Solid Phase Microextraction

SPME-Diffusive Fiber Holder (DFH)

DFHSPME-Diffusive Fiber Holder (DFH), Cat.No. 57584-U
for TWA Air Sampling with SPME

A SPME-Diffusive Fiber Holder (DFH) installed with a FFA is capable of determining the time-weighted average (TWA) concentration of volatile organic compounds (VOCs) in air. Unlike conventional sampling with SPME, in which a fiber is extended outside its needle, during TWA passive sampling the fiber is retracted at a known distance into the needle. The DFH SPME passive sampler collects the VOCs by the mechanism of molecular diffusion and sorption onto the fiber.

DFH

DFH Fig. 2This process is described by Fick’s first law of diffusion, whereby determination of the amount of analyte accumulated over time enables measurement of the TWA concentration to which the sampler was exposed.
C=M_SR  x T
where Cis TWA concentration, m is analyte mass, SR is sampling rate (which can be found/estimated in the manual) and t is sampling time (e.g. 15 min or 8 h).




DFH Fig. 3TWA passive sampling with an SPME device has been shown to be almost independent of air flow rate, and to be more tolerant of high and low analyte concentrations and long and short sampling times, because of the ease with which the diffusion path length (z) can be changed (Fig. 2) to control the device’s sensitivity. Environmental conditions, e.g. temperature, pressure, relative humidity and ozone, have little or no effect on sampling. For more details please refer to the references listed below.




DFH Fig. 4During the sampling the SPME needle tip is protected by a cage (Fig. 3) allowing the analytes to freely enter the sampler. After sampling the installed SPME-FFA can be sealed off in the DFH (built-in PTFE Sealing Mechanism Fig. 4) or removed and placed in an optional SPME FFA Storage Container (57592-U) for transport.





The FFA can be desorbed manually with the DFH by using a manual desorption adapter (57541-U, Fig. 5), or by removing the FFA and placing it in a tray of an MFX system for automated unattended desorption (Fig.6).

DFH Fig. 5DFH Fig. 6


For more details on the use of this device please refer to the Manual under Technical Resources, below.

For Ordering Information click here

Technical Rescources
Manual - SPME-Diffusive Fiber Holder (DFH)
Datasheet - SPME Fast Fit Fiber Assemblies (FFA)



References for diffusive/air sampling with SPME:

  1. Anal. Chem. 2003, 75, 2004-2010 – Time-Weighted Average Passive Sampling with a Solid-Phase Microextraction Device (Yong Chen and Janusz Pawliszyn).
  2. Journal of Chromatography A, 892 (2000) 455–467 - Time-weighted average sampling of volatile and semi-volatile airborne organic compounds by the solid-phase microextraction device (Abir Khaled, Janusz Pawliszyn).
  3. Journal of Chromatography A, 1129 (2006) 29–33 - Diffusive sampling of airborne furfural by solid-phase microextraction device with on-fiber derivatization (Shih-Wei Tsai, Kuo-Yuan Kao).
  4. Anal. Chem. 1999, 71, 1513-1520 Time-Weighted Average Sampling with Solid-Phase Microextraction Device: Implications for Enhanced Personal Exposure Monitoring to Airborne Pollutants (Perry A. Martos and Janusz Pawliszyn)