Applications of nanomaterials in ambient ionization mass spectrometry

Rapid on-site detection of persistent organic pollutants using multiwalled carbon nanotube-modified paper spray ionization and a miniature mass spectrometer

RATIONALE

Rapid on-site detection of persistent organic pollutants (POP) is highly desirable for environmental protection.

METHODS

Herein, a rapid on-site analytical workflow was developed for the investigation of polycyclic aromatic hydrocarbons and perfluorinated compounds using multiwalled carbon nanotube-modified paper spray ionization (PSI) coupled with a miniature ion trap mass spectrometer. Critical parameters regarding PSI and miniature mass spectrometry analysis were optimized.

RESULTS

The analytical performance of the developed method was evaluated under optimized conditions, obtaining a short analysis duration of less than 1 min, sufficient linearity with correlation coefficients greater than 0.99, acceptable recovery rates of 93.1%-105.8% with relative standard deviations of between 3.5% and 10.3%, and reasonable sensitivity with limits of detection and quantitation of 2-200 and 5-500 μg/L, respectively.

CONCLUSIONS

Considering these aspects, it was concluded that the present approach demonstrated a promising solution for rapid on-site detection of emerging POPs.

Point-of-care applicable metabotyping using biofluid-specific electrospun MetaSAMPs directly amenable to ambient LA-REIMS

In recent years, ambient ionization mass spectrometry (AIMS) including laser ablation rapid evaporation IMS, has enabled direct biofluid metabolome analysis. AIMS procedures are, however, still hampered by both analytical, i.e., matrix effects, and practical, i.e., sample transport stability, drawbacks that impede metabolome coverage. In this study, we aimed at developing biofluid-specific metabolome sampling membranes (MetaSAMPs) that offer a directly applicable and stabilizing substrate for AIMS. Customized rectal, salivary, and urinary MetaSAMPs consisting of electrospun (nano)fibrous membranes of blended hydrophilic (polyvinylpyrrolidone and polyacrylonitrile) and lipophilic (polystyrene) polymers supported metabolite absorption, adsorption, and desorption. Moreover, MetaSAMP demonstrated superior metabolome coverage and transport stability compared to crude biofluid analysis and was successfully validated in two pediatric cohorts (MetaBEAse, n = 234 and OPERA, n = 101). By integrating anthropometric and (patho)physiological with MetaSAMP-AIMS metabolome data, we obtained substantial weight-driven predictions and clinical correlations. In conclusion, MetaSAMP holds great clinical application potential for on-the-spot metabolic health stratification.

Development of Magnetic Molecularly Imprinted Polymer Coupled Nanospray Ion Source for Analysis of Cephalosporin Antibiotics in Food Samples

A magnetic molecularly imprinted polymer (MMIP) coupled nanospray ion source was developed for analysis of cephalosporin antibiotics in food samples. MIP coated Fe₃O₄ nanospheres were prepared for magnetic solid-phase extraction (MSPE) of the antibiotics in the extract of samples and then integrated into the nanospray capillary for further desorption and mass spectrometry analysis. The developed device combines the advantages of high extraction efficiency of MSPE, unique selectivity of MIPs, and fast analysis speed of ambient ionization mass spectrometry (AIMS). Five cephalosporin antibiotics in milk, egg, and beef samples were analyzed using the developed methods. High sensitivities with limits of detection (LODs) from 0.3 to 0.5 μg kg^-1 were achieved for cephalosporin antibiotics in milk, egg, and beef samples, respectively. Good linearity, determination coefficient values (R² > 0.992), and precision (RSD < 15%) with recoveries ranging from 72.6% to 115.5% were obtained using the spiked milk, egg, and beef sample matrices.

Routine analysis of pesticides in foodstuffs: Emerging ambient ionization mass spectrometry as an alternative strategy to be on your radar

Pesticides residues in foodstuffs are longstanding of great concern to consumers and governments, thus reliable evaluation techniques for these residues are necessary to ensure food safety. Emerging ambient ionization mass spectrometry (AIMS), a transformative technology in the field of analytical chemistry, is becoming a promising and solid evaluation technology due to its advantages of direct, real-time and in-situ ionization on samples without complex pretreatments. To provide useful guidance on the evaluation techniques in the field of food safety, we offered a comprehensive review on the AIMS technology and introduced their novel applications for the analysis of residual pesticides in foodstuffs under different testing scenarios (i.e., quantitative, screening, imaging, high-throughput detection and rapid on-site analysis). Meanwhile, the creative combination of AIMS with high-resolution mass analyzer (e.g., orbitrap and time-of-flight) was fundamentally mentioned based on recent studies about the detection and evaluation of multi-residual pesticides between 2015 and 2021. Finally, the technical challenges and prospects associated with AIMS operation in food industry were discussed.

Thread-based isotachophoresis coupled with desorption electrospray ionization mass spectrometry for clean-up, preconcentration, and determination of alkaloids in biological fluids

A thread-based isotachophoresis method coupled with desorption electrospray ionization mass spectrometry (TB-ITP-DESI-MS) was developed and applied for clean-up, preconcentration, and determination of alkaloids in biological fluids. This simple approach enables the focusing and rapid analysis of analytes of interest in complex matrices that are otherwise challenging using direct ambient mass spectrometry. The TB-ITP platform components were rapidly and reproducibly fabricated at low-cost using 3D printing. A single string of nylon 6 thread was used as the electrophoresis substrate and a cotton knot, tied to the nylon thread, was used as the trapping zone of the ITP focused model analytes (coptisine, berberine and palmatine). The trapping efficiency was evaluated upon different commercially available threads with different chemical properties and cotton was selected as the best material due to its highest trapping efficiency and subsequent DESI-MS ionization efficiency. Up to 11.6-fold increase in signal to noise ratio (S/N) was obtained using the proposed method compared to direct DESI-MS detection, due to the reduced matrix interference and focusing. The results demonstrated that the TB-ITP-DESI-MS approach is a viable solution for the analysis of complicated biological fluid samples.

Nanomaterial-assisted thread-based isotachophoresis with on-thread solute trapping

This research describes a nanomaterial-assisted TB-ITP setup for the clean-up, preconcentration, and trapping of alkaloids in biological fluids, followed by their on-thread DESI-MS determination.