Multi-linear gradient elution optimization for separation of phenylthiohydantoin amino acids using pareto optimality method

Abstract

Multi-linear gradient elution was applied for simultaneous optimization of resolution and analysis times for ten phenylthiohydantoin amino acids (PTH-AAs) in liquid chromatography. Relation of lnK upon ij for each analyte was determined using isocratic retention time data, and gradient retention time of analytes was predicted using fundamental equation of gradient elution. Then a grid search program was used to predict retention time of solutes in variable space. Two different chromatographic goals-analysis time and minimum difference between adjacent peaks-were simultaneously evaluated using Pareto optimality method. Gradient program in optimum condition was: initially 24% CH 3 OH/Water for 10 min, linear ramp to 34% over 5 min, to 29% over 5 min, and to 70% over 20 min. The average of calculated relative error in the prediction of the retention time in optimal conditions was -1.67% that shows a good agreement between predicted and experimental values of the chromatographic retention time in optimal condition.

Enhanced selectivity and search speed for method development using one-segment-per-component optimization strategies

“…This software combines chromatogram simulation and fast Monte-Carlo optimization to optimize multi-linear gradients [19]. In 2006, Nikitas and coworkers reported on the use of Genetic Algorithms to optimize multi-linear gradients [20,21]. However, this optimization approach requires a priori selection of initial parameters such as the number of generations, the population size and the probability of mutation [20].…”

“…The best "traditional" multi-segment gradient profile (determined by a starting composition 0 and a value for ˇ and t G for each segment) was determined via a similar grid search. Based on our own findings and these of Concha-Herrara et al [12], only 4-segment gradients were considered as these give the best compromise between the achievable selectivity (in gradient elution this is the ratio between the apparent gradient retention factors k eff,1 /k eff,2 [16][17][18][19][20][21][22][23][24][25][26][27]) and the required search time. The grid search was conducted considering different starting concentrations %B between 5 and 95% (step size of 0.5%) and a number of ˇ-and t G -values for each of the 4 segments (ˇ going from 0.001 to 0.2, corresponding to 0.1 to 20%B/min, i.e., ln(ˇ) between −6.9 and −0.70 and t G /t 0 between 1 and 12).…”

Analysis of amino acids using serially coupled columns

“…The main problem is the inability to get sufficiently good resolution in practical analysis times, using conventional columns and instrumentation for HPLC. It is thus not surprising that a number of authors have been interested in developing optimisation protocols to improve the chromatographic performance in amino acid analysis . The most successful optimisation strategy is the in silico scanning of the performance of a large number of arbitrary conditions by inspecting their computer‐predicted chromatograms .…”