Vol 72, No 14 (2017)

Based on a review of recent domestic and international literature, examples of using secondary ion mass spectrometry (SIMS) for the determination of carbon and hydrogen in solving particular problems of geochemistry and space chemistry are presented. Special attention is paid to problems arising in calibration procedures for the quantitative determination of carbon and hydrogen by SIMS. A summary of equipment currently used for SIMS analysis is given. Mass spectral imaging method based on mathematical processing of the recorded secondary ion currents of carbon and hydrogen for visualizing 3D distributions of elements is considered in detail.

Disinfection is an important step in the purification of drinking and swimming pool water. The most common procedure includes chlorination, which efficiently eliminates microorganisms. However, the reaction of active chlorine with dissolved organic matter produces numerous organochlorine compounds posing a hazard to the environment and human health. UV filters belong to emerging contaminants, as their application to skin protection from UV irradiation becomes increasingly popular all over the world. Certain components of UV filters were detected in swimming pools and result in the emergence of new ecotoxicants. In the present study, 40 compounds, including numerous brominated derivatives, which result from the chlorination of avobenzone in sea water, were identified by gas chromatography–high resolution mass spectrometry. In addition, the applicability of photocatalysis to the destruction of chlorination products was studied. The procedure was found to be rather efficient and allows a decrease in the total amount of avobenzone transformation products by a factor of 10. The only compound class demonstrating stability under the applied conditions is exemplified by halogenated acetophenone derivatives.

Derivatization by composite reagents based on ω-bromoacyl chlorides [ClCO(C₂)_nBr (n = 1–4)] and pyridine was applied to study aliphatic and alicyclic alcohols and diols by ordinary and tandem electrospray ionization (ESI) mass spectrometry. The applied derivatization involves the simultaneous acylation of hydroxyl groups with an acyl chloride moiety and the quaternization of pyridine with a terminal bromoalkyl group. Under the ESI conditions, quaternary salts produce corresponding mono and diammonium cations, which are detected in the first-order mass spectra. Collision-induced dissociation (CID) of primary cations generated from monool derivatives gives rise to ammonium cations of the corresponding acids HOOC(CH₂)_n–N⁺(C₅H₅). The CID of primary dications affords the same cations which are also eliminated from dications to form mono-charged fragments.

A method of high resolution-mass spectrometry with acetone doped atmospheric pressure photoionization was used to study products of the alkaline solvolysis of hydrolysis lignin. It was found that the mass spectrum of the depolymerization products of hydrolysis lignin consists of about seven thousand peaks of oligomers, containing up to 10 aromatic units with an average molecular weight of 150 Da. Calculations of the elemental compositions of all detectable oligomers and their visualization on the van Krevelen coordinates allowed us to show that the studied sample differs from native (virgin released) lignin by the presence of fractions with high oxygen contents and highly unsaturated condensed structures, including polynuclear aromatic hydrocarbons. The structural units of lignin oligomers were characterized using an approach based on the collision induced dissociation of precursor ions in a broad m/z range.

The dependence of matrix-assisted laser desorption/ionization (MALDI) mass spectra of lipids extracted from human blood plasma and corresponding lipid compositions on different experimental conditions was studied. Not only numerous compounds of the lysophosphatidylcholines (LPCs) and phosphatidylcholines (PCs) groups, but also lipid oxidation products, including six oxidized LPCs, are detected. They are present in the original samples and produced by the reaction with air oxygen molecules, resulted in their accumulation in samples under analysis. A higher sensitivity of MALDI detection is observed for less hydrophobic LPCs as compared to more hydrophobic PCs; this phenomenon is explained. The hydrophobicity/ lipophilicity factor is also revealed in replacing the matrix of 2,5-dihydroxybenzoic acid by α-cyano-4- hydroxycinnamic acid. The latter matrix is rarely used in MALDI detection of lipids and may be suitable for the selective determination of LPCs and oxidized LPCs.

The paper describes the results of extraction of aromatic microbial metabolites (phenylcarboxylic acids) from model aqueous solutions using microextraction by packed sorbent (MEPS), followed by the determination of their silyl derivatives by gas chromatography/mass spectrometry. The selected conditions of adsorption–desorption, derivatization, and gas chromatography determination enable the detection of a number of compounds, which are proved and prospective disease markers. This detection could be performed at the level of their concentration in blood of healthy donors (0.5 μmol L^–1) and patients of intensive care units, having an initial stage of sepsis (2–3 μmol L^–1) or other serious diseases caused by significant microbial load and led to the development of multiple organ failure. The recoveries of phenylcarboxylic acids using nonpolar sorbent (C18) reached 20–65% for hydroxylated acids (phenyllactic, 4-hydroxybenzoic, 4-hydroxyphenylacetic, 4-hydroxyphenylpropanoic, homovanillic, and 4-hydroxyphenyllactic acids) and 100% for more nonpolar acids (benzoic, phenylpropanoic, and cinnamic acids).

The dependence of the degree of fragmentation of anthocyanin “molecular” ions on the cone voltage of a mass spectrometric electrospray ionization detector was studied. It was found that the voltage required for the fragmentation of 50% of original “molecular” ions, E_f(0.5), increased with the number of glycoside residues. The fragmentation of glycosides proceeds with the removal of the entire residue regardless of their structures. In the case of 3,5-diglycosides, two types of fragment ions formed due to the loss of glycosidic residues from different positions; the ratio of their peak intensities is reciprocal to the ratio of the masses of residues eliminated. The values of E_f(0.5) for monoglycosides (190 V), diglycosides (229 V), triglycosides (267 V), and for some acylated cyanidin-3,5-diglycosides are determined. These results were given for the gradient separation of anthocyanins by reversed-phase HPLC in aqueous acetonitrile containing 10 vol % of formic acid using quadrupole mass spectrometric detection.