Department of Chemistry, Smith and Kolthoff Halls, University of Minnesota, Minneapolis, MN 55455, USA.
J Chromatogr A. 2011 May 20;1218(20):2984-94. doi: 10.1016/j.chroma.2011.03.032. Epub 2011 Apr 12.
The experimental effects of sampling time on the resolving power of on-line LC×LC were investigated. The first dimension gradient time ((1)t(g)) and sampling time (t(s)) were systematically varied ((1)t(g)=5, 12, 24 and 49 min; t(s)=6, 12, 21 and 40s). The resolving power of on-line LC×LC was evaluated in terms of two metrics namely the numbers of observed peaks and the effective 2D peak capacities obtained in separations of extracts of maize seeds. The maximum effective peak capacity and number of observed peaks of LC×LC were achieved at sampling times between 12 and 21s, at all first dimension gradient times. In addition, both metrics showed that the "crossover" time at which fully optimized 1DLC and LC×LC have equal resolving power varied somewhat with sampling time but is only about 5 min for sampling times of 12 and 21s. The longest crossover time was obtained when the sampling time was 6s. Furthermore, increasing the first dimension gradient time gave large improvements in the resolving power of LC×LC relative to 1DLC. Finally, comparisons of the corrected and effective 2D peak capacities as well as the number of peaks observed showed that the impact of the coverage factor is quite significant.
考察了采样时间对在线 LC×LC 分辨率的实验影响。系统地改变了第一维梯度时间（(1)t(g)）和采样时间（t(s)）（(1)t(g)=5、12、24 和 49 min；t(s)=6、12、21 和 40 s）。在线 LC×LC 的分辨率通过两个度量来评估，即观察到的峰数和玉米种子提取物分离中获得的有效 2D 峰容量。在所有第一维梯度时间下，当采样时间在 12 到 21 秒之间时，LC×LC 达到了最大有效峰容量和观察到的峰数。此外，这两个度量都表明，完全优化的 1DLC 和 LC×LC 具有相等分辨率的“交叉”时间随采样时间而略有变化，但对于采样时间为 12 和 21 秒时，仅约为 5 分钟。当采样时间为 6s 时，获得的交叉时间最长。此外，增加第一维梯度时间可以大大提高 LC×LC 相对于 1DLC 的分辨率。最后，对校正和有效 2D 峰容量以及观察到的峰数进行比较表明，覆盖因子的影响相当显著。
