Microtrace Analysis of Rare Earth Element Residues in Femtogram Quantities by Laser Desorption and Laser Postionization Mass Spectrometry

Advances in mass spectrometry imaging for plant metabolomics-Expanding the analytical toolbox

Mass spectrometry imaging (MSI) has become increasingly popular in plant science due to its ability to characterize complex chemical, spatial, and temporal aspects of plant metabolism. Over the past decade, as the emerging and unique features of various MSI techniques have continued to support new discoveries in studies of plant metabolism closely associated with various aspects of plant function and physiology, spatial metabolomics based on MSI techniques has positioned it at the forefront of plant metabolic studies, providing the opportunity for far higher resolution than was previously available. Despite these efforts, profound challenges at the levels of spatial resolution, sensitivity, quantitative ability, chemical confidence, isomer discrimination, and spatial multi-omics integration, undoubtedly remain. In this Perspective, we provide a contemporary overview of the emergent MSI techniques widely used in the plant sciences, with particular emphasis on recent advances in methodological breakthroughs. Having established the detailed context of MSI, we outline both the golden opportunities and key challenges currently facing plant metabolomics, presenting our vision as to how the enormous potential of MSI technologies will contribute to progress in plant science in the coming years.

LASER IONIZATION MASS SPECTROMETRY AT 55: QUO VADIS?

Laser ionization mass spectrometry (LIMS) was one of the first practical methods developed for in situ analysis of the surfaces of solid samples. This review will encompass several aspects related to this analytical method. First, we will discuss the process of laser ionization, the influence of the laser type on its performance, and imaging capabilities of this method. In the second chapter, we will follow the historic development of LIMS instrumentation. After a brief overview of the first-generation instruments developed in 1960-1990 years, we will discuss in detail more recent designs, which appeared during the last 2-3 decades. In the last part of our review, we will cover the recent applications of LIMS for surface analysis. These applications include various types of analyses of solid inorganic, organic, and heterogeneous samples, often in combination with depth profiling and imaging capability.

Insights into the degradation and toxicity difference mechanism of neonicotinoid pesticides in honeybees by mass spectrometry imaging

Honeybees are essential for the pollination of a wide variety of crops and flowering plants, whereas they are confronting decline around the world due to the overuse of pesticides, especially neonicotinoids. The mechanism behind the negative impacts of neonicotinoids on honeybees has attracted considerable interest, yet it remains unknown due to the limited insights into the spatiotemporal distribution of pesticides in honeybees. Herein, we demonstrated the use of matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) for the spatiotemporal visualization of neonicotinoids, such as N-nitroguanidine (dinotefuran) and N-cyanoamidine (acetamiprid) compounds, administered by oral application or direct contact, in the whole-body section of honeybees. The MSI results revealed that both dinotefuran and acetamiprid can quickly penetrate various biological barriers and distribute within the whole-body section of honeybees, but acetamiprid can be degraded much faster than dinotefuran. The degradation rate of acetamiprid is significantly decreased when piperonyl butoxide (PBO) is applied, whereas that of dinotefuran remains almost unchanged. These two factors might contribute to the fact that dinotefuran affords a higher toxicity to honeybees than acetamiprid. Moreover, the toxicity and degradation rate of acetamiprid can be affected by co-application with tebuconazole. Taken together, the results presented here indicate that the discrepant toxicity between dinotefuran and acetamiprid does not lie in the difference in their penetration of various biological barriers of honeybees, but in the degradation rate of neonicotinoid pesticides within honeybee tissues. Moreover, new perspectives are given to better understand the causes of the current decline in honeybee populations posed by insecticides, providing guidelines for the precise use of conventional agrochemicals and the rational design of novel pesticide candidates.

Spatiotemporal Visualization of Insecticides and Fungicides within Fruits and Vegetables Using Gold Nanoparticle-Immersed Paper Imprinting Mass Spectrometry Imaging

Food safety issues caused by pesticide residue have exerted far-reaching impacts on human daily life, yet the available detection methods normally focus on surface residue rather than pesticide penetration to the internal area of foods. Herein, we demonstrated gold nanoparticle (AuNP)-immersed paper imprinting mass spectrometry imaging (MSI) for monitoring pesticide migration behaviors in various fruits and vegetables (i.e., apple, cucumber, pepper, plum, carrot, and strawberry). By manually stamping food tissues onto AuNP-immersed paper, this method affords the spatiotemporal visualization of insecticides and fungicides within fruits and vegetables, avoiding tedious and time-consuming sample preparation. Using the established MSI platform, we can track the migration of insecticides and fungicides into the inner region of foods. The results revealed that both the octanol-water partition coefficient of pesticides and water content of garden stuffs could influence the discrepancy in the migration speed of pesticides into food kernels. Taken together, this nanopaper imprinting MSI is poised to be a powerful tool because of its simplicity, rapidity, and easy operation, offering the potential to facilitate further applications in food analysis. Moreover, new perspectives are given to provide guidelines for the rational design of novel pesticide candidates, reducing the risk of food safety issues caused by pesticide residue.

Discrimination of isomeric monosaccharide derivatives using collision-induced fingerprinting coupled to ion mobility mass spectrometry

Because of the isomeric heterogeneity that is ubiquitous in analytical science, a formidable analytical challenge is to fully discriminate multiple isomers, especially those candidate isomers with various biological functions. Ion mobility mass spectrometry (IM-MS) has gained impressive advances for gaining molecular conformations, whereas coexisting structurally similar isomers often make unambiguous discrimination impossible due to the limited IM resolution of commercially available instruments. Herein, we demonstrate an energy-resolved collision-induced fingerprint (CIF) method to fully discriminate isomeric monosaccharide derivatives that differ in terms of composition, connectivity and configuration without complex instrument modifications. By simply increasing the collisional energy in the trap cell, the full width at half maximum (FWHM) of IM peaks can be markedly narrowed by at least 2-fold. Given the excellent reproducibility of CIF measurements, the full discrimination of isomers can benefit from their unique feature values and root-mean square deviation (RMSD) in CIF spectra. Moreover, rapid discrimination of each monosaccharide derivate isomer from binary mixtures is demonstrated. This strategy will expand the horizons of IM-MS platform in the rapid differentiation of a wider range of isomers more than monosaccharide derivatives in complex systems, which facilitates the identification and evaluation of innovative isomer candidates with unexplored functions.

In Situ Analysis of Surface Catalytic Reactions Using Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy

Electrochemistry and heterogeneous catalysis continue to attract enormous interest. In situ surface analysis is a dynamic research field capable of elucidating the catalytic mechanisms of reaction processes. Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) is a nondestructive technique that has been cumulatively used to probe and analyze catalytic-reaction processes, providing important spectral evidence about reaction intermediates produced on catalyst surfaces. In this perspective, we review recent electrochemical- and heterogeneous-catalysis studies using SHINERS, highlight its advantages, summarize the flaws and prospects for improving the SHINERS technique, and give insight into its future research directions.

Rapid Trace Detection and Isomer Quantitation of Pesticide Residues via Matrix-Assisted Laser Desorption/Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS) has been applied for rapid, sensitive, undisputed, and quantitative detection of pesticide residues on fresh leaves with little sample pretreatment. Various pesticides (insecticides, bactericides, herbicides, and acaricides) are detected directly in the complex matrix with excellent limits of detection down to 4 μg/L. FTICR-MS could unambiguously identify pesticides with tiny mass differences (∼0.017 75 Da), thereby avoiding false-positive results. Remarkably, pesticide isomers can be totally discriminated by use of diagnostic fragments, and quantitative analysis of pesticide isomers is demonstrated. The present results expand the horizons of the MALDI-FTICR-MS platform in the reliable determination of pesticides, with integrated advantages of ultrahigh mass resolution and accuracy. This method provides growing evidence for the resultant detrimental effects of pesticides, expediting the identification and evaluation of innovative pesticides.