Tivadar Farkas

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A variety of complementary evidence reviewed here demonstrates that the packing of chromatographic columns is heterogeneous. It is denser and less well organized close to the column wall than in the center of the column. The mechanism of particle consolidation under stress explains the origin of this phenomenon and provides a fundamental justification to(More)
The separation of enantiomers of ten chiral arylpropionic acid derivatives was studied on six different polysaccharide-based chiral HPLC columns with various normal-phase eluents. Along with the successful separation of analyte enantiomers, the emphasis of this study was on the effect of the chiral selector and mobile phase composition as well as of the(More)
Three polysaccharide-derived chiral stationary phases (CSP) were evaluated for the resolution of more than 200 racemic compounds of pharmaceutical interest in the reversed-phase (RP) separation mode. The population of test probes was carefully evaluated in order to insure that it covers as completely as possible all structural diversity of chiral(More)
A series of experiments and measurements demonstrate the importance of minimizing the extra-column band broadening contribution of the instrument used. The combination of several measures allowed the achievement of the full potential efficiency of three Kinetex-C(18) columns, using a conventional liquid chromatograph. The first measure consists in(More)
Structural multiplicity has a significant effect on the solution of an MINLP model for process synthesis problems. The optimization model may also have built-in redundancy that cannot always be directly derived from the multiplicity of the superstructure. A basic GDP representation (BGR) involving logical relations is defined, and can be constructed by(More)
This article reports comparative high-performance liquid chromatographic separations of enantiomers with chiral stationary phases (CSPs) prepared by coating cellulose tris(4-chloro-3-methylphenylcarbamate) on totally porous and on core-shell type silica of comparable particle diameter. Several interesting observations were made: (1) the selectivity of(More)
A new hybrid optimisation method is presented, that is fairly robust and can be accomplished in an automatic way. The main idea is using integer cuts and bounds, calculated based on driving force plot analysis, for the lean streams to decrease the possibility of being trapped in local optimum. A new initial solution is constructed only if the MINLP solution(More)
The essential problems, namely representativeness and uniqueness, in defining mixed integer non-linear programming (MINLP) representation (MR) is solved in Part I by first defining a basic MR (BMR) that: (1) can be automatically constructed from an easier formable standard GDP representation and (2) serves as a reference representation. Binary and(More)
In this study two types of silica particles, one fully porous and the other superficial porous (core-shell or fused-core) were modified with a polysaccharide-type chiral selector and evaluated for the separation of enantiomers in nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC). The major goal of this project was to critically(More)
Photo- and thermal-degradation studies on eccrine fingerprint components are presented herein. Dilute distinct solutions of urea, lactic acid, and seven amino acids were deposited on steel coupons and Teflon disks, exposed to artificial sunlight or heat, extracted, and analyzed. This aim of this study was to determine whether the investigated eccrine(More)