Determination of N-nitrosamines in water resources using Al-AC sorbent for stir-bar supported micro-solid-phase extraction coupled with gas chromatography mass-spectrometry

This work presents the synthesis of a simple, cheap and an effective sorbent for the extraction of polar nitrosamines from aqueous samples. The sorbent was prepared by the loading of aluminum on activated carbon (Al-AC) and characterized by Fourier transform infrared (FTIR), Raman spectroscopy, and thermogravimetry analysis. The simple sorbent material was then utilized in membrane protected stir-bar supported micro-solid-phase extraction (SB-μ-SPE) to preconcentrate nitrosamines (NA) from various types of aqueous samples. Furthermore, the extracted analytes were analyzed using gas chromatography mass spectrometry. The extraction process parameters were optimized including choosing the best sorbent, mass of that sorbent, time for extraction and desorption, stirring rate during extraction, type of desorption solvent and its volume, and the effect of adding salt to the aqueous sample. The extraction and chromatographic method have shown a wide linear range of 10 to 1000 ng mL⁻¹ with an r² ranging from 0.9912 to 0.9986. This method can analyze polar nitrosamines with LOD in the range of 0.8 to 3.3 ng mL⁻¹. The reproducibility was tested at three concentration levels from the linear range and found to be in the range of 4.0 to 6.6%. To evaluate the method applicability in a real matrix, the relative recoveries in wastewater, seawater, and drinking water were tested and found to be between 85% and 104.2%.