Use of solid phase microextraction (SPME) in the analysis of the reduced sulfur compounds (RSC) and its experimental limitations Ehsanul Kabir, Ki-Hyun Kim ⁎ Department of Environment & Energy, Sejong University, Seoul, 143-747, Republic of Korea abstract article info Article history: Received 13 December 2011 Received in revised form 10 January 2012 Accepted 11 January 2012 Available online 18 January 2012 Keywords: Reduced sulfur compounds Carboxen–PDMS fiber Solid-phase microextraction Pulsed flame photometric detection In this study, techniques based on solid-phase microextraction (SPME) with gas chromatography (GC)– pulsed flame photometric detection (PFPD) were evaluated for its application toward a list of reduced sulfur compounds (RSCs) such as hydrogen sulfide (H 2 S), methanethiol (CH 3 SH), dimethyl sulfide (DMS), carbon disulfide (CS 2 ), and dimethyl disulfide (DMDS). Its performance was tested against direct injection (DI) and thermal desorber (TD) approaches. Although the SPME-based calibration of RSCs showed good linearity (r 2 > 0.9) like other methods, it was more prone to analytical bias for the lighter molecular weight (MW) RSCs (especially H 2 S) due to distinctively reduced sensitivity relative to the heavier MW compounds. As such, the detections limits (DL) of SPME vary by more than an order of magnitude for the lighter and heavier MW RSCs (DL = 16.9 ng for H 2 S and 1.46 ng for DMS). Evidence collected from an extended reproducibility test further supports that the experimental reliability of SPME approach is fairly low, especially with respect to H 2 S. The quality of SPME-based analysis thus needs more cautious validation in the study of odor and air pollution, as the lighter RSCs like H 2 S (or CH 3 SH) are often identified as the key components under various settings. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The environmental interests in reduced sulfur compounds (RSCs) have increased steadily due to their unique properties, e.g., offensive odor, toxicity, and potential corrosivity [1]. It is very important to quantify these compounds accurately and precisely for the proper assessment of their potent role in each environmental setting. There are several methods for the detection of RSCs such as gas chromatog- raphy (GC), spectrophotometry, polarography, fluorescence, coulom- etry, potentiometry, and impregnated filter tapes [2]. However, due to the combined effects of several factors (e.g., lack of sensitivity, complexity of methodology, unreliability of calibration, and the oc- currence of interfering compounds), many of these methods are found to be implausible in the application toward ambient air sam- ples [3]. Moreover, some of these methods suffer from high expenses, longer time to setup (or to operate), more analytical skills, more lo- gistic needs (such as combination with thermal desorber), or the li- cense of radioactive material treatment. For their ambient-level detection, GC with sulfur selective detection has been preferred over other options because of its excellent separation capability and high detectability [2,4,5]. A number of GC techniques have been introduced for sulfur gas analysis such as pulsed flame photometric detection (PFPD), sulfur chemiluminescence detection (SCD), and atomic emission detection (AED) [6]. Most of these detection methods have been sensitive enough to detect sulfur components at much reduced detection limits [7,8]. However, the analysis of ambient air samples still requires the enhancement of their detectability with the aid of preconcentration tools, e.g., cryofocusing (CF) and thermal desorption (TD) techniques [7]. Our study group has been involved in developing GC-based ana- lytical techniques with or without the aid of TD to precisely quantify RSCs in ambient air [9–14]. The most common difficulties one encounters in the detection of RSCs include the variable range of concentrations, high reactivity, and the complexity of matrices [15]. To resolve problems associated with the limited detectability of the instruments, their detection for environmental samples (e.g., ambient air) is inevitably aided by the use of preconcentration tools like solid adsorbents or cryogenic trap- ping [15–17]. To induce adsorption of analytes, air is first pumped through a solid sorbent. The collected analytes are then released in the next stage desorptive analysis with the aid of TD. As an alternative to solid sorbent enrichment methods, solid-phase microextraction (SPME) has been investigated intensively. Being an inexpensive solvent-free enrichment method, SPME allows the combining of sam- pling and preconcentration of analytes in a single step [18]. In fact, in a number of studies, SPME has been employed to determine RSCs in many different matrices including liquid, solid, and air samples [19–22]. Among many fiber coatings, the Carboxen–polydimethylsi- loxane (CAR–PDMS) fiber has repeatedly been demonstrated as a su- perior choice for the quantification of sulfur compounds [23–27]. In Microchemical Journal 103 (2012) 42–48 ⁎ Corresponding author. Tel.: + 82 2 499 9151; fax: +82 2 3408 4320. E-mail address: khkim@sejong.ac.kr (K.-H. Kim). 0026-265X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.microc.2012.01.005 Contents lists available at SciVerse ScienceDirect Microchemical Journal journal homepage: www.elsevier.com/locate/microc