What tolerance should be used for a PQ Performance Qualification on Transmission Color Measurements?

FAQ: “What is the limit on the standardization in TTRAN.  Using the small sample flask, filled with Ultra pure water. If they follow the protocol, they expect to find values (CieLab: 100.0; 0.0; 0.0)?” Continue reading

Do you have a source for Transparent Liquid Haze Standards?

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?” Continue reading

What is a visual limit for Haze%?

FAQ: “What is a visual limit for Haze%? When should I be able to see a difference in a sample?”

A perfect clear of 0% would be air for transparent solids and the transmission cell of a defined path length filled with DI water for transparent liquids.

It should also be noted that the Haze% measurement of scatter in a sample is dependent on the thickness of transparent solid samples or cell path length of liquid samples.

The answer as to when you can see a visual difference will depend on the nature of the sample. For the plastic or glass sheets used in computer tablet screens, acceptable limits for what is faintly visible fall in the 1-2% range.

For pharmaceutical or chemical liquids, the average person may be able to see a visual difference in transmission haze at around 4 – 5%, and should definitely see a difference at a level of 6 – 7%.

To determine this for you sample, you should take a range of products exhibiting haze and get the consensus opinion of a number of people as to which samples show less than and more than visible sample. Measure Haze% using a sphere instrument and assign a visible limit specific to your product.

For many applications, especially those related to consumer products, a visible limit for haze is also the tolerance for acceptable product but not always…

Depending on the end use of the product, what is an acceptable may be below a visible limit if you don’t customer to see any visible haze difference in your product.

Or, if haze is inherent in the product and whatever is causing the product haze does not impact its use, an acceptable tolerance may be several times a visible difference. On these types of products, a typical range for good product might be from 10 to 12%, with an upper limit set at 20% just to ensure that any abnormal product is detected.

Air for transparent solids, or the cell filled with DI water or clear solvent for transparent liquids, is a physical product reference representing no haze, and the best your sample can be. A visible limit in product samples will typically be in the 2% to 5% range. What is acceptable in the marketplace will vary from less than a visible limit to some upper maximum.

Source for ASTM D1003 Transparent Plastic Haze Standards from HunterLab

You can order single Haze standards or the full set of 5 haze standards through HunterLab for use with any of our sphere instruments – ColorQuest XE, UltraScan PRO and UltraScan VIS. These solid, transparent plastic plaques (calibrated or uncalibrated) can be effective in monitoring instrument performance in measuring wide angle scattering over time.   Continue reading

How do I use the round Small Volume (4 ml) 10 mm Transmittance Cell?

HunterLab’s round cell (A13-1011-613) is a practical small volume cell for transmittance color and haze measurements. Continue reading

How do I measure “clear and colorless” Surfactants?

FAQ: “We are in touch with a pharmaceutical company which is looking for a spectrophotometer to measure the color and appearance of cationic surfactants. Can you provide any information on this topic?”

Surfactants reduce the surface tension of a liquid as in the use of a dish detergent; the interfacial tensions between two liquids such as in the case of an oil spill in water, or of laundry detergent removing soil from clothes in water.

Surfactants have two parts within a single molecular structure  – a hydrophilic (or water-loving) head and a hydrophobic (water-repellent or oil-loving) tail. The hydrophobic part is typically a long hydrocarbon chain of different types. The polar hydrophilic head group can be non-ionic (no-charge),  anionic (positive charge), cationic (negative charge) and zwitterionic (two opposite charges).

 In terms of color and appearance quality, transparent surfactants are often visually described in product specification sheets as “clear and colorless”, almost “water white”, without apparent visual haze. “Colorless” in measurement terms, means being a close as possible to distilled water with only trace yellowness. Being “clear” means being as close to distilled water as possible in not scattering light.

How to Measure Surfactants on HunterLab Sphere Instruments

  1.  Any of HunterLab’s diffuse d/8° sphere instruments such as ColorQuest XE, UltraScan VIS or UltraScan PRO are appropriate for this application. Additional required accessories are a  50 mm path length transmittance cell (13-8573-20 or 20 mm path length cell ( 04-4592-00) and a Transmittance Cell Holder (C02-1005-481).
  2. Configure the Color Data View in EasyMatch QC software to display:
    1. CIE L*, a*, b* D65/10° or C/2° as a full color descriptor. While these values are good to report, APHA and Haze% will be the two metrics best able to distinguish slight lot differences in very clear and colorless surfactants.
    2. APHA-50 mm [C/2°] or Yellowness Index YI E313 [C/2°] to quantify trace yellowness.Typical purchase specifications indicate a maximum APHA value of 5 to 30, with distilled water being 0.
    3. Haze% to measure trace scattering to indicate how “clear” the sample is. DI water will have 0% haze. A visual difference in haze can typically be seen around 4%.
    4. As an optional metric, Y Total Transmittance can be configured to quantify the total amount of light passing through the sample with DI water as a reference for 100% transmittance.
  3. Standardize any HunterLab sphere instrument in TTRAN (Total Transmittance) LAV (Large Area of View) mode using:
    1. The Light Blocker to set 0% transmittance.
    2. The 50-mm path length transmittance cell filled with DI water and the white calibrated tile at the reflectance port to set 100% transmittance.
  4. As a recommended PQ (Performance Qualification) step, leave the cell with DI water in place at the TTRAN port. Then measure DI water as a product standard. If the instrument is set up correctly, distilled water in the 50 mm cell should measure closely to CIE L* = 100.0, a* = 0.0, b* = 0.0; APHA = 0.0; YI E313 [C/2] = 0.0; Haze% = 0.0 and Y Total Transmittance = 100.0.
  5. As an optional Application Diagnostic step, a liquid APHA Color standard can be purchased with nominal values similar to the product specification (APHA 5, 10, 20 or 30), then measured for APHA 50-mm and Haze% on the first day to establish baseline values. The measured baseline APHA value should closely match the assigned APHA value for the standard. The baseline Haze% should be low, typically < 1%. Measurements of the APHA liquid color standard should match the baseline values closely over time to affirm that your instrument is consistent in measuring APHA Color and Haze%.
  6. Proceed to measure batch lots of surfactants and report APHA and Haze% to document process differences by lot and conformance to product color and appearance specifications.