Compact devices for generation of reference trace VOC mixtures: a new concept in assuring quality at chemical and biochemical laboratories

Abstract

Volatile organic compounds (VOCs) in gas mixtures at trace level (nmol/mol) are routinely measured by chemical and biochemical laboratories as climate indicators, indoor air quality pollutants from building materials emissions, contaminants in food and beverages, and biomarkers in body fluids (blood, urine, breath) of occupational exposure or human diseases. Current analytical instruments used for measurements are gas chromatographs equipped with various injector and detector configurations. The assurance of measurement quality is done by using a huge amount of certified liquid VOC standard solutions (or gaseous VOC standard cylinders) with multiple dilutions to reach the required trace level. This causes high standard uncertainty in instrument calibrations, high cost, and high consumption of analysis and laboratory personal time. In this paper, we present the implementation of portable generators producing VOC gas standards at trace level for automatic and direct calibration of VOC detectors employed in various contexts, removing the need for preparation of matrix calibration standards in cylinders. Two compact devices in-house developed by two national metrology institutes-the Istituto Nazionale di Ricerca Metrologica (INRIM) and the Federal Institute of Metrology (METAS)-are here used to dynamically generate reference gas mixtures in an SI traceable way. The two devices are based on different technologies: diffusion and permeation, for INRIM and METAS, respectively. A metrological characterization is given and the practical implementation at chemical and biochemical laboratories is discussed. Graphical abstract Onsite calibration with transportable generation system with similar performances to primary laboratory devices.

Supramolecular Luminescent Sensors

“…Challenges in developing methods for the detection of VOC analytes include their volatility, which makes it difficult to isolate significant quantities for analysis; the fact that they often occur as mixtures of analytes, which complicates identification of any one analyte in the mixture; and the general dearth of functional groups that provide clear spectroscopic signatures, especially for aliphatic alkanes and organic solvents. Nonetheless, a variety of detection methods have been reported in the chemical literature, , with the vast majority using gas chromatography/mass spectrometry (GC/MS) to accomplish such detection. − The use of luminescent sensors, including supramolecular luminescent sensors, − has been reported as well.…”

On-Site Detection of Volatile Organic Compounds (VOCs)

“…Most methods, however, use mass spectrometers as detectors (GC-MS). Due to the volatile and reactive nature of some VOCs, it is often difficult to obtain stable reference standards to ensure the calibration of measurements [ 24 , 25 ]. These reference standards can be generated from gas tanks or via dynamic methods [ 24 , 26 ].…”

In situ gas cell for the analysis of adsorption behavior on surfaces using x-ray spectroscopy

“…For monitoring air quality and air pollution levels of these compounds, measurements take place in ambient and indoor air, up to measuring of vertical VOC profiles in the atmosphere to better model and monitor their impact on climate. [1][2][3][4][5][6] VOC concentrations in the background atmosphere are typically in the low range of a few pmol•mol −1 to a few nmol•mol −1 and require measurement techniques with very high sensitivity that are adapted depending on the concentration and compound to be detected (Table 1 in 6 ). Gas chromatographs with flame ionisation detectors and mass spectroscopy detectors are currently the most commonly used VOC measuring instruments, but also Fourier transform infrared spectroscopy, cavity ringdown spectroscopy, portable monitors and direct sensor techniques specified for individual VOCs, e.g.…”

“…for breath analysis, are used. 1,2,[4][5][6] Good calibration standards are essential for metrological traceability and comparability.…”

“…In order to minimise the interaction with the surfaces, the state of research also includes the use of different surface treatments of the containers, gas cylinders and the components used, such as filters and pipe systems in the measurement setup. [2][3][4][5][6][7] The development of the gas cell presented here is linked to this issue. While it is interesting to understand the adsorption behavior fundamentally and quantify adsorbed material, also the adsorption mechanisms can be utilized as a means of reducing the amount of pollutants in the atmosphere.…”