1. I believe this issue deals with changes in pressure with ESI apparati. Droplets are formed at atmospheric pressure while the m/z analyzer is usually in a vacuum to avoid uncontrolled fragmentation of ions. In nanoLC-ESI-MS, reduced flow rates are used which result in a higher charge density on the surface of the droplets. This should result in more efficient ionization which would allow the "ion intake" to be setup closer to the electrospray interface.
2. I think it's uL.
3. Hypothesis- due to the decrease flow rate it may be more difficult to evaporate your buffer-analyte mixture. A heated emitter could assist with this phase transition.
It appears from the paper that nano-LC is more sensitive because it does clog the sprayers with solvent and other material. This means that more of the actual analyte is getting through the sprayers and can be detected by the MS giving it a greater sensitivity. While there may be other factors contributing to the greater sensitivity, this reason seemed to be the main one highlighted in the paper. It appears that the authors used nano-LC for their experiments.
With the array of capillaries, I would think the "plume" of sample is wider and would potentially cause a wider band of sample to be introduced to the mass analyzer. So, is the resolution affected by this ESI technique?
1) The sensitivity for nanoLC-ESI-MS is better because of great droplet desolvation. The main problem with ESI-MS in general is the low sensitivity due to incomplete droplet desolvation. Using nanoLC-ESI-MS, smaller charged ion droplets are produced, which will desolvate better and promote a greater charge per analyte molecule.
According to Mellisa's question, they did post-column study to see if the emiter array causes lost of resolution. The result turns to be the band width is almost the same as in one emitter case, while the intensity increase. So there is no obvious post-column broadening.
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Comments
I have some questions for Meng and the rest of the class.
1. Why is the sensitivity of nanoLC-ESI-MS better than the sensitivity of microLC-ESI-MS?
2. In this paper, what do they use, microLC or nanoLC?
3. Why do the emitters (i.e. electrospray tips need to be heated?)
Posted by: Edgar Arriaga | March 27, 2008 04:33 PM
1. I believe this issue deals with changes in pressure with ESI apparati. Droplets are formed at atmospheric pressure while the m/z analyzer is usually in a vacuum to avoid uncontrolled fragmentation of ions. In nanoLC-ESI-MS, reduced flow rates are used which result in a higher charge density on the surface of the droplets. This should result in more efficient ionization which would allow the "ion intake" to be setup closer to the electrospray interface.
2. I think it's uL.
3. Hypothesis- due to the decrease flow rate it may be more difficult to evaporate your buffer-analyte mixture. A heated emitter could assist with this phase transition.
Posted by: Chad Satori | March 30, 2008 11:09 AM
It appears from the paper that nano-LC is more sensitive because it does clog the sprayers with solvent and other material. This means that more of the actual analyte is getting through the sprayers and can be detected by the MS giving it a greater sensitivity. While there may be other factors contributing to the greater sensitivity, this reason seemed to be the main one highlighted in the paper. It appears that the authors used nano-LC for their experiments.
Posted by: Jonathan Dozier | March 30, 2008 06:36 PM
With the array of capillaries, I would think the "plume" of sample is wider and would potentially cause a wider band of sample to be introduced to the mass analyzer. So, is the resolution affected by this ESI technique?
Posted by: Melissa Maurer-Jones | March 30, 2008 07:17 PM
1) The sensitivity for nanoLC-ESI-MS is better because of great droplet desolvation. The main problem with ESI-MS in general is the low sensitivity due to incomplete droplet desolvation. Using nanoLC-ESI-MS, smaller charged ion droplets are produced, which will desolvate better and promote a greater charge per analyte molecule.
2) nanoLC-ESI-MS
3) to optimize ion transfer
Posted by: Courtney Wettlaufer | March 30, 2008 08:48 PM
According to Mellisa's question, they did post-column study to see if the emiter array causes lost of resolution. The result turns to be the band width is almost the same as in one emitter case, while the intensity increase. So there is no obvious post-column broadening.
Posted by: Meng Jing | March 30, 2008 09:17 PM