Journal of Chromatography A, 1136 (2006) 89–98 Comparison of various detection limit estimates for volatile sulphur compounds by gas chromatography with pulsed flame photometric detection Lionel J.J. Catalan a,∗ , Victor Liang a,b , Charles Q. Jia b a Department of Chemical Engineering, Lakehead University, Thunder Bay, Ont., Canada b Department of Chemical Engineering and Applied Chemistry, University of Toronto, Ont., Canada Received 12 July 2006; received in revised form 14 September 2006; accepted 19 September 2006 Available online 27 October 2006 Abstract This paper addresses the variations that presently exist regarding the definition, determination, and reporting of detection limits for volatile sulphur compounds by gas chromatography with pulsed flame photometric detection (GC-PFPD). Gas standards containing hydrogen sulphide (H 2 S), carbonyl sulphide (COS), sulphur dioxide (SO 2 ), methyl mercaptan (CH 3 SH), dimethyl sulphide (DMS), carbon disulphide (CS 2 ), and dimethyl disulphide (DMDS) in concentrations varying from 0.36 ppb (v/v) up to 1.5 ppm (v/v) in nitrogen were prepared with permeation tubes and introduced in the gas chromatograph using a 0.25-ml gas sampling loop. After measuring the PFPD response versus concentration, the method detection limit (MDL), the Hubaux–Vos detection limit (x D ), the absolute instrument sensitivity (AIS), and the sulphur detectivity (D s ) were determined for each sulphur compound. The results show that the MDL determined by the US Environmental Protection Agency procedure consistently underestimates the minimum concentrations of volatile sulphur compounds that can be practically distinguished from the background noise with the PFPD. The Hubaux–Vos detection limits and the AIS values are several times higher than the MDL, and pro- vide more conservative estimates of the lowest concentrations that can be reliably detected. Sulphur detectivities are well correlated with AIS values but only poorly correlated with MDL values. The AIS is recommended as a reliable and cost-effective measure of detection limit for volatile sulphur compounds by GC-PFPD, since the AIS is easier and faster to determine than the MDL and the Hubaux–Vos detec- tion limit. In addition, this study confirmed that the PFPD response is nearly quadratic with respect to concentration for all volatile sulphur compounds. © 2006 Elsevier B.V. All rights reserved. Keywords: Pulsed flame photometric detector; PFPD; Gas chromatography; Detection limit; Volatile sulphur compounds; Sulphur 1. Introduction Quantitative analysis of volatile sulphur compounds (VSCs) is most commonly carried out by gas chromatography (GC) due to its excellent separation performance and the availability of several detection methods that are both sensitive and selec- tive to sulphur compounds. These include flame photometric detection (FPD), pulse flame photometric detection (PFPD), sul- phur chemiluminescence detection (SCD), and atomic emission detection (AED) [1–7]. PFPD provides improved detection sen- sitivity and much higher selectivity for sulphur compared to FPD ∗ Corresponding author. Tel.: +1 807 343 8573; fax: +1 807 343 8928. E-mail address: Lionel.Catalan@lakeheadu.ca (L.J.J. Catalan). [8,9]. Although less sensitive than SCD and AED [7], PFPD is more economical. For very low concentrations (e.g., less than 20 ppbv), PFPD has been successfully used in conjunction with a preconcentration step, such as cryogenic trapping [10,11], sorption on porous polymers and molecular sieves [12–14], or solid-phase microextraction [15]. The PFPD system differs from the FPD system in that the flow of combustible gases (hydrogen and air) to the PFPD system is too low to sustain a continuous flame. After the combustible gases are ignited by a heated ignitor coil at the top of the detec- tor, the flame propagates downwards through a quartz combustor tube and extinguishes once the combustible gases are depleted. The next ignition occurs after fresh combustible gases flowing upward from the base of the detector have flushed the com- bustion products from the combustor and reached the ignitor 0021-9673/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2006.09.056