Line shape test spectra

The resolution and line shape test spectra in Figures 3a and obtained at 500 MHz demonstrate that a level of performance has become feasible that until recently was unachievable even at a considerably lower field. Obtainment of this degree of field uniformity is crucial, however, if the benefit of enhanced shift separation is to be fully exploited. 

Perform a fit to the imaginary part of the spectrum using error structure weighting. Increase the number of line-shapes used until the maximum number of statistically significant parameters is obtained. Ideally, the ratio of the sum of squares to the noise level should be within the F-test boxmds given by the program. 

The QC sample should produce a chromatographic peak with shape and TIC abundance as expected from previous injections of the same QC sample. The spectrum from the QC sample should have a profile of mass fines that is in accordance with spectra from previous injections. The test spectrum should not contain extra lines. 

Figure 5.18 On-line analysis. (A) Photograph of a nib-shaped nanoESI interface used for on-line tests. The nib structure is fabricated using the negative photoresist SU-8 and its capillary slot is coupled to standard capillary tubing (10 pm i.d.) for on-line MS analysis. (B) Base peak trace obtained for the separation of 800 fmol of a cytochrome c digest using a nanoLC setup coupled to a nib-shaped nanoESI interface. The inset shows the mass spectrum corresponding to fragment 92-99 of cytochrome c, which is eluted at 23.8 min (flow rate, 100 nLmin-1 HY of 1.5 kV). (Adapted with permission from Ref. 26).

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