Chem 8157

I have the following questions for Nic and the rest of the class.

1. Is the micro FFE isoelectric focusing device suitable for analyatical or preparative experiments?

2. Nic mentioned that EOF and Joule heating limit peak capacity. I mentioned that there are other fundamental limitations (i.e. equilibrium and kT). Describe the fundamental parameters that affect peak capacity [c.f. Equations 1 and 2 in the paper]

3. If the separation channel was 5 cm wide (instead of 2), what is the expected peak capacity?

1. The micro FFIEF device is designed to be used for preparative purposes however, I would assume that some quantitative results could be obtained since the authors were taking flourescence linescans across the separation channel, which could then be correlated to concentration assuming a calibration curve of some sort was created.

2. The fundamental parameters described in Equations 1 and 2 include the diffusion coefficient, the electric field strength, the slope of the pH gradient, and the mobility slope of the analyte. The mobility slope and the diffusion coefficient are intrinsic properties of the analytes, so only the electric field strength and slope of the pH gradient can be varied to increase the peak capacity (decrease avg. peak width). Joule heating limitations put an upper limit on the electric field strength and decreasing the slope of the pH gradient would obviously be costly as far as pH range within the device is concerned.

3. If the separation channel was increased by 2.5 times, the expected peak capacity would increase 2.5-fold as well (Eqn. 7). So in terms of the peak capacity reported in this paper, it would increase from 29 to approximately 73 peaks.

I agree with Nic in the fact that although free flow devices are ideal for preparative experiments because of their continuous nature and ability to collect fractions, some analytical experiments could also be done because the LIF detection system lends itself well to quantitative data.