What does pesticide specific rotation represent?

The specific rotation of pesticides is a crucial physical constant that measures their optical activity. Its definition and significance are outlined below:

‌1. Definition and Measurement Method‌

Specific rotation refers to the measured optical rotation when polarized light passes through a 1 dm path length of a solution with a concentration of 1 g/mL of optically active substances, under specific wavelengths (typically the sodium D line at 589 nm) and temperatures. The formula is:
[α]=αc⋅L[α]=c⋅Lα​
Where:

αα: Observed optical rotation

cc: Solution concentration (g/mL)

LL: Optical path length (dm)

‌2. Core Significance‌

‌Optical Activity Characterization‌: Reflects the chirality (e.g., left-handed or right-handed) of pesticide molecules, serving as a key basis for determining their stereostructure.

‌Purity Control‌: A critical pharmacopeia indicator for verifying authenticity and assessing purity (e.g., differences in lactose specific rotation reflect varying pharmacopeia standards).

‌Quantitative Analysis‌: Indirectly determines pesticide content, widely used in quantitative detection of optically active components.

‌3. Differences from Optical Rotation‌

‌4. Influencing Factors‌

‌Temperature & Wavelength‌: Must be measured under pharmacopeia-specified conditions (e.g., 20°C, D-line light source).

‌Solvent & Concentration‌: Different solvents may alter specific rotation values, requiring standardized conditions.

The magnitude of specific rotation does not indicate superiority; it merely reflects differences in optical properties.

The STNY-105 pesticide specific rotation meter is designed and manufactured in accordance with the NYT 1860.18-2010 Guidelines for Testing the Physical and Chemical Properties of Pesticides Part 18: Specific Rotation Method. It is a specialized instrument for measuring the specific rotation of pesticides.

Specific optical rotation: The optical rotation measured by a specific wavelength of polarized light passing through a 1dm tube and a 1g/L liquid of light substance at a certain temperature T is called the specific optical rotation at that wavelength and temperature.