05 January 2017
Appearance is paramount when it comes to public perception. If something does not look as it should, it will not be received in a positive manner which could be detrimental to suppliers and manufacturers, regardless of the product. Even the less publically acclaimed products are still subject to visual scrutiny, so why not solve a problem before it presents itself? Why not keep even the clearest of liquids up to an outstanding standard and keep the appearance of a product true to visual sensitivity?
What are EP, APHA, PtCo and Hazen Colour Scales?
“EP – European Pharmacopoeia Colour is a similar visual liquid colour scale used in the pharmaceutical industry. It consists of 3 primary colour standard solutions (yellow, red and blue) that are combined with hydrochloric acid to make 5 standard colour solutions – B (brown), BY (brownish-yellow), Y (yellow), GY (greenish-yellow) and R (red) that are subsequently diluted with hydrochloric acid (10 mg/l) to make 37 reference EP liquid colour standards – 9B, 7BY, 7Y, 7GY and 7R.”
APHA stands for American Public Health Association. This colour scale acts as a yellowness index, allowing for accurate measurements of transparent liquids. The APHA colour scale ranges from 0 (clean water) to 500 (distorted waste water). Each APHA unit is based on a dilution of the 500ppm stock solution of PtCo.
APHA Zero (0) standards are represented by distilled water for water based products, Toluene or Benzene for resins and Mineral oils for oils for the most accurate results that allow for a universal conformation.
The PtCo or Platinum Cobalt Colour Scale is equal to the APHA Colour Scale as they are both used predominately to measure the colour and quality of water. Both colour scales are based on standards made from chloroplatinate solutions, varying in parts per million of platinum cobalt to water.
The Hazen Colour Scale is again equal to the APHA and PtCo although can sometimes be referred to as Hazen Colour or 1500 Hazen Colour. If this is the case then the range is often goes above the 500 units associated with APHA.
APHA, PtCo and Hazen are all names of the same colour measurement scale.
EP Colour is short for European Pharmacopoeia colour.
What are their uses?
All products have certain visual tolerances that must be met; APHA/PtCo/Hazen Colour Scales (henceforth known as APHA Scales) are used for the measurements of chemicals, clear oils, petroleum spirits and many other clear liquids in the water, chemical, oil, plastics and pharmaceutical industries.
The USP and EP Color Standards are visual color standards, intended to improve color communication between sites by defining a sample color as being close to physical liquid standard (“near USP F”; “near EP Y2”) rather than using words. (“light yellow”).
These colour scales play an important role in a range of industries as they can quantify trace amounts of yellowness caused by exposure to light or heat, an error in processing or the presence of impurities.
The most pivotal to the public eye would be in the use of tap water. Water that is fed to houses should be clear and pure or water whit to a visual inspection. Even being slightly off colour would suggest contaminants that would cause complaints and even health scares. For water, the presence of a foreign colour could indicate substances such as bacteria, minerals, algae and fertilisers to name a few so it is vitally important that before being sent for use as tap water, final testing is done during the purification process to ensure that the water has an extremely low APHA unit value.
APHA Colour testing can also be done during smaller scale water testing such as if there is a problem with a particular area’s water supply and only a small cross section of the water supply needs to be tested to maintain quality and keep to regulations. APHA colour testing is ideal as the yellowness of a liquid is a clear indicator of a problem.
Even bottled water companies require testing to ensure their produce being sold meets all regulations and quality control standards. Who will buy bottled spring water with a yellow tinge?
APHA Scales can also be used alongside the ADMI Colour Index for the measurement of waste water. This can test the quality of the waste water after treatment to ensure there will be no harmful bacteria or chemicals contained in it before returning to the environment.
Aside from use in water based industries, the APHA scale is essential for quality control in a variety of chemical applications as well. The production of solvents is fundamental to a wide expanse of products. Organic and inorganic solvents are present in numerous products ranging from paint and ink to cleaning fluids and adhesives and so need to be of excelling standards from the start so not to alter the appearance of the finished product.
Pharmaceutical companies are looking for clarity and to prevent impurities.
All uses of the APHA Scale require an instrument or system that is capable of adapting to any liquid testing needs, including quick access to EP and APHA measurements for recognising problems quickly thus drastically cutting quality control process time and keeping consumers satisfied.
Machine Used and Application
For the measurement of a sample using the EP and APHA Scale, the HunterLab VISTA Spectrophotometers are ideal, offering a versatile range of functions.
The HunterLab VISTA is a specially designed transmittance measurement spectrophotometer that can take accurate measurements of a variety of transparent liquids. The VISTA comes equipped with the Hunter L, a, b and CIE L*, a*, b* colour scales in addition to the EP and APHA Scale to provide a range of useful functions.
Equally as beneficial is the HunterLab UltraScan VIS, this colour measurement spectrophotometer can measure the reflectance, transmittance or haze of samples using every viable colour measurement scale. The HunterLab UltraScan VIS is equipped with a large transmission compartment that opens on three sides to enable measurements of the transmittance of samples of varying sizes.
Both of these versatile instruments can take quick and accurate measurements of the transmitted colour of liquid samples for analysis using the EP and APHA Colour Scale. Any samples that are either more saturated with the yellow hue or are of a darker yellow or brown in colour can then be measured using the Gardner Colour scale, also available on these multipurpose instruments.
Both of these instruments offer a simple, easy to use solution to quality control, allowing industries an easy approach to keep to important regulations and maintain the highest standards conceivable. Ask us for a free method.