Component Profiling in Agricultural Applications Using an Adjustable Acupuncture Needle for Sheath-Flow Probe Electrospray Ionization/Mass Spectrometry

Rapid analysis of untreated food samples by gel loading tip spray ionization mass spectrometry

Rapid, efficient, versatile, easy-to-use, and non-expensive analytical approaches are globally demanded for food analysis. Many ambient ionization approaches based on electrospray ionization (ESI) have been developed recently for the rapid molecular characterization of food products. However, those approaches mainly suffer from insufficient signal duration for comprehensive chemical characterization by tandem MS analysis. Here, a commercially available disposable gel loading tip is used as a low-cost emitter for the direct ionization of untreated food samples. The most important advantages of our approach include high stability, and durability of the signal (> 10 min), low cost (ca. 0.1 USD per run), low sample and solvent consumption, prevention of tip clogging and discharge, operational simplicity, and potential for automation. Quantitative analysis of sulfapyridine, HMF (hydroxymethylfurfural), and chloramphenicol in real sample shows the limit-of-detection 0.1 μg mL-1, 0.005 μg mL-1, 0.01 μg mL-1; the linearity range 0.1-5 μg mL-1, 0.005-0.25 μg mL-1, 0.01-1 μg mL-1; and the linear fits R2 ≥ 0.980, 0.991, 0.986. Moreover, we show that tip-ESI can also afford sequential molecular ionization of untreated viscous samples, which is difficult to achieve by conventional ESI. We conclude that tip-ESI-MS is a versatile analytical approach for the rapid chemical analysis of untreated food samples.

A direct analysis method using sheath flow probe electrospray ionisation-mass spectrometry (sfPESI-MS) to detect drug residues from fingerprint forensic gel lifts

Latent fingerprints at crime scenes are frequently recovered using forensic gel-lifters, which can help to preserve the crime scene and to enhance visualisation of traces such as blood or paint. In addition to providing fingerprint ridge detail, additional chemical information can also be recovered from gel lifts that may prove pertinent to an investigation. However, while DNA and metal ions have been shown to be able to be detected in gel-lifted fingerprints, the determination of other types of chemical information such as the presence of drugs in gel-lifted prints has not been previously shown. This study demonstrates the application of an ambient ionisation method, sheath flow probe electrospray ionisation-mass spectrometry (sfPESI-MS), to the direct analysis of gel-lifted fingerprints. A model drug compound (zolpidem) is successfully detected from gel-lifted prints from three different surface types: glass, metal, and paper. The surface activity-based separation associated with probe electrospray approaches is shown to resolve zolpidem ions from background phthalate species, significantly enhancing the response obtained from the gel-lifter. A depletion series experiment shows that the drug residue can be detected with up to 100% efficiency after eight consecutive contacts; however, detection efficiency drops to 20% after 30 contacts. The developed approach has potential application to analysis of historical gel-lifters to obtain additional chemical information.

Plastic probe electrospray ionization mass spectrometry developed for rapid fingerprint profile of biological samples without pretreatment

A triangular-shaped flat plastic substrate probe was prepared for direct electrospray ionization mass spectrometry (ESI-MS) for analysis of untreated chemical and biological samples including liquids (Met-Arg-Phe-Ala peptide, reserpine, and dodecyl aldehyde), solids (biological samples, traditional Chinese medicine), and powders (roasted coffee, rhizoma coptidis, lotus plumule, and Schisandra sphenanthera). Quantitative analysis of reserpine in water yielded a detection limit of 1 ng mL-1, dynamic response range within 1-500 ng mL-1, and linearity of signal response ˃0.9925. Compared to the conventional capillary ESI, this plastic probe ESI offers lower cost of analysis (US $0.0056 per probe), higher sensitivity, lower sample consumption, longer signal duration (>6 min), better reproducibility, signal stability, and higher speed of analysis (<10 s per sample, including sample loading). Overall, the results indicate the potential of ESI-MS based on flat plastic probes as a versatile method for simple, sensitive, and stable analysis of untreated biological sample analysis.

Applications of ambient ionization mass spectrometry in 2022: An annual review

The development of ambient ionization mass spectrometry (AIMS) has transformed analytical science, providing the means of performing rapid analysis of samples in their native state, both in and out of the laboratory. The capacity to eliminate sample preparation and pre-MS separation techniques, leading to true real-time analysis, has led to AIMS naturally gaining a broad interest across the scientific community. Since the introduction of the first AIMS techniques in the mid-2000s, the field has exploded with dozens of novel ion sources, an array of intriguing applications, and an evident growing interest across diverse areas of study. As the field continues to surge forward each year, ambient ionization techniques are increasingly becoming commonplace in laboratories around the world. This annual review provides an overview of AIMS techniques and applications throughout 2022, with a specific focus on some of the major fields of research, including forensic science, disease diagnostics, pharmaceuticals and food sciences. New techniques and methods are introduced, demonstrating the unwavering drive of the analytical community to further advance this exciting field and push the boundaries of what analytical chemistry can achieve.

High-throughput analysis of anthocyanins in horticultural crops using probe electrospray ionization tandem mass spectrometry (PESI/MS/MS)

Plant secondary metabolites exhibit various horticultural traits. Simple and rapid analysis methods for evaluating these metabolites are in demand in breeding and consumer markets dealing with horticultural crops. We applied probe electrospray ionization (PESI) to evaluate secondary metabolite levels in horticultural crops. PESI does not require pre-treatment and separation of samples, which makes it suitable for high-throughput analysis. In this study, we targeted anthocyanins, one of the primary pigments in horticultural crops. Eighty-one anthocyanins were detected in approximately 3 minutes in the selected reaction-monitoring mode. Tandem mass spectrometry (MS/MS) could adequately distinguish between the fragments of anthocyanins and flavonols. Probe sampling, an intuitive method of sticking a probe directly to the sample, could detect anthocyanins qualitatively on a micro-area scale, such as achenes and receptacles in strawberry fruit. Our results suggest that PESI/MS/MS can be a powerful tool to characterize the profile of anthocyanins and compare their content among cultivars.

Development of a rapid, in-situ analysis method using sheath-flow probe electrospray ionisation-mass spectrometry for the direct identification of cocaine metabolites in dried blood spots

RATIONALE

Small amounts of biofluid samples are frequently found at crime scenes; however, existing gold standard methods such as LC-MS frequently require destructive extraction of the sample before a time-consuming analysis which puts strain on forensic analysis providers and can preclude further sample analysis. This study presents the application of sheath-flow probe electrospray ionization-mass spectrometry (sfPESI-MS) to the direct analysis of drug metabolites in dried blood spots (DBS) as a high throughput, minimally destructive alternative.

METHODS

A rapid direct analysis method using a sfPESI ionisation source coupled to an Orbitrap Exactive mass spectrometer was applied to detect cocaine metabolites (benzoylecgonine, BZE, cocaethylene, CE, and ecgonine methyl ester, EME) from DBS. An optimisation study exploring the use of different chemical modifiers (formic acid and sodium acetate) in the sfPESI probe extraction solvent was conducted to enhance the sensitivity and reproducibility of the sfPESI-MS method.

RESULTS

Optimisation of the extraction solvent significantly enhanced the sensitivity and reproducibility of the sfPESI-MS method. A quantitative response over a five-point calibration range 0.5 to 10 μg/ml was obtained for BZE (R²  = 0.9979) and CE (R²  = 0.9948). Limits of detection (LOD) of 1.31, 0.29 and 0.15 μg/ml were achieved for EME, BZE and CE, respectively, from 48 h aged DBSs with % RSD (relative standard deviation) across the calibration range ranging between 19%-28% for [BZE + H]⁺ , 13%-21% for [CE + H]⁺ and 12%-29% for [EME + H]⁺ .

CONCLUSIONS

A rapid (< 20 s) quantitative method for the direct analysis of cocaine metabolites from DBS which requires no prior sample preparation was developed. Although the LOD achieved for BZE (LOD: 0.29 μg/ml) was above the UK threshold limit of exposure for drug driving (0.05 μg/ml), the method may be suitable for use in identifying overdose in forensic analysis.

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.

Probe Electrospray Ionization (PESI) and Its Modified Versions: Dipping PESI (dPESI), Sheath-Flow PESI (sfPESI) and Adjustable sfPESI (ad-sfPESI)

In 2007, probe electrospray ionization/mass spectrometry (PESI/MS) was developed. In this technique, the needle is moved down along a vertical axis and the tip of the needle touched to the sample. After capturing the sample at the needle tip, the needle is then moved up and a high voltage is applied to the needle at the highest position to generate electrospray. Due to the discontinuous sampling followed by the generation of spontaneous electrospray, sequential and exhaustive electrospray takes place depending on the surface activity of the analytes. As modified versions of PESI, dipping PESI (dPESI), sheath-flow PESI (sfPESI) and adjustable sfPESI (ad-sfPESI) have been developed. These methods are complementary to each other and they can be applicable to surface and bulk analysis of various biological samples. In this article, the characteristics of these methods and their applications to real samples will be reviewed.

Investigating distributions and changes of alkaloids in living Catharanthus roseus under low-phosphorus stress using wooden-tip electrospray ionisation mass spectrometry

INTRODUCTION

Vinca alkaloids are important sources for producing anticancer drugs from Catharanthus roseus. The phosphorus of soil is one of crucial factors for planting C. roseus.

OBJECTIVES

We aim to develop an in vivo sampling technique coupled with direct mass spectrometry with wooden tip for investigating distributions and changes of alkaloids in flowers, leaves, stems, veins and roots of living C. roseus under low-phosphorus stress.

MATERIALS AND METHODS

Living C. roseus were prepared under low-phosphorus stress (n = 10) and control conditions (n = 10). Wooden-tip electrospray ionisation mass spectrometry and conventional liquid chromatography-mass spectrometry were applied to analyse living C. roseus and extracts of C. roseus, respectively.

RESULTS

Distributions and changes of serpentine, vindoline, catharanthine, and anhydrovinblastine in living C. roseus under low-phosphorus stress and control conditions were successfully obtained.

CONCLUSION

Compared to control soil conditions, low-phosphorus soil was found to induce C. roseus to generate more serpentine but less catharanthine and vindoline in leaves, veins, stems and roots, and to generate more anhydrovinblastine in flowers, leaves, stems and roots. Overall, our results showed a simple, rapid, and effective method for in vivo sampling and direct analysis of living plants.

Robotic sheath-flow probe electrospray ionization/mass spectrometry (sfPESI/MS): development of a touch sensor for samples in a multiwell plastic plate

In the previous work, sheath-flow probe electrospray ionization (sfPESI) equipped with a touch sensor was developed for conducting samples. In this work, a capacitiance-sensitive touch sensor that can be applicable to samples prepared in a nonconducting plastic multiwell plate was developed. The radiofrequency with 5 kHz and 4.5 Vpp was applied to the metal substrate on which the plastic plate was placed. The probe tip stopped at the position where it touched the surface of the liquid solution prepared in the plastic multiwell plate by detecting the displacement current flowing through the capacitance of the circuit. By coupling a nondisposable sfPESI probe with a table-top 3-axis robot, consecutive analysis of peptides, proteins, drugs, and real samples was performed. The carry-over by the consecutive analyses was suppressed to minimal by cleansing the probe tip using the solvent of water/methanol/acetonitrile (1/1/1).

Point Analysis of Foods by Sheath-Flow Probe Electrospray Ionization/Mass Spectrometry (sfPESI/MS) Coupled with a Touch Sensor

For quick, noninvasive, and high-sensitivity surface analysis of foods and agricultural products, a touch sensor was developed and applied to sheath-flow probe electrospray ionization/mass spectrometry (sfPESI/MS). Upon making contact with the sample, the probe stopped by detecting the current flowing through the circuit and analytes on the sample surface were extracted in the solvent preloaded in the plastic capillary. By lifting up the probe to the default position, an electrospray ionization mass spectrum of the sample was obtained. By scanning the sample stage using a programming tool, a point analysis of targeted positions of biological samples with a spot diameter of ≤0.3 mm was achieved. It took less than 10 s for one sample spot. This method was applied to various plants and animal tissues.