Ion mass chromatograms

Representative multiple ion mass chromatograms of soil samples are presented in Fig. 5.4. These gas chromatography-mass spectrometric determinations of polychlorodibenzo-p-dioxin and polychlorodibenzofurans, and non-ortho polychlorobiphenyls in differing types of samples serve to exemplify the versatility of the procedure for such analyses. The gas chromatography-mass spectrometric data were usually uncluttered by extraneous components, and interpretation of the data was routinely straightforward. 

FIGURE 15.47 2,3-Dichlorobiphenyl at a concentration of 0.05 ppb in tbe aqueous sample (0.75 pg injected on-column). Tbe upper balf of tbe figure is an extracted ion mass chromatogram for m/z 152 + m/z 222. The lower half of the figure is a full scan mass spectrum of the same peak. 

The determination of the LOD and LOQ was based on the characteristic extracted ion mass chromatograms with a peak signal-to-noise ratio S/N > 3 for LOD, and S/N > 10 for LOQ, as given in Table 4.23 for the individual phthalate compounds. Figure 4.74 shows the calibration curves of 16 PAE compounds. 

The systems reported above all rely on detection by ultraviolet absorbance, and require some separate means of identifying the desired product among the various components (and thus collected fractions) of the reaction mixture. Efficiency and throughput can be considerably enhanced by real-time detection and identification of products. Two groups have now reported preparative HPLC systems where fractionation decisions are based upon output from a mass spectrometer detector. The first preliminary report of such a system came from a collaboration between CombiChem and Sciex [21]. This system bases fractionation decisions on the output of a single ion mass chromatogram for the predicted molecular ion of the desired product. Reverse phase preparative HPLC is used in conjunction with electrospray ionization mass detection. A full report of this work has appeared in early 1998 [22]. The second report of such a system came from a collaboration between Pfizer and Micromass [23]. This system uses a flexible combination of UV and/or ion chromatograms to control fractionation. Unlike other systems, fractionation parameters are set by the mass spectrometer control software. Variants of both of the above systems will probably become commercially available in late 1997 [24]. 

Figure 5 Hydrophilic interaction liquid chromatography (HILIC) of a test mixture of organic acids (selected ion mass chromatograms M-H ).

Once the mass spectral information has been acquired, various software programs can be employed to print out a complete or partial spectrum, a raw or normalized spectrum, a total ion current (TIC) chromatogram, a mass chromatogram, accurate mass data, and metastable or MS/MS spectra. 

Figure 5.37 Mass chromatograms of the (M + H) ions from four analytes, with each introduced from a separate HPLC column into an electrospray source. From de Biasi, V., Haskins, N., Organ, A., Bateman, R., Giles, K. and Jarvis, S., Rapid Commun. Mass Spectrom., 13, 1165-1168, Copyright 1999. John Wiley Sons Limited. Reproduced with permission.

Principles and Characteristics With sample spots in a developed thin-layer chromatogram, there are no constraints on the operation of the mass spectrometer. Depending on the analytical information required, either low- or high-resolution mass-spectral data can be recorded, and both positive- and negative-ion mass spectra can be obtained from the same sample spot. 

Figure 26 shows a positive ion APCI chromatogram for a 10 (ig/ml standard of diparamethyl-dibenzylidene sorbitol together with its mass spectrum (Figure 27). Its presence in sample extracts can be identified from the (M+H)+ molecular ion at m/z 387 (Figure 28).

Fig. 9A,B GC-MS analysis of the pheromone extract of Anadevidia peponis (Noctuidae, 1 FE) treated with DMDS A TIC B mass chromatograms [141]. The mass chromatograms, which are multiplied by indicated factors, monitor the M+ of DMDS adducts derived from C10 to C16 monoenyl acetates (m/z 292,320,348, and 376) and some diagnostic fragment ions (m/z 89,117,145,173,175,203,231, and 259) to determine their double-bond position. Peaks I-VI indicate the DMDS adducts of the following components in the pheromone gland Z5-10 OAc (I),Z5-12 OAc (II),Z7-12 OAc (III), ll-12 OAc (IV),Z9-14 OAc (V), and Zll-16 OAc (VI)...

FIGURE 4.3 Total LC/MS ion chromatogram of an Abbott compound, the analog internal standard, its metabolites and impurities. Depending on the need to assay the polar metabolite, 23 to 50% of the mass chromatogram will not show useful information (arrows). 

Extracted Ion Chromatogram A chromatogram created by plotting the intensity of the signal observed at a chosen m/z value or series of values in a series of mass spectra recorded as a function of retention time. See also related entry on total ion current chromatogram. 

Figure 5.3. GC-MS analysis of organic pollutants in a sample of natural water, (a) Total ion current chromatogram (b) reconstructed ion current chromatogram (c) mass chromatogram based on the ion m/z 149 current.

Figure 5.9. GC-MS analysis of organic pollutants in natural water (Pegasus III instrument, LECO). (a) Six-seconds segment of TIC chromatogram, (b) Mass chromatograms, reconstructed by software and based on the current of ions of m/z 59, 64, 173, 49, 158, 99, and 93.

Macro FindPeak.mac automatically exports the mass spectral data, including ion masses and abundances for each peak in the gas chromatogram, to a. CSV (comma separated value) file. Each. CSV file contains MS data for one peak from the gas... 

Fig. 11.17. Simulated mass chromatograms resulting from precursor ion and constant neutral loss tandem mass spectra (middle and bottom traces), illustrating the selectivity that those MS/MS scan modes can bring to chromatographic analyses. The top trace in the figure represents a total ion chromatogram obtained using a conventional single stage of mass analysis.

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