Magnetic extractant with an Fe₃O₄@SiO₂ core and aqueous ammonia coating for microextraction of petroleum acids

Abstract

Magnetic aqueous ammonia (MAA) was prepared as a magnetic extractant for dispersive microextraction of petroleum acids (PAs). The amount of extractant in MAA was custom-made by a simple approach. In the MAA composed of an aqueous ammonia coating and Fe 3 O 4 @SiO 2 core, the coating is a base extractant that can selectively extract acids, while the magnetic core serves as a support to achieve dispersion as well as rapid magnetic retrieval of the extractant during the extraction processes. This is the first use of reusable, stable and modifiable Fe 3 O 4 @SiO 2 as a support instead of bare Fe 3 O 4 in a magnetic particle assisted dispersive liquid-liquid microextraction technique. The parameters that affect extraction efficiency were investigated. The sampling step as well as the desorption step can be completed in 2 min. The linear ranges are 5-5000 ng g À1 , while the limits of quantification range from 2.5 to 6.2 ng g À1. The recoveries in spiked crude oil samples are in the range of 79.1% to 112.1% with relative standard deviations less than 11.3% (intra-day) and 13.4% (inter-day). Finally, the proposed method was applied to the analysis of PAs in diluted crude oils with different maturities. In comparison to the existing methods for extraction of PAs, the proposed method provides superior performances including high throughput (12-well plate), high degree of sample clean-up, and low consumption of separation material, solvent and time.

Carboxylic Acids in Petroleum: Separation, Analysis, and Geochemical Significance

“…In 2018, we developed a magnetic aqueous ammonia (MAA) material for dispersive microextraction of CAs from crude oils. 32 Figure 3 shows the whole process of extraction. MAA consisted of an aqueous ammonia coating and a Fe 3 O 4 @SiO 2 core.…”

“…Workflow for the magnetic dispersive extraction of CAs. This figure was reproduced with permission from ref . Copyright 2018 Royal Society of Chemistry.…”

“…As a result of the low volatility and low thermal stability of CAs, derivatization is indispensable prior to GC analysis of CAs. The common derivatization reagents include diazomethane (CH 2 N 2 ), , boron trifluoride (BF 3 )/methanol (MeOH), and N - tert -butyldimethylsilyl- N -methyltrifluoroacetamide (MTBSTFA). , In 2001, Jones et al converted CAs separated from petroleum samples to corresponding methyl ester using BF 3 /MeOH, followed by GC–FID analysis. In the chromatograms of methylated CAs from undegraded oils, n -carboxylic acids were well-separated and clearly identified.…”

“…7 Sample preparation, aiming to separate and enrich CAs from petroleum samples, is often indispensable prior to instrumental analysis. Many methods, including liquid−liquid extraction, 29 solid-phase extraction, 30,31 magnetic dispersive extraction, 32 ion-exchange chromatography, 33 and ion liquid extraction, 34 have been developed for the separation of CAs. Moreover, the field has benefited from the advances in analytical instrumentation, and there are new and improved instruments and methodologies for detection of CAs, such as infrared (IR)-spectroscopy, nuclear magnetic resonance (NMR), gas chromatography (GC), liquid chromatography (LC), and mass spectrometry (MS)-based methods.…”

Synthesis of benzo[b]xanthene‐triones and tetrahydrochromeno[2,3‐b]xanthene tetraones via three‐ or pseudo–five‐component reactions using Fe3O4@SiO2/PEtOx as a novel, magnetically recyclable, and eco‐friendly nanocatalyst

“…Bare magnetite nanoparticles are susceptible to air oxidation and unstable, irreversible adsorption, and they are easily aggregated in aqueous systems with difficulty in complete desorption of compounds that are adsorbed on Fe 3 O 4 . The modified Fe 3 O 4 NPs have been extensively used for various applications such as catalyst support, which is greatly applied in organic reactions because of easy recovery (using an external magnet) . Among different coating agents, SiO 2 shell around Fe 3 O 4 NPs (Fe 3 O 4 @SiO 2 ) has attracted more attention because the SiO 2 shell can protect bare Fe 3 O 4 NPs from decomposition and bring up a nontoxic, inert, eco‐friendly, and hydrophilic surface with excellent active points for proper surface modification .…”