Revolutionary diffusion limiting tubes for pumped sampling

SafeLok™ tubes represent a major new development in pumped sampling of vapour phase organic compounds (VOCs) using sorbent tubes and thermal desorption. 

SafeLok™ tubes incorporate patented* diffusion locking technology at either end of the tube protecting the sample from ingress or loss of volatiles at all stages of the monitoring process.

With industry standard external dimensions (3½-inch (89 mm) long x ¼-inch (6.4 mm) O.D.) and full compliance with key international standard methods they provide a unique sampling solution for challenging applications including:

Long-term pumped sampling at low (~1 ml/min) flow rates
Traditionally long-term pumped sampling at flow rates < 10 ml/min have not been possible at trace levels, due to the errors introduced by diffusive uptake during the sampling period.  (Diffusive sampling occurs at 0.5 - 1 ml/min on standard tubes).  The use of SafeLok™ tubes reduces diffusive ingress to below 0.3 µL/min (0.4 ml/day).

No ingress of volatiles from the laboratory air during routine capping and uncapping procedures
When sampling trace level concentrations in 'ultra-clean' environments (mid-ocean, high altitude etc.) the ingress of even small amounts of laboratory air (for example, when tubes are uncapped/recapped prior to analysis) can introduce large errors.  The use of SafeLok tubes eliminates this issue.

Protection of the integrity of blank and sampled tubes during sequential sampling
When sequentially sampling onto a series of sorbent tubes (see MTS-32), the use of SafeLok™ tubes protects the integrity of both the blank tubes awaiting sampling and those tubes already sampled.

Monitoring very toxic compounds
By preventing losses (outgassing) of analytes from the tube, SafeLok™ technology also makes it safer to handle tubes that have been used to collect very dangerous compounds such as CW agents

Routine air monitoring applications
SafeLok™ tubes significantly reduce the risk of contamination from poorly fitted or loose storage caps and prevent necking or other damage to the ends of tubes caused by 'over enthusiastic' tightening of tube seals.

Technical information
SafeLok™ tubes are available in stainless steel or inert coated stainless steel and can be packed with up to three sorbents in series.

They comply with all retention and safe sampling volume data published for equivalent industry standard tubes and can be used with all conventional accessories - pen clips, storage caps, etc. 

SafeLok™ tubes are not suitable for diffusive monitoring.

SafeLok™ tubes require conditioning and capping in the usual way prior to use. They may be ordered pre-conditioned and capped with ¼-inch brass caps if required. 

For part numbers and pricing please contact your local Markes distributor or visit our on-line shop. 

Relevant technical support publications from Markes International can be automatically downloaded from this web site (registration required). Examples include:

• Brochure - SafeLok™ - Revolutionary Sorbent Tubes
• Brochure - Thermal Desorption & Air Sampling Products
• TDTS 20 - Determining and validating safe sampling volumes
• TDTS 61 – Diffusion-locking technology

Other sorbent tubes and accessories available from Markes include Sorbent tubes, Sorbents, Certified Reference Standards, Sorbent tube accessories, Diffusive sampling accessories, TubeTAG

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* Patent No: GB2337513