Resolving of Overlapping Asymmetrical Chromatographic Peaks by Using Wavelet-Transform and Gram-Charlier Peak Model

The paper describes a method for resolving overlapping asymmetric peaks that make up a chromatogram. The presented method uses the Gram-Charlier model in the form of the first three terms of the Gram-Charlier series as a basis. Using the wavelet transform, the parameters of this model are determined, which is used to describe a single or overlapping chromatographic peak. Hermitian wavelets of the first four orders are used in the computation of the wavelet transform. To speed up the computation of multiple wavelet transforms, the possibility of coding a signal using the Chebyshev-Hermite functions is considered in order to further restore the set of wavelet transforms simultaneously. According to the presented method, the parameters of the peaks are determined by analytical expressions without using the numerical approximation of the chromatogram by the peak model, which avoids the disadvantages of the numerical approach. The resulting method is used to resolve overlapping asymmetric peaks. The advantage of the method over others is shown by calculating the area of each of the resolved peaks.

Removal of Cresols From Water By Packed Beds of Cyclodextrin-Based Hydrogels

A cyclodextrin-based polymer was prepared by crosslinking β-cyclodextrin with epichlorohydrin to be assessed as a sorbent material for cresols in packed-bed columns. Both Langmuir and Freundlich isotherms were appropriate to describe the sorption equilibrium in the conditions tested, and the thermodynamic parameters obtained for this process confirmed its exothermic nature with similar enthalpies (between −6.8 and −8.3 kJ/mol) for the three isomers. The removal of cresols from water was carried out in nine cycles of sorption-desorption in fixed-column experiments with the cyclodextrin hydrogel, achieving sorption capacities of 6.2, 11.6, and 15.1 mg/g for o-, m-, p-cresol, respectively. The experimental data for the breakthrough and the elution curves have been successfully modeled by two effective two-parameter equations, a dose-response model for the sorption step and a pulse-peak model for the regeneration step. The cyclodextrin polymer matrix has been proven to be an effective a good sorbent material for removing cresols from water, exhibiting remarkable reusability performance and structural stability throughout the successive elution steps carried out with methanol.

STUDY OF EFFECT OF CONSECUTIVE HEATING ON THERMOLUMINESCENCE GLOW CURVES OF MULTI-ELEMENT TL DOSEMETER IN HOT GAS-BASED READER SYSTEM

The objective of this paper is to study the effect of consecutive heating of TL elements of a thermoluminescence dosemeter (TLD) card in hot N2 gas-based TLD badge reader. The effect is studied by theoretical simulations of clamped heating profiles of the discs and resulting TL glow curves. The simulated temperature profile accounts for heat transfer to disc from hot gas as well as radiative and convective heat exchanges between the disc and the surrounding. The glow curves are simulated using 10 component glow peak model for CaSO4:Dy using the simulated temperature profile. The shape of the simulated glow curves and trend in total TL signal of the three discs were observed to match closely with the experimental observations when elevated surrounding temperature was considered for simulation. It is concluded that the readout (heating) of adjacent TLD disc affects the surrounding temperature leading to the changes in temperature profile of the next disc.