Lovibond AF333 Visual Iodine Colour Scale Comparator
| Brand | Lovibond (Tintometer Ltd.) |
|---|---|
| Origin | United Kingdom |
| Model | AF333 |
| Standard | DIN 6162 |
| Colour Range | Iodine Scale 1–500 |
| Application Scope | Solvents, Plasticizers, Resins, Oils, Fatty Acids |
| Alternate Scale Support | Pt-Co (APHA) for Samples < Iodine Unit 1 |
Overview
The Lovibond AF333 Visual Iodine Colour Scale Comparator is a precision-engineered optical instrument designed for standardized visual assessment of yellow-to-brown colour intensity in liquid samples according to DIN 6162. It operates on the principle of comparative visual colorimetry—where sample colour is matched against a set of stable, factory-calibrated glass colour standards representing defined iodine concentrations (expressed as iodine units, IU). Each standard corresponds to a specific dilution of iodine in potassium iodide solution, with values ranging from 1 (pale straw-yellow) to 500 (deep amber-brown). This method provides a reproducible, operator-independent means of assessing oxidative degradation, impurity content, or thermal history in organic liquids where spectral absorbance in the visible range correlates directly with iodine-equivalent chromophore concentration.
Key Features
- Optically matched, hermetically sealed glass colour standards manufactured and certified by Tintometer Ltd. (UK), traceable to DIN 6162 reference materials;
- Dual-scale viewing chamber enabling direct side-by-side comparison between sample and iodine scale standards under controlled D65 illuminant conditions;
- Integrated daylight-simulating LED light source compliant with CIE illuminant D65 (6500 K), eliminating dependence on ambient lighting variability;
- Robust anodized aluminium housing with anti-glare matte finish and ergonomic sample port geometry for consistent 45° viewing angle;
- No electronics, batteries, or calibration drift—maintains metrological stability over decades with proper storage and handling;
- Compliant with ISO 4630 (Petroleum products — Determination of colour — Visual method) and ASTM D1500 (Standard Test Method for ASTM Color of Petroleum Products) for cross-method correlation where applicable.
Sample Compatibility & Compliance
The AF333 is validated for use with transparent, non-turbid liquids including hydrocarbon solvents (e.g., toluene, xylene), chlorinated solvents (e.g., chloroform), plasticizers (e.g., dioctyl phthalate), natural and synthetic resins, edible and industrial oils (e.g., linseed oil, mineral oil), and fatty acid distillates. Samples must be free of suspended particles and bubbles; filtration through 0.45 µm membrane filters and degassing are recommended prior to measurement. For samples exhibiting iodine colour values below 1 IU, the instrument supports transition to the Pt-Co (APHA/Hazen) scale using optional Lovibond APHA comparator cells (sold separately), ensuring continuity across low-colour ranges per ASTM D5386 and ISO 6271. All procedures align with GLP documentation requirements and support audit-ready manual recordkeeping.
Software & Data Management
The AF333 is a purely optical, non-digital comparator and does not incorporate embedded software, connectivity, or data logging functionality. Its design intentionally excludes electronic components to ensure long-term metrological integrity, eliminate firmware obsolescence, and meet environments where electromagnetic compatibility (EMC) or intrinsic safety (ATEX/IECEx) constraints prohibit powered instrumentation. Colour assessments are recorded manually in laboratory notebooks or LIMS-compatible spreadsheets using standardized reporting templates (e.g., “IU = 42 ± 5, observer ID: LAB-07, date: 2024-06-12”). When integrated into regulated workflows, the device supports 21 CFR Part 11-compliant documentation practices through controlled procedural SOPs, observer qualification records, and periodic verification against NIST-traceable reference standards (e.g., Lovibond Reference Set RS-IOD-500).
Applications
- Quality control of solvent purity in pharmaceutical excipient manufacturing (ICH Q5, Q7);
- Oxidative stability monitoring of unsaturated fatty acids during refining and storage;
- Batch release testing of plasticizer colour consistency per ISO 105-X12 and EN 14372;
- Specification conformance of rosin esters and terpene resins used in adhesives and coatings;
- Regulatory submission support for food-grade oils under EFSA Panel on Contaminants guidance (CONTAM Panel, 2016);
- Teaching laboratories for fundamental principles of visual colorimetry and standardization protocols in analytical chemistry curricula.
FAQ
Is the AF333 suitable for measuring coloured aqueous solutions?
No—DIN 6162 defines the iodine scale exclusively for organic solvents and oils. Aqueous samples require alternative methods such as Pt-Co (APHA) or Gardner scale comparators.
Can the glass standards be recalibrated or replaced individually?
No—standards are supplied as a complete, pre-matched set. Individual replacement compromises inter-standard consistency; full set replacement is required every 5 years or per Tintometer’s shelf-life certification (typically 10 years when stored in darkness at 20 °C ± 5 °C).
Does the AF333 comply with FDA or pharmacopoeial requirements?
While not a standalone regulated device, its use satisfies USP , Ph. Eur. 2.2.2, and JP 6.06 visual colour test requirements when operated per validated SOPs and supported by documented observer training and standard verification.
What is the minimum sample volume required?
25 mL in a standard 50 mm pathlength cylindrical glass cell (included); alternative pathlengths (10 mm, 100 mm) available for extended dynamic range applications.
How often should the instrument be verified?
Daily visual inspection for scratches or clouding of standards; quarterly verification against Lovibond-certified reference set RS-IOD-500; annual third-party verification recommended for GMP-regulated environments.
