Chuping Lee

In-situ detection is essential for pollutant source tracking and timely environmental management, particularly in dynamic water systems. However, implementing such detection remains challenging for trace organic contaminants such as per- and polyfluoroalkyl substances (PFASs) because their pg mL−1 level concentrations and complex matrix interferences often necessitate time-consuming LC−QqQ MS workflows. Herein, we developed a field-deployable analytical platform integrating CO2 microbubble preconcentration and portable MS to enable the rapid quantification of perfluorocarboxylic acids (PFCAs), a major class of PFASs. This platform leverages PFCA surface activity to drive sequential transfer from bulk water to the CO2 bubble−water interface and subsequently into bursting microdroplets, achieving >1100-fold enrichment of two common PFCAs, PFOA and PFNA, within 5 min. This enrichment may be associated with fine, slow-rising CO2 microbubbles that prolong interfacial contact and CO2-induced acidification that may favor anionic PFCA accumulation at the bubble−water interface. Based on this platform, method validation with PFOA and PFNA in drinking water revealed 80−112% recovery, high inter- and intraday precision of 3−16% RSD, and method quantification limits of 0.55−1.0 pg mL−1. Field deployment in lake and river waters successfully quantified PFOA and PFNA at concentrations of 2.4−4.1 and 0.8−1.1 pg mL−1, respectively. To our knowledge, this is one of the first portable MS/MS-based workflows capable of pg mL−1 level PFCA quantification in environmental waters. Crucially, these on-site results were consistent with conventional laboratory-based analysis, supporting this platform as a rapid (<10 min) and practical tool for dynamic environmental monitoring.

Per- and polyfluoroalkyl substances (PFASs) are highly persistent and bioaccumulative contaminants that pose serious ecological and human health risks even at trace levels. In this study, we developed a rapid and eco-friendly bubble preconcentration–surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) method for PFAS detection in water. Compared with our previous design, the average bubble size was reduced from 312 to 243 μm, enhancing the enrichment of short-chain PFASs. Using an iron-based metal–organic framework (MIL-101(Fe)) as the assisting material, the method achieved enrichment ratios of 700-fold for PFOS and 400-fold for PFHxS within 30 s. The entire analysis is completed within minutes without organic solvents, offering substantial reductions in time and waste compared with conventional SPE–LC–MS/MS. PFOS concentration of ~3 ng/L was detected in Tamsui River samples, consistent with LC–MS/MS results. This solvent-free, small-bubble-based method provides a sustainable approach for rapid PFAS monitoring in environmental waters. Graphical abstract

This Perspective covers discovery and mechanistic aspects as well as initial applications of novel ionization processes for use in mass spectrometry that guided us in a series of subsequent discoveries, instrument developments, and commercialization. Vacuum matrix-assisted ionization on an intermediate pressure matrix-assisted laser desorption/ionization source without the use of a laser, high voltages, or any other added energy was simply unbelievable, at first. Individually and as a whole, the various discoveries and inventions started to paint, inter alia, an exciting new picture and outlook in mass spectrometry from which key developments grew that were at the time unimaginable, and continue to surprise us in its simplistic preeminence. We, and others, have demonstrated exceptional analytical utility. Our current research is focused on how best to understand, improve, and use these novel ionization processes through dedicated platforms and source developments. These ionization processes convert volatile and nonvolatile compounds from solid or liquid matrixes into gas-phase ions for analysis by mass spectrometry using, e.g., mass-selected fragmentation and ion mobility spectrometry to provide accurate, and sometimes improved, mass and drift time resolution. The combination of research and discoveries demonstrated multiple advantages of the new ionization processes and established the basis of the successes that lead to the Biemann Medal and this Perspective. How the new ionization processes relate to traditional ionization is also presented, as well as how these technologies can be utilized in tandem through instrument modification and implementation to increase coverage of complex materials through complementary strengths.

In the work, a pig-blood-derived mesoporous carbon (BC) was prepared as a novel Fe-N-C material for the electrochemical sensor to detect hydrogen peroxide. Because of the unique nanostructure of Fe-BCs with rough surface structure, hierarchical pores, and high graphitization degree, the Fe-BCs, as a kind of advanced electrode material, exhibited remarkable performance in electrocatalysis. The sensor based on Fe-BCs exhibited an extra-long range from c and a detection limit of 0.046 μM (S/N = 3). The synthesis of low-cost, advanced carbon-based electrode materials from environmentally friendly pig blood for electrochemical sensor construction is a promising approach.

Edible oils are valuable sources of nutrients, and their classification is necessary to ensure high quality, which is essential to food safety. This study reports the establishment of a rapid and straightforward SALDI-TOF MS platform used to detect triacylglycerol (TAG) in various edible oils. Silver nanoplates (AgNPts) were used to optimize the SALDI samples for high sensitivity and reproducibility of TAG signals. TAG fingerprints were combined with multivariate statistics to identify the critical features of edible oil discrimination. Eleven various edible oils were discriminated using principal component analysis (PCA). The results suggested the creation of a robust platform that can examine food adulteration and food fraud, potentially ensuring high-quality foods and agricultural products.

We developed a preconcentration method in which aerosol droplets containing enriched perfluorinated sulfonic acids (PFSs) are generated through bubble bursting and collected. The droplets were subjected to PFS analysis of perfluorohexane sulfonic acid (PFHxS) and perfluorooctanesulfonic acid (PFOS) through surface‐assisted laser desorption/ionization‐time‐of‐flight mass spectrometry; silver nanoplates (AgNPts) were assisting materials. The method was highly efficient, with an approximately three‐order magnitude enhancement (5 × 10⁻¹³ to 1 × 10⁻¹¹ M). Ultralow PFS concentrations (0.5 ng/L of PFOS; 0.4 ng/L of PFHxS) were detected in preconcentrated tap water containing PFSs. Our method has potential for rapid real‐world PFS detection in water.

A series of novel anthranilic acid derivatives I-IV, of which COOH-NH2 (I) and COOH-NHMe (IV) are endowed with acid and base bifunctionality, were designed and synthesized for matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry applications in dual polarity molecular imaging of biological samples, particularly for lipids. The heat of protonation, deprotonation and proton transfer reaction as well as the capability of analyzing biomol-ecules in both positive and negative ion modes for I-IV were systematically investigated under standard 355-nm laser excitation. The results indicate correlation between dual polarity and acid-base property. Further, COOH-NHMe (IV) showed a unique performance and was successfully applied as the matrix for MALDI-TOF mass spectrometry imaging (MSI) for studying the mouse brain. Our results demonstrate the superiority of COOH-NHMe (IV) in detecting more lipid and protein species compared to commercially available matrices. Moreover, MALDI-TOF MSI results were obtained for lipid distributions, making COOH-NHMe (IV) a potential next generation universal matrix.

Adenosine -5′-triphosphate (ATP) plays a valuable role in metabolic activity to produce adequate energy in a biosystem. A high ATP/AMP ratio has a correlation with diabetes that induces suppression of AMP-activated protein kinase (AMPK). Matrix-assisted laser desorption/ionization (MALDI)–mass spectrometry (MS) has outstanding potential in determining the ratio of several types of adenosine phosphates in a sample to rapidly understand the primary energy transfer in metabolism. Although MALDI is viewed as a soft ionization technique for MS analysis, excess photon energy might crack the phosphate bonds leading to misinterpretation of the ATP level. In this work, ionic liquid matrices (ILMs) were employed to reduce fragmentation and increase the detection efficiency during the MALDI process. This study demonstrated for the first time that 2,5-dihydroxybenzoic acid pyridine (DHBP) is one of the most effective matrices for further quantitative analysis of adenosine nucleotides. This systematic screening of ILMs also enhances the fundamental understanding of MALDI.