Selective extraction and determination of steroidal glycoalkaloids in potato tissues by electromembrane extraction combined with LC-MS/MS

A comprehensive approach to the monitoring of steroidal glycoalkaloids in foods of plant origin

Steroidal glycoalkaloids (GAs) are toxins produced by solanaceous plants. As there are no fully standardized methods for their extraction and determination in food, the research aimed to: (1) develop and critically compare methods based on gas (GC) and liquid (LC) chromatography, including their coupling with mass spectrometry, and (2) to develop and optimize a universal GA extraction method. Hyphenated techniques proved to be the most useful in GA analysis: LC-MS was the most sensitive one, while GC-MS offered the highest chromatographic resolution. It was proven that quantitative results obtained using different analytical techniques cannot be directly compared. New extraction method that is more efficient than the AOAC method (997.13) was then designed and optimized. It was characterized by higher absolute recovery (99% and 34%, respectively) and allowed to extract much more GAs from the same material (e.g. 21.2 ± 1.4 and 11.82 ± 0.97 mg g-1 of potato tubers, respectively).

Chemical nature evolution of solid supports used in electromembrane extraction procedures: A comparative analysis based on metric tools

BACKGROUND

In recent decades, green chemistry has been focusing on the adaptation of different chemical methods towards environmental friendliness. Sample preparation procedures, which constitute a fundamental step in analytical methodology, have also been modified and implemented in this direction. In particular, electromembrane extraction (EME) procedures, which have traditionally used plastic supports, have been optimized towards greener approaches through the emergence of alternative materials. In this regard, biopolymer-based membranes (such as agarose or chitosan) have become versatile and very promising substitutes to perform these processes.

RESULTS

Different green metric tools (Analytical Eco-Scale, ComplexGAPI and AGREEprep have been applied to study the evolution of solid supports used in EME from nanostructured tissues and polymer inclusion membranes to agar films and chitosan flat membranes. The main goal is to evaluate the usage of these new biomaterials in the analytical procedure to quantify their environmental impact in the frame of Green Analytical Chemistry (GAC). In addition, both RGB model and BAGI metrics have been employed to study the sustainability of the whole procedure, including not only greenness, but also analytical performance and feasibility aspects. Results obtained after the performance of the mentioned metrics have demonstrated that the most efficient and environmentally friendly analytical methods are based on the use of chitosan supports. This improvement is mainly due to the chemical nature of this biopolymer as well as to the removal of organic solvents.

SIGNIFICANCE

This work highlights the advantages of biodegradable materials employment in EME procedures to achieve green analytical methodologies. These materials also contribute to raise the figure of merits regarding to the quantification parameters in a wide range of applications compared to classical supports employed in EME, thus enhancing sustainability of procedures.

Parallel electromembrane extraction of peptides with monoterpene and medium-length fatty acid deep eutectic solvents

BACKGROUND

Electromembrane extraction (EME) involves the process of mass transfer of charged analytes from an aqueous sample through an organic liquid membrane into an aqueous acceptor medium under the influence of an electrical field. Successful solvation of the analyte within the liquid membrane is of paramount importance and involves molecular interactions with the liquid membrane. In this comprehensive investigation, parallel EME was examined using a training set of 13 model peptides employing deep eutectic solvents as the liquid membrane. These deep eutectic solvents were formulated by mixing specific monoterpenes (thymol, menthol, camphor) with medium-chain fatty acids (1-octanoic acid and 1-decanoic acid).

RESULTS

From an array of different liquid membrane compositions explored, it was revealed that the combination of camphor and 1-decanoic acid (in a 1:1 w/w ratio) with 2% di (2-ethylhexyl) phosphate (DEHP) delivered the most efficient extraction system. The solvation of the model peptides within this liquid membrane predominantly relied on ionic interactions between protonated basic functionalities and DEHP, along with hydrogen bond interactions between the deprotonated acid functionalities (hydrogen bond acceptor) and 1-decanoic acid (hydrogen bond donor). Selectivity was modulated by the pH of the sample and acceptor solutions, with a direct correlation to the polarity and net charge of the model peptides. The ionization of 1-decanoic acid in the interfacial region between the sample and liquid membrane emerged as an important factor influencing the selectivity.

SIGNIFICANCE AND NOVELTY

Although parallel EME of peptides has been reported previously, the current liquid membrane provides an extraction system with sufficient stability for the first time. Selective extraction of peptides through EME holds substantial promise within the realm of next-generation environmentally-friendly sample preparation methodologies. The findings presented in this paper contribute significantly to our fundamental understanding of these processes, and may serve as an important reference for the development of future methods in this field.

Extraction performance of electromembrane extraction and liquid-phase microextraction in prototype equipment

In this comparative study, the performance of liquid-phase microextraction and electromembrane extraction in prototype equipment was evaluated for extraction of ninety basic substances from plasma. Using a commercial EME device based on conductive vials enabled a standardized and comprehensive comparison between the two methods. Extractions were performed from a pH-adjusted donor solution, across an organic liquid membrane immobilized in a porous polypropylene membrane, and into an acidic acceptor solution. In LPME, dodecyl acetate was used as the extraction solvent, while 2-nitrophenyl octyl ether was used for EME with an electric field applied across the system. To assess the extraction performance, extraction recovery plots and extraction time curves were constructed and analyzed. These plots provided insights into the efficiency and effectiveness of LPME and EME, allowing users to make better decisions about the most suitable method for a specific bioanalytical application. Both LPME and EME were effective for substances with 2.0 < log P < 4.0, with EME showing faster extraction kinetics. Small (200 µL) and large vials (600 µL) were compared, showing that smaller vials improved kinetics markedly in both techniques. Carrier-mediated extraction showed improved performance for analytes with log P < 2 in EME, however, with some limitations due to system instability. This is, to our knowledge, the first time LPME was performed in the commercial vial-based equipment. An evaluation of vial-based LPME investigating linearity, precision, accuracy, and matrix effects showed promising results. These findings contribute to a general understanding of the performance differences in vial-based LPME and EME.

Electromembrane extraction of peptides based on hydrogen bond interactions

BACKGROUND

Electromembrane extraction (EME) of peptides reported in the scientific literature involve transfer of net positively charged peptides from an aqueous sample, through a liquid membrane, and into an aqueous acceptor solution, under the influence of an electrical field. The liquid membrane comprises an organic solvent, containing an ionic carrier. The purpose of the ionic carrier is to facilitate peptide solvation in the organic solvent based on ionic interactions. Unfortunately, ionic carriers increase the conductivity of the liquid membrane; the current in the system increases, the electrolysis in sample and acceptor is accelerated, and the extraction system tend to be unstable and suffers from drifting pH.

RESULTS

In the present work, a broad selection of organic solvents were tested as pure liquid membrane for EME of peptides, without ionic carrier. Several phosphates provided high mass transfer, and tri(pentyl) phosphate was selected since this solvent also provided high operational stability. Among 16 different peptides used as model analytes, tri(pentyl) phosphate extracted those with net charge +1 and with no more than two polar side chains. Tri(pentyl) phosphate served as a very strong hydrogen bond acceptor, while the protonated peptides were hydrogen bond donors. By such, hydrogen bonding served as the primary interactions responsible for mass transfer. Tri(pentyl) phosphate as liquid membrane, could exhaustively extract leu-enkephalin, met-enkephalin, and endomorphin from human blood plasma and detected by LC-MS/MS. Calibration curves were linear (r² > 0.99) within a concentration range from 1 to 500 ng/mL, and a relative standard deviation within 12% was observed for precision studies.

SIGNIFICANCE

The current experiments are important because they indicate that small peptides of low polarity may be extracted selectively in EME based on hydrogen bond interactions, in systems not suffering from electrolysis.

Electromembrane extraction of clenbuterol from swine urine for monitoring illegal use in livestock

The illegal use of clenbuterol seriously endangers food safety and human health. Accurate monitoring the illegal use of clenbuterol in livestock can efficiently prevent the clenbuterol residue pork products from entering the consumer market. Thus, in this study, a simple, rapid and sensitive method for the determination of clenbuterol in swine urine was developed using electromembrane extraction combined with liquid chromatography-tandem mass spectrometry. It should be noted that the electromembrane extraction method presented many advantages of simple operation, fast mass transfer rate, good sample clean-up capability and less organic solvent consumption. The effect of important factors on the extraction efficiency of clenbuterol was investigated. Under the optimal conditions, good linearity was achieved for clenbuterol over the range of 1-1000 ng/mL (R² = 0.9996). The recoveries of clenbuterol in swine urine at three spiked levels ranged from 83.7 to 110.0% with relative standard deviation values lower than 9.7% (n = 4). Limits of detection and quantification for clenbuterol were 0.07 and 0.25 ng/mL, respectively. These results suggested that the proposed method has great potential on the extraction and determination of trace analyte in complex sample matrix for monitoring the illegal use in livestock. This article is protected by copyright. All rights reserved.

Electromembrane extraction of nicotine in inhaled aerosols from tobacco cigarettes, electronic cigarettes, and heated tobacco products

Heated tobacco products and electronic cigarettes are considered as alternatives to traditional tobacco cigarettes. However, it is crucial to monitor and compare the nicotine concentration in inhaled aerosols from these tobacco products, owing to the addictive nature and adverse effects of nicotine on human health. This study aimed to provide an electromembrane extraction (EME) combined liquid chromatography method to extract and determine nicotine in different inhaled aerosols. EME showed high extraction efficiency, selectivity, and sample clean-up capability. Under the optimal parameters, the linear range for nicotine was 0.1-200 mg L^-1 (r² > 0.9998), and the limit of detection was 0.02 mg L^-1. Good precision was obtained with the intra- and inter-day relative standard deviations of 2.2 % and 2.8 %, respectively. Repeatability was satisfactory (<7.7 %), and recoveries ranged from 81.0 % to 112.8 %. Finally, this method has been successfully used for the determination and comparison of nicotine in aerosols from these three tobacco products.

Overview of Recent Liquid Chromatography Mass Spectrometry-Based Methods for Natural Toxins Detection in Food Products

Natural toxins include a wide range of toxic metabolites also occurring in food and products, thus representing a risk for consumer health. In the last few decades, several robust and sensitive analytical methods able to determine their occurrence in food have been developed. Liquid chromatography mass spectrometry is the most powerful tool for the simultaneous detection of these toxins due to its advantages in terms of sensitivity and selectivity. A comprehensive review on the most relevant papers on methods based on liquid chromatography mass spectrometry for the analysis of mycotoxins, alkaloids, marine toxins, glycoalkaloids, cyanogenic glycosides and furocoumarins in food is reported herein. Specifically, a literature search from 2011 to 2021 was carried out, selecting a total of 96 papers. Different approaches to sample preparation, chromatographic separation and detection mode are discussed. Particular attention is given to the analytical performance characteristics obtained in the validation process and the relevant application to real samples.

Simultaneous analysis of multiple pesticide residues in tobacco by magnetic carbon composite-based QuEChERS method and liquid chromatography coupled to quadrupole time-of-flight mass spectrometry

Magnetic carbon composite (Fe3O4@C) was synthesized and applied as a reversed-dispersive solid-phase extraction sorbent for the simultaneous analysis of 40 pesticide residues in tobacco by ultrahigh-performance liquid chromatography coupled to quadrupole time-of-fight mass spectrometry. Compared to the traditional QuEChERS method, the optimized Fe3O4@C simplified clean-up process and exhibited better clean-up capability than conventional sorbents. The pesticides were qualitatively identified by accurate mass of protonated molecules, fragment ions, isotopic peak clusters, and retention time, and quantitatively determined by matrix-matched external standard method. Good linearity of the proposed method was obtained with R value greater than 0.997 for all target pesticides at concentration levels of 2-200 µg/L. The limit of detection ranged from 0.14 to 2.67 µg/kg. The recoveries and relative standard deviations of all target pesticides at three spiked concentrations of 20, 50 and 200 µg/kg were in the ranges of 80.8%-113.3% and 0.6%-16.3%, respectively. Compared with the reported methods for the analysis of multiple pesticide residues in tobacco, the proposed method has the advantages of simple to operate, high clean-up ability and less time-consuming in clean-up process.