46 Air Monitoring
Gas Chromatography: MCERTS Certification for Ambient Air Analysis on Benzene and VOCs
Due to environmental issues, the world of gas analysis is evolving very rapidly. Governments set the rules to limit and control the environmental pollution through legislation. Volatile organic compounds (VOCs), often produced by human activities, are amongst the sources of pollution that need to be identified and quantified for safety reasons. Exposure to high concentrations of certain VOCs is dangerous, even for short times, and the impact of low concentrations of VOCs on people’s health and environment has also become a major concern in recent years. The concentration of such compounds can be very different depending on the measurement area and it is a considerable technological challenge to analyse precisely and continuously the VOCs present in air within industrial walls or at the top of a mountain using the same instrument. Presently, only benzene is regulated, but there are moves to measure other VOCs which are known to be ozone precursors.
Since 1986, Chromatotec® The NPL, is known
worldwide for being at the edge of technology for air quality monitoring and type testing, performed in the laboratory and in the field.
Author Details: Franck Amiet, Chromatotec
Group President Michel Robert,
Chromatotec Analytical Service Manager
Dr Nicholas A Martin, Senior Research Scientist, Environmental
Measurements Group National Physical Laboratory, UK
15 rue d’Artiguelongue, 33240 Saint Antoine, France
Tel: +33 (0)5 57 94 06 26 Email:
info@chromatotec.com Web:
www.chromatotec.com
Chromatotec and the NPL are members of the European benzene normalization committee
has been recognised worldwide for their
accurate gas analysis, renowned for analysis in the field of ambient air monitoring and natural gas. Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analysing compounds that can be stable in the vapour state. Chromatotec’s products allow the quantification and identification of compounds over a wide range of concentrations (including ppt, ppb, ppm and % levels) using gas chromatography analysers.
In gas chromatography, the mobile phase is a carrier gas, usually an inert gas such as helium, hydrogen or an unreactive gas such as nitrogen or argon. The mobile phase carries the sample to be analysed through a column in order to separate the compounds. The time at which the compounds elute from the column is used to identify the different species whereas the electric intensity measured by the detector allows for quantification. In order to verify the quality of our instruments, Chromatotec®
has performed tests and obtained certifications relating to relevant standards, performed by bodies recognised worldwide.
Furthermore, to be compliant with European, Chinese and American performance standards, Chromatotec®
development and improvement of rapid and accurate analysers.
For Continuous Ambient Air Monitoring Systems (CAMS), the Certification Scheme called MCERTS defines tests and performance criteria for the measurement of benzene concentrations and other VOCs using an automated sampling pump with in-situ gas chromatography. There is also a harmonised European standard relating to the measurement of benzene, which is known as EN 14662-3. In the near future, Chromatotec®
will be certified ISO 17025 for measurements of benzene and certain other VOCs.
The National Physical Laboratory (NPL -London) is currently one of only a few ISO 17025 accredited European laboratories to perform benzene laboratory and field tests. The NPL in collaboration with airmotec/Chromatotec®
has worked and invested in the
performance criteria defined in the MCERTS standard for CAMS and EN 14662-3. Both types of CAMS were cyclic automated analysers which sample a known measured volume of air through a sorbent medium for a fixed period of time, and then analyse the amount of the target determinands, trapped using a gas chromatograph. One type of CAM (airmoVOC) employed a Flame Ionisation Detector (FID) to measure the determinands while the second
type of CAM (airTOXIC) used a Photo Ionisation Detector (PID).
For the laboratory tests, all four CAMS measured simultaneously from the same gas manifold and sample line. The required determinands were generated from traceable 30 component EU Directive ozone precursor mixtures diluted in nitrogen; a mixture produced by NPL using gravimetry (ISO 17025 for standard production). The parent mixtures were diluted as required in zero nitrogen or scrubbed air. The starting concentration of the determinands in the parent mixtures (before dilution), expressed in units of parts per billion, was nominally the same for all the 30 compounds.
The performance standards were specifically applicable to measurements of ambient benzene vapour in the 0 µg.m-3
to 50 µg.m-3 concentration
range (standardised at 101.3 kPa and 293 K) but the MCERTS standard could also be applied to other volatile organic compounds (VOCs) with
proposed a Laboratory and Field Test Programme
for approval to Sira Environmental Limited. Sira is the certification body which oversees the MCERTS certification on behalf of the Environment Agency which is an Executive Non-departmental Public Body responsible to the Secretary of State for Environment, Food and Rural Affairs in the UK.
To verify and ensure the accurate performance of Chromatotec’s analysers, four CAMS, using two different detector technologies, were simultaneously tested by NPL in their specialised ambient air quality test laboratory in accordance with UKAS-accredited NPL Test Procedure QPAS/B/528a (and later on in the field) and compared against the
IET Annual Buyers’ Guide 2013
www.envirotech-online.com
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