Preparation of standard VOC mixtures for climate monitoring

Sassi, Guido; Demichelis, Alessia; Lecuna, Maricarmen; Sassi, Maria Paola

doi:10.1080/03067319.2015.1016015

Cited by 8 publications

(10 citation statements)

References 11 publications

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Section: Introductionmentioning

confidence: 99%

“…The measurements of volatile organic compounds (VOCs) at trace level have a major role in atmospheric chemistry, health, ultra-clean industrial processes, indoor air quality, and metrology [1,2]. In all these applications, measurements of VOCs amount of substance require a challenging target accuracy at the level of pmol mol −1 (ppt) and nmol mol −1 (ppb) [1]. VOCs' monitoring within 1-1000 ppb range is required for the atmosphere and indoor air quality at an uncertainty of 5% for different VOCs and 3% for different fluorinate volatile compounds [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

“…The impact of the gas-wall interactions on VOCs' measurements in sampling lines has been recently under study [1,5,20,22,31,[47][48][49][50], but results are still limited. Teflon, polymeric material, coated and uncoated steel, glass, and aluminum have been considered.…”

Section: Introductionmentioning

confidence: 99%

“…Quantification of losses aimed to correct a bias in VOC measurement has not yet been proposed, to this aim, a correction has to be quantified with a proper target accuracy. Simplified conservative quantification of the losses due to gas-wall interactions in the sampling lines has been proposed, it is based on the value of an equilibrium amount of VOC adsorbed on the pipe wall [1]. A quantification of equilibrium amount segregated on the material surface is available from theoretical insight and models for few types of wall materials [30].…”

Section: Introductionmentioning

confidence: 99%

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Reproducibility of the Quantification of Reversible Wall Interactions in VOC Sampling Lines

2021

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Volatile Organic Compounds (VOCs) are widely measured at ppb and ppt level in many contexts, from therapeutic drug control in respiratory diseases to monitoring of climate change and indoor air quality. The need for accuracy is a common denominator in all these fields. The interactions between gas mixtures and solid surfaces in sampling lines and instruments play an important role in calculating the total uncertainty of the amount of VOC. The amount of substances in the gas mixture is affected by its reversible and irreversible interactions with the sampling line. The main aim of this paper is to propose and discuss a method to quantify the amount of substance segregated by reversible interactions on sampling lines. To validate the proposed method, the areic amount of a VOC (Acetone) is measured for a commercial test pipe (Sulfinert®) as the amount of substance per unit area of the internal surface of the test pipe segregated from the flowing gas mixture. Stainless steel coated by Sulfinert® was chosen as a test material because of its wide use and its limited irreversible and permeation effects. A certified gas mixture of Acetone in air with a nominal mole fraction of 10 µmol mol−1 was used for validation. Broad temperature control was used and the sensibility of the method to the temperature and the pressure has been evaluated to correct the bias due to physical condition. The sensitivity to the residence time and the Reynolds number of the gas flow has been evaluated to verify the reaching of equilibrium and the limits of the applicability of the method. The areic amount of Acetone at equilibrium on Sulfinert® coated pipe was measured as 40 nmol m−2, and an equilibrium constant value of around 0.2 m was calculated as the ratio between the superficial amount segregated on the wall and the amount concentration of Acetone in the mixture, both at the equilibrium. The observed reproducibility was better than 2.5%. This method is aimed to investigate VOC losses due to interactions for many VOC/material systems at a lower amount of substance levels.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reproducibility of the Quantification of Reversible Wall Interactions in VOC Sampling Lines

2021

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“…Uncertainty accounts for other sources generally negligible, e.g. wall adsorption effects, gas leakages from line-ups and gas mixing after connections [7,13].…”

Section: Introductionmentioning

confidence: 99%

Molar fraction stability in dynamic preparation of reference trace gas mixtures

Demichelis¹,

Sassi

Lecuna

et al. 2016

IET Science, Measurement & Technology

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Volatile Organic Compounds (VOC) at trace level are common indicators for climate change and ambient air quality. The calibration of detection systems at trace level needs VOC mixtures at nmol/mol level with 5% uncertainty, the dynamic preparation can fulfil it. A source of uncertainty for dynamic generation is the stability of the VOC molar fraction averaged on the sampling time. A general method for the calculation of the relevance of the stability contribution to the total uncertainty is here proposed. VOC molar fraction is here considered as a composed quantity. Threshold values for stability contribution were set to consider it either as negligible and relevant. The stability of the operative quantities of a device, for the dynamic preparation of accurate VOC reference mixtures, was measured at the working conditions by the Allan deviation algorithm. Stabilities of operative quantities were composed to calculate the VOC molar fraction stability and their contribution to total uncertainty of VOC molar fraction. The stability of the air inlet pressure gave the main stability contribution. The stability contribution to the total uncertainty resulted to be negligible for observation times below 60 min for VOC molar fraction uncertainty of 2% at 30 nmol/mol level

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

et al. 2018

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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.

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Preparation of standard VOC mixtures for climate monitoring

Cited by 8 publications

References 11 publications

Reproducibility of the Quantification of Reversible Wall Interactions in VOC Sampling Lines

Reproducibility of the Quantification of Reversible Wall Interactions in VOC Sampling Lines

Molar fraction stability in dynamic preparation of reference trace gas mixtures

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

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