Characterization of Mixtures of Alkyl Polyglycosides (Plantacare) by Liquid Chromatography-Electrospray Ionization Quadrupole Time-of-Flight Mass Spectrometry

Abstract

Industrial products of alkyl polyglycosides (APGs) are widely used as well tolerated surfactants in washing and cleaning agents. APGs belong to the class of nonionic surfactants and are mixtures of molecules consisting of a hydrocarbon chain with Y carbon atoms linked to X sugar residues. Physicochemical properties of APG products strongly depend on the molecular composition. Therefore, a detailed analytical investigation of technical-grade APGs is presented. Complex mixtures of alkyl/alkenyl polyglycosides (APGs, Plantacare) and mixtures of APGs with other surfactants were analyzed by reversed-phase liquid chromatography-electrospray ionization quadrupole time-of-flight mass spectrometry (LC/ESI-QTOF-MS) using methanol-water as mobile phase and gradient elution. Analytes were separated according to the chain length of the alkyl homologs. Under the soft ionization of the ESI technique, mainly [M+Na]+ ions were observed, which proved to be very stable. Additionally [M+H]+ ions were detected. The QTOF mass spectrometer allows to identify even high molecular mass components in the mixtures, and APGs up to eight sugar residues were found. From these data, the alkyl/alkenyl chain lengths and the degree of oligomerization of the sugar moiety for different technical-grade APGs were calculated. Using MS/MS experiments, additional structural and chemical information was obtained. The presented LC/ESI-QTOF-MS approach allows to analyze and characterize various APG products, such as Plantacare. The ability of this LC/ESI-QTOF-MS approach to analyze mixtures of APGs with other surfactants is demonstrated.