Determination of carboxylic acid salts in pharmaceuticals by high-performance liquid chromatography after pre-column fluorogenic labelling

Determination of urea, allantoin and lysine pyroglutamate in cosmetic samples by hydrophilic interaction chromatography

A new HPLC method using a Polyhydroxyethyl A column involving hydrophilic interaction chromatography (HILIC) is described for the simultaneous determination of urea, allantoin and lysine pyroglutamate in a cosmetic cream. Validation of the method was accomplished with respect to linearity, repeatability and limits of detection/quantification. Compound recoveries approach 100% with acceptable RSD values. The method is very simple since no derivatisation is necessary. Furthermore, it allows the rapid and direct chromatographic analysis of urea and hence could provide an alternative to other methods used to determine this compound in biological or cosmetic samples.

Chromatographic analysis of lipoic acid and related compounds

The analysis of lipoic acid and related compounds, such as its reduced form dihydrolipoic acid, its amide form lipoamide and other analogues, in biological and food samples is important in biochemistry, nutritional and clinical chemistry. This review summarizes the chromatographic methods for the determination of lipoic acid and related compounds, and their applications to various samples such as bacteria, tissues, drugs and food. Gas chromatographic methods with flame ionization detection and flame photometric detection are commonly used for the quantification of lipoic acid present as its protein-bound form, after acid or base hydrolysis of these samples. High-performance liquid chromatographic methods with ultraviolet, fluorescence and electrochemical detection are mainly used for the determination of free lipoic acid and related compounds, such as dihydrolipoic acid, lipoamide and other analogues. Moreover, gas chromatography-mass spectrometry and capillary electrophoresis methods are also developed.