results in mass spectral peak intensities that more accurately reflect relative
amounts of material as compared to traditional online ESI–LC/MS. Hop et al.
used a chip-based nanospray ionization source (NanoMateTM) to compare the
ionization efficiencies of compounds with different physical–chemical char-
acteristics and found that the ionization efficiencies varied to a much lesser
extent in NSI MS compared to that in LC/MS (Hop et al., 2005). A set of 25
compounds from six distinct structural series was examined using conventional
LC/MS and the NanoMate. The LC/MS data (Fig. 11.4a) showed that the
120.0100.080.060.040.020.00.0Relative signal intensitySeries 1 Series 2 Series 3 Series 4 GSH-adducts Series 5(a) Compounds analyzed by lc/ms120.0100.080.060.040.020.00.0Relative signal intensitySeries 1 Series 2 Series 3 Series 4 GSH-adducts Series 5(b) Twenty five compounds analyzed with the NanomateFIGURE 11.4 Relative ion intensities obtained for 25 compounds from 6 distinct
structural series using conventional LC/MS (a) and NanoMateTM(b). Reprinted from
Hop et al. (2005) with permission of John Wiley and Sons Limited.
344 APPLICATION OF LIQUID CHROMATOGRAPHY/MASS SPECTROMETRY