Konstantin Chingin

Perfluoroalkanes (PFAs), a subclass of per- and polyfluoroalkyl substances (PFASs), are persistent environmental contaminants of growing global concern. The combination of high carbon-fluorine (C-F) bond stability and the absence of ionizable groups makes the direct detection of PFAs highly challenging, typically requiring complex sample preparation. Herein, we report a novel online ambient mass spectrometry (MS) approach for the rapid and sensitive analysis of PFAs without any sample pretreatment. This approach utilizes a corona discharge source to generate reactive water radical anions/cations (H₂O^-•/H₂O^+•) in situ, which efficiently activate the inert C-F bond via a hydroxylation pathway, converting PFAs into readily detectable hydroxylated derivatives. The approach was demonstrated for perfluorooctane, perfluorohexane, and perfluoroheptane, achieving direct, real-time analysis, with limits of detection (LODs) ranging from 0.28 to 0.30 ng/L. The reaction mechanism and products were characterized using high-resolution MS, tandem MS, isotope labeling, and theoretical calculations. This H₂O^-•/H₂O^+•-induced strategy provides an efficient and powerful tool for the sensitive screening of PFAs in environmental samples.

The practical application of advanced oxidation processes is often constrained by their high energy consumption and dependence on chemical additives. To overcome these limitations, this work harnesses the highly reactive species water dimer radical cation (H₂O)₂^+•, as a green oxidant for efficient dye degradation. A corona discharge setup was developed for the controlled, ambient generation of (H₂O)₂^+•, which was directly detected by in situ mass spectrometry. Electron paramagnetic resonance spectroscopy further verified its role as a precursor to hydroxyl radicals, elucidating the underlying radical cascade. Using model dyes (e.g., rhodamine B) as representative pollutants, degradation was quantitatively tracked via their characteristic UV-vis absorption. The (H₂O)₂^+•-based process achieved 99% removal of rhodamine B in 8 min without any external chemical inputs, representing a more than 1100-fold enhancement in processing rate over conventional Fenton oxidation. Scalability was demonstrated through an enlarged array device, which exhibited an energy consumption of 0.75 kJ/mg and a degradation efficiency ∼90 times higher than that of a standard Fenton system. This study establishes a practical route to utilize (H₂O)₂^+• for rapid, chemical-free water treatment, offering a scalable and energy-efficient strategy for green degradation technologies.

The rapid, sensitive, selective, and real-time measurement of n-alkanes in mixtures is significant for safety, health, and the environment. However, detecting n-alkanes is challenging due to their optoelectronic and chemical inertness, particularly in ambient mass spectrometry (MS) measurements, which often necessitate hardware modifications or environmentally harmful derivatization reagents. Here, an ambient MS approach was proposed for direct n-alkane detection in complex mixtures, leveraging water dimer radical cations ((H₂O)₂^+•) generated by a low-energy ambient corona discharge to activate C-H bonds and form detectable dihydroxyalkane adducts (R-C⁺(OH)₂). Using hexane as a model, the mechanism involves the following: (a) (H₂O)₂^+• reacts with hexane to produce a stable complex, followed by (b) stepwise hydroxylation reaction forming R-C⁺(OH)₂. The method was successfully extended to other n-alkanes (e.g., pentane, heptane, octane, nonane, and decane) with their corresponding dihydroxyalkane adducts R-C⁺(OH)₂ detected as anticipated. The presented MS approach enables simple and real-time analysis of n-alkanes in complex matrices, with a detection limit down to 0.22 parts per trillion. By leveraging (H₂O)₂^+•-induced C-H activation, this work provides an environmentally friendly strategy for direct n-alkane determination in mixtures under ambient conditions without sample pretreatment, offering a novel pathway for direct n-alkane determination across various fields including environmental monitoring, petroleum analysis, etc.

Water radical cations (H₂O^+•) serve as key reactive intermediates in fundamental chemical processes, atmospheric chemistry, and energy-related applications due to their high reactivity and ability to initiate diverse chemical reactions. In this study, we investigated the generation of water dimer radical cations (m/z 36, (H₂O)₂^+•) and their reaction products with different substrates using multiple soft ionization techniques. Our comprehensive analytical platform incorporates corona discharge ionization (CDI), electrospray ionization (ESI), dielectric barrier discharge ionization (DBDI), and microwave plasma torch (MPT), coupled with complementary mass analyzers, including ion trap, Orbitrap, and quadrupole time-of-flight (Q-TOF) mass spectrometers. To confirm the formation of (H₂O)₂^+•, we employed a multitechnique verification strategy combining high-resolution mass spectrometry (MS), isotope labeling technique, tandem MS, and electron paramagnetic resonance (EPR) spectroscopy. The stabilization and reactivity of H₂O^+• were also examined by using different substrates.

Chemical fingerprinting to characterize the occurrence state and abundance of organic and inorganic constituents within fine particulate matter (PM2.5) is useful in evaluating the associated health risks and tracing pollution sources. Herein, an analytical strategy for the rapid analysis of metal and organic constituents in PM2.5 was developed employing a combination of sequential chemical extraction coupled with mass spectrometry detection. H₂O, CH₃OH, EDTA-2Na, electrochemical oxidation, and electrochemical reduction were sequentially utilized to extract the chemical constituents in PM2.5 samples on a homemade device employing simultaneous online detection using two linear trap quadrupole mass spectrometers (LTQ-MS) with electrospray ionization (ESI) in positive and negative modes. After a single analytical procedure, dozens of metals (e.g., Pb, Cr, and Cu), organic compounds (e.g., amines, polycyclic aromatic hydrocarbons, and aliphatic acids), and negative ions (e.g., NO₃^-, NO₂^-, and Cl^-) were comprehensively detected in the water-soluble, liposoluble, insoluble, oxidizable, and reducible fractions of PM2.5 samples, and their physical and chemical relationships were established.

Hydroxyl quaternization through the direct oxidation reaction of aromatic amines, facilitated by water radical cations within water microdroplets, is explored.

The positions of C═C bonds in unsaturated fatty acids (FAs) are one of the main factors determining the quality of food flavor. Herein, we developed an approach for the determination of C═C bonds of FAs by online epoxidation reaction with water dimer radical cations. The limit of detection for octenoic acid isomers was ∼9 μg/L. The positions of C═C bonds in trans-2/3-hexenoic acid, trans-2/3-octenoic acid, oleic acid, linoleic acid, and linolenic acid in black tea or olive oil samples were directly determined by the established method. These results indicate that the established method allows the rapid determination of unsaturated FAs in black tea and olive oil. The advantages of this approach include the analysis speed (∼1 min per sample), simple device, and no need for complex pretreatment. This study not only provides a strategy for the determination of C═C positions but also offers new possibilities for applications in the field of food chemistry.

The information regarding the occurrence and abundance of lead (Pb) in PM2.5 is useful for the evaluation of air pollution status and tracing the pollution source. Herein, electrochemical mass spectrometry (EC-MS) for sequential determination of Pb species in PM2.5 samples without sample pretreatment has been developed using the combination of online sequential extraction with mass spectrometry (MS) detection. Four kinds of Pb species including water-soluble Pb compounds, fat-soluble Pb compounds, water/fat-insoluble Pb compounds, and a water/fat-insoluble Pb element were sequentially extracted from PM2.5 samples, in which water-soluble Pb compounds, fat-soluble Pb compounds, and water/fat-insoluble Pb compounds were extracted sequentially by elution using H₂O, CH₃OH, and EDTA-2Na as the eluent respectively, while the water/fat-insoluble Pb element was extracted by electrolysis using EDTA-2Na as the electrolyte. The extracted water-soluble Pb compounds, water/fat-insoluble Pb compounds, and water/fat-insoluble Pb element were transformed into EDTA-Pb in real time for online electrospray ionization mass spectrometry analysis, while the extracted fat-soluble Pb compounds were directly detected by electrospray ionization mass spectrometry. The advantages of the reported method include the obviation of sample pretreatment, high speed of analysis (90%), which indicates the potential of this method for the rapid quantitative species detection of metals in environmental particulate matter samples.

The molecular profile of a tumor is associated with its histological type and can be used both to study the mechanisms of tumor progression and to diagnose it. In this work, changes in the lipid profile of a malignant breast tumor and the adjacent tissue were studied. The potential possibility of determining the histological type of the tumor by its lipid profile was evaluated. Lipid profiling was performed by reverse-phase chromato-mass-spectrometric analysis the tissue of lipid extract with identification of lipids by characteristic fragments. Potential lipid markers of the histological type of tumor were determined using the Kruskal-Wallis test. Impact of lipid markers was calculated by MetaboAnalyst. Classification models were built by support vector machines with linear kernel and 1-vs-1 architecture. Models were validated by leave-one out cross-validation. Accuracy of models based on microenvironment tissue, were 99% and 75%, accuracy of models, based on tumor tissue, were 90% and 40% for the positive ion mode and negative ion mode respectively. The lipid profile of marginal (adjacent) tissue can be used for identification histological types of breast cancer. Glycerophospholipid metabolism pathway changes were statistically significant in the adjacent tissue and tumor tissue.

Research of cancer progression mechanisms and their impact on metabolism of tumor cells and tumor microenvironment cells is an important element in drug development for cancer target therapy. In this study, changes in tumor tissue and margin tissue lipid profiles were investigated for their association with the following clinical and morphological characteristics: tumor size, cancer stage, multifocality, tumor grade, number of lymph node metastases, Nottingham prognostic index, total malignancy score, and the level of Ki67 protein. Lipid profiling was performed by reverse-phase chromato-mass spectrometry analysis of the lipid tissue extract with lipid identification by characteristic fragments. In the lipid profile of tumor tissue 13 characteristic lipids were selected. Their levels significantly correlated with at least 5 clinical and morphological features. Eight of 13 lipid features belonged to phosphatidylcholines. In the lipid profile of tumor microenvironment tissue, 13 lipid features were selected. Their levels significantly correlated with at least 5 clinical and morphological features. Four of 13 lipid features belonged to oxidized lipids, 4 lipid features belonged to sphingomyelins, 4 lipid features belonged to phosphatidylethanolamines. The tumor microenvironment tissue lipid profile correlated with the tumor size, the cancer stage, the tumor grade, the number of axillary metastases, and the Nottingham prognostic index. The tumor tissue lipid profile correlated with tumor size, tumor grade, total malignant score, and number of axillary metastases.