Microextraction High-performance Liquid Chromatography Research Articles

Rapid determination of nine preservatives in tobacco flavor by three phase-hollow fiber-liquid phase microextraction-high performance liquid chromatography

Tobacco flavors are extensively utilized in traditional tobacco products, electronic nicotine, heated tobacco products, and snuff. To inhibit fungal growth arising from high moisture content, preservatives such as benzoic acid (BA), sorbic acid (SA), and parabens are often incorporated into tobacco flavors. Nonetheless, consuming preservatives beyond safety thresholds may pose health risks. Therefore, analytical determination of these preservatives is crucial for both quality assurance and consumer protection. For example, BA and SA can induce adverse reactions in susceptible individuals, including asthma, urticaria, metabolic acidosis, and convulsions. Parabens, because of their endocrine activity, are classified as endocrine-disrupting chemicals. Despite extensive research, the concurrent quantification of trace-level hydrophilic (BA and SA) and hydrophobic (methylparaben, ethylparaben, isopropylparaben, propylparaben, butylparaben, isobutylparaben, and benzylparaben) preservatives in tobacco flavors remains challenging. Traditional liquid phase extraction coupled with high performance liquid chromatography (HPLC) often results in high false positive rates and inadequate sensitivity. In contrast, tandem mass spectrometry offers high sensitivity and specificity; however, its widespread application is limited by laborious sample preparation and significant operational costs. Therefore, it is crucial to establish a fast and sensitive sample pretreatment and analysis method for the nine preservatives in tobacco flavors. In this study, a method for the simultaneous determination of the nine preservatives (SA, BA and seven parabens) in tobacco flavor was established based on three phase-hollow fiber-liquid phase microextraction (3P-HF-LPME) technology combined with HPLC. To obtain the optimal pretreatment conditions, extraction solvent type, sample phase pH, acceptor phase pH, sample phase volume, extraction time, and mass fraction of sodium chloride, were examined. Additionally, the HPLC parameters, including UV detection wavelength and mobile phase composition, were refined. The optimal extraction conditions were as follows: dihexyl ether was used as extraction solvent, 15 mL sample solution (pH 4) was used as sample phase, sodium hydroxide aqueous solution (pH 12) was used as acceptor phase, and the extraction was carried out at 800 r/min for 30 min. Chromatographic separation was accomplished using an Agilent Poroshell 120 EC-C18 column (100 mm×3 mm, 2.7 μm) and a mobile phase comprising methanol, 0.02 mol/L ammonium acetate aqueous solution (containing 0.5% acetic acid), and acetonitrile for gradient elution. Under the optimized conditions, the nine target analytes showed good linear relationships in their respective linear ranges, the correlation coefficients (r) were ≥0.9967, limits of detection (LODs) and quantification (LOQs) were 0.02-0.07 mg/kg and 0.08-0.24 mg/kg, respectively. Under two spiked levels, the enrichment factors (EFs) and extraction recoveries (ERs) of the nine target analytes were 30.6-91.1 and 6.1%-18.2%, respectively. The recoveries of the nine target analytes ranged from 82.2% to 115.7% and the relative standard deviations (RSDs) (n=5) were less than 14.5% at low, medium and high levels. The developed method is straightforward, precise, sensitive, and well-suited for the rapid screening of preservatives in tobacco flavor samples.

The electrospun polyacrylonitrile/covalent organic framework nanofibers for efficient enrichment of trace sulfonamides residues in food samples

In this work, the electrospun polyacrylonitrile/covalent organic frameworks Tp-BD nanofibers (PAN/Tp-BD) were synthesized and applied as an adsorbent for thin film microextraction (TFME) of seven sulfonamides in animal derived food samples. The morphology, structure, porosity, and stability of the prepared nanofibers were investigated. The PAN/Tp-BD nanofibers exhibited good chemical stability, high flexibility, porous fibrous structure, and excellent extraction efficiency. Based on the PAN/Tp-BD nanofibers as the adsorbent, a thin film microextraction-high performance liquid chromatography (TFME-HPLC) method for the determination of seven sulfonamides (SAs) in food samples was developed. Under the optimal conditions, the TFME-HPLC exhibited the low limit of detection (0.10-0.18 ng·mL−1), the low limit of quantitation (0.33-0.60 ng·mL−1), the wide linear range (0.5-50 ng·mL−1) with correlation coefficients between 0.994 and 0.998, and good enrichment factors between 39.7 to 170.1 towards 20 ng/mL SAs solution. The relative standard deviation (RSD) was lower than 11% in the interday and intraday analysis. Furthermore, the applicability of PAN/Tp-BD nanofibers was demonstrated for measuring trace SAs residues in the spiked food samples with recoveries ranging from 85.3% to 115.2%. The results demonstrated that the PAN/Tp-BD nanofibers have great potential for the efficient extraction of sulfonamides from complex food samples.

Solid phase microextraction-high performance liquid chromatography of fluorinated covalent organic polymer to determine eugenol anesthetics in aquatic products

氟化共价有机聚合物(F-COP)具有较大的比表面积和吸附容量,对丁香酚类化合物具有特异性吸附。该文以2,3,5,6-四氟对二苯甲醛(TFA)和1,3,5-三(4-氨苯基)苯(TAPB)为单体,三氟甲磺酸钪(Sc(OTf)3)为催化剂在室温下快速合成F-COP,并将其作为固相微萃取(SPME)吸附剂,结合高效液相色谱-紫外检测法(HPLC-UV),建立了测定水产品中丁香酚、乙酸丁香酚酯和甲基丁香酚麻醉剂的分析方法。通过傅里叶红外光谱、X射线衍射、N2吸附-解吸等温线和扫描电子显微镜等手段对F-COP材料进行表征。考察了萃取时间、搅拌速度、解吸溶剂及解吸时间对丁香酚类麻醉剂萃取量的影响,在萃取时间为30 min、搅拌速度为700 r/min、解吸溶剂为乙腈、解吸时间为10 min时,丁香酚类麻醉剂获得了最佳的萃取效果。在Diamonsil Plus C18-B色谱柱(250 mm×4.6 mm, 5 μm)上,以甲醇-水(60:40, v/v)为流动相,流速0.800 mL/min,进样量20.0 μL,紫外检测波长280 nm,柱温30 ℃条件下,丁香酚和乙酸丁香酚酯在10~1000 μg/L,甲基丁香酚在10~1500 μg/L范围内呈现出良好的线性关系,相关系数(r2)大于0.9961,方法检出限为2.9~4.5 μg/kg(S/N=3),精密度小于8.7%(n=5)。最后,将该分析方法用于罗非鱼和基围虾样品的3种麻醉剂残留分析中,得到了满意的回收率(76.7%~104%)。结果表明,F-COP-SPME-HPLC-UV可满足水产品中丁香酚类麻醉剂的分析检测。

Study on the Oxidation Products of Hemp Seed Oil and its Application in Cosmetics

Abstract Hemp seed oil has a very better effect of sunscreen, repair, anti-allergy and anti-aging, as a result of which it is a high-quality raw material for skin care products. In this study, the oxidation degree of hot-pressed and cold-pressed hemp seed oil which was stored in five different environments, was evaluated. The results showed that the long-chain unsaturated fatty acids were oxidized. The oxidation products of hemp seed oil were analyzed by headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) and high performance liquid chromatography (HPLC). All hemp seed oils which were stored at low-temperature protected from light and outdoor environment contained aldehydes, ketones, and alcohols, which have a negative impact on the health of consumers. Furthermore, hemp seed emulsion was prepared with different HLB values. After the 2nd month, hemp seed oil emulsion exhibited a good stability without stratification.

Simultaneous Determination of Lamotrigine and Carbamazepine in Plasma Using Ultrasound-Assisted Emulsification Microextraction-High Performance Liquid Chromatography

A simple, fast and efficient method based on ultrasound-assisted emulsification microextraction (USAEME) followed by HPLC has been developed for simultaneous determination of Carbamazepine (CBZ) and Lamotrigine (LTG) in biological samples. The influence of different parameters affecting the USAEME procedure was evaluated to optimize the efficiency of the process. At these conditions, validation of the proposed method was performed based on European medicines agency guidelines. The proposed method showed good linearity in plasma samples ranging from 0.25 to 6 µg/mL and 0.13 to 6 µg/mL (R2 ≥ 0.99) for CBZ and LTG, respectively. The precision of the proposed method was evaluated for repeatability which was ≤12% (n = 5). The detection limits of 0.06 and 0.05 µg/mL were obtained for CBZ and LTG, respectively. The proposed method can be applied as an effective technique for therapeutic drug monitoring of CBZ and LTG in plasma of epileptic patients.

Ultrasound-assisted dispersive liquid–liquid microextraction for determination of three gliflozins in human plasma by HPLC/DAD

A novel, highly sensitive ultrasound-assisted dispersive liquid–liquid microextraction (UA-DLLME) high performance liquid chromatography with diode-array detection (HPLC/DAD) method was developed for the determination of empagliflozin, dapagliflozin and canagliflozin in human plasma using methanol as protein precipitating agent/disperser and 1-dodecanol as extracting solvent. The analytes were eluted with an isocratic mobile phase consisting of acetonitrile:aqueous 0.1% trifluoroacetic acid pH 2.5, (40:60, v/v), at a flow rate of 1 mL/min and UV detection at 210 nm. The microextraction conditions were optimized regarding type and volume of extractant, type of disperser, sample pH, extraction time and centrifugation time. Under the optimal conditions, the enrichment factors were 19 for empagliflozin, 27 for dapagliflozin and 50 for canagliflozin. Linearity ranges were 2–2500 ng/mL, 3.5–2500 ng/mL and 1.1–2500 ng/mL for empagliflozin, dapagliflozin and canagliflozin, respectively. The developed method employs very small volumes of organic solvents in sample extraction and allows determination of small concetrations of gliflozins in human plasma.

Determination of four acetanilide herbicides in brown rice juice by ionic liquid/ionic liquid-homogeneous liquid-liquid micro-extraction high performance liquid chromatography

The new method of ionic liquid-based homogeneous liquid-liquid micro-extraction coupled with high performance liquid chromatography was established for the determination of the four acetanilide herbicides, including metazachlor, propanil, alachlor, and butachlor in the brown rice juice. Some experimental conditions, including the salt concentration in sample solution, pH value of sample solution, type and volume of extractant, type and volume of dispersant and extraction time, were examined and optimized. The optimum experimental conditions were created. When the proposed method was applied to the analysis of brown rice juice, the average recoveries of the analytes ranged from 90.9% to 106.4% and relative standard deviations ranged from 2.9% to 5.2%. Under the optimized conditions, the linearities for determination of the analytes were satisfactory.

Effect of Montmorillonite on 4-Nonylphenol Enrichment in Zebrafish.

The aim of this study was to investigate the effect of montmorillonite on nonylphenol (4-nonylphenol, 4-NP) enrichment in a zebrafish model. The AB strain zebrafish were used as the animal subjects, and three concentration gradients were set for both nonylphenol and montmorillonite, according to their actual concentrations in aquaculture water in Huzhou City. A group treated with nonylphenol alone was also set, adding up to 12 experimental groups. Concentrations of nonylphenol enriched in the liver, muscle and gills of zebrafish were detected by solid phase microextraction–high performance liquid chromatography at Days 7, 15 and 30, respectively. Additionally, the relative enzymatic activity of superoxide dismutase (SOD) and the glutathione S-transferase (GST) were also detected, and the data were statistically analyzed. The results showed that the concentrations of nonylphenol in zebrafish peaked at Day 7 and gradually decreased afterwards for all the experimental groups. The montmorillonite reduces short-term accumulation of nonylphenol in gills, and the high concentration of nonylphenol facilitates its enrichment in liver and muscle, while the low concentration of nonylphenol does not. Meanwhile, the low concentration of nonylphenol in liver exerts an influence on the inductive effect of SOD and GST, while the high concentration of nonylphenol shows the inhibiting effect of SOD and GST.

Urea functionalized surface-bonded sol-gel coating for on-line hyphenation of capillary microextraction with high-performance liquid chromatography

Sol-gel urea functionalized-[bis(hydroxyethyl)amine] terminated polydimethylsiloxane coating was developed for capillary microextraction-high performance liquid chromatographic analysis from aqueous samples. A fused silica capillary is coated from the inside with surface bonded coating material and is created through in-situ sol-gel reaction. The urea-functionalized coating was immobilized to the inner surface of the capillary by the condensation reaction of silanol groups of capillary and sol-solution. The characterization of the coating material was successfully done by using X-ray photoelectron spectroscopy, thermogravimetric analysis, field emission scanning electron microscope, and energy dispersive X-ray spectrometer. To make a setup of online capillary microextraction-high performance liquid chromatography, the urea functionalized capillary was installed in the HPLC manual injection port. The analytes of interest were pre-concentrated in the coated sampling loop, desorbed by the mobile phase, chromatographically separated on C-18 column, and analyzed by UV detector. Sol-gel coated capillaries were used for online extraction and high-performance liquid chromatographic analysis of phenols, ketones, aldehydes, and polyaromatic hydrocarbons. This newly developed coating showed excellent extraction for a variety of analytes ranging from highly polar to non-polar in nature. The analysis using sol-gel coating showed excellent overall sensitivity in terms of lower detection limits (S/N = 3) for the analytes (0.10 ng mL−1–14.29 ng mL−1) with acceptable reproducibility that is less than 12.0%RSD (n = 3). Moreover, the capillary to capillary reproducibility of the analysis was also tested by changing the capillary of the same size. This provided excellent%RSD of less than 10.0% (n = 3).

Determination of Aristocularine Enantiomers by Dispersive Liquid–Liquid Microextraction and Chiral High-performance Liquid Chromatography

ABSTRACTHere is reported a novel analytical approach for the extractive separation and determination of enantiomeric ratios of aristocularine in bovine serum albumin. The results demonstrate suitable analytical performances. The separation was performed by chiral high-performance liquid chromatography with a 5-µm column using a mobile phase of 1:1 n-hexane:ethanol at a flow rate of 0.7 mL min−1 with ultraviolet–visible absorption, circular dichroism, and polarimetric detection. The enantiomers were eluted at 13.2 and 15.6 min for (+) and (−)-aristocularine, with a resolution of 1.58 and a separation factor of 1.27. The analytical parameters for the dispersive liquid–liquid microextraction were optimized; under these conditions, the extraction recoveries were from 88.6% to 93.9% for a two-step extraction. The precision, reported as the percent relative standard deviation, had values from 2.9% to 3.2% for 0.5 µg mL−1 of analyte for five replicate measurements using ultraviolet–visible absorption and circular dichroism detection. The limits of detection were between 0.05 and 0.08 µg mL−1 with enrichment ratios up to a value of 12.

Determination of four alkaloids in cell culture fluids by pipette tip solid phase microextraction-high performance liquid chromatography

Determination of four alkaloids in cell culture fluids by pipette tip solid phase microextraction-high performance liquid chromatography

Polydopamine-sheathed electrospun nanofiber as adsorbent for determination of aldehydes metabolites in human urine

In this paper, a novel polydopamine modified polystyrene/graphene electrospun nanofiber membrane (PS/G@PDA) was fabricated on the surface of filter paper and used for thin film microextraction (TFME) for the first time. Benefiting from the hydrophilic polydopamine (PDA) coating and the porous fibrous structure, the PS/G@PDA membrane exhibited large surface area, high extraction efficiency, rapid extraction equilibrium, special selectivity and excellent biocompatibility. A thin film microextraction-high performance liquid chromatography method was developed and applied for the analysis of six aldehyde metabolites in human urine samples. Under the optimal conditions, the recoveries of the aldehyde compounds varied in the range of 83%–115%, with the relative standard deviation values lower than 14.5% (n = 5). Moreover, satisfactory sensitivities with the limits of detection in the range of 2.3–6.5 nmol L−1 and good linearity with excellent correlation coefficients (R2) being larger than 0.9936 had also been achieved. In general, a fast, convenient, sensitive, high-efficient and matrix-free method was successfully proposed and expected becoming a promising approach for the determination of trace aldehyde metabolites in complex biological samples.

Development of a novel polystyrene/metal-organic framework-199 electrospun nanofiber adsorbent for thin film microextraction of aldehydes in human urine

In this work, electrospun polystyrene/metal-organic frameworks-199 (PS/MOF-199) nanofiber film was synthesized and investigated as a novel adsorbent for thin film microextraction (TFME) of aldehydes in human urine. Some properties of the prepared PS/MOF-199 nanofiber film, including morphology, structure, wettability, solvent stability and extraction performance were studied systematically. Porous fibrous structure, large surface area, good stability, strong hydrophobicity and excellent extraction efficiency were obtained for the film. Based on the PS/MOF-199 film, a thin film microextraction-high performance liquid chromatography (TFME-HPLC) method was developed, and the experimental parameters that affected the extraction and desorption were optimized. Under the optimal conditions, the limits of detection (LODs) were in the range of 4.2–17.3nmolL−1 for the analysis of six aldehydes. Good linearity was achieved with correlation coefficients (R2) being lager than 0.9943. Satisfactory recovery (82–112%) and acceptable reproducibility (relative standard deviation: 2.1–13.3%) were also obtained for the method. The developed TFME-HPLC method has been successfully applied to the analysis of aldehyde metabolites in the urine samples of lung cancer patients and healthy people. The method possesses the advantages of simplicity, rapidity, cost-effective, sensitivity and non-invasion, it provides an alternative tool for the determination of aldehydes in complex sample matrices.

Use of volatile organic solvents in headspace liquid-phase microextraction by direct cooling of the organic drop using a simple cooling capsule.

A low-cost and simple cooling-assisted headspace liquid-phase microextraction device for the extraction and determination of 2,6,6-trimethyl-1,3 cyclohexadiene-1-carboxaldehyde (safranal) in Saffron samples, using volatile organic solvents, was fabricated and evaluated. The main part of the cooling-assisted headspace liquid-phase microextraction system was a cooling capsule, with a Teflon microcup to hold the extracting organic solvent, which is able to directly cool down the extraction phase while the sample matrix is simultaneously heated. Different experimental factors such as type of organic extraction solvent, sample temperature, extraction solvent temperature, and extraction time were optimized. The optimal conditions were obtained as: extraction solvent, methanol (10 μL); extraction temperature, 60°C; extraction solvent temperature, 0°C; and extraction time, 20 min. Good linearity of the calibration curve (R(2) = 0.995) was obtained in the concentration range of 0.01-50.0 μg/mL. The limit of detection was 0.001 μg/mL. The relative standard deviation for 1.0 μg/mL of safranal was 10.7% (n = 6). The proposed cooling-assisted headspace liquid-phase microextraction device was coupled (off-line) to high-performance liquid chromatography and used for the determination of safranal in Saffron samples. Reasonable agreement was observed between the results of the cooling-assisted headspace liquid-phase microextraction high-performance liquid chromatography method and those obtained by a validated ultrasound-assisted solvent extraction procedure.

Porous boronate affinity monolith for on-line extraction coupled to high-performance liquid chromatography for sensitive analysis of heterocyclic aromatic amines in food samples

Abstract A novel on-line solid-phase microextraction–high-performance liquid chromatography (SPME–HPLC) system was developed for the determination of heterocyclic aromatic amines (HAAs) in food samples. A poly(vinylphenylboronic acid-co-ethylene glycol dimethacrylate) polymer monolith was prepared for on-line efficient extraction and large-volume injection was used to increase the sensitivity of detection. The polymermonolith, based on a ternary porogen, was prepared by in situ polymerization of vinylphenylboronic acid (VPBA) and ethylene glycol dimethacrylate (EGDMA) in a fused-silica capillary column. It showed good permeability, high extraction capacity, and high selectivity. The column-to-column reproducibility was satisfactory, and the enrichment factors for HAAs were 3746–7414. Conditions influencing the on-line extraction efficiency, including pH of sample solutions, flow rate of extraction and desorption, and desorption volume, were investigated. The proposed method had low limit of detection (0.10–0.15 ng/L) and good linearity. Trace HAAs in roast beef and lamb samples were determined, and the amounts of 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline, and 2-amino-3,4,7,8-tetramethyl-3 H -imidazo[4,5-f]quinoxaline in these samples were 0.235–2.08 ng/g. The recoveries for the five HAAs ranged from74.3% to 119%, and the relative standard deviation (RSDs) were less than 8.2%. The results showed that the proposed on-line method was highly sensitive for monitoring HAAs in different food samples.

Online Injection-Based Hollow Fiber Liquid-Phase Microextraction–High-Performance Liquid Chromatography as a Fully Automatic Sample Processing for Phthalate Esters Analysis

Recently, a novel analytical instrument setup was reported for automatic preconcentration and determination of organic compounds in various sample matrices based on online hollow fiber liquid-phase microextraction (HF-LPME)–high-performance liquid chromatography (HPLC). In the present work, this novel instrument has been developed for extraction and determination of phthalate esters samples located in the polyethylene (PET) bottles. By using an automated syringe pump for loading supported liquid membrane (SLM) and acceptor solvents, a platform lift for moving sample vial, and a sampling loop for online injection of extract to HPLC, along with an electronic board with AVR microcontroller for storage of data and instrument programs, an automated sample preparation-HPLC analysis was developed. Optimization of extraction parameters was carried out by Box–Behnken design (BBD) which required a minimum of 29 experiments; the entire set of experiments was performed completely automatically and consecutively without any human intervention. The limits of detection (three times the S/N) ranged from 0.3 to 0.5 μg L−1. Effective preconcentration of the analytes was also achieved (between 153 and 335). The method is highly precise, with relative standard deviations varying between 5.1 and 6.4 % and also accurate (recovery percentages >94.6 %). The main advantages of the developed method are high sensitivity, selectivity, and reliability of results, minimum sample manipulation, full automation, suitable extraction time, low solvent consumption, and ease of use. The applicability of the online automated HF-LPME/HPLC-UV instrument was validated for quantitative extraction and determination of phthalate esters in aqueous samples located inside the PET bottles.

Electrospun polystyrene/graphene nanofiber film as a novel adsorbent of thin film microextraction for extraction of aldehydes in human exhaled breath condensates

In the current study, we introduced a novel polystyrene/graphene (PS/G) composite nanofiber film for thin film microextraction (TFME) for the first time. The PS/G nanofiber film was fabricated on the surface of filter paper by a facile electrospinning method. The morphology and extraction performance of the resultant composite film were investigated systematically. The PS/G nanofiber film exhibited porous fibrous structure, large surface area and strong hydrophobicity. A new thin film microextraction-high performance liquid chromatography (TFME-HPLC) method was developed for the determination of six aldehydes in human exhaled breath condensates. The method showed high enrichment efficiency and fast analysis speed. Under the optimal conditions, the linear ranges of the analytes were in the range of 0.02–30μmolL−1 with correlation coefficients above 0.9938, and the recoveries were between 79.8% and 105.6% with the relative standard deviation values lower than 16.3% (n=5). The limits of quantification of six aldehydes ranged from 13.8 to 64.6nmolL−1. The established method was successfully applied for the quantification of aldehyde metabolites in exhaled breath condensates of lung cancer patients and healthy people. Taken together, the TFME-HPLC method provides a simple, rapid, sensitive, cost-effective, non-invasion approach for the analysis of linear aliphatic aldehydes in human exhaled breath condensates.

Determination of fluoroquinolone drugs in meat by ionic-liquid-based dispersive liquid–liquid microextraction-high performance liquid chromatography

Ionic-liquid-based dispersive liquid–liquid microextraction combined with high performance liquid chromatography was used to determine four fluoroquinolone drugs in meat.

Synchronous extraction and determination of phenoxy acid herbicides in water by on-line monolithic solid phase microextraction-high performance liquid chromatography

A C18 monolithic capillary column was utilized as the solid phase microextraction column to construct an in-tube SPME-HPLC system which was used to simultaneously extract and detect five phenoxy acid herbicides, including 2,4-dichlorophenoxyacetic acid (2,4-D), 2- (2-chloro)-phenoxy propionic acid (2,2-CPPA), 2-(3-chloro)-phenoxy propionic acid (2,3- CPPA), phenoxy propionic acid (PPA) and 2-(2,4-dichlorophenoxy) propionic acid (2,4-DP). The operating parameters of the in-tube SPME-HPLC system, including the length of the monolithic column, the sampling flow rate, the sampling time, the elution flow rate and the elution time, had been investigated in detail. The optimized operating parameters of the in-tube SPME-HPLC system were as follow: the length of the monolithic column was 20 cm, the sampling flow rate was 0. 04 mL/min, sampling time was 13 min; the elution flow rate was 0.02 mL/min, elution time was 5 min. Under the optimized conditions, the detection limits of the five phenoxy acid herbicides were as follows: 9 µg/L for PPA, 4 µg/L for 2,2-CPPA, 4 µg/L for 2,3-CPPA, 5 µg/L for 2,4-D, 5 µg/L for 2,4-DP. Compared with the HPLC method with direct injection, the combined system showed a good enrichment factors to the analytes. The recoveries of the five phenoxy acid herbicides were between 79.0% and 98.0% (RSD ≤ 3.9%). This method was successfully used to detect the five phenoxy acid herbicides in water samples with satisfactory results.

Determination of triazine herbicides in fresh vegetables by dynamic microwave-assisted extraction coupled with homogeneous ionic liquid microextraction high performance liquid chromatography.

A novel extraction method, dynamic microwave-assisted extraction coupled with homogeneous ionic liquid microextraction, was developed for the determination of triazine herbicides, including desmetryn, terbumeton, propazine, terbuthylazine, dimethametryn, and dipropetryn in fresh vegetable samples by high performance liquid chromatography (HPLC). In the developed method, 120 μL of 1-butyl-3-methylimidazolium tetrafluoroborate ([C4MIM][BF4]) was added to 10 mL of aqueous solution containing 0.3 g of NaCl to obtained the extraction solvent. Six triazines could be extracted completely within 4 min by the present method. Then, [NH4][PF6] was added into the extract to form a water-insoluble ionic liquid [C4MIM][PF6] via a simple metathesis reaction, and the analytes were enriched into the ionic liquid phase. After centrifugation and dilution with acetonitrile, the resulting solution was analyzed directly by HPLC. The effects of some experimental parameters, including type and volume of ionic liquid, volume of extraction solvent, amount of ion-pairing agent [NH4][PF6], salt concentration, microwave power, and flow rate of extraction solvent on the extraction efficiency were investigated and optimized. Under the optimum experimental conditions, the linearity for determining the analytes was in the range of 2.50-250.00 μg kg(-1), with the correlation coefficients ranging from 0.9989 to 0.9999. When the present method was applied to the analysis of vegetable samples, satisfactory recoveries were obtained in the range of 76.8%-106.9%, and relative standard deviations were lower than 9.8%.