On the capabilities of the rotating heater as a modulator for GCxGC—a reply

In this study, a combination of solid-phase extraction (SPE) and solid-phase microextraction (SPME) has been used to determine chlorobenzenes in air. Analytes were sampled by pumping a known volume of air through a porous polymer (Tenax TA). Then, the adsorbent was transferred into a glass vial and SPME was performed. The quantification was carried out using gas chromatography (GC)–electron-capture detection or GC–MS. Several SPME coatings (100 μm poly(dimethylsiloxane) (PDMS), 75 μm Carboxen (CAR)–PDMS, 65 μm PDMS–divinylbenzene (DVB), 65 μm PDMS–DVB and 85 μm polyacrylate (PA) were evaluated, obtaining the highest responses with Carbowax (CW)– PDMS for the most volatile chlorobenzenes, and with PDMS–DVB or CW–DVB fibers for the semivolatile compounds. To optimize some other factors that could affect the SPME step, a factorial design was used. Kinetic studies of the SPME process were also performed. Concerning the SPE step, breakthrough was studied, showing that 2.5 m3 of air could be processed without losses of the most volatile compounds. The performance of the method was evaluated. External calibration, which does not require the complete sampling process, demonstrated to be suitable, obtaining good linearity (R2 > 0.99) for all chlorobenzenes. Recovery studies were performed at two concentration levels (4 and 40 ng/m3), obtaining quantitative recoveries (>80%). Limits of detection at the sub ng/m3 were achieved for all the target compounds.