Measurement Uncertainty in the Analysis of Selected Polycyclic Aromatic Hydrocarbons in Environmental Water By Magnetic Molecularly Imprinted Polymer-Based Micro-Solid Phase Extraction- Liquid Chromatography

Sample preparation is important to produce a clean extract to enhance detection sensitivity and minimize instrument maintenance. A micro-solid phase extraction (µ-SPE) technique using magnetic molecularly imprinted polymers (magnetic-MIPs) as the adsorbents combined with micro-high performance liquid chromatography and ultraviolet detection (µ-HPLC-UV) has been developed for the determination of selected polycyclic aromatic hydrocarbons (PAHs), namely benzo[a]pyrene, phenanthrene, fluoranthene and pyrene in environmental water samples. The magnetic-MIPs were characterized using scanning electron microscopy, Brunauer–Emmett–Teller, thermogravimetric analysis and vibrating sample magnetometer to finalize the physical properties of the magnetic-MIPs. The µ-SPE was then optimized using one variable at a time approach to enhance the extraction efficiency. Under the optimal extraction conditions, the feasibility of using magnetic-MIPs as the adsorbents for the extraction of the selected PAHs was proven with a wide linearity range (5-250 µg L-1), good repeatability (relative standard deviation <10%), ultra-trace detection limits (0.01-0.02 µg L-1) and good relative recovery (80.2-119.3%) for the application in the environmental water. The doubt of using the µ-SPE was investigated by calculating the measurement uncertainty. The estimated combined standard uncertainties for the determination of the selected PAHs were in the range of 0.0678-0.0890. It was concluded that the uncertainty of the µ-SPE-µ-HPLC-UV is mainly attributed to its accuracy. Nevertheless, the results showed that the measurement uncertainty of the proposed magnetic-MIPs-based µ-SPE-µ-HPLC-UV was at an acceptable level. The method is beneficial to the routine analysis, especially in providing simple and sensitive determination of the selected PAHs in environmental water. The µ SPE technique consumes minimal amounts of solvent and traces of adsorbents, which then greatly minimizes the waste and analysis costs in routine analysis. (author)