Determination of 3-mercaptopropionic acid by HPLC: A sensitive method for environmental applications

Green-emitting functionalized silicon nanoparticles as an "off-on" fluorescence bio-probe for the sensitive and selective detection of mercury (II) and 3-mercaptopropionic acid

Herein, we developed a class of functionalized silicon nanoparticles (F-SiNPs) bio-probes named thiol-conjugated F-SiNPs. They combine excellent biocompatibility with small dimensions (<10 nm) and biological usefulness with sustained and robust fluorescence (3.32% photoluminescent quantum yield). Identifying 3-Mercaptopropionic acid (3-MPA), which lowers the quantity of gamma-aminobutyric acid in the brain, and mercury (Hg²⁺) was a crucially important step since their excessive levels are a sign of several disorders. Using F-SiNPs as a fluorescent bio-probe, we provided an "off-on" technique for sensitively and selectively determining Hg²⁺ and 3-MPA in this study. The 3-(2-aminoethylamino) propyl (dimethoxymethylsilane) and basic fuchsin as precursors were hydrothermally treated to produce the F-SiNPs exhibiting green fluorescence. Our results suggest that Hg²⁺ reduced the fluorescence of F-SiNPs because of strong ionic interactions and metal-ligand binding among many thiols and carboxyl groupings at the surface of Hg²⁺ and F-SiNPs. Additionally, the resultants demonstrated that after being quenched by Hg²⁺, the produced F-SiNPs led to the distinctive "off-on" response to 3-MPA. Moreover, the method could detect Hg²⁺ and 3-MPA with limits of detection of 0.065 μM and 0.017 μM, respectively. The technique employed is quick, easy, affordable, and environmentally friendly. The sensing platform has successfully determined Hg²⁺ and 3-MPA in urine, water, and human serum samples.

Bacterial community structure in acidic gruel from different regions and its influence on quality

Acidic gruel is a popular and nutritious fermented cereal food in China. However, the relationship between microbial function and quality of traditionally-fermented acidic gruel has not been evaluated. In this study, the microbiome, sensory quality and nutritional components of 98 samples of naturally fermented acidic gruel collected from Guangxi, Shanxi and Inner Mongolia were analyzed by high-throughput sequencing combined with various determination methods. High-throughput sequencing showed bacteria in acidic gruel belonged mainly to the genera Lactobacillus, Acetobacter, Bacillus, Clostridium and Weissella. Bacterial community composition and sensory quality of samples from Shanxi and Inner Mongolia were similar, but significantly different from Guangxi samples (p < 0.05). PICRUSt showed that gene functions were mostly related to carbohydrate and amino acid metabolism; all dominant bacterial genera, except Lactobacillus, were related to taste and volatile flavour indices. Acidic gruel was rich in amino acids, organic acids and soluble solids, which were in significantly higher concentrations in samples from Guangxi than in samples from Shanxi and Inner Mongolia; pH values of samples from Guangxi were also the highest. These differences may be caused by geographical, environmental or manufacturing differences.

Red-emitting GSH-Cu NCs as a triplet induced quenched fluorescent probe for fast detection of thiol pollutants

Thiol compounds exist widely on the Earth and have certain significance in the fields of the circulation of the sulfur element and industrial production. However, the odor and biological toxicity of thiol compounds make them pollutants that seriously threaten the environmental safety and the living quality of human. In this study, a novel triplet induced fluorescence "turn-off" strategy was designed for the detection of thiol pollutants via a glutathione-stabilized copper nanocluster (GSH-Cu NC) probe. The as-prepared GSH-Cu NCs not only have small size and good water-solubility, but also exhibit strong red-emitting fluorescence at 630 nm, which could be quenched quantitatively with the increase of the concentration of thiol pollutants. So they were employed to detect thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA), 2-mercaptoethanol (ME) and 2-(diethylamino)ethanethiol (2-AT) in a wide linear range of 1-100 μM with detection limits of 0.73 μM, 0.43 μM, 0.37 μM, and 0.69 μM, respectively. This method was successfully applied to detect the above thiol pollutants in lake water with good recoveries. Moreover, their further application was also expanded as luminous test strips based on the excellent fluorescence characteristics of GSH-Cu NCs for fast real-time detection of thiol pollutants.

Organic Analysis of Environmental Samples Using Liquid Chromatography with Diode Array and Fluorescence Detectors: An Overview

This overview is focused to provide an useful guide of the families of organic pollutants that can be determined by liquid chromatography operating in reverse phase and ultraviolet/fluorescence detection. Eight families have been classified as the main groups to be considered: carbonyls, carboxyls, aromatics, phenols, phthalates, isocyanates, pesticides and emerging. The references have been selected based on analytical methods used in the environmental field, including both the well-established procedures and those more recently developed.

Chemosensors for biogenic amines and biothiols

There is burgeoning interest among supramolecular chemists to develop novel molecular systems to detect biogenic amines and bio-thiols in aqueous and non-aqueous media due to their potential role in biological processes. Biogenic amines are biologically important targets because of their involvement in the energy metabolism of human biological systems and their requirement is met through food and nutrition. However, the increasing instances of serious health problems due to food toxicity have raised the quality of food nowadays. Biogenic amines have been frequently considered as the markers or primary quality parameters of foods like antioxidant properties, freshness and spoilage. For instance, these amines such as spermine, spermidine, cadavarine, etc. may originate during microbial decarboxylation of amino acids of fermented foods/beverages. These amines may also react with nitrite available in certain meat products and concomitantly produce carcinogenic nitrosamine compounds. On the other hand, it is also well established that biothiols, particularly, thiol amino acids, provide the basic characteristics to food including flavor, color and texture that determine its acceptability. For instance, the reduction of thiol groups produces hydrogen sulfide which reduces flavour as in rotten eggs and spoiled fish, and the presence of hydrogen sulfide in fish is indicative of spoilage. Thus, biogenic amines and bio-thiols have attracted the profound interest of researchers as analytical tools for their quantification. Much scientific and technological information is issued every year, where the establishment of precise interactions of biogenic amines and bio-thiols with other molecules is sought in aqueous and non-aqueous media. This review summarizes the optical chemosensors developed for the selective detection of biogenic amines and bio-thiols.

Biodegradation tests of mercaptocarboxylic acids, their esters, related divalent sulfur compounds and mercaptans

Mercaptocarboxylic acids and their esters, a class of difunctional compounds bearing both a mercapto and a carboxylic acid or ester functional group, are industrial chemicals of potential environmental concern. Biodegradation of such compounds was systematically investigated here, both by literature search and by experiments (Closed Bottle Test OECD 301D and Manometric Respirometry Test OECD 301F). These compounds were found either readily biodegradable or at least biodegradable to a significant extent. Some related compounds of divalent sulfur were tested for comparison (mercaptans, sulfides, disulfides). For the two relevant monofunctional compound classes, carboxylic acids/esters and mercaptans, literature data were compiled, and by comparison with structurally similar compounds without these functional groups, the influence of COOH/COOR' and SH groups on biodegradability was evaluated. Thereby, an existing rule of thumb for biodegradation of carboxylic acids/esters was supported by experimental data, and a rule of thumb could be formulated for mercaptans. Concurrent to biodegradation, abiotic processes were observed in the experiments, rapid oxidative formation of disulfides (dimerisation of monomercaptans and cyclisation of dimercaptans) and hydrolysis of esters. Some problems that compromise the reproducibility of biodegradation test results were discussed.