Common peak

The most common chromatogram in the distilled spirits industry is the fusel oil content. This consists of / -propyl alcohol, isobutyl alcohol, and isoamyl alcohol. Other common peaks are ethyl acetate, acetaldehyde, and methanol. The gc columns may be steel, copper, or glass packed column or capillary columns. Additional analyses include deterrninations of esters, total acids, fixed acids, volatile acids, soHds or extracts (used to determine... 

What are the common peak shapes, and why it is necessary to know the peak shapes before applying apodization ... 

When the individual insecticides are present in the solution in such a concentration range, the electron capture responds nearly uniformly to all insecticides. A column filled with 1.5% silicone OV-17 plus silicone oil (fluoralchylsiloxane) on Chromasorb W (80-100 mesh) is used for separation of the BHC alpha, beta, gamma and delta isomers (hexachlorocyclohexane), o,p -DDT, p,p -DDE, p,p -DDD, and p,p -DDT. a-BHC and hexachlorobenzene (HCB) have a common peak. They can be separated on a column filled with 2.5% Silicone Oil XE-60 (Is-cyanoethyl-methylsilicone) on Chromosorb W (80-100 mesh). 

Laser Flash Photolysis at 248 nm of TDI-PU. MDI-PUE. and Model Compounds. Figures 1 and 2 show the transient absorption spectra of MDI-PUE (5.5 X lO-3 g/dL) and TDI-PU (2.3 X 10 3 g/dL) in THF at a 2.0 ns delay after pulsing with a krypton fluoride excimer laser (Xex=248 nm) in air and nitrogen saturated samples. Both spectra have common peaks in nitrogen saturated solutions (shown by arrows) at 310 nm, 330-360 nm (broad), and above 400 nm (broad, diffuse absorbance).. The MDI-PUE sample has an additional and quite distinctive peak at 370 nm. In the presence of air, the peak at 370 nm for MDI-PUE is completely extinguished, while the sharp peaks at 310 nm for TDI-PU and MDI-PUE and the broad band above 400 nm are only marginally quenched by oxygen. 

After completing this series of experiments and finally optimizing an LC separation, the determination of which impnrities to monitor can begin. The primary purpose of this exercise is to determine which impnrities are likely to be found in production-scale batches. This process begins with the evalnation of all of the degradation chromatograms to identify common peaks. Where common peaks are found, they should be added to the list of impurities to be characterized and potentially limited. 

No such stabilization is present in the 1,2-dimethyl-2-norbomyl cation and the proton spectrum does not permit a choice because the exo- and enrfo-6-protons exhibit a common peak. The methyl groups also afford a single non-resolvable b[Pg.219]

Figure 11.4 MS spectral signatures for selected explosives. Each compound gives a unique spectrum. Nitrate esters all have a common peak at m/z 62.

Most 2H-imidazoles show a parent ion that can be quite prominent.The major fragmentation pathway involves loss of RCN (two possible ways when the C-4 and C-5 substituents are different) and often gives rise to the base peak. Thus the 4-phenyl compounds show a prominent Mt — 103 ion, and structures 51 a common peak at m/e 145 (Mt -RCN). " °... 

The complete powder XRD profile (either for an experimental pattern or a calculated pattern) is described in terms of the following components (1) the peak positions, (2) the background intensity distribution, (3) the peak widths, (4) the peak shapes, and (5) the peak intensities. The peak shape depends on characteristics of both the instrument and the sample, and different peak shape functions are appropriate under different circumstances. The most common peak shape for powder XRD is the pseudo-Voigt function, which represents a hybrid of Gaussian and Lorentzian character, although several other types of peak shape function may be applicable in different situations. These peak shape functions and the types of function commonly used to describe the 20-dependence of the peak width are described in detail elsewhere [22]. 

The mass spectra of l,2,4-triazolo[4,3-a]pyrimidines showed, mainly, their molecular ion peaks [83S44 88JCS(P1)351 94LA1005]. The mass spectra of l,8a-dihydro-l,3,7-trisubstituted-l,2,4-triazolo[4,3-a]pyrimidines 41 revealed a common peak of the nitrileimine 159 (94LA1005). 

The mass spectrum of camphor shows the common peaks of isoprene m/e 27, 29, Ul, 53, 67, 68. There are also the molecular ion (M+ 152) and the base peak m/e 95 (CjHip ). The base peak is probably formed as follows ... 

The thiohydantoin-amino acid standard HPLC chromatogram (Figure 1) shows the elution times for each of the 20 common amino acid derivatives (approximately 50 pmols) including thiohydantoin-Pro (P) and the common peak designated S/C, identifying Ser and Cys residues. The relative retention time for the S-carboxymethyl derivative of cysteine is indicated by the arrow. 

Figure 15.15. Comparasion of MALDI spectra of E. coli (strain ATCC 11775) grown in different laboratories, under the same experimental conditions. The asterisks on the bottom trace indicate common peaks in the two spectra.31,32 [Top trace reprinted, with permission, from Z. Wang, L. Russon, L. Li, D. C. Roser, and S. R. Long, Rapid Communications in Mass Spectrometry 12, 1998, 456 -64. Investigations of Spectral Reproducibility in Direct Analysis of Bacteria Proteins by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry . 1998 John Wiley Sons, Ltd. Bottom trace reprinted, with permission, from Catherine Fenselau and Plamen A. Demirev, Mass Spectrometry Reviews 20, 2001, 157-171. Characterization of Intact Microorganisms by Maldi Mass Spectrometry. Copyright 2002 by John Wiley Sons, Inc.]...

Panel a illustrates the variation of fraction cubic ice as a function of droplet size. The horizontal bars indicate the size range in which 68 % of the droplet volume resides. Panel b illustrates the relationship between the fraction of cubic ice and the ratio of the intensities of the hexagonal peak at 44° and the common peak at 40°. The solid line represents the relationship between Uf cind the amount of cubic ice assuming that the fraction cubic ice = 1-fraction hexagonal = l-fUf l4o)/0.79). 

Schematic representation of the split Pearson VII profile (SP7) with six parameters common peak position 20 and peak height but separate half widths FWHM and slope parameters m for the left and right peak moieties. (After Kern, 1992. )...

Helline billiardieri afforded two new alkaloids, phellibilidine (69) and isophellibilidine (70), respectively (26). The mass spectrum of 70 shows it to be isomeric with 69 (C17H23NO4). Moreover, several common peaks were found in the spectra of 69 and 70, indicating the same partial structure. The IR absorption at 3380 cm for 70 agrees with the presence of a hydroxy group the absorption at 1745 cm can be attributed not to an unconjugated ester or S-lactone but rather to an a./S-unsaturated... 

The appearance of common peaks for tetragonal and monoclinic vanadium-doped zirconias suggests that identical electrochemical pathways are operative for vanadium centers in these materials. Additional peaks recorded in t-V ZrOj materials can be attributed, however, to vanadium centers with a coordinative arrangement characteristic of tetragonal zirconias. 

Figure 4 illustrates the CD spectra of a few rhodium (I) complexes. The pattern is very much dependent on the other ligands. Two charateristic and common peaks are seen in the two regions, where the r 2-olefins cause absorption peaks i.e. negative peaks between 20,000 and 30,000 cm-l and large positive peaks at oa. 

Comparison of the mass spectrum of securinol A with that of securi-nine (Section II, C) showed the presence of a common peak at m e 84 as expected for a hare tetrahydropyridinium ion. The most important peak in securinol A was observed at m/e 191 (m 155.2) assignable to the ion 159 formed by loss of CH2=CHOH. The presence of an m/e 44 peak in securinol A and its absence in securinine and dihydrosecuri-nine gave assurance that the ion at m/e 191 was not due to loss of C02-Reference to literature examples leads to the most reasonable interpretation of this fragmentation as shown (158 — 159) and thus fully supports the assignment of a C-15-OH function in securinol A (157) which may now be named 14,15-dihydroviroalloseourinin-15a-ol. 

We shall first examine the reaction chromatographic method in which the derivatives formed are not analysed and the reaction is assessed by the variation of the concentration of the sample compounds in one of two phases that are in equilibrium. This combined distribution-chromatographic method makes it possible to measure quantitatively the contents of components in a common unresolved peak. As an example we can cite the determination of isobutene and butene-1, which are not separated on most stationary phases, in a common peak. First the phase distribution of components in the sample was established in a liquid—vapour system at 20°C, with silver nitrate solution in ethylene glycol as the liquid phase. The distribution coefficients for isobutene and butene-1 in... 

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