Akademiai Kiado Zrt.

A thin-layer chromatographic system comprising of silica gel as stationary phase and 1.0% aqueous urea solution as mobile phase (pH 7.44) has been developed for the mutual separation of five-component mixture of amino acids [lysine (RF = 0.38), histidine (RF = 0.59), leucine (RF = 0.78), alanine (RF = 0.87), and glutamic acid (0.98)]. The presence of foreign substances such as metal cations, anions, and vitamins as impurities in the sample on the separation was also examined. Thin-layer chromatographic parameters such as standard deviation (SD), ΔRF, separation factor (α), and resolution (RS) values of separated components of the mixture of these five amino acids were calculated. The limits of detection for lysine, leucine, and alanine were found to be 1.5 µg spot−1, whereas for histidine and glutamic acid, these were 1.2 µg and 3.0 µg spot−1, respectively. The proposed TLC system is applicable for the identification and separation of amino acids in pharmaceutical formulations.

This paper focuses on the study of different types of SPE material that can be used for preconcentration of eight pharmaceuticals from water samples. The compounds studied were enrofloxacine, norfloxacine, Oxytetracycline, trimethoprim, sulfamethazine, sulfadiazine, sulfaguanidine, and penicillin G/procaine. Cartridges were tested on spiked water samples and extraction efficiency was determined by thin-layer chromatography (TLC) CN-modified chromatographic plates with 0.05 m H2C2O4-methanol, 81 + 19, as mobile phase. Strata-X cartridges were proved to be the best type of SPE material for this group of pharmaceutical compounds. For this reason an SPE—TLC method with Strata-X cartridges and HPTLC plates was validated. The method has been applied to the determination of pharmaceutical products in production wastewater samples from the pharmaceutical industry.

Eucalypts are a large group of woody trees with about 900 taxa in 3 genera: Eucalyptus, Corymbia and Angophora. The secondary metabolites of eucalypts have shown a plethora of biological activities. The chemistry behind the activities of eucalypts is being unearthed with advancements in modern medicine and pharmacy. This has demanded the phytochemical profiling of eucalypts with respect to their bioactive constituents. A large number of secondary metabolites (flavonoids, glycosides, triterpenoids, phloroglucinols) from several species of eucalypts have been earlier isolated by our group. In order to develop quick identification of secondary metabolites from eucalypts for de-replication purposes, we thought it worthwhile to develop qualitative HPTLC methods for these compounds in 15 eucalypts (13 Eucalyptus and 2 Corymbia) collected from Australia and India. High-performance thin-layer chromatography (HPTLC) fingerprints using 87 compounds of the above chemical classes of natural products were developed for the quality assessment of eucalypts.

A general equation for determination of relative position, Rpg, of solutes chromatographed under conditions of stepwise gradient elution with one void volume of mobile phase in reverse-phase thinlayer chromatography has been applied to separation of ten component dye mixture. A satisfactory agreement between calculated (by computer program) and experimental values of Rpg has been demonstrated. A device with the new horizontal developing chamber has been applied to the investigations. This device showed practical advantages in comparison to other chambers especially in respect of its application to stepwise gradient elution.

The possibility of using aminopropylsilica TLC plates for determination of phenolic acids has been investigated. Eighteen phenolic acids were chromatographed on aminopropyl-bonded silica with mobile phases comprising mixtures of diisopropyl ether and acetic acid with toluene, petroleum ether, or heptane. The selectivity of the proposed chromatographic systems was satisfactory. The best separations were obtained with heptane–diisopropyl ether–acetic acid, 4 + 5 + 1 (v/v) or petroleum ether–diisopropyl ether–acetic acid, 6 + 3 + 1 (v/v) as mobile phase.

A simple, selective, sensitive, and precise high-performance thin-layer chromatographic technique was followed to determine the diversity within accessions of Solanum nigrum. Fruit, stem, leaf, and root samples extracted in methanol were used to quantify withanolide A and withaferin A. Significant difference has been detected among the different plant parts. The maximum amount of withaferin A has been found to be present in the leaf sample (71.65 ± 2.86 mg g−1 DW), followed by the stem sample, while the least amount of withaferin A has been detected in the mature fruit sample (5.97 ± 1.91 mg g−1 DW).