Literature

DryLab draws on the philosophy described in the three most famous Solvophobic Theory papers IIIIII of Csaba Horváth, which were developed in the years 1975-1977 at Yale University (see also literature by Dr. Imre Molnár). Read more about the Fundamentals of DryLab...

Keyword Year

Optimizing Selectivity During Reversed-Phase HPLC Method Development: Prioritizing Experimental Conditions

L.R. Snyder, J.W. Dolan
 J. Chromatography , 1302, 45–54 (2013)

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http://doi.org/10.1016/j.chroma.2013.05.082

Several different conditions can be varied to improve selectivity for reversed-phase chromatography (RPC). A reexamination of literature data suggests that changes in selectivity due to a change of column or mobile phase pH are largely replicated by changes in temperature or mobile phase composition (concentrations of acetonitrile and/or methanol). This suggests a reconsideration of the role of mobile phase pH and the column during method development.


Exploring better column selectivity choices in ultra-high performance liquid chromatography using Quality by Design principles

Róbert Kormány, Imre Molnár, Hans-Jürgen Rieger
Journal of Pharmaceutical and Biomedical Analysis, 80, 79-88 (2013)

Keywords: Amlodipine, DoE, DryLab, QbD, UHPLC-column comparison

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http://dx.doi.org/10.1016/j.jpba.2013.02.028

An older method for amlodipine was reworked with the goal to reduce the analysis time of 60min below 6min. To select the best column for short and robust analysis, 9 different UHPLC column chemistries were investigated using 3-dimensional resolution spaces based on 12 experiments using DryLab4 modelling software. The main variables used were gradient time (tG), temperature (T) and the pH of eluent A. The best critical resolution was calculated and located in a 3-dimensional space in an automated fashion and the corresponding best experiments were carried out. The work (9×12=108 runs) for DryLab4 modeling was finished with an UHPLC instrument in less than 24h. The comparison between predictions and real experiments showed an excellent correlation with differences typically less than 0.04min (<3s) in average, although the set points were located at quite different conditions on gradient times, pH's and temperatures for the individual columns. With the support of DryLab4 all columns could perform the required baseline separation at their individual best working points with satisfactory results.


Determination of alcohols in essential oils by liquid chromatography with ultraviolet detection after chromogenic derivatization

J. Ródenas-Montano, E.J. Carrasco-Correa, M. Beneito-Cambra, G. Ramis-Ramos, J.M. Herrero-Martínez
 J. Chromatography, 1296, 157-163 (2013)

Keywords: Essential oils, Alcohols, Chromogenic derivatization, DryLab, HPLC-UV

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An HPLC-UV method to determine compounds having a hydroxyl functional group in plant essential oils is developed. Separation conditions were optimized using the DryLab® method development software, a large sensitivity enhancement was obtained.


Determination of the design space of the HPLC analysis of water-soluble vitamins

H.A. Wagdy, R.S. Hanafi, R.M. El-Nashar, R.M., H.Y. Aboul-Enein
J. Sep. Science, 36, 11, 1703-1710 (2013)

In this work, DryLab is used to accurately determine the design space for critical resolution in the analysis of water-soluble vitamins by HPLC. The multifactorial optimization of three measured parameters (gradient time, temperature, ternary eluent composition (B1/B2)) and seven calculated ones (flow rate, column length, column internal diameter, dwell volume, extracolumn volume, %B [start], and %B [end]) are illustrated. DryLab is used to examine multifactorial effects of these 3+7 parameters on critical resolution and selectivity. Multidimensional robust regions of high critical Rs were defined and graphically verified. The optimum method was selected based on the best resolution separation in the shortest run time. Predicted retention times of all peaks were found to be in excellent match with the virtual ones.


Comparison of supercritical fluid chromatography and reverse phase liquid chromatography for the impurity profiling of the antiretroviral drugs lamivudine/BMS-986001/efavirenz in a combination tablet

A.J. Alexander, L. Zhang, T.F. Hooker, F.P. Tomasella
J. Pharm. Biomed. Anal, 78-79 , 243-251 (2013)

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http://doi.org/10.1016/j.jpba.2013.02.019

Dual and triple combinations of antiretroviral drugs are a cornerstone of human immunodeficiency virus type 1 (HIV-1) treatment. Supercritical fluid chromatography (SFC) and reverse phase liquid chromatography (RPLC) methods have been developed for the impurity profiling of a prototype combination tablet containing three such drugs: lamivudine, BMS-986001 and efavirenz. This combination of mobile phase additives was required for both the separation of minor components and to minimize peak tailing of the active pharmaceutical ingredients (APIs). Separation by RPLC was achieved using a Discovery HSF5 stationary phase and a mobile phase consisting of 10 mM ammonium acetate, pH 5.5 and methanol. Mobile phase gradient elution was employed in each case to elute components with a wide range of polarities. Both these methods were found to have advantages and disadvantages. Out of the three APIs and 13 possible impurity/degradation products selected, all were resolved by RPLC using DryLab


Classification of LC columns based on the QSRR method and selectivity toward moclobemide and its metabolites

A. Plenis, I. Oledzka, T. Baczek
J. Pharm. Biomed. Anal, 78-79 , 161-169 (2013)

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http://doi.org/10.1016/j.jpba.2013.02.020

The rapid development of the reversed-phase liquid chromatography (RP-LC) nowadays has elevated this particular separation technique to the position of one of the most powerful analytical methodologies used for drug analysis. On the other hand, many analysts confront the problem of selecting the appropriate column because their nominally identical structures may suggest similar chromatographic properties. For this reason, general test methods to characterize RP-LC columns have been extensively studied since the 1970s with support of DryLab. Interesting approach namely a quantitative structure-retention relationships (QSRR method) was published by Kaliszan et al. 


Intergroup cross-comparison for the evaluation of data-interchangeability from various chromatographic tests

C.Chamseddin, I.Molnár, T.Jira
J. Chromatogr, 1297, 5 July, 146-156 (2013)

Keywords: Stationary phase classification, Tanaka, USP, Snyder–Dolan, Calixarene- and resorcinarene-bonded phases

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http://doi.org/10.1016/j.chroma.2013.04.081

The recently dramatic increase in the available choices of reversed-phase columns could be an advantage of this mode of separation. However, due to the insufficiency of available information in terms of the exact functionality of these phases and the similarities and differences between these newly introduced and conventional reversed-phase columns, it is now somehow problematic to determine which could be the best column for a given analytical problem. There is no single column that will give us a good separation for all applications. As a result, there have been several attempts to develop testing strategies to characterize column chemistries. In this study three of the most widely used and acceptable approaches for the characterization of reversed-phase columns, which are Tanaka, United States Pharmacopeia (USP), and Snyder–Dolan, are systemically applied to investigate the chromatographic properties of calixarene- and resorcinarene-bonded stationary phases, polar-embedded and polar-endcapped stationary phases, phenyl and ether-linked phenyl with the presence of conventional alkyl-bonded phases (octyl- and octadecylsilane). Although all column classification systems aim to evaluate "more or less" the same characteristics, each system uses different test mixtures in different chromatographic conditions. It is therefore very important to evaluate the similarities and differences in the resulted "column parameters" and the possible interchangeability of them. The results of this comparative study show that the used parameters of Tanaka and of Snyder–Dolan have in many cases a good to very good correlation. The USP approach, which is based on single run, is related to Tanaka and Snyder–Dolan only in terms of hydrophobic characters, and no relation could establish in the other parameters. The hydrophobic-subtraction model could be extended to describe the ligand–solute interactions of calixarene- and resorcinarene-bonded stationary phases, which are belonging to reversed phase material. However they show, depending on the analytes, some additional interactions, since their steric, polar and ionic properties are different compared to those of conventional alkyl-bonded phases.

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