Quench interference/correction

The method of symmetric points was used to determine the center of the interference curve. Extensive calculations showed that the line profile should be symmetric about the center frequency. The line center was then corrected for the second order Doppler shift, The Bloch-Siegert and rf Stark shifts, coupling between the rf plates, the residual F=1 hyperfine component, and distortion due to off axis electric fields. A small residual asymmetry in the average quench curve was attributed to a residual variation of the rf electric field across the line and corrected for on the assumption this was the correct explanation. Table 1 shows the measured interval and the corrections for one of the 8 data sets used to determine the final result. 

With HTRF, the only possible interferences that are not easily corrected are due to the inner filter effect at the acceptor emission wavelength. However, only very few compounds in the hbraries absorb highly in the near infrared region. Possible cryptate quenching is even corrected to a certain extent by the signal ratio, while only acceptor quenching is not taken into account, similar to the situation with the other technologies. 

Analytical Procedure. Method for Determination of AA. Residual AA was determined immediately after irradiation by spectrophoto-fluorometry. In general the solutions were acidified to pH = 2.8 and analyzed using AeXit = 342 and Aemit = 428 m/x. To avoid quenching of the fluorescence because of AA, the irradiated solutions were diluted to an initial concentration of 2 X 10"5M AA. In experiments with nitrate, residual AA was determined by two different spectrophotofluorometric procedures. In the first method, carried out as described above, it was necessary to correct for a decrease in fluorescence caused by radiation induced nitrite which slowly diazotized AA. This reaction was followed with time and AA at the time of acidification was determined by extrapolation. In the second method, AA was determined by fluorescence assay of the diluted neutral solution (AeXit = 290 m/x and Aemit = 340 m/x). The radiation products (aniline 3-hydroxy- and 5-hydroxyanthranilic acid) did not interfere in either method, and both gave the same value for residual AA in the irradiated solutions (33). 

Light is produced, and sometimes quenched, by processes illustrated in Fig. 48.22. Since the sample is dissolved in the scintillator, there is no attenuation of the radiation on the way to the detector. Unfortunately, having the sample in the detector may interfere with scintillation. Most commercial systems can sense and correct for this quenching. Typically, a small peUet... 

Neilson and Holland [9] associate the amorphous phase absorption of polyethylene at 1368 cm (7.31 pm) and 1304 cm (7.69 pm) with the trans-trans conformation of the polymer chain about the methylene group. Therefore, the intensities of these two absorptions are proportional to one another. By placing an annealed film (approximately 0.3 - 0.4 mm) of high-density polyethylene (HOPE) in the reference beam of a double beam spectrometer and a thin, quenched film of the sample in the sample beam, most of the interference at 1368 cm (7.31 pm) can be removed. The method has the advantage that it is not necessary to have complete compensation for the 1368 cm (7.31 pm) band since a correction for uncompensation at 1378 cm (7.25 pm) can be applied based on the intensity of the 1368 cm (7.31 pm) absorption. 

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