Octadecylsilane and multiwall carbon nanotubes based cellulose triacetate mixed matrix membrane for new microextraction approaches

Abstract

Widespread use of pharmaceuticals and herbicides leads to accumulation of their residues in surface water with detrimental effects and they have been recognized as emerging environmental pollutants. Therefore, it is important to develop a suitable sample pre-treatment method for the determination of these compounds in water. In this study, the fabrication of a mixed matrix membrane (MMM) using carbonaceous material immobilized in cellulose triacetate polymer matrix for microextraction is reported. The applicability and reliability of utilizing carbonaceous-based MMM in two different miniaturised microextraction designs, namely dynamic MMM tip extraction and automated flow-through MMM microextraction, are comprehensively demonstrated. To evaluate the performance of dynamic MMM tip extraction, the developed approach was applied for determination of five selected nonsteroidal anti-inflammatory drugs (NSAIDs) namely indoprofen, sulindac, naproxen, diclofenac, and ibuprofen in sewage water samples prior to ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis. The established method showed good linear responses in the concentration range of 0.25–500 pg/mL with correlation coefficients (r) from 0.9988 to 0.9992. The limits of detections (LODs) were 0.08–0.40 pg/mL. The relative recoveries of NSAIDs from spiked water samples were in the range of 92–99% and exhibited excellent precision (relative standard deviations, RSDs ≤ 4.9%). The proposed analytical methodology allowed pre-concentration factors up to 250. Automated flow-through MMM microextraction approach was developed for the analysis of six chlorophenoxy acid herbicides, namely 2-(4-chlorophenoxy)acetic acid, 2-(3,4-dichlorophenoxy)acetic acid, 2-(2,4-dichlorophenoxy)acetic acid, 2-(4-chloro-2-methylphenoxy)acetic acid, 2-(2,4,5-trichlorophenoxy)acetic acid, and 4-(2,4-dichlorophenoxy)butanoic acid in the spiked sewage water sample prior to high performance liquid chromatography-ultraviolet detection (HPLC-UV) analysis. Under optimum conditions, the linearity of this method ranged from 50 - 1000 ng/mL with correlation coefficients (r) ≥ 0.9939, while LODs ranged from 15 - 20 ng/mL. The recoveries of the compounds in spiked sewage water samples were from 95% to 99% with RSDs ≤7.5% and enrichment factors of 19 to 55. The developed analytical methodology has the advantage of requiring less adsorbent (only 62.5 μg) and less organic reagent (60 μL of desorption solvent).