The analysis of volatile organic compounds (VOCs) normally involves sample collection, sample transfer to laboratory, sample preparation, and the chromatographic separation of analytes. However, in some cases, it is impractical or impossible to collect samples prior to the analysis, while the analysis time has to be minimized. Ion mobility spectrometry (IMS) is an ideal technique for a rapid in situ chemical analysis. Here, we present a portable cloud-integrated pen-probe analyzer based on IMS and demonstrate its applications in the analysis of VOCs emanating from surfaces. The user approaches the penprobe to a sampled surface and presses a button on the pen-probe. The analysis is then executed automatically. The VOCs are scavenged from the surface by a suction force and directed to a corona discharge atmospheric pressure chemical ionization source. The ions are separated in a drift tube according to their size and charge and then detected by a Faraday plate detector. The detector signal is amplified and digitized. The spectral data are deposited in the Internet cloud along with time and location data for further retrieval and processing. The platform incorporates a mobile Wi-Fi router for easy connectivity and a global positioning system module for geolocation. The prototype was developed using low-cost electronic modules (Arduino, Tinker Board S). It was further characterized using chemical standards. The limits of detection for pyrrolidine, 2,4-lutidine, and (−)-nicotine are 48.9, 2.30, and 416 nmol, respectively (amounts of substances placed on the sampling surface). The selected real specimens (nicotine patch, skin exposed to nicotine, fish sauce, and fried chicken) were also subjected to analysis yielding the characteristic ion mobility spectra.

We present BioChemPen, a portable wireless biosensor device for rapid analysis of substances adsorbed on solid surfaces. The device takes advantage of (bio)luminescent reactions taking place in a hydrogel matrix. In a typical embodiment, the active element of this device is a hydrogel disk (chemotransducer) containing enzyme(s), electrolyte solution, and all of the necessary substrates. When the hydrogel is exposed to a solid sample surface containing the target analyte, light is produced. A photoresistor (phototransducer), placed in close proximity to the hydrogel disk, detects the light. The operation of the BioChemPen is enabled by a MicroPython PyBoard microcontroller board and other low-cost electronic modules. The obtained results are immediately uploaded to the Internet cloud. In one application, we demonstrate an analysis of hypochlorite-containing cleaning agents present on the surfaces of daily use objects by an assay based on hydrogel embedded with luminol and hydrogen peroxide. In another application, we use hydrogel embedded with luciferin, luciferase, and pyruvate kinase to detect adenosine triphosphate (ATP), and adenosine diphosphate (ADP), and link the ATP content with meat freshness. Lastly, we demonstrate the detection of organophosphate pesticides present on vegetables with the hydrogel containing acetylcholinesterase, choline oxidase, and horseradish peroxidase. The limits of detection for sodium hypochlorite, ATP, ADP, and chlorpyrifos-methyl (a pesticide) were 7.95

Analysis of volatile organic compounds (VOCs) is normally preceded by sample homogenization and solvent extraction. This methodology does not provide spatial resolution of the analyzed VOCs in the examined matrix. Here, we present a robotized pen-shaped probe for open-space sampling and mapping of VOCs emanating from solid specimens (dubbed “PENVOC”). The system combines vacuum-assisted suction probe, mass spectrometry, and robotic handling of the probe. The VOCs are scavenged from the sample surface by a gentle hydrodynamic flow of air sustained by a vacuum pump. The sampled gas is transferred to the proximity of corona discharge in an atmospheric pressure chemical ionization source of a tandem mass spectrometer. The PENVOC has been attached to a robotic arm to enable unattended scanning of flat surfaces. The specimens can be placed away from the mass spectrometer during the scan. The robotized PENVOC has been characterized using chemical standards (benzaldehyde, limonene, 2-nonanone, and ethyl octanoate). The limits of detection are in the range from 2.33 × 10–5 to 2.68 × 10–4 mol m–2. The platform has further been used for mapping of VOCs emanating from a variety of specimens: flowers, glove exposed to smoke, fuel stains, worn medical face mask, worn clothing, cheese, ham, and fruits. The chemical maps show unique distributions of the VOCs on the scanned surfaces. Obtaining comparable results (VOC maps) using other techniques (e.g., repetitive headspace sampling prior to offline analysis) would be time-consuming. The presented mapping technique may find applications in environmental, forensic, and food science.

Skin metabolites show huge potential for use in clinical diagnostics. However, skin sampling and analysis workflows are tedious and time-consuming. Here, we demonstrate a vending-machine-style skin excretion sensing platform based on hydrogel-assisted sampling of skin metabolites. In this sensing platform, a sampling probe with hydrogel is held by a robotic arm. The robotic arm manoeuvres the probe to press it onto the forearm of a human subject. Due to the highly hydrophilic nature of the hydrogel, water-soluble metabolitesreleased by skinare collected into the hydrogel, leaving behind the nonpolar metabolites. The probe is then inserted into a custom-made open port sampling interface coupled to an electrospray ion source of a high-resolution quadrupole-time-of-flight mass spectrometer. Metabolites in the hydrogel are immediately extracted by a solvent liquid junction in the interface and analyzed using the mass spectrometer. The ion current of the target analyte is displayed on a customized graphical user interface, which can also be used to control the key components of the analytical platform. The automated sampling and analysis workflow starts after the user inserts coins or presents an insurance card, presses a button, and extends an arm on the sampling area. The platform relies on low-cost mechanical and electronic modules (a robotic arm, a single-board computer, and two microcontroller boards). The limits of detection for standard analytesarginine, citrulline, and histidineembedded in agarose gel beds were 148, 205, and 199 nM, respectively. Various low-molecular-weight metabolites from human skin have been identified with the high-resolution mass spectrometer.

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