Head space voltammetry: A novel voltammetric method for volatile organics and a case study for phenol K. Volkan O ¨ zdokur a , Levent Pelit a,n , Hasan Ertas - a , Suna Timur b , F. Nil Ertas - a a Ege University, Faculty of Science, Department of Chemistry, Izmir, Turkey b Ege University, Faculty of Science, Department of Biochemistry, Izmir, Turkey article info Article history: Received 3 February 2012 Received in revised form 5 June 2012 Accepted 15 June 2012 Available online 27 June 2012 Keywords: Voltammetry Head space analysis Polypyrrole Phenol Electropolymerization abstract Present paper describes the results of a novel method which combines the Head space (HS) preconcentration of the analyte on the electrode prior to the voltammetric analysis. Thereafter, the method was called HS-Voltammetry. The performance of the method was tested upon using an electroactive and volatile molecule, phenol molecule, which gives an oxidation peak at conventional electrodes. In this study, a glassy carbon electrode was modified with polypyrrole by electropolymer- ization and then, the electrode was placed over the solution in a sealed vial heated gently on a hotplate with a stirrer for phenol determination. By controlling the thickness of the polymeric coating and optimizing preconcentration parameters such as vial pH and temperature, stirring rate and exposure time, a very consistent (5.2% at 5.0  10 7 M) fraction of the analyte can be extracted during a predetermined time. The oxidation peak current at 0.8 V depended linearly on the phenol concentration over a wide range (3 orders of magnitude). The detection limit was estimated as 7.0  10 8 M at 60 1C (S/N¼3) which is well below the limit set by the European Community for phenols in wastewaters (ca. 5  10 6 M). The effect of other phenolic compounds was also examined and it was shown that head space preconcentration eliminated the interference of non-volatile phenolic acids studied. For volatile phenolic compounds, the selectivity can be maintained in cases when isolated peaks are obtained for each component. The proposed method has been applied successfully for the determina- tion of phenol in artificial wastewater and recovery percentage was calculated as 93%. & 2012 Elsevier B.V. All rights reserved. 1. Introduction In trace analyses, the preconcentration of the analyte plays a vital role in terms of sensitivity, and in some cases, the selectivity. In stripping techniques, this step usually includes an electroche- mical deposition process on the electrode surface at a controlled potential under stirred conditions [1]. Despite the wide applica- tion of electroanalytical techniques, the selectivity of the methods suffers from the interference of electroactive impurities in the matrices and the electrode performance is usually impaired by the presence of surface active materials [2]. Head Space (HS) techniques, on the other hand, provide a practical tool for determination of volatile organic compounds by simply eliminating any interference from non-volatile components of the sample [3]. In HS sampling, the sample is heated in a sealed vial until the volatile compounds reach the equilibrium with the gas phase above the liquid. The analytes can be selectively preconcen- trated on a solid [4] or liquid phase [5] and subsequent detection of target analyte is generally performed by chromatographic techni- ques. When it is combined with a solid phase micro extraction (SPME) fiber, this solventless technique endow with analyte/matrix separation and preconcentration for volatile organic compounds [3]. The technique is particularly practical for complex matrixes such as wastewaters and clinical samples as many interference problems are eliminated since the fiber is not in contact with the sample [6,7]. Present study includes the earliest results of a novel method which combines the HS preconcentration of the analyte in the polymeric coating on a glassy carbon electrode (GCE) prior to the voltammetric analysis. Thereafter, the method was called HS- Voltammetry. Phenol being a semi-volatile and electroactive molecule was chosen to test the effectiveness of the method. Phenol and a considerable number of its derivatives are important toxic compounds and are extensively used in several industrial processes such as plastics, dyes, pesticides, papers, and petrochemical products [8]. As a result, phenols are often detected in water, soil and sediment samples [9–14]. Owing to their poor biodegradability, high toxicity and ecological aspects, phenolic compounds have been included in the US Environmental Protec- tion Agency (EPA) list of priority pollutants that should be monitored in the environment [15]. Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/talanta Talanta 0039-9140/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.talanta.2012.06.032 n Corresponding author. Tel.: þ90 232 3112389; fax: þ90 232 3888264. E-mail address: levent.pelit@ege.edu.tr (L. Pelit). Talanta 98 (2012) 34–39