Application of matrix-assisted laser desorption/ionization in the studies of phosphotungstic acid.

RATIONALE: Phosphorotungstic acid (PTA) has many applications, especially in the field of catalysis, due to its structural properties. However, the structure of PTA is studied mainly using theoretical methods. Matrix-assisted laser desorption/ionization (MALDI) has the potential to be an effective method for the experimental study of heteropolyacids. Limitations of MALDI are the high molecular weight of the particles and the complex distribution of isotopic peak intensities. Both problems can be solved by automatically identifying observed signals by generating hypothetical molecular formulas and estimating their isotopic distributions. METHODS: Phosphotungstic acid was studied under conditions of laser desorption/ionization in the absence and in the presence of the matrix. Three types of matrices were used: 2,5-dihydroxybenzoic acid in water, α-cyano-4-hydroxycinnamic acid in acetonitrile, and sinapic acid (SA) in tetrahydrofuran. Part of the peaks in the resulting mass spectra was identified using in-house developed software that implements the automated isotopic distribution brute force. RESULTS: The most informative mass spectra were obtained using SA as the matrix, which enabled the detection of particles containing PTA dimers for the first time. The compositions of particles incorporating PTA dimers were determined in an automated manner and can be written as [H3PW12O40]2·2H2O (m/z = 5791.2 Da) and [H3PW12O40]2·4H2O (m/z = 5836.5 Da). Other observed species included (WO3)n·PO3 -, HPO2·(WO3)n, and WO2·(WO3)n clusters, with the latter containing W in mixed oxidation states. CONCLUSIONS: The combined use of MALDI and an automated identification procedure provided valuable experimental data on the structure and fragmentation of phosphotungstic acid. To the best of our knowledge, this study was the first to report on particles containing phosphotungstic acid dimers.

1-Methyl-1H-1,2,4-triazole as the main marker of 1,1-dimethylhydrazine exposure in plants.

With their wide application in chemical industry, human health and environmental toxic effects of hydrazines arise extensive concerns. Although hydrazine exposure is known to lead to inhibition of seed germination and seedling growth in plants, there are few reports about the mechanism of oxidation or transformation ways of hydrazines in plant tissue. In this research, garden cress (Lepidium sativum L.) and zucchini (Cucurbita pepo L.) were used as model plant objects to study 1,1-dimethylhydrazine exposure in vitro using the GC-MS system. The seed germination and plant growth experiments were carried out in Petri dishes using an aqueous media. Among the detected 1,1-dimethylhydrazine transformation products in plant tissues, 1-methyl-1H-1,2,4-triazole had the highest intensity and reproducibility. In our research, 1-methyl-1H-1,2,4-triazole formed at all contaminant concentrations in an extremely short period. This preliminary study determined 1,1-dimethylhydrazine environment contamination by detecting 1-methyl-1H-1,2,4-triazole in combination with other transformation products.

The mysterious mass death of marine organisms on the Kamchatka Peninsula: A consequence of a technogenic impact on the environment or a natural phenomenon?

The increased incidence of environmental disasters in recent years is a matter of serious concern. The reasons for the disaster on the Kamchatka Peninsula (Russia), which occurred in September 2020 and caused the mass death of marine organisms, have not yet been established. This is the first study of the environmental disaster on Kamchatka and should shed light on the possible impact of two main man-made factors associated with an oil spill and a rocket fuel spill. The traces of oil products found in marine organisms could not have led to their death, as they indicate old oil pollution, heavy metals concentrations did not exceed the average values for the studied objects. The propellant and its transformation products were not found in the samples. Thus, having excluding the two main technogenic factors of the death of marine organisms, we can conclude that it was probably caused by a natural phenomenon.

Microextraction by packed sorbent optimized by statistical design of experiment as an approach to increase the sensitivity and selectivity of HPLC-UV determination of parabens in cosmetics.

A new approach to the quantitative analysis of parabens (PBs) in cosmetics, based on microextraction by packed sorbent (MEPS) followed by HPLC-UV detection is proposed. The development of optimal conditions for the sample preparation step was carried out in two stages. The potentially important factors that could influence the extraction were screened using the Plackett-Burman design approach, as a result of which, three statistically significant factors were selected from the nine studied. Thereafter, the selected variables were optimized by response surface methodology using a Central Composite Design. Under optimal conditions, the linear ranges for PBs analysis in cosmetic samples were 0.05-4 µg/mL with excellent precision. Limits of detection (LOD) of PBs in cosmetic samples were 2-5 ng/mL, and the extraction recovery ranged from 89 to 105 %. By comparing the chromatograms of the diluted shampoo sample before and after MEPS, the benefits of developed approach were shown. Then it was applied to the analysis of PBs in commercial hair cosmetic products: parabens were determined in all samples in which they were indicated on the package and in 1 of 12 samples labeled "paraben-free". Finally, the proposed method was compared with other analytical HPLC-UV methods with various sample pretreatment techniques for PBs analysis in cosmetics described in recent articles. Its sensitivity turned out to be one of the highest, while it is express, automated, meets the principles of green chemistry.