MTS-32: Sequential sampler


Muti-tube sequential sampling. Pumped sampling onto sorbent tubes remains one of the most popular and versatile air monitoring options for trace organics in environmental health and safety applications. It is applicable to vapour-phase organic chemicals ranging in volatility from n-C3 to n-C26 (depending on sorbent selection) and for vapour concentrations from low ppt to high ppm. The MTS-32 is a convenient, fieldportable multi-tube sequential sampler from Markes International Ltd. offering unattended sampling onto multiple tubes over time.

Applications for sequential sampling

The MTS-32 allows air to be pulled, sequentially, through a series of up to 32 industry standard (3.5-inch long x 0.25-inch O.D.) sorbent tubes using constant flow pump technology. The constant flow pump ensures that the same flow rate and volume of air is sampled onto each tube in the sequence regardless of impedance variations.


Key applications include:

  • Monitoring diurnal fluctuations of benzene, 1,3-butadiene and other pollutants in ambient air, for example in Air Quality Management areas,
  • Continuous monitoring of emission events in industrial locations.

Sampling times (1 minute - 99 hours) and flows (5-100 mL/min) may be user selected, but are then fixed for each tube in the sequence.

Preventing analyte ingress outside the sampling period

While outside the sampling period, sorbent tubes are sealed using Markes International patented diffusion locking technology. This prevents both diffusive ingress of atmospheric contaminants and loss of retained volatiles from sampled tubes. The diffusion locking technology is either configured into DiffLok™ caps for use with standard thermal desorption tubes (3.5-inch long by ¼-inch O.D.) or incorporated inside Markes unique SafeLok™ tubes.


SafeLok tubes have the same external dimensions and sorbent capacity as standard tubes, but contain inert diffusion-locking inserts in the air space either side of the sorbent packing. They are compatible with standard tube accessories (penclips, storage caps, etc.) -and have identical retention volume characteristics to standard tubes. However, these are not subject to diffusive ingress of contaminants or back diffusion of retained volatiles. SafeLok tubes are an ideal complement to the MTS-32, preventing ingress of loss of volatiles when tubes are not being sampled.


Markes diffusion locking technology has been demonstrated to prevent both ingress of volatiles and loss of retained analytes. For more information please see the associated leaflet on SafeLok tubes. 

Field portability

The MTS-32 is a standalone, battery powered device housed in a compact, showerproof box. It is ideal for field monitoring applications and will operate for over 40 hours on a fully charged battery. The battery is incorporated inside the main MTS-32 box; adaptors are also available to power the MTS-32 with mains electricity. The MTS-32 is not intrinsically safe. The battery or mains electricity adaptor maintains a supply of power to the FLEC® pump as well as powering the sequential sampler itself.


The MTS-32 is constructed of low-outgassing components and incorporates a fan to ensure an air change inside the box every few seconds. This ensures that the air sampled onto the sorbent tubes accurately reflects that in the immediate environment of the sampler and also allows quantitative measurement of transients. A protective gauze acros the fan inlet prevents particulates or wildlife from entering inside the MTS-32 housing and disrupting the air flow.


The MTS-32 can be adapted to sample sequentially from a discrete gas or air line.



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