Current profile

Figure 24.8 Charging current profile on no load in a transmission line...

Figure 24.12 Voltage and current profiles when the line at the far end is open-circuited...

Figure4.4 c(2 x 2)A structure. Left panel structural model. Right top panel corresponding simulated STM image (VB = + 1.30V, / = 0.04nA). The protrusions correspond to oxygen couples, whereas the depressions are the hollow sites surrounded by O—H complexes. Right bottom panel simulated current profiles along [00 1] at decreasing (light blue to red) tip-surface distances. (Reprinted with permission from Ref. [18].)...

Figure 7.6 Total ion current profile of the acidic fraction of a sample from a linseed oil reference paint layer (Opificio delle Pietre Dure, Florence, Italy), after saponification and silylation of carboxylic and hydroxyl ic groups [9]...

LC separation applying ion chromatography in combination with ion spray mass spectrometric detection was applied for the examination of a synthetic mixture of alkyl sulfonates (CnH2n+i-SO3 re = 8) and AS with different alkyl chain lengths in the selected ion monitoring (SIM) ESI-MS(—) mode [53], Selected ion current profiles provided the separation of the compounds. The ionic matrix constituents of the eluent were removed by a suppressor module prior to MS detection to improve the signal to noise (S/N) ratio. 

Fig. 3.11. Positive-ion SRM ion current profiles for 1 (m/z 443—415 black trace), 2 (mJz 443 - 415, red trace), and 3 (m/z 345-285, blue trace) obtained during development lane scans of replicate development lanes of the RP C2 TLC separation of a mixture (50 ng each) of rhodamines 6G (1), B (2), and 123 (3) at surface scan rates of (a) 19, (b) 44, and (c) 190 jum/s using a DESI solvent (methanol) flow rate of 0.5 //Emin. Dwell time was 100 ms for each transition. Signal levels were normalized to the signal in panel (c). Chromatographic resolution, R, calculated from the data is shown in each respective panel. Reprinted with permission from G. J. Van Berkel et al. [89].

When working with non-radiolabeled drugs the major challenge is to find metabolites in the biological matrices. Because the enzymes responsible for metabolism are quite well characterized metabolic changes can partially be predicted. For example hydroxylation of the parent drug is in many cases the principal metabolic pathway. From a mass spectrometric point of view it results in an increase of 16 units in the mass spectrum. In the full-scan mode an extracted ion current profile can be used to screen for potential metabolites. In a second step a product ion spectrum is recorded for structural interpretation. Ideally, one would like to obtain relative molecular mass information and the corresponding product ion spectrum in the same LC-MS run. This information can be obtained by data dependant acquisition (DDA), as illustrated in Fig. 1.39. 

Advances in high resolution mass analyzers (TOF, FT-ICR, orbitrap) have greatly improved the detection and identification of metabolites based on accurate mass measurements. In single MS mode accurate mass determination is mainly used to differentiate between isobaric ions. Combined with LC-MS, it allows the detection of predicted metabolites by performing extracted ion current profiles... 

Figure 4.27 Measured SIMS and SSRM current profiles of a multiple-energy implanted 4H-SiC sample. The implanted dopant ion is Al and the activation after two annealing temperatures is shown. (From [122], 2003 Material Science and Engineering B. Reprinted with permission.)...

Figure 6.14. Cell Voltage vs. Cell Current profile of a hydrogen - oxygen fuel cell under idealized (dotted-dashed curve) and real conditions. Under real conditions the cell voltage suffers from a severe potential loss (overpotential) mainly due to the activation overpotential associated with the electroreduction process of molecular oxygen at the cathode of the fuel cell. Smaller contributions to the total overpotential losses (resistance loss and mass transport) are indicated.

Certain inspections may be required by program priorities even if a profile class code indicates an acceptable CGMP status. The current profile codes/classes for human drugs are ... 

The analytes are determined by acquiring a full mass scan and obtaining the extracted ion current profiles (EICP) for the primary mass-to-charge ratio and at least two secondary masses of each analyte. Ions recommended for this purpose are listed in the EMSL methods. 

Figure 9. Illustration of the use of extracted ion-current profiles obtained with LC-MS, moving-belt interface, for the detection of carbamate and other pesticides. T op, extracted ion-current profile for 17 major ions second from top, extracted ion-current profile for m/z = 151 to m/z = 181 third from top, extracted ion-current profile for m/z = 86 to m/z = 305 bottom, UV absorption detection at 220 nm. (Reproduced with permission from reference 53. Copyright 1982 Preston Publications.)...

Figure 12. Total ion-current profiles obtained with LC-MS, moving-belt interface, for the detection of carbamates and other pesticides. (Reproduced with permission from reference 53. Copyright 1982 Preston Publications.)...

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. 

Figure 2. GC/NICI-MS ion current profiles of secondary effluent and GAC-fUtered effluent. IS = internal standard decachlorobiphenyl.

Figure 4. GC/NICI-MS ion current profiles for 79Br and 81 Br in secondary effluent and GC-filtered effluent. Ion current ratios were as shown. Note peak labeled was not brominated (no m/z = 81).

Figure 5. GC/NICI-MS ion current profiles for 1271 in GAC secondary effluent and GAC-f titered effluent. Note peaks 1 and 4 increased after carbon contact. Both were silver labile (labeled ), whereas peaks 2 and 3 were not. The latter two components may not contain I but rather another ion of m/z = 127. Note early eluting (labeled ) components.

Figure 6. Effects of AgNC>3 on GC/NICI-MS ion current profile of secondary effluent. IS = internal standard. Peaks labeled ° in secondary effluent (GAC influent) were reduced or removed by AgNOs. Labeled peaks in bottom trace (AgNC>3 treated) were increased or created by AgNC>3...

Figure 7. Effects of AgNOs treatment on ion current profile of GAC filter effluent. IS — internal standard. Peaks labeled in untreated sample were removed or reduced by AgNO3. Peaks labeled in AgNC>3-treated sample were created or increased by the treatment.

Figure 8. Effects of AgNC>3 on GC-NICl ion current profiles of 35Cl and 37 Cl in GAC filter influent (secondary effluent) and effluent (GAC effluent). Peaks labeled in untreated effluents were reduced by AgNC>3. Peaks labeled m in AgNC>3-treated effluents were increased by Ag. (Continued on next page.)...

Figure 9. Effects of chlorination and AgN03 treatment on GAC filter effluent GC/NICI-MS ion current profiles for m/z = 35 and 79. Peaks labeled o in GAC traces were halogenated components decreased or destroyed by chlorination. Peaks labeled + in GAC-Ch traces were produced by chlorination. Peaks labeled 0 in GAC-Cfe traces were reduced by AgNQ3. Peaks labeled 0 in AgNQ3 traces were produced by AgNQ3.

---