Best@BUCHI: Trace Analysis of PAHs Using Two EPA Extraction Methods

Authors: J. Cavegn, B. Haag, R. Hartmann, Buchi Labortechnik AG, 9230, Flawil, Switzerland
Best@BUCHI #51: Trace Analysis of PAHs
 
 Abstract: The Extraction System B-811 and the Syncore Analyst parallel concentrator from BUCHI as well as the Pressurized Solvent Extractor from Applied Separations were evaluated for the pretreatment of samples containing PAHs. Recoveries of extraction and subsequent concentration using acetone+n-hexane (1+1) were 70-95% for 2 ring and 90-100% for the less volatile 3-5 ring PAHs. A good precision (95% confidence level) of less than 6%, naphtalene excluded (12%), was found. No significant difference was observed between the two extraction methods. Download and review http://tiny.cc/jl2p6 this Best@BUCHI study.  
 

Introduction: Polycyclic aromatic hydrocarbons (PAHs) are organic pollutants primarily formed by incomplete combustion and incineration. PAHs adsorb strongly to small carbonaceous particles but are also present in the vapor phase. Therefore, they can undergo long range transport. Typical concentrations are in the sub-ppb to ppm range. PAHs also bioaccumulate in food webs and are partially mutagenic and carcinogenic. Therefore, PAH analysis is requested by regulatory bodies.

The US Environmental Protection Agency (EPA) introduced a priority pollutant list of 16 PAHs (EPA610) in 1982. The analyses of PAHs contamination at the trace level includes sample extraction and extract concentration.

 
Instrumentation: Automated Soxhlet extraction was performed with the Extraction System B-811 (Buchi), pressurized solvent extraction with the PSE system (Applied Separations) and subsequent concentration was carried out with the parallel evaporator Syncore Analyst (Buchi) holding 12 positions. The locally cooled appendix of the sample vessel prevents evaporation to dryness.

Vacuum was generated by the Vacuum Pump V-700 (Buchi). A pressure profile was optimized and programmed with the Vacuum Controller V-855 (Buchi) and the condenser was cooled with ethanol+water (40+60) using the Recirculating Chiller B-740/8 (Buchi).Both automated Soxhlet extraction (EPA3541) and pressurized solvent extraction (EPA3545) are approved extraction techniques (EPA3500) for solid samples.

 

Conclusions: High recoveries and good precision were found for the PAHs sample preparation. The results are better than described in the EPA method 8270. Soxhlet extraction and PSE are able to extract the 16 EPA-PAHs nearly exhaustive and with good precision.

 

Recoveries and precision are similar for both methods. However, the influence of solvent is more critical for PSE and should be carefully optimized.

 

A second static cycle can be necessary for a complete extraction. The results were obtained with the fastPSE system, but comparable results are archieveable with the SpeedExtractor E-916, too  Loss of the most volatile PAHs during extract concentration could be nearly completely reduced by the combined application of a vacuum controller, a Flushback module, low cooling temperature and low speed of orbital movement.



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