Marker peak

Other polymeric binders, natural and synthetic, may be found as paints or varnishes in modern artworks and installations. Artists very easily adopt resins developed as industrial coatings or for specialized applications, and use them according to their creative needs. Natural rubber latex is a water dispersion of 1,4-ds-polyisoprene particles where pigments can be added to give coloured paints. By means of Py-GC/MS the presence of these paints can be easily assessed. As shown in Figure 12.13, the principal marker peaks in the pyrogram are those of isoprene, limonene and other cyclic dimers. 

Bone marker concentrations in urine and serum vary with the time of day because of the diurnal variation of bone resorption and formation. Because of the nocturnal peak in bone turnover, most bone markers peak in the early morning hours (4 am to 8 am) and reach their nadir in the afternoon (1 pm to 11 pm). The amplitude of this variation is greatest for resorption markers, with nadir values averaging 70% of peak values. Consequently, speci-... 

Fig. 17 Detection of B. anthracis from murine blood, (a) Detector responses during all three stages of sample processing and analysis are portrayed in terms of total analysis time. The SPE trace (green) was taken from off-line DNA extraction of the same murine sample and is representative of the total DNA concentration observed in a typical extraction. The temperature (blue) and fluorescence intensity (black) represent on-line data, with a total analysis time <24 min. Three sequential injections and separations were carried out to ensure the presence of amplified product, (b) Fluorescence data from an integrated analysis of a blank sample (no DNA) control with marker peaks labeled. The inset represents valve actuation during co-injection, with the PR and MR pumping inlets indicated by the arrows, (c) Zoomed view of the first separation shown in (a), with the product peak marked. The second and third runs are overlaid with the time axis cropped. Inset shows the sizing curve of inverse migration time vs. logfbase pairs) with both the sizing standard peaks (open diamonds) and product (square) plotted for all three runs shown in (a). From these data, the product was 211 2 bp. Reproduced from [10] with permission...

FIGURE 6 Refined praseodymium X-ray spectra showing the emergence of the low symmetry a-U phase. Copper pressure marker peaks are denoted by an asterisk and oxide peaks with o. (A) hR24 phase at 9.3 GPa. (B) a-U phase at 18.9 GPa, slightly above the transition pressure. Residual hR24 peaks are marked with arrows. (C) Pure a-U phase at 40.4 GPa (Cunningham et aL, 2005). 

FIGURE 20 X-ray diffraction spectra of Eu from 4 to 35 GPa with Rietveld full-profile refinements (red lines) for bcc and hep phases. Pt pressure marker peaks are identified by asterisks in all spectra (Bi et al., 2011). 

Column effects. In order to establish optimal operating conditions, it is useful to consider the effects of system parameters on the resolution characteristics of an HDC system. HDC has been described as a chromatographic method with very low capacity but very high efiBciency. For example, the calibration curves show that the spectrum of sizes from less than 100 nm to greater than 300 nm is encompassed in less than about 5% of the column void volume. On the other hand, the theoretical plate count corresponding to the marker peak is typically in the range of several thousand per foot. Comparisons in terms of the specific resolution factor, enable a more precise analysis, since both the separation factor and peak dispersion are included in its definition. A simple form for the specific resolution between two particle populations of diameter Dpi and Dp2 is [11]. 

For the differentiation of analyzed oil and testing, given the possibility of detecting the presence of vegetable oil blended with VOO, the authors propose the identification of TAG peaks using MS with positive APCI and the calculation of the peak area ratio values, dividing an indicator peak area by a marker peak area. The obtained results clearly show that the peak area ratio values of analyzed oil samples are markedly different and the adulterated VOO samples are detected. Thus, this method is able to detect VOO samples adulterated with 1% of soybean oil and walnut oil, or with 5% of hazelnut oil. The detection threshold for this method is much lower than other LC-MS methods developed previously. 

The series of well-defined sulfur marker peaks provides the data points on which the computer system performs a high-order polynomial fit to construct a mass axis calibration curve. The latter can then be used to convert experimentally measured intensity-time profiles to intensity-m/z plots (mass spectra). A caveat that should not be ignored is the formation of heteronudear species by gas-phase reactions of sulfur with other inorganic substances [13]. Even though none of these het-eronuclear species may exist in the solid state or in solution, their presence in the gas phase complicates mass spectra. 

On the other hand, some compounds containing a central metal atom in different oxidation states may generate marker peaks without the need to resort to a chemical ligand. For example, Aubriet et al. [24] and Hachimi and Muller [25] in their investigations on the ionization of Cr(III) and Cr(VI) oxides by a laser-... 

Fig. 8.6 Pseudo-gel view produced from 195 mass spectra of . faecium, among them are 29 strains of VSEfm (lines 1-87) and 36 strains of VREfm (lines 88-195). Among the VREfm strains 30 were of the vaw.4 (lines 88-177) and 6 of the vanB type (lines 178-195). The figure demonstrates the absence of vanA and variB marker peaks postulated by Griffin et al. (2012) in the mass spectra of the RKI strain collection. Arrows at m/z 5095 and 6603 denote the position of the proposed marker peaks...

Fig. 8.8 Pseudo-gel view of mass spectra from B. cereus sensu lato (s.l.) in the diagnostically relevant mass range of m/z 5000-8000. Mass spectra of the three elassieal speeies B. anthracis, B. cereus sensu strict, (s.s.), and B. thuringiensis consistently exhibit marker peaks at m/z 5171, 5886, 6263, 6835, 7082, 7368, and 7782. The peak at m/z 6679 has been suggested as a biomarker specific for B. anthracis-, however, there are a few strains of B. cereus in which the postulated biomarker was also observed (arrows 1 and2, see also the text for details)...

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