EP colorimetry and color measurement according to GMP and FDA
In the production and development of biopharmaceutical products, the focus is on reliable solutions for determining the EP Colour number according to Ph. Eur. 2.2.2 instructed. With special technical solutions from HunterLab, the color of liquid samples (even in very small quantities) is examined with the greatest accuracy.
In order to check the product quality of yellowish, almost colorless liquid samples, 37 comparative solutions of the EP color number were specially developed. These are used to determine the color quality of liquid pharmaceutical products, concentrated liquid proteins or any liquid that tends to turn yellow due to its starting materials or during the process. Their value is therefore an indicator of the ageing or effectiveness of medicinal substances.
In many companies, visual comparison with the EP colour standards is still used to characterize the colour of liquid drug solutions. However, this visual method is very subjective, depends on the employee carrying out the comparison and is difficult to validate and document.
However, the process can be very easily replaced by a measurement technique using the Vista color measurement device. HunterLab devices can measure and display color in the three-dimensional L*, a*, b* color space. Target color values and color standards that meet the strict requirements of the European Pharmacopoeia are integrated directly into the software.
Color measurement in accordance with 21 CFR Part 11 is also possible with HunterLab color measurement devices. This means that the requirements of the FDA can be complied with by means of electronic records (logs) and signatures.
Read more about color measurement of very small quantities, EP color number and validation & compliance in our current HunterLab NEWS issue or everything about FDA-compliant color measurement according to 21 CFR Part 11 in our new whitepaper!
However, the process can be very easily replaced by a measurement technique using the Vista color measurement device. HunterLab devices can measure and display color in the three-dimensional L*, a*, b* color space. Target color values and color standards that meet the strict requirements of the European Pharmacopoeia are integrated directly into the software.
Color measurement in accordance with 21 CFR Part 11 is also possible with HunterLab color measurement devices. This means that the requirements of the FDA can be complied with by means of electronic records (logs) and signatures.
Read more about color measurement of very small quantities, EP color number and validation & compliance in our current HunterLab NEWS issue or everything about FDA-compliant color measurement according to 21 CFR Part 11 in our new whitepaper!
Whitepaper: “Color Measurement FDA-compliant”:
Read all about validation & compliance in color measurement in our latest white paper and how to reliably measure very small, liquid sample quantities and what to look out for in terms of sample handling in our HunterLab NEWS magazine.
Please fill in the two fields below and you can immediately read the PDFs!
Frequently asked questions about EP color number determination:
What is the EP color number?
The EP color number is a colour scale defined in the European Pharmacopoeia (Ph. Eur.) for the assessment of liquids, especially in the pharmaceutical and chemical industries. It is originally based on a visual comparison with standardized reference solutions and is used for the qualitative classification of colour intensities in the yellowish-brown range.
Why is the visual determination of the EP color number problematic?
The visual assessment depends on individual factors such as color perception, fatigue, lighting and environmental influences. This can lead to deviations between inspectors or locations. For regulated environments with high demands on reproducibility and documentation, this subjectivity is critical.
How can the EP color number be determined instrumentally?
A spectrophotometer is used to measure the transmission or reflection behavior of the sample in the visible spectral range. The recorded spectral data is converted into CIE Lab* values and compared with digitally stored EP reference values. This ensures that the classification is objective and reproducible.
Which illuminant should be used for EP color measurement?
What role does the cuvette length play in the EP color number?
The optical path length directly influences the measured color intensity (Lambert-Beer’s law). Typical cuvette lengths are 10 mm, 50 mm or 100 mm. For reproducible results, the path length must be standardized and documented.
Is the instrumental determination of the EP color number GMP-compliant?
Yes, provided the spectrophotometer used has suitable functions, e.g:
- Calibration with traceable standards
- User administration
- Audit trail
- Electronic data backup
This means that the measurement can be fully integrated into a GMP and 21 CFR Part 11-compliant quality system.
Can instrumental measurement completely replace the visual method?
In many applications, yes. The instrumental method significantly reduces subjective influences and increases comparability between locations. In regulated environments, it is increasingly being used as the preferred method or at least as a supplement to the visual test.
What are the advantages of instrumental EP shade determination?
- Higher reproducibility
- Objective basis for decision-making
- Faster batch release
- Fewer complaints
- Global comparability
- Complete documentation for audits
- Conformity to standards
How is the EP color number determined for turbid or fluorescent samples?
Cloudy samples can cause scattered light, fluorescent substances react sensitively to UV components of the light source. In such cases, a precise definition of the measurement parameters – including a controlled UV component – is required. If necessary, special Measuring modes, or adapted sample preparations (e.g. filtration) appliedcan be applied.
Why is the EP color number an important quality parameter?
Color deviations can indicate oxidation, impurities, aging processes or process deviations. The EP color number is therefore not only used for visual classification, but is also a sensitive indicator of product quality and process stability.