.5	0.5	0.5	0.5	0.5
Syrup BP (mL)	15	15	15	15	15
Double Strength Chloroform water (mL)	75	75	75	75	75
Distilled water q.s. (mL)	150	150	150	150	150

 

2. 5 mL of the suspension was poured into a weighing boat and each formulation was labelled.   The texture ,clarity and color of each suspension were observed and compared.

 

3. The sedimentation rate of each suspension was determined. The suspension was shook vigorously to make sure all of the particles were uniformly suspended, and the time wass noted. The boundary between the sediment and the supernatant was observed and  the time took for the boundary to pass each 10 mL graduation until the volume of sediment reached 80 mL was recorded. 

 

**The best way to observe the boundary is to view it directly in front of a light source. A clear and distinct boundary or no obvious boundary was noted.

 

4. The graduated cylinder was set down on the lab bench, and the lab timer was started at this point.

 

5. For suspensions A to D, the sedimentation volume of the suspensions were recorded at time, t=0, 2, 5, 10, 15, and      30 min.

 

6. The obtained data was recorded  in the table.

 

7. The sedimentation volume ratio was calculated using the following formula  :

     Sedimentation volume ratio = Hu/Ho

     Hu: ultimate height of the sediment, the height of the sediment at a particular

              time

     Ho: initial height of the total suspension

 

8. The ease of re-dispersibility of each formulation was examined after the last measurement. To do this:

I. The Parafilm® was made sure to snug on the mouth of the graduated cylinder, and the seal is re-enforce with gloved hand.

II. The number of inversions it takes to completely re-disperse the drug was counted .

III. The observations were recorded.

 

9. 95 mL of suspension was poured  into a 100 mL beaker and the viscosity of the suspension was determined using viscometer at 12 000 rpm for 2 minutes.

 

10.  The data was recorded in the table.

 

11.  Each suspension was poured  into a plastic bottle. After storing all the suspensions for a period of 4 days,  the ease of redispersion and which system was most acceptable were determined in each system was determined.

 

RESULTS:

1. Texture, clarity and colour

Observations	Texture	Clarity	Colour
A	Watery	Not clear	White
B	Thicker than A	Not clear	White
C	Thicker than A	Not clear	White
D	Watery	Translucent	Colourless

 

2. Volume of sendiment

Volume of Sediment	Time taken (s)
	150mL	140mL	130mL	120mL	110mL	100mL	90mL	80mL
A	0	46	87	113	141	215	248	293
B	0	–	–	–	–	–	–	–
C	0	–	–	–	–	–	–	–
D	0	–	–	–	–	–	–	–

 

3. Sedimentation volume at pre-determined time 

Suspension	Sedimentation volume (mL) at pre-determined time (min)						Distinct boundary (yes/no)
	0	2	5	10	15	30
A	150	150	75	27	26	12	Yes
B	150	150	150	150	150	150	No
C	150	150	150	149	148	148	No
D	150	150	150	150	150	150	No

 

4. Sedimentation volume ratio

For Suspension A:

Time (min)	Sedimentation volume ratio
0	150/150 = 1
2	150/150 = 1
5	75/150 = 0.50
10	27/150 =0.18
15	26/150 = 0.17
30	12/150 = 0.08

  For Suspension B:

Time (min)	Sedimentation volume ratio
0	150/150 = 1
2	150/150 = 1
5	150/150 = 1
10	150/150 = 1
15	150/150 = 1
30	150/150 = 1

  For Suspension C:

Time (min)	Sedimentation volume ratio
0	150/150 = 1
2	150/150 = 1
5	150/150 = 1
10	149/150 = 0.99
15	148/150 = 0.99
30	148/150 = 0.99

  For Suspension D:

Time (min)	Sedimentation volume ratio
0	150/150 = 1
2	150/150 = 1
5	150/150 = 1
10	150/150 = 1
15	150/150 = 1
30	150/150 = 1

 

Suspension	Sedimentation volume (mL) at pre-determined time (min)						Distinct boundary (yes/no)
	0	2	5	10	15	30
A	1	1	0.5	0.18	0.17	0.08	Yes
B	1	1	1	1	1	1	No
C	1	1	1	0.99	0.99	0.99	No
D	1	1	1	1	1	1	No

 

5. Ease of redispersibility

A = Easy

B = Easy

C = Easy

D = Easy

B,C and D are easy to disperse because the sediment formed was in small value.

 

6. Viscosity

X = mean

∑ X = sum of viscosity

n = no of recording recorded

   

Suspension	Viscosity (cP)			Mean	Standard Deviation
A	0.66	1.20	0.72	0.86	0.0876
B	1.02	1.68	1.14	1.28	0.1236
C	0.48	0.36	0.54	0.46	0.0084
D	1.32	1.62	1.38	1.44	0.0252

 

7. Ease of redispersion after 4 days storage

A = Hard, required 13 inversions

B = Quite hard, required 10 inversions

C = Quite easy, required 6 inversions

D = Easy, required 3 inversions

 

DISCUSSION:

1. Compare and discuss the physical appearances of all suspensions produced.

In this experiment, four suspensions are prepared with varying amount of tragacanth as wetting agent. The physical appearance in terms of texture, clarity and colour is observed. Tragacanth can give viscosity to the suspension as it has great importance for stability and pourability of suspensions. The presence of wetting agent facilitates the distribution and dispersion of the lyophobic powders. Absence of the tragacanth as the suspending agent causes the suspensions to sediment very fast and the particles are separated into two distinct boundaries.

Based on the observation, Suspension A has the clearest clarity, least viscous and milky suspension among suspension B, C and D. This is due to the absence of tragacanth powder that serves as a viscosity increasing agent. The absence of the tragacanth as suspending agent causes suspension A to sediment very fast. Therefore it shows the clearest distinct boundaries.

In suspension B, the suspension is less viscous than C due to the presence of small amount of tragacanth. It is a bit cloudy due to the insoluble chalk powder which does not dissolve in the solution. The viscosity contributes by the tragacanth gives the colour of milky white. The rate of sedimentation in suspension B is much slower than suspension A. This is due to the presence of the tragacanth as suspending agent which helps to prevent settlement of the suspended solids under gravity. The clarity of this suspensions iss opaque compared to clearer suspensions A because the suspensions does not seem to separate into two separate layers.

Suspension C has greater viscosity compared to B but lower compared to A because of increased amount of tragacanth. The texture is very smooth and cloudy because tragacanth helps to suspend and distributes the insoluble particle evenly. The colour of milky white is due to the viscosity and the chalk powder. The sedimentation rate of suspension C is higher than suspension B due to greater amount of tragacanth added. 

Suspension D is the most vicious because it contains the highest amount of tragacanth with no chalk. It has the thickest texture. This is because suspension D contained the highest amount of tragacanth but does not contain chalk, the active ingredient to be suspended in aqueous phase. Due to the absent of tragacanth, the chalk particles tend to sediment quickly and left the top part free from chalk particles.

 

2.Plot Hu/Ho vs time for each of the suspension ( Table 1 ). Discuss the findings. 

Sedimentation volume ratio is the ratio of the ultimate height or volume of sediment (Hu) to the original height or volume of sediment (Vo) before settling. 

From the graph shown above, the sedimentation volume ratio for suspension A increases a little then decreases with time. This is due to absence of tragacanth which act as wetting agent and suspending agent which can stabilize and disperse the indiffusible solid uniformly in the suspension. Therefore, sedimentation occurs the fastest in suspension A. However, as time goes by, the graph decreases sharply and slightly towards the end. This is because the suspension starts to form sediment or flocculation system. As the flocs is pulled down to the bottom, it will form flocs and start to compact. Eventually, sediment is formed. 

Sedimentation volume ratio for suspensions B, C and D are quite constant with time. This may due to the presence of tragacanth, which act as wetting agent or suspending agent. So, the indiffusible solid chalk particles can disperse uniformly in the suspension and less tendency or slower to form sedimentation. The reason for graph to show almost constant value may be because sedimentation did not occur during that period of time. The suspension may require a longer time to sediment.

 

3. Briefly explain the principle of analysis using viscometer. Plot the viscosity vs  tragacanth content (Table 2 ). Discuss the findings.

A viscometer is an instrument used to measure the viscosity of a fluid. Generally, a specifically selected spindle is immersed in a sample of liquid or product and the viscosity if measured according to the torque required to rotate the spindle at a preset speed. This torque has to overcome the viscous forces of the tested substance and is therefore a measure for its viscosity. The viscometer works according to the principle of Searle and Couette. 

According to Searle Principle, the motor drives the cup while the bob is stationary to minimize the risk of turbulent flow. According to Couette Principle, the measuring bob or spindle is driven by a motor in a container filled with fluid. The driving speed is preset and the torque required to turn the measuring bob against the fluid’s viscosity is measured.

Theoretically, tragacanth content is directly proportional to viscosity. The greater the amount of tragacanth, the more viscous the suspension. Tragacanth acts as suspending agent that suspends and stabilises the active ingredient by increasing the viscosity of the suspension, preventing sedimentation as per Stokes Law. So, suspension A is the least viscous suspension and suspension D is the most viscous suspension. viscosity increases with the amount of tragacanth. This is because suspension A does not contain any tragacanth. This can cause instability, hard to redisperse and increase in sedimentation rate. Meanwhile, suspension D contains only tragacanth, thus increasing the viscosity of the liquid. 

There is an error in suspension C, which supposedly should have higher value of viscosity than suspension B but lower than suspension D. This may due to error occurs when handling the viscometer.

 

4. After storing the suspensions for a period of 4 days, determine the ease of  redispersion for each.

After storing for 4 days, the ease of redispersion are as shown:

Bottle	A	B	C	D
No. of inversion	13	10	6	3

 

After storing the suspensions for a period of 4 days, it is found that suspension D require the least number of inversions among suspensions A, B and C. This means that suspension D is the easiest to be dispersed among all the suspensions. This is because it contained the greatest amount of tragacanth as suspending agent without any chalk which suspend in the liquid. Tragacanth can also act as a wetting agent which can lower the interfacial tension of suspension liquid. Suspension A needs the highest number of inversions, thus it is the most difficult to redisperse. This is because it only contains chalk without any tragacanth as suspending agent to stabilise the suspension.

For suspension B, it needs higher number of inversions compared to suspension C because it contains less amount of tragacanth. Therefore, suspension B is less stable compared to suspension C and prone to sedimentation. So, suspension B is harder to redisperse.

 

5. Based on all observation, which product would be considered to be most  acceptable? Explain.

Based on all observations, suspension C is consider to be most acceptable. This is because suspension C contained the greatest amount of tragacanth among suspension A and B, without comparing to suspension D. The greater the amount of tragacanth, the more viscous the suspension was. The more viscous the suspension, the more stable the suspension is. Therefore, suspension C has the lowest sedimentation rate, lowest interfacial tension and most suitable viscosity. This prevent the finely insoluble chalk which suspends in the liquid to agglomerate, agitate and form cake. Besides, it also requires the least number of inversions. This shows that it is easily redisperse into original suspension. Meanwhile, suspensions A and B containes less amount of tragacanth, so they has a higher sedimentation rate and higher interfacial tension. Thus, the suspension is not stable and has a higher tendency to cause sedimentation and caking. Suspension D is not suitable as it containes only tragacanth without any chalk which act as active ingredient.

 

CONCLUSION:

The effect of concentration of tragacanth, which act as wetting agent and suspending agent can help to lower the rate of sedimentation of suspensions. The concentration of tragacanth can also changes viscosity of the suspension. The more the amount of tragacanth, the higher viscosity of suspension. Eventually, the suspension is more stable as it less likely to sediment, which is bad for pharmaceutical products. 

For this experiment, suspension D gives highest viscosity and took the longest time to sediment. However, because there was no active ingredient for suspension D and suspension C is the best sample for suspension as it exhibits like a drug suspension with chalk as active ingredient and more stable compared to suspension A and B.

 

REFERENCE:

1. https://www.slideshare.net/Muwela001/pharmaceutical-suspension

2. http://www.uobabylon.edu.iq/eprints/publication_3_31242_6264.pdf

3. http://abacus.bates.edu/~ganderso/biology/resources/centrifugation.html