是这样的 Rhizosphere samples (approximately 3 g RFW) were ultrasonically extracted in 30 ml of 9:1 acetonitrile:water containing 0.1%trifluoroacetic acid. After 10 min of ultrasonic agitation, extractswere 11mm filtered (Qualitative Paper Grade 1, Whatman, UK),evaporated with dry nitrogen, redissolved in 3 ml of methanol, and0.2mm filtered (Millex-GN, Millipore, USA). SPE packings withdifferent pore sizes and bonded silica or polymeric particles wereevaluated. Because of the hydrophilic–hydrophobic nature of theanalytes, the SPE columns worked best when chosen to maximizeretention of impurities. Using SPE columns of octadecyl unendcapped bonded silica with an average pore size of 60 ? (HypoSepC18, Thermo-Electron, USA), both surfactin and iturin A were elutedwith methanol, then evaporated dry, redissolved in 0.5 ml of methanol, and refiltered (0.2mm) for subsequent HPLC injectionand analyses.我现在已经做到了把样品溶于3ml的甲醇中。然后买了Hyposep C18的柱子，但是不明白这个方法里说的“The SPEcolumns works best when chosen to maximize retention of impurities” 是什么意思。我现在应该怎么前处理柱子呢，样品本来就溶解在甲醇中，还说从SPE柱子上面用甲醇洗脱，求高手示下。 显示全部