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European Pharmacopoeia EP 10, Chapter 2.2.25

The latest version of the European Pharmacopoeia (EP 10), applied since 01 January 2020

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.

New requirements in EP 10, Chapter 2.2.25
The new EP 10-compliant control of the UV/Vis spectrophotometer depends on the intended spectral range (absorption and wavelength range). This means that the existing standard filter set can only be partially used to check the parameters. In general the existing filter set must be supplemented individually depending on the intended spectral range.

Important Statements in the new EP 10, Chapter 2.2.25
„.. quantitative measurements relying on absorbance values above 2.0 should be avoided“
„..all measurements are carried out with reference to the same solvent or the same mixture of solvents (blanks)."

Following parameters should be regularly controlled:
1. Wavelength accuracy
2. Absorbance accuracy
3. New: Photometric linearity
4. Limit of stray light
5. Resolution


New requirements of EP 10 Chapter 2.2.25

The changes in the new EP 10 compared to the previously valid EP 8 are briefly explained in the following context.

 

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

Material Wavelength (nm)
Cerium liquid filter 201, 211, 223 ,240, 254
Didymium liquid filter 512, 732, 794
Holmium liquid filter 241, 287, 361, 451, 485, 537, 640

 

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

Material Wavelength (nm)
Niacin liquid filter (5 - 45 mg/l) 213, 261
Neutral density glass filter 440, 465, 546.1, 590, 635

 

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

Material Wavelength (nm)
Niacin liquid filters (5 - 40 mg/l) 213, 261
Neutral density glass filters 440, 465, 546.1, 590, 635

 

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:

Filter / Solution Absorbance at Wavelength
Potassium chloride (12 g/L) ≥ 2.0 Abs at 198 nm
Sodium iodide (10 g/L) ≥ 3.0 Abs at 220 nm
Potassium iodide (10 g/L) ≥ 3.0 Abs at 250 nm
Sodium nitrite (50 g/L) ≥ 3.0 Abs at 340 and 370 nm

 

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

European Pharmacopoeia 10th Edition - EP10 (Folder EN)

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