Coceth sulfate characterization by electrospray ionization tandem mass spectrometry

Area of Science:

• Analytical Chemistry
• Surfactant Science

Background:

• Alkyl ether sulfates (AESs) are widely used anionic surfactants in cleaning products.
• Coceth sulfate (CES) is a common AES derived from coconut oil fatty acids.
• Detailed structural information on CES, particularly alkyl chain length and ethoxylation degree, is lacking.

Purpose of the Study:

• To characterize the molecular structure of coceth sulfate (CES).
• To determine the distribution of alkyl chain lengths and ethylene oxide units in CES.
• To enable CES identification in commercial cleaning products.

Main Methods:

• Tandem mass spectrometry (MS/MS) with direct injection electrospray ionization (ESI).
• Analysis using a linear quadrupole ion trap mass spectrometer.

Main Results:

• Two series of CES oligomers with C12 and C14 alkyl chains were identified.
• The degree of ethoxylation (n) ranged from 0 to 7 for both alkyl chain lengths.
• CES was successfully identified in three commercial dishwasher detergents.

Conclusions:

• Direct injection MS/MS provides a well-defined molecular weight distribution for CES.
• The method accurately identifies alkyl chain composition and the number of ethylene oxide units in CES.
• This characterization is valuable for quality control and identification of CES in consumer products.