Evaluation methods of Suspensions, IP suspensions and MCQs for GPAT, NIPER, Pharmacist and Drug Inspector exam

Evaluation of Suspensions:

1. Sedimentation method
2. Rheological method
3. Electro kinetic method

1.Sedimentation method : Two parameters are studied for determination of sedimentation:

• Sedimentation volume
• Degree of flocculation

Sedimentation volume –

• The suspension formulation(50mL)was poured separately into100mL measuring cylinders and sedimentation volume was read after 1,2,3 and 7days,and there after at weekly intervals for 12 weeks.
• Triplicate results were obtained for each formulation. Sedimentation volume was calculated according to the equation:

                                                                          F = Vu/Vo

Where, F =sedimentation volume ,

 Vu = ultimate height of sediment

Vo=initial height of total suspension.

Degree of flocculation –

It is the ratio of the sedimentation volume of the flocculated suspension ,F , to the sedimentation volume of the deflocculated suspension, F∞ ß = F / F∞ The minimum value of ß is 1,when flocculated suspension sedimentation volume is equal to the sedimentation volume of deflocculated suspension.

2.Rheological method: It provide information about Settling behaviours.

Brookfield viscometer is used to study the viscosity of the suspension .It is mounted on heli path stand and using T-bar spindle. T-bar spindle is made to descend slowly into the suspension and the dial reading on the viscometer is then a measure of the resistance the spindle meets at various level. This technique also indicates at which level of the suspension the structure is greater owing to particle agglomeration. The dial reading is plotted against the number of turns of the spindle. The better suspension show a lesser rate of increase of dial reading with spindle turns, i.e. the curve is horizontal for long period.

Figure 1 – Brookfield viscometer 

3.Electrokinetic method: Measurement of Zeta-potential using Micro electrophoresis apparatus & Zeta Plus (Brook haven Instruments Corporation , USA). It shows the stability of a disperse system.

The zeta potential of the formulated suspensions was determined using a Zeta Plus.(Brook haven Instruments Corporation ,USA).

• Approximately 1mL of suspension was transferred into a plastic cuvette using a pipette and diluted with distilled water.
• The Brookhaven zeta potential software was used for the measurement.
• Parameters set to a temperature of 250C and refractive index(1.33).
• The zeta potential of the formulations was determined on day 0,7, 14,21and day 28 post formulation.

Figure 2 – Effect of zeta potential of properties of suspension

IP suspensions:

• Acetaminophen oral IP suspension
• Paracetamol oral suspension

Multiple choice questions:

1.Which of the following methods are used for evaluation of suspensions?

a)Sedimentation method

b)Rheological method

c)Electro kinetic method

d)All of these

2.Which parameters are studied for determination of sedimentation?

a)Sedimentation volume

b)Degree of flocculation

c)Both of these

d)None of these

3.Sedimentation volume is determined by

a)F = Vo/Vu

b)F = Vu/Vo X 100

c)F = Vu/Vo

d)F = Vu/Vo+1

4.F = Vu/Vo In this equation F is

a)sedimentation volume

b)ultimate height of sediment

c)initial height of total suspension

d)inner diameter of the container used

5.F = Vu/Vo In this equation Vu is

a)sedimentation volume

b)ultimate height of sediment

c)initial height of total suspension

d)inner diameter of the container used

6.F = Vu/Vo In this equation Vo is

a)sedimentation volume

b)ultimate height of sediment

c)initial height of total suspension

d)inner diameter of the container used

7.The minimum value of ß is ____,when flocculated suspension sedimentation volume is equal to the sedimentation volume of deflocculated suspension.

a)0

b)1

c)2

d)5

8.The ratio of the sedimentation volume of the flocculated suspension ,F , to the sedimentation volume of the deflocculated suspension is

a)Sedimentation volume

b)Degree of flocculation

c)Force of flocculation

d)Amount of flocculation

9.It provide information about Settling behaviours

a)Sedimentation method

b)Rheological method

c)Electro kinetic method

d)All of these

10.Which instrument is used to study the viscosity of the suspension?

a)Brookfield viscometer

b)Stalagmometer

c)Pycnometer

d)All of these

11.Brookfield viscometer is T-bar spindle type.

a)true

b)false

12.The dial reading in Brookfield viscometer is plotted against

a)number of turns of the spindle

b)length of spindle

c)height of spindle

d)none of these

13.The better suspension show a greater rate of increase of dial reading with spindle turns.

a)true

b)false

14.Measurement of Zeta-potential shows

a)stability of a disperse system

b)bioavailability of a dispersed system

c)solubility of a dispersed system

d)all of these

15.Measurement of Zeta-potential can be done by using

a)Micro electrophoresis apparatus

b)Zeta Plus

c)Both of these

d)None of these

Solutions:

1. d)All of these
2. c)Both of these
3. c)F = Vu/Vo
4. a)sedimentation volume
5. b)ultimate height of sediment
6. c)initial height of total suspension
7. b)1
8. b)Degree of flocculation
9. b)Rheological method
10. a)Brookfield viscometer
11. a)true
12. a)number of turns of the spindle
13. b)false
14. a)stability of a disperse system
15. c)Both of these

References:

1. Gaurav K. Jain Theory and Practice of Physical Pharmacy, 1st edition 2012 Elsevier, page no. 218-220.

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