Derivatization of carboxylic groups prior to their LC analysis - A review

Carboxylic acids (CAs) represent a large group of important molecules participating in various biologically significant processes. Analytical study of these compounds is typically performed by liquid chromatography (LC) combined with various types of detection. However, their analysis is often accompanied by a wide variety of problems depending on used separation system or detection method. The dominant ones are: i) poor chromatographic behavior of the CAs in reversed-phase LC; ii) absence of a chromophore (or fluorophore); iii) weak ionization in mass spectrometry (MS). To overcome these problems, targeted chemical modification, and derivatization, come into play. Therefore, derivatization still plays an important and, in many cases, irreplaceable role in sample preparation, and new derivatization methods of CAs are constantly being developed. The most commonly used type of reaction for CAs derivatization is amidation. In recent years, an increased interest in the isotopic labeling derivatization method has been observed. In this review, we comprehensively summarize the possibilities and actual trends in the derivatization of CAs that have been published over the past decade.

Recent Analytical Methodologies in Lipid Analysis

Lipids represent a large group of biomolecules that are responsible for various functions in organisms. Diseases such as diabetes, chronic inflammation, neurological disorders, or neurodegenerative and cardiovascular diseases can be caused by lipid imbalance. Due to the different stereochemical properties and composition of fatty acyl groups of molecules in most lipid classes, quantification of lipids and development of lipidomic analytical techniques are problematic. Identification of different lipid species from complex matrices is difficult, and therefore individual analytical steps, which include extraction, separation, and detection of lipids, must be chosen properly. This review critically documents recent strategies for lipid analysis from sample pretreatment to instrumental analysis and data interpretation published in the last five years (2019 to 2023). The advantages and disadvantages of various extraction methods are covered. The instrumental analysis step comprises methods for lipid identification and quantification. Mass spectrometry (MS) is the most used technique in lipid analysis, which can be performed by direct infusion MS approach or in combination with suitable separation techniques such as liquid chromatography or gas chromatography. Special attention is also given to the correct evaluation and interpretation of the data obtained from the lipid analyses. Only accurate, precise, robust and reliable analytical strategies are able to bring complex and useful lipidomic information, which may contribute to clarification of some diseases at the molecular level, and may be used as putative biomarkers and/or therapeutic targets.

A sensitive, precise and rapid LC-MS/MS method for determination of ergosterol peroxide in Paecilomyces cicadae mycelium

Ergosterol peroxide (EP) has considerable potential effect against the proliferation of tumor cells. Here, we established a new approach for EP content detection through liquid chromatography-tandem mass spectrometry. The specificity, limit of detection (LOD)/quantitative (LOQ), linearity and range, accuracy, repeatability, and intermediate precision were tested. The EP retention time was 7.18 min. The linear relationship between the mass concentration of nonylphenol and the chromatographic peak area was good within the EP concentration range of 0.1-2.0 μg/mL. The correlation coefficient was 0.994, the regression equation was Y = 27 409.8 × X - 1114.67, the average recovery rate was 82.77%, the relative standard deviation was 11.1%, the LOQ was 50 ng/mL, and the LOD was 20 ng/mL. The detection technique was convenient, accurate, reproducible, and rapid. Therefore, this method could be used for deep liquid fermentation, providing a basis for EP to serve as a quality standard for the fermentation of Paecilomyces cicadae.