Static (equilibrium) headspace injection is commonly used for GC determination of volatiles in solid and liquid samples. Since this technique relies on the analyte partitioning between the sample and headspace, and uses a fi xed injection volume, it may not provide adequate detection limits, particularly for higher molecular weight, higher boiling analytes.

In this study, we describe a new automated dynamic headspace analyzer that uses a two-needle design to flush the headspace of vessels ranging from 10 mL to 1.0 L onto replaceable adsorbent traps. The clean adsorbent traps are stored in a sealed tray on the x-y-z robotic sampler which transports them to the sample vessel, then directly to the integrated thermal desorber. This design enables automated optimization of trapping conditions including choice of adsorbent.

Performance of the new system was assessed using standard sample types and compared to traditional static headspace (HS) analysis and optimized SPME sampling. In general, better detection limits were obtained with dynamic headspace while maintaining reproducibility comparable to the other techniques.

Dynamic Headspace (DHS)

Automated Dynamic Headspace (DHS) is available for the GERSTEL MultiPurpose Sampler (MPS). The DHS station efficiently extracts and concentrates VOCs from liquid or solid sample placed in standard Headspace vials (DHS) or in larger sample containers up to 1 L volume (DHSLarge). The sample is thermostated and agitated while the headspace is purged with a controlled flow of inert gas, providing controlled and efficient extraction conditions. Sample temperatures can be selected from 10oC to 200oC. Lowering the temperature provides a means of reducing the amount of water vapor released and ultimately retrapped. The DHS station additionally holds a replaceable adsorbent- or sorbent filled tube used for analyte concentration. The temperature of the adsorbent tube during the DHS process can be varied from 20oC to 70oC for optimal trapping of the analytes in question.