The relevant EP 10 chapter, 2.2.25 Absorption spectrophotometry Ultraviolet and Visible, has undergone a comprehensive revision in the latest version. Amongst other things, for the purpose of absorbance accuracy, Nicotinic acid has been introduced as an alternative to potassium dichromate which is listed in Annex XIV of the REACH regulations.

1. CONTROL OF WAVELENGTH ACCURACY

Old EP 8:
Holmium liquid filter is used to check wavelength accuracy from 240 nm to 650 nm

New EP 10:
.. requires to control the wavelength accuracy of an appropriate number of bands in the intended spectral range using one or more reference materials. It is recommended to test at least 2 wavelengths that bracket the intended spectral range!

Following reference materials (filters) are suggested:
- Holmium liquid filter for spectral range from 240 nm to 640 nm
- Didymium liquid filter for spectral range above 640 nm
- Cerium liquid filter for spectral range below 240 nm

Here you can find more information about Wavelength Filters.

2. CONTROL OF ABSORBANCE ACCURACY

Old EP 8:
UV range: Potassium dichromate solution with 60 mg/l is used.
Vis range: Potassium dichromate solution with 600 mg/l is used.

New EP 10:
.. requires the control of the absorbance accuracy at an appropriate number of wavelengths in the intended spectral range using solid or liquid filters. As a minimum, values at approx. the two limits of expected absorbance range should be verified

Following reference materials (filters) are suggested:
UV range: Nicotinic acid solution (Niacin) up to 2.0 Abs (5 - 45 mg/l)
Vis range: Neutral density glass filters up to 2.0 Abs

Note:
The use of potassium dichromate filters to check the absorbance accuracy in the UV range is still possible.

Here you can find more information about Absorbance Filters.

3. CONTROL OF PHOTOMETRIC LINEARITY

Old EP 8:
Not required.

New EP 10:
.. requires the control of the photometric linearity in the intended spectral range.

Following reference materials (filters) are suggested:
UV range: Nicotinic acid solution (Niacin)
Vis range: Neutral density glass filters

Note:
To check the photometric linearity, at least 3 filters with different concentrations are required per spectral range.

Here you can find more information about Photometric Linearity.

4. LIMIT OF STRAY LIGHT

Old EP 8:
.. requires the control of stray light with potassium chloride in H2O, the absorbance at 198 nm must be at least 2.0.

New EP 10:
.. requires the control of stray light at a suitable wavelength, the acceptance criterion depends on the filter used, see table.

Following reference materials (filters) are suggested:

Here you can find more information about Stray Light Filters.

5. CONTROL OF RESOLUTION

Old EP 8:
.. .requires the control of resolution with toluene in hexane.

New EP 10:
.. ..requires the control of resolution with toluene in hexane and using hexane as the reference solution.

Following reference materials (filters) are suggested:
Toluene in hexane and reference solution hexane.

Here you can find more information about Control of Resolution.