Application of Liquid-Liquid Microextraction-High-Performance Thin-Layer Chromatography for Preconcentration and Determination of Phenolic Compounds in Aqueous Samples

JPC – Journal of Planar Chromatography – Modern TLC - A novel liquid-phase microextraction method coupled with high-performance thin-layer chromatography (HPTLC) for preconcentration,...     

Development and Validation of a Planar Chromatographic Method with Reflectance Scanning Densitometry for Quantitative Analysis of Anastrozole in the Bulk Material and in Tablet Formulations

JPC – Journal of Planar Chromatography – Modern TLC - A new quantitative densitometric HPTLC method has been developed for analysis and determination of the stability of anastrozole,...     

Development of a Validated Stability-Indicating High-Performance Thin-Layer Chromatographic Method for the Quantification of Levetiracetam

JPC – Journal of Planar Chromatography – Modern TLC - Levetiracetam (LT) is an FDA-approved orally active anticonvulsant drug. A high-performance thin-layer chromatographic (HPTLC)...     

A Simple and Reliable HPTLC Method for the Determination of Four Marker Components in the Quality Control of Alstonia scholaris

JPC – Journal of Planar Chromatography – Modern TLC - A new, simple, reliable, and validated high-performance thin-layer chromatographic (HPTLC) method has been developed for the...     

Quantification and Isolation of Plumbagin (Plumbago zeylanica Linn.) by High-Performance Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - A simple, rapid, selective, and quantitative high-performance thinlayer chromatographic (HPTLC) method has been developed for the...     

Amino acid and vitamin determinations by TLC/HPTLC: review of the current state

Several methods to determine amino acids and vitamins in biological and pharmaceutical samples have been reported. Thin layer chromatography (TLC) finds its place when the relatively costly equipment required by other methods is unavailable. This review covers the 1991–2010 literature on TLC/HPTLC (high performance thin layer chromatography) amino acid and vitamin determinations. It gives an overview of the special features as well as the problems in TLC/HPTLC determinations of amino acids and vitamins. Various chromatographic systems useful in amino acid and vitamin identification, separation and quantitation of are presented in tabular form. Future prospects of TLC/HPTLC for amino acid and vitamin determinations are also discussed.      

Determination of cortisol in guinea pig urine by high performance thin-layer chromatography, high performance liquid chromatography, and thin-layer chromatography/radioimmunoassay

Summary In order to collect urinary samples from unrestrained guinea pigs, animals were kept in their familiar home cages with wood shavings for bedding. Cortisol was removed from shavings by a simple washing step, and an attempt was made to measure its concentrations by high performance thin-layer chromatography (HPTLC), high performance liquid chromatography (HPLC), or thin layer chromatography/radioimmunoassay (TLC-RIA). After intramuscular administration of 25 mg cortisol, cortisol excretion increased from about 20–30 μg/day to 400–500 μg/day (HPTLC: 531 μg/day, HPLC: 493 μg/day; TLC-RIA: 394 μg/day). Similarly, the treatment of the animals with 20 IU ACTH resulted in an augmented cortisol excretion, with mean values of 294 μg/day (HPTLC), 256 μg/day (HPLC) and 143 μg/day (TLC-RIA), respectively. The present study shows, for the first time, that cortisol excretion in unrestrained laboratory animals can be determined. Whilst the cortisol values measured by HPTLC and HPLC agree, the amounts measured by TLC-RIA were significantly lower. These differences are probably due to the presence of substances in urine or shavings which interfere with the radioimmunological determination. Hence, cortisol should be determined either by HPTLC or HPLC. Beside having a desirable specificity, these methods are more suited than TLC/RIA for steroid analysis since they confer the possibility of measuring additional steroids (e.g. precursors and/or metabolites of cortisol) in a single urine extract. This is especially the case for the HPTLC method since substances can be transformed into fluorescent derivatives.     

Determination of chenodeoxycholic acid on 3-cyanopropyltrichlorosilane-treated high-performance thin-layer chromatographic plates

Summary Chenodeoxycholic acid in commerical drugs was analyzed by high-performance, thin-layer chromatography (HPTLC) using a cyanoalkyl chemically-bonded stationary phase, prepared by treating pre-coated silica with 3-cyanopropyltrichlorosilane (3CPTS). The 3CPTS-treated plates were used to evaluate commerical chenodeoxycholic acid in drug capsules. After development with methanol on the 3CPTS-treated plate, the chenodeoxycholic acid spot in the chromatogram was measured with a TLC densitometer equipped with a dual-wave length TLC scanner at λ=370nm. By this method, the fluorescence intensity of chenodeoxycholic acid was measured within 2.6% error over the range 30–240ng and the limit of detection was 30ng.     

Critical evaluation of experimental conditions influencing the surface-enhanced Raman spectroscopic (SERS) detection of substances separated by layer liquid chromatographic techniques

Summary Surface-enhanced Raman spectra (SERS) ofp-dimethylaminobenzylidenerhodanine have been recorded on silica gel 60 F₂₅₄ and Si60 F₂₅₄ Raman TLC plates. Spectra were enhanced by use of a silver sol prepared according to the modified Lee-Meisel procedure. The standard deviations of the intensities and the band ratios for the seven most intense peaks were calculated for 30 parallel measurements. Although the Raman plate gives more reproducible results, several experimental difficulties are encountered in the development of chromatograms. SERS detection of ascorbigen and 1′-methylascorbigen was performed after chromatography on silica gel 60 F₂₅₄ TLC and HPTLC plates and on Si60 F₂₅₄ Raman TLC plates. Traditional development was used for the silica gel 60 F₂₅₄ TLC plates and Si60 F₂₅₄ Raman plates, and the personal OPLC technique for the silica gel 60 F₂₅₄ HPTLC plates. It was found that the SERS spectrum gave information about the indole ring only. Because bonding of the analyte to the stationary phase results in a change in molecular conformation-in contrast with the behaviour of rhodanine-the type of the plateused and the development procedure employed can significantly influence the quality of the SERS spectrum. Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary September 1–3, 1999     

Fast quantitation of 5-hydroxymethylfurfural in honey using planar chromatography

An approach for rapid quantitation of 5-hydroxymethylfurfural (HMF) in honey using planar chromatography is suggested for the first time. In high-performance thin-layer chromatography (HPTLC) the migration time is approximately 5 min. Detection is performed by absorbance measurement at 290 nm. Polynomial calibration in the matrix over a range of 1:80 showed correlation coefficients, r, of ≥ 0.9997 for peak areas and ≥ 0.9996 for peak heights. Repeatability in the matrix confirmed the suitability of HPTLC–UV for quantitation of HMF in honey. The relative standard deviation (RSD, %, n = 6) of HMF at 10 ng/band was 2.9% (peak height) and 5.2% (peak area); it was 0.6% and 1.0%, respectively, at 100 ng/band. Other possible detection modes, for example fluorescence measurement after post-chromatographic derivatization and mass spectrometric detection, were also evaluated and can coupling can be used as an additional tool when it is necessary to confirm the results of prior quantitation by HPTLC–UV. The confirmation is provided by monitoring the HMF sodium adduct [M + Na]⁺ at m/z 149 followed by quantitation in TIC or SIM mode. Detection limits for HPTLC–UV, HPTLC–MS (TIC), and HPTLC–MS (SIM) were 0.8 ng/band, 4 ng/band, and 0.9 ng/band, respectively. If 12 μL honey solution was applied to an HPTLC plate, the respective detection limits for HMF in honey corresponded to 0.6 mg kg⁻¹. Thus, the developed method was highly suitable for quantitation of HMF in honey at the strictest regulated level of 15 mg kg⁻¹. Comparison of HPTLC–UV detection with HPTLC–MS showed findings were comparable, with a mean deviation of 5.1 mg kg⁻¹ for quantitation in SIM mode and 6.1 mg kg⁻¹ for quantitation in TIC mode. The mean deviation of the HPTLC method compared with the HPLC method was 0.9 mg kg^-1 HMF in honey. Re-evaluation of the same HPTLC plate after one month showed a deviation of 0.5 mg kg⁻¹ HMF in honey. It was demonstrated that the proposed HPTLC method is an effective method for HMF quantitation in honey.      

Densitometric Thin-Layer Chromatography of Protease Inhibitors in Pharmaceutical Preparations

JPC – Journal of Planar Chromatography – Modern TLC -     

Some Technical Problems Associated with Temperature-Controlled Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC -     

Recycled X-Ray Films as an Alternative Support for Thin-Layer Chromatography Plates

JPC – Journal of Planar Chromatography – Modern TLC -     

Identification and Quantification of Tocopherols in Vegetable Oils by Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC -     

Quantitative Determination of Four Water-Soluble Compounds in Herbal Drugs from Lamiaceae Using Different Chromatographic Techniques

HPTLC-densitometric and HPLC–UV techniques were used for qualitative and quantitative determination of luteolin-7-O-glucuronide, lithospermic acid, rosmarinic acid and caffeic acid in several herbal drugs from the Lamiaceae family: Thymi herba, Serpylli herba, Majoranae herba and Menthae piperitae folium. Unmodified silica gel (HPTLC Si60) and silica gel chemically modified with aminopropyl groups (HPTLC NH₂) were used during the investigation process. Among HPTLC methods the best resolution and selectivity was achieved with mobile phases: diisopropyl ether–acetone–formic acid–water (50:30:10:10, v/v/v/v) and acetone–formic acid (85:15, v/v), respectively. Plates were densitometrically evaluated. Contents of analyzed compounds in the studied aqueous extracts prepared from herbal drugs were established using both techniques. The results from the HPTLC-densitometric analysis have been compared with those from HPLC–UV on a C18 column with acetonitrile–water–formic acid as a mobile phase. The chromatographic methods were validated for linearity, LOD, LOQ, repeatability, intermediate precision and recovery. An analysis of variance showed that the HPTLC-densitometric and HPLC–UV methods are equivalent and sufficiently precise for the estimation of polyphenolic compounds mentioned above, in investigated herbal drugs. All of the suggested methods (HPTLC NH₂, HPTLC Si60 and HPLC RP18) give results with good agreement.     

A methodological and metabolite identification study of the metabolism of S-carboxymethyl-L-cysteine in man

Summary The analysis of 08:00–16:00 (0–8) hour urine collections following oral S-carboxymethyl-L-cysteine administration of 750 mg to 30 individuals identified S-carboxymethyl-L-cysteine, S-carboxymethyl-L-cysteine S-oxide, S-methyl-L-cysteine and S-methyl-L-cysteine S-oxide as the major urinary drug related compounds. No S-(carboxymethylthio)-L-cysteine mixed disulphide metabolite was found in the 08:00–16:00 hour urine collection but the metabolite was detected in the 16:00–00:00 (8–16) hour urune collection by paper chromatography, TLC and HPLC. The production of the S-oxide metabolites 08:00–16:00 hour urine collection) and the mixed disulphide metabolite (16:00–00:00 hour urine collection) were both shown to be biomodally distributed. A significant linear correlation of the S-oxides recovered following 08:00–16:00 hour urine collection as analysed by paper chromatography, TLC and HPLC is reported.     

Investigation of the Separation of Higher Fatty Acid Methyl Esters by Reversed-Phase HPTLC

JPC – Journal of Planar Chromatography – Modern TLC - Separations of eight methyl esters of higher fatty acids on RP-18 stationary phase with methanol—water and...     

Planar Chromatography of Cholic Acid-Derived cis—trans Isomeric bis-Steroidal Tetraoxanes

JPC – Journal of Planar Chromatography – Modern TLC - Seven pairs of cis—trans isomers of bis-steroidal tetraoxanes have been examined by both normal-phase (NP) and reversed-phase...     

Densitometric HPTLC Analysis of the 5-Hydroxymethylfurfural Content of Turkish Fruit Wines and Vinegars

JPC – Journal of Planar Chromatography – Modern TLC - A thin-layer chromatographic method with densitometric UV detection at 286 nm after ethyl acetate extraction is described for...     

Planar Dielectrochromatography on Non-Wetted Thin Layers

JPC – Journal of Planar Chromatography – Modern TLC - Some of the physical properties of dielectric liquids are influenced by electric fields. Interesting results were obtained in this...