Optima 1ms column

Ten mg of each polysaccharide were hydrolyzed with 1 mL of TFA 2 M at 120 °C during 90 min, then evaporated under dryness using nitrogen stream at 60 °C. Derivatization of monosaccharides was realized according to Pierre et al. [31 (link),32 (link)], dissolving the lyophilizate in pyridine and Sylon (BSTFA/TMCS; 99%/1%). The mix was incubated at room temperature 2 h and under Argon to form trimethylsilyl-O-glycosides which were solubilized in dichloromethane after evaporation of reagent. The samples were injected on an Agilent 6890 Series GC System coupled to an Agilent 5973 Network, equipped with an OPTIMA-1MS column (Macherey-Nagel; 30 m, 0.32 mm, 0.25 µm) from Macherey–Nagel with a helium flow rate of 2.3 mL/min. The first time, temperature was at 100 °C for 3 min. In a second step an increment of 8 °C/min up to 200 °C for 1 min was applied before a final increment of 5 °C/min up to 250 °C. Electronic Impact (EI, 70 eV) ionization method was performed with the trap temperature set at 150 °C and the target ion was fixed at 40–800 m/z. The relative molar proportions were calculated using area normalization method. As monosaccharides standards, Ara, Rha, Gal, Glc, Xyl, Man, GlcA and GalA were prepared and analyzed following the same procedure.

The monosaccharide composition of NRLP was determined using GC/MS-EI according to Pierre et al. [30 (link)]. Briefly, 10 mg of NRLP were hydrolyzed with 2 M trifluoroacetic acid (TFA) at 120 °C for 90 min. After the derivatization of hydrolysates using BSTFA: TMCS (99:1), the mixture was evaporated under nitrogen steam at 60 °C and trimethylsilyl-O-glycosides were solubilized into dichloromethane. The samples were injected on an Agilent 6890 GC system coupled to an Agilent 5973 Network Mass Selective Detector (Agilent, Santa Clara, CA, USA), equipped with an OPTIMA-1MS column (Macherey-Nagel; 30 m, 0.32 mm, 0.25 μm). The apparatus was set up according to the following parameters, i.e., target ion: 40–800 m/z, injector line temperature: 250 °C, trap temperature: 150 °C, split ratio: 50:1, helium pressure: 8.8 psi; helium flow rate: 2.3 mL/min, ionization: 70 eV by electronic impact. The rise in temperature was a first step at 100 °C during 3 min, an increment of 8 °C/min up to 200 °C for 1 min and then a final increment of 5 °C/min up to 215 °C. The monosaccharide standards (Glc, Ara, GlcA, Fuc, Rha, Gal, Man, Xyl and GalA) were prepared using the same procedure.