Solvent vapour monitoring in work space by solid phase micro extraction

Area of Science:

• Analytical Chemistry
• Environmental Science
• Occupational Health

Background:

• Conventional methods for volatile organic compound (VOC) sampling, such as charcoal tube sampling with carbon disulfide extraction, are effective but involve solvents and are time-consuming.
• Solid Phase Micro Extraction (SPME) presents a solvent-less and rapid alternative for air sampling.
• Evaluating SPME's efficacy in a typical laboratory setting is crucial for its adoption in occupational and environmental monitoring.

Purpose of the Study:

• To compare the performance of Solid Phase Micro Extraction (SPME) with active sampling techniques, specifically charcoal sorbent tubes, for the analysis of volatile organic compounds (VOCs) in a laboratory atmosphere.
• To evaluate different SPME fiber coatings for their suitability in detecting common solvent vapors at ambient concentrations.
• To determine the sensitivity, repeatability, and optimal exposure time for SPME analysis of specific VOCs.

Main Methods:

• SPME was employed using two fiber coatings: a general-purpose polydimethylsiloxane (PDMS) and a mixed-phase carboxen/PDMS.
• The SPME method was compared against the conventional charcoal sorbent tube method for active sampling.
• Calibration studies were performed using dichloromethane (DCM), benzene (B), and toluene (T) to establish optimal exposure times and assess repeatability.
• Minimum detectable amounts (MDAs) and inter-fiber variations were quantified.

Main Results:

• The mixed-phase carboxen/PDMS fiber demonstrated suitability for VOC analysis, whereas the standard PDMS fiber was found to be inadequate.
• SPME exhibited significantly higher sensitivity compared to the charcoal sorbent tube method.
• An optimal exposure time of 5 minutes was identified for solvents like DCM, with repeatability below 20% for a wide range of organic vapors.
• The minimum detectable amount for DCM was as low as 0.01 microg/l (0.003 ppmv).
• Inter-fiber variations were within 30% at 1 microg DCM/l, indicating suitability for field monitoring.
• An actual application measuring background solvent vapor levels showed agreement within a factor of two with the charcoal sampling method, with no DCM concentrations exceeding the regulatory limit of 50 ppmv.

Conclusions:

• The mixed-phase carboxen/PDMS fiber SPME technique is a highly sensitive and efficient alternative to conventional methods for VOC monitoring in laboratory environments.
• SPME offers advantages in terms of speed, reduced solvent use, and superior sensitivity, making it a valuable tool for occupational and environmental exposure assessments.
• The method's performance characteristics, including sensitivity and repeatability, are adequate for practical field monitoring applications.