New Numbering System for ICUMSA® Methods

In order to reduce difficulties with ICUMSA® Method numbering system, a modified system is introduced with the publication of the ICUMSA® Methods Book 2019:

Secondary ICUMSA® General Subject Numbers (see explanatory note on the next page) will be printed in a 
reduced font size in order to reduce their prominence. 
For example GS1 / 3 / 4 / 7 / 8 – 13 (2004) /will be published/printed as follows;

GS1 / 3 / 4 / 7 / 8 – 13 (2004)

All Buyers of the ICUMSA® Methods Book 2019 receive a version with Method numbers printed in this way. The new writing is used also on the internet on and (for ordering).

Buyers of the ICUMSA® Methods Book Supplement 2019 receive an introductory section with new Method numbering system in addition to the new and revised Methods. They can keep the Methods with the old numbering system in their Methods Book as long the respective Method is not replaced by a revised version.

In future, ICUMSA® Methods should be cited in statutes, specifications, contracts etc. as: 

GS1 – 13 (2004)

This citation method number is referred to as the Shortened Method Number. Any future change to the applicability or scope of a method, will not affect the Shortened Method Number for citation purposes. 

Other Examples:

Old NumberNew Number in Methods Book 2019Shortened Method Number
GS1/2/3/9‐1 (2011)GS1/2/3/9‐1 (2011)GS1-1(2011)
GS1/2/3/4/7/8/9‐23 (2009)GS1/2/3/4/7/8/9‐23 (2009)GS1-23(2009)

With the publication of the 2025 Methods Book in 2025, the Secondary General Subject Numbers will be removed from the ICUMSA® Methods Book. 
ICUMSA® Methods will be numbered using only the Shortened Method Number. 

In common with other standardised international methods of analysis, the Scope and Applicability of all ICUMSA® Methods are described in the respective clauses of methods. A reference table in the introductory section of the ICUMSA® Methods Book also indicates the applicability of methods, the ICUMSA® General Subject Number and the Secondary General Subject Numbers. The table also shows the status of the methods for the various ICUMSA® General Subjects. For that reason, when the transition is made to Shortened Method Numbers, the information currently contained within method numbers will still be available to users.

The advantage of this modification is that method numbers will no longer need to be modified. The year of publication will of course be amended and users of ICUMSA® methods are reminded that this component of a method number is important. Only the most recent versions of ICUMSA® methods are valid.

Explanatory note on ICUMSA® Method numbering system

New Numbers for GS1, GS2, GS3, GS4, GS5, GS6, GS7, GS8 and GS9