Remote sampling mass spectrometry for dry samples: Sheath-flow probe electrospray ionization (PESI) using a gel-loading tip inserted with an acupuncture needle

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.

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.

Ambient Ionization Mass Spectrometry: Application and Prospective

Mass spectrometry (MS) is a formidable analytical tool for the analysis of non-polar to polar compounds individually and/or from mixtures, providing information on the molecular weights and chemical structures of the analytes. During the last more than one-decade, ambient ionization mass spectrometry (AIMS) has developed quickly, producing a wide range of platforms and proving scientific improvements in a variety of domains, from biological imaging to quick quality control. These methods have made it possible to detect target analytes in real time without sample preparation in an open environment, and they can be connected to any MS system with an atmospheric pressure interface. They also have the ability to analyze explosives, illicit drugs, disease diagnostics, drugs in biological samples, adulterants in food and agricultural products, reaction progress, and environmental monitoring. The development of novel ambient ionization techniques, such as probe electrospray ionization, paper spray ionization, and fiber spray ionization, employed even at picolitre to femtolitre solution levels to provide femtogram to attogram levels of the target analytes. The special characteristic of this ambient ion source, which has been extensively used, is the noninvasive property of PESI of examination of biological real samples. The results in the current review supports the idea that AIMS has emerged as a pioneer in MS-based approaches and that methods will continue to be developed along with improvements to existing ones in the near future.

Direct Liquid Extraction and Ionization Techniques for Understanding Multimolecular Environments in Biological Systems (Secondary Publication)

A combination of direct liquid extraction using a small volume of solvent and electrospray ionization allows the rapid measurement of complex chemical components in biological samples and visualization of their distribution in tissue sections. This review describes the development of such techniques and their application to biological research since the first reports in the early 2000s. An overview of electrospray ionization, ion suppression in samples, and the acceleration of specific chemical reactions in charged droplets is also presented. Potential future applications for visualizing multimolecular environments in biological systems are discussed.

Enhancing Solid State LiDAR Mapping with a 2D Spinning LiDAR in Urban Scenario SLAM on Ground Vehicles

Solid-State LiDAR (SSL) takes an increasing share of the LiDAR market. Compared with traditional spinning LiDAR, SSLs are more compact, energy-efficient and cost-effective. Generally, the current study of SSL mapping is limited to adapting existing SLAM algorithms to an SSL sensor. However, compared with spinning LiDARs, SSLs are different in terms of their irregular scan patterns and limited FOV. Directly applying existing SLAM approaches on them often increase the instability of a mapping process. This study proposes a systematic design, which consists of a dual-LiDAR mapping system and a three DOF interpolated six DOF odometry. For dual-LiDAR mapping, this work uses a 2D LiDAR to enhance a 3D SSL performance on a ground vehicle platform. The proposed system takes a 2D LiDAR to preprocess the scanning field into a number of feature sections according to the curvatures on the 2D fraction. Subsequently, this section information is passed to 3D SSL for direction feature selection. Additionally, this work proposes an odometry interpolation method which uses both LiDARs to generate two separated odometries. The proposed odometry interpolation method selectively determines the appropriate odometry information to update the system state under challenging conditions. Experiments are conducted in different scenarios. The results proves that the proposed approach is able to utilise 12 times more corner features from the environment than the comparied method, thus results in a demonstrable improvement in its absolute position error.

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.

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).

Interpol review of controlled substances 2016-2019

This review paper covers the forensic-relevant literature in controlled substances from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

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.

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

In previous work, probe electrospray ionization/mass spectrometry (PESI/MS) and sheath-flow probe electrospray ionization/mass spectrometry (sfPESI/MS) were reported for the rapid and minimally invasive analysis of food. In this work, a modified version of sfPESI will be reported. The sample surface was pricked with an acupuncture needle inserted in the sfPESI probe that protruded from the terminus of the tip by 5 mm. The invasion depth of the needle into the sample was ∼1 mm. After sampling, the needle was retracted into the solvent-preloaded capillary with a protrusion length of 0.1-0.2 mm from the tip. A mass spectrum of the sample captured on the needle was obtained by applying a high voltage to the needle. This method could be applicable to profiling analyses of plants with the epicuticular wax covering on the surfaces that are difficult to analyze by sf-PESI. The on-site mass spectrometric analysis for a growing apricot in the field was performed to monitor the developing stage of the fruit.