True profile

The form of the isotherm need not be Langmuir in nature, but in any event, must be experimentally determined in order to identify the true profile of the overloaded peak. In practice, the determination of the adsorption isotherm of each compound to be separated by a preparative chromatographic procedure can be arduous and time consuming. A better alternative might be to design the fully optimized column from basic principles in the manner previously described. 

True profile analysis requires scanning over the whole mass range for the acquisition of all data on excreted compounds. Quantitation has been more challenging on a quadrupole instrument because total ion current peaks are seldom a single component and extracted-ion chromatograms (EICs) when recovered from scanned data are of poor quality due to the lower sensitivity of scanning GC-MS. Thus, we developed profile analysis based on SIM of selected analytes but tried to ensure the components of every steroid class of interest were included. For ion traps the fundamental form of data collection (in non-MS/MS mode must be full -scans). Thus, the quantitative data produced are EICs obtained from scanned data. The EICs are of the same ions used for SIM in quadrupole instruments and the calibration external standards are the same. 

In emission spectroscopy, we measure emitted irradiance rather than the fraction of incident irradiance striking the detector. Detector response varies with wavelength, so the recorded emission spectrum is not a true profile of emitted irradiance versus emission wavelength. For analytical measurements employing a single emission wavelength, this effect is inconsequential. If a true profile is required, it is necessary to calibrate the detector for the wavelength dependence of its response. 

Since the measured profile is a convolution of the true profile with the optical PSF (which can be calculated), we have an opportunity to improve the fidelity of the profile by deconvolution. If Px(x, y) is known or can be determined, then the... 

The second term between the square brackets contains straight d s. Now we use the condition that a = 0 in the term between squeu e brackets on the r.h.s. As this situation refers to the true profile we may replace p and p by p and p, respectively. So our condition for the true function becomes... 

E(u,v) is the inner product of u and v. In conventional OCFE calculation methods, the exponent of Az in Eq. 10.112 is 6, hence the degree of convergence between the calculated and the true profiles is of the sixth degree with respect to the space increment. One expects the value of C I4 to be rather small in the type of problems dealt with here. The fourth-order Runge-Kutta method used in the OCFE algorithm discussed here introduces an error of the fifth order. Accordingly, we may anticipate that the numerical solutions of the system of partial differential equations of chromatography calculated by an OCFE method will be more accurate than those obtained with a finite difference method [48] or even with the controlled diffusion method [49,50]. 

The measured peak absorption coefficient, Kmax, for a discrete impurity transition depends on the oscillator strength of the transition and on the impurity concentration. The measured profile of a recorded line is the convolution product of its true profile by the instrumental function of the spectroscopic device used. It depends significantly on the ratio of the true FWHM of the line to the spectral resolution (the spectral band width) of the spectroscopic device. When this ratio is of the order of 3 or above, the measured FWHM can be considered as the true FWHM and the observed profile is close to the true profile. For lower values of this ratio, the measured FWHM increases steadily while the measured value of Kmax decreases, and it is assumed that when the ratio becomes l/3 or smaller, the measured FWHM is the spectral resolution and the measured profile the instrumental function. This effect is known as instrumental broadening. For isolated lines, the absorption coefficient can be integrated over the entire line to give an integrated absorption I A ... 

There are some further steps, which should also be included, and are quite straightforward in practice. The true profiles of the absorption lines are not Lorentzian, as assumed in the simple theory above, but are broadened by the Maxwellian velocity distribution ... 

Overall, the moving reference datum level devices are low-cost devices, are easy to operate and can easily locate bumps. However, the operating speed is, as in Dipstick and walking profilers, slow, does not provide a true profile and lacks precision. 

The lightweight profilometers cost less than high-speed profilometers, measure true profile, are flexible to use and are ideal for quality control measurements during paving operations. However, they require certain traffic control during operation, lack reproducibility and are not really suitable for network roughness surveys. Some relevant information can be found in Mondal et al. (2000). 

Figure 8. Model film geometries to study photoresist roughness, (a) Single layer with resist and/or blend of protected and deprotected components with additives, (b) This work, bilayer with deprotected bottom layer and top deprotected PAG feeder layer, (c) True profile prepared with mask to study resist performance.

Taylor, A.J., R.S.T. Linforth, I. Baek, M. Marin, M.J. Davidson, Flavor analysis under dynamic conditions measuring the true profile sensed by consumers, in Frontiers of Flavour Science, RE. Schieberie, K.H. Engel, Eds., Deutsche Forschung. Lehensmit., Garching, 2000, p. 255. 

Figure 6.4 (a) Schematic illustration of the relation of true profile and correction bz (of feedback loop applied to keep the cantilever bend-... 

---