ASTM Industrial Test Methods for visual and instrumental APHA Color Scale

FAQ: “Does HunterLab have any documentation to show that the ColorQuest XE is compliant with ASTM 1209. One of our customers is having a problem regarding the method. Their client is using the manual visual method for performing the ASTM 1209 color test method whereas they use the ColorQuest XE. Can you explain the difference?” Continue reading

What are the Flow Cell Options for Transparent Liquids?

Flow Cell Diagram combo

HunterLab D04-1015-423 flow cell with 7 mm ID/9 mm OD inlet ports, centered in D02-1009-960 Flow Through Cell Holder

A flow through cell can be a handy solution for continuous sampling and ease of measurement with a transparent, liquid product. Continue reading

Source for the APHA/Pt-Co/Hazen Color Standards

These APHA/Pt-Co/Hazen liquid color standards were originally developed as references for visual APHA/Pt-Co/Hazen Color comparison to samples. Their role with instrumental APHA/Pt-Co/Hazen Color measurement is primarily as a performance qualification check of the instrument prior to measuring liquid product samples, or to validate the instrumental-to-visual correlation.

HunterLab instruments have their own internal diagnostic standards to verify instrument performance. Measurement verification on these liquid color standards serves as an application diagnostic, affirming that the instrument has been configured correctly and is reading APHA/Pt-Co/Hazen color in the range of the samples closely and consistently over time.

There are many suppliers of  APHA/Pt-Co/Hazen liquid color standards. Just make sure that their liquid color standards conform to ASTM D1209. Also some APHA/Pt-Co/Hazen color standards come in a small volumes sealed in glass intended for visual comparison purposes rather than instrumental measurement.

Typically a client orders a Platinum Cobalt 500 Color Standard and mixes it down to intermediate levels such as an APHA/Pt-Co/Hazen 30 that are close to the product color.

While there are other industry test methods that reference the Platinum Cobalt 500 Color Standard Solution, also known as APHA/Pt-Co/Hazen Color Standard, preparation of the liquid standard is best defined in ASTM D1209 Standard Test Method for Color of Clear Liquids (Platinum Cobalt Scale). Instruction for preparing intermediate APHA/Pt-Co/Hazen standards below 500 by dilution is found in ASTM D1209 Table 1. This method also provides advice on how best to perform visual comparisons to these liquid color standards.

Sources for Liquid APHA/Pt-Co/Hazen Color Standards

Ricca Chemical Company, Arlington, TX 76094 USA +817-461-5601 www.riccachemical.com can be ordered through Fisher Scientific www.fishersci.com with worldwide distribution (search under Analytical Reagents for “Color Standard APHA/Hazen” conforming to ASTM D1209).

RICCA manufactures the liquid APHA/Pt-Co/Hazen 500 Color Standard, as will also prepare the intermediate standards, and certify them. They also sell a liquid APHA/Pt-Co/Hazen 1000 Color Standard for rare cases where the product color exceeds 500.

Fluka Analytical of Sigma-Aldrich, St. Louis, MO 63178 USA with worldwide distribution www.sigmaaldrich.com (search on “APHA” or “Pt-Co”).

Fluka sells the 500 Color Standard along with sets (2 ml and 10ml) for 20 different intermediate APHA/Pt-Co/Hazen standards, sealed in vials and intended for visual comparison.

Paragon Scientific Ltd., Prenton, Wirral CH43 3DU, United Kingdom+44 (0)151 649 9955 www.paragon-sci.com

Paragon is a European supplier of APHA/Pt-Co/Hazen color standards (fixed 5, 10. 15, 30, 50, 100, 500 color standards only with certification). Please note that Paragon  offers an APHA/Pt-Co/Hazen color standard that represents 0. As this is just certified distilled water, purchase is not recommended.

Reagecon Diagnostics Limited, Shannon Free Zone, County Clare, Ireland +353 61 47 26 22 www.reagecon.com

Reagecon is a European supplier of APHA/Pt-Co/Hazen, Gardner, Saybolt and ASTM D1500 liquid color standards in accordance with ASTM D1209, ASTM D6166 and ASTM D6045 methods.

Hach UK, Salford M50 1DL UK +0161 872 1487 http://uk.hach.com  

Hach bought Dr. Lange (Germany) and with it got their LICO color measurement instruments that include measuring APHA/Pt-Co/Hazen and Gardner Color. Dr. Lange also had a side business of supplying liquid color standards for instrument performance qualification. Hach UK has picked this business up in Europe.

The ADDISTA Colour Set of 6 certified standard colour solutions for LICO (LZM282 consists of 3×50 ml APHA/Pt-Co/Hazen liquid color standards (levels of 20, 100, 200) and 3×50 ml Gardner liquid color standards (levels of 2, 5, 8).

Our EasyMatch QC software has a built-in 10 mm correlation for measuring both APHA/Pt-Co/Hazen and Gardner Color simultaneously on the same sample with the 10 mm cell path length filled with distilled water being APHA/Pt-Co/Hazen and Gardner = 0, representing no color.

 

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.

APHA = Pt-Co = Hazen = PCU = Platinum Cobalt Color

Bottles of APHA/Pt-Co/Hazen 500 color standard.

“APHA” stands for American Public Health Association Color Scale, the organization responsible for the original definition and implementation of this visual color scale as a standard method for rating water quality. Continue reading

What Path Length Cell should I use for APHA/Pt-Co/Hazen Color Measurement?

FAQ: ” We are currently using a 10 mm path length and read in the 0 – 50 region for APHA/Pt-Co/Hazen Color, usually in the area of 10. Would you recommend a 10 mm path length with our equipment for this application?” Continue reading