The Role of Complementary Sampling Approaches, Combined with Thermal Desorption, in Assisting with Environmental Sample Characterization

Poster Presentation

Presented by C. Keller
Prepared by N. Watson
Markes International, 2355 Gold Meadow Way, STE 120, Gold River, CA, 95670, United States

Contact Information: [email protected]; 866-483-5684


Analysis of volatile and semi-volatile organics in environmental samples often requires extensive sample preparation for efficient extraction and concentration the target analytes, and or multiple sample preparation and injection techniques to fully characterize a sample.

A new multi-facted sampling approach, Centri, has been designed that limits sample preparation whilst maintaining maximum sensitivity and selectivity. Up to four different sampling techniques on one platform can be combined for comprehensive characterisation, these include, Headspace (HS), Solid phase microextraction (SPME), Thermal desorption (TD), and high-capacity sorptive extraction (HiSorb).

Headspace techniques are widely used for analysing VOCs in water, soil, and air. Although headspace overcomes the foaming issues associated with purge-and-trap methods, a drawback is that sensitivity is limited in conventional static (or equilibrium) headspace mode. The cryogen-free focusing trap on Centri enables enhanced sensitivity for headspace, and also allows the traditional Thermal desorption techniques to be carried out.

SPME is a convenient and readily-automated approach, typically used for sampling VOC and SVOC levels in the headspace of food, environmental and clinical samples. The availability of a variety of
extraction phases for SPME fibers allows different volatility and polarity ranges to be targeted. Combining SPME with secondary re-focusing on Centri enhances sensitivity by allowing multiple extraction cycles from a single sample to be ‘concentrated’ in one GC–MS run.

Thermal desorption (TD) has commonly been employed as a ‘solvent-free’ sampling approach for environmental air monitoring, but has historically been limited in its ability to deal with liquid matrices. New developments in sampling technologies, including high-capacity sorptive extraction, has extended the applicability of TD to liquid and solid samples, with the capacity for both immersive and headspace sampling allowing the extraction of components from within the sample prior to pre-concentration and analysis.

When used in conjunction with Thermal desorption, high-capacity sorptive extraction offers a number of well-known advantages over traditional solvent-extraction methods for a wide range of VOCs and SVOCs, including greatly improved sensitivity due to the avoidance of dilution, high extraction efficiency, and efficient transfer/injection into the GC. Furthermore, high-capacity sorptive extraction offers an extension to SPE & SPME methods which is simple to employ and, offers a versatile, robust method for gaining complementary information to that contained using other sampling approaches.

This multi-faceted sampling approach has been applied to different environmental samples, examples of which will be presented. The benefits of using TD sample introduction extend to the ability to re-collect sample for repeat analysis, assisting with method validation and eliminating the need to perform repeat extractions on limited sample quantities.