The scope of cross-sector applications for mass spectrometry imaging continues to expand – from food safety to new applications in environmental monitoring

The initial impetus for mass spectrometry imaging technology lay in the biomedical field—the distribution of lipids in brain tissue, the metabolic subtyping of tumour tissue, and the tracking of drug distribution within organs have constituted the most typical applications of this technology over the past decade. However, in the last two years, a noteworthy trend has emerged: the boundaries of mass spectrometry imaging are rapidly expanding into non-biomedical fields such as food testing, environmental analysis, forensic science and agricultural science. Underpinning this cross-sector expansion are the continuous advancements in mass spectrometry imaging sources and ion source technologies—higher sensitivity, a broader molecular coverage range and greater flexibility in sample adaptation have enabled a technology once confined to biological tissues to accommodate a more diverse range of sample types.

Food safety testing: from ‘total quantity analysis’ to ‘spatial distribution’

Traditional mass spectrometry methods (LC-MS, GC-MS) used in food safety testing answer the question of ‘how much’—namely, whether the total amount of a particular pesticide residue or additive exceeds the permissible limit. However, in many practical scenarios, regulators and researchers need to answer the question of ‘where’—are pesticide residues evenly distributed across the surface of fruit and vegetables, or are they concentrated in a specific area? In which structural layer of the food are contaminants introduced during processing distributed?

Mass spectrometry imaging provides direct answers to such spatial distribution questions. Taking tea leaves as an example, researchers can use a mass spectrometry imager to scan tea leaf sections, simultaneously obtaining spatial distribution maps of dozens of pesticide residues and metabolites within the tea leaf tissue. Traditional methods require the entire tea leaf to be ground and extracted before analysis, resulting in the complete loss of spatial information; mass spectrometry imaging, however, can clearly show whether pesticide residues are concentrated in the epidermal layer or have penetrated into the mesophyll tissue, providing intuitive evidence for assessing the effectiveness of washing processes.

In the field of meat safety, scanning slices of meat products using mass spectrometry imaging ion sources can reveal the spatial distribution of veterinary drug residues, colouring additives and spoilage metabolites. Differences in the distribution of characteristic metabolites across different regions reflect gradients in meat freshness and the uniformity of processing—information that cannot be obtained through traditional homogenised testing.

Environmental monitoring: microplastics and the tracing of pollutants

Environmental analysis is another active area of cross-disciplinary application for mass spectrometry imaging.

Research into microplastic pollution has become a hot topic in environmental science in recent years, but traditional methods lack the spatial resolution required to characterise organic pollutants adsorbed onto microplastic surfaces. Mass spectrometry imaging instruments can directly scan the surfaces of microplastic particles, revealing the adsorption distribution patterns of pollutants such as polycyclic aromatic hydrocarbons and plasticisers on their surfaces. This spatial information aids in understanding the migration and release behaviour of microplastics in the environment as ‘pollutant carriers’.

Applications of mass spectrometry imaging have also emerged in the analysis of soil pollutants. By preparing thin sections of soil and scanning them using mass spectrometry imaging, researchers can observe the microscopic distribution of heavy metal complexes and organic pollutants within soil aggregates. Traditional soil testing involves digesting samples and measuring total concentrations; this method cannot distinguish whether pollutants are attached to the surface of organic matter or bound within the mineral lattice—a distinction that is crucial for assessing the bioavailability of pollutants and selecting remediation strategies.

In the field of atmospheric science, the concept of mass spectrometry imaging has also been applied to the analysis of the organic components of particulate matter. The distribution of particulate matter on PM2.5 filter membranes can be directly scanned using a mass spectrometry imaging ion source, providing information on the distribution of organic components across particles of different sizes, thereby aiding in the identification of pollution sources.

Forensic Science: Molecular-level visualisation of physical evidence

Forensic science places extremely high demands on the non-destructive analysis of physical evidence and the preservation of spatial information; the ‘labelling-free, extraction-free’ characteristics of mass spectrometry imaging demonstrate unique value in this field.

The analysis of chemical residues on fingerprints is a typical application. Whilst traditional fingerprint analysis focuses on physical ridges, mass spectrometry imaging can capture the molecular distribution of drugs, explosive residues and cosmetic ingredients remaining on the fingerprint whilst preserving the ridge information. Law enforcement agencies can use this chemical information to infer the occupational characteristics of the person who left the fingerprint or items they have recently come into contact with, thereby providing clues for case investigation.

In the examination of documentary evidence, mass spectrometry imaging enables molecular-level analysis of ink, seals and paper. Differences in the chemical composition of different brands of ink and the layered structure of seal ink can all be presented in the form of molecular images, assisting in determining the authenticity and age of documents.

Agricultural Science: From the Laboratory to the Field

Agricultural research institutions are introducing mass spectrometry imaging into crop breeding and quality assessment research.

The analysis of seed component distribution is one of the earliest areas of agricultural application. By scanning seed sections using mass spectrometry imaging, spatial distribution maps of lipids, proteins, starch and secondary metabolites within the seed can be obtained. There are significant differences in the compositional distribution patterns of seeds from different varieties, and these differences are related to the seeds’ nutritional quality, storage stability and germination characteristics. Breeders can use this information to screen for high-quality varieties and evaluate the chemical quality of seeds at the laboratory level without the need for lengthy field trials.

Research into root–soil interactions is another emerging field. Researchers prepare sections of the interface between plant roots and soil, and use mass spectrometry imaging to scan the range of diffusion and distribution gradients of root exudates within the soil. This information is crucial for understanding the mechanisms of plant–soil–microbial interactions; traditional methods are unable to determine the spatial distribution of root exudates in the soil.

Technological Iteration Drives Cross-Disciplinary Expansion

The expansion of cross-disciplinary applications does not occur spontaneously; it relies on continuous advancements in mass spectrometry imaging sources and imaging ion source technologies.

Traditional mass spectrometry imaging sources are predominantly optimised for biological tissue sections and have limited suitability for non-biological samples such as food, soil and filter membranes. The new Ceyuan MSI DPI electrospray/photochemical ionisation mass spectrometry imaging source employs a DESI+ post-photoionisation dual-ionisation architecture. The electrospray mechanism of DESI offers broad compatibility with sample morphology—whether biological tissues, food sections or filter membrane surfaces—allowing direct analysis without the need for complex pretreatment. The VUV photoionisation stage of post-photoionisation further expands the range of detectable molecules, enabling the effective detection of non-polar compounds (such as fat-soluble vitamins in food and polycyclic aromatic hydrocarbons in environmental samples).

The MSI LDPI laser/photochemical ionisation mass spectrometry imaging source, with its spatial resolution of 2–3 μm, offers advantages in cross-disciplinary applications requiring high spatial resolution (such as microplastic surface analysis and seed microstructure imaging). Its transmission-type laser desorption design exhibits high tolerance for sample surface topography, making it suitable for solid samples with uneven surfaces.

Both imaging ion sources are compatible with mass spectrometers from the three major brands—Agilent, AB SCIEX and Thermo Fisher. This means that food testing organisations, environmental monitoring stations and forensic laboratories already equipped with imported mass spectrometers can retrofit imaging capabilities without purchasing new instruments, significantly reducing the entry costs for cross-disciplinary applications.

Industry Insights

The expansion of mass spectrometry imaging technology from biomedical to non-biomedical fields essentially represents an upgrade in testing requirements from ‘what is present’ to ‘where it is located’. Traditional mass spectrometry methods address total quantity, whilst mass spectrometry imaging addresses spatial distribution—the two are complementary rather than mutually exclusive. When regulatory requirements for food safety evolve from “whether limits are exceeded” to “where the exceedances occur”, and when environmental monitoring requirements shift from “total compliance” to “the form in which pollutants are present”, the market for mass spectrometry imaging expands from biomedical laboratories to a broader range of testing and analysis fields.

For domestic manufacturers of mass spectrometry imaging sources, cross-sector applications signify a diversification of the user base—no longer limited to research institutes in the life sciences, but now including food testing organisations, environmental monitoring stations and public security forensic centres as potential clients. This expansion of the user base will provide stronger demand support for the market promotion of domestically produced imaging ion source products.