HunterLab EasyMatch QC, User Manual

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EasyMatch QC User’s Manual Version 2.1
A-16 Measurement Values
APHA-10, -20, and -50 mm (ColorQuest II Sphere, ColorQuest XE,
ColorQuest XT, UltraScan PRO, UltraScan XE, and UltraScan VIS only)
The American Public Health Association (APHA) Index was developed in the 1890s as a visual
indicator of the purity of wastewater, where color is due to the presence of naturally-occurring organic
materials such as leaves, bark, roots, humus, and peat. Today, APHA is used as a metric for purity in
the chemical, oil, plastics, and pharmaceutical industries. This scale serves to quantify the appearance
of yellowness, a visual indicator of product degradation due to light and/or heat, the presence of
impurities, and the effects of processing.
APHA-10, -20, and -50 mm are designed to yield APHA/PtCo values that closely correlate to
APHA/PtCo standard solution values as defined by ASTM D1209. They are calculated from the YI
E313 yellowness index and are optimized for each instrument. This index is calculated only for the C/2°
illuminant/observer combination.
A transmission cell with 10-, 20-, or 50-mm path length is required for this metric.
To measure APHA Color, follow the steps below:
1. Configure your Color Data Table to include APHA-10, -20, or -50 mm as an index for display.
2. Standardize the sensor in TTRAN (total transmittance) mode on a clear liquid (distilled water is
suggested for water-based samples, toluene or benzene for resins, and mineral oil for oils) in a cell of
the desired size. Place the cell in the transmission compartment as close to the sphere as possible.
When APHA is in the Color Data Table and the instrument is not a ColorQuest II Sphere, the
instrument flashes three times for each reading in the standardization sequence.
3. Place the white calibrated tile at the reflectance port and leave it there for the APHA measurements.
4. Read the standards and/or samples in a cell of the desired size. Place the sample cell in the
transmission compartment as close to the sphere as possible. The APHA value will appear in your
displays and on your printouts. When APHA is in the Color Data Table and the instrument is not a
ColorQuest II Sphere, the instrument flashes three times for each reading.
APHA Difference is also available, and is defined as follows:
dAPHA-10 mm = (APHA-10 mm)
sample
- (APHA-10 mm)
standard,
dAPHA-20 mm = (dAPHA-20 mm)
sample
- (dAPHA-20 mm)
standard.
and
dAPHA-50 mm = (dAPHA-50 mm)
sample
- (dAPHA-50 mm)
standard.
ASBC-10 mm (ColorQuest XE, ColorQuest XT, ColorQuest II Sphere,
UltraScan XE, UltraScan PRO, and UltraScan VIS only)
The American Society of Brewing Chemists (ASBC) scale is used in the measurement of the color of
beer, malt worts, caramel solutions, and similarly-colored liquids. This transmission scale, which should
be measured using a cell path length of 10 mm, is based on the EBC scale, which is described later in