OIML R 139
Definition
International Organisation of Legal Metrology Recommendation R 139 (2014) governing metrological requirements for polarimeters used in official testing; specifies maximum permissible error of ±0.05° rotation for instruments in customs, food safety, and pharmacopoeia compliance applications.
- Issuer
- International Organisation of Legal Metrology (OIML)
- Year
- 2014
- Instrument covered
- Polarimeters used in official testing
- Maximum permissible error
- ±0.05° rotation
Common questions
Why does a legal metrology standard matter for forensic polarimetry?+
Laboratories that report optical rotation values for regulatory purposes, such as sugar content in customs or food testing, must show their instrument meets a recognized accuracy standard for the result to hold up under challenge.
How does R 139 differ from a laboratory's own calibration procedure?+
R 139 sets the metrological performance limit an instrument must meet for official use, while the laboratory's calibration procedure is the internal process it follows to verify and document that the instrument still meets that limit.
Related terms
- Biot Equation
- The fundamental equation of polarimetry: [α]_T^λ = α / (c × l), relating observed rotation to specific rotation, concentration, and path length;...
- Chirality
- The property of a molecule that cannot be superimposed on its mirror image; a chiral molecule and its mirror image are enantiomers...
- Dextrorotatory (+)
- Rotating the plane of polarisation clockwise (to the right) as seen facing the light source; designated (+) or d-; the d-methamphetamine and...
- Enantiomeric Excess (Ee)
- A measure of chiral purity: ee (%) = (R - S)/(R + S) x 100, where R and S are the measured...
- Enantiomers
- Two molecules that are non-superimposable mirror images of each other; they have identical physical properties (melting point, boiling point, solubility) except for...
- Invert Sugar
- The equimolar mixture of glucose and fructose produced by hydrolysis (inversion) of sucrose; laevorotatory overall because fructose's negative rotation exceeds glucose's positive...
- Laevorotatory (-)
- Rotating the plane of polarisation anticlockwise (to the left) as seen facing the light source; designated (-) or l-; l-methamphetamine and natural...
- Laurent Half-Shade Polarimeter
- A classical polarimeter design that uses a half-wave plate covering half the aperture to create two adjacent half-fields; the null point (equal...
- Optical Rotation (α)
- The angle in degrees through which a chiral solution rotates the plane of polarisation of a plane-polarised light beam; measured by rotating...
- Saccharimeter
- A polarimeter calibrated in International Sugar Degrees (°Z) rather than angular degrees; used in the sugar industry for purity determination under the...
- Specific Optical Rotation ([α])
- The standardised optical rotation of a substance at a defined temperature and wavelength, calculated from the Biot equation: [α] = α /...