Literature

So far, more than 230 peer reviewed papers have been published on the application of DryLab – a complete list of which you can find here.

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 and its History.

Keyword Year

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

PDF
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.


A High-Performance Liquid Chromatographic Method for Simultaneous Determination of 21 Free Amino Acids in Tea

M. Zhao et. al
Food Analytical Methods, 6, 1, 69-75 (2013)

http://link.springer.com/article/10.1007/s12161...

Free amino acids are closely related to the savory taste and beneficial effects of tea, and high-performance liquid chromatography (HPLC) is the most widespread analytical approach for simultaneous determination of free amino acids in tea. However, the reported HPLC methods have drawbacks such as long run times, low resolution, or poor efficiency. In this study, a special amino acid analysis column was used to separate and verify 21 amino acids including l-theanine, the predominant amino acid in tea. The mobile phases, including the sodium acetate and acetic acid concentration in buffer B, and the pH and concentration of sodium acetate in buffer A were optimized. The elution gradients were optimized using DryLab software. In this way, an online o-phthaldialdehyde precolumn derivatization HPLC-fluorescence detection method was developed for simultaneous determination of 21 amino acids. Comparison to other HPLC methods for simultaneous determination of free amino acids in tea showed that our method is easy (automated derivatization), quick (30 min), inexpensive, and green (using a minimum of solution). It has good resolution (≥1.8) and high selectivity (interpark time ≥ 0.5 min). Free amino acids in six tea samples were analyzed. This work provides an HPLC method to simultaneously measure 21 amino acids in tea and potential in other food products.


Using an innovative Quality-by-Design approach for development of a stability indicating UHPLC method for ebastine in the API and pharmaceutical formulations

Alexander Schmidt, Imre Molnár
J. Pharm. Biomed. Anal., 78-79, 65-74 (2013)

Keywords: Quality by Design, Design Space, Chromatography modeling software, DryLab 4, UHPLC method development, Ebastine,

PDF

A stability-indicating ultra high performance liquid chromatographic (UHPLC) method has been developed for purity testing of ebastine and its pharmaceutical formulations. Successful chromatographic separation of the API from impurities was achieved on a Waters Acquity UPLC BEH C18, 50mm×2.1mm, 1.7 µm particle size column with gradient elution of 10mM acetate buffer pH 6.2 and a mixture of acetonitrile/2-propanol(1:1) as the mobile phase. Incorporating Quality by Design (QbD) principles to the method development approach by using the chromatography modeling software DryLab allows the visualization of a “Design Space”, a region in which changes to method parameters will not significantly affect the results as defined in the ICH guideline Q8 (R2). A verification study demonstrated that the established model for Design Space is accurate with a relative error of prediction of only 0.6%.

The method was fully validated for specificity, linearity, accuracy and precision, and robustness in compliance to the ICH guideline Q2 (R1). The method was found to be linear in the concentration range from the quantification limit(LOQ) to 125 of the specification limit for ebastine and each of the impurities with correlation coefficients of not less than 0.999. The recovery rate was between 98.15 and 100.30% for each impurity. The repeatability and intermediate precision (RSD) were less than 3.2% for ebastine and each of the impurities. The robustness of the developed method was studied by varying the six parameters: gradient time, temperature, ternary composition of the eluent, flow rate and start and end concentration of the gradient at 3 levels (+1, 0, −1). The resulting 729 experiments were performed in silico from the previously constructed model for Design Space and showed that the required resolution of 2.0 can be reached in all experiments. To prove the stability-indicating performance of the method, forced degradation (acid and base hydrolysis, oxidation, photolytic and thermal stress conditions) of ebastine was carried out. Baseline separation could be achieved for all peaks of the impurities, the degradation products and the API. Total runtime was only 4 min,which is an impressive 40-fold increase in productivity in comparison to themethod published in the Ph. Eur.monograph and allowed purity testing of more than 360 samples per day.


Chromatography Modelling in High Performance Liquid Chromatography Method Development

Imre Molnár, Hans-Jürgen Rieger, Róbert Kormány
Chromatography Today, 3-8 (2013)

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This article discusses the development of chromatography modelling of the last 30 years from the first software package for calculating resolution and capacity factors to the visual modelling of chromatograms for testing peak movements with altering elution conditions. Different approaches are discussed, such as retention modelling based on measurements, others based on molecular structure or on statistical considerations. The state-of-the-art will be demonstrated using DryLab with a few applications of industrial importance.


Predictability of enantiomeric chromatographic behavior on various chiral stationary phases using typical reversed phase modeling software

H.A. Wagdy, R.S. Hanafi, R.M. El-Nashar, H.Y. Aboul-Enein
Chirality, 25, 9, 506-513 (2013)

Keywords: Predictability of enantiomeric separations, DryLab, Chirobiotic V, Chirobiotic T, Chiralpak AD-RH, Ultron ES-OVM

http://onlinelibrary.wiley.com/doi/10.1002/chir...

This article aims to investigate the predictability of chromatographic behavior of enantiomers using DryLab to predict the effect of changing various chromatographic parameters on resolution in the reversed phase mode. Three different types of chiral stationary phases were tested for predictability.High rates of accuracy allow for the conclusion that Chirobiotic V reversed phase retention mechanism follows the solvophobic theory.


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

Chamseddin Chamseddin, Imre Molnár, Thomas Jira
Journal of Chromatography A, 1297, 146-156 (2013)

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

http://dx.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. Method robustness can be evaluated for each column with DryLab.

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