Use of new generation poly(styrene-divinylbenzene) resins for gas-phase trapping-thermal desorption. Application to the retention of seven volatile organic compounds.
Two new generation polymeric resins, Bond Elut ENV (styrene-divinylbenzene) from Varian and LiChrolut EN (ethylvinylbenzene-divinylbenzene) from Merck, commonly used in liquid--solid-phase extraction (SPE) were evaluated as sorbents for gas-phase sampling followed by thermal desorption and compared to Tenax TA, a reference sorbent in this kind of applications. The three resins were tested against seven volatile organic compounds (VOCs): 1-octene, ethylbenzene, (p-, m-, o-)xylenes, styrene and 1,4-dichlorobenzene. Elution curves for all compounds were determined at temperatures from 120 to 180 degrees C, and from such curves, different parameters, such as retention factor (k), distribution coefficient (K), height equivalent to a theoretical plate (H), asymmetry factor (Fa) and breakthrough volume (VB) were calculated and extrapolated at room (25 degrees C) and desorption (220 degrees C) temperatures in order to estimate breakthrough and elution volumes. In average, retention in LiChrolut EN is 10 and 200 times stronger than in Bond Elut ENV and Tenax TA, respectively, but its chromatographic behavior is rather poor giving quite asymmetric elution profiles (Fa >1.8 at 120 degrees C). Bond Elut ENV exhibited the best chromatographic behavior, with H values two or five times lower than those of LiChrolut EN or Tenax TA. An additional advantage of the new sorbents is that retention decreases with T much faster than it does in Tenax (8 or 20 times for Bond Elut ENV or LiChrolut EN). Modeling has finally shown that beds with 60-80 (for Bond Elut ENV) or 300-400 (for LiChrolut EN) times less of sorbent have the same retention properties than standard Tenax TA tubes and similar (LiChrolut EN) or five to six times smaller (Bond Elut ENV) elution volumes. These predictions have been experimentally confirmed.
López
Patricia
P
Department of Analytical Chemistry, Aragón Institute of Engineering Research, CPS-University of Zaragoza, Zaragoza 50018, Spain.
Batlle
Ramon
R
Nerín
Cristina
C
Cacho
Juan
J
Ferreira
Vicente
V
D009930:Organic Chemicals / Q000302:isolation & purification*; D011108:Polymers / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry*; D015203:Reproducibility of Results; D052616:Solid Phase Extraction / Q000379:methods*; D013696:Temperature; D014835:Volatilization
D009930:Organic Chemicals; D011108:Polymers; D011137:Polystyrenes