Common Types Of Chemical Identifiers

Chemical identifiers are distinct codes or symbols used to represent chemical compounds. They enable accurate differentiation and identification of specific substances in scientific research, industrial applications and regulatory frameworks.

Figure 1. CAS Information on Caffeine [1]

Chemical Nomenclature:

Chemical names are assigned to compounds according to prescribed nomenclature rules, for instance IUPAC names or common names.

IUPAC Names:

The IUPAC system, which stands for International Union of Pure and Applied Chemistry, typically assigns names based on a compound’s molecular structure. It considers the types and arrangement of atoms. For example, Ethanol is the IUPAC name for the alcohol in beverages. 2-Methylpropan is the IUPAC name for a branched hydrocarbon with four carbon atoms.

IUPAC names for chemical compounds can be retrieved from online databases such as PubChem or ChemSpider. Authoritative chemistry textbooks, journals and mobile applications also provide access to IUPAC names.

Chemical Formulas:

Chemical formulas are symbolic representations that indicate the types and quantities of atoms in a molecule. For example, H2O represents water with two hydrogen atoms and one oxygen atom.

CAS Numbers:

CAS registry numbers (Chemical Abstracts Service) are unique numerical designations used to categorise chemical compounds. Each number comprises up to 10 digits separated by hyphens into three parts. The CAS registry contains records for substances such as elements, isotopes, metals, alloys and polymers.

Access to CAS registry numbers is available via sources and databases such as CAS SciFinder-n and CAS STNext. SAM and other chemical suppliers typically list CAS numbers alongside product details. CAS numbers are also provided on safety data sheets (SDS) and chemical labels.

InChI Codes:

InChI codes (International Chemical Identifier Codes) are unique textual representations of the structural information pertaining to chemical compounds. They serve as a standard method to represent molecular structure and bonding details in a format that is both human-readable and computer-interpretable.

InChI codes consist of a string that depicts connectivity, stereochemistry and isotopic details. They facilitate the exchange and retrieval of chemical data in databases and scientific publications, thereby ensuring accurate representation and identification of compounds.

SMILES:

SMILES stands for Simplified Molecular Input Line Entry System. It is a string-based notation used to represent the structure of chemical compounds using ASCII characters. SMILES notations convey information regarding atom connectivity as well as spatial arrangement and bonding. This system provides a compact, human-readable representation of complex molecular structures.

Unique Ingredient Identifier (UNII):

The Unique Ingredient Identifier (UNII) is a non-proprietary, unique alphanumeric code assigned to substances in the FDA Substance Registration System. UNIIs facilitate accurate identification of substances in approval applications, databases and various health-related information systems. Each UNII serves as a unique identifier that enhances accuracy and efficiency in the classification and referencing of chemical ingredients in pharmaceuticals, food additives, cosmetics and other FDA-regulated products.

Reference:

[1] CAS Registry Number. (2023, 12/10/2023). In Wikipedia. https://en.wikipedia.org/wiki/CAS_Registry_Number