Skip to main content



Substance are optically in the sense that the rotate on incident plane or polarized light so that the transmitted light energy at a measurable angle to the plane of the incident light.

Plane polarized light: 
Plane polarized light

According to wave theory of light, an ordinary ray of light is considered to be vibrating to all planes at right angle to the direction of its propagation.If this ordinary ray of light is pass through a Nicol prism the emergent ray has its vibrations only in one plane.This light having wave motion in only one plane is known as plane polarized light.

Optical Activity:
Optical rotation & construction of polarimeter

When certain organic liquid solution (like sugar) or quartz crystal are placed in the path of plane polarized light, the plane of polarization is rotated.The property by virtue of which the plane of polarization of light is rotated is called optical activity and the substances possessing this property are said to be optically active. Substances which rotate the plane of polarized light toward the right (clockwise) are called dextro rotation (+) while which rotated toward left (anticlockwise) are called laeve rotation (-) .
It has been found that the magnitude of the rotation depend upon the following factors.
  1. Nature of substance.
  2. Length of the liquid column through which light passes.
  3. Concentration of the solution.
  4. Nature of the solvent.
  5. Temperature of the solution.
  6. Wavelength of the light used.     

Polarimeter Principal: 

The optical rotation of a substance is the angle through which the plan of polarization is rotated when polarized light passes through the substance, if liquid or a solution of the substance.
Substance are described as Dextro-rotation (+) or Laevo-rotation (-) according to whether the plan of polarization is rotated clockwise or anticlockwise, respectively as determine by viewing towards the light source.
Specific optical rotation is expressed in degree milliters per decimeter gram.
Calculation the specific optical rotation.

For Liquid [α]²⁵ = α/ld
For Solids [α]²⁵ = 100 α/lc
α = Corrected observed rotation in degrees, at 20°
D = Line of sodium light (589.3 nm)
L = Length of polarimeter tube in dm.
c = Concentration in % w/v

Calibration of polarimeter:

Sucrose used in the calibration of polarimeter previously dried 2 hrs at 105°C and temp. maintaining 25°C ± 0.5°C
Concentration of  Sucrose (%)
Angle of Rotation at (Standard)
25°C ± 0.5°C
Angle of Rotation at (Observed)
25°C ± 0.5°C

13.18 to 13.40

26.36 to 26.80

39.54 to 40.20

52.72 to 53.60

65.90 to 67.00


Popular posts from this blog

To determine loss on drying (LOD)

To determine loss on drying (LOD) Definition:   Loss on drying compares the weight of product sample before and after drying. The result is the percentage of moisture in a product. % Moisture = (Begging weight-Ending weight) X 100                         -----------------------------------------------                                    Begging weight  Loss on drying determine by two method which is given below: Method (1):   Weigh accurately a dry empty glass Petri dish. Put the sample (about 0.5 to 5 gm as par requirement, Its mean if sample having less wet take 5 g weight. If sample having more wet than take 0.5 g weight ) in dish and weigh. Note down the reading. Distribute the sample in Petri dish by gentle shaking. Place the loaded dish (without cover) in the drying chamber for two hours. Maintain the oven temperature 105 +/- 5 0 C.  After drying is completed, open the drying chamber, cover the dish and allow it to cool at room temp.  Keep it in the desiccator for 15

Analytical Method Validation

Analytical Method Validation   The validation is performance, demonstration of any procedure, process, equipment, material, activity or any system performance as expected under given set of condition. In the most basis form, validation is proving that the performance is as intended. When extended to an analytical procedure,depending upon the application, it means that the method works reproducibaly, when carry out by same or different persons, in same or different laboratories, using different reagents, different equipment, etc. The analyst normally tends to assume that if an analytical method or process performs reproducibility in an limited number of experiment, it will continue doing so forever, which is too optimistic to assume. The Benefits:   The biggest   advantage  of method validation is that it builds a degree of confidence, not only for the developer but also to the user. Although the validation exercise may appears costly and time consuming. It is results in expens

Handling of Laboratory Incidents

Handling of Laboratory Incidents What is Incident: Any unplanned or uncontrolled event in the form of non-compliance to the designed systems or procedures at any stage of testing, and storage of drug product due to system failure or equipment breakdown or manual error. A laboratory Incident is an event in the laboratory that occurs for two primary reasons either due to analyst error or instrument error. Few example of laboratory incidents: Use of expired reagents/working standard/reference standard System suitability fail. Improper peak shape or peak split. Relative retention time shift. Communication failure between software and hardware during analysis. Power failure during analysis.  Temperature of laboratory found out of acceptance criteria. Out of calibration instrument used for analysis. To be broken or damage part of instrument during analysis. Responsibilities of the Personnel in case of incidents: Analyst:   Reporting of an incident to Head Q