Complying with EN 14662-1, the European standard method for measurement of benzene concentrations using pumped sampling followed by thermal desorption and gas chromatography.
Method EN 14662-1 is a European standard prepared by CENs Technical Committee (TC 264) on “air quality” and gives guidance on how the reader can reliably determine the concentration of benzene in ambient air. The technique used for sampling is pumped sampling onto a sorbent packed tube with analysis by thermal desorption (TD) coupled to gas chromatography (GC).
What's changed from the 2005 version of EN 14662-1?
Whilst the general methodology of EN 14662-1 is the same, the 2023 version has four technical changes to the method when compared to the 2005 edition:
- Users now have the option of using multi-tube sampling devices so that a series of samples can be collected, either in sequence and/or in parallel, without the need for user intervention.
- A specification for the requirements that these multi-tube sampling devices should meet has been included.
- EN 14662-1:2023 now includes guidance on how to calibrate using a gas standard as well as the liquid spiking method, which was previously included in the document.
- Finally, there are widespread updates to technical details within the standard to bring it in line with the latest ambient air monitoring standards, including the uncertainty calculations.
Who should use EN 14662-1?
Standards such as EN 14662-1 are invaluable for anyone who wants to reliably measure benzene in ambient air, as they provide clear advice and data quality objectives.
EN 14662-1 is the European reference method for determining benzene concentrations in air for the purpose of comparing measurements with the benzene limit values over a period of one year, but it can also be used more broadly.
EN 14662-1 was written to cover a benzene concentration range of approximately 0.5 μg/m3 to 50 μg/m3, with sampling collection over a range of times from a few hours to several days. This scope and application range means that it can be used for:
- Compliance with legislation including monitoring of the ambient atmosphere g. European Commission Air Quality Directives.
- Environmental permitting.
- Air quality reviews by local authorities.
- Emissions inventories and modelling.
- Environmental assessments for planning regulations.
- Investigation or environmental research.
Why partner with Markes for EN 14462-1?
Markes has an enviable reputation, built up over almost 30 years, for being a technology leader in the field of thermal desorption.
Markes’ specialists are actively involved various standard committees, such as CEN, ISO and ASTM. They also advise national bodies responsible for air quality monitoring on the best techniques and practice for achieving their objectives i.e. making our air cleaner and safer for all.
This sharing of technical knowledge also extends to our customers to assist with their working practices.
Additionally, Markes manufacturers and provides the complete range of thermal desorption equipment, accessories, and consumables necessary for adherence to, and effective execution of, EN 14662-1.
What equipment and materials do you need for EN 14662-1?
There are four key phases for which laboratories must be prepared: calibration, sampler preparation, sampling and analysis:
1. Calibration
Accurate calibration can significantly aid analysts. Having an accurate calibration is fundamental for achieving confident quantitation from the analysis.
EN 14662-1 covers both gas-standard and liquid-standard loading. Gas-standard loading is the recommended method as it most closely mimics real sample conditions. We would recommend using the Markes Calibration Solution Loading Rig, and for gas standards the ACTI-VOC PLUS pump to draw standard gases over the sorbent tube.
2. Sampler preparation
EN 14662-1 recommends and contains technical information for sorbent tubes made from stainless steel tubing; 6.4 mm (1/4 inch) o.d., 5 mm i.d. and 90 mm long. These are Markes’ industry-standard size sorbent tubes, packed with any of the five sorbents detailed in the method. For longer sampling studies, we would recommend tubes packed with Carbograph™ 5TD (either as a single bed or as a multibed tube), and for shorter studies, where the sample volume will be below 40 L, Carbograph™ 1TD is recommended.
Sorbent tubes need conditioning as part of the sampler preparation and this can either be carried out on Markes’ thermal desorbers, using the dedicated conditioning method, or offline (saving instrument time and GC carrier gas) using the TC-20 tube conditioner.
3. Sampling
Once conditioned and sealed with caps the tubes are ready for sampling. Sampling, in compliance with the method, can be carried out in one of four ways:
- Single-tube sampling.
- Multiplexed sampling of two or more tubes.
- Parallel sampling of two or more tubes.
- Sequential sampling.
Markes’ ACTI-VOC Plus pumps are used for single-tube sampling, or combined with a TD instrument that facilitates one of the other sampling approaches. This allows for constant-flow sampling in the range of 20 mL/min to 200 mL/min.
If a sample rate of below 20 mL/min is required for the project, or it’s a sequential sampler containing multiple tubes and you need to ensure the tubes are sealed when not being sampled, We recommend using Markes’ SafeLok tubes.
4. Analysis
EN 14662-1 specifies that the thermal desorption system must include the following important features:
- Sealing of the samplers before and after desorption.
- Pre-purging of air from the samplers prior to desorption.
- Robust leak-testing before every sample is desorbed which is carried out without flow to maintain sampler integrity in the case of a leak.
- Refocusing on a secondary trap within the system.
- Back-flush desorption of both the sorbent tube and secondary focusing trap.
- Option to split the sample upon injection to the GC column.
All Markes’ tube-based thermal desorption instruments meet these criteria, increasing confidence in the results and saves labs time and money. Features useful for this method include:
- Automated addition of gas-phase internal standard.
- Automated dry purging of samplers to minimize water interference from humid samples.
- Option to split the sample during tube desorption.
- Option for quantitative re-collection of split flows to validate methods or simply repeat an analysis.
- Multiple carrier gas options - H2, He and N2 are available on all Multi-Gas
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