FAQ: “I need to confirm that the HunterLab color instrumentation used in our product development laboratory complies with the USP 1061. We use the HunterLab Color Quest XE and EasyMatch QC Software (ver 4.82). We use the ASTM D1925 method for quantifying yellowness.
The USP chapter 1061 states: 'Determine the reflectance/transmittance from 380 to 770 nm at intervals of 10 nm.'
Is this wavelength range used in our instrumentation?”
USP 38 Monograph 1061 Color – Instrumental Measurement
USP - United States Pharmacopoeia Inc., Rockville, MD USA www.usp.org
There are 2 United States Pharmacopoeia monographs that address color (631) and color measurement (1061). 1061 describes the CIE system of color measurement and 631 references the visual USP liquid color standards and Munsell color standards.
This USP 1061 method on color measurement, while generally well written, is dated and not perfectly consistent with more updated CIE, ASTM, ISO and JIS methods.
Today the CIE references a colorimetric spectrophotometers having a full visible wavelength range of 360 nm to 780 nm with a recommended reported wavelength interval of 10 nm, or smaller – 5 nm and 1 nm intervals are fine as well.
The UltraScan PRO exceeds this with a spectral wavelength range of 350 nm to 1050 nm, and a reporting interval of 5 nm or 10 nm. The UltraScan VIS has a wavelength range of the full CIE range of 360 nm to 780 nm, and a reporting interval of 10 nm.
The ColorQuest XE has spectral range of 400 nm to 700 nm, and a reporting interval of 10 nm. The CIE (Commission internationale de l´éclairage Publication 15:2004), world governing body of light and color measurement, allows an instrument a truncated range of 400 – 700 nm to be used instead of the full 360 nm to 780 nm range. The reason for this is that the illuminant/observer tables which condition the spectral reflectance or transmission are almost zero below 400 nm and above 700 nm. For purposes of calculation of CIE X, Y, Z tristimulus values, HunterLab follows procedure 188.8.131.52 of ASTM E308 which is the recommended way of dealing with wavelength ranges shorter than 360 nm to 780 nm without any significant loss in the color value calculation.