# Passive Sampling and Analysis of Naphthalene
## 1 Introduction
### SPME for Sampling of Vehicle Exhaust Gases  
Until now, SPME was used for sampling and quantitative analysis of PAHs in water [31], soil [32; 33; 34; 35] and in ambient air [28]. There are few studies using SPME for sampling PAHs in exhaust gases [27; 28; 29]. In previous studies [27; 28; 29], SPME fibers were used in a conventional exposed mode (i.e., SPME fiber is sampling outside of the needle housing). [PERSON] et al. (2014) reported testing eight different vehicles for exhaust emission sampling: four diesel cars, a gasoline car, heavy-duty diesel truck and two motorcycles directly in the exhaust pipe for 150 s using 7 \(\upmu\)m polydimethylsiloxane (PDMS) coating [28]. Gaseous PAHs were responsible for 73-96% of the total 26 PAHs mass in gasoline engine samples [28]. [PERSON] et al. (2009) developed a method of determination of 16 EPA PAHs concentrations in the exhaust gas of 4-cylinder, 4-stroke, turbocharged, inter-cooled, 2.2 L diesel engine involving capture of diesel PM on glass microfiber filters, followed by thermal desorption of analytes in diesel PM from filters into Tedlar bags, and then using 100 \(\upmu\)m PDMS for extraction from Tedlar bags [27]. It was found that emissions of the naphthalene were higher than those other light PAHs [27].  
[PERSON] et al. (2001) collected diesel exhaust samples from a truck using exposed 7 \(\upmu\)m PDMS SPME fiber for 1 to 16 min [29]. It was established that PAHs with lower molecular weights (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, and pyrene) were likely to be in the gas phase and adsorbed on SPME fiber. PAHs with higher molecular weights (chrysene, benzo[a]pyrene and indenopyrene) were likely to be in the solid phase and stuck on metallic parts of SPME fiber. It was suggested that solid particles were \"glued\" to PDMS coating [29]. The follow-up paper by [PERSON] et al. (2001) showed the \"glued\" immobilized single particles from diesel exhaust could be analyzed using Raman spectroscopy [36].  
Sampling with exposed SPME fiber in fast flowing gas with PM and soot could be problematic due to the possibility of mechanical damage, overloading with PM, and an inherent variability associated with analyte partitioning between PM and gas phases. In our previous research, [PERSON] et al. [37; 38], [PERSON] et al. [30], and [PERSON] et al. [29] addressed these concerns by proposing to use retracted SPME sampling for benzene, toluene, ethylbenzene and \(o\)-xylene (BTEX) in hot gas streams from syngas plant, vehicle exhaust, and phenolics, mercaptans and a heterocyclic amine in potentially infectious process reactor air. [PERSON] et al. [30] and [PERSON] et al. [39] showed that the adsorption to metallic surfaces of SPME assembly is significant, reproducible, yet can be controlled and accounted for. Adsorption to metallic SPME assemblies is likely more of a concern for PAHs but was not assessed before.  
SPME technology is relatively simple, time-saving, and solventless. Sampling, extraction, concentration and the introduction of the sample are reduced into one-step. This decreases cost, reduces need for highly-skilled analysts and equipment requirements, and can increase the sensitivity of the analysis. These advantages of SPME, i.e., acceptable analytical performance at low cost, can be attractive for scientists and engineers studying air pollution at low budgets. Thus, the selection of SPME as an alternative approach can provide simpler and more efficient determination of TWA naphthalene in exhaust gases of internal combustion engines.