Unresolved peaks, problems with

The next section is a summary of the bioavailability/pharmacokinetic data and the overall conclusions. The summary should include a table with the following pharmacokinetic parameters peak concentration (Cmax), AUC, time to reach peak concentration (Tmax), elimination constant (kel), distribution volume (Vd), plasma and renal clearance, and urinary excretion. Overall conclusions as well as any unresolved problems should be discussed. 

A still unresolved problem in gc is the allocation of the areas of overlapping peaks with the same precision as areas of isolated peaks. Since the relative standard deviation of gc is in practice often better than 1 % and optimally better than 0.1%, it is desirable to use peak-area determinations having smaller systematic errors and deviations than 0.1% for overlapping peaks, too. It is still a challenge to mathematicians to seek general algorithms which satisfy the above conditions. 

Figure 7.19 shows the chromatogram of a test mixture of nine PAHs. At 30°C, the mixture was unresolved and all peaks showed bad symmetry and efficiency, especially for the most hydrophobic solutes (peaks 4-15). At 40°C, the separation was still poor. At 50°C, the improvement was evident, the efficiency of the separation of peaks 8-15 increased considerably. The best situation occurred at 60 C, where the mixture was totally resolved and the analysis time diminished in comparison with the initial situation at 30°C. The enhanced silica dissolution is a problem that should not be neglected when working at elevated temperature with micellar phases. 

Numerical reactive hydrodynamic codes such as SIN, TDL or 2DE include the Forest Fire decomposition rate. For unresolved burns, it is necessary for the decomposition front of a detonation wave to occur over several computer meshes or cells so that the physics of the flow, the shock jump conditions, are properly described. Historically this was accomplished by adjusting the artificial viscosity so that the burn occurred over about 3 cells. If the mesh size changed, a new viscosity coefficient was determined empirically that would result in a realistic burn. As shown in the movie on the CD-ROM at /MOVIE/VISC.MVH, if there is insufficient viscosity, one obtains a reactive front with a peak that oscillates. If there was too much viscosity, a flat pressure profile occurs at the front. The problem is not unique to Forest Fire as other burn rates such as Arrhenius have the same numerical problems when numerically unresolved in reactive hydrodynamic codes. 

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