Validation and sensitivity evaluation of the ID-GC-TOF-MS method for determination of PAHs in biogas

Abstract

Abstract:In this study, an ID-GC-TOF-MS method was developed and validated for polycyclic aromatic hydrocarbons (PAHs) by spiking solutions onto thermal desorption tubes using calibration solution loading ring (CSLR) apparatus and sweeping them by the aid of air stream. Once the method was developed and validated, the effect of other compounds found in biogas and biomethane was investigated by the same methodology used in method development by using a gravimetrically prepared biogas mixture consisting of 45% methane, 40% carbon dioxide and 15% nitrogen. There are standard reference methods for measurements of PAHs in air but there was no available standard method for PAHs in biogas and biomethane yet. This study provides a basis for the future studies to develop a standard method. Data obtained through this study showed that present method is not affected by the compounds found in biogas that are not present in other matrices such as ambient air.Keywords: PAH; biogas; biomethane; thermal desorption; isotope dilution; GC-TOF-MS. © 2017 ACG Publications. All rights reserved. Sample SourcePolycyclic aromatic hydrocarbon (PAH) calibration solutions of consisting benzo[a]anthracene, benzo[a]pyrene and naphthalene were prepared from individual stock solutions that were prepared gravimetrically from high purity solid standards. Purities of solid standards were determined by quantitative nuclear magnetic resonance (qNMR) purity assessment protocol developed in TUBITAK UME [1]. Previous StudiesBiogas is a valuable renewable energy produced from anaerobic digestion of sewage sludge, commercial composting, animal manure, residue landfill, waste biogasification and agro-zootechnical digestion in mesophilic (35 ºC) and thermophilic (55 ºC) conditions [2][3][4]. The process of biogas production takes place in four steps; hydrolysis, acidification, formation of acetic acid and formation of methane. Raw biogas comprise methane (40-70%), carbon dioxide (30-45%), nitrogen (0-15%) and inorganic and organic contaminants [2]. Upgraded biogas, known as biomethane, contains at least 95 % methane and less than 2.5 % carbon dioxide.