Column Classification Research Articles

Purchase Information Extraction Model From Scanned Invoice Document Image By Classification Of Invoice Table Header Texts

Development of automated document management system specified for scanned invoice images suffers from rigorous accuracy requirements for extraction of monetary data, which necessiate automatic validation on the extracted values for a generative invoice table model. Use of certain internal constraints such as amount = unit price times quantity is typical implementation. In this paper, we propose a noble invoice information extraction model with improved auto-validation method by utilizing table header detection and column classification.

The comparison of two column classification systems during the chromatographic analysis of steroids

Nowadays, due to the availability of hundreds of brands of reversed-phase liquid chromatographic columns, the selection of suitable columns can be difficult. Therefore, a good characterization and classification system is very important. Among published papers, the classification system based on quantitative structure-retention relationships and a method developed at the Katholieke Universiteit Leuven also exist. In quantitative structure-retention relationships, retention is evaluated in terms of the chemical structure of the analytes and the physicochemical properties of both the stationary and mobile phase. The second system allows to rank columns due to the values of four parameters and the calculation of specific F(KUL)-values for a reference column and to be compared with others. In this paper, the classification systems based both on quantitative structure-retention relationships and the F(KUL)-values using principal components analysis were compared. Moreover, the proposed column ranking systems have been checked in clinical practice case considering liquid chromatography determination of six steroid hormones in urine samples. Despite that the matching of both methods is not exactly the same, both classification systems provide simple, reliable and comparable results.

Facilitated column selection in the separation of acetylspiramycin components using a simple column classification system

Facilitated column selection in the separation of acetylspiramycin components using a simple column classification system

Stability of columns with semi-rigid connections including shear effects using Engesser, Haringx and Euler approaches

A complete column classification and the corresponding stability equations that can be used to evaluate the elastic critical axial loads of prismatic columns with sidesway uninhibited, partially inhibited, and totally inhibited including the simultaneous effects of bending and shear deformations and semi-rigid connections are presented and derived using three different approaches. The first two approaches are those by Engesser and Haringx that include the shear component of the applied axial force proportional to the total slope ( d y / d x ) and to the angle of rotation of the cross-section ( ψ ) along the member, respectively. The third approach is a simplified formulation based on the classical Euler theory that includes the effects of shear deformations but neglects the shear component of the applied axial force along the member. Comparisons among the critical loads obtained using these three approaches and those using the classical Euler solutions for classical column cases are presented. Examples that demonstrate the effectiveness and accuracy of the proposed stability equations and the importance of shear deformations and shear component of the applied axial force are presented in detail. These effects must be taken into account particularly in structures made of columns with relatively low effective shear areas A s (like laced columns, columns with batten plates or with perforated cover plates, and columns with open webs) or with low shear stiffness GA s of the same order of magnitude as π 2 E I / h 2 (like short columns made of laminated composites with low shear modulus G when compared to their elastic modulus E ). These effects become even more significant when the external supports are not perfectly clamped. The effects of semi-rigid connections and those due to shear forces and deformations are condensed into the proposed characteristic equations.

New strategy for decision making of Pilon fracture

To study the guidance of four column theory in decision making of Pilon fractures and its result. Ninety-one cases of Pilon fractures classified by four column method and treated by open reduction internal fixation (ORIF) were reviewed from March 2005 to June 2009. Four column classification:lateral column of 67 cases were involved, posterior column of 34 cases were involved, medial column of 34 cases were involved and anterior column of 34 cases were involved. Among all the 94 fractures, single column of 20 fractures were involved, 2 columns of 49 fractures were involved, 3 columns of 15 fractures were involved and all of 4 columns of 10 fractures were involved. Eighty-nine cases had been followed up. The average follow-up time was 16.2 months ranging between 6.0 and 39.0 months. The average healing time was 3.7 months ranging from 3.0 to 5.0 months. Reduction of 91% reviewed Pilon cases were good or acceptable according to Burwell and Charley's radiology evaluation system. Ankle function of 87.6% cases were excellent or good according to AOFAS evaluation system. As a simple and comprehensive classification, four column classification can contribute to reasonable operating decision making and good prognosis of Pilon fracture.

Hydrophilic interaction LC of peptides: Columns comparison and clustering

A wide variety of hydrophilic interaction chromatography (HILIC) stationary phase surface chemistries are currently available. Although their selectivity can be considerably different, column comparison or clustering using peptides is limited. In this study, ten pharmaceutically relevant model peptides are analyzed on seven different HILIC columns (bare silica, amide, poly-hydroxyethyl aspartamide, diol and zwitterionic) for the evaluation of their performance and classification. The responses examined include single and multiple responses: plate number, asymmetry factor, LOD, geometric mean resolution, resolution product, time corrected resolution product, peak capacity and chromatographic response function. Column classification was performed using hierarchical clustering and principal component analysis. Moreover, the overall performance quality of the HILIC columns was compared using a linear desirability function. Hierarchical clustering and principal component analysis showed consistent clusters. The zwitterionic phase was clustered apart from the other HILIC columns and both poly-aspartamide columns were clustered together. In addition, the two bare silica phases represent two different clusters, and thus different selectivities. Overall, the responses showed the best performance for one of the bare silica columns (Alltima-Alltech), followed by the zwitterionic phase (ZIC)-HILIC. Thus, these columns, belonging to different clusters, were found to be the best performing systems in pharmaceutical peptide analysis for the selected peptide set.

Asymmetry models for square contingency tables: exact tests via algebraic statistics

Square contingency tables with the same row and column classification occur frequently in a wide range of statistical applications, e.g. whenever the members of a matched pair are classified on the same scale, which is usually ordinal. Such tables are analysed by choosing an appropriate loglinear model. We focus on the models of symmetry, triangular, diagonal and ordinal quasi symmetry. The fit of a specific model is tested by the chi-squared test or the likelihood-ratio test, where p-values are calculated from the asymptotic chi-square distribution of the test statistic or, if this seems unjustified, from the exact conditional distribution. Since the calculation of exact p-values is often not feasible, we propose alternatives based on algebraic statistics combined with MCMC methods.

Application of Snyder–Dolan classification scheme to the selection of “orthogonal” columns for fast screening of illicit drugs and impurity profiling of pharmaceuticals – I. Isocratic elution

Fourteen judiciously selected reversed phase columns were tested with 18 cationic drug solutes under the isocratic elution conditions advised in the Snyder–Dolan (S–D) hydrophobic subtraction method of column classification. The standard errors (S.E.) of the least squares regressions of log k′ vs. log k′ REF were obtained for a given column against a reference column and used to compare and classify columns based on their selectivity. The results are consistent with those obtained with a study of the 16 test solutes recommended by Snyder and Dolan. To the extent these drugs are representative, these results show that the S–D classification scheme is also generally applicable to pharmaceuticals under isocratic conditions. That is, those columns judged to be similar based on the 16 S–D solutes were similar based on the 18 drugs; furthermore those columns judged to have significantly different selectivities based on the 16 S–D probes appeared to be quite different for the drugs as well. Given that the S–D method has been used to classify more than 400 different types of reversed phases the extension to cationic drugs is a significant finding.

Column Classification and Selection for the Determination of Antibiotics by Micellar Liquid Chromatography

Seven commercially available: Zorbax C18, Kromasil C18, C8, cyano, phenyl, monolithic, and amino stationary phase columns, have been characterized and classified into broadly similar types to simplify column choice. The results were evaluated employing cluster analysis, which shows several interesting groups based on distances (Minkowski and Euclidean) in agreement with the manufacturer's claims: chain density of the stationary phase used, and the presence or not of a silica base. Finally, results showed that C18 columns offer the best chromatographic characteristics for separation and quantification of antibiotics in micellar liquid chromatography.

Evaluation of an International Pharmacopoeia method for the analysis of ritonavir by liquid chromatography

A gradient LC method for the determination of related substances in ritonavir (RTV) has been recently published in the International Pharmacopoeia. The method uses a base-deactivated reversed-phase C18 column kept at a temperature of 35 °C. The mobile phases consist of acetonitrile, phosphate buffer pH 4.0 and water. UV detection is performed at 240 nm. A system suitability test (SST) is described to govern the quality of the separation. Since no brand names of columns are mentioned in pharmacopoeial texts, analysts often have problems to select a suitable stationary phase which is only described in general terms. So, the separation towards RTV components was investigated on 18 C18 columns and correlation was made with the column classification system developed in our laboratory. The method was further evaluated using a Hypersil BDS C18 column (25 cm × 4.6 mm i.d.), 5 μm, which was also used for the development of the method. A central composite design was applied to examine the robustness of the method. The method shows good precision, linearity, sensitivity and robustness. Four commercial samples were examined using this method.

Finding an Alternative Column for the Separation of Antibiotics on XTerra RP using a Column Classification System

A project to develop a test procedure to characterize reversed‐phase liquid chromatographic C18 columns was started earlier and resulted in a fast, simple, repeatable, and reproducible test procedure. In this paper, the separations of two antibiotics (erythromycin and tetracycline) from their respective impurities were examined. Both methods were developed on XTerra RP, a hybrid column. The performance of the column classification system was evaluated by finding an alternative column for the XTerra RP column. The column classification system was helpful in the selection of a suitable column for the separation of erythromycin, but also showed its limitations towards the separation of tetracycline. The addition of an efficiency parameter and/or omission of one of the original parameters did not improve the results.

Three methods to characterize reversed phase liquid chromatographic columns applied to pharmaceutical separations

AbstractSelecting a suitable reversed phase liquid chromatographic (RP‐LC) column for a particular separation is complicated. More than 600 brands of C18 columns are available on the market. Therefore, determining the characteristics influencing the selectivity of the different stationary phases is necessary. In this paper, three different methods to characterize RP‐LC columns are compared. Hoogmartens et al. developed a column characterization system based on test methods from literature, which were reduced with principal component analysis (PCA), and led to four final chromatographic parameters. The second method studied is this of Euerby et al. who developed a column classification system using six parameters, based on the method of Tanaka and also applying PCA. The third method, developed by Snyder et al. is different from the other two. It uses five parameters, calculated by multiple linear regression from the retention data of 18 solutes. The suitability of the column classification systems was examined on pharmaceutical separations. It seems that all three methods can facilitate the selection of a suitable column for an analysis. Copyright © 2008 John Wiley & Sons, Ltd.

Comparative evaluation of high-performance liquid chromatography stationary phases used for the separation of peptides in terms of quantitative structure–retention relationships

Chromatographic measurements were made on 17 physicochemically diversified high-performance liquid chromatography (HPLC) columns which were further analyzed in terms of their similarities and dissimilarities for 25 carefully designed, structurally diverse peptides showing distinctly distinguished groups. The goal of the study was to investigate the molecular mechanism of retention and to find an objective manner of quantitative comparison of retention properties and classification of modern stationary phases for reverse phase HPLC (RP-HPLC). We utilized the structural descriptors of peptides obtained from molecular modeling to describe their chromatographic retention behavior under given HPLC conditions. Quantitative structure–retention relationships (QSRR) with the following descriptors were employed: logarithm of the sum of amino acid retention contributions in a given peptide, log Sum AA, logarithm of the Van der Waals volume of the peptide, log VDW vol, and logarithm of its calculated n-octanol/water coefficient, clog P. The best QSRR equations were obtained in the case of monolithic and regular octadecylsilica columns. On the other hand, the combination of QSRR and principal component analysis (PCA) can be considered as the efficient tool allowing column classification and searching for orthogonal HPLC conditions required to separate peptides.

Column selection for pharmaceutical analyses based on a column classification using four test parameters

This paper focuses on the usability of a previously developed column classification system, applied to pharmaceutical analyses. The separation of two drugs from their respective related substances was investigated on 65 new reversed-phase liquid chromatographic columns. The chromatographic procedure for fluoxetine hydrochloride was performed according to the method prescribed in the European Pharmacopoeia monograph while the separation of gemcitabine hydrochloride was carried out according to the United States Pharmacopeia monograph. It was shown that the column ranking system is a helpful tool in the selection of a suitable column.

Reversed-phase liquid chromatography column testing and classification: Physicochemical interpretation based on a wide set of stationary phases

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.

Evaluation of an International Pharmacopoeia method for the analysis of nelfinavir mesilate by liquid chromatography

A gradient LC method for the determination of related substances in nelfinavir mesilate (NFVM) has been recently published in the International Pharmacopoeia. The method uses a base deactivated reversed phase C18 column (25 cm × 4.6 mm I.D.), 5 μm kept at a temperature of 35 °C. The mobile phases consist of acetonitrile, methanol, phosphate buffer pH 3.4 and water. The flow rate is 1.0 ml/min. UV detection is performed at 225 nm. A system suitability test (SST) is described to govern the quality of the separation. The separation towards NFVM components was investigated on 18 C18 columns and correlation was made with the column classification system developed in our laboratory. The method was evaluated using a Hypersil BDS C18 column (25 cm × 4.6 mm I.D.), 5 μm. A two level fractional factorial design was applied to examine the robustness of the method. The method shows good selectivity, precision, linearity and sensitivity. Seven commercial samples were examined using this method.

Evaluation of an International Pharmacopoeia method for the analysis of saquinavir (mesilate) bulk drugs by liquid chromatography

A single gradient LC method for the determination of related substances in both saquinavir (SQV), saquinavir mesilate (SQVM) has been published in a consultation document of the International Pharmacopoeia, WHO Drug Information. The method uses a base deactivated reversed phase C18 column (25 cm × 4.6 mm i.d.), 5 μm kept at a temperature of 30 °C. The mobile phases consist of acetonitrile, methanol, phosphate buffer pH 3.4 and water. The flow rate is 1.0 ml/min. UV detection is performed at 220 nm. A system suitability test (SST) is described to govern the quality of the separation. The separation towards SQV(M) components was investigated on 18 C18 columns and correlation was made with the column classification system developed in our laboratory. The method was evaluated using a Hypersil BDS C18 column (25 cm × 4.6 mm i.d.), 5 μm. A central composite design was applied to examine the robustness of the method. The method shows good precision, linearity, sensitivity and robustness. SQV(M) commercial samples of bulk drugs were examined using this method.

Influence of pH on Benzoic Acid Derivatives' Retention and RP HPLC Column Classification

The pH role in benzoic acid derivatives chromatographic analysis were under the current study. The retention factor (k), as well as the peak asymmetry (f AS ), were determined and compared using five commercially available reversed phase columns. Utilization of statistical approaches of tested chromatographic columns were divided into several groups according to the obtained data (retention factor, asymmetry) due to the different mobile phases pH (pH=5.8 and 3.0). Although four studied columns (Purospher‐STAR, Alltima, Reprosil, Symmetry) were the octadecyl type, they showed significant differences in the benzoic acids derivatives. Obtained results allowed for distinctions in individual column chromatographic behavior explanation.

Advances in HPLC technology for the determination of drug impurities

Advances in HPLC technology have improved capability for drug impurity profiling in terms of faster analysis time, better separations and faster method development. We review developments in monolithic columns, sub-2-μm particle columns operated at typical or high pressures, high temperature operation, new stationary phases, systematic method development, column classification techniques and selected detectors.

Classification of reversed-phase columns based on their selectivity towards vancomycin compounds

The selection of a reversed-phase liquid chromatographic (RP-LC) column with suitable selectivity for a particular separation is difficult if the brand name of the column is not known. The monographs of the European Pharmacopoeia and other official compendia for drug analysis only give a general description of the stationary phase to be used in the operating procedure of a liquid chromatographic method. A project to develop a chromatographic test procedure to characterise RP-LC C 18 columns was started earlier and resulted in a fast, simple, repeatable and reproducible test procedure. Four column parameters, determined on 69 RP-LC C 18 columns, allowed the characterisation and ranking of these columns. In this paper, an overview of this column classification system is given with an application on the separation of vancomycin and some of its impurities. It is shown that the column ranking system is a helpful tool in the selection of a suitable column.