HunterLab Distributor FAQ: “I have a new pharma customer doing color measurements. They also want to do haze measurements and we had a discussion about haze standards. Would our plastic haze standards be fine or is there a liquid haze standard out there?
”It depends on the intended purpose of your customer. If your customer is looking to verify their instrument performance over time, the best option is the plastic plaque standards used to monitor ASTM D1003. These plaques are more dimensionally stable than liquid turbidity standards that are also used to rate and quantify the degree of scattering.
Given that these liquid turbidity standards that were originally as visual standards to estimate the degree of scattering, they are sufficiently stable to use as a check standard over time that is similar in nature to liquid products. There are two types of physical liquid standards for visual turbidity or opalescence – Formazin solution (with or without stabilizer) and polymer beads (polystyrene micro spheres). The Formazin solution is the historical liquid scattering standard but the polymer beads are more stable and homogenous.
Industrial Test Methods and References for Liquid Turbidity or Opalescence Standards
EP 2.2 Physical and Physico-Chemical Methods for color and opalescence describes the visual evaluation of scattering or opalescence in near clear pharmaceutical liquids relative to distilled water.
EP – European Pharmacopoeia, Section 2.2 Physical and Physico-Chemical Methods, Unit European Pharmacopeia, Strasbourg, France (1997: 15-16) http://www.pheur.org
Sources of Liquid Turbidity Standards
Loveland, CO 80538 USA
DC Scientific Glass, Inc.
Glen Burnie, Maryland 2106 USA
Method for Measuring Turbidity Liquids as Liquid Haze Standards.
- Standardize the sphere instrument on the transmittance cell with Distilled or HLPC water in Total Transmittance (TTRAN) LAV mode.
- As a Performance Qualification check measure the cell with solvent back without moving with the measurement expected to be Haze% = 0, Y Total Transmittance = 100 expected.
- Measure the liquid turbidity standards in the same cell as an additional PQ check.
- Report and trend chart the Haze results of your PQ checks over time.
- Proceed to measure the Haze of normal samples.
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