# Regulation (EC) No 648/2004 of the European Parliament and of the Council of 31 March 2004 on detergents (Text with EEA relevance), Division 4.4.4

Extent: E+W+S+N.I.

Connect the exchange columns so that the cation-exchange column is placed on top of the anion-exchange column.
Heat the exchange columns to 50 ° C using thermostatic control.
Heat 5 000 ml of the solution obtained in item 4.4.2 to 60 ° C and pass the solution through the exchanger combination at a rate of 20 ml/min. Wash the columns with 1 000 ml hot isopropanol/water mixture (4.3.3).
To obtain the anionic surface active agents (MBAS), disconnect the KAT column. Using 5 000 ml ethanol/CO2 solution at 50 ° C (4.3.4), elute the soap fatty acids out of the KAT column. Reject the eluate.
Then elute the MBAS out of the AAT column with 5 000 ml ammonium bicarbonate solution (4.3.5). Evaporate the eluate to dryness using a steam bath or in a rotary evaporator.
The residue contains the MBAS (as ammonium salt) and possible non-surfactant anionics that have no detrimental effect on the biodegradation test. Add deionised water to the residue until a definite volume is obtained and determine the MBAS content in an aliquot. The solution is used as a standard solution of the anionic synthetic detergents for the biodegradation test. The solution should be kept at a temperature below 5 ° C.
Regeneration of ion exchange resins

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Source: https://www.legislation.gov.uk/eur/2004/648/annex/VIII/division/4/division/4.4/division/4.4.4 (the official version)
Page: https://openlegislation.uk/eu-regulation-2004-648/annex-VIII/division-4/division-4.4/division-4.4.4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.