J. Sep. Sci. 2006, 29, 1909 – 1921 C. v. Mühlen et al. 1909 Carin von Mühlen 1 Weeraya Khummueng 2 Claudia Alcaraz Zini 1 Elina Bastos Caram¼o 1 Philip J. Marriott 2 1 Universidade Federal do Rio Grande do Sul, Instituto de Química, Porto Alegre, RS, Brasil 2 Australian Centre for Research on Separation Science, School of Applied Sciences, RMIT University, Melbourne, Australia Review Detector technologies for comprehensive two-dimensional gas chromatography The detector is an integral and important part of any chromatographic system. The chromatographic peak profiles (i. e. peak separation) should, ideally, be unaffected by the detector – it should only provide the sensing capacity required at the end of a column separation process. The relatively new technique of comprehensive 2-D GC (GC6GC) extends the performance of GC manyfold, but comes at a price – existing GC systems may not be adequately designed with the requirements of GC6GC in mind. This is primarily the need for precise measurement of very fast peaks entering the detector (e. g. as fast as 50 ms basewidth in some instances). The capacity of the detector to closely track a rapidly changing chromatographic peak profile depends on a number of factors, such as design of flow paths and make-up gas introduction, type of detector response mechanism, and the chemistry of the response. These fac- tors are discussed here as a means to appreciate the technical demands of detection in GC6GC. The MS detector will not be included in this review. Keywords: Detection speed / Comprehensive two-dimensional gas chromatography / Received: November 17, 2005; revised: January 28, 2006; accepted: January 19, 2006 DOI 10.1002/jssc.200500443 1 Introduction Comprehensive 2-D GC (GC6GC) is now firmly estab- lished on the GC scene. By any measure, GC6GC has sig- nificantly altered the way in which the GC experiment is conducted (Fig. 1). This figure shows that a rapid analysis occurs on the second dimension ( 2 D) subsequent to the , regular’ first dimension ( 1 D) separation. The modulator M performs the function of collecting (focussing) the solute at the end of 1 D and rapidly introducing it to the 2 D column. The detector therefore only records these very fast, narrow, modulated peaks. From modulation of the migrating chromatographic band to data presenta- tion, experimental set-up, and even terminology, ana- lysts who perform GC6GC are faced with a new opera- tional paradigm, and must negotiate their way through coupled column systems, routinely performing very fast (ultrafast in some instances) separations, interpreting their results from a new viewpoint, and optimising the experiment in ways that are, whilst ultimately logical, a significant departure from the classical single column experiment. One of the less-considered aspects of the GC6GC experi- ment is the detector. Perhaps whether it is due to the extra separation performance that reduces the need for a selective detector, or the reliance on the flame ionisation detection (FID) , workhorse‘, or the belief that there will be operational difficulties with most selective detectors in GC6GC, there is not a wealth of information in the Correspondence: Professor Philip J. Marriott, Australian Centre for Research on Separation Science, School of Applied Sciences, RMIT University, GPO Box 2476V, Melbourne 3001, Victoria, Australia. E-mail: philip.marriott@rmit.edu.au. Fax: +61-3-9639-1321. Abbreviations: AED, Atomic Emission Detector; BNT, benzoni- trothiophene; BT, benzothiophene; DBT, dibenzothiophene; ECD, Electron Capture Detector; FCC, fluid catalytic cracking; FID, flame ionisation detection, NCD, Nitrogen Chemilumines- cence Detector; NPD, Nitrogen Phosphorus Detector; PCBs, poly- chlorinated biphenyls; TID, Thermionic Detector; SCD, Sulphur Chemiluminescence Detector; l-ECD, Micro-Electron Capture Detector i 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com Figure 1. Schematic diagram of the GC6GC instrument, showing use of a short, fast elution second dimension col- umn which produces very narrow peaks at the detector. I, injector; M, modulator; D, detector. 1 D = first dimension col- umn, 2 D = second dimension column.