Headspace SPME followed by GC/PFPD for the analysis of malodorous sulfur compounds in liquid industrial effluents

Abstract

Headspace SPME was used to analyse malodorous sulfur compounds in liquid industrial effluents. A pulsed flame photometric detector (PFPD) was selected for a specific and sensitive analysis. Two fibres, PDMS/Dvb and PDMS/Carboxen, which are particularly convenient for extracting small and volatile molecules were tested. To compare these fibres, both sensitivity and artefact formation were considered. The PDMS/Carboxen fibre showed the lower limits of detection and moreover the least artefact formation yields. It was therefore selected and headspace SPME extraction conditions were optimised. Limits of detection of the target compounds evaluated were 12-31 ng L(-1) and repeatability was around 7%. Due to the adsorption mechanism involved, extraction is strongly influenced by the sample matrix and the low affinity compounds can suffer displacement effects. To investigate the occurrence of this phenomenon, two sampling times corresponding to non-equilibrium (5 min) and equilibrium conditions (60 min) were investigated. An external calibration was carried out by using standard solutions for both sampling times. The developed procedure was then compared to the standard addition method on a real industrial effluent. The results obtained from the two methods and for the two extraction times were in good agreement, demonstrating that even a long sampling time can be used. Therefore, the simple and timesaving external calibration was defined as relevant for an accurate quantification of sulfur compounds by headspace SPME.

Degradation of dimethyl disulfide using homogeneous Fenton's reaction

“…The vial was placed in a water bath at 50 • C. Magnetic stirring was used to increase the transfer of the volatile compound from the liquid phase to the headspace. This procedure increases the adsorption of the compounds in the SPME fibers and reduces the time necessary for the extractions [6][7][8][9]. The extraction conditions were determined in preliminary experiments (results not shown).…”

“…This compound was chosen, since it is found in wastewaters from the poultry by-products industry, and for its low odor threshold (sub-g m −3 ) [6]. A 0.025 mg L −1 solution of DMDS was prepared with deionized water before every experimental run.…”

Measurement and assessment of odorous sulfur compounds

“…Solid phase microextraction (SPME) is one of the most popular methods for odour collection. SPME has been widely used in beverage, food, and environmental assessments (Antoniou et al, 2007;Cai et al, 2006a;Campillo et al, 2009;Hill & Smith, 2000;Lestremau et al, 2004a;Lestremau et al, 2004b;Salgado-Petinal et al, 2005). In SPME, analytes from samples are extracted using an exposed fibre coated with an extracting phase (liquid or solid).…”

“…Many studies have been conducted into the use of different SPME fibres for VSC sampling and analysis. The most common SPME fibres include Carboxen/polydimethylsiloxane (CAR/PDMS) (Antoniou et al, 2007;Campillo et al, 2009;Haberhauer-Troyer et al, 1999;Hill & Smith, 2000;Lestremau et al, 2004a), divinylbenzene/ polydimethylsiloxane (DVB/PDMS) (Antoniou et al, 2007;Cai et al, 2006a;Hill & Smith, 2000;Lestremau et al, 2004b), polydimethylsiloxane (PDMS) (Antoniou et al, 2007;Hill & Smith, 2000;Salgado-Petinal et al, 2005), polyacrylate (PA), Carboxen/divinylbenzene/polydimethylsiloxane (CAR/DVB/ PDMS) (Antoniou et al, 2007;Campillo et al, 2009;Salgado-Petinal et al, 2005), and Carbowax/divinylbenzene (CW/DVB) (Antoniou et al, 2007; Salgado- Petinal et al, 2005). A potential SPME fibre with good application for sulfur analysis is graphene-supported zinc oxide (ZnO) as described by Zhang et al (2012), however further research is required to optimise this new technology within the context of complex odours (Zhang et al, 2012).…”

“…seriously affected by the sample matrix with regard to levels of oxygen, humidity, and alcohol on SPME extraction of VSCs and also due to the significant bias of extraction between light and heavy VSCs (Cai et al, 2006b;Campillo et al, 2009;Haberhauer-Troyer et al, 1999;Kabir & Kim, 2012;Lestremau et al, 2004b;Lopez et al, 2007;Mochalski et al, 2009;Murray, 2001;Nielsen & Jonsson, 2002). To correct this, several authors suggest standard "additions" to the SPME process to determine its VSC extraction efficiency, but this is time consuming and does not wholly restore the method's accuracy (Kabir & Kim, 2012;Mochalski et al, 2009;Murray, 2001).…”