This paper describes the development and validation of an HPLC method for the determination of protein bound and total lipoic acid in human plasma. The essential steps in the total lipoic acid assay include reduction of disulfide bridge with tris(2-carboxyethyl)phosphine, derivatization via thiol group with 1-benzyl-2-chloropyridinium bromide and HPLC analysis of S-pyridinium derivative. Protein-bound lipoic acid is first separated from free lipoic acid with the use of liquid extraction, converted to its reduced counterpart then processed as total lipoic acid. The method is reproducible, precise and accurate. The inter- and intraday related standard deviation varied from 1.5% to 11.5% and from 1.8% to 19.6%, respectively, while recovery is in the range of 80.0–106.0% and 80.4–110.8%, respectively. The mean concentration of total lipoic acid in healthy donors after supplementation with 600mg and 1200mg was 0.67±0.40μmolL−1 (137.6±82.1μgL−1) and 1.57±0.34μmolL−1 (323.34±70.07μgL−1), respectively

α-Lipoic acid (LA) is a unique antioxidant that is not only effective in affording protection against oxidative stress but also plays an essential role in metabolic processes of all living organisms. Therefore, the determination of LA and its metabolites content is crucial for understanding their physiological and pathophysiological functions. Most of the recently developed methods for the detection and determination of LA and its metabolites in various biological samples have focused on sample preparation procedures involving but not limited to sampling, extraction and storage. The main goal of this review is to summarize and critically evaluate the current state of the art of analytical procedures applied to the determination of LA and related compounds in biological samples.

In recent years, the amount of produced petrochemical plastic waste has been growing at an alarming rate. According to the Plastics Europe Market Research Group (PEMRG)/Conversio Market & Strategy GmbH, in 2018 the global production of plastics amounts to 359 million tons, and in Europe—61.8 million tons. More than 80% of all marine litter is plastic, which accumulates in the environment due to its durability. Due to the growing problem, biodegradable polymer products are introduced to the market. Therefore, it is necessary to conduct research on degradation products in order to estimate the risk arising from their presence in the environment. This paper discusses research on compounds that may potentially remain in the soil after the degradation of the double green PLA polymer. The aim of the research was to prove whether products made of PLA, e.g., packaging, films and other waste can release substances harmful to the environment. Therefore, soil was selected as a medium to characterize the substances potentially released from the polymer under conditions simulating the degradation process in the environment. The soil was always used from the same producer. Before the polymer biodegradation process, it was additionally checked for pH, C and N content, number of microorganisms, etc. PLA degradation in soil was carried out in a laboratory accredited by the Polish Accreditation Center (PCA). During the research, soil samples at various stages of the degradation process under laboratory conditions were subjected to both extraction in an aqueous environment and organic solvent extraction The studies used the gas chromatography coupled with mass spectrometry (GC/MS), as well as pyrolysis gas chromatography (Py-GC/MS). In addition, the study used the gel permeation chromatography (GPC/SEC) allowing to determine the distribution of molar masses, average molar masses and polydispersity, and the infrared spectroscopy (FTIR).