小中大液质联用中梯度洗脱的一个奇怪的问题!!
我在做一个多肽的药物代谢试验。药物分子量4700左右。从血浆中提取后,色谱条件:Restek C18 guard column (2.1×12.5mm, 5 μm particle size) at 18 ℃. The LC elution conditions were as follows (all solvent percentages are volume fractions): mobile phase A, 0.1% FA in water; mobile phase B, 0.1% FA in ACN; time program, 0 min, 95% A/5% B; 1.0 min, 95% A/5% B; 5 min, 5% A/95% B; 5.5 min, 5% A/95% B; 6 min, 95% A/5% B; 12 min, 95% A/5% B; flow rate, 200 μl/min. The retention time is 9.26 min。 我的方法学验证达到标准。但是——
投稿后一个审稿人的意见:
A flow rate of 200 ul/min is appropriate for a column of this length. However, a gradient going from 5% organic to 95% organic in 4 minutes is not appropriate. A column that size simply cannot have reached any state of equilibrium whatsoever in that time. The authors then return the column rapidly to initial conditions by 6 minutes. Supposedly, the column is already re-equilibrating by the time the analyte comes off at 9.26 minutes. Clearly the LC separation is not really functioning as one would hope that it is. Clearly, something is happening in the column since their analyte is observed to come out, but chromatographically the assay is unsound and not in control.
这该如何解释呢??请各位指教