Dear Sir. Concerning your issue about the use of solid-phase microextraction, or SPME for pollutant gas in air. Solid phase microextraction (SPME) with poly(dimethylsiloxane) (PDMS) is used to sample dynamic hydrocarbon standard gas mixtures with calibration for temperature, relative humidity, gas velocities, and gas concentrations. Equilibration times were found to vary from 15 to 450 s depending on the compound. Relative humidity greater than 90% at various temperatures was found to decrease analyte mass loading by 10%. Investigation of linearity with PDMS showed all of the analytes had a linear relationship between mass loaded at equilibrium and the gas concentrations studied. Analyte detection limits are better than those for conventional grab sampling (concentration with adsorbent tubes and analysis by gas chromatography and flame ionization detection). Partition coefficients (K) were established at various temperatures, yielding a linear relationship between log K and T-1. The linear expression has a slope that is a function of the gas constant and the analyte heat of vaporization (ΔH v) and a y-intercept that is a combination of terms among which include the gas constant, analyte ΔH v, and activity coefficient; therefore, K values can be estimated using literature ΔH v and ascertained at temperatures for which a K was not determined. This removes the restriction that calibration and air sampling must be carried out at the same temperature. A comparison of PDMS (100 μm) fiber lengths (n = 13) revealed an average fiber length of 1.02 ± 0.03 cm. An interfiber estimation of method precision (n = 10) yielded less than 9% RSD for all the test analytes. When a correction for fiber lengths was applied, the differences between the means of area counts for the individual fibers was statistically insignificant. SPME was successfully field tested as a grab sampler and an integrated sampler to analyze air at an industrial site, with excellent agreement to traditional air sampling methods. This work suggests that ambient and industrial air sampling with SPME is possible with essentially no calibration of the sampling device. It is only necessary to know the analyte's K to the fiber at various temperatures which is based on defined and empirically determinable physical constants. I think the following below links may help you in your analysis:

https://pubs.acs.org/doi/abs/10.1021/ac960415w

https://pubs.acs.org/doi/abs/10.1021/ac000518l

https://link.spr nger.com/article/10.1007%2Fs002160051273

Thanks

Mohsen,

You can use SPME - the air sample should be placed in a chamber and the SPME fiber should be introduced to this chamber. However, the sorption capacity is very low, thus I do not recommend this technique for this purpose.

Standard techniques make use of a sorption tubes - depending on volatility range of VOCs with TENAX or a sequence of sorbents with carbon based sorbents at the end of sorption tubes (to trap the most volatile analytes).

You can use a pump or big syringe to suck the air sample through the tube.

You can use differnt volumen depending on the characteristics of VOCs and used sorbents begginning from 100 mL up to even a few liters.

At the end, thermal desorption is used to inject the analytes into the GC system.

regards,

G

I added also a Supelco selection guide for sorbents - as you can see for many VOCs you can sample even much above 100 L.

regards,

G