Application of dispersive liquid-liquid microextraction for the determination of phenylurea herbicides in water samples by HPLC-diode array detection

Construction of hydroxyl functionalized magnetic porous organic framework for the effective detection of organic micropollutants in water, drink and cucumber samples

Organic micropollutants have been extensively detected in environmental waters, posing severe hazards to organisms and humans. Effective detection of micropollutants in environmental water and food samples is of significant importance. Herein, a novel magnetic porous organic framework (labeled as M-Qu-POF) was synthesized using natural quercetin as building units via a facile azo-coupling reaction for the first time. Featuring with good magnetism, intrinsic porosity, high surface area and hydrophilic-lipophilic (amphiphilic) structure, the M-Qu-POF displayed high adsorption capacity for phenylurea herbicides (PUHs) pollutants. The adsorption mechanism was investigated by theory calculation, confirming that the hydrogen bonds interaction, π-π interactions and electrostatic interactions play an important role in the adsorption. With the M-Qu-POF as adsorbent, a magnetic solid phase extraction-high performance liquid chromatography method was first established for simultaneous enrichment and detection of six PUHs in environmental water, tea drink and cucumber samples. Under the optimized experimental conditions, good linear range, low detection limits and high enrichment factors were obtained. The method was successfully applied for determination of PUHs in environmental water, tea drink and cucumber samples with satisfactory recoveries (80.0-118%). The result demonstrates that the M-Qu-POF material has a good application prospect in the detection of other organic micropollutants.

Analysis of fluorinated compounds by micellar electrokinetic chromatography - mass spectrometry

Micellar electrokinetic chromatography (MEKC) is a good separation technique with high efficiency, high selectivity and simple preparation process. Hyphenation of MEKC with mass spectrometry (MS) could extend its application in complex sample analysis. However, direct coupling MEKC using commonly used surfactants like sodium dodecyl sulfate (SDS) with ESI-MS will lead to strong signal suppression. In this work, a MEKC-MS method using volatile ammonium perfluorooctanoate as surfactant was developed. The MS compatibility of ammonium perfluorooctanoate was investigated. The result revealed that there is no signal suppression even the concentration of ammonium perfluorooctanoate was up to 300 mM. Meanwhile, we found that ammonium perfluorooctanoate used as surfactant in MEKC provided powerful F-F interaction and hydrophobic interaction, which was beneficial for separation of fluorinated compounds. Using the ammonium perfluorooctanoate based MEKC method, several groups of fluorinated compounds, which cannot be separated using non-fluorinated surfactants like lauric acid and SDS based MEKC method, were baseline separated. Finally, the MEKC-ESI-MS method was successfully applied for analysis of two herbicides including fluometuron and fenuron in lake water samples with high separation efficiency, high sensitivity, good linearity and reproducibility.

A magnetic covalent aromatic polymer as an efficient and recyclable adsorbent for phenylurea herbicides

A magnetic covalent aromatic polymer (Fe₃O₄-NH₂-CAP) was synthesized by grinding a covalent aromatic polymer (CAP) and amino-functionalized magnetic nanoparticles (Fe₃O₄-NH₂ NPs). The CAP was prepared by a Friedel-Crafts reaction between biphenyl and 1,3,5-benzenetricarbonyl trichloride. The interaction in the Fe₃O₄-NH₂-CAP is based on hydrogen bond formation between the carbonyl groups in the CAP and the amino groups in the Fe₃O₄-NH₂ NPs. The adsorbent inherits the advantages of the CAP and also has the superior magnetic property of the Fe₃O₄ NPs. The adsorbent was applied to magnetic solid-phase extraction of six phenylurea herbicides (metoxuron, monuron, chlortoluron, isoproturon, monolinuron, buturon) from soil and water samples. Following elution with 600 μL methanol, the herbicides were quantified by HPLC. The calibration plots are linear in the 1.00-100 ng g^-1 herbicide concentration ranges in case of spiked soil samples, and in the 0.10-40 ng mL^-1 concentration range for spiked water samples. The limits of detection range from 0.3 to 0.5 ng g^-1 (soil) and from 0.01 to 0.03 ng mL^-1 (water), with relative standard deviations of <8.0% and < 6.9%, respectively. Graphical abstract Schematic presentation for the preparation of the magnetic covalent aromatic polymer (Fe₃O₄-NH₂-CAP) and of magnetic solid-phase extraction.

Organic Analysis of Environmental Samples Using Liquid Chromatography with Diode Array and Fluorescence Detectors: An Overview

This overview is focused to provide an useful guide of the families of organic pollutants that can be determined by liquid chromatography operating in reverse phase and ultraviolet/fluorescence detection. Eight families have been classified as the main groups to be considered: carbonyls, carboxyls, aromatics, phenols, phthalates, isocyanates, pesticides and emerging. The references have been selected based on analytical methods used in the environmental field, including both the well-established procedures and those more recently developed.

Green synthesis of o-hydroxyazobenzene porous organic polymer for efficient adsorption of aromatic compounds

This work presents a simple and eco-friendly synthetic approach to fabricate a novel o-hydroxyazobenzene porous organic polymer (HAzo-POP) by diazo-coupling of 2,6-diaminoanthraquinone with m-trihydroxybenzene in aqueous solution. The prepared HAzo-POP possesses good stability and high adsorption capability towards aromatic organic pollutants due to its porous nature, highly conjugated structure and strong hydrogen bonding ability. The HAzo-POP was successfully used for the solid-phase extraction of phenylurea herbicides from six real samples prior to high performance liquid chromatography with ultraviolet detection. The analytical method showed good linearity in the range of 0.5-160.0 ng g^-1 for celery, lettuce and tomato samples, and 0.4-160.0 ng mL^-1 for milk, soybean milk and juice samples, with low limits of detection in the range from 0.05 to 0.30 ng g^-1 (or mL^-1). The HAzo-POP has a promising application potential for the adsorption of more aromatic organic compounds.

New approach applying a pet fish air pump in liquid-phase microextraction for the determination of Sudan dyes in food samples by HPLC

A new approach applying a pet fish air pump is introduced to develop an extraction method, namely, air-pump-enhanced emulsion, followed by salt-assisted emulsion breaking based on solidified floating organic drop microextraction for the extraction and preconcentration of Sudan I-IV before high-performance liquid chromatography. The applicability of this method was successfully demonstrated by determination of these dyes in four chili products that include chili powder, chili oil, chili sauce, and chili paste. An enrichment factor of 62 was obtained only with a sample solution of 5 mL. A linear range of 0.5-2500 ng/mL was obtained with a limit of detection of 0.16-0.24 ng/mL and recovery of 90-110%. This method is superior to other liquid-liquid extraction methods, as is simple, rapid, environmental friendly, and its phase separation needs no centrifugation. It also needs no disperser solvent and requires less organic solvent, and satisfies the criteria to be called as a green extraction. Therefore, this facile extraction method can be successfully applied in the determination of Sudan dyes in food samples.

Hollow-fiber solvent bar microextraction with gas chromatography and electron capture detection determination of disinfection byproducts in water samples

A liquid-phase microextraction method that uses a hollow-fiber solvent bar microextraction technique was developed by combining gas chromatography with electron capture detection for the analysis of four trihalomethanes (chloroform, dichlorobromomethane, chlorodibromomethane, and bromoform) in drinking water. In the microextraction process, 1-octanol was used as the solvent. The technique operates in a two-phase mode with a 5 min extraction time, a 700 rpm stirring speed, a 30°C extraction temperature, and NaCl concentration of 20%. After microextraction, one edge of the membrane was cut, and 1 μL of solvent was collected from the membrane using a 10 μL syringe. The solvent sample was directly injected into the gas chromatograph. The analytical characteristics of the developed method were as follows: detection limits, 0.017-0.037 ng mL^-1 ; linear working range, 10-900 ng mL^-1 ; recovery, 74 ± 9-91 ± 2; relative standard deviation, 5.7-10.3; and enrichment factor, 330-455. A simple, fast, economic, selective, and efficient method with big possibilities for automation was developed with a potential use to apply with other matrices and analytes.

Simultaneous preconcentration and analysis of anthraquinones based on ultrasound emulsification ionic liquid microextraction

An ultrasensitive method of ultrasound emulsification ionic liquid microextraction (UEILME) coupled with high-performance liquid chromatography (HPLC) has been developed and introduced for the preconcentration and analysis of anthraquinone additives in cosmetic samples and five anthraquinone compounds (aloe-emodin, rhein, emodin, chrysophanol and physcion) in traditional Chinese medicines. Several parameters affecting the extraction efficiency were investigated and optimized, such as the type and amount of extraction solvent, sample pH, ultrasound time and temperature, centrifugation speed and time and ionic strength. The most favorable results were obtained using 60 mg of 1-hexyl-3-methylimidazolium hexafluorophosphate as extraction solvent. The anthraquinones were extracted from the aqueous solution (pH 2.0) by ultrasound at 40°C for 7 min and centrifuged at 2,500 rpm for 6 min. Under optimal conditions, acceptable linearity of the five anthraquinone compounds was obtained with correlation coefficients > 0.99. The limits of detection (LODs) and limits of quantitation (LOQs) ranged from 0.01 to 0.09 µg/L and 0.05 to 0.25 µg/L, respectively. The relative standard deviations (n = 3) were less than 9.8%. Moreover, the enrichment factors ranged from 80 to 197-fold. Compared with conventional dispersive liquid-liquid microextraction, the UEILME technique exhibited lower LODs and LOQs. The results demonstrated that the UEILME coupled with HPLC is a simple, environmentally friendly, sensitive and efficient method for the extraction, concentration and analysis of anthraquinone compounds.

Voltammetric determination of the herbicide Linuron using a tricresyl phosphate-based carbon paste electrode

This paper summarises the results of voltammetric studies on the herbicide 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (Linuron), using a carbon paste electrode containing tricresyl phosphate (TCP-CPE) as liquid binder. The principal experimental conditions, such as the pH effect, investigated in Britton-Robinson buffer solutions (pH 2.0–7.0), the peak characteristics for the analyte of interest, or instrumental parameters for the differential pulse voltammetric mode were optimized for the method. As found out, the best electroanalytical performance of the TCP-CPE was achieved at pH 2.0, whereby the oxidation peak of Linuron appeared at ca. +1.3 V vs. SCE. The analytical procedure developed offers good linearity in the concentration range of 1.25–44.20 μg mL⁻¹ (1.77 × 10⁻⁴–5.05 × 10⁻⁶ mol L⁻¹), showing—for the first time—the applicability of the TCP-CPE for anodic oxidations in direct voltammetry (without accumulation). The method was then verified by determining Linuron in a spiked river water sample and a commercial formulation and the results obtained agreed well with those obtained by the reference HPLC/UV determination.

Development of an ionic liquid-based dispersive liquid-liquid micro-extraction method for the determination of phthalate esters in water samples

Ionic liquid-based dispersive liquid-liquid micro-extraction (IL-DLLME) was coupled with high-performance liquid chromatography-ultraviolet (HPLC-UV) for the determination of four phthalate esters, including butyl benzyl phthalate, di-n-butyl phthalate, dicyclohexyl phthalate and bis(2-ethylhexyl) phthalate in water samples. The mixture of ionic liquid (IL) and dispersive solvent was rapidly injected into 10 mL aqueous sample. Then, IL phase was separated by centrifugation and was determined by high-performance liquid chromatography-ultraviolet. The factors influencing the extraction efficiency, such as type and volume of IL, disperse solvent, extraction time, centrifuging time and ionic strength, were investigated and optimized. Under the optimized conditions, the extraction recoveries by the proposed ionic liquid-based dispersive liquid-liquid micro-extraction for the four phthalates ranged from 83.0 to 91.7%. The relative standard deviations were between 7.8 and 15%. The limits of quantification for four phthalates were between 10.6 and 28.5 μg/L. The proposed method was successfully applied for the analysis of PAEs in tap, lake and treated wastewater samples.