Amino acids are very important organic compounds in nature. The biological activity of amino acids depends mainly on their stereoisomeric configuration (d- or l-). Thus, the stereochemical analysis of amino acids and peptides is an important aspect of their characterization. Owing to the increasing role of amino acid configuration in biomedical and pharmaceutical studies, numerous analytical methods have been described in the literature. Among a wide range of analytical techniques available for the steroselective separation of different amino acids, which were obtained from plants or biological samples, chromatographic methods such as thin-layer chromatography, high-performance chromatography and also gas chromatography are very useful. This review presents such systems developed for direct stereoisomeric separation and quantitative determination of amino acid and peptide enantiomers with emphasis on selected literature published during two last decades. Almost all aspects, including sample preparation prior chromatographic analysis, stationary phase, solvent system and detection system, are discussed. New possibilities in chiral amino acid analysis have been opened up by the application of mass spectrometry and infrared detection in thin-layer chromatography and mass spectrometry-selected ion monitoring detection system in gas chromatography. A modern trend in high-performance chromatography is two-dimensional chromatography. These innovations have led to decreased development time and increased amino acid resolution and detectability.
This review presents various chromatographic systems, TLC, HPLC, GC, and also SFC, developed for identification and accurate quantification of long-chain mono- and polyunsaturated fatty acids from different samples with emphasis on selected literature which was published during last decade. Almost all the aspects such as preseparation step of fatty acids (cisandtrans), stationary phase, solvent system, and detection mode are discussed.
A new specific, precise, accurate, and robust TLC-densitometry has been developed for the simultaneous determination of hydrocortisone acetate and lidocaine hydrochloride in combined pharmaceutical formulation. The chromatographic analysis was carried out using a mobile phase consisting of chloroform + acetone + ammonia (25%) in volume composition 8 : 2 : 0.1 and silica gel 60F254 plates. Densitometric detection was performed in UV at wavelengths 200 nm and 250 nm, respectively, for lidocaine hydrochloride and hydrocortisone acetate. The validation of the proposed method was performed in terms of specificity, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, accuracy, and robustness. The applied TLC procedure is linear in hydrocortisone acetate concentration range of 3.75 ÷ 12.50 μg·spot−1, and from 1.00 ÷ 2.50 μg·spot−1 for lidocaine hydrochloride. The developed method was found to be accurate (the value of the coefficient of variation CV [%] is less than 3%), precise (CV [%] is less than 2%), specific, and robust. LOQ of hydrocortisone acetate is 0.198 μg·spot−1 and LOD is 0.066 μg·spot−1. LOQ and LOD values for lidocaine hydrochloride are 0.270 and 0.090 μg·spot−1, respectively. The assay value of both bioactive substances is consistent with the limits recommended by Pharmacopoeia.
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