Li J M, Caldwell K D
Department of Bioengineering, University of Utah, Salt Lake City 84112.
J Chromatogr. 1991 Aug 30;555(1-2):260-6. doi: 10.1016/s0021-9673(01)87187-9.
Conventional operation of field-flow fractionation (FFF) systems involves carrying out the analysis at a constant flow of carrier; the flow is temporarily interrupted after injection of a sample in order to permit its equilibration under the applied field. Retention is calculated as the ratio of elution times for a non-retained species and the sample of interest, respectively. Such time-based retentions are only valid if the flow-rate is precisely known at all times during the run. The peristaltic pumps often used with FFF equipment are shown to have an output which varies unpredictably in time. Furthermore, initiation of flow after relaxation is shown to result in significant periods of transient behaviour while the system adjusts to the operating pressure. These and other variations in flow-rate can be eliminated as sources of error by basing the retention measurement on effluent weight, rather than on time. For this purpose, an electronic balance is interfaced with the system's computer, so that detector response/effluent weight data pairs are continuously monitored during the course of the FFF analysis.
场流分级（FFF）系统的传统操作包括在恒定的载流流速下进行分析；在注入样品后，流动会暂时中断，以便使其在施加的场中达到平衡。保留率分别计算为非保留物质和感兴趣样品的洗脱时间之比。只有在运行过程中始终精确知道流速时，这种基于时间的保留率才有效。常用于FFF设备的蠕动泵显示出其输出随时间不可预测地变化。此外，松弛后启动流动会导致在系统调整到工作压力时出现显著的瞬态行为期。通过基于流出物重量而不是时间来进行保留测量，可以消除这些和其他流速变化作为误差来源。为此，将电子天平与系统计算机连接，以便在FFF分析过程中连续监测检测器响应/流出物重量数据对。
