Peak shifts and distortion due to solute relaxation in flow field-flow fractionation
Peak shifts and distortion due to solute relaxation in flow field-flow fractionation
复制标题
流场流分馏中溶质弛豫导致的峰移和畸变
DOI：
10.1021/ac50012a037
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发表时间：
1977
影响因子：
7.4
通讯作者：
J. Giddings
中科院分区：
文献类型：
--
作者：
Frank J. Yang;M. N. Myers;J. Giddings
Sir：在场流分馏（FFF）中，溶质弛缓过程可以定义为远离平衡的溶质物质在FFF通道中接近其横向平衡分布的现象。这种现象在溶质样品被注入或带入分馏通道后立即发生。在这一点上，溶质总是混合在整个流动截面上。然而，在外场的影响下，它开始积累（放松）成一个狭窄的指数平衡层，靠近一个壁，这里称为积累壁（1,2）。溶质弛豫所需的时间可能会对FFF的正常行为产生重要的干扰。从积聚壁附近开始的溶质将达到平衡，因此，几乎立即达到正常的保留状态。然而，溶质进入靠近对面墙壁的通道必须首先穿过墙壁之间的间隙。在这里，它受到通道中心相当高的流速的影响，并被冲到已经在堆积壁附近达到平衡的溶质前面。因此，溶质区可以在一开始就被加宽，其重心充分向前移动，从而大大增加了最终峰的宽度和减少了保留体积。解决这个问题的一种方法是止流法（3-7），在这种方法中，一旦溶质峰值到达通道顶部，通道流动就会停止。在没有差速扰动影响的情况下发生松弛，因此再次开始流动。
Sir: The solute relaxation process infield-flow fractionation (FFF) may be defined as the phenomenon in which solute material far from equilibrium approaches its lateral equilibrium distribution in the FFF channel. The phenomenon is most important immediately after the solute sampleis in-jected or carried into the fractionating channel. At this point, solute is invariably mixed over the entire flow cross section. Under the influence of the external field, however, it begins to accumulate (relax) into a narrow, exponential equilibrium layer next to one wall, termed here the accumulation wall (1, 2).The time required for solute relaxation is potentially ca-pable of creating important disturbances in normal FFF be-havior. Solute that begins near the accumulation wall will reach equilibrium and, therefore, a state of normal retention almost immediately. However, solute entering the channel near the opposite wall must first cross the gap between the walls. Here it is subjectedto the considerably higher velocity of flow in thecenter of the channel and is swept ahead of the solute already at equilibrium near the accumulation wall. Thus the solute zone may be broadened and its center of gravity moved forwardsufficiently at the very beginning to contribute substantially to an increased width and decreased retention volume of the final peak. A solution to this problem is the stop flow method (3-7) in which channel flow is halted as soon as the solute peakreaches the head of the channel. Relaxation occurs without thedis-turbing influence of differential velocity and thus flow is commenced again.