Accelerated air-assisted in-syringe extraction and needle spray ionization coupled with miniature mass spectrometry: A streamlined platform for rapid on-site analysis

Miniature mass spectrometers and their potential for clinical point-of-care analysis

Mass spectrometry (MS) has become a powerful technique for clinical applications with high sensitivity and specificity. Different from conventional MS diagnosis in laboratory, point-of-care (POC) analyses in clinics require mass spectrometers and analytical procedures to be friendly for novice users and applicable for on-site clinical diagnosis. The recent decades have seen the progress in the development of miniature mass spectrometers, providing a promising solution for clinical POC applications. In this review, we report recent advances of miniature mass spectrometers and their exploration in clinical applications, mainly including the rapid analysis of illegal drugs, on-site monitoring of therapeutic drugs, and detection of biomarkers. With improved analytical performance, miniature mass spectrometers are also expected to apply to more and more clinical applications. Some promising POC analyses that can be performed by miniature mass spectrometers in the future are discussed. Lastly, we also provide our perspectives on the challenges in technical development of miniature mass spectrometers for clinical POC analysis.

Microsyringe-based slug-flow microextraction for rapid and accurate determination of antibiotics in highly saline seawater

BACKGROUND

Extensive use of antibiotics leads to widespread environmental pollution, endangering ecosystems, and human health. It is particularly concerning, posing global threats requiring urgent attention and action. In this regard, the shift to mass spectrometry in determining antibiotics is highly desirable. Significant progress has been made in analyzing and optimizing the sensitivity of high-salt samples. However, the persistence of cumbersome operational procedures presents a significant challenge to this shift. Thus, the persistence of complex operational procedures needs to be addressed.

RESULTS

In this study, a rapid and direct method for determining antibiotics in highly saline environmental water samples using microsyringe-based slug-flow microextraction (MSFME)-droplet spray ionization (DSI) mass spectrometry (MS) has been described. The proposed method successfully detected clarithromycin, ofloxacin, and sulfadimidine in seawater within a linear range of 1-1200 ng mL-1, with low limits of detection of 0.19 ng mL-1, 0.17 ng mL-1, and 0.20 ng mL-1, respectively (Signal/Noise = 3). Additionally, spiked real seawater samples of all three antibiotics demonstrated satisfactory recoveries (95.1-107.5%) and precision (RSD≤8.8%). The MSFME-treated high-salt sample (3.5 wt%) showed a mass spectral response intensity 4-5 orders of magnitude higher than the untreated medium-salt sample (0.35 wt%). Furthermore, exploration of the applicability of MSFME showed that it is suitable not only for high-salinity (3.5 wt%) samples but also for salt-free or low-salt and hard water samples rich in calcium and magnesium ions.

SIGNIFICANCE

Comparisons with other methods, complex laboratory setups for sample processing are now simplified to a single step, completing the entire process, including desalination and detection, MSFME-DSI-MS provides faster results in less than 1 min while maintaining sensitivity comparable to that of other detection methods. In conclusion, this advancement provides an exceptionally simplified protocol for the rapid, highly sensitive, and quantitative determination of antibiotics in environmental water samples.

Development of dual-photoionization ion trap mass spectrometry and its application for direct analysis of VOCs in fruit aroma

Photoionization-ion trap mass spectrometry (PI-ITMS) is one of the major directions of mass spectrometer miniaturization because of its great potential for rapid on-site VOCs detection in many cases. Traditionally, PI has always been investigated separately and is restrained by ion transmission structure, so a new structure needs to be designed and investigated for simplifying and improving the ion transmission efficiency. Interestingly, our preliminary experiments found that the signal intensity and mass range can be effectively improved by combing atmospheric pressure photoionization (APPI) and low-pressure photoionization (LPPI). Therefore, in this paper, a new dual photoionization - ion trap mass spectrometry (DPI-ITMS) was developed, explored and used to directly analyze complex VOCs. Compared with traditional single PI configuration, it presents two obvious merits: (1) simplified ion transmission structure, eliminating the need to use deflection electrode to repel ions and avoiding breakdown risk. (2) some missing/weak low m/z ion mass spectral peaks in APPI and some high m/z ion mass spectral peaks in LPPI were improved in DPI detection mode. In addition, by combining multivariate statistical analysis, we preliminary achieved in differentiating fruit types and maturity level. In summary, we concluded that the developed DPI-ITMS has moderate detection sensitivity (limited by the homemade ITMS, 0.1-1 ppmv with RSD of 6.36 %), and the DPI-ITMS configuration can be referenced by future PI-MS, and this study also provides a high-throughput, simple, noninvasive and no chemical contamination solution for analyzing main VOCs in fruit aroma.

Applications of mass spectrometry in cosmetic analysis: An overview

Mass spectrometry (MS) is a crucial tool in cosmetic analysis. It is widely used for ingredient screening, quality control, risk monitoring, authenticity verification, and efficacy evaluation. However, due to the diversity of cosmetic products and the rapid development of MS-based analytical methods, the relevant literature needs a more systematic collation of information on this subject to unravel the true potential of MS in cosmetic analysis. Herein, an overview of the role of MS in cosmetic analysis over the past two decades is presented. The currently used sample preparation methods, ionization techniques, and types of mass analyzers are demonstrated in detail. In addition, a brief perspective on the future development of MS for cosmetic analysis is provided.

Online hyphenation of in-capillary aptamer-functionalized solid-phase microextraction and extraction nanoelectrospray ionization for miniature mass spectrometry analysis

Direct mass spectrometry (MS) analysis is vital to chemical and biological investigations. However, measuring complex samples is challenging due to matrix interference, resulting in compromised MS performance. In this study, an integrated experimental protocol has been developed, combining in-capillary aptamer-functionalized solid-phase microextraction (SPME), extraction nanoelectrospray ionization (nanoESI), and miniature MS analysis. The established method was applied to analyze caffeine in electronic cigarette liquid and beverage samples as proof-of-concept demonstrations. A custom SPME strip fabricated with caffeine-binding aptamers was prepared with an immobilization density of up to 0.812 nmol cm^-2. Critical parameters affecting the effects of extraction, desorption, and ionization were optimized. A novel transition ion ratio-based strategy with enhanced quantitation accuracy was developed. The analytical performance of the proposed method was evaluated under optimized conditions. Acceptable recoveries of 87.5-111.5% with relative standard deviations of 3.1-6.1% and satisfactory sensitivity with limits of detection of 1.5 and 3 ng mL^-1 and limits of quantitation of 5 and 10 ng mL^-1 were obtained, respectively. The developed approach demonstrates a promising potential for rapid on-site applications with appealing analytical performance and efficiency.

Nebulization Swab Assisted Photoionization Tandem Miniaturized Ion Trap Mass Spectrometry for On-Site Analysis of Nonvolatile Compounds

Nonvolatile compounds usually have a high molecular weight and exhibit a high boiling point, which poses great challenges to the ionization method of MS. Ambient ionization sources can efficiently analyze the nonvolatile compounds without complex pretreatment, but they generally require special media such as heating devices, laser optical devices, or corona needles. Acoustic nebulization assisted photoionization (ANPI) is a potential method for the analysis of nonvolatile compounds that uses nebulization as a prerequisite for photoionization and introduces many advantages of PI, including excellent ionization efficiency, a high yield of molecular ions, and simplified spectrum interpretation. However, the ANPI source can be limited in on-site applications by the complexity of the analytical devices and the high cost of the nebulization chip. To address this issue, in this paper, we explored cheap and commercially piezoelectric materials used in a mist sprayer and fabricated a nebulization swab assisted photoionization (NSAP) as an ambient ionization source. Some useful results are presented: numerical simulation was introduced successfully for optimizing the aerosol distribution in the NSAP source; nonvolatile muscle relaxants, drugs of abuse, antibiotics, phthalates, and cholesterol were detected mostly as their protonated molecular ions while some special acetone/water cluster ions were detected. In addition, the LOD for most of the target analytes ranged from 10.0 to 50.0 pg with RSD ≤ 9%. Finally, this method is implemented for Chinese baijiu spiked with phthalates. The experimental data shows the capability of a NSAP source in high sensitivity and on-site analysis of the nonvolatile compounds.

Microsampling with a Solid-Phase Extraction Cartridge: Storage and Online Mass Spectrometry Analysis

This study aims to introduce the concept of utilizing a solid-phase extraction (SPE) cartridge for remote biofluid collection, followed by direct sample analysis at a later time. For this, a dried matrix spot was prepared in a syringe, in the form of SPE cartridge for the first time to enable small biofluid collection (microsampling), storage, shipment, and online electrospray ionization (ESI) mass spectrometry (MS) analysis of the stored dried samples. The SPE sorbents were packed into an ESI syringe and the resultant cartridge was used for sampling small volumes (<20 μL) of different complex biological fluids including blood, plasma, serum, and urine. The collected sample was stored in the dry state within the confinement of the SPE sorbent at room temperature, and analyte stability (e.g., diazepam) was maintained for more than a year. Direct coupling of the SPE cartridge to MS provides excellent accuracy, precision, and sensitivity for analyzing illicit drugs present in the biofluid. The corresponding mechanism of wrong-way positive ion generation from highly basic elution solvents was explored. Without chromatography, our direct SPE-ESI-MS analysis technique afforded detection limits as low as 26 and 140 pg/mL for raw urine and untreated plasma, respectively. These promising results proved that the new syringe-based SPE cartridge can serve as a good alternative to conventional microsampling techniques in terms of analyte stability, ease of operation and versatility, and analytical sensitivity and speed.

Suspect Screening of Fentanyl Analogs Using Matrix-Assisted Ionization and a Miniature Mass Spectrometer with a Custom Expandable Mass Spectral Library

The reliable identification of fentanyl and its analogs is of great significance for public security. However, with the growing prevalence of fentanyl compounds, current analytical strategies cannot fully meet the need for fast and high-throughput detection. In this study, a simple, rapid, and on-site analytical protocol was developed based on a miniature mass spectrometer. A dramatically simplified workflow was implemented using matrix-assisted ionization, bypassing complex sample pretreatment and chromatographic separation. The tandem mass spectrometry (MS/MS) capability afforded by the miniature ion trap mass spectrometer facilitated the investigation of fragmentation patterns for 49 fentanyl analogs during collision-induced dissociation, revealing valuable information on marker fragment ions and characteristic neutral loss. Calculations on Laplacian bond order values further verified the mass spectrometric behavior. A computation-assisted expandable mass spectral library was constructed in-house for fentanyl compounds. Smart suspect screening was carried out based on the full-scan MS and MS/MS data. The present study demonstrates an appealing potential for forensic applications, enabling streamlined screening for the presence of illicit fentanyl compounds at the point of seizures of suspect samples.