Stability-indicating high performance thin layer chromatography determination of Paroxetine hydrochloride in bulk drug and pharmaceutical formulations

A simple selective precise and stability-indicating high performance thin layer chromatographic method of analysis of Paroxetine hydrochloride both as a bulk drug and in formulations was developed and validated. The method employed TLC (Thin Layer Chromatography) aluminum precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of butanol:acetic acid:water (8:2:0.5, v/v/v). This system was found to give compact spots for Paroxetine HCl (Rf, retardation factor, value-0.48 ± 0.02). Paroxteine HCl was subjected to acid and alkali hydrolysis, oxidation and photodegradation, where the degraded product was well separated from the pure drug. Densitometric analysis of Paroxetine hydrochloride was carried out in the absorbance mode at 295 nm. The linear regression analysis data for the calibration spots showed good relationship with (regression) r² = 0.9903 in the amount range of 300-1500 ng (nanogram) per spot. The mean value of co-relation co-efficient, slope and intercept were 0.9903 ± 0.001, 5.38 ± 0.058 and 182.5 ± 2.16 respectively. The method was validated for precision, recovery and robustness. The limits of detection and quantitation were 50 and 150 ng, respectively. The drug doesnot undergo degradation with oxidation, but gets affected in acidic and alkaline conditions. The acid and alkali degradation showed extra peaks at 0.4 and 0.08 Rf, respectively. This indicates that the drug is susceptible to acidic and alkaline medium. As the method could effectively separate the drug from its degradation products, it can be employed as a stability-indicating one.     

Prediction of the retention in thin layer chromatography screening systems by atomic contributions

A novel atomic-contribution system for predicting of R_M values is presented and validated on 13 thin layer chromatography screening systems on silica gel, where the large experimental datasets (198-761 R_M values) are available. The R_M is predicted with error less than 0.5 in majority of solutes (besides several outliers), which corresponds to difference in R_F equal to 0.28 in the worst case. The system was validated by dividing the data into training and validation datasets, proving its accuracy. The main reason of larger errors in outliers are: large conjugated heterocycles, quarternary ammonium cations, large amount of polar atoms or very simple but unique molecules. The calculations are very easy and can be performed on free software or even manually. The presented method can be used in the retention prediction of new solutes in existing chromatographic screening systems.     

Contour diagrams for the presentation of separation quality in two-dimensional thin layer chromatography

Several methods for evaluating separation quality in two-dimensional thin layer chromatography are discussed. These include using either the distance between spot centers for the pair of solutes that is the most difficult to separate in a mixture, or the value of a suitable, separation function, as criteria of overall separation quality. Contour diagrams may be constructed in which solvent compositions for each of the two-dimensional developments are the independent variables and spot separation or the value of a suitable function is the dependent variable. Such diagrams indicate which are the best and the worst regions of the two-dimensional solvent domain. These diagrams should be of value for comparing different solvent systems for two-dimensional thin layer chromatography.     

Quality assessment for tramadol in pharmaceutical preparations with thin layer chromatography and densitometry

Research studies have been carried out to develop a chromatographic and densitometric method suitable for identification and determination of tramadol and impurities. In addition, the stability of tramadol in solutions was investigated, including an effect of solution pH, temperature and incubation time. In the first instance the conditions for identification and quantitative determination of tramadol and impurities in pharmaceutical preparations were established. The separation was performed on silica gel-coated chromatographic plates (HPTLC) using two mobile phases: (I) chloroform-methanol-glacial acetic acid (9:2:0.1, v/v/v); (II) chloroform-toluene-ethanol (9:8:1, v/v/v). The UV densitometry was carried out at lambda = 270 nm. The developed method is of high sensitivity and low detection and determination limits ranging from 0.044 to 0.35 microg. For individual constituents the recovery ranges from 93.23 to 99.66%. The next step was to evaluate the stability of tramadol and determine a method of decomposition under various experimental conditions. It was found that tramadol decomposes in various ways in acidic and basic environments producing (1RS)-[2-(3-methoxyphenyl)cyclohex-2-enyl]-N,N-dimethylmethanamine (imp. B) and (1RS, 2RS)-2-[(dimethylamino)methyl]-1-(3-methoxyphenyl)cyclohexanol (imp. cis-T) or imp. cis-T, respectively.     

Characterization and classification of medicinal plants according to their antioxidant profile estimated by thin layer chromatography assisted by chemometric expertise

This study focuses on the characterization and classification of 42 medicinal plants extracts according to their antioxidant activity. Principal component analysis (PCA), cluster analysis (CA) and the combination of PCA with linear discriminant analysis (PCA-LDA) were used as multivariate exploratory techniques for chromatographic data analysis. For the separation of the compounds a mobile phase containing ethyl acetate: toluene: formic acid: water (30:1.5:4:3 v/v/v/v) and different HPTLC plates (Silica gel 60 and HPTLC Silica gel 60?F₂₅₄) were used. The chromatographic plates were evaluated using the images obtained after spraying the plates with 2-aminoethyldiphenylborate solution (NTS, 0.2% in ethanol) and also after their reaction with 2, 2-diphenyl-1-picrylhydrazyl solution (DPPH^?) (0.2% in ethanol). The score projection on the plane defined by first two components (PC1 and PC2) revealed two large groups of the investigated samples depicted according to their antioxidant capacity. A better classification of samples according to their antioxidant capacity was obtained using the CA and PCA-LDA methodology in all cases. The excellent results obtained in this study concerning the classification of medicinal plants according to their antioxidant capacity using the PCA-LDA methodology applied to TLC chromatograms might lead to a new paradigm in the field of medicinal plant holistic evaluation.     

High-performance thin layer chromatography method for estimation of andrographolide in herbal extract and polyherbal formulations

A new, simple, sensitive, precise and robust high-performance thin layer chromatographic (HPTLC) method was developed for the estimation of andrographolide in herbal extracts and pharmaceutical dosage forms. Analysis of andrographolide was performed on TLC aluminium plates pre-coated with silica gel 60F-254 as stationary phase. Linear ascending development was carried out in twin trough glass chamber saturated with chloroform:toluene:methanol (66:26:8, v/v/v) at room temperature (25 ± 2 °C). The R_f value of andrographolide was found to be 0.49. Camag TLC scanner III was used for spectrodensitometric scanning and analysis in absorbance mode at 229 nm. The system was found to give compact spots for andrographolide (R_f value of 0.49). The data for calibration plots showed good linear relationship with r² = 0.9986 in the concentration range of 200 ng to 1000 ng with respect to peak area. The present method was validated by precision, recovery, robustness and reproducibility according to ICH guidelines. The limits of detection and quantification were determined and it was found to be 3.5 and 11.7 ng, respectively. Statistical analysis of the data showed that the method is reproducible and selective for estimation of andrographolide.     

Determination of platinum, palladium and rhodium in Pt-catalysts by high performance thin layer chromatography using densitometry

The determination of palladium and platinum in alumina-supported bimetallic Pt-Re, Pd and Pt catalysts at the 0.03 and 0.3% (m/m) levels, respectively, and of rhodium and platinum in platinum sieve catalysts at the 0.04% (m/m) level and in the 4.75–19.75% (m/m) range, respectively, is described. The platinum group metals in fresh or spent catalysts are determined chromatographically using densitometry by forming theirN,N-diethyl-N-benzoylthiourea complexes. The precision of the method, %RSD, is 0.4–3.5, 2.2–6.7, and 4.2–6.0 for Pt, Pd and Rh, respectively. The accuracy was tested using alumina-based and active carbon platinum and palladium standards. The results were also compared with those obtained by FAAS. There was at most 8% difference between the results obtained with these methods, except for one active carbon based Pd standard.     

Separation of neutral and basic enantiomers by cyclodextrin electrokinetic chromatography using anionic cyclodextrin derivatives as chiral pseudo-stationary phases

Separations of neutral and basic racemates were performed using five different anionic cyclodextrin (CD) derivatives as chiral selectors, viz. carboxymethylated β-CD, β-CD phosphate sodium salt, sulfobutyl ether β-CD sodium salt, carboxymethylated γ-CD, and γ-CD phosphate sodium salt. For the separation of neutral racemates, an untreated fused silica capillary was employed and various neutral racemates were successfully separated. Since the pH of the buffer affected the electroosmotic flow (EOF), the resolution was improved by changing the buffer pH. A polyacrylamide coated capillary was employed for the separation of basic racemates to suppress EOF and to prevent adsorption of cationic analyte on the capillary surface. By choosing an appropriate type and concentration of anionic CD, about 40 basic racemates were successfully separated. Some rough binding constants of basic analytes with an anionic β-CD were measured to discuss the optimum concentration of the CD. The migration direction was dependent on the binding constants and the concentration of the CD. The analyte strongly bound to the anionic CD migrated towards the anode but the weakly bound one moved towards the cathode. Anionic γ-CDs were also very useful for the separation of basic enantiomers. Five neutral CDs were employed as chiral selectors to compare selectivity between charged and neutral CDs, and eleven racemates could only be resolved using anionic CDs. The separation of some basic racemates in human plasma was also described. The direct injection of plasma samples was possible for some enantiomers that did not interact strongly with plasma proteins.     

Behavior of peptides and computer-assisted optimization of peptides separations in a normal-phase thin-layer chromatography system with and without the addition of ionic liquid in the eluent

The addition of an ionic liquid into the mobile phase appeared to be useful in optimization of chromatographic separation of peptides. Different behavior of peptides in thin-layer chromatography (TLC) was observed after addition of 1-ethyl-3-methylimidazolium tetra fluoroborate to the eluent in comparison to the system without the ionic liquid. Nonlinear dependence of the retention coefficient, R(M), of peptides on the volume percentage of acetonitrile in the eluent was found in normal-phase TLC with and without immidazolium tetra fluoroborate in the mobile phase. In general, R(M) increased with increasing concentration of acetonitrile. In TLC systems without the ionic liquid, R(M) can be described well with a quadratic function. On the other hand, in a TLC system with an ionic liquid as the additive to the mobile phase, the retention behavior is better described with a third-degree polynomial function. The potential usefulness of ionic liquids for optimization of separation of peptides was demonstrated. Optimization of the separation conditions was supported by a commercially available computer program.     

Quasi-thin layer chromatography with forced flow of the mobile phase in microchannels packed with a sorbent

A version of the thin-layer chromatography with forced flow of the mobile phase in microchannels packed with a sorbent is proposed. The dependences of retention parametersR _f and the number of theoretical plates in the course of the elution of hydrophilic dyes (naphthol red and methyl red) on the eluent (propan-2-ol) pressure and developing time were studied. The method can be of interest as a simplified version of the forced-flow TLC and would be useful as a micropilot technique for liquid chromatography. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1538–1539, August, 1997.     

The effect of methylene chain length on the chromatographic behaviour of aminobonded silicas in high-performance thin layer chromatography

Summary High-performance thin layer chromatography has been carried out on 3-aminopropyltriethoxysilane, N-(2-aminoethyl)--aminopropyltrimethoxysilane or trimethoxysilylpropyldiethylenetriamine-treated thin layer plates, the chromatographic properties of the amino-modified plates depends largely on the amino-methylene (alkylamino) chain length bonded to the surface of the silica gel.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Sequential centrifugal layer chromatography (SCLC): A new technique for the isolation of natural compounds. Part 2: Comparative study on centrifugal layer chromatography (CLC) and SCLC for the separation of furocoumarin isomers

The new sequential centrifugal layer chromatography extends the possibilities for preparative separation of furocoumarin isomers. In the present work, isobergapten, pimpinellin, bergapten, isopimpinellin, and sphondin were isolated from a prepurified extract of Heracleum sphondylium roots using two different techniques, namely, centrifugal layer chromatography (CLC) and sequential centrifugal layer chromatography (SCLC). The former technique was carried out with four plates, whereas the latter method required only one plate, using the same mobile phase in each case. A further advantage of the SCLC method was that all completely separated compounds could be quickly and efficiently eluted in small volumes of mehtanol.     

薄层色谱法测定二磺化和三磺化 5H-苯基联苯膦氧化物的含量

采用薄层色谱法,对新型化合物5H-苯基联苯磷（PDBP）磺化产物的分离、二磺化和三磺化PDBP氧化物标准品的制备及其定量分析进行了研究。     

Enantiomer separation of side-chain fluorinated alkylbenzenes by capillary gas chromatography on cyclodextrin phases

Summary The separation of racemic side-chain fluorinated alkylbenzenes and bromofluorinated analogues by capillary gas chromatography using permethylated , and -cyclodextrins dissolved in polysiloxanes of different polarity as stationary phases is described. The influence of the achiral polysiloxane matrices on the separation of enantiomers is discussed in the light of the results obtained with the different phases. For a part of the tested compounds thermodynamic data are determined which describe the interaction of enantiomers with the stationary phase. The mechanism of separation is discussed on this basis and by comparison with data for structurally similar compounds.     

Salting-out thin layer chromatography of transition metal complexes: A comparative study of the effect of increased number of CH2 groups in chelate rings

Summary The regularities previously established in salting-out thin-layer chromatography on silica gel of Co(III) complexes, in which the side chains of a specific chelate ring were successively increased in length, were also found to be valid for two series of Co(III) complexes of the EDTA type, in which different chelate rings were enlarged by one CH₂ group. It was found that in the case of complexes of the EDTA type the salting-out efficiencies were practically the same for all members of a series, while the values of the separation factors were paractically independent of the ammonium sulphate concentration in the solvent system used. The results obtained were consistent with the mechanism of nonspecific hydrophobic interactions. The method used can be applied to the separation of the members of the series of complexes that we investigated.     

Enantiomer separation by counter-current chromatography. Optimisation and drawbacks in the use of L-proline derivatives as chiral selectors

Several L-proline and (4R)-hydroxy-L-proline derivatives were evaluated as chiral selectors (CSs) in the separation of enantiomers by counter-current chromatography (CCC). A variety of biphasic solvent systems, all of organic/aqueous nature, were tested in order to determine the appropriate distribution for CSs and racemates (N-(3,5-dinitrobenzoyl)-(+/-)-leucine and (+/-)-ketoprofen). Successful separations of DNB-(+/-)-leucine in analogous experimental conditions allow the comparative study of the enantioselectivity displayed by the considered CSs. The low solubility of certain CSs limits their applicability for preparative purposes even for improved enantioselectivity. The effect that the nature and pH of the buffer solutions used as a component of the solvent system have on the separation was also studied.     

Separation of the enantiomers of 2-phenylcyclopropanecarboxylate esters by capillary gas chromatography on derivatized cyclodextrin stationary phases

Summary Separation of the enantiomers of 2-phenylcyclopropanecarboxylate esters has been investigated on derivatized cyclodextrin chiral stationary phases (CD CSPs) to enable direct determination of the enantiomeric purity of the products of enantioselective cyclopropanation. Four stereoisomers of these chiral compounds could be resolved to baseline on permethylated β-cyclodextrin CSP. Some unusual phenomena, iso-enthalpy retention behavior and entropically driven chiral separation, were observed for the enantioseparation of 2-phenylcyclo-propanecarboxylates on the CD CSPs. Thermodynamic parameters were evaluated and an enthalpy-entropy compensation effect was observed forn-alkyl esters of 2-phenylcyclopropanecarboxylate separated on CD CSPs.