Time-integrated absorbance spectrum

Figure 4.8 shows an example for this mode of correction applied for the determination of Pb in pig kidney reference material, using direct solid sample analysis. The three-dimensional plot in Figure 4.8a shows that a strong molecular absorption with pronounced fine structure appears short after the atomic absorption signal. Figure 4.8b shows the time-integrated absorbance spectrum of PO,... 

Figure 5.7 Time-integrated absorbance spectrum, calculated from Figure 5.6 analyte wavelength position dashed line...

Figure 8.33 (continued) (b) time-integrated absorbance spectrum lead wavelength at 217.001 nm is indicated by the dashed line time delay after onset of the atomization cycle 1.5 s ... 

In LS GF AAS, according to the Stabilized Temperature Platform Furnace (STPF) concept [133], signal evaluation should be done exclusively by means of time-integrated absorbance, the so-called peak area value. Applying this principle to HR-CS GF AAS, a spectrum is obtained which is summed over time, whereby the integrated absorbance at individual pixels A is calculated by ... 

Preferably, the molecule reference spectra, at least those of the most notorious troublemakers, such as PO and NO (refer to Chapter 7), should be pre-recorded with a good SNR and stored in a library. Fortunately, identification of the molecule responsible for the specific fine-structured background is not in all cases necessary, since a reference spectrum can be generated from the measurement itself, when the molecular structure can be separated from the analyte signal in time. By limiting the number of scans to the time interval of the presence of the unknown molecular structure, a reference spectmm can be obtained when calculating the time-integrated absorbance from the selected scans. 

To experimentally probe the CO trajectory after dissociation, ultrafast time-resolved polarized mid-IR spectra of photolyzed h-MbCO in G/W were recorded (34), the results of which are plotted in Fig. 8A. This study was performed in G/W primarily because the flatness of the solvent absorbance spectrum near 2100 cm-1 minimizes temporal distortion of the transmitted femtosecond IR probe pulse, thereby maximizing the effective time resolution of the measurement. Two features are already apparent at 0.2 ps, the earliest time shown, and these features rapidly develop into the docked states denoted Bi and B2. The development of the docked CO spectrum is further quantified by the time dependence of the polarization anisotropy, as defined in Equation (2). The B and B2 polarization anisotropies, plotted in Fig. 8B, evolve exponentially with time constants of 0.20 0.05 ps and 0.52 0.10 ps, respectively, and converge to the same anisotropy of approximately 0.2. According to Fig. 8C, ligand translocation is accompanied by a 1.6 0.3 ps growth of the integrated isotropic B-state absorbance. 

Figures 2B-E show Che IR-ER spectra for a 170 10 nm cellulose acetate film at GC as a function of hydrolysis time. Figure 2B is the spectrum of the film prior to hydrolysis. Figures 2C-E are IR-ER spectra for the film at hydrolysis times of 40, 50, and 80 min, respectively. Optical dispersion effects, which are enhanced due to the low IR reflectivity of materials such as GC, cause the observed band-shape distortions in the reflection spectra (38)- I or short Immersion times ( 40 min), the changes in the absorbances for Che acetate marker bands (1731 and 1234 cm ) suggest a reaction mechanism that is consistent with the hydrolysis of an ester. For example, at an immersion time of 40 min the integrated absorbances of the acetate markers decrease by about 3SZ whereas chat for Che marker for the polymeric backbone (1052 cm ) decreases only by 14Z. Althou not shown in the figure, the decrease in the acetate composition of the film is accompanied by an increase in the number of hydroxyl groups of the film. These data indicate that at short immersion times the composition of the film evolves from Chat of cellulose acetate to one which is more "celluloslc" in nature.

Figure 838 Time-integrated spectra in the vicinity of the aluminum line at 309.271 nm (a) emission spectrum of an aluminum single-element hoUow cathode lamp lamp current 23 rtiA (b) absorbance spectrum of a seawater sample sample volume 25 pL, atomization temperature 2500 °C...

Figure 4.8. Least-squares BC for molecular spectra with rotational fine structure determination of Pb in the BCR 186 Pig Kidney CRM at 217.001 nm using HR-CS ET AAS and direct solid sample analysis (a) absorbance over time and wavelength after correction for continuous absorption (b) reference spectrum absorbance over wavelength integrated over time for NH4H2P04 (the dotted line represents the center pixel) (c) absorbance over time and wavelength after subtraction of the reference spectrum using least-squares BC.

For each solution in the Cr + G series, Table 8.2 (1) measure the UV-vis spectrum to obtain the absorbance A at Aex, and (2) measure an emission spectrum and obtain the integrated emission intensity, I. Also, prepare a solution having [G] the same as the last in your series (Table 8.2), but with no chromium complex. This will serve as a control sample. Save your sample solutions for time-resolved luminescence quenching if you are conducting these experiments (see below). Save all UV-vis and luminescence spectra files that you acquire—they may be useful for data analysis. 

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