SUSPENSION

Title

Evaluation of the effects of different ingredients on the characteristics of suspension.

Objective

To determine the effects of different amount of tragacanth resulted on a suspension.

Introduction

Suspension formulation is a type of dispersed system where the solid molecules do not dissolved homogenously in the liquid phase. A good suspension must stay in the state of homogenous after being shaken, be easy to pour out from the container and having a uniform solid particle size, and also attractive taste and texture. Precipitation formed from the storage must be easily dispersed again after shaken and the dispersion formed must be homogenous. Normally, suspension composed of active ingredient (solid phase) dispersed in the   liquid carrier, wetting agent, flavoring agent and coloring agent. Wetting agent (ex: Tragacanth) is used to reduce the surface tension between solid particle and liquid. Suspension is classified as coarse suspension where the particle diameter is more than 1 µm, or colloidal suspension where the particle size is less than 1 µm. In pharmaceutics, suspension is used to improve the stability, the taste and the bioavailability of the active ingredient.

Apparatus

The apparatuses are weighing balance, weighing boat, mortar and pestle, plastic bottle 150ml, measuring cylinder 50ml, measuring cylinder 200ml, a set of pipette (1ml) and bulb-pipette, centrifugation tube 15ml, beaker 100ml, centrifugation equipment and viscometer.

                       

Materials

The materials required are chalk, tragacanth, 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:

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, 15, 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 25°C) is determined.

Results:

Table 1: Height of sedimentation

Table 2: Physical characteristic of suspension

Figure 1: Observation on physical characteristic of suspension

Table 2: Viscosity of suspension

Table 3: Height of sedimentation after centrifuge

Discussion:

1. Compare the physical characteristics of the suspension formed and give explanation.

Mixture I do not contain Tragacanth in their formulation. Therefore, the suspension has a rough texture, more watery and less viscous but it is easy to sediment and redisperse. This is because no suspending agent adsorbs on the particle surface provide low affinity to water, hence it forms 2 layers providing a poor suspension. It is also less cloudy due to absence of Tragacanth. Formulation II, III and IV contain Tragacanth. Therefore, the texture becomes smoother and more viscous as the weight of tragacanth used increase gradually. The formulations have one layer and do not sediment easily. In other words, the formulations are stable. Suspending agent gives thicken and provide ‘structure’ for the medium hence those formulations II, III and IV are cloudy and give milky white colour. Amount of tragacanth must not be too high as it will become too viscous to agitate and pour.

2. Plot a graph of height of sediment vs. time. Give explanation.

The graph above is the formation of sediment for formulation IV. Sediment starts to form after 10 minutes. With increasing the time, the height of the sediment increases. Sedimentation occurs due to the gravitational forces in which comparatively large drug particles will be sedimented. The height of the sediment becomes constant when all the chalk particles are sedimented.

3. Plot a graph of height of sediment vs. time for the formulation of suspension that contain varied amount of Tragacanth. Give explanation.

For suspension without tragacanth, the height of sediment formed increased at the beginning but gradually decreased after that. Basically, the height of sediment for suspension with 0.1g, 0.3g, and 0.5g increases overtime. Tragacanth is a polymeric flocculating agent. It is used to control flocculation. It forms gel-like network by adsorbed to the particles and hold them in flocculation state. So at the beginning, the 3 suspensions mentioned did not have any sediment because the tragacanth holds the particles in flocculation state. From the experiment, the more the volume of tragacanth, the suspended particles take longer time to settle at the bottom. For suspension without tragacanth, the particles settle easily. Thus, the height of sediment increased dramatically at the beginning. But the trend is followed by gradual decrease. This is because the particles get closer together. When the particles get closer together, the interparticular forces between them become stronger and pull closer to each other. Less voids present between the particles and thus the sediment become more compact. When the particles become closer to each other and become more compact, the height of sediment will decrease. 

4. Explain the analysis mechanism of the viscometer. Plot a graph of the viscosity of the suspension versus the content of Tragacanth. Give the explanation.

         A viscometer is used in the measurement of the viscosity of the suspension. A viscometer is also known as viscosimeter. It is an instrument used to measure the viscosity of a fluid. Viscometers only used to measure under one flow condition. Viscosity can be measure by the drag caused by relative motion of the fluid and a surface. There are various types of viscometer, for instances, U-tube viscometers, Falling sphere viscometers, Falling Piston Viscometer, Oscillating Piston Viscometer, Vibrational viscometers, Rotational viscometers, Stabinger viscometer, Stormer viscometer and Bubble viscometer.

The viscometer that used in this experiment operates as the motor of viscometer rotate with a constant speed which is controlled by the central controller. There are different diameters of the stirrer. The stirrer with the larger diameter is used to determine the viscosity of the lower concentration ointment. On the other hand, the stirrer with the lower diameter is used for the higher concentration ointment. Under the constant speed, the viscosity of the solution is determined.

Tragacanth is a suspending agent that is used to suspend the chalk powder in suspension. When the amount of Tragacanth in a suspension increases, the viscosity of the system is also increasing in a gradually manner. Thus, a more stable suspension can be formed. From the result that we obtained from the experiment, the graph plotted shown that the viscosity of the suspension increases gradually with the increase amount of Tragacanth added. Formulation III is the most viscous suspension in this experiment as it recorded average viscosity of 6.58cP with the 0.3g of Tragacanth. The least viscous suspension is Formulation I which without any Tragacanth added into and with a average viscosity of 3.03cP. However, there is a point show some error, which is when the added Tragacanth is 0.5g (Formulation IV). It shows a little lower viscosity than the suspension with 0.3 Tragacanth (Formulation III). This is mostly due to several errors during the experiment, such as the incorrect preparation of suspension or the incorrect amount of Tragacanth added. Besides, the technical error may be due to incorrect usage of viscometer and thus the results that we obtained are inaccurate. All in all, we can conclude that the viscosity of the suspension is proportional to the amount of suspending agent added into the system.

5. Plot a graph of ratio of sediment height as a result of centrifugation vs. weight of Tragacanth. Give explanation. 

Tragacanth in suspension acts as suspending agent to minimize the sedimentation and increase the suspending capacity of disperse system in continuous system. From the result above show that the ratio of sediment height increase as the amount of tragacanth(suspending agent) increased. As we know, the sedimentation rate is higher with the high ratio of sediment due to the time taken of solid particle to sediment at the lower part of the system is longer even the amount of chalk used for all type of these suspensions are same value.

6. What is the function of each material used in the preparation of this suspension? How does the use of this different tragacanth content influence the physical characteristics and the stability of a suspension formulation?

    The materials used in this suspension preparation are chalk, tragacanth, concentrated peppermint oil, syrup BP, double strength chloroform water and distilled water.

     Chalk is the active ingredient in this suspension. It functions as adsorbent that adsorbs excessive fluid in watery faeces and make the faeces more solid. The chalk mixture is used as antidiarrhea. 

   Tragacanth acts as a thickening agent in the suspension. It increases the viscosity of a solution. It also increases the stability of the preparation, where the suspended particles take longer time to settle at the bottom and easily redisperse when the suspension is agitated.

      Concentrated peppermint oil is a flavouring agent that gives the preparation a nice scent.

      Syrup BP functions as a sweetening and also flavouring agent.

    Double strength Chloroform water is used as a preservative. As suspension contains moisture, it is susceptible to microbial growth, therefore we need to put preservative.

      Water is used as a vehicle and bulking agent to add up the volume up to 150 mL.

     A different amount of tragacanth used in the formulation cause the suspension to have different texture, appearance and colour. Based on observation, the more tragacanth used, the more viscous the suspension, as tragacanth is a thickening agent. Suspension with higher amount of tragacanth also appears to be cloudy since the chalk solid is better dispersed. When the tragacanth is not added into the formulation, the solid in suspension separate very fast from the solution. With increasing amount of tragacanth, the colour of suspension looks more opaque and milky. The suspension having a higher amount of tragacanth is more stable, as the suspended solid take a longer time to sediment at the bottom.

Conclusion: 

In conclusion, we can evaluate the effect when using varied amount of Tragacanth and this will influence the physical characteristics and stability of the suspension.

High content of tragacanth produce a suspension with a smooth structure. Suspension is viscous and difficult to spread when compared with the other suspension with a lower content of tragacanth. Suspension with a low content of tragacanth produces a less smooth texture, less viscous and more easily spread again when the precipitate formed at the base of the measuring cylinder.

Therefore, high tragacanth content can produce a stable suspension which does not precipitate with speed, while the contents should be controlled to ensure that the physical characteristics of the formed suspension can be adopted.

References

1. Aulton, M.E. 2002. Pharmaceutics: The science of dosage form design. Edinburgh: Churchill Livingstone
2. Banker, G.S. & Rhodes, C.T. 1990.Modern pharmaceutics.2^nd Ed. New York: Marcel Dekker.
3. Florence, A.T. & Attwood, D. 1998.Physico-chemical principles of pharmacy.3^rd Ed. New York: Macmillan.