Development of a single format membrane assisted solvent extraction-molecularly imprinted polymer technique for extraction of polycyclic aromatic hydrocarbons in wastewater followed by gas chromatography mass spectrometry determination

Fabrication of a surface molecularly imprinted polymer membrane based on a single template and its application in the separation and extraction of phenytoin, phenobarbital and lamotrigine

An innovative molecularly imprinted polymer membrane (MIPM) was prepared with polyvinylidene difluoride (PVDF) as the support, phenytoin (PHT) as the single template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linking reagent, azobisisobutyronitrile as the initiator, and acetonitrile-dimethylformamide (1 : 1.5, v/v) as the porogen. These materials were characterized via scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller measurements and X-ray photoelectron spectroscopy. Their adsorption performances were evaluated through a series of experiments including isothermal adsorption, kinetic adsorption, selective adsorption, adsorption-desorption, reusability, and preparation reproducibility. Additionally, the application was explored by investigating the extraction recovery of MIPMs towards PHT, phenobarbital (PHB) and lamotrigine (LTG) in different matrices including methanol, normal saline (NS), phosphate buffer solution (PBS) and plasma. The results showed that MIPMs with rough and porous surfaces were successfully constructed, which offered good preparation reproducibility, reusability and selectivity. The adsorption capacities of MIPMs towards PHT, PHB and LTG were 2.312, 2.485 and 2.303 mg g-1, respectively, while their corresponding imprinting factors were 8.538, 12.122 and 4.562, respectively. The adsorption equilibrium of MIPMs was achieved within 20 min at room temperature without stirring or ultrasonication. The extraction recoveries of MIPMs for PHT, PHB or LTG in methanol, NS and PBS were more than 80% with an RSD% value of less than 3.64. In the case of plasma, the extraction recovery of MIPMs for PHT and PHB was more than 80% with an RSD% value of less than 2.41, while that of MIPMs for LTG was more than 65% with an RSD% value of less than 0.99. All the results indicated that the preparation method for MIPMs was simple, stable, and reliable, and the prepared MIPMs possessed excellent properties to meet the extraction application of PHT, PHB and LTG in different matrices.

Ultrasound assisted membrane-assisted solvent extraction for the simultaneous assessment of some drugs involved in drug-facilitated sexual assaults by liquid chromatography-tandem mass spectrometry

A simple and highly efficient ultrasound assisted membrane-assisted solvent extraction (MASE) pre-treatment method for urine has been developed and validated for the simultaneous determination of twenty-two drugs involved in drug-facilitated sexual assaults (DFSAs) by liquid chromatography-tandem mass spectrometry. MASE was performed with 4.0 mL of urine (pH adjusted at 12), 400 μL of hexane as an organic solvent inside the polypropylene membrane, and ultrasonication (45 kHz, 120 W) for 10 min. A pre-concentration factor of 40 was achieved after evaporation (N2 stream) and re-dissolution in 100 µL of methanol. Analytes were separated using a Zorbax Eclipse Plus C18 column under gradient elution with aqueous 10 mM NH4HCO3 (pH 8.0) and methanol as mobile phases. Matrix-matched calibrations allowed the assessment of DFSA drugs of quite different octanol-water partition coefficients (Ko/w), from 1.32 101 for pregabalin to 2.45 105 for clomipramine (Log P values from 1.12 (pregabalin) to 5.39 (clomipramine)). The limit of detection (LOD) was between 0.0075 to 0.37 µg L-1, with analytical recoveries ranging from 73 to 103%, and relative standard deviations (RSDs) within the 2-20% range. The applicability of the method was demonstrated after analysing urine samples under forensic investigation.

Isolation and quantification of synthetic cannabinoid receptor agonists in human urine using membrane-assisted solvent extraction followed by liquid chromatography-tandem mass spectrometry

The global market for new psychoactive substances (NPSs) continues to expand, and the range of drugs available on the market has probably never been wider. Synthetic cannabinoids (SCRAs) constitute the largest family of NPSs, and they go unnoticed during illicit drug market control and during routine toxicological-forensic analysis. Membrane-assisted solvent extraction (MASE) has been a novelty proposed for the simultaneous extraction of SCRAs, and urine has been selected as a model forensic-clinical sample. Isolated SCRAs were further determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). An optimised sample pre-treatment procedure consists of using 400 μL of n-hexane as an extraction phase placed inside a polypropylene (PP) membrane, adjusting the donor phase (urine) at a pH value of 5.9. Extraction was assisted by mechanical (orbital-horizontal) stirring in a temperature-controlled chamber at room temperature for 20 min. n-Hexane extracts were evaporated to dryness and re-suspended in 100 μL of mobile phase, which leads to a pre-concentration factor of 50. Method validation showed analytical recoveries higher than 80% for most SCRAs and repeatability (inter-day and intra-day assays) with RSD values lower than 20%. The proposed method was found to be selective and sensitive and limits of quantification (LOQs) between 0.10 and 1.0 μg L^-1 were achieved.

Multivariate optimization of a two-way technique for extraction of pharmaceuticals in surface water using a combination of membrane assisted solvent extraction and a molecularly imprinted polymer

This work demonstrates development and evaluation of a two-way technique based on the combination of membrane assisted solvent extraction and a molecularly imprinted polymer (MASE-MIP) for selective and efficient extraction of five selected pharmaceuticals belonging to five different therapeutic classes. The pharmaceuticals were extracted from surface water samples followed by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-qTOF/MS) determination. A central composite design was applied to optimize the influence of the sample salt content, the stirring rate, the stirring time and the amount of MIP on the extraction of an anticonvulsant (carbamazepine), a cardiac stimulant (etilefrine), a muscle relaxant (methocarbamol), an antiretroviral (nevirapine) and an antidepressant (venlafaxine) from surface water. Optimization of the analytical method was performed by spiking water with a mixture of all five pharmaceuticals at 500 ng mL^-1. Optimum extraction conditions for a sample volume of 18 mL were found to be 5 g of salt content, a stirring rate of 400 rpm, an extraction time of 60 min and 50 mg of MIP. The MASE-MIP-LC-qTOF/MS method gave detection and quantification limits ranging from 0.09 to 0.20 ng mL^-1 and 0.31-0.69 ng mL^-1, respectively. The spiked river water samples yielded recoveries ranging from 38 to 91% for the selected model compounds belonging to the five classes of pharmaceuticals. Upon the application of the developed analytical method in water analysis, all selected pharmaceuticals were detected in South African river water with nevirapine and venlafaxine being more prominent attaining the maximum concentrations of 1.64 and 2.48 ng mL^-1, respectively.

Trends in Innovations and Recent Advances in Membrane Protected Extraction Techniques for Organics in Complex Samples

Membrane protected extraction is an ongoing innovation for isolation and pre-concentration of analytes from complex samples. The extraction process, clean-up and pre-concentration of analytes occur in a single step. The inclusion of solid sorbents such as molecularly imprinted polymers (MIPs) after membrane extraction ensures that selective double extraction occurs in a single step. The first step involves selective extraction using the membrane and diffused analytes are trapped on the solid sorbent enclosed in the membrane. No further clean-up is required even for very dirty samples like plant extracts and wastewaters samples. Sample clean-up occurs during extraction in the first process and not as additional step since matrix components are prevented from trapping on the sorbent. This can be referred to as prevention is better than cure approach. In this work, the analytical methods that employed membrane protected extraction for various organics such as pesticides, polycyclic aromatic hydrocarbons, and pharmaceuticals are reviewed. The designs of these analytical methods, their applications, advantages and drawbacks are discussed in this review. Literature suggests that the introduction of solid sorbents in membrane creates the much-needed synergy in selectivity. Previous reviews focused on membrane combinations with MIPs while discussing micro-solid-phase extraction. The scope of this review was broadened to include other sample preparation aspects such as membrane protected stir bar solvent extraction and membrane protected solid-phase microextraction. In addition, novel sample preparation methods for solid samples which include Soxhlet membrane protected molecular imprinted solid phase extraction and membrane protected ultra sound assisted extracted are discussed.

Synthesis of hypercrosslinked polymers for efficient solid-phase microextraction of polycyclic aromatic hydrocarbons and their derivatives followed by gas chromatography-mass spectrometry determination

Three novel hypercrosslinked polymers (HCPs) were synthesized via Friedel-Crafts reaction employing 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene as alkylating agent, and triphenylbenzene, tetraphenylethylene and p-quaterphenyl as the aromatic units, respectively. The prepared HCPs were applied as solid-phase microextraction coatings for direct immersion extraction of polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives in environmental water samples. The key factors affecting the extraction efficiency including extraction time, extraction temperature, stirring rate, ionic strength and desorption conditions, were carefully studied. Coupled with gas chromatography mass spectrometry analysis, a new method for determining PAHs and their derivatives was developed. Under the optimized conditions, the limits of detection (S/N=3) and limits of quantitation (the lowest concentration for quantification) of the method were in the range of 2.5-25.0 and 7.5-75.0 ng L^-1, respectively. The recoveries of spiked samples were in the range of 73.1-118.3% with relative standard deviations less than 13.0%. The developed method was applied for the simultaneous determination of nine PAHs and their derivatives in environmental water samples, showing good accuracy and reliability.

Highly efficient porous sorbent derived from asphalt for the solid-phase extraction of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are generated primarily during the incomplete combustion of organic matter and are ubiquitous environmental pollutants. For the first time, in this study, a mesoporous carbon derived from asphalt with high surface area (2300 m²g^-1 with an average of 1.2 cm³ g^-1) was utilized as a sorbent for the solid-phase extraction (SPE) of several PAHs in tap water samples. The factors influencing the extraction capability of the new material were investigated and the optimum conditions were determined to be as follows: Sample volume - 200 mL, no adjustment of sample pH, and sorbent amount - 50 mg. Under the most favorable SPE conditions, with gas chromatography-mass spectrometric analysis, the method exhibited a linear range of 0.5-50 μgL^-1 with limits of detection between 0.004 and 0.026 μgL^-1. The recoveries obtained from spiked tap water samples spiked at 1 μgL^-1 and 5 μgL^-1, were in the range 86.7-98.2% with relative standard deviations of <9%. The method was also applied to tap water samples collected from the local environment. The concentrations of PAHs detected ranged between 0.13 and 48 μgL^-1. The reusability of the sorbent was tested with five consecutive SPE extraction, and no carryover of analytes was observed.

Green Approaches to Sample Preparation Based on Extraction Techniques

Preparing a sample for analysis is a crucial step of many analytical procedures. The goal of sample preparation is to provide a representative, homogenous sample that is free of interferences and compatible with the intended analytical method. Green approaches to sample preparation require that the consumption of hazardous organic solvents and energy be minimized or even eliminated in the analytical process. While no sample preparation is clearly the most environmentally friendly approach, complete elimination of this step is not always practical. In such cases, the extraction techniques which use low amounts of solvents or no solvents are considered ideal alternatives. This paper presents an overview of green extraction procedures and sample preparation methodologies, briefly introduces their theoretical principles, and describes the recent developments in food, pharmaceutical, environmental and bioanalytical chemistry applications.

Applications of Green Chemistry Approaches in Environmental Analysis

Background:

Green chemistry is the application of methodologies and techniques to reduce the use of hazardous substances, minimize waste generation and apply benign and cheap applications.

Methods:

In this article, the following issues were considered: greener solvents and reagents, miniaturization of analytical instrumentation, reagent-free methodologies, greening with automation, greener sample preparation methods, and greener detection systems. Moreover, the tables along with the investigated topics including environmental analysis were included. The future aspects and the challenges in green analytical chemistry were also discussed.

Results:

The prevention of waste generation, atomic economy, use of less hazardous materials for chemical synthesis and design, use of safer solvents, auxiliaries and renewable raw materials, reduction of unnecessary derivatization, design degradation products, prevention of accidents and development of real-time analytical methods are important for the development of greener methodologies.

Conclusion:

Efforts should also be given for the evaluation of novel solid phases, new solvents, and sustainable reagents to reduce the risks associated with the environment. Moreover, greener methodologies enable energy efficient, safe and faster that reduce the use of reagents, solvents and preservatives which are hazardous to both environment and human health.