Stefan Persijn

• PhD
• Researcher at VSL - National Metrology Institute

To establish robust calibration and measurement capabilities (CMCs) for atmospheric methane (CH4) stable isotope ratios, National Metrology Institutes (NMIs) and Designated Institutes (DIs) need a comprehensive understanding of the underlying measurement techniques, reference materials (RMs), calibration hierarchies, value assignment, uncertainty e...

Volatile organic compounds (VOCs) have a large impact on the oxidising capacity of the troposphere and are major precursors of tropospheric ozone and secondary atmospheric aerosols. Accurate measurements and data comparability of VOCs among monitoring networks are essential to assessing the trends of these secondary air pollutants. Metrological tra...

Volatile organic compounds (VOCs) have a large impact on the oxidising capacity of the troposphere and are major precursors of tropospheric ozone and secondary atmospheric aerosols. Accurate measurements and data comparability of VOCs among monitoring networks are essential to assess the trends of these secondary air pollutants. Metrological tracea...

The preparation of calibration gas mixtures in high pressure cylinders using the gravimetric method (ISO6142-1) has enabled the production of a wide range of mixtures down to the pmol/mol level with low uncertainties reaching 0.01% relative and beyond. This static method has limited use however for reactive components that adsorb on the cylinder wa...

Overview of the developed laser spectrometers at VSL and a description of a number of applications.

Main text The key comparison CCQM-K68.2019 was aimed at evaluating the level of comparability of laboratories' capabilities for preparing nitrous oxide in air primary reference mixtures at ambient amount fractions, in the range 320 nmol mol ⁻¹ to 350 nmol mol ⁻¹ . The comparison was coordinated by the BIPM and the KRISS. It consisted in the simulta...

Main text The CCQM-P172 comparison was designed to evaluate the level of compatibility of laboratories' spectroscopic methods for trace gas quantification using nitric acid (HNO 3 ) as a model system. Because it is present in NO 2 gas standards as an impurity, HNO 3 was chosen as the analyte for study. As primary reference gas mixtures of HNO 3 /N...

Novel traceable analytical methods and reference gas standards were developed for the detection of trace-level ammonia in biogas and biomethane. This work focused on an ammonia amount fraction at an upper limit level of 10 mg m-3 (corresponding to approximately 14 μmol mol-1) specified in EN 16723-1:2016. The application of spectroscopic analytical...

Main text The CCQM-K74.2018 comparison evaluated the level of compatibility of nitrogen dioxide (NO 2 ) in nitrogen standards at nominal amount fractions of 10 μmol/mol provided by National Metrology Institutes. Fourteen laboratories participated in the comparison, submitting two standards each, with comparative measurements and comparison coordina...

Gaseous hydrogen for fuel cell electric vehicles must meet quality standards such as ISO 14687:2019 which contains maximal control thresholds for several impurities which could damage the fuel cells or the infrastructure. A review of analytical techniques for impurities analysis has already been carried out by Murugan et al. in 2014. Similarly, thi...

Biomethane is a renewable energy gas with great potential to contribute to the diversification and greening of the natural gas supply. Ideally, biomethane can directly be injected into the natural gas grid system. For grid injection, specifications such as those in EN 16723-1 shall be met. One of the impurities to be monitored is hydrogen chloride...

Isotope ratio measurements and scale definitions are typically related to mass specectroscopy. This work discusses the challenges of optical isotope ratio spectroscopy and its prospects to significantly complement isotope ratio mass spectrometry.

Metrological services from National Metrology Institutes related to energy gases have been supported by the programme of key comparisons of the Gas Analysis Working Group of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology since its conception in 1993. Most of the key comparisons have been performed on natural...

A novel gas sensor based on multi-layered graphene (MLG) functionalised with gold nanoparticles (Au-NPs) is presented. We demonstrate for the first time that: (1) the signal saturates during the analyte exposure, something which does not occur in the pristine material and in graphene-based gas sensors in general; (2) the sign of the device current...

The MetAMCII project was established to develop a robust measurement infrastructure for key AMC species such as HCl at those trace concentrations found in cleanroom fabrication environments. This involves development of sensitive and traceable detection methods, low uncertainty static and dynamic reference materials to validate the optical detectio...

Hydrogen fuelled vehicles can play a key role in the decarbonisation of transport and reducing emissions. To ensure the durability of fuel cells, a specification has been developed (ISO 14687), setting upper limits to the amount fraction of a series of impurities. Demonstrating conformity with this standard requires demonstrating by measurement tha...

Standards ISO14687 and EN17124 set stringent limits for numerous gaseous impurities and particulates that may damage the fuel cell system in a hydrogen vehicle, as it is highly sensitive to the presence of even very low levels of impurities. However, performing the whole set of analyses is both technically challenging and time-consuming for any lab...

The absence of contaminants in the hydrogen delivered at the hydrogen refuelling station is critical to ensure the length life of FCEV. Hydrogen quality has to be ensured according to the two international standards ISO 14687–2:2012 and ISO/DIS 19880-8. Amount fraction of contaminants from the two hydrogen production processes steam methane reformi...

First analysis campaign at the European level on hydrogen quality. The results of this study come under an European metrology project that contributes to standards revision on hydrogen to promote electric mobility.

To facilitate the use of biomethane in existing transmission and distribution infrastructures, CEN/TC 408 developed specifications (EN 16723) for injecting biomethane into the natural gas grids and using it as a transport fuel. Currently, the test methods cited in EN 16723 lack metrological aspects and have not been specifically developed for biome...

Accurate measurements of line strengths and air-broadening coefficients for 10 lines of ¹²CH4 mostly from the band (2ν2 + ν3) and 2 lines of ¹³CH4 from the band (2ν3) around 1.66 µm were performed using cavity ring down spectroscopy. Spectra of mixtures of ¹²CH4 in air and ¹³CH4 in air with well-defined mole fractions of methane were recorded at pr...

The effect of moisture on the adsorption of ammonia was systematically studied using different surface materials and humidity levels. The experimental water amount fractions varied between 6 and 18,000 µmol mol⁻¹, and the ammonia amount fraction was 400 nmol mol⁻¹. The investigated materials included plain 316L stainless steel and stainless steel c...

Biogas has a vital role in the future market of renewable energy. When upgraded to biomethane, it can be injected into natural gas grids if the level of certain impurities complies with the specifications in EN16723. For some of these impurities, suitable measurement methods are lacking which hampers the quality control of biomethane to be injected...

The shortwave infrared (SWIR) spectrometer module of the Tropospheric Monitoring Instrument (TROPOMI), on board the ESA Copernicus Sentinel-5 Precursor satellite, is used to measure atmospheric CO and methane columns. For this purpose, calibrated radiance measurements are needed that are minimally contaminated by instrumental stray light. Therefore...

The Tropospheric Monitoring Instrument (TROPOMI) is the single instrument on board the ESA Copernicus Sentinel-5 Precursor satellite. TROPOMI is a nadir-viewing imaging spectrometer with bands in the ultraviolet and visible, the near infrared and the shortwave infrared (SWIR). An accurate instrument spectral response function (ISRF) is required in...

Air quality observations are performed globally to monitor the status of the atmosphere and its level of pollution and to assess mitigation strategies. Regulations of air quality monitoring programmes in various countries demand high-precision measurements for harmful substances often at low trace concentrations. These requirements can only be achi...

Preparation of accurate reference gas standards at low amount fractions such as for greenhouse gases requires highly sensitive instrumentation to determine the purity of the gases used in the preparation. For this purpose, a versatile CRDS spectrometer has been constructed at VSL based on high-power, continuous wave OPOs covering a very wide wavele...

A photoacoustic (PA) sensor for fast and real-time gas sensing is demonstrated. The PA sensor is a stand-alone system controlled by a field-programmable gate array. The PA cell has been designed for flow noise immunity using computational fluid dynamics (CFD) analysis. The aim of the CFD analysis was to investigate and minimize the influence of the...

A photoacoustic (PA) sensor for fast and real-time gas sensing is demonstrated. The PA sensor is a standalone system controlled by a Field-Programmable Gate Array (FPGA). The PA cell has been designed for flow noise immunity using computational fluid dynamics (CFD) analysis. The aim of the CFD analysis was to investigate and minimize the influence...

The short-wave infrared (SWIR) spectrometer module of the Tropospheric Monitoring Instrument (TROPOMI), on board the ESA Copernicus Sentinel-5 Precursor satellite, is used to measure atmospheric CO and methane columns. For this, calibrated radiance measurements are needed in which the stray light is reduced strongly. Therefore, a method has been de...

The Tropospheric Monitoring Instrument (TROPOMI) is the single instrument on board of the ESA Copernicus Sentinel-5 Precursor satellite. TROPOMI is a nadir-viewing imaging spectrometer with bands in the ultraviolet and visible, the near infrared and the short-wave infrared (SWIR). An accurate instrument spectral response function (ISRF) is required...

Air quality observations are performed globally to monitor the status of the atmosphere, its level of pollution and to assess mitigation strategies. Regulations of air quality monitoring programmes in various countries demand high precision measurements for harmful substances often at low trace concentrations. These requirements can only be achieve...

Accurate intensity measurements were performed for several lines of the two main isotopologues of carbon dioxide, using cavity ring down spectroscopy. Absorption spectra of the R52e line at 6112.8902 cm⁻¹ (30014←00001 band) of ¹²CO2 and the P6e line at 6114.8580 cm⁻¹ (30013←00001 band) of ¹³CO2 were recorded at pressures between 15 and 50 mbar at 2...

The KEY-VOCs project is a EURAMET joint research project focused on key Volatile Organic Compounds (VOCs) in air. One of its activities is the evaluation of sensors-based measurement systems. In Europe, the monitoring of benzene in ambient air is mandatory as set by the European Directive for air quality (AQD) [1]. This Directive states that the re...

This article presents a literature review of sensors for the monitoring of benzene in ambient air and other volatile organic compounds. Combined with information provided by stakeholders, manufacturers and literature, the review considers commercially available sensors, including PID-based sensors, semiconductor (resistive gas sensors) and portable...

Methods for the hydrogen impurity analysis are listed in this report to enable the simultaneous analysis as best as possible of compounds mentioned in ISO 14687-2:2012. Performance characteristics of the methods are also mentioned. Only validated offline purity analysis methods are taken into account in this report. This report aims at answering th...

Absorption spectroscopy on CO2 for the determination of gas temperature is reported. Direct absorption of a frequency comb laser through a gas cell at atmospheric conditions is analysed with a virtually imaged phased array spectrometer. Several measurement and analysis techniques are investigated to find the parameters most sensitive to changes in...

We demonstrate an online (in-situ) sensor for continuous detection of oil contamination in compressed air systems complying with the ISO-8573 standard. The sensor is based on the photo-acoustic (PA) effect. The online and real-time PA sensor system has the potential to benefit a wide range of users that require high purity compressed air. Among the...

The CCQM-K90 comparison is designed to evaluate the level of comparability of national metrology institutes (NMI) or designated institutes (DI) measurement capabilities for formaldehyde in nitrogen at a nominal mole fraction of 2 μmol mol⁻¹. The comparison was organised by the BIPM using a suite of gas mixtures prepared by a producer of specialty c...

We demonstrate an online (in-situ) sensor for continuous detection of oil contamination in compressed air systems complying with the ISO-8573 standard. The sensor is based on the photo-acoustic (PA) effect. The online and real-time PA sensor system has the potential to benefit a wide range of users that require high purity compressed air. Among the...

The environmental impacts of ammonia (NH3) in ambient air have become more evident in the recent decades, leading to intensifying research in this field. A number of novel analytical techniques and monitoring instruments have been developed, and the quality and availability of reference gas mixtures used for the calibration of measuring instruments...

The environmental impacts of ammonia (NH$_3$) in ambient air have become more evident in the recent decades, leading to intensifying research in this field. A number of novel analytical techniques and monitoring instruments have been developed, and the quality and availability of reference gas mixtures used for the calibration of measuring instrume...

High purity nitrogen or air, often referred to as zero gas, is essential for calibrating instrumentation used in a wide variety of measurements, such as air quality monitoring. Providing traceable and accurate quantification of impurities of the target component in zero gas is a major challenge, as the detection limits of appropriate analytical tec...

In order to calibrate volatile organic compounds (VOC) measurement systems high concentrated gas standards are dynamically diluted with a zero gas (nitrogen or air). Within the framework of the European KEY-VOCs project, gas purifiers were tested to remove residual VOC impurities which could bias the prepared calibration standard. The testing inclu...

Measuring ammonia in ambient air is a sensitive and priority issue due to its harmful effects on human health and ecosystems. The European Directive 2001/81/EC on " National Emission Ceilings for Certain Atmospheric Pollutants (NEC) " regulates ammonia emissions in the member states. However, there is a lack of regulation to ensure reliable ammonia...

Adsorption of dynamically diluted ammonia at part-per-billion to low part-per-million concentrations in dry nitrogen was studied with treated and non-treated stainless steel and polymer test tubes. The treatments included electropolishing and two types of coatings based on amorphous silicon. Cavity ring-down spectroscopy with an external cavity dio...

An instrument achieving 100 KHz spectral precision using multiple correlation Fourier transform spectroscopy has been demonstrated. The instrument can measure the individual frequency comb modes of 100 MHz frequency comb lasers in air. The experiments show ∼400,000 resolved modes at linewidths of 85 MHz in the region of 829 nm and ∼ 182,000 resolve...

Over the past 10 years, with the advent of new crystals designs and a new generation of pump lasers, continuous-wave (cw) optical parametric oscillators (OPOs) have developed into mature monochromatic light sources. Nowadays, cw OPOs can fulfill a wide variety of criteria for sensitive molecular gas sens-ing. It can access the mid-infrared waveleng...

Abstract Over the past 10 years, with the advent of new crystals designs and a new generation of pump lasers, continuous-wave (cw) optical parametric oscillators (OPOs) have developed into mature monochromatic light sources. Nowadays, cw OPOs can fulfill a wide variety of criteria for sensitive molecular gas sensing. It can access the mid-infrared...

Background and aims After a series of seminal works during the last decade of the 20th century, nitric oxide (NO) is now firmly placed in the pantheon of plant signals. Nitric oxide acts in plant–microbe interactions, responses to abiotic stress, stomatal regulation and a range of developmental processes. By considering the recent advances in plant...

This supplementary comparison (EURAMET.QM-S8) concerns the purity analysis of nitrogen as used in reference gas mixture preparation. This project was carried out without adding impurities to the gas used for this comparison, and is therefore more representative to evaluate the analysis of carbon monoxide, carbon dioxide, methane, oxygen, argon and...

Different forms of nitrogen (N) fertilizer affect disease development; however, this study investigated the effects of N forms on the hypersensitivity response (HR)—a pathogen-elicited cell death linked to resistance. HR-eliciting Pseudomonas syringae pv. phaseolicola was infiltrated into leaves of tobacco fed with either or . The speed of cell dea...

We demonstrate a new technique for absolute distance measurement with a femtosecond frequency comb laser, based on unraveling the output of an interferometer to distinct comb modes with 1 GHz spacing. From the fringe patterns that are captured with a camera, a distance is derived by combining spectral and homodyne interferometry, exploiting about 9...

This key comparison was performed to demonstrate the capability of NMIs to analyse the purity of methane for use as a source gas in the preparation of standard gas mixtures. This capability is an essential requirement for the preparation of accurate standards of natural gas and some other fuels. Since it is difficult to carry out a comparison with...

Laser-spectrometric methods to derive absolute and traceable carbon monoxide (CO) amount fractions in exhaled human breath could be of advantage for early disease detection as well as for treatment monitoring. As proof-of-principle laboratory experiment, we employed intra-pulse and continuous wave (cw) quantum cascade laser spectroscopy (QCLAS), bo...

A Cavity-Enhanced Direct Frequency Comb Spectroscopy (CE-DFCS) setup developed in our laboratory is described. We focus on the broadband spectrometer which is based on a Virtually Imaged Phased Array (VIPA). It can detect 3500 independent channels simultaneously, covering a bandwidth of 20 nm with a resolution of 800 MHz around a central frequency...

We present a Fourier Transform Infrared spectrometer for use with a frequency comb laser as source. The spectrometer can completely resolve the modes of the frequency comb at 100 MHz.

A fiber-amplified Distributed Bragg Reflector diode laser is used to pump a continuous wave, singly resonant Optical Parametric Oscillator (OPO). The output radiation covers the 3–4 μm with ability of rapid (100 THz/s) and broad mode-hop-free tuning (5 cm−1). Wavelength Modulation Spectroscopy is combined with the OPO to take optimal advantage of t...

After a short introduction and description of particular features of the equipment used, attention is centered on applications. Solids, surfaces, and solutions have been studied by photoacoustic (PA) spectroscopy; recent work is quoted. Gas-phase investigations are discussed with emphasis on trace gas detection. Especially, applications in biology...

Aversatile OPO-based cavity ringdown spectrometer is reported for quantitative and sensitive gas measurement down tonmol/mol levels. The system is based on cavity ringdown spectroscopy (CRDS) in combination with a continuous wave optical parametric oscillator tunable from 2693 to 3505nm. Using a single set of CRDS mirrors, spectra were recorded of...

Infrared gas phase spectroscopy is becoming very common in many life science applications. Here we present three types of trace gas detection systems based on CO2 laser and continuous wave (cw) optical parametric oscillator (OPO) in combination with photoacoustic spectroscopy and cw quantum cascade laser (QCL) in combination with wavelength modulat...

A singly resonant continuous-wave optical parametric oscillator (cw OPO) is described. The OPO contains no intracavity etalon, which makes its wavelength tuning simple and straightforward, including only temperature tuning of the nonlinear crystal and wavelength tuning of the pump laser. The OPO provides watt-level output in the mid-infrared region...

Stability and tuning characteristics of continuous-wave optical parametric oscillators (CW OPOs) are affected by various thermal effects arising from optical absorption in nonlinear crystals. In this paper, we present an experimental study of such effects in a singly resonant CW OPO. The OPO operates in the 3-μm mid-infrared region and it is based...

Nowadays, worldwide developments of new cw OPO devices realize widely tunable, cw radiation with high power and narrow linewidth. Here, the versatility and sensitivity of continuous wave, singly resonant OPO’s combined with photoacoustic and cavity ring-down spectroscopy are discussed for trace gas sensing. Keywords: Optical parametric oscillator,...

We report on recent progress on continuous-wave quantum cascade laser (QCL)-based spectrometer using wavelength modulation for detection of nitric oxide (NO) and carbon dioxide in breath. Comparison is made with a standard chemiluminescence instrument. Article not available.

We report on recent progress on continuous-wave quantum cascade laser (QCL)-based spectrometer using wavelength modulation for detection of nitric oxide (NO) and carbon dioxide in breath. Comparison is made with a standard chemiluminescence instrument. Article not available.

A continuous wave optical parametric oscillator, generating up to 300mW idler output in the 3–4μm wavelength region, and pumped by a fiber-amplified DBR diode laser is used for trace gas detection by means of quartz-enhanced photoacoustic spectroscopy (QEPAS). Mode-hop-free tuning of the OPO output over 5.2cm-1 and continuous spectral coverage exce...

Nitrogenase activity, indicative of N2 fixation, was measured in the surface waters along a north–south transect in the eastern Atlantic Ocean, from Texel (The Netherlands, 53°N) to Cape Town (South Africa, 35°S) using a sensitive on-line, near real-time acetylene reduction assay. From the beginning of January to the end of February 2000 nitrogenas...

An 800 mW, fast scanning (100 THz/s), continuous wave optical parametric oscillator (3-4 mum) pumped by a fibre-amplified diode laser is used for sensitive (1.5 times 10-8 cm-1 Hz-1/2), multi-component trace gas detection.

We present a novel approach to trace gas detection of more complex molecules, based upon a combination of continuous cavity ringdown spectroscopy using a cw infrared OPO system and supersonic planar jet.

The relationship between ethylene production and both seed dormancy and germination was investigated using red rice (weedy rice) as a model species. Both fully dormant and after-ripened (non-dormant) naked caryopses were incubated with or without inhibitors of ethylene synthesis [aminoethoxyvinylglycine (AVG)] and perception [silver thiosulfate (ST...

A sensitive infrared detection scheme is presented in which continuous wave cavity ring down spectroscopy is used to record rovibra-tional spectra of molecular ions in direct absorption through supersonically expanding planar plasma. A cw optical parametric oscillator is used as a light source and combines a broad spectral coverage (2100–3600 cm À1...

The authors present a trace gas detection method for complex molecules using continuous cavity ring-down spectroscopy in combination with a continuous wave optical parametric oscillator (tunability wavelength: 2.8–4.8 μm; power: 1 W) sampling a supersonic planar jet expansion (nozzle dimension: 3 cm×80 μm). The improved molecular selectivity allows...

* The results of a single publication stating that terrestrial plants emit methane has sparked a discussion in several scientific journals, but an independent test has not yet been performed. * Here it is shown, with the use of the stable isotope (13)C and a laser-based measuring technique, that there is no evidence for substantial aerobic methane...

Although quantifying gas exchange in small insect species is of great biological interest, the progress in this field of research is hampered by the inability of most gas detectors to monitor the low emission rates from these insects. Recently, laser based photoacoustic spectroscopy (LPAS) has emerged as a highly sensitive technique that allows gas...

We present a high power, broadly tunable (2.75-3.83 mum) cw OPO based on PP-MgO-LN. Using a combination of tuning techniques, molecular absorption spectra can be continuously recorded over 450 cm-1 at Lt0.001 cm-1 resolution.

We present a high-power (2.75W), broadly tunable (2.75–3.83μm) continuous-wave optical parametric oscillator based on MgO-doped periodically poled lithium niobate. Automated tuning of the pump laser, etalon and crystal temperature results in a continuous wavelength coverage up to 450cm-1 per poling period at <5×10-4cm-1 resolution. The versatility...

CO-laser based photoacoustic detection of nitric oxide has been theoretically and experimentally investigated. Using a model based on rate equations the influence of H 2O vapor on NO relaxation was determined. In addition, NO absorption coefficients were measured and they showed a good correspondence with calculated values from Hitran database. The...

Changes in ascorbic acid content are measured in the cortex tissue of Conference pears stored at various compositions of carbon dioxide and oxygen. Enhanced carbon dioxide levels cause ascorbic acid concentrations to decline. Soon after ascorbic acid has declined below a certain value, browning of the core tissue can be observed. Reducing carbon di...

Detecting early ageing stages of seeds in storage is of great concern to vegetable seed companies. Despite their reliability conventional germination tests are destructive and time consuming. One alternative towards assessing the quality of seed is to monitor the concentration of certain volatiles (acting as biological markers) evolved from the see...