The answer is as follows: Using the GERSTEL TDU and CIS injector for thermal desorption of Twisters produces the highest recoveries of analytes from the stir bars, and the lowest detection limits and background levels. Analytes are transfered almost 100% to the GC column. Attempts by some chemists to place the Twister with extracted chemicals into the Agilent injector to desorb volatiles does not work and is a big waste of time. After back-extraction with solvents, the extracts can be injected into normal GC injectors but sensitivity and background problems are usually compromised, so this approach is inadvisable. When non-volatile or thermally labile compounds are of interest, solvent back-extraction of the Twister followed by injection into an LC system is the method of choice. This Twister back-extraction method can also be used for GC, but detection limits will be lower compared to using thermal desorption unless large volume injection techniques are used. Important advantages of GERSTEL back-extraction technology: useful for nonvolatiles and thermally labile compounds and extends capabilities to non-thermal desorption techniques and LC analysis. You can learn more about Twister back-extraction at the following link: www.richrom.com/application/v2/public/upload/0/default/70.pdf .Ray Marsili