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

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


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


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)

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)

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. 

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)

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,


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.

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