Determination of surfactant bio-sourced origin by isotope-ratio mass spectrometry.

Abstract

To develop more eco-friendly laundry detergents, renewable surfactants synthesized from vegetal sources are increasingly being used. In a more stringent regulation context, the determination of bio-sourced surfactant origin thus appears essential to assess the claims of detergent manufacturers. Radiocarbon determination, the standard method for the analysis of bio-sourced materials, is an expensive technique, so there is a need for a cheaper method. Here, the use of an elemental analyzer linked to isotope-ratio mass spectrometry (EA/IRMS) is evaluated as an alternative approach to the official method. The δ(18) O, δ(13) C and δ(2) H isotope-ratio values were determined to investigate the bio-sourced origin of surfactant raw materials and mixtures. A sample library of 26 commercial surfactants representative of detergent raw materials was first analyzed by EA/IRMS. The δ(18) O, δ(13) C and δ(2) H values allowed discrimination of synthetic and bio-sourced surfactants. Moreover, in this latter group, C4 plant-derived surfactants were distinguished by their δ(13) C values. Binary and ternary mixtures made of synthetic and bio-sourced surfactants were also analyzed and indicated a linear relationship between mixture isotope-ratio values and surfactant proportions. IRMS represents a viable alternative to radiocarbon determination for the evaluation of surfactant bio-sourced origin. It is a faster and cheaper technique, allowing discrimination of petroleum- and biomass-derived surfactants and identification of their carbon sources (C4 or C3 plants).