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 would be the plastic plaque standards used to monitor ASTM D1003 transmission haze. These plaques are more dimensionally stable than liquid turbidity standards that are also used to rate and quantify the degree of scattering.
As a workaround for a liquid scattering standard, there are liquid turbidity standards that could to verify measurement consistency of transmission haze in liquids over time.
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 version is more stable and homogenous.
Liquid turbidity standards can be obtained from:
Loveland, CO 80538 USA
DC Scientific Glass, Inc.
Glen Burnie, Maryland 2106 USA
Method for Measuring Turbidty Liquids as Liquid Haze Standards.
- Standardize the sphere instrument on the transmission cell filled with DI or HLPC water in TTRAN LAV mode.
- As a PQ Performance Qualification check, measure the cell with solvent back without moving the cell with the measurement expected to be Haze% = 0, Y Total Transmission = 100 expected.
- As an additional and optional PQ check, measure one or more liquid turbidity standards in the same cell and compare to baseline values read on the first day. The expectation is that these turbidity liquids will read closely to the baseline values over time.
- Report and trend chart the Haze results of your PQ checks over time.
- Proceed to measure the Haze of normal samples.
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) www.pheur.org