Can GC×GC be considered a super-resolution technique?
Philip Marriott & Yada Nolvachai |
We posed the question above at the Riva del Garda ISCC/GC×GC symposium in May – perhaps somewhat rhetorically given that the audience was made up of committed GC×GC researchers. Today, “super-resolution” is a term apparently reserved for the Nobel prize-winning spectroscopic technique that is defined by achieving spectroscopic imaging at wavelengths less than those of light. This feat is accomplished by a combination of the “blinking” of fluorescent emitting centers – for instance, located along a fibril – and the mathematical localization of the center of the emission, which effectively reduces the dispersion of the light and centers it better on the emitting moiety. In this way, a biological feature comprising the emitting centers can be defined with much greater precision.
So, does GC×GC qualify as a super-resolution technique? We define the separation power of GC in terms of peak capacity – the total analysis time/peak width measure. Or, in other words, how many peaks can be fitted in the chromatogram. For example, if we consider the limit for well-resolved peaks to be separation by 4 σ (the width at baseline), then we might fit 400 peaks in the total chromatogram. If we relax (reduce) the peak width measure for defining separated peaks, then we can fit in more peaks. There is a natural limit to how small the peak separation measure can be before we are unable to distinguish neighboring peaks, which is exacerbated as peak response magnitudes become increasingly different. For a regular (non-MS) GC detector, we rely upon peaks being adequately resolved.
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