Suspension

Title:

Evaluation on the effect of different composition of tragacanth on the characteristics of a suspension.

Objective:

To study the appearance, clarity and colour of a suspension, the rate of sedimentation and viscosity of the suspension based on different compositions of tragacanth used.

Introduction:

Suspension is a class of pharmacpoeial preparations of finely divided, undissolved drugs of powders for suspension dispersed in liquid vehicles for oral or parenteral use. The dispersed phase of a suspension is the solid whereas the continuous phase is the liquid. For medicine that comes in suspension form, shake well before using to receive the right amount of drug every time when taking it. Otherwise, there will be little drug received in the beginning, and too much drug in the end. Good suspension has a uniform solid particle size physically and chemically stable, resistant to microbial contamination, and possesses better texture and feel. It should be easily poured from the container and the sediments are easily redispersed after shaking to form a homogeneous suspension.

            Active ingredients (solid phase), wetting agents, flavouring, colouring agents and preservatives are included in a suspension. Tragacanth, which is a wetting agent is used to reduce the interfacial tension between solid particles and liquid. When the diameter of the particles is more than 1µm, it is classified as course suspension. Colloidal suspension has particle size less than 1µm. In general, suspension is used to improve the stability of the active ingredient, taste and bioavailability of the formulation.

 Apparatus:

Mortar and pestle, 50mL measuring cylinder, 200mL measuring cylinder, 1mL pipette and bulb-pipette, 15mL centrifuge tube, centrifugation machine, coulter counter, 100mL beaker, viscometer, and weighing boat.

Material:

Tragacanth, chalk, concentrated peppermint water, syrup BP, double strength chloroform water, and distilled water.

Methods:

1.      A suspension of Paediatric Chalk Mixture (150ml) is prepared using the formulation below:

Chalk Tragacanth Concentrated Peppermint Water Syrup BP Double Strength Chloroform Water Distilled Water, q.s.

3g Refer to table below 0.6ml 15ml 75ml 150ml

Paediatric Chalk Mixture	Group	Tragacanth (g)
I	1, 5	0.0
II	2, 6	0.1
III	3, 7	0.3
IV	4, 8	0.5

2.      Some of the suspension formed (5ml) is poured into the weighing boat and labelled. State and compare the texture, clearness, and colour of the suspension formed.

3.      50ml of suspension formed is poured into the 50ml measuring cylinder and the height of the solid phase sediment in the cylinder is measured at intervals of 0, 5, 10, 20, 25, 30, 40, 50 and 60 minutes.

4.      The remaining suspension (95ml) is poured into a 100ml beaker and viscosity of the suspension formed is determined using a viscometer.

 

5.      10ml of suspension is poured into a centrifugation tube and the height of the solid phase formed after centrifugation (1000rpm, 5 minutes, and 25⁰C) is determined.

     Result: 

Time (minute)		Height of the sediment (millimetre)
		0	5	10	15	20	25	30	35	40	45	50	55	60
Amount of tragacanth (g)	0.0	9.5	1.8	1.2	1.2	1.2	1.2	1.2	1.2	1.2	1.2	1.2	1.2	1.2
	0.1	11.9	11.9	11.8	11.7	11.7	11.4	11.2	11.1	10.8	10.7	10.6	10.6	10.4
	0.3	0	9	11	11	12	13	13	14	14	14	14	14	14
	0.5	0	1	4	8	10	15	18	20	21	22	22	22	22

Reading	0.0	0.1	0.3	0.5
Concentration (CP)(X+/- SD)	10.004	5.925	12.851	9.110

Amount of Tragacanth (g)	Height (mm)		Height ratio
	Before centrifudge	After centrifudge
0.0	24	6	4:1 = 4
0.1	5	15	5:14 = 0.3571
0.3	7.9	1.4	79:14 = 5.6429
0.5	2	18	1:9 = 0.1111

    

 

Questions: 

1)   Compare the physical characteristics of the suspensions and give your comment.

Pediatric chalk mixture	Amount of tragacanth (g)	Texture	Clarity and appearance	Colour of suspension
I	0.0	More watery, less viscous, easy to sediment and disperse	Less cloudy, 2 layer on sedimentation	Less milky
II	0.1	Viscous, easy to sediment and disperse	Opaque, moderate cloudy	Milky white
III	0.3	Viscous, less easy to sediment, easily disperse	Opaque, more cloudy	Milky white
IV	0.5	Highly viscous, difficult to sediment	Opaque and highly cloudy	Milky white

The 4 suspension preparation has different composition of tragacanth. Tragacanth is a suspending agent which increases the viscosity of suspension and thus slowing down the sedimentation of particles within suspension. Tragacanth increases the viscosity by providing “structures” to the medium. As the amount of tragacanth increases, the texture of suspension will become less watery and more viscous. The higher the viscosity, the more difficult to sediment.

All of the suspension appeared cloudy, the cloudiness indicates the particles dispersed in liquid medium. In suspension I (without suspending agent: tragacanth) , it is less cloudy and easy sediment to form 2 layer ( liquid and sedimentation).

2) Plot a graph of sedimentation height against time and give explanation based on the graph.

TIME (MIN)	HEIGHT (MM)
0	95
5	18
10	12
15	12
20	12
25	12
30	12
35	12
40	12
45	12
50	12
55	12
60	12

At first, Height of sediment is well distributed in the tube. However, it begins to decline gradually when time is increased. At minute 10, the height of sediment is 12 mm and it remains plateau till the end of experiment. All the sediment gathered below and it cannot be well suspended due to absence of suspending agent that is Tragacanth. 

3)   Plot the graph of height of solid phase against time for different amount of tragacanth in the suspension. Give your comment.

Time (minute)		Height of the sediment (millimetre)
		0	5	10	15	20	25	30	35	40	45	50	55	60
Amount of tragacanth (g)	0.0	9.5	1.8	1.2	1.2	1.2	1.2	1.2	1.2	1.2	1.2	1.2	1.2	1.2
	0.1	11.9	11.9	11.8	11.7	11.7	11.4	11.2	11.1	10.8	10.7	10.6	10.6	10.4
	0.3	0	9	11	11	12	13	13	14	14	14	14	14	14
	0.5	0	1	4	8	10	15	18	20	21	22	22	22	22

Graph above relates the height of sedimentation against time for 4 suspension formulation. Tragacanth acts as suspending agent, it slows down the sedimentation by structuring the continuous phase to produce a deflocculated system. For formulation with optimum amount of tragacanth, the system is stable and no slow flocculation occurs. Tragacanth enables the particles to remained suspended for a longer time within suspension and take longer time to sediment.

The greater amount of tragacanth, it will slows down sedimentation of particles and form a lower height of sedimentation. Thus, suspension IV with 0.5g tragacanth shows slowest sedimentation compared to others suspension.

The suspension I without any tragacanth achieve constant height of sedimentation in very short time of 10 minutes and remains constant throughout the following period. It is because the suspension without suspending agent (tragacanth), there will be rapid sedimentation as compared to other curve and it has maximum height of sediments as compared to graph of other suspensions. 

4)  Explain briefly mechanism of viscometer analysis. A graph was plotted of concentration against Tragacanth content (g).  Give a comment.

Reading	0.0	0.1	0.3	0.5
Concentration (CP)(X+/- SD)	10.004	5.925	12.851	9.110

5)     Plot a graph on height ratio of sedimentation against amount of tragacanth and give comment.

Amount of Tragacanth (g)	Height (mm)		Height ratio
	Before centrifudge	After centrifudge
0.0	24	6	4:1 = 4
0.1	5	15	5:14 = 0.3571
0.3	7.9	1.4	79:14 = 5.6429
0.5	2	18	1:9 = 0.1111

Based on the graph, the height ratio upon centrifuging increases with the increased amount of tragacanth. Theoretically, the height ratio should be decreased with the increased amount of tragacanth. This is due to tragacanth as suspending agent. Tragacanth reduces the sedimentation rate of the suspension. It increases the viscosity of the liquid particles and therefore slowing down the settling of the solid particles. Hence, the mass of tragacanth powder increases, less chalk powder will sediment at the bottom of the tubes, the separation of the suspension will be lesser and the height ratio should be decreased. However, the result is incorrect due to some experimental errors.  

6)  What is the function of each ingredient used in the suspension preparation? How does the different amount of Tragacanth powder affect the physical characteristics and stability of the suspension formulation?

Ingredient	Function
Chalk	Adsorbent and antacid also is an ingredient of mixture powders used in the treatment of diarrhea
Tragacanth	Suspending agent to suspend and stabilize the chalk in the suspension
Concentrated Peppermint Water	Make the flavor and smell of the suspensions and to increase patient acceptance
Syrup BP	Make the suspensions more viscous also a sweetening and flavoring agent
Double Strength Chloroform Water	Acts as the flavorings agent, preservative and solvent
Distilled Water qs	Vehicle to carry all the active ingredients in the pharmaceutical suspensions into patient’s bodies

Tragacanth is used to increase the viscosity of the suspension which is necessary to prevent sedimentation of the suspended particles as per Stoke’s law. As the higher the amount used in the formulation, the lower the rate of sedimentation. Suspensions that do not use tragacanth do not have good stability and the solid particles inside will sediment rapidly but easy to redisperse. Moreover, the suspension containing large amount of Tragacanth powder is more stable and less flocculation compared to those having smaller amount of tragacanth powder.

Conclusion: 

Tragacanth acts as suspending agent and affect the sedimentation rate of suspension. Amount of tragacanth also affects the sedimentation height and viscosity of suspension. 

References: 

1)  Ghosal & Srivastava, 2009. Fundamentals Of Bio analytical Techniques And Instrumentation. PHI Learning Pvt. Ltd.

2) John F. Marriott, Pharmaceutical Compounding And Dispensing, 2006, Pharmaceutical Press Sdn Bhd