Procedures & Tools > SDA Nomenclature

SDA Nomenclature principles

In accordance with the Guidance for identification and naming of substances under REACH, UVCB substances either cannot be uniquely specified with the IUPAC name of the constituent, as not all the constituents can be identified; or they may be generically specified but with a lack of specificity due to variability of the exact composition. As such, as the chemical composition alone is not sufficient enough for substance identification, the substance shall in general be identified by its name, origin and the most relevant steps during processing. Such substances should be derived solely from the named source (e.g. soybean) and the process undergone by the substance must be indicated in the description (e.g. hydrogenation, interesterification, etc.). This is source-based nomenclature.

In connection with reporting to EINECS, the EINECS reporting rules guidance and the current ECHA Guidance both refer to a system, jointly developed by the U.S. Environmental Protection Agency (EPA) and Soaps & Detergent Association (SDA), for the naming of chemical substances derived from natural fats and oils and their synthetic substitutes. This is referred to as the SDA Nomenclature system and is described into detail in a guidance document, published by the US EPA (TSCA Addendum III, section 1), and in Appendix A, Volume I, of the 1985 printed edition of the Toxic Substances Control Act (TSCA) Chemical Substance Inventory.

This SDA system description of long-chain alkyl derivatives is based on:

  • an alkyl descriptor;
  • a functionality descriptor to identify the functional group(s) associated with an alkyl group;
  • and a salt descriptor to identify cations associated with the functional groups.

Specific guidance is provided in the original EINECS and TSCA documents on the most appropriate alkyl descriptor for a limited number of source derived alkyl groups.

These nomenclature rules allow a flexibility in the botanical source of substance named, whereas it is still sharp on the chemical composition of the substance, which offers the opportunity to describe a diversity of UVCBs in a convenient and relevant way for regulatory toxicology and biochemistry purposes. This offers the opportunity to bring more consistency in the registration approaches.

The original published reference documents providing guidance on the SDA Nomenclature are the following:

SDA Nomenclature approach as applied to oils, fats and certain derivatives

With regards to assessing the appropriate SDA nomenclature, the following two main general rules apply:

  • Use of the SDA nomenclature is predicated on selecting the narrowest alkyl distribution value (alkyl descriptor) which describes the predominant long-chain alkyl groups of the substance reported. In this context, the term “predominant” means that about 80-100 percent of all long-chain alkyl groups are included within the description.
  • As a practical consideration, alkyl group components that are present at less than two percent by weight need not be included in the SDA name.

In addition, the TSCA guidance also provides that for substances that only contain even chain lengths, only the possible even chain lengths are considered for the calculation of the extra and missing components. However, in case a substance contains only odd chain lengths or contains both even and odd chain lengths, the full range of even and odd chain lengths has to be considered for the purpose of calculating extra and missing components.

In situations where both the overall percentage covered and the total sum of extra and missing components are equal, the TSCA guidance provides that the alkyl descriptor providing a better technical description of the alkyl composition, i.e., the actual composition is nearer the centre of the range provided by the alkyl descriptor, shall be chosen.

Further documents and extended guidance on the use of SDA System for REACH purposes, developed and owned by the Consortium, are available to purchase upon request.

A worked example in which the SDA nomenclature approach is applied to a modified vegetable oil is available for download here.