Passive Sampling and Analysis of Naphthalene in Internal Combustion Engine Exhaust with Retracted SPME Device and GC-MS

Abstract

Exhaust gases from internal combustion engines are the main source of urban air pollution. Quantification of Polycyclic aromatic hydrocarbons (PAHs) in the exhaust gases is needed for emissions monitoring, enforcement, development, and testing of control technologies. The objective was to develop quantification of gaseous naphthalene in diesel engine exhaust based on diffusion-controlled extraction onto a retracted solid-phase microextraction (SPME) fiber coating and analysis on gas chromatography-mass spectrometry (GC-MS). Extraction of naphthalene with retracted fibers followed Fick's law of diffusion. Extracted mass of naphthalene was proportional to C g , t, D g , T and inversely proportional to Z. Method detection limit (p = 0.95) was 11.5 ppb (0.06 mg·m −3 ) at t = 9 h, Z = 10 mm and T = 40 • C, respectively. It was found that the % mass extracted of naphthalene by SPME needle assembly depended on the type of fiber. Storage time at different temperatures did not affect analyte losses extracted by polydimethylsiloxane (PDMS) 100 µm fiber. The developed method was tested on exhaust gases from idling pickup truck and tractor, and compared side-by-side with a direct injection of sampled exhaust gas method. Time-weighted average (TWA) concentrations of naphthalene in exhaust gases from idling pickup truck and a tractor ranged from 0.08 to 0.3 mg·m −3 (15.3-53.7 ppb).

Optimization of Time-Weighted Average Air Sampling by Solid-Phase Microextraction Fibers Using Finite Element Analysis Software

“…To date, all published research on TWA-SPME has used Equation (1) as the basis of quantification [ 3 , 4 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ] of VOCs in an outdoor air, laboratory air, pyrolysis reactor air, engine exhaust, and process air. Equation (1) predicted measured gas concentrations with reasonable accuracy and precision.…”

“…Woolcock et al [ 17 ] reported a significant departure from the zero-sink assumption and from Equation (1) suggesting “apparent” diffusion coefficient ( D ) dependent on both sampling time ( t ) and retraction depth ( Z ). Baimatova et al [ 11 ] reported significant differences in the extracted mass of naphthalene gas for different SPME coatings, i.e., that Equation (1) does not incorporate. Recent research by Tursumbayeva [ 20 ] shows that the discrepancy between Equation (1) and experimental data are amplified when a wide-bore glass liner is used for passive sampling with SPME fiber retracted inside it.…”

Optimization of Time-Weighted Average Air Sampling by Solid-Phase Microextraction Fibers Using Finite Element Analysis Software

“…The increase of analyte concentration in the air near the fiber tip results in the decrease of the analyte flux (i.e., the mass of analyte entering protecting needle per cross-sectional area and time) from the sampled air with time. This affects the sampling rate, which was previously assumed to be constant [3,4,[8][9][10][11][12][13][14][15][16][17].…”

“…To date, all published research on TWA-SPME used Eq. 1as the basis of quantification [3,4,[8][9][10][11][12][13][14][15][16][17] of VOCs in laboratory air, pyrolysis reactor air, engine exhaust, and process air. Eq.…”

“…Baimatova et al [9] reported significant differences in the extracted mass of naphthalene gas for different SPME coatings, i.e., that Eq. (1) does not incorporate.…”