Robotized Noncontact Open-Space Mapping of Volatile Organic Compounds Emanating from Solid Specimens

Abstract

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.

Mass Specthoscope: A Hand-held Extendable Probe for Localized Noninvasive Sampling of Skin Volatome for Online Analysis

“…It should be noted that the armpit region provides a favorable environment for bacterial growth . These two compounds were previously detected during skin/sweat VOC analyses. ,, We also detected other endogenous compounds: butanol, acetone, propionic acid, butyric acid, capric acid, and pentadecanoic acid (Table S8). Their presence on the skin is expected based on the previous reports. ,, …”

“…It is interesting to compare the proposed technique with other techniques used for the analysis of surface VOCs in terms of sensitivity (Table S4). For example, the LOD for benzaldehyde obtained with the Mass Specthoscope (3.79 × 10 –5 mol m –2 ) was lower than the LOD obtained with PENVOC (2.68 × 10 –4 mol m –2 ) . Some other techniques provide LODs in the pg and ppb range but require tedious sampling and preconcentration.…”

“…The efficacy of employing a hand-held aspirating probe for the sampling and transfer of concentrated VOCs to an ion-mobility spectrometry analyzer has been demonstrated in previous studies. , Another study demonstrated a vending-machine-style device that employs a robotic arm to sample analytes from the skin using hydrogel probes . A robotized probe was also coupled with MS for chemical mapping of VOCs in solid specimens …”

Automation and Computerization of (Bio)sensing Systems

“…Nevertheless, this process does not provide spatial resolution and is also labor-intensive. To analyze the VOCs emanating from solid specimens, Abu Bakar et al developed a robotic arm-based open-space sampling method . In this methodology, a vacuum-assisted suction sampling probe is affixed to the robotic arm, which subsequently maneuvers the probe to conduct scans of the flat surface samples.…”

Vending-Machine-Style Skin Excretion Sensing

“…Moreover, the automated systems that possess machine learning capabilities have been employed to accelerate the discovery and development of novel materials. , Robots play an important role in laboratory automation . Different types of robotic systems are designed to automate a variety of laboratory procedures, such as chemical synthesis, , microbial culture-based testing, solvent-based extraction, sample preparation, and delivery, − as well as sampling and chemical imaging with MS − to name a few. Furthermore, the available inexpensive electronic modulessuch as microcontroller boards and single-board computers (SBCs)allow chemists to automate specific tasks in the laboratory on their own by customizing the existing experimental systems. − They can be readily handled by junior researchers and students who do not have background in engineering.…”