Markes International

TD100-xr™ is an automated thermal desorption system for the rapid and unattended processing of up to 100 sorbent tubes in a single sequence. It is the perfect thermal desorption unit for high-throughput analytical laboratories needing to process large numbers of tube-based samples automatically.

TD100-xr is also available with our award-winning Multi-Gas functionality, independently certified for operation with a choice of three carrier gases: helium, nitrogen, and hydrogen. Hydrogen carrier gas offers fast, cost-effective analyses and protection against future helium shortages.

Read more: TD100-xr brochure

Single-tube thermal desorption with unprecedented upgradeability

The UNITY-xr™ is the industry-leading thermal desorption (TD) instrument for the analysis of VOCs and SVOCs using standard 3 ½ inch (~9 cm) adsorbent sampling tubes. While the UNITY-xr is a standalone single-tube system, its modular design allows for seamless upgrades to meet the evolving requirements of any analytical chemistry laboratory. Key modules include:

 - ULTRA-xr™: A high-throughput autosampler with a capacity of up to 100 TD tubes. It features automated sample re-collection and advanced tube tracking via barcodes or RFID TubeTAGs.

 - Air Server-xr™: A versatile module for online VOC monitoring. It is ideal for the real-time analysis of ozone precursors, terpenes, ultra-volatiles, sulfur compounds, and greenhouse gases. It also enables direct sampling from gas bags or canisters, equipped with an internal pump for low-pressure sampling.

 - CIA Advantage-xr™: A cryogen-free autosampler designed for the analysis of VOCs and SVOCs from canisters and whole-air samples via GC(MS).

Download the product catalog here.

Conditioning and dry-purging for multiple sorbent tubes

In TD–GC workflows, residual contaminants and carryover in sorbent tubes can introduce unwanted artefacts, mask low-level targets and reduce confidence in results reported. Even small amounts of contamination can lead to costly re-analysis, particularly in trace-level volatile organic compound (VOC) applications where sensitivity is critical. Clean sorbent tubes are essential to minimise background, maximise sensitivity and protect data quality. 

The TC-30™ is an easy-to-use, off-line device for the automated and simultaneous conditioning and dry-purging of up to 30 thermal desorption tubes. The system uses a flow of clean, dry nitrogen rather than expensive  helium carrier gas, significantly reducing operating costs. Its integrated touch-screen with in-built preset and fully-programmable methods improves workflow efficiency and accelerates routine tasks in busy laboratories.

Read more: TC-30 Brochure

Sorbents

In the context of thermal desorption, a sorbent (or adsorbent) is a material used to capture volatile compounds. Sorbents are fundamental to the process of TD and are used in both sorbent tubes and focusing traps. Many types of sorbents are available, with some of the most popular being porous polymers such as Tenax® TA, graphitised carbon blacks such as Carbograph and carbonised molecular sieves such as Carboxen 1000.

It is generally advised to match the sorbents in the sorbent tube and focusing trap, because analytes that can be trapped at ambient temperature on a tube can then be trapped at ambient temperature on a focusing trap. Being able to use near-ambient conditions helps reduce the impact of interferences due to water/moisture.

Read more: Sorbents - Quick reference guide

Micro-Chamber/Thermal Extractor

The Micro-Chamber/Thermal Extractor™ (µ-CTE™) is a versatile and compact unit with four small cylindrical chambers that enables the sampling of chemicals released from products or materials. Released volatile and semi-volatile organic compounds (VOCs and SVOCs) are collected onto sorbent tubes for analysis by TD–GC–MS. Applications range from emissions screening of construction materials, consumer products, and car trim to aroma or fragrance profiling.

- Designed for sampling VOCs or SVOCs emitted from products and materials.

- Humidifier and permeation accessories extend the capabilities of the instrument.

- A full range of accessories for the Micro-Chamber/Thermal Extractor is available.

Read more: Micro-Chamber brochure

ACTI-VOC PLUS

ACTI-VOC PLUS™ is a robust, fast-flow sampling pump kit designed for sampling volatile organic compounds (VOCs) onto sorbent tubes for analysis via thermal desorption (TD). With an expanded flow range compared to the ACTI-VOC series, ACTI-VOC PLUS is the ideal choice for sampling semi-volatile organic compounds (SVOCs), where required sampling flows are in the range of 300–500 mL/min.

The device allows for the sampling of precise air volumes in constant-flow mode (20–500 mL/min). Long battery life ensures stable performance for over 8 hours. The pump is programmable and allows for the recording of sample data. A dedicated carry-case protects the pump from damage during storage and transport. Users can replace the filters and battery themselves to minimize downtime during maintenance.

Read more: ACTI-VOC PLUS flyer

Pumps used for active sampling include 'grab-samplers' and battery-powered pumps. By allowing precise volumes from 20 mL to several hundred liters to be sampled into tubes, this method ensures compatibility with a wide concentration range (from sub-ppt to high ppm levels).

Active sampling can be used in combination with multi-bed sorbent tubes to collect analytes over a wide volatility range; it can also be used for collecting very volatile organic compounds - VVOCs (e.g., propene and chloromethane) through to semi-volatile organic compounds - SVOCs (e.g., dodecyl phthalate and six-ring PAHs).

MTS-32 (multiple-tube sampler)

The MTS-32 Multi-tube sequential sampler is a compact, robust, and portable sampler, designed for unattended sampling of air onto a series of sorbent tubes. Ambient air is pulled sequentially through a series of up to 32 industry-standard thermal desorption tubes by a low-flow sampling pump. Each tube is sampled at the same flow rate, so that the same volume of air is collected.

- Field-portable – the MTS-32 can be used virtually anywhere

- Labour-saving, unattended sampling – retrieve the instrument at the end of the extended sampling period

- Trusted sample integrity – tubes are sealed with diffusion-locking technology, preventing unwanted air ingress and sample loss

Read more: MTS-32 flyer

Gas regulators

Gas regulation is essential to control gas supply into an analytical system or off-line accessory. Markes offers two types of regulator: one for use with all Markes’ thermal desorption instruments such as the TD100-xr and UNITY-xr, and the other for off-line accessories such as a tube conditioner (TC-20) and Calibration Solution Loading Rig (CSLR).

- Regulate high-purity carrier gas/dry gas

- Fitted with on/off toggle(s)

- Lightweight, with minimal footprint

Flowmeter

A digital flowmeter is required to measure gas flows associated with thermal desorption equipment and sampling.

Markes’ recommended flowmeter is tested over the range of 0.0 to 500.0 ml/min with an uncertainty of +/- 0.4 ml/min or 2.5%, whichever is greater. Calibration Reference Temperature and Pressure: 0°C and 760 mm Hg. Compatible with eight gases including helium, hydrogen and nitrogen, in the range 0.1–500 mL/min.

- Enables repeatable analysis and compliance with standard methods

- Rechargeable battery

- Calibration traceable to UKAS standards

Calibration Solution Loading Rig (CSLR)

Markes’ Calibration Solution Loading Rig (CSLR) has been designed for loading sorbent tubes with gas- or liquid-phase standards. It allows you to calibrate the entire TD–GC–MS analytical system for qualitative and quantitative analysis. It is used as part of routine quantitative analysis, or when changing methods and/or analytical conditions.

- Specifically designed for loading sorbent tubes with VOC gas standards

- Key to TD standard methods, such as ISO 16017 and US EPA TO-17 – standards are loaded onto a tube in a stream of carrier gas using an unheated apparatus

- Compatible with ¼″ and 6 mm o.d. tubes – for 6 mm tubes a different ferrule is required (C-FP010-XZ)

Read more: Calibration Solution Loading Rig Instruction for use

Easy-VOC

Easy-VOC is a grab sampling kit, a hand-operated pump for rapid ‘grab-sampling’ of precise volumes of air/gas directly onto sorbent tubes, for analysis by thermal desorption (TD). In contrast to canister sampling, grab-sampling onto sorbent tubes allows analytes from a wider volatility range to be sampled (in the region of C2/3 to n-C44), plus many polar and reactive species.

- Enables sampling of precise volumes of air (50 mL and 100 mL intervals)

- Portable and can be used remotely without batteries or electrical power

- No need for calibration means no additional tools are required

Read more: Easy-VOC flyer