Fragmentation Mechanism of Alkyl-monoglycosides by Mass Spectrometry

Alkylmonoglycosides with different alkyl chain lengths (APG8, APG9, APG10 and APG14) were prepared by Fisher reaction of glucose with fatty alcohols. Excess alcohol was used to increase the possibility of producing alkyl monoglycosides products. Mass spectrometry with chemical ionization was used to confirm their structures as alkyl monoglycosides. Accordingly, the obtained signals at m/z = 293, 307, 321 and 377 corresponds to their protonated molecules. The base lines which are the most intensive signals in each spectrum at m/z = 145, 127, 141 and 197 represent the most abundant ions and define the pathway of their fragmentation mechanism. The mass 145 for APG8 is generated from the parent ion by elimination of the mass ROH followed by H2O. For this compound cleavage occurs at the C–O bond next to the glucose ring, while fragmentation of alkyl monoglycosides with carbon number 9, 10 and 14 occurs at the O–R bond releasing the alkyl cation R of the aglucone moiety (CnH2n+1) along with large fragment ions characteristic of the glucose moiety.

Mesoporous Silica Sol-Gel as Catalyst for the Synthesis of Alkylpolyglucosides

The synthesis of alkylpolyglucosides involves condensation of decanol with dextrose in the presence of mesoporous silica sol-gel as a catalyst. In this study, mesoporous silica was produced using sol-gel technique by converting tetraethyl orthosilicate (TEOS) into silica. The mesoporous silica was characterized using BET surface area measurement and X-ray Photoelectron Spectroscopy surface analysis. The specific BET surface area was 794m2/g. From the XPS analysis, the Si2p binding energy is 103.7 eV while the O1s binding energy is 532.8eV indicating the formation of Si-O-Si bond which attributed to SiO2. Mesoporous silica has been found efficient to be solid catalyst for synthesis alkylpolyglucosides and easy to be separated. The reaction was carried out 8 hours at 110°C-120°C under vacuum condition. The mass determination of alkylpoluglucosides has been achieved by ESI LC-MS/MS (ToF) positive-mode giving a mass peak at m/z = 343.21 corresponding to [M++ of alkylmonoglucoside peak at retention time 11.0 min.