LC/MS total ion chromatograms

FIGURE 22 (a) HPLC/UV chromatogram, (b) ESI LC/MS total ion chromatogram, (c) extracted mass spectrum for RT = 25.35 min peak without background subtraction, (d) Extracted mass spectrum for the same peak with background subtraction. 

Since the melanin formation assay was run against a cell viability assay, the activity peak maximum at fraction Dll was most likely due to cytotoxicity. The dereplication of another active peak located from fractions D7 to D2 is illustrated in Figure 9. Every active fraction was analyzed by HPLC/PDA/MS. There was a peak located at Rt=16.33 min in the LC/MS total ion chromatogram of active fractions. This peak showed the same pattern of increasing to decreasing intensity as the trend exhibited by the melanin inhibition activities of those fractions. 

Fig. (9). LC/MS total ion chromatograms of HTP fractions D7 to D2 from Mallotus repandus.

Figure 1. Thermospray LC/MS total ion chromatogram of 0.25 (ig standard mixture of six sulfonylurea herbicides.

Figure 1. Thermospray LC/MS total ion chromatogram for male rat bile after oral dosing with SKSF 96148 (100 mg/kg). Major drug related components are designated M1-M5. Linear LC gradient indicated by dashed line (%B is percent acetonitrile).

Figure 5.28 LC-electrospray-MS total ion chromatogram of sulfated oligosaccharides from mucins purified from the porcine large intestine, where the annotations indicate the molecular ions observed from each component. Reprinted with permission from Thoms-son, K. A., Karlsson, H. and Hansson, G. C., Anal. Chem., 72, 4543-4549 (2000). Copyright (2000) American Chemical Society.

Fig. 2.11.31. APCI-LC-MS(-) total ion current chromatogram (TIC) (4) and selected mass traces (l)-(3) of compounds as in the overview spectrum in Fig. 2.11.30 gradient elution separated by RP-Clg column [22,61].

Because online separations provide such a wealth of information about target proteins, interpretation becomes of critical importance in order to make full use of the data. The first step in any analysis of LC-MS data involves integration and deconvolution of sample spectra to determine protein mass and intensity. In manual analysis (Hamler et al., 2004), users identify protein umbrellas, create a total ion chromatogram (TIC), integrate the protein peak, and deconvolute the resulting spectrum. Deconvolution of ESI spectra employs a maximum entropy deconvolution algorithm often referred to as MaxEnt (Ferrige et al., 1991). MaxEnt calculates... 

FIGURE 13.4 Total ion chromatograms from the ID LC/MS analysis of a yeast ribosomal protein fraction separated using 0.1% TFA (Panel a) and 0.1% formic acid (Panel b) as mobile phase modifiers. TFA produced narrower, more concentrated, peaks for mass analysis that did not overcome the significant electrospray ionization suppression associated with using this modifier for LC/MS studies, resulting in an overall reduction in component intensities. 

FIGURE 13.5 The total ion chromatogram and deconvoluted protein mass map for a ID LC/MS analysis of yeast ribosomal proteins. The bubble size is proportional to component intensity. 

Mass spectra recorded using LC/MS software may be displayed individually, signal averaged, and background subtracted. Furthermore, these data may be used to plot computer-reconstructed selected ion or total ion chromatograms. 

A logical extension of FI A with serial EC-LC-MS is to incorporate a separation technique to further characterize the products. Figure 8.2 is an example of precolumn EC oxidation of tamoxifen. With the EC cell at 500 mV, the total ion chromatogram (TIC) shows two primary peaks corresponding to starting material (tamoxifen) and, at an earlier retention time, an N-demethylated product. With the precolumn EC cell at 1000 mV (Fig. 8.3), additional peaks are evident, including possible aromatic... 

The MS detector is more sensitive and requires much less sample than UV detection. The LC/MS system is often designed either with an in-line secondary detector or with a splitter system before the interface and a second detector so that additional information can be obtained on the sample. Figure 15.10 compares the chromatographic signals from a variable UV detector and the full-scan total ion chromatogram (TIC) from a MS detector run in series for detection of an adhesive extract. 

Using this optimized method shown in Figure 8-49 that starts at 25v/v% acetonitrile, LC-MS studies were performed to determine the [M -i- H]+ ion of the impurity that has been resolved from the main peak. The mass spectrum of Product M was taken and was shown to be spectrally homogeneous. The mass spectrum of the impurity (RRT 1.04) that has now been resolved from the main peak was also taken. The UV and the total ion chromatograms are shown in Figure 8-50. This impurity, RRT 1.04, has the same [M -i- H]+ ion that was co-eluting with the main component in the initial separation on the C8... 

Figure 21.1 Total-ion-chromatogram of an interesterified palm oil, after Ag -LC-ESI-MS. Reprinted from [19] with permission. 1998, Elsevier Science BV.

Figure 22.2 LC-MS reconstracted total-ion chromatogram of a separation of a homologous series of oligonucleotides p(dT) with n between 12 and 30 on a micropellicular octadecylated PS-DVB column using a solvent gradient of acetonitrile in 50 mmol/1 TEABC. Reprinted from [9] with permission. 1999, American Chemical Society.

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