Analysis of the temporal performance of one versus on-line comprehensive two-dimensional liquid chromatography

• Current LC × LC systems can outperform 1D in as short a time as 3–8 min.
• We define “crossover time” and examine effects of 1D and LC × LC variables.
• Fractions of analysis time devoted to separation and cycle times have strong effects.
• LC × LC fraction of coverage of separation space has strong influence.
• We define a unified variable to quickly assess crossover time for experiment design.

Our purpose is to generalize the chief conclusion of earlier studies based on complex maize seed extract samples that indicated that at very short times (less than 5 min) the peak capacity of 1D liquid chromatography was better than that of comprehensive, on-line 2D liquid chromatography (LC × LC), but that the LC × LC method begins to out-perform the 1D method at surprisingly short analysis times of only 5–10 min. We call the analysis time at which the peak capacities of 1D and LC × LC become equal the “crossover time.” We quantify the importance of various system parameters such as the 1D peak capacity, the second dimension cycle time and second dimension peak capacity, and fractional coverage of the two-dimensional separation space on the crossover time of 1D versus LC × LC chromatography. For ranges of these parameters used in our earlier experimental studies, we believe that crossover times will generally be between 3 and 8 min under optimized on-line LC × LC conditions.