Showing papers on "Thin-layer chromatography published in 2008"

Mycotoxin analysis: an update.

Abstract: Mycotoxin contamination of cereals and related products used for feed can cause intoxication, especially in farm animals. Therefore, efficient analytical tools for the qualitative and quantitative analysis of toxic fungal metabolites in feed are required. Current methods usually include an extraction step, a clean-up step to reduce or eliminate unwanted co-extracted matrix components and a separation step with suitably specific detection ability. Quantitative methods of analysis for most mycotoxins use immunoaffinity clean-up with high-performance liquid chromatography (HPLC) separation in combination with UV and/or fluorescence detection. Screening of samples contaminated with mycotoxins is frequently performed by thin layer chromatography (TLC), which yields qualitative or semi-quantitative results. Nowadays, enzyme-linked immunosorbent assays (ELISA) are often used for rapid screening. A number of promising methods, such as fluorescence polarization immunoassays, dipsticks, and even newer methods such as biosensors and non-invasive techniques based on infrared spectroscopy, have shown great potential for mycotoxin analysis. Currently, there is a strong trend towards the use of multi-mycotoxin methods for the simultaneous analysis of several of the important Fusarium mycotoxins, which is best achieved by LC-MS/MS (liquid chromatography with tandem mass spectrometry). This review focuses on recent developments in the determination of mycotoxins with a special emphasis on LC-MS/MS and emerging rapid methods.

Thin Layer Chromatography in Phytochemistry

Abstract: Thin layer chromatography in phytochemistry , Thin layer chromatography in phytochemistry , کتابخانه دیجیتال جندی شاپور اهواز

Isolation of ursolic acid from apple peels by high speed counter-current chromatography

Abstract: Cuticular waxes of four varieties of Malus domestica were investigated regarding their content of ursolic acid. Peels from Fuji, Gala, Smith and Granny Smith apples were extracted with chloroform, ethyl acetate and/or ethanol. The crude extracts were purified by high speed counter-current chromatography (HSCCC), by using mobile and stationary phases derived from the two-phase solvent system composed by n-hexane:ethyl acetate:methanol:water in the proportion of 10:5:2.5:1. The phase proportions and the relative distribution of ursolic acid between the two-phases were optimized by TLC and optical densitometry, by comparison with an authentic sample of ursolic acid. The amount of ursolic acid present in the extracts as well as the characterization of the isolated compound were made by high resolution gas chromatography coupled to mass spectrometry (GC–MS), 13C nuclear magnetic resonance (13C NMR), Infrared; and by comparing thin layer chromatography and flame ionization detection gas chromatography (GC–FID) patterns with the commercial sample. The average content of ursolic acid of 0.8 mg/cm2 in the peel (around 50 mg per medium sized fruit with a surface area of 50–70 cm2) was found in the Fuji and Smith varieties, whereas 0.5 mg/cm2 and 0.2 mg/cm2 were the amounts calculated for Granny Smith and Gala, respectively. The HSCCC technique was shown to be a good method to purify free ursolic acid from apple peels and could represent a new technological tool to be developed to exploit industrially this source of product.

Variants of Lipopeptides Produced by Bacillus licheniformis HSN221 in Different Medium Components Evaluated by a Rapid Method ESI-MS

Abstract: A lipopeptide producing strain was isolated from an oil field and identified as Bacillus licheniformis HSN221. Nine different substrates were used to cultivate the strain under the same incubation conditions. Using a rapid method, Electrospray Ionization Mass Spectrometry (ESI-MS) combined with Thin Layer Chromatography (TLC), nine different lipopeptide homologues were found and identified. The strain produced four [Leu]surfactin homologues, surfactin C13, surfactin C14, surfactin C15 and surfactin C16, when cultivated in the medium with glucose, yeast extract and ammonium chloride, but it produced five lichenysin homologues, lichenysin C12, lichenysin C13, lichenysin C14, lichenysin C15 and lichenysin C16, when cultivated in the remaining eight media. Additionally, it showed that the type and relative content of each homologue were consistent with in each medium which is helpful for optimizing the medium components to cultivate the similar species.

Simultaneous estimation of acetylsalicylic acid and clopidogrel bisulfate in pure powder and tablet formulations by high-performance column liquid chromatography and high-performance thin-layer chromatography.

Abstract: This paper describes validated high-performance column liquid chromatographic (HPLC) and high-performance thin-layer chromatographic (HPTLC) methods for simultaneous estimation of acetylsalicylic acid (ASA) and clopidogrel bisulfate (CLP) in pure powder and formulations. The HPLC separation was achieved on a Nucleosil C8 column (150 mm length x 4.6 mm id, 5 microm particle size) using acetonitrile-phosphate buffer, pH 3.0 (55 + 45, v/v) mobile phase at a flow rate of 1.0 mL/min at ambient temperature. The HPTLC separation was achieved on an aluminum-backed layer of silica gel 60F254 using ethyl acetate-methanol-toluene-glacial acetic acid (5.0 + 1.0 + 4.0 + 0.1, v/v/v/v) mobile phase. Quantitation was achieved with UV detection at 235 nm over the concentration range 4-24 microg/mL for both drugs, with mean recoveries of 99.98 +/- 0.28 and 100.16 +/- 0.66% for ASA and CLP, respectively, using the HPLC method. Quantitation was achieved with UV detection at 235 nm over the concentration range of 400-1400 ng/spot for both drugs, with mean recoveries of 99.93 +/- 0.55 and 100.21 +/- 0.83% for ASA and CLP, respectively, using the HPTLC method. These methods are simple, precise, and sensitive, and they are applicable for the simultaneous determination of ASA and CLP in pure powder and formulations.

Speciation of chromium by high-performance thin-layer chromatography with direct determination by laser ablation inductively coupled plasma mass spectrometry.

Abstract: It is of considerable importance to be able to distinguish metallic species because their toxicity depends on their chemical form. Therefore, the analysis of environmental samples can be enhanced by the combination of high-performance thin-layer chromatography (HPTLC) with laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). In this study, Cr (3+) and Cr (6+) were separated on silica gel HPTLC plates using aqueous mobile phases. Separation was achieved in seconds with retardation factors ( R f ) of 0 and 1 for Cr (3+) and Cr (6+), respectively. LA was used to volatilize the chromium species directly from the chromatographic material prior to ICPMS detection. A linear calibration was obtained, and detection limits (3sigma) of 6 ng for Cr (6+) and 0.4 ng for Cr (3+) were achieved with precision ranging from 3 to 40% at the 95% confidence level. The silicon present in the stationary phase was used as an internal standard. This procedure allows for a rapid separation and quantification, requires only 0.5 muL of sample, and lower detection limits can be achieved through preconcentration.

Structural elucidation of a tadalafil analogue found in a dietary supplement.

Abstract: A tadalafil analogue was detected in a dietary supplement marketed for tonic effect, along with hydroxyhomosildenafil and aminotadalafil. The tadalafil analogue was isolated by preparative thin layer chromatography (TLC) and its structure was elucidated using high-performance liquid chromatography (HPLC), liquid chromatography electrospray ionization-mass spectrometry (LC-ESI-MS), Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS) and nuclear magnetic resonance (NMR) spectroscopy. The compound was determined to be methyl-1-(1,3-benzodioxol-5-yl)-2-(chloroacetyl)-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole-3-carboxylate.

Comparison of high performance TLC and HPLC for separation and quantification of chlorogenic acid in green coffee bean extracts.

Abstract: Two chromatographic methods, high-performance TLC (HPTLC) and HPLC, were developed and used for separation and quantitative determination of chlorogenic acid in green coffee bean extracts For HPTLC silica gel Kieselgel 60 F 254 plates with ethyl acetate/dichlormethane/formic acid/acetic acid/water (100:25:10:10:11, v/v/v/v/v) as mobile phase were used Densitometric determination of chlorogenic acid by HPTLC was performed at 330 nm A gradient RP HPLC method was carried out at 330 nm All necessary validation tests for both methods were developed for their comparison There were no statistically significant differences between HPLC and HPTLC for quantitative determination of chlorogenic acid according to the test of equality of the means

Purification and partial characterization of antifungal metabolite from Paenibacillus lentimorbus WJ5

Abstract: Paenibacillus lentimorbus strain WJ5, a soil isolate showed in vitro antagonistic activity against several fungal phytopathogens belonging to the ascomycetes, basidiomycetes and oomycetes. The antifungal metabolite was extracellular and could be extracted with n-butanol. Its production was initiated at the end of the exponential phase, reaching a maximum after 5 days incubation at 30°C. Crude extract of the antifungal metabolite was thermostable (121°C for 3 h) and no loss of activity was recorded when exposed to proteinase K, sodium dodecyl sulphate (1%), Tween-80 (1%) and glycerol (1%). However, cationic hexadecyltrimethylammonium bromide and lysozyme inactivated the metabolite. The antifungal metabolite was purified by silica gel thin layer chromatography and Sephadex LH-20 size exclusion chromatography. Loss of activity during acid hydrolysis indicated the peptide nature of the antifungal metabolite. The FT-IR spectrum of the antifungal metabolite confirmed the presence of the peptide and glycosidic bonds.

Determination of pesticides in water samples from the Wieprz-krzna Canal in the Leczyńsko-Włodawskie Lake District of southeastern Poland by thin-layer chromatography with diode array scanning and high-performance column liquid chromatography with diode array detection.

Abstract: High-performance thin-layer chromatography with diode array scanning (TLC-DAD) and high-performance column liquid chromatography with a diode array detector (HPLC-DAD) were used to screen water samples for pesticides. Atrazine, clofentezine, chlorfenvinphos, hexaflumuron, terbuthylazine, lenacyl, neburon, bitertanol, and metamitron were enriched from canal water samples by solid-phase extraction (SPE) on octadecyl silane (C18)/styrene-divinylbenzene-1, C18, C18 Polar Plus, and cyanopropyl (CN) cartridges. Recovery rates were high for all extraction materials except CN, for which values for all pesticides were lower. SPE was used for both preconcentration and fractionation of the analytes. Analytes were eluted by means of methanol and dichloromethane. Methanol eluates were analyzed by HPLC-DAD and dichloromethane eluates by TLC-DAD. The method was validated for precision, repeatability, and accuracy. Calibration graphs were linear between 0.1 and 50.0 microg/mL for all pesticides, and correlation coefficient (r) values were between 0.9994 and 1.000 as determined by HPLC-DAD. Calibration graphs were linear between 0.1 and 1.5 microg/spot for all pesticides, and r values were between 0.9899 and 0.9987 as determined by TLC-DAD. The limit of detection was between 0.04 and 0.23 microg/spot for TLC-DAD and 0.02 and 0.45 microg/mL for HPLC-DAD.

Chronology of thin-layer chromatography focusing on instrumental progress

Abstract: 1938. N.A. Izmailov and M.S. Shraiber, at the Pharmaceutical Institute in Kharkov (Ukraine), analyzed plant tinctures by placing a drop of sample solution on a horizontal 2 mm layer of aluminum oxide without binder on a glass microscope slide. Methanol mobile phase was added dropwise to produce concentric circles of separated zones that were detected by their different colors under illumination with ultraviolet (UV) light from a lamp. This was the first use of thin-layer chromatogram development with mobile phase, similar to Tswett’s column method. They used loose layers and circular development. The technique was called ‘spread layer chromatography’ or ‘spot chromatography’. Of course this is different from the practice of TLC today; how-ever, they described the basic principle underlying the TLC process.

Evaluation of the water and organic liquids extraction efficiency of Spirulina maxima dyes using thermostated micro thin-layer chromatography.

Abstract: Thermostated micro thin-layer chromatography was applied for separation and quantification studies of Spirulina maxima dyes isolated from pharmaceutical formulation by a simple one-step liquid extraction. The isolation process was performed using a number of liquids, including water; 10 mM water solutions of native alpha-, beta-, and gamma-cyclodextrin and their hydroxypropyl derivatives; and a number of common organic liquids characterized by different polarity, namely, methanol, ethanol, 1-propanol, 2-propanol, acetonitrile, acetone, tetrahydrofuran, dichloromethane, toluene, and n-hexane. Chromatographic studies were performed on RP18W plates working inside a small thermostated horizontal chamber allowing a development distance of 45 mm. Using a mobile phase consisting of acetone-n-hexane (30 + 70, v/v) and 40 degrees C separation temperature, plate peak capacity of at least 15 spots/lane and developing time <5 min were obtained. Validation data indicated that under such conditions, with an office scanner used for chromatogram digitalization, spot quantification could be accurately performed within an analyte mass range of 2 factors. The raw quantitative data obtained from microchromatograms acquired under visible light conditions were explored using cluster analysis and principal components analysis. Chemometric investigations revealed that the best extraction liquids for isolation of dye mixtures from Spirulina samples were methanol, ethanol, tetrahydrofuran, and dichloromethane. Moreover, it was found that the liquids' parachor values could be used for estimation of the dye extraction efficiency from complex samples.

Determination of the veterinary drug maduramicin in food by fluorescence polarisation immunoassay

Abstract: Summary A fluorescence polarisation immunoassay (FPIA) using a specific polyclonal antiserum for the detection of maduramicin (MD) was developed and optimised. The polyclonal antiserum was produced against MD linked to bovine serum albumin. Fluorescein-labelled MD (tracer) was synthesised by N-hydroxysuccinimide active ester method and purified using thin layer chromatography. The developed FPIA for MD had a dynamic range from 0.01 to 5.6 μg mL−1 with an IC50 value of 0.16 μg mL−1 and a limit of detection of 0.002 μg mL−1. Recoveries from chicken muscle, fat and egg samples spiked at 0.25, 5 and 10 μg g−1 levels were 82–130%. The FPIA results from analysis of incurred residues in chicken muscle samples showed that the simple procedure is viable.

Separation and quantitation of jasmonic acid using HPTLC.

Abstract: A rapid, simple, and stringent protocol for the detection and quantitation of jasmonic acid (JA) is designed using highperformance thin-layer chromatography. Acidified culture filtrate of Lasiodiplodia theobromae is extracted with an equal volume of ethyl acetate and spotted on silica gel 60 F 254 foil using Linomat-5 spray-on applicator. Standard JA is also spotted either internally or adjacent to the sample, and the foils are developed with isopropanol‐ammonia‐water [10:1:1 (v/v)] as the mobile phase. A quantitative estimation of the separated JA is performed by measuring the absorbance at 295 nm in the reflective mode. The sensitivity of the method is improved by adding internal standard to obtain a detection limit of 1 µg. The limit of quantitation is found to be 80 µg with this method. The method is shown to have selectivity, accuracy, precision, and high sample throughput, making it useful for the routine analysis of JA in basic science and perfumery industries.

TLC of Alkaloids on Cyanopropyl Bonded Stationary Phases. Part II. Connection with RP18 and Silica Plates

Abstract: Some standards of the alkaloids and synthetic or natural mixtures are separated by two-dimensional thin-layer chromatography (TLC) on different adsorbent layers. Normal- and reversed-phase systems are used to obtain significant differences in the separation selectivity. Optimization of the one-dimensional TLC separation of the alkaloids’ standards is performed on cyanopropyl-silica, RP18W, and silica layers in various eluents containing (besides diluent and modifier) silanol blockers, such as diethyl amine or ammonia. The most selective systems are used for the separation of the alkaloids’ mixtures by two-dimensional TLC with an adsorbent gradient method. The mixtures of alkaloids or plant extracts (Chelidonium majus, Fumaria officinalis, or Glaucium flavum) are chromatographed in system I; the plates are connected with the plate pre-coated with various adsorbent, and partly separated fractions are transferred to the second layer and developed in system II. CN-silica‐RP18W and CN-silica‐silica are used as the connected layers. The alkaloids are identified by R F values of standards, and the components of plant extracts are identified in both systems, and by the comparison of UV spectra obtained in diode array detector denistometry.

Preparation and biodistribution of [111In]-rHuEpo for erythropoietin receptor imaging

Abstract: Human recombinant erythropoietin (EPO) was successively labeled with [111In]-indium chloride after conjugation with freshly prepared cyclic DTPA-dianhydride (ccDTPA). The best results of the conjugation were obtained by the addition of 100 i.u. of an EPO pharmaceutical solution (in phosphate buffer, pH 7.5) to a glass tube pre-coated with DTPA-dianhydride (0.01 mg) at 25 °C with continuous mild stirring for 30 minutes. Radio thin layer chromatography (RTLC), instant thin layer chromatography (ITLC) and high performance liquid chromatography (HPLC) showed overall radiochemical purity of higher than 95% at optimized conditions (specific activity = 1.2–1.5 GBq/mg, labeling efficiency 80%). Preliminary in vivo studies in normal rat model was performed to determine the biodistribution of the radiotracer up to 1 hour using scarification. The high kidney uptake of the tracer was consistent with the reported EPO receptor distribution.

Application of temperature-controlled micro planar chromatography for separation and quantification of testosterone and its derivatives.

Abstract: Temperature-controlled micro thin-layer chromatography (TLC) was applied for separation and quantification studies of testosterone and its derivatives including methyltestosterone, testosterone propionate, isobutyrate, phenylpropionate, isocaproate, enanthate and caprate. Chromatographic studies were performed on silica-, octadecylsilica- and aluminum-coated plates working inside a small thermostated horizontal chamber unit allowing one-dimensional and two-dimensional developing modes with an elution distance of 45 mm. Retention properties of steroids were investigated across a whole range of binary mixtures such as methanol/water, acetonitrile/water, methanol/dichloromethane and acetone/hexane (0–100% v/v). Moreover, the effect of temperature ranging from −20 to +60 °C under saturated and unsaturated chamber conditions was also investigated. Our results revealed that depending on the mobile phase polarity the separation system based on the low carbon load wettable with water RP18W plates may work as a normal-phase (NP) or reversed-phase (RP) chromatographic system. It has been also demonstrated that micro TLC equipment can be applied as a fast retention screening device as well as simple and robust quantitative tool for determination of testosterone residue containing testosterone derivatives in complex samples.

ISOLASI DAN IDENTIFIKASI SENYAWA YANG BERPOTENSI SEBAGAI ANTITUMOR PADA DAGING BUAH PARE (Momordica charantia L.)

Abstract: Isolation and identification of the compound which has a potency as antitumor from bitter melon have been carried out. Extraction was conducted n-hexane, chloroform, and ethanol respectively using each extracts obtained were examined with brine shrimp lethality test. The most toxic extract was ethanol extract (LC50 223 ppm). Separation and purification of the compounds from the ethanol extract were conducted by column chromatogaraphy using a gel silica 60 as the stationary phase and benzene : acetic acid ( 8:2) as the mobile phase. This yielded 3 fractions. Then the fractions were examined with brine shrimp lethality test and the most toxic fraction was found to be the fraction 1 (LC50 31,62 ppm), but the fraction that was analysed further was fraction 3 (LC50 100 ppm), because fraction 1 consists of using compounds that were difficult to separate. The purity fraction 3 was tested conducted thin layer chromatography and its activity as antitumor agent was tested using Agrobacterium tumefacien A-208. The test was in 6 weeks and that fraction 3 has a potency as an antitumor agent at 1000 ppm. The identification with gas chromatography – mass spectroscopy indicate that the antitumor isolate from bitter melon contains 3 mayor compoundsnamely dioxtyl hexadioate esther, palmitic acid, stearic acid.

Chemical stability of haloperidol injection by high performance thin‐layer chromatography

Abstract: The chemical stability of haloperidol lactate injection was studied under different storage conditions by high performance thin-layer chromatography (HPTLC). The study was performed at 25 +/- 2 degrees C and at refrigeration temperature (8 +/- 1 degrees C) in original glass ampoules over 15 days after being opened. The samples tested at 25 +/- 2 degrees C were stored with exposure to and protection from light. Chromatographic separation was achieved on precoated silica gel F 254 HPTLC plates using a mixture of acetone/chloroform/n-butanol/glacial acetic acid/water (5:10:10:2.5:2.5, v/v/v/v/v) as a mobile phase. Quantitative analyses were carried out at a wavelength of 254 nm. The method exhibited adequate linearity (r = 0.999), selectivity, precision (RSD = 1.92%), and accuracy (recoveries from 98.59 to 101.90%). The concentrations of all samples remained greater than or 90% of the original concentration. Haloperidol lactate injection was chemically stable under all conditions studied over 15 days.

Sea weed sesquiterpenoids as well as preparation method and application thereof

Abstract: The invention relates to a seaweed sesquiterpenoids, the preparation method and the application of the seaweed sesquiterpenoids, belonging to antifeedant pesticide field The structural formula is as (I) The preparation method comprises to wash, shade dry, crush and extract the marine red alga Laurencia okamurai Yamada for two to five times by organic solution; to merge and concentrate the extractant so as to get the crude extract; after silica column chromatography to the crude extract and gradient elution with organic solvent, the eluent is collected and tested by thin layer chromatography; being eluented at gradient volume ratio of 20-30:1, the component is purified to achieve target compound I after silica column chromatography and thin layer chromatography separation The preparation method for seaweed sesquiterpenoids has the advantages of having significant antifeedant and insecticidal activity of the products, utilizing Laurencia okamurai Yamada further as pollution-free marine biogenic pesticides, having easy operation, good reproducibility and other advantages

Thin Layer Chromatography/Fluorescence Detection of 3,4‐Methylenedioxy‐Methamphetamine and Related Compounds

Abstract: A rapid and sensitive method for the detection of six methylenedioxylatedphenethylamines, 3,4-methylenedioxymethamphetamine (MDMA); 3,4-methylenedioxyamphetamine; 3,4-methylenedioxyethylamphetamine; N-methyl-1-(3,4-methylenedioxyphenyl)-2-butamine; N-methyl-1-(3,4-methylenedioxyphenyl)-3-butamine; and 3,4-methylenedioxydimethylamphetamine, by thin-layer chromatography with fluorescence detection is proposed. These compounds form fluorophores on the developing plate following spraying with a reagent consisting of sodium hypochlorite, potassium hexacyanoferrate (III), and sodium hydroxide, and heating for 3 min at 100 degrees C. Blue fluorescent spots were observed under ultraviolet light in a wavelength range of 250-400 nm. The detection limits for MDMA and the above related compounds were 50 ng. The proposed method was effectively applied to the detection of MDMA in urine samples.

Two-Dimensional Thin-Layer Chromatography of Structural Analogs. Part II. Method for Quantitative Analysis of Selected Coumarins in Plant Material

Abstract: Coumarins are interesting group of natural compounds, because of their biological and pharmacological activity, and are widely investigated. They are normally found in complex mixtures, e.g. plant extracts, and are difficult to separate in one chromatographic run. Mixtures of coumarins have been separated by two-dimensional thin-layer chromatography on CN-silica plates by use of aqueous and nonaqueous mobile phases. Complete separation was also achieved by use of graft thin-layer chromatography on connected layers — silica with RP-18W or CN-silica with silica. The systems characterized by the best efficiency and selectivity were used for separation of coumarin fractions from extracts of selected Apiaceae plants. These orthogonal systems were used for quantitative analysis of selected coumarins. The results obtained show two dimensional thin-layer chromatography is useful tool for quantification of some furanocoumarins in plant extracts. The best results were obtained on connected silica and octadecyl silica layers.

Preparative-Scale Chromatography of Ecdysteroids: A Class of Biologically Active Steroids

Abstract: A simple separation procedure is developed for the isolation of the main phytoecdysteroid 20-hydroxyecdysone from the herb Silene viridiflora. The purification in four steps uses only a simple preparative-scale separation technique (i.e., liquid-liquid extraction, precipitation, solid-phase extraction on octadecyl silica, and crystallization). This procedure is extended using classical normal-phase liquid column chromatography, rotation planar chromatography, and preparative high-performance liquid chromatography for the isolation of the minor ecdysteroids: integristerone A, 26-hydroxypolypodine B, 2-deoxy-20,26-dihydroxyecdysone, and polypodine B. 2-Deoxy-20,26-dihydroxyecdysone is isolated from this species for the first time. The isolation of these ecdysteroids in adequate amounts makes them readily available for insect physiology experiments and for structure-activity relationship studies. The preparative-scale separation work also results in a minor, as yet unknown ecdysteroid.

Lipophilicity of 5′‐Carbonates of Lamivudine with Antiretroviral Activity. Correlation Between Different Methods

Abstract: This study reports on the lipophilicity of novel 5′‐carbonates of lamivudine with anti‐HIV activity. Reversed‐phase thin layer chromatography (RP‐TLC), reversed‐phase high performance liquid chromatography (RP‐HPLC), conventional shake flask (log Poct), and the theoretical CLOGP methods were used, in order to establish if the linear relationships between the conventional and chromatographic methods permit an extrapolation procedure. The nature of the organic modifiers used in the chromatographic techniques did not substantially affect the measurement of lipophilicity, since a good correlation between experimental log Poct and extrapolated RP‐TLC and RP‐HPLC values (RMw and log k′w, respectively) supported the validity of the extrapolation technique.