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Project titleDevelopment of new hyphenated techniques for chemical food analysis

AffiliationFederal State Budgetary Educational Institution of Higher Education "Saint-Petersburg State University",

Research area 03 - CHEMISTRY AND MATERIAL SCIENCES, 03-205 - Analytical chemistry

KeywordsAnalytical chemistry, sample preparation, separation and concentration techniques, microextraction, magnetic nanoparticles, chromatographic methods, food, ecotoxicants

Annotation
Due to constantly increasing necessity for food control, there is a need for reliable safe and effective analytical methods for the determination of target analytes at concentrations of maximum residue level and below. To determine the "contaminants" in food products modern instrumental methods of analysis such as chromatographic (HPLC-UV, HPLC-FLD, HPLC-MS, GC-MS, etc.), spectral (ICP, AAS, etc.), electrochemical, etc. are widely used in chemical analysis. Taking into account the complexity of food matrices, preliminary stage of sample preparation is an important and integral step of chemical analysis. Various methods of separation and preconcentration help to eliminate the interfering effects of related components and to concentrate target analytes, increasing selectivity and sensitivity of the method in general. Thus, one of the current general strategies in modern analytical chemistry is the hybridization (combination) of chemical analysis methods by combination of separation techniques with determination methods. The goal of the Project is a creation of complex of new simple, express and sensitive methods to ensure reliable food quality control. As a result of the Project, a new approach of headspace solid-phase microextraction of volatile analytes from solid food samples will be developed. Its main feature is the use of a new environmentally friendly sorbent – magnetic nanoparticles, which has several advantages compared to previously known sorbents. The current trend of "green analytical chemistry" is the use of environmentally friendly solvents during extraction process [J. Płotka-Wasylka et al., TrAC, 91 (2017) 12-25]. Taking into account this fact, a new approach of cloud point microextraction based on isolation of analytes from complex samples in extraction solvent phase formed by a micellar phase of surfactant (higher carboxylic acid and amine) will be developed. The combination of the developed microextraction techniques with instrumental methods will allow to solve such analytical task as the determination of ecotoxicants (in this Project: pesticides and aromatic hydrocarbons) in products of agriculture and food industry. The groundwork of the Head of the Project in this direction will promote implementation of this work.

Expected results
One of the current trends in modern analytical chemistry is the search for new environmentally friendly materials and solvents for the realization of extraction processes and their introduction into analytical practice. According to a review by J. Płotka-Wasylka etc. «Extraction with environmentally friendly solvents» [TrAC, 91 (2017) 12-25], such solvents as: ionic liquids (IL), deep eutectic solvents (DES), bio-derived solvents, supercritical fluids, surface active agents (surfactants), and also switchable hydrophilicity solvents (SHS) based on medium-chain fatty acids [H.K. Shih et al., Anal. Chim. Acta, 854 (2015) 70] and tertiary amines [J.R. Vanderveen et al., Green Chem. 16 (2014) 1187] can be considered as environmentally friendly solvents. Despite of the environmental friendliness and a number of other advantages presented by the extractants, all of them have drawbacks such as high cost (IL, supercritical fluids); complex preparation procedure and non-biodegradability (IL); application limits (DES, SHS); need for deeper study (bio-derived solvents), and the restriction in direct injection into the chromatographic system due to the high viscosity (IL, surfactant, SHS). Thus, the question of the study and search for new safe solvents remains open to this day. The proposed Project will demonstrate the possibility in using a mixture of medium-chain fatty acid and amine as a zwitterionic (mixed) surfactant for the implementation of cloud point microextraction from solid phase samples. Combination of the developed microextraction method with the GC-MS system (due to reduced viscosity and soapy of the mixed surfactant) will allow to develop a simple, environmentally friendly and sensitive method for the determination of pesticides (fungicides, insecticides and herbicides) in plant products. Compared with the existing analogues, where toxic organic solvents are mainly used, the proposed approach will provide highly safe analysis, moreover, it will characterized by high throughput competing with methods with long sample preparation stage. The search for new sorbents for the implementation of solid-phase microextraction led to the study of properties of magnetic nanoparticles, which have found wide application for sample preparation of water matrices, including food products [J. González-Sálamo et al., TrAC 85 (2016) 203-220; B. Hashemi et al., Talanta, 187 (2018) 337-347]. The large surface area and small amount of sorbent allow to carry out highly effective preconcentration, and the presence of magnetic properties eliminates the need for a centrifugation step. A new approach of headspace solid-phase microextraction based on using environmentally friendly modern materials – magnetic nanoparticles as a sorbent will be proposed in this Project for the determination of volatile phenols in solid-phase food samples for the first time. Such approach will allow to achieve a high selectivity in analytes’ isolation and to eliminate the interferences of matrix components. The capabilities of this approach will be demonstrated in a combined scheme including the sorption of volatile phenols from smoked food products on magnetic nanoparticles, its chromatographic separation and fluorimetric detection. It is expected, that the new hybrid (hyphenated) method will provide lower detection limits, cost-effectiveness and rapidity of analysis compared to existing analogues. According to modern trends in analytical chemistry to miniaturization and automation of chemical analysis in order to reduce reagent consumption and waste generation, as well as reduce labor costs and eliminate the “human factor”, microextraction techniques and the possibility of their automation on the principles of flow analysis are being actively developed. Taking into account these trends, a universal combined method for the determination of polyaromatic hydrocarbons in solid-phase matrices of food samples, including their microextraction and preconcentration followed by chromatographic separation and fluorimetric detection will be developed in this Project. The original works presented in the Project are focused on the requirements of modern “green analytical chemistry” [J.A. Lima Pallone et al. “Green analytical chemistry applied in food analysis: alternative techniques” // Current Opinion in Food Science, 22 (2018) 115-121] and are intended for express, highly sensitive and environmentally safe food quality control in expert laboratories.

Annotation of the results obtained in 2020
During the implementation of the Project, a work plan was fulfilled: a new combined scheme for the determination of polycyclic aromatic hydrocarbons (PAHs) in tea, including an automated stage of sample preparation and subsequent determination of target analytes by high performance liquid chromatography with fluorometric detection (HPLC-FL), was developed. For this a simple, express and environmentally friendly scheme of dispersive liquid-liquid microextraction (DLLME) has been developed. It involves the introduction of an emulsion based on a switchable hydrophilicity solvent (carboxylic acid) into an aqueous sample solution, as a result of which the salt of the carboxylic acid acts as a surfactant-dispersive solvent and a micellar phase enriched with analytes is released onto the surface of the system. To implement the proposed scheme, studies were carried out to optimize and select the following parameters: the choice of carboxylic acid (hexanoic acid); the ratio and concentration of the components of the emulsion (hexanoic acid and 1M NaOH in a ratio of 1: 4, respectively); sample and emulsion volumes (3.8 mL and 1.2 mL, respectively); pH (7.0), and extraction time (10 s stirring and 3 min of phase separation). Based on literature data, 13 PAHs (benzo [a] pyrene, chrysene, benzo [a] anthracene, benzo [b] fluoranthene, benzo [k] fluoranthene, fluorene, dibenz [a, h] anthracene, benzo [ghi] perylene, naphthalene, anthracene, fluoranthene, phenanthrene and pyrene) most frequently found in food products were selected. The HPLC-FL conditions for their determination were chosen. The composition of the micellar phase was studied and established: sodium hexanoate, water and hexanoic acid in a molar ratio of 1:6:6, respectively. Cryo-SEM images were obtained, confirming the presence of supramolecular structures. A feature of the developed scheme was revealed: the low viscosity of the micellar phase (the measured value of the kinematic viscosity was 8.8 ± 0.3 mm2/s at 20 °C), which became a key point in the combination of the developed microextraction method with the HPLC-FL system. Automation of the proposed scheme based on the principles of flow analysis (in-a-syringe system) made it possible to significantly reduce the sample preparation time (sample throughput – 15 samples/hour), increase the reproducibility of results (RSD up to 4.1 %) and reduce labor costs. The developed automated procedure was applied for the determination of 13 PAHs in 4 samples of tea infusion, the correctness of the results obtained was confirmed by the "add-found" method. The obtained scientific data are published in the journal Talanta (IF 5.339, Q1): Irina Timofeeva, Kira Stepanova, Andrey Bulatov. In-a-syringe surfactant-assisted dispersive liquid-liquid microextraction of polycyclic aromatic hydrocarbons in supramolecular solvent from tea infusion. // Talanta 224 (2021) 121888. DOI: 10.1016/j.talanta.2020.121888. Internet link https://www.sciencedirect.com/science/article/abs/pii/S0039914020311796?via%3Dihub

Publications

1. Irina Timofeeva, Kira Stepanova, Andrey Bulatov In-a-syringe surfactant-assisted dispersive liquid-liquid microextraction of polycyclic aromatic hydrocarbons in supramolecular solvent from tea infusion Talanta, 224 (2021)121888 (year - 2021) https://doi.org/10.1016/j.talanta.2020.121888

Annotation of the results obtained in 2019
During the implementation of the Project, a new variant of micelle-mediated microextraction based on mixed surfactants was proposed and practically implemented. It represents by extraction of analytes in the micellar phase formed by primary amine and medium-chain fatty acid. Phase separation was achieved by adding a salting out agent. The developed scheme involves injection of the extraction mixture (1-nonylamine, pivalic acid and deionized water in ratios of 3:2:5, v/v/v) into an aqueous solution with a homogenized sample resulted in extraction of analytes from solid-phase sample into the obtained micellar solution; then, after changing the ionic strength by addition of sodium chloride, micelle aggregation and phase separation occurs. The surfactant-rich phase obtained after centrifugation was found to be compatible with highly sensitive detection systems (e.g. GC-MS) without any dilution due to low viscosity of the phase. Thus, a combined scheme for the determination of pesticides in plant food samples, including the micelle-mediated microextraction with subsequent detection of target analytes by GC-MS, was developed; and the conditions for its implementation were optimized. The surfactant-rich phase was investigated in detail to reveal the mechanism of the proposed microextraction procedure. The analytical capabilities of the scheme developed were demonstrated on the determination of diazinon, triadimefon, triadimenol and bifentrin in cucumbers and baby food. The results were confirmed by the reference method. [D. Kanashina, A. Pochivalov, I. Timofeeva, A. Bulatov. Mixed surfactant systems based on primary amine and medium-chain fatty acid: Micelle-mediated microextraction of pesticides followed by the GC–MS determination. Journal of Molecular Liquids, 306 (2020) 112906. DOI: 10.1016/j.molliq.2020.112906. (IF=4,561)]. Also, a new method of sample preparation, the magnetic headspace adsorptive microextraction, was proposed and practically implemented during this Project. The possibility of using magnetic nanoparticles as a sorbent for the headspace sorption of volatile phenols was considered for the first time; the choice of Fe3O4@Cr(OH)3-based nanoparticles as the magnetic sorbent and 0.01 M of sodium hydroxide solution as the eluent was justified. As a result, a combined scheme for the determination of volatile phenols in smoked products, including the magnetic headspace adsorptive microextraction and subsequent determination of anatites by HPLC-FL, was developed. The scheme involved the thermal isolation of phenols from the sample, their sorption on magnetic nanoparticles held on the inner side of the cap by an external magnet, followed by desorption of the analytes into a weakly alkaline solution; then the nanoparticles were kept at the bottom of the vessel due to the magnetic properties, and the obtained supernatant with analytes was analyzed by HPLC-FL. The possibilities of the developed scheme were demonstrated on the determination of volatile phenols (phenol, guaiacol, p-cresol and o-cresol) in three types of smoked sausage. [Irina Timofeeva, Mariya Alikina, Mikhail Osmolowsky, Olga Osmolovskaya, Andrey Bulatov. Magnetic headspace adsorptive microextraction using Fe3O4@Cr(OH)3 nanoparticles for effective determination of volatile phenols. // New Journal of Chemistry, 2020. DOI: 10.1039/D0NJ00854K. (IF=3,069)].

Publications

1. D. Kanashina, A. Pochivalov, I. Timofeeva, A. Bulatov Mixed surfactant systems based on primary amine and medium-chain fatty acid: Micelle-mediated microextraction of pesticides followed by the GC–MS determination Journal of Molecular Liquids, 306 (2020) 112906 (year - 2020) https://doi.org/10.1016/j.molliq.2020.112906

2. Irina Timofeeva, Mariya Alikina, Mikhail Osmolowsky, Olga Osmolovskaya, Andrey Bulatov Magnetic headspace adsorptive microextraction using Fe3O4@Cr(OH)3 nanoparticles for effective determination of volatile phenols New Journal of Chemistry, - (year - 2020) https://doi.org/10.1039/D0NJ00854K