Lovibond AF328 Visual Platinum-Cobalt Colorimeter
| Brand | Lovibond (Tintometer Ltd.) |
|---|---|
| Origin | United Kingdom |
| Model | AF328 |
| Measuring Range | 0–70 mg Pt/L (Platinum-Cobalt Units) |
| Cell Path Length | 250 mm |
| Standard Discs | CAA (0–30 APHA), CAB (30–70 APHA) |
| Compliant Standards | ASTM D1209, ISO 2211, ISO 6271, AOCS Td 1b-64, BS 5339 |
Overview
The Lovibond AF328 Visual Platinum-Cobalt Colorimeter is a precision optical instrument engineered for the visual assessment of color in transparent, lightly yellow liquids using the internationally recognized Platinum-Cobalt (Pt-Co) scale—also widely referenced as the APHA (American Public Health Association) color scale. Based on the classical Hazen method first described in 1892, the AF328 operates on the principle of direct visual comparison between a sample and standardized Pt-Co reference solutions contained in matched glass Nessler tubes. This gravimetrically prepared standard series—comprising platinum chloride and cobaltous chloride in hydrochloric acid—provides traceable, stable color references calibrated to concentrations from 0 (water-white) to 500 APHA units. The AF328 employs a 250 mm path length cell geometry, optimized for enhanced sensitivity in the low-to-mid range (0–70 APHA), making it particularly suitable for high-purity water, pharmaceutical excipients, glycerin, solvents, plasticizers, and refined petrochemical intermediates where subtle color deviations indicate oxidation, degradation, or contamination.
Key Features
- Fixed 250 mm optical path length designed for improved resolution and repeatability in the 0–70 APHA range
- Dual-scale Nessleriser disc system: CAA (0–30 APHA) and CAB (30–70 APHA), each manufactured to strict Lovibond tolerance specifications (±1 APHA unit)
- Integrated light diffuser and collimated viewing aperture to minimize glare and ensure consistent illumination geometry per ASTM D1209 requirements
- Robust anodized aluminum housing with anti-reflective black interior finish to eliminate stray light interference
- Calibration traceability supported by Lovibond’s UKAS-accredited reference standards and documented uncertainty budgets
- No electronics or software dependency—fully manual, operator-independent methodology compliant with GLP environments requiring audit-trail-free visual analysis
Sample Compatibility & Compliance
The AF328 is validated for use with clear, non-turbid, non-fluorescent liquid samples exhibiting minimal suspended solids and low absorbance outside the visible spectrum (400–700 nm). It is routinely applied in QC laboratories for purified water (USP , EP 2.2.43), glycerol (USP ), ethylene glycol, chlorinated solvents (e.g., carbon tetrachloride), and food-grade alcohols. Its measurement protocol satisfies regulatory expectations under FDA 21 CFR Part 11 for manual analytical methods when accompanied by controlled SOPs and trained operator qualification records. All performance claims are substantiated against ISO/IEC 17025-accredited interlaboratory studies conducted by Tintometer Ltd. in accordance with ISO 6271 and ASTM D1209 revision protocols.
Software & Data Management
The AF328 is a purely optical, non-digital instrument and does not incorporate embedded firmware, data logging, or connectivity interfaces. As such, it requires no software installation, validation, or cybersecurity controls. Results are recorded manually in laboratory notebooks or LIMS-compatible forms. For laboratories operating under 21 CFR Part 11 or EU Annex 11, the AF328 supports fully paper-based or hybrid electronic record workflows—provided that observation entries include analyst ID, date/time, sample ID, observed scale value (CAA or CAB), and environmental conditions (e.g., ambient lighting class per ISO 8255-1). Traceability is maintained via physical retention of Nessler tubes and calibration discs, with lot-specific certificates supplied with each disc set.
Applications
- Pharmaceutical water systems: USP Purified Water and Water for Injection (WFI) color verification
- Petrochemical QA: Color grading of white mineral oils, naphthas, and halogenated solvents per ASTM D1209
- Food & feed additives: Glycerin (E422), propylene glycol, and polyethylene glycols per AOCS Td 1b-64
- Chemical manufacturing: Monitoring oxidative stability of plasticizers (e.g., dioctyl phthalate) and monomers
- Environmental labs: APHA-compliant wastewater effluent screening where instrumental colorimeters may overestimate due to turbidity interference
- Academic teaching labs: Demonstrating classical colorimetry principles without spectral complexity
FAQ
Is the AF328 compliant with current pharmacopoeial requirements for color testing?
Yes—the AF328 fulfills USP , EP 2.2.43, and JP 2.05 criteria for visual Pt-Co comparison methods, provided operators follow documented procedures and maintain calibrated reference discs.
Can the AF328 be used for samples above 70 APHA?
No—the AF328 is specifically configured for 0–70 APHA. Samples exceeding 70 require dilution or use of the AF329 (0–250 APHA) with dual Nessleriser compatibility.
How often must the CAA/CAB discs be replaced?
Lovibond recommends disc replacement every 24 months under normal storage (dark, dry, room temperature) and usage (≤10 observations/day); certificates of conformance include expiration dates based on accelerated aging studies.
Does the AF328 require annual recalibration?
No—calibration is intrinsic to the physical disc geometry and Pt-Co solution stability; however, periodic verification against a certified reference standard (e.g., Lovibond Reference Set RS-APHA) is recommended every 6 months per ISO/IEC 17025 Clause 6.6.
Is training required to operate the AF328?
Yes—per ISO 17025 and GLP, operators must undergo documented competency assessment including side-by-side comparison trials against a qualified assessor before independent use.
