Carboxyl-bearing low-molecular-weight compounds such as keto acids, fatty acids, and other organic acids are involved in a myriad of metabolic pathways owing to their high polarity and solubility in biological fluids. Various disease areas such as cancer, myeloid leukemia, heart disease, liver disease, and lifestyle diseases (obesity and diabetes) were found to be related to certain metabolic pathways and changes in the concentrations of the compounds involved in those pathways. Therefore, the quantification of such compounds provides useful information pertaining to diagnosis, pathological conditions, and disease mechanisms, spurring the development of numerous analytical methods for this purpose. This review article addresses analytical methods for the quantification of carboxylic acids, which were classified into fatty acids, tricarboxylic acid cycle and glycolysis-related compounds, amino acid metabolites, perfluorinated carboxylic acids, α-keto acids and their metabolites, thiazole-containing carboxylic acids, and miscellaneous, in biological samples from 2000 to date. Methods involving liquid chromatography coupled with ultraviolet, fluorescence, mass spectrometry, and electrochemical detection were summarized.

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2-Hydroxyglutarate (2-HG) was enantiomerically separated using copper(II) acetate and N,N-dimethyl-L-phenylalanine as chiral additives. These compounds formed diastereomeric complexes with 2-HG, which were successfully separated on an achiral (ODS) column. Several parameters, such as additive concentration, the type of organic modifier, and column temperature, were optimized.Using the optimal mobile phase (1 mM copper(II) acetate and 2 mM N,N-dimethyl-L-phenylalanine in a 10% aqueous methanol solution), 2-HG enantiomers were successfully separated in 15 min with a resolution of 1.93.

An analytical method for 2-hydroxyglutarate 2-HG enantiomers was developed using on-line heart-cutting two-dimensional liquid chromatography (2D-LC) with fluorescence detection.