Multipurpose Sampler (MPS)
1 noiembrie 2016
Automated Solid Phase Extraction (SPE)
1 noiembrie 2016
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Dynamic Headspace (DHS)

Caracteristici:

Dynamic Headspace benefits:

  • The GERSTEL Dynamic Headspace provides lower detection limits than static headspace, SPME and other widely used techniques
  • High productivity through high throughput design and complete automation from sample preparation to GC/MS-analysis
  • Highest flexiblity: User defined extraction time, flow, temperature and adsorbent
  • The Dynamic Headspace technology provides multiple water management options to ensure best chromatography and MS stability

Automated 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 samples 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 10 °C to 200 °C. 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 20 °C to 70 °C for optimal trapping of the analytes in question.

Adsorbent tubes used are standard GERSTEL Thermal Desorption Unit TDU tubes. Following analyte concentration, the tube is automatically transferred to the TDU for Thermal Desorption and analyte transfer to the GC. Tubes are fitted with individual adapters enabling both automated movement and leak-free sealing during the Dynamic Headspace and Thermal Desorption steps and during storage in the autosampler tray.

Automated Dynamic Headspace DHS combined with sample introduction to a GC or GC/MS system is performed by the MPS and TDU. Up to 98 samples can be processed automatically in one sequence.

Dynamic Headspace benefits:

  • The GERSTEL Dynamic Headspace provides lower detection limits than static headspace, SPME and other widely used techniques
  • High productivity through high throughput design and complete automation from sample preparation to GC/MS-analysis
  • Highest flexiblity: User defined extraction time, flow, temperature and adsorbent
  • The Dynamic Headspace technology provides multiple water management options to ensure best chromatography and MS stability

The DHS station provides sample thermostating and agitation combined with purging of the sample headspace with a controlled flow of inert gas. Extracted compounds are trapped and concentrated on a replaceable adsorbent-filled trap, which is subsequently thermally desorbed in the integrated Thermal Desorption Unit TDUfollowed by determination of the analytes using GC/MS. While in the GERSTEL MPS autosampler, samples are stored in standard headspace vials at ambient temperature. Optionally, samples can be stored at controlled temperatures between 4 °C to 200 °C.

During extraction, samples can be agitated to enhance and speed up the extraction process. The temperature of the adsorbent tube during the DHS process can be independently controlled from 20 °C to 70 °C for optimal trapping of the analytes of interest. The adsorbent tube can be dry purged for water removal to ensure the best possible chromatography and MS stability. A new adsorbent tube can be used for every sample, eliminating the risk of cross contamination or the same tube can be used for multiple samples as in standard Purge and Trap instruments.

Analysis of coffee powder using DHS, HS-SPME and Static Headspace

In order to compare different gas phase extraction techniques, 100 mg samples of a ground coffee were analyzed using static headspace, headspace-SPME and DHS. Comparable extraction conditions were chosen:

HS HS-SPME DHS
 Temperature40 °C40 °C40 °C
 Extraktion time30 min30 min10 min
 Purge flow  20 ml/min
 AdsorbentDVB/Carboxen/PDMSTenax

It can be seen from the sample chromatograms and the bar graph showing relative peak areas (DHS response normalized to 100%), that DHS provided the highest response for the analytes that were determined.

For most analytes, DHS provided relative standard deviations well below 5%, which is equal to or better than the other techniques.

DHS – powered by MAESTRO

DHS is easily and conveniently controlled from the GERSTEL MAESTRO Software

Parallel processing of samples enable the DHS process to be performed during the chromatographic run of the preceding sample for optimal productivity and for highest system utilization.

Automated liquid handling in the MPS can be used for additional sample prep steps. As part of the sample prep procedure, standard addition can be performed automatically for best possible analytical results.

Sample prep steps are selected by mouse-click from a pull-down menu using the PrepBuilder function of the GERSTEL MAESTRO software.

A graphical scheduler display for the DHS process provides an overview of the time required for each individual step and for the complete sequence of samples for easier planning.

Just one method and one sequence table controls the complete process from DHS through sample prep and sample introduction to GC/MS analysis. Integrated control ensures a more efficient operation with less risk of error. The GERSTEL MAESTRO Software operates stand-alone or fully integrated with the Agilent Technologies ChemStation Software.