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Webinar: Direct, Real-Time Fenceline Monitoring Using Time-of-Flight Mass Spectrometry

Environmental Monitoring Webinar


Gaseous emissions can negatively affect human health and are a major contributor to poor air quality in many regions. Ambient air pollutant sources include stack emissions and fugitive emissions during storage, processing, and transport from different industries, including those produced by oil and gas refineries and petrochemical plants. To protect workers and neighboring communities, many countries have established environmental protection regulations for critical pollutants. Regulatory methods include fenceline monitoring, air toxic analysis, and mobile air quality monitoring. For example, the US EPA rule 40 CFR part 63 requires refineries to monitor benzene emissions at key emission sources within their facilities and at their fencelines. Other examples, such as Saudi Green and Middle East Green Initiative, are focusing on reducing air pollutant emissions (e.g., 30% methane emissions reduction) by bringing together environmental protection regulations and air monitoring.

In this webinar, we discuss TOFWERK’s mobile time-of-flight mass spectrometers (TOFMS) which provide a real-time, state-of-the-art solution for online VOC and odorous compound analysis. This solution requires no sample preparation or GC separation, providing fast, real-time data output. This data helps regulatory agencies more accurately measure and inventory emissions, and effectively enforce air quality standards.

Key Discussion Points

  1. Time-of-flight mass spectrometry technology overview
  2. Environmental monitoring case studies from US, China, and Europe
  3. Features of the Vocus CI-TOF mass spectrometer that enable fast and continuous environmental measurements, including fenceline, air toxics and air quality monitoring

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Webinar Q&A

What are some of the advantages of the Vocus compared to traditional GC methodology in the context of air monitoring?
Gas chromatographs requires preconcentration followed by separation. This process is fairly slow, on the order of tens of minutes, resulting in slow time resolution. In comparison, the Vocus can directly measure VOCs in air with speed up to 10Hz. Additionally, GC requires calibration for each measured chemical species – the Vocus automatically estimates sensitivity for each detected species.

Can the Vocus be connected to all types of GC? Or only for gases and VOCs?
Yes. The Vocus is fundamentally compatible with all GCs. It can be used as a GC detector and switch between both direct measurement and separation (GC). The mechanical changes to the GC are minimal and are dependent on the GC model. The Vocus has a 1/16” inlet on its side which simplifies GC connection.

For stationary fenceline monitoring methods, the use of a long sampling line is often required. Is there a unique benefit gained from the use of the Vocus for this application?
A long sampling line is not recommended. All volatile species in the gas phase will interact with the line’s surfaces resulting in chemical losses and a slow response time. The extent of this loss will depend on the chemical characteristics of the volatile species. This is a fundamental limitation of measuring ambient air through long tubing, regardless of the detector used. We always recommend using short sample lines with direct analysis using mobile instruments for fenceline monitoring around the perimeter of a facility. If longer inlet lines are necessary, an inlet pump can be installed on the Vocus, paired with a larger diameter line for a higher flow rate.

Local Saudi authorities are asking us to provide fenceline monitoring for BTX and NMHC with 4 sampling points to cover a plant. How many analyzers should we have to connect these 4 sampling points?
It depends on how often you need to produce each measurement. If you need measurements second-by-second or minute-by-minute, you will need an analyzer at each sampling point. If you need a measurement every 15 minutes, you can accomplish this with a mobile monitoring lab that circles the facility. For this, we would recommend using our smallest Vocus model, the Elf. It is well suited for measuring BTX. 

What variety of target compounds can be analyzed by the Vocus?
The Vocus PTR reactor with its standard H3O+ ionization, provides measurement for a broad range of volatile compounds, from aromatic hydrocarbons to small, oxygenated organics. The Vocus offers additional ionization schemes which are more specific to other molecules, such as oxidized organics or ammonia.

Is the Vocus CI-TOF method for analysis recognized by any regulatory agencies? Are results legally defensible in the face of objections?
It is not currently recognized as a standard method – we are not currently recognized in the ISO standards – yet there has been some work on this over the past year with lots of work to be done. We are sending more and more instruments into standard development laboratories where demonstrations and understanding of the technology is growing, but these developments are ongoing. So far, we have yet to experience any objections to the results of Vocus measurements – in most circumstances, the results have been welcomed due the additional insight this analysis brings.

Based on atomic mass number, how many compounds can be detected and how can we distinguish them?  
Time-of-flight mass spectrometry is not limited by mass range; it is primarily limited by compound volatility (required to be present in the gas phase) and by the means which they are ionized (required to interact with the selected reagent ion). With PTR chemistry, hundreds to thousands of compounds can be detected. We can assign the molecular formula to detected ions based on the mass of the measured compounds.

How many running test hours are required? How is the Vocus calibrated and how often?
There are 2 required calibrations: mass calibration and sensitivity calibration. These calibrations can be set to automatic schedules. We recommend calibration at least once a day. All calibration settings are provided by the software and is easily customizable. Mass calibration and sensitivity calibration each take about 1 minute to complete and are fully automated.

What are the power requirements and required power source for operation? What are the requirements for remote operation?
The highest performing model requires 600W at most, with a single electric cable. Remote operation uses TeamViewer via a remote desktop connection. TOFWERK software, TWeb, runs on a web interface; if you are on the same network as the instrument, you can connect directly with a web browser.

Is there a built-in compound library?
Yes. In most environmental monitoring applications, we are using PTR ionization which we have produced extensive libraries for.

What are the environmental requirements for operation; specifically, related to 55° C temperature and 95% humidity?
Recommended operation lies between 20-25° C for optimal operation. For higher temperatures, air conditioning is recommend for a mobile or stationary laboratory. Safe operating temperatures are from 10-30° C, however, operators should be aware that large temperature fluctuations can affect the results.  

Do you have any experience selling instruments into climate zones with high temperatures and high humidity?
We have had instruments placed in Singapore and Oman without perfect environmental conditions. We cannot recommend operation at such conditions, but the instruments are designed to endure challenging environments. 

Webinar Presenter

real-time breath analysis

Dr. Veronika Pospisilova is an Application Scientist at TOFWERK in Thun, Switzerland.  She is an analytical chemist with a background in atmospheric chemistry and state-of-the art mass spectrometry for chemical analysis of aerosols. Her current research focus is the development of chemical ionization instrumentation for real-time measurement of volatile organic compounds.