ABSTRACT

A highly sensitive and selective thin layer chromatographic (TLC) method was developed for simultaneous determination of catecholamines and their related drugs using a new detection method and digital image processing of chromatographic plates. For the quantitative evaluation of the investigated compounds, the chromatographic separation was followed by spraying the plate with 0.02% solution of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH ) in ethanol. The BioDit Thin Layer Chromatography (TLC) Scanner device and advanced specific software (ImageDecipher-TLC, Sorbfil TLC Videodensitometer and JustTLC) were used for the detection and quantification of chromatographic spots. For an accurate determination, the RGB colored images of the bright-white spots detected against a purple background were inverted and processed after their conversion into green scale. The results showed a strongly linear correlation between area (R2>0.99) and volume (R2>0.99) of spots and concentration of investigated compounds in all cases. The limit of detection (LOD) and the limit of quantification (LOQ) were below 49.3 ng/spot and 69.6 ng/spot respectively in all cases. The evaluation of the method was performed using different pharmaceutical samples spiked with the investigated amines and validated with respect to accuracy and precision.

ABSTRACT

A comprehensive study of biogenic amines and related drugs as free radical scavengers and potential antioxidants was carried out using the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH•). The results of the effect of test duration and the relative concentration on the ability of the compounds to scavenge the DPPH• were investigated and discussed. The antiradical activity of amines was compared with the activity of some reference antioxidants (phenols, phenolic acids, flavonols and other antioxidants). Some particular insights related to the mechanism of reactivity toward the DPPH• were investigated by carrying out kinetic studies in methanol for different relative concentrations. According to the obtained results, catecholamines and especially their related drugs (D-dopa, adrenalone, S-(-)-carbidopa and isoprenaline) showed a fast reactivity towards DPPH• and the highest antiradical activity which increased in a concentration-dependent manner. Moreover, catecholamines proved to be more powerful scavengers than ascorbic and caffeic acids even at low concentrations while their related drugs (D-dopa, adrenalone and S-(-)-carbidopa) showed higher antiradical activity than gallic acid for all of the investigated concentrations.

ABSTRACT

A facile and rapid thin-layer chromatography (TLC) method for tartrazine analysis from mustard is proposed. Silica gel precoated plates and isopropyl alcohol-ammonia mixture as mobile phase were used for tartrazine determination. The synthetic dye was extracted from solid matrix by ultrasound assisted extraction with a methanol-ammonia mixture and further purified by ion-pair solid phase extraction, using hexadecyltrimethylammonium-bromide as ion-pair reagent. Recovery determination was carried out on mustard samples spiked with tartrazine at different concentration levels. Good recoveries, around 98%, and a relative standard deviation of 17.4% were obtained. An extensive study for the quantitative evaluation of dyes was developed by comparing the photodensitometric results with those obtained by using digital processing of scanned plates with ImageDecipher-TLC software. The method was applied for the tartrazine determination in various mustard samples purchased from a local market.

ABSTRACT

A new perspective in the lipophilicity evaluation through RP-HPLC is permitted by analysis of the retention factor (k) obtained by injecting large volumes of test samples prepared in solvents immiscible with mobile phase. The experiment is carried out on representative groups of compounds with increased toxicity (mycotoxins and alkaloids) and amines with important biological activity (naturally occurring monoamine compounds and related drugs), which are covering a large interval of lipophilicity. The stock solution of each compound was prepared in hexane and the used mobile phases were mixtures of methanol or acetonitrile and water, in suited volume ratio. The injected volume was between 10 and 100 µL, while the used stationary phases were RP-18 and RP-8. On both reverse stationary phases the retention factors were linearly decreasing while the injection volume was increasing. In all cases, the linear models were highly statistically significant. On the basis of the obtained results new lipophilicity indices were purposed and discussed. The developed lipophilicity indices and the computationally expressed ones are correlated at a high level of statistical significance.

ABSTRACT

The retention behavior for a series of biogenic amines and related sympathomimetic drugs has been investigated in reversed-phase thin-layer chromatography using RP-2, RP-8, RP- 18W, and Diol stationary phase and mixtures of phosphate buffer (pH=7.10) and methanol in different proportions as mobile phases. Several methodologies like arithmetic mean of experimental retention values, extrapolation to zero methanol concentration procedure and principal component analysis were applied to retention data values (RM) in order to determine relevant parameters (mean of RM - mRM, RM0, and scores corresponding to the first principal component - PC1/RM respectively) encoding information on the lipophilic behavior of compounds. High similarities in lipophilicity behavior of investigated amines were highlighted by mRM and PC1/RM lipophilicity indices for all of the studied stationary phases. The experimental results were compared with some computed lipophilicity parameters expressed as distribution coefficients at working pH (logD), partition coefficients (logPN, logPI, and diff(logPN–I)) concerning both neutral and fully protonated species and difference between both species, and also with various lipophilicity values (logP) generated by different commonly used software. Significant correlations were observed between the experimental lipophilicity indices mRM respectively PC1/RM and diff(logPN–I) values in all cases

ABSTRACT

A high-performance thin-layer chromatographic method combined with a sample preparation procedure has been developed for simultaneous determination of sunset yellow and azorubine synthetic yes in powders for jelly desserts containing a variety of other ingredients. Some different xtraction solvents and sample preparation steps (solid phase extraction procedures on RP-18 nd polyamide cartridges) were tested for the quantitative isolation and purification of dyes. he best recovery results were achieved by using methanol for extraction procedure followed by solid hase extraction on the polyamide cartridges for the purification step. For the quantitative evaluation f the chromatographic spots, visible slit-scanning densitometry and digital processing of mages of chromatographic plates (using ImageDecipher-TLC software with pure color-green and lue and integrate color- grey channels selection) were compared. The best statistical parameters or the linear functions of the calibration were obtained using ImageDecipher-TLC software for he quantitative evaluation of the investigated dyes. The lowest limits of detection and quantification 0.0096 and respectively 0.0190 lg=spot for azorubine and 0.0117 and respectively .0231 lg=spot for sunset yellow) were obtained by selecting pure color (green and blue) channels or dyes determination. The results obtained for commercial food samples showed that the proposed ethod is suitable for rapid routine nalysis of synthetic dyes in powders for jelly dessert samples.

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A thin-layer chromatographic method combined with a sample preparation procedure has been developed for determination of Sunset Yellow (E110) and Amaranth (E123) synthetic dyes in different pharmaceutical powders. For an accurate separation of investigated dyes, different mobile phases were tested using silica gel G chromatographic plates. The dyes were analyzed using slit scanning densitometry with specific wavelength selection (?=485 nm for E110 and ?=520nm for E123). Experimental results showed a very good linear correlation (R2 > 0.9940) between area of colored spots and concentration of dyes in range of 4-20 µg/mL. In addition, low values of LOQ (0.29 µg/mL for E123 and 0.46 µg/mL for E110) and LOD (0.58 µg/mL for E123 and 0.92 µg/mL for E110) were obtained. The sample preparation step was focused on the quantitative desorption of dyes from starch based matrix and sugars removing. In the case of non soluble matrix, different extraction solvents and techniques were tested. The best results were obtained using ultrasounds assisted extraction (UAE) using the mixture of MeOH-NH3 (9:1 v/v) as extraction agent. In the case of water soluble samples, a purification step by ion-pair – solid phase extraction (IP-SPE) on C18 cartridges using hexadecyltrimethylammonium bromide (CTAB) was developed. High recovery values (R%) and a good reproducibility (RSD) was obtained for E110 and E123 (99.27±3.73% and 98.84±1.17% respectively). The applicability of the developed method was assessed for Coldrex and Daleron Junior pharmaceutical powders. The obtained results (42.64±3.29mg/kg E110 and 218.86±10.73mg/kg E123 in Coldrex and 54.21±3.95mg/kg E110 in Daleron) showed that the proposed method is suitable for rapid routine analysis of synthetic dyes in pharmaceutical powders

ABSTRACT

A high-performance thin-layer chromatographic method combined with a sample preparation procedure and digital images processing has been developed for simultaneous determination of parabens in pharmaceutical suspensions. For the quantitative evaluation of the chromatographic spots, three different software that combines 2D (ImageDecipher-TLC and Sorbfil TLC) and respectively 3D (JustTLC) image analysis were investigated. The statistical parameters of the linear relation between the applied concentrations and both the peaks area and volume respectively, revealed no statistical significant differences in terms of the regression determination coefficient (R2). The lowest limits of detection and quantification values were obtained for ethylparaben and butylparaben using the ImageDecipher-TLC software. Also, by using ImageDecipher-TLC software with conversion of color images of chromatographic plates into grey scale, the precision of the developed method increased in all cases. The results obtained for commercial samples showed that the proposed method, using new UV-Vis TLC scanner device with ImageDecipher-TLC software, is suitable for rapid routine analysis of parabens in pharmaceutical suspensions.

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A study for quantitative evaluation of thin layer chromatographic plates by using, for the first time, the BioDit Thin Layer Chromatography (TLC) Scanner device in UV mode was developed for imultaneous determination of the parabens (methyl, ethyl, propyl, and butylparaben) in pharmaceutical preparations. ImageDecipher-TLC software and Sorbfil TLC Videodensitometer were used for image processing analysis. After their chromatographic separation, the quantification of the parabens was made by the conversion of RGB colored images of TLC plates (obtained by UV light scanning at kĽ254 nm) into grey scale. Experimental results showed a strongly linear correlation between area of grey spots and concentration of parabens covering a relatively large domain of concentration in all cases. The linearity of the analytical procedure was in range of 0.46–2.47 lg=spot for methylparaben, 0.50–2.99 lg=spot for ethylparaben, 0.54–3.24 lg=spot for propylparaben, and, respectively, 0.58–3.49 lg=spot for butylparaben, the regression determination coefficient being higher than 0.9977 in all cases. The recovery studies performed on two levels of concentration gave values higher than 96.32% in the case of ImageDecipher-TLC software for all studied parabens. The limits of detection and quantification varied in that case between 0.10–0.37 lg= spot and 0.20–0.44 lg=spot, respectively. The proposed method was found to have a good precision and accuracy and their applicability was assessed for commercial pharmaceutical syrup samples analysis.

ABSTRACT

Quantitative structure-property relationships (QSPR) models were developed for the prediction of food preservatives lipophilicity based on a wide set of theoretical molecular descriptors and a set of published experimental chromatographic data. The lipophilicity data have been modeled using linear multivariate regression (MLR) methodology and genetic algorithm (GA) procedure for variable subset selection. The molecular descriptors employed in this study, computed using the DRAGON package, combine two (2D) and three-dimensional (3D) aspects of the molecular structure. The best models revealed some insights into 2D and 3D structural features, the results showing that the use of 3D descriptors did not significantly improve the predictability of preservatives lipophilicity. According to our findings, molecular descriptors including information indices, topological, 3D-MoRSE and WHIM descriptors provide a good prediction of preservatives lipophilicity. The most important descriptors, highly significant in the predictive lipophilicity models of preservatives, were related to the atomic polarizabilities, atomic Sanderson electronegativities and atomic van der Waals volume of the molecules

ABSTRACT

The chromatographic behavior of a series of amino acids compounds was investigated on silica gel chromatographic plates impregnated with various oils (paraffin, olive, sunflower and corn) and different animal fats (pig, pullet, sheep and bear) using mixture of methanol-phosphate buffer in different proportions as mobile phase. The relevance of the obtained results was evaluated by a critical comparison of the lipophilicity parameters with different theoretical lipophilicity and solubility indices. Also some correlation matrices and diagrams were developed for a comparative evaluation of the studied impregnated stationary phases. The results indicated that the oils and some animal fats (pullet and bear) impregnated silica gel plates can be a good alternative in the field of chromatographic lipophilicity estimation of amino acids. In addition, the PCA methodology proved again to offer a realistic characterization of the impregnated plates, both from the retention mechanism and lipophilicity point of view

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Quantitative structure–property relationship models were developed for the prediction of pesticides and some PAH compounds lipophilicity based on a wide set of computational molecular descriptors and a set of experimental chromatographic data. The chromatographic lipophilicity of pesticides has been evaluated by high-performance liquid chromatography (HPLC) using different chemically bonded (C18, C8, CN and Phenyl HPLC columns) stationary phases and two different organic modifiers (methanol and acetonitrile, respectively) in the mobile phase composition. Through a systematic study, by using the classic multivariate analysis, several quantitative structure–property/lipophilicity multi-dimensional models were established. Multiple linear regression and genetic algorithm for the variable subset selection were used. The internal and external statistical evaluation procedures revealed some appropriate models for the chromatographic lipophilicity prediction of pesticides. Moreover, the statistical parameters of regression and those obtained by applying t-test for the intercept (a0) and for the slope (a1) in order to evaluate relationship between experimental and predicted octanol–water partition coefficients in case of the test set compounds, revealed two statistically valid models that can be successfully used in lipophilicity prediction of pesticides.

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The retention behavior of some food synthetic dyes has been studied by RP-HPLC on chemically bonded C18, C8, C16 and CN stationary phases. Using methanol-ammonium acetate (0.08 mol/L, pH=56.76) as mobile phase, a linear behavior of retention parameters throughout the methanol fraction variance was obtained in all cases (r40.99). The patterns of chromatographic behavior of the compounds illustrate high similarities between the C18, C8 and C16 columns, respectively. Highly significant correlations were obtained between experimental lipophilicity indices log kw and j0 estimated on C18 and C8 stationary phases and some computed log P-values. An extensive investigation made for quantitative structure–property (lipophilicity) relationships of studied dyes, using descriptors from Dragon software, multiple linear regression and genetic algorithm, revealed that the molecular descriptors appearing in the best models combine 2-D and 3-D aspects of the molecular structure. The most significant descriptors can be classified as radial distribution function, GETAWAY (autocorrelation), 3D-MoRSE signal, Burden eigenvalues and edge adjacency descriptors.

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The retention behaviour of some selected synthetic dyes have been investigated on RP-18F254S, RP-18W/ UV254 and CNF254S plates using methanol–water mixture in different volume proportions as mobile phases. The RM values of the compounds decreased linearly with increasing concentration of methanol in the mobile phase in all cases. On the basis of the linear relationship between retention (RM) values and volume fraction of methanol, values of RM0 corresponding to 100% water were obtained by extrapolation using five isocratic RM values. The regression determination coefficients obtained for all stationary phases were excellent (higher than 0.99 in all cases). The good regularities of profiles of retention indices (RM and PC1/RM) indicated that the same mechanism (lipophilic interactions) is dominant in all cases and all types of stationary phases (RP-18, RP-18W and CN) appear to be suitable for estimating the lipophilicity of selected synthetic dyes. The chromatographic lipophilicity values (expressed by RM0) estimated on three different stationary phases were not highly correlated between them and also with computed log P values. The best correlations were founded with lipophilicity parameters calculated by Dragon 5.4 software. By using PC1/RM or ?0 values as estimators for lipophilic character of synthetic dyes, the correlation between these values obtained on that three stationary phases were significantly improved, correlation coefficient being higher than 0.92 in some cases.

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The purpose of this study is to develop a simple and fast sample preparation method for synthetic dyes determination from starchbased foods (puddings). Because at sample preparation stage the main problem is to extract quantitatively the dye unchanged, seven different extraction systems were tested. The extractions were carried out using two different techniques: magnetic stirring and sonication. Quantitative determinations were performed using molecular absorption spectrometry and standard calibration method. The efficiency of extraction of eight synthetic food dyes from spiked corn starch samples was evaluated in terms of recovery. The most efficient extraction solvent proved to be ammonia 25%, the recoveries for all dyes (exception for brilliant blue FCF dye) being higher than 92%. Ultrasounds assisted solvent extraction proved to be more efficient than magnetic stirring, leading to a recovery improvement up to 5% in most cases. Finally, commercial pudding samples were analyzed to assess applicability of this extraction procedure. The results obtained for determination of tartrazine in six identical samples showed no significant difference in terms of extracted amount of dye.

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Lipophilcity of some preservatives was determined by reversed phase high performance thin layer chromatography (RP-HPTLC) using methanol–water mixtures in different volume proportions as mobile phase on three stationary phases of different polarity: RP-18F254s, RP-18WF254s and CNF254s plates. The RM values decreased linearly with increasing methanol concentration in the mobile phase in all cases. The regression determination coefficients obtained for all stationary phases were excellent (higher than 0.98 in most cases). The chromatographic behavior of the preservatives on the RP-HPTLC plates used in this study is similar and in a very good agreement with their polarity. Good chromatographic regularities found for retention factors and by applying principal component analysis for all three types of stationary phases indicate that the same lipophilic interactions are dominants in all cases. The relationships between different RP-HPTLC retention parameters (RM0, b, scores of RF-PC1/RF and scores of RM-PC1/RM) and various calculated log P values of the same preservatives show highly significant correlations for all types of stationary phases

ABSTRACT

The chromatographic behaviour of the parabens has been investigated on RP-18F_254S, RP-18WF_254S, CNF_254S, Diol F_254s and silica gel 60F₂₅₄ plates impregnated with different oils (paraffin, olive, sunflower and corn) using methanol-water mixtures in different volume proportions as mobile phases, the regression determination coefficients being excellent (higher than 0.98 for the majority of compounds). Moreover, highly significant correlations were obtained between different experimental indices of lipophilicity (R_M0, band scores corresponding to the first principal component (PC1)) and computed log P values. All types of stationary phases investigated appear to be highly suited for estimating the lipophilicity of the parabens.

ABSTRACT

The chromatographic behavior of some preservatives was performed by reversed-phase high-performance liquid chromatography on C18 (LiChroCART, Purosphere RP-18e), C8 (Zorbax, Eclipse XDB-C8), CN100 (Säulentechnik, Lichrosphere) and NH₂ (Supelcosil LC-NH₂) columns. The lipophilicity estimated for the first time on the first three columns are comparable and very well correlated. The mobile phase was a mixture of methanol–water (0.1% formic acid) in different volume proportions from 40% to 60% (v/v) for RP-C18, RP-C8 and RP-CN100 column (exception for parabens on RP-C8 column—the methanol concentrations being from 55% to 65%) and from 30% to 50% (v/v) for RP-NH₂. Highly significant correlations were obtained between different experimental indices of lipophilicity (log k_w, S, φ₀, mean of k and log k, and scores of k and log k corresponding to the first principal component) and computed log P values, and C8 column seems to be more suited for estimating the lipophilicity of the investigated compounds. These direct correlations offer a very good opportunity to derive powerful predictive models via Collander-type equations. The reliability of scores values as lipophilic indices is shown by their high correlation with the log K_ow obtained using classical “shake-flask” technique, log k_w and also some of the computed log P values. In addition, the results obtained applying PCA to the retention data may be used in interpreting the molecular mechanism of interactions between eluents and stationary phases with different polarity and to explain the chromatographic behavior of compounds. Finally, the “congeneric lipophilicity chart” described by the scores corresponding to the first principal component has the effect of separating compounds from each other more effectively from congeneric ((dis)similarity) point of view. The parabens and tert-butylhydroquinone appeared to be the most lipophilic preservatives.

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Using the multivariate calibration methods, the simultaneous spectrophotometric determination of the interested compounds from binary, ternary or even with a larger number of compound mixtures becomes possible, lessening much the problems concerning spectral interferences. This study successfully applies Principal Component Regression (PCR) to the determination of the food dyes azorubine (E122), tartrazine (E102) and sunset yellow (E110) from their ternary mixtures within 350-610 nm spectral range. The multivariate calibration interval was 2.3-20.8 mg/L for azorubine, 2.5-20.0 mg/L for tartrazine and 2.0-20.0 mg/L for sunset yellow in acetic buffer of pH = 4.66. Five comercial products (powder juice) containing other food additives and some of them other dyes in mixture with at least one of these three mentioned food dyes were successfully analyzed without a preliminary separation step. Statistics and the recovery results in the validation step support the exactness and precision of this method by comparing it to the univariate calibration which is not so performant because of the spectral interferences of the three dyes.

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Rapid separation of 18 synthetic preservatives on the silica gel chemically modified HPTLC plates (RP-18F254s, RP-18wF254s, CN F254s and Nano-SIL Diol/UV254) has been achieved with methanol-water as mobile phase. The development distance was 8 cm in all cases. Identification of the separated preservatives was performed by UV light at l=254 nm. Potassium sorbate, sodium benzoate and ascorbic acid were identified in some soft drinks after sample preparation by solid phase extraction on C18 column.

ABSTRACT

A simple and reliable thin layer chromatography (TLC) method for simultaneous separation of some carotenoids (beta-carotene, lycopene, lutein, astaxanthin and zeaxanthin), retinoids (retinol, retinoic acid, 9-cisretinal and all-trans-retinal) and tocopherols (alpha-tocopherol, gama-tocopherol and delta-tocopherol) was described. For a proper separation of all compounds three different mobile phases (Benzene: Petroleum Ether, 10:90, v/v; Methanol: Benzene: Ethyl acetate, 5:75:20, v/v/v; Benzene: Petroleum Ether, 90:10, v/v) were tested, using silica gel F254 as stationary phase. The visualization was performed under UV light (254 and 365 nm). The presented method is simple and adequate for the separation and identification of these compounds from different matrices, such as pharmaceuticals and foods.

ABSTRACT

Lipophilicity of parabens (methyl-, ethyl-, propyl-, and butyl-paraben) was determined by reversed-phase high-performance thin-layer chromatography on RP-18F254S, RP-18WF254S, RP-CN F254S and Nano-Sil Diol/ UV254 HPTLC plates. The mobile phase was a mixture of methanol-water in different volume proportions. The RM values of the compound decreased linearly with increasing concentration of methanol in the mobile phase in all cases. Retention indices corresponding to pure water (RM0) were determined using five isocratic RM values. The regression correlation coefficients obtained for all stationary phases were excellent (higher than 0.98 for the majority of compounds). In order to compare the experimental lipophilicity of investigated compounds estimated by RM0 and b and the different computed Last message received on 8/31 at 9:43 PM

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Hydrophilic play an important role in human health. The analysis of these compounds is indispensable for monitoring their content in pharmaceuticals and food in order to prevent some human diseases. The separation and of eight hydrophilic vitamins, i.e., B₁, B₂, B₃, B₅, B₆, B₉, B₁₂, and C, was achieved by thin layer chromatography and Raman spectrometry. After chromatographic experiments, the best results were obtained using programmed multiple development. The unambiguous identification of superimposed spots can be done without using standards of vitamins

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The thin-layer chromatographic (TLC) separation of rare earths has been studied using di(2-ethylhexyl)dithiophosphoric acid as complexing agent in the mobile phase. Silica gel H and silica gel H impregnated with 2.5 m NH ₄ NO ₃ were investigated as stationary phases. The TLC behavior of rare earths on these adsorbents was compared using different mixed mobile phases. The best results were obtained by use of ethyl methyl ketone-tetrahydrofuran-di(2-ethylhexyl)dithiophosphoric acid (1 m ), 6.8 + 3.2 + 0.4 ( v/v ), as mobile phase. Double development was used to achieve better separation of consecutive rare earths.

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A quantitative structure–retention and retention–activity relationships investigations were performed on the lipophilicities of some 1,3-oxazolidine systems as estimated by RP-HPTLC retention parameters. The classical R_Mo values were compared with the factors scores obtained by principal component analysis based also onto the TLC retention data. The lipophilicities (R_Mo and factor scores) were correlated with the theoretical molecular descriptors of 1,3-oxazolidine derivatives providing by the ALCHEMY 2000 software package. The reliability of the factor scores values as lipophilic indices are shown by their significant correlation with the classical R_Mo values and other molecular descriptors. In addition, the “lipophilicity chart” described by the first two components, and/or the “lipophilicity space” described by the first three components have the effect of separating compounds from each other most effectively from the congeneric (similarity) aspect point of view. Finally, these findings support the idea that the chromatographic process of the investigated compounds in this paper and consequently their partitioning over a bio-membrane are controlled mainly by lipophilicity.

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The identification of compounds separated by high performance thin layer chromatography (HPTLC) can be made by coupling the HPTLC with Fourier transform infrared (FTIR) spectroscopy. The quality of HPTLC-FTIR spectra is sufficient for identification of unknown substances, and the information is extremely valuable when examined in reference to the spectra of pure compounds, on different portions of the spectrum. If the FTIR spectra are recorded, the identification of compounds that have been separated by HPTLC can be made without using the standards. It is known that the physico-chemical properties of solutes affect their retention parameters. Many molecular parameters have been used in HPTLC studies to find the relationship between chemical structure and chromatographic retention. The correlation between several properties of Phthalazine derivatives such as dipole moment, polarizability, and surface area, and the retention parameters of these compounds, can be realized. The dipole moment was found to be an important descriptor, and this property of the compounds has a major influence on the retention parameter