Trace analysis of phenolic compounds in water by in situ acetylation coupled with purge and trap-GC/MS

Abstract

The purge-and-trap preconcentration of phenolic compounds from waters after in situ acetylation was carried out in order to quantify them by Gas Chromatography/Mass Spectrometry (GC/MS) in selected ion monitoring (SIM) mode. Using spiked natural surface water, various parameters including purge method, derivatization reagent (acetic anhydride), pH adjuster (Na2HPO4), temperature and time of derivatization reaction, amount of inert salt (NaCl) added, purge time and desorb temperature have been investigated. The final optimized preconcentration conditions were as follows: 10.0 g of NaCl, 0.40 g of Na2HPO4 and 400 μL of acetic anhydride were added to a 35 mL sample which then was heated at 55 °C for 20 min and purged for 20 min while the trap remained at room temperature. Once the purge step was over, the trap was desorbed at 260 °C for 2 min and then baked at 270 °C for 6 min. Under these optimized conditions, the precision and detection limits for all target compounds ranged from 1.3 to 7.0% (relative standard deviation, RSD) and from 0.06 to 0.12 μg L−1, and recoveries from the river water sample and wastewater sample ranged from 87.3 to 111% for all analytes. The response was found to be linear in the validated range, with the correlation coefficient (R2) better than 0.998. Finally, the method had been utilized for determination of phenolic compounds in natural surface water and wastewater samples, which suggested that it is a useful and effective method for the routine analysis of trace-level phenolic compounds in water.