Selected ion chromatograms

Fig. 2.1.3. Selected ion chromatograms for C14-C17-SAS homologues in (a) primary effluent and (b) secondary effluent collected from a sewage treatment plant. Reproduced with permission from Ref. [35]. 1994 by American Chemical Society.

Figure 13. Comparison of UV and MS chromatograms using a 1.0-mm i.d. column packed with a 5-pm diameter Supelcosil C-18. LC-MS interface used aerosol spray deposition on a moving belt. Peaks correspond from left to right to 0.2 pg each of resorcinol, 1,5-dihydroxynaphthol, and 2-methyl-phenol. Conditions 41% acetonitrile and 59% water (v/v) with 0.1% trifluoro-acetic acid at a flow rate of 40 pL/min. A, UV trace at 280 nm, 0.015 AUFS B, MS trace, selected ion chromatogram. (Reproduced from reference 54.

GC-MS runs were stored as files by the data system on discs FORTRAN routines were written to compare selected parameters in file sets and to reduce the data to summary tables for hard copy output. These routines facilitated the determination of peak areas of components in extracted ion current profiles (EICP) for both total and selected ion chromatograms, calculated the removal of components of interest (e.g., those containing halogen isotopes) by treatment processes (GAC, CI2) or derivatization, summarized the occurrence of new components of interest in treatment or derivatization, and calculated the percent of the total ion current represented by a given component. The programs allowed operator discrimination between major and minor components in a file set by preselection of an ion current threshhold for data reduction. For data summarized herein, components were >4000 ion counts, which corresponds to a level >5 of the internal standard (decachlorobiphenyl) response. 

What is the difference between a total ion chromatogram and a selected ion chromatogram ... 

Figure 3. Selected ion chromatogram (m/z 191) for two archaeological ceramic samples (a) AK2INTRES and (b) CS1INTRES. Key to peak identification is...

Fig. 3 Schematic drawing of a combined GC-MS instrument and its application for the recording of mass spectra and selected ion chromatograms...

Figure 2. Selected ion chromatogram of a mixture of the methyl esters of tetrafluorobutyryl 1AA and dt-IAA. The IAA was from an extract of com seedlings and the dt-IAA added during homogenization. Retention time is in minutes and the masses monitored are 326.2 and 385.2 for IAA and 330.2 and 309.2 for drlAA. The percent dt- AA has been computed by the area of the peaks at 330.2/326.2 + 330.2 (base peak) and 389.2/385.2 + 389.2 (molecular ion).

In the original heroin assay by Goldberger et al., heroin, 6-AM, morphine, and codeine were extracted by LLE and assayed simultaneously by GC/MS. The performance of the assay including analyte recovery and stability was not optimized, and the assay was limited by interference. Selective ion chromatograms of hair and standard extracts are illustrated in Figure 4. In an improved procedure by Goldberger et al., two sets of SPE extracts were assayed independently by GC/MS one set for heroin, and other set for the trifluoroacetyl derivatives of 6-AM and morphine. The extraction process, in combination with the use of aprotic solvents, mild elution solvents, and an enzyme inhibitor, provided maximum analyte stability for the recovery of heroin from hair with minimal (<5%) hydrolysis. The procedure was modified further by Cone et al. for the analysis of cocaine, heroin, and metabolites in hair. 

In further studies of anatomic origin by Cone et al. with heroin users, 20 paired head and arm hair samples were assayed for heroin and its metabolites. Heroin was detected in two head hair samples and 6-AM was present in 14 head hair and six arm hair samples. If present, the concentration of 6-AM was generally greater in arm hair than head hair. Morphine was present in three head hair samples and was not present in arm hair samples. Selective ion chromatograms of hair and standard extracts adapted from Cone et al. are illustrated in Figure 3. 

Figure 7-20. Selected ion chromatograms typical for the LC/ESI-MS/MS determination of ET-743 in human plasma blank plasma (A) and plasma samples collected at the end (B, 0.1088 ng/rtiL) and 48 hr after cessation of a 24-hr infusion at a dose level of 100 xg/m (C, 0.0183 ng/mL). The solid line represents the transition of m/z 744.4 to 495.0 (ET-743), and the dashed line represents the transition of m/z 730.6 to 478.8 (internal standard ET-729). (Reprinted from reference 103, with permission of John Wiley Sons.)...

Fig. 4. GC-ECNI high resolution mass spectrometry selected ion chromatograms of the C10H15C17 formula group, based on the [M-Cl] ion, for beluga blubber samples from Cumberland Sound and Hudson Bay are compared with an extract of an air sample from Alert (NWT) at the northern tip of Ellesmere Island and in the PCA-60 standard. The air sample shows a strong resemblance to the commercial product while the profile in beluga suggests considerable biotransformation. Results from Tomy et al. [78]...

Figure 4 Distribution of triaromatic steroids (68) in GC-MS m/z = 231 selected ion chromatograms in (a) a Phanerozoic oil of low thermal maturity, (b) a mature Phanerozoic oil, and (c) an overmature bitumen from the late Archaean Fortescue Group in Western Australia. The inset in (c) is a 20 X magnification of the elution range of C26 to C28 triaromatic steroids (68b) (Brocks et ah, 2003a,b) (reproduced by permission of Elsevier...

The combination of immobilized enzyme columns with HPLC/thermospray MS can be very useful in peptide identification and sequencing [6,7], There are a number of ways of combining the immobilized enzyme column, HPLC and MS detection for peptide analysis. Use of an endopeptidase column prior to HPI.C separation and MS detection will enable separation of each hydrolysis product for Identification. Figure 2 shows the trypsin column/HPLC/thermospray MS of Y-endorphin. The selected ion chromatograms show the retention time for each tryptic hydrolysis product Tj and T. Typically, this column configuration can only be used on purified samples since no separation or column clean-up is performed before hydrolysis. 

Figure 55-8 Partial urine organic acid profiles 15-23 minute portion of a 33 minute run) of two patients with tyrosinemia type i. A, Acutely III patient with markedly elevated excretion of succiny[acetone, pre-NTBC treatment.The insert shows the selected ion chromatogram of the [M-15] ion of succinylacetone O-TMS-oxime TMS ester, m/z 212 B, Fifteen month old patient, succinylacetone was not detected by either total ion current (orrow) or selected ion chromatogram in three different urine specimens.This patient was later shown to be compound heterozygote for the French Canadian common splice mutation (IVS12+5G>A) and another previously unreported mutation. Peak legend I, Succinylacetone (oxime, peak I) 2, succinylacetone (oxime, peak II) 3, 4-hydroxy phenyllactic acid 4, 4-hydroxy phenylpyruvic add (oxime).The symbol marks the internal standard (pentadecanoic acid), signal abundance is normalized to the intensity of the internal standard peak.

Figure 2. GC-EIMS analysis of the 3-methylcatecholates of methyl- and phenylarsonic acids. Key A, reconstructed ion chromatogram of known methyl- and phenylarsonic acid derivatives of3-methylcatechol B, selected ion chromatogram showing m/e 197for each derivative C, selected ion chromatogram for methylarsonic acid-3-methylcatecho-late at m/e 212 and D, selected ion chromatogram for phenylarsonic acid-3-methyl-...

Figure 19 Standard addition calibration curves. Equal volumes of solvent containing varying amounts of standard are added (spiked) into the sample. The samples are analyzed and the analyzer response (e.g., area under the TIC or selected ion chromatogram) is plotted against the amount of standard added. The analyte concentration is estimated by extrapolating a linear least-squares regression toy = 0 (a). An alternative approach is to plot the difference between the spiked samples and the unspiked sample. The same calibration curve now passes through the origin and the sample analyte concentration can now be determined by interpolation with improved confidence limits164 (b).

Metabolites to be identified are present in the incubated sample. In this example, Fig. 34 represents a microsomal incubation aliquot taken at 40 min. The total ion chromatogram (Fig. 34A) is somewhat difficult to interpret because of the low intensities of metabolites relative to background. Therefore, selected ion chromatograms are constructed based on a general understanding of metabolism principles described earlier and through use of specialized software capable... 

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