Chemometric classification of reversed-phase high-performance liquid chromatography columns (original) (raw)
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Journal of Chromatography A
The high number of stationary phases commercially available for liquid chromatography makes the choice of the analyst a real headache. In order to provide a tool to carry out this choice on objective basis, the present work proposes interpretations of the column classifications obtained, thanks to a previously described testing procedure. The meaning of principal components was attributed to crossing over information carried by loading plots and groups revealed by hierarchical cluster analysis (HCA) on the corresponding score plots. At high solvent ratio, the retention seemed to be governed by enthalpy, whereas at low solvent ratio, entropic phenomena were predominating. Finally, the behavior of known families of RPLC columns was studied giving rise either to homogeneous groups like polar embedded grafts columns or to scattered families like Aqua type columns.
Reversed-phase liquid chromatography testing
Journal of Chromatography A, 2005
Column testing is a primary concerns for analysts. It is of use not only for the choice of set of development columns with different behaviors, but also for a substitution column in a validated method or as a quality control of new batches of stationary phase. A validated chromatographic procedure for column testing was applied to 42 commercially available columns, including alkyl, polar embedded and Aqua type stationary phases. This procedure was based on the use of two different solvents: MeOH and MeCN; and two different solvent/aqueous buffer fractions. Principal component analysis has been combined to hierarchical cluster analysis to provide both rational and objective classifications. The solvent effects were then studied on the obtained representations, revealing the necessity for considering both the solvent nature and its fraction in RPLC column testing. Differences observed depending on the solvent nature and fractions revealed quite different chromatographic behaviors according to these parameters.
Journal of Chromatography A, 2007
The main tests developed in last 20 years to investigate the chromatographic behaviour and the stationary phase properties are described in this paper. These properties are the hydrophobicity, depending on the surface area and the bonding density, the number of accessible residual silanol groups having sometimes different acidity, which can interact with neutral solutes by hydrogen bonds or with the ionic form of basic compounds and the shape or steric selectivity, depending on both the functionality of the silanising agent and the bonding density. Two types of tests are performed, either based on key solutes having well defined properties such as phenol, caffeine, amitriptyline, benzylamine, acenaphtene, o-terphenyl, triphenylene, p-ethylaniline, carotenoid pigments, or on retention models (solvation parameter, hydrophobic subtraction) obtained from the analyses of numerous and varied compounds. Thus, the chromatographic properties are either related to selectivities or retention factors calculated from key solutes, or they are described by interaction coefficients provided by multilinear regression from retention models. Three types of comparison methods are used based on these data. First, simple plots allow the study of differences between the columns as regards to one or two properties. Columns located in the same area of the plot display close properties. Second, chemometric methods such as principal component analysis (PCA) or hierarchical cluster analysis (HCA) can be performed to compare columns. In this case, all the studied properties are included in the comparison, done either by data projection to reduce the space in which the information is located (PCA) or by distance calculation and comparison for drawing a classification (HCA). Neighbouring columns are expected to provide identical chromatographic performances. These two chemometric methods can be used together, PCA before HCA. The third way is to calculate a discrimination factor from a reference column, through calculation methods based on the Pythagorean Theorem: the lower this factor, the closer the column properties. Following the presentation of the analytical conditions, the compounds and the data treatments used by the teams working in this field, the pertinence of the different selectivities, i.e. of the different probe solute couples or of the different interaction coefficients, are discussed as regards their discrimination capacity. The accuracy of chemometric treatments in the discrimination of stationary phases having different functionalities (octadecylsiloxane (ODS), cyano, fluorinated, phenyl, polar embedded group or "aqua" type) will be discussed, as well as their performances in the finer ODS discrimination. New two-dimensional plots, from data gained by different studies will be suggested, to improve the classification of stationary phases having different nature of bonded chains.
AdvionInterchim Scientific, 2023
When replacing a column for a separation under partially aqueous reversed-phase conditions, few problems may arise. This column may still not be available. A new column with the same designation may not provide the same separation. Several attempts have been made to produce a set of chemical probes to best characterize the huge number of stationary phases available. Nowadays a harmonized set of test probes has not been identified. However several independent publicly databases of HPLC columns exist today. They were also used for selection of alternative columns giving very different selectivities. We present, here, a new and complementary ranking method which includes flash purification, preparative LC and core-shell columns.The new and complementary ranking method was obtained from the sum of respective Euclidean differences corresponding to 6 normalized parameters. Four of them are the well-known Tanaka selectivities: C/P), (T/O), (A/P) pH 2.7, (A/P) pH 7.6. The fifth is the hydrophobic potential HP. The sixth parameter is the symmetry d(TF; 1) derived from reduced Veuthey test methodology at basic pH. For evaluation of the stationnary phase similarity they have been in parallel characterized by a normalized radar plot drawn with the four parameters: HP, alphaC/P), alpha(T/O), alpha(A/P) pH 2.7 and two histograms (normalized retention capacity and symmetry parameter).
Types of High-Performance Liquid Chromatography (HPLC) Columns: A Review
FoodTech: Jurnal Teknologi Pangan
Some chemical analysts, especially those working in the food sector, often find it difficult to choose the HPLC columns for their research. Every so often they tend to modify their method to fit whatever HPLC column available in their laboratory instead of looking for the column type best suited to their experiments. Other than that, HPLC column types are often very limited discussed in the class. This is particularly disadvantageous for those who have sufficient access to select the HPLC column they need for the best result. The lack of insight into the types of HPLC columns available in the market also influenced their decision to select the right column in their analysis to a large extent. This article briefly reviews the differences between the commonly used Particle-Packed Columns with the newer yet less frequently used Monolithic Columns. The types of HPLC columns based on polarity, molecular size, and the electrical charge will be described further, along with the working pri...
Talanta, 2008
In order to study column deterioration as a result of long-term storage and/or usage in liquid chromatography analyses, 55 pairs (same batch) of different commercial reversed-phase C 18 columns were examined using an already existing column characterisation system. After initial testing, one column was stored and the other was used to analyse different pharmaceuticals. All columns were characterized by four chromatographic parameters reflecting hydrophobicity, silanol activity, metal impurity and steric selectivity at the beginning and at the end of the test. An F-value was calculated to express the change of column properties with one single number. After performing analyses, higher F-values were obtained as compared to the non-used, stored columns. Although the time during which the columns were used to perform analyses was relatively short, an obvious influence was noticed, mainly resulting from small changes in silanol activity and hydrophobicity. Most of the affected columns have no endcapping and/or no base deactivation, making them more vulnerable for degradation, resulting in higher silanol activity and faster ageing. This effect is observed less with columns equipped with polar-embedded groups and/or polar endcapping, protecting the column by blocking the silanol groups and attracting a shielding water layer. Also columns with higher coverages and bulky or long chains show more resistance towards degradation.
Rapid Method for Evaluating Reversed-Phase High-Performance Liquid Chromatography Column Stability
Journal of …, 2004
A procedure is presented for the rapid evaluation of HPLC stationary phase stability at pH 8.4 or 10.1 using a temperature of 60 • C. Mobile phase (MeOH-0.1 mol l −1 aqueous NaHCO 3 , 50:50, v/v) is continuously passed through the column with periodic injections of a test solution until the several chromatographic parameters of the resulting chromatograms are degraded. The tests were applied to several commercial and laboratory-made stationary phases. After degradation two of these phases, one commercial and one laboratory-made, were examined by elemental analysis and scanning electron microscopy to elucidate the degradation process.
Journal of Chromatography A, 2004
To select appropriate stationary phases from the continuously expanding supply of potentially suitable HPLC columns, the properties of 28 frequently applied stationary phases were determined by measuring several chromatographic parameters. From these results, based on chromatographic expertise, eight stationary phases with different properties and selectivities were selected. The aim of this study is to apply chemometric tools to evaluate the initially selected set of columns, i.e. a more systematic approach for making such a selection is examined. Starting from the information obtained on the 28 stationary phases, the re-evaluation was performed independently based on the chemometric techniques Pareto-optimality, principal component analysis (PCA), and Derringer's desirability functions. The aim was to select a set of efficient columns exhibiting large selectivity differences. The chemometrically selected stationary phases were divided in groups based on hydrophobicity, a critical retention-determining property in reversed-phase chromatography. This allowed to further reducing the selection to three columns. It is demonstrated that the selection by the chemometric approaches in general is fairly comparable with the initial selection.
HPLC plays a vital role in product assessment, research, and environmental monitoring. HPLC is suited to separate higher molecular weight compounds to give quantitative and qualitative information. HPLC separatory systems, chromatographic separations are characterized by the resolution, retention time of analyte peak, selectivity, and efficiency (plate number). HPLC separations are affected with liquid mobile phases following through a column packed with a solid stationary phase. In this article, we have explained developing better HPLC methods and also achieving optimum resolution in the minimum amount of time. The top three bits of advice like considering analyte chemistry, using a scouting gradient, and optimum selectivity. We have also discussed how to improve resolution in HPLC because the effectiveness of separation can be quantified by measuring the resolution.This review offers insight into the meaning significance of recommended qualification parameters, system suitability criteria, the impact of chromatographic parameters on resolution, and parameters that influence the selectivity.