Comparison of Solid-Phase Extraction and Solid-Phase Microextraction Using Octadecylsilane Phase for the Determination of Pesticides in Water Samples

Occurrence of organic micropollutants in municipal landfill leachate and its effective treatment by advanced oxidation processes

Landfilling is the most prominently adopted disposal technique for managing municipal solid waste across the globe. However, the main drawback associated with this method is the generation of leachate from the landfill site. Leachate, a highly concentrated liquid consisting of both organic and inorganic components arises environmental issues as it contaminates the nearby aquifers. Landfill leachate treatment by conventional methods is not preferred as the treatment methods are not much effective to remove these pollutants. Advanced oxidation processes (AOPs) based on both hydroxyl and sulfate radicals could be a promising method to remove the micropollutants completely or convert them to non-toxic compounds. The current review focuses on the occurrence of micropollutants in landfill leachate, their detection methods and removal from landfill leachate using AOPs. Pharmaceuticals and personal care products occur in the range of 10^-1 to more than 100 μg L^-1 whereas phthalates were found below the detectable limit to 384 μg L^-1, pesticides in the order of 10^-1 μg L^-1 and polyaromatic hydrocarbons occur in concentration from 10^-2 to 114.7 μg L^-1. Solid-phase extraction is the most preferred method for extracting micropollutants from leachate and liquid chromatography (LC) - mass spectrophotometer (MS) for detecting the micropollutants. Limited studies have been focused on AOPs as a potential method for the degradation of micropollutants in landfill leachate. The potential of Fenton based techniques, electrochemical AOPs and ozonation are investigated for the removal of micropollutants from leachate whereas the applicability of photocatalysis for the removal of a wide variety of micropollutants from leachate needs in-depth studies.

Porous thin-film molecularly imprinted polymer device for simultaneous determination of phenol, alkylphenol and chlorophenol compounds in water

A porous water-compatible molecularly imprinted polymer (MIP) coating using catechol as a pseudo-template and a water-soluble functional monomer (4-vinyl benzoic acid) with ethylene glycol dimethacrylate as the crosslinker was developed for extraction of phenols from environmental water samples. The MIP devices were combined with ultra high performance liquid chromatography with a photodiode array detector (UHPLC-PDA) suitable for the simultaneous determination of trace levels of phenolic compounds with a wide range of polarities -phenol, alkylphenols and chlorophenols- in seawater and produced water. Parameters that influence extraction efficiency (salinity, pH, polymer mass, desorption solvent, and desorption time) were optimized to give method detection limits (LOD) ranging from 0.1 to 2 μg L^-1 and linearity (R²>0.99) over at least three orders of magnitude for the hydrophobic phenols (e.g., 0.5-1000 μg L^-1 for 2,4,6-trichlorophenol) and ~2 orders of magnitude for the light phenols (e.g., 10-120 μg L^-1 for phenol, 5-120 μg L^-1 for methylphenols and 2-chlorophenol, 0.5-120 μg L^-1 3-methyl-4-chlorophenol and 2,4-dichlorophenol). The recoveries from authentic spiked samples ranged from 85 to 100% with %RSDs of 0.2-14% for seawater and 81-107% with %RSD of 0.1-11% for produced water. The resulting MIP-based extraction requires no pre-conditioning of the sorbent, and because the required sample size is small and sample manipulation is limited, the method is easy to multiplex for high throughput sample processing.

Electrochemically Fabricated Solid Phase Microextraction Fibers and Their Applications in Food, Environmental and Clinical Analysis

Background:

Designing an analytical methodology for complicated matrices, such as biological and environmental samples, is difficult since the sample preparation procedure is the most demanding step affecting the whole analytical process. Nowadays, this step has become more challenging by the legislations and environmental concerns since it is a prerequisite to eliminate or minimize the use of hazardous substances in traditional procedures by replacing with green techniques suitable for the sample matrix.

Methods:

In addition to the matrix, the nature of the analyte also influence the ease of creating green analytical techniques. Recent developments in the chemical analysis provide us new methodologies introducing microextraction techniques and among them, solid phase microextraction (SPME) has emerged as a simple, fast, low cost, reliable and portable sample preparation technique that minimizes solvent consumption.

Results:

The use of home-made fibers is popular in the last two decades since the selectivity can be tuned by changing the surface characteristics through chemical and electrochemical modifications. Latter technique is preferred since the electroactive polymers can be coated onto the fiber under controlled electrochemical conditions and the film thicknesses can be adjusted by simply changing the deposition parameters. Thermal resistance and mechanical strength can be readily increased by incorporating different dopant ions into the polymeric structure and selectivity can be tuned by inserting functional groups and nanostructures. A vast number of analytes with wide range of polarities extracted by this means can be determined with a suitable chromatographic detector coupled to the system. Therefore, the main task is to improve the physicochemical properties of the fiber along with the extraction efficiency and selectivity towards the various analytes by adjusting the electrochemical preparation conditions.

Conclusion:

This review covers the fine tuning conditions practiced in electrochemical preparation of SPME fibers and in-tube systems and their applications in environmental, food and clinical analysis.

Application of counter-current chromatography as a new pretreatment method for the determination of polycyclic aromatic hydrocarbons in environmental water

Counter-current chromatography (CCC) was investigated as a new sample pretreatment method for the determination of trace polycyclic aromatic hydrocarbons (PAHs) in water environmental samples. The experiment was performed with a non-aqueous binary two-phase solvent system composed of n-heptane and acetonitrile. The CCC column was first filled with the upper stationary phase, and then a large volume of water sample was pumped into the column while the CCC column was rotated at 1600 rpm. Finally, the trace amounts of PAHs extracted and enriched in the stationary phase were eluted out by the lower mobile phase and determined by gas chromatography-flame ionization detector (GC-FID) or gas chromatography-mass spectrometry (GC-MS). The enrichment and cleanup of PAHs can be fulfilled online by this method with high recoveries (84.1-103.2%) and good reproducibility (RSDs: 4.9-12.2%) for 16 EPA PAHs under the optimized CCC pretreatment conditions. This method has been successfully applied to determine PAHs in lake water where 8 PAHs were detected in the concentration of 40.9-89.9 ng/L. The present method is extremely suitable for the preparation of large volume of environmental water sample for the determination of trace amounts of organic pollutants including PAHs as studied in this paper.