EXP 1 : THE USE OF WETTING AGENT IN SUSPENSION

INTRODUCTION

Suspension is a two-phase system consisting of a finely divided solid which is usually the active ingredients is dispersed and suspended through the vehicle or pharmaceutical solvents.

Suspensions are heterogeneous systems consisting of at least two phases.According to British Pharmacopeia (BP), oral suspension is defined as “Oral liquids containing one or greater active ingredients suspended in a suitable vehicle where suspending solids may slowly separate on standing but are easily redispersed. The continuous or external phase is generally a liquid or a semi-solid, and the dispersed or internal phase is made up of particulate matter which is essentially insoluble in, but dispersed throughout, the continuous phase. 

Suspensions are intended for oral administration or topical application such as lotion. Suspension also possesses certain advantages. First of all, insoluble drugs are more stable compared to other dosage form. However, its disadvantage is suspension tend to settle over time leading to disuniformity of the dose. Thus, it required for the patient to shake it well before use. Other than that, we can decrease the rate of sedimentation or to make it easy to redisperse the settled particulate matter by adding wetting agent such as tragacanth. Wetting agent added will be adsorbed at solid/liquid interface resulting in particles having more affinity for surrounding particle. Thus, reducing surface tension.

OBEJCTIVES:
 To determine the effect of different amount of tragacanth on the sedimentation rates of suspensions. 

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	Syrup BP

PROCEDURES:

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

Ingredient	Suspension
	A	B	C	D
Chalk (g)	3	3	3	-
Tragacanth (g)	0.0	0.1	0.3	0.5
Concentrated peppermint water (mL)	0.6	0.6	0.6	0.6
Syrup BP (mL)	15	15	15	15
Double Strength Chloroform water (mL)	75	75	75	75
Distilled water q.s. (mL)	150	150	150	150

2. 5mL of each suspension was poured into a weighing boat and being labelled for each  

     formulation. The texture, clarity and colour of each suspension was observed and   

     compared.

3.  The sedimentation rate of each suspension was determined. The suspension was shaken     

     vigorously to make sure all the particles were uniformly suspended and the  

     time was noted.

4.  The boundary between sediment and the supernatant was observed by putting the suspension   in front of a light source for example flashlight and the time taken for the boundary to pass each 10mL of graduation until the volume of sediment reached 80mL was recorded.  

5.  The gradated cylinder was set down on the lab bench and the timer started at this point.

6.  The sedimentation volume of the suspensions at t=0, 2, 5, 10, 15, and 30 min was recorded.

RESULT :

Suspension	Sedimentation volume at pre-determined time (min)						Distinct boundary (Yes/No)
	0	2	5	10	15	30
A	0	32	21	14	13	11	Yes
B	0	2	4	5	5	6	No
C	0	0.5	0.5	1	1	1.5	No

Table 1: Sedimentation volume at pre-determined time (min) of suspensions

Suspension	Volume of sedimentation (mL)
	A						B						C
	0	2	5	10	15	30	0	2	5	10	15	30	0	2	5	10	15	30
Initial volume of total suspension (Vo)	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100
Ultimate volume of the sediment (Vu)	0	32	21	14	13	11	0	2	4	5	5	6	0	0.5	0.5	1	1	1.5
Sedimentation volume ratio (Vu/Vo)	0	0.32	0.21	0.14	0.13	0.11	0	0.02	0.04	0.05	0.05	0.06	0	0.005	0.005	0.01	0.01	0.015

Table 2: Sedimentation volume ratio of suspensions

Suspension	A			B			C
Trials	1	2	3	1	2	3	1	2	3
Viscosity (cP)	5.36	5.05	4.87	7.68	7.02	6.24	9.30	9.00	8.70
Mean	5.09			6.98			9
SD	0.202			0.589			0.245

Table 3: Viscosity (cP) of suspensions

Physical Characteristics	Paediatric chalk mixture
	A	B	C
Texture	More watery, rough texture, less viscous, easily sediment and rediperse	Less watery, smooth texture, viscous, not easy sediment	Smooth texture, more viscous, no sedimentation
Clarity	Less cloudy	Moderate cloudy	Cloudy
Colour	White	White	Milky white
Layer	2 layer	1 layer	1 layer

Table 4: Physical characteristics of each suspensions

Time (min)	Volume of sediment (mL)
	10	20	30	40	50	60	70	80
Suspension A	0.32	0.40	0.49	1.08	1.22	1.34	1.52	2.04
Suspension B	>30	-	-	-	-	-	-	-
Suspension C	>30	-	-	-	-	-	-	-

Table 5: Volume of sediment of each suspensions (mL)

Suspension	A	B	C
Number of inversion	2	5	12

Table 6: Number of inversion to redisperse

DISCUSSION :

1.         Suspension A do not contain Tragacanth in their formulation. Therefore, the suspension has a rough mixture, 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 less cloudy due to absence of Tragacanth. Suspension B and C contain Tragacanth. Therefore, the texture becomes smoother and more viscous when the weight of Tragacanth used increasing gradually. The suspensions have one layer and do not sediment easily. Suspending agent gives thicken and provide structure for the medium hence those suspensions B and C are cloudy and give milky white colour. Amount of Tragacanth must not be too high because it will be too viscous to agitate and pour.

 

 2.

The sedimentation ratio of the suspension A is the highest compared to suspension B and C.Highest sedimentation volume ratio of suspension A is 0.32 while suspension B is 0.06 and suspension C with 0.015

Tragacanth act as a wetting agent in the suspension B and suspension C.The tragacanth lower chalk particles surface tension,which make the particles able to interact with the medium phase.

In Suspension A which contain no tragacanth,the sedimentation rate is highest,and drastic reduction of sedimentation volume occurs,at about 10 minutes,sedimentation volume reduce slowly.the rate of sedimentation are the highest.

In Suspension B which contain tragacanth 0.1g,there is significant difference between suspension A,the sedimentation volume gradually increase and there is slight increase from time interval between 15-30 minutes.

Suspension C which have greater amount of tragacanth,0.3g,the increase in sedimentation volume are hardly noticeable.The tragacanth help to reduce sedimentation rate.

3.         A viscometer is an instrument used to measure the viscosity and flow parameters of a fluid. There are several types of viscometer which are capillary viscometer, rotational viscometer, rolling ball, falling ball, sphere, and piston viscometers. In this experiment, the viscometer used is rotational viscometer or known as Brookfield viscometer. Rotational viscometers use the idea that the force required to turn an object in a fluid, can indicate the viscosity of that fluid. The viscometer determines the required force for rotating a disk or bob in a fluid at known speed. To be able to measure the sample’s viscosity in the Brookfield viscometer, the material needs to be stationary inside a container while the spindle moves while immersed in the fluid. The viscosity of most materials reduces as temperature increases. Therefore, it is very important for viscometers to have precise temperature controls.

From the graph, we can conclude that the viscosity of the suspension increases as the tragacanth content increases. So, with a higher amount of tragacanth, a better suspension with less sedimentation can be made.

Suspension consists of insoluble solid particle which prone to sediment at the bottom on standing. Thus, tragacanth is used as a suspending agent to lower the interfacial tension and increase the viscosity of suspension which in turn reduces the sedimentation rate.

4.         For suspension A, the number of inversions it takes to completely re-disperse the drug is 7 times, for suspension B, 10 times while for suspension C is 21 times. As the tragacanth content in the suspension increases, it is more difficult to redisperse the suspension.

5.        

           Based on the results and observations, suspension B is considered as the most acceptable stable formulation. Suspension B contains 0.1 g of tragacanth and had the best effect on the suspension stability. High content of tragacanth produce a suspension with a smooth structure. Suspension is viscous and difficult to spread when compared with other suspension with a lower content of tragacanth. Suspension with a lower amount 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.

The smaller the amount of tragacanth, the faster the sedimentation height becomes constant. Tragacanth acts as suspending agent that increases the viscosity of the suspension. The lesser the tragacanth content, the faster the insoluble particles settle at the bottom of measuring cylinder. It is important to produce an ideal suspension that not easily to sediment and easily to redisperse if sedimentation occur.

6.     
            The materials used in this suspension preparation are chalk, tragacanth, concentrated peppermint water, syrup BP, Double Strength Chloroform water and distilled water.

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

            Tragacanth act 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 water is a flavouring agent, which 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 contain moisture, it is susceptible to microbial growth, therefore we need to put preservative.

            Distilled water is used as a vehicle and bulking agent to add up the suspension to certain volume. 

            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 appear to be cloudier since the chalk solid is better dispersed. When tragacanth is not added into the formulation, the solid in suspension separate very fast from the solution. Some part of the suspension looks transparent and some parts looks cloudy. With increasing amount of tragacanth, the colour of suspension having a higher amount of tragacanth is more stable, as the suspended solid take a longer time to sediment at the bottom.

CONCLUSION :

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.

The rate of sedimentation and the height of sediment formed in the suspension depend on the amount of different tragacanth powder used to form the suspension. The higher the amount of tragacanth powder, the lower the height of sediment formed. This is due to the action of tragacanth powder that prevents the solution from forming sediment.