Specific optical rotation

Dear all,

While doing the SOR for liquid samples what is the concentration to be entered in sample concentraion option. Weight is not mentioned in procedure. Direct as such liquid sample using.

The specific optical rotation of a liquid substance is the angle of rotation measured as specified in the monograph, calculated with reference to a layer 100 mm (1 decimeter) thick, and divided by the relative density (specific gravity) measured at the temperature at which the rotation is measured.

The specific optical rotation of a solid is the angle of rotation measured as specified in the monograph and calculated with reference to a layer 100 mm thick of a solution containing 1 g of the substance per mL.

where a is the observed rotation, l is the length of the observed layer in mm, c is the number of g of substance contained in 100 mL of solution, d is the relative density, and p is the number of g of substance contained in 100 g of solution.

Reference- The International Pharmacopoeia, 10th Edition, 2020
1.4 Determination of optical rotation and specific rotation

can you provide liquid samples name ?

Essential oils consist of many different compounds that are mostly optically active. Their varying composition allows for them to be characterized by measuring the optical rotation. These measurements can also provide insight into essential oils’ quality and purity, as any change in their optimal composition will affect the optical rotation.
International pharmacopeias, such as the US and the European pharmacopeias, demand the determination of the optical rotation of a variety of essential oils, generally at 25 °C and 20 °C, respectively.

Examples:-

Orange oil- Angular (Optical) Rotation is +94 to +99 as per USP/NF
Lemon oil - Angular (Optical) rotation is +57.0 to +65.6 as per USP/NF