Phase Extraction-high Performance Liquid Chromatography Research Articles

Structure-based design and screening of hydrogel copolymer/Fe3O4 composite microspheres for magnetic solid phase extraction of bisphenol A from aqueous samples

It is of great significance to monitor bisphenol A (BPA) in the environment because of its potential environmental and health risks. However, the detection of trace or ultratrace BPA in complicated environmental samples is challenging due to the relatively low affinity and poor selectivity of existing adsorbents used in sample pretreatment. Herein, we report a high-affinity, low environment-dependent and strong interference-resistant abiotic affinity ligand, a N-methacryloyl-l-lysine-NH2 (MLys)-based hydrogel copolymer (HP 17) screened from a small focused polymer library engineered by incorporating various combinations and ratios of candidate functional monomers. The selection of these monomers was guided by molecular mechanism between BPA and the ligand-binding pocket of its estrogen receptors. The BPA–HP17 binding is mainly a synergistic effect of π-cation and hydrophobic interactions. The screened HP 17 has high adsorption capacity (349.4 mg/g) for BPA under wide pH (3.0–10.0) and ionic strength (0–150 mM) range. To improve its practicability, a hydrogel copolymer/Fe3O4 composite microspheres (Fe3O4@HP 17) was synthesized and applied for magnetic solid phase extraction–high-performance liquid chromatography (MSPE–HPLC) analysis of BPA in tap water, lake water and industrial effluents. The method shows wide linear range (2.5⁓100 ng/mL), high sensitivity (detection limit of 0.22 ng/mL even without further concentration after desorption), high accuracies (92.6⁓103.0 %) and good precisions (0.57⁓4.53 %), indicating a great potential of this material and method in the detection of trace or ultratrace BPA in complex environmental water samples.

Determination of quinolone antibiotics in surface water by MnFe2O4@TiO2 magnetic solid phase extraction-high performance liquid chromatography

The magnetic solid phase extraction material (MnFe2O4@TiO2) was prepared by coating TiO2 on MnFe2O4 through an in-situ formation method. The structure and properties of MnFe2O4@TiO2 were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), nitrogen adsorption–desorption experiment, and vibrating sample magnetometer (VSM). The conditions for magnetic solid phase extraction (MSPE) of quinolone antibiotics were optimized, and an MSPE-HPLC method was established to determine quinolone antibiotics in water samples. The optimal conditions for MSPE are MnFe2O4@TiO2 amount of 15 mg, extraction time of 15 min, 5 mL of methanol solution with 20 % ammonia as eluent, and elution time of 1 min. Under the optimal conditions, 50 mL 0.1 mg/L mixed standard solutions of fleroxacin, ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin have achieved enrichment multiples of 67.8, 72.1, 59.6, 55.8, and 60.7, respectively. The linear range of five antibiotics determined by MSPE-HPLC is 0.004–1 mg/L with the relative standard deviations (RSDs) of 2.1 %–4.9 % and the limits of detection (LODs) of 0.0006–0.0020 mg/L. The method is applied to the determination of the five antibiotics in rice paddy water and fish pond water; the recoveries range from 78.9 to 105.8 %, and the RSDs (n = 5) are 3.6 %–8.7 %.

Online solid phase extraction high-performance liquid chromatography – Isotope dilution – Tandem mass spectrometry quantification of organophosphate pesticides, synthetic pyrethroids, and selected herbicide metabolites in human urine

Analytical methods to quantify pesticide biomarkers in human population studies are critical for exposure assessment given the widespread use of pesticides for pest and weed control and their potential for affecting human health. We developed a method to quantify, in 0.2 mL of urine, concentrations of 10 pesticide biomarkers: four organophosphate insecticide metabolites (3,5,6-trichloro-2-pyridinol (TCPy), 2-isopropyl-6-methyl-4-pyrimidinol, para-nitrophenol, malathion dicarboxylic acid); five synthetic pyrethroid insecticide metabolites (4-fluoro-3-phenoxybenzoic acid, 3-phenoxybenzoic acid, cis and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (DCCA), cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid); and the herbicide 2,4-dichlorophenoxyacetic acid.he method is based on enzymatic hydrolysis of conjugated urinary metabolites, extraction and pre-concentration of the deconjugated metabolites using automated online solid-phase extraction, and separation and quantification using liquid chromatography-isotope dilution tandem mass spectrometry.Depending on the analyte, method detection limits were 0.1–0.6 ng/mL; mean accuracy, calculated as spike recoveries, was 91–102%, and total precision, given as percent variation coefficient, was 5.9–11.5%. Percent differences associated with three freeze-thaw cycles, 24-h benchtop storage, and short-term processed sample stability were <14%.Method suitability was assessed by recurring successful participation in external quality assessment schemes and by analyzing samples from subjects with suspected exposure to pesticides (n = 40) or who self-reported consuming an organic diet (n = 50). Interquartile ranges were considerably lower for people consuming an organic diet than for those potentially exposed for cis-DCCA (0.37 ng/mL vs 0.75 ng/mL), trans-DCCA (0.88 ng/mL vs 1.78 ng/mL) and TCPy (1.81 ng/mL vs 2.48 ng/mL). This method requires one-fifth of the sample used in our previous method and is suitable for assessing background exposures to select pesticides in large human populations and for studies with limited sample volumes.

Nanoconfinement of functionalized ionic liquid for enhanced adsorption and rapid sensitive detection of phenylurea herbicides in food and environmental samples

The novel ILs@CNTs was synthesized by encapsulating task-specific ionic liquids (ILs) within carbon nanotubes (CNTs) derived from ZIF-67. These hybrid materials served as multifunctional adsorbents enabling simultaneous sorptive removal, sensitive detection, molecular sieve selection, and magnetic separation. In contrast to pristine CNTs, ILs@CNTs demonstrate significantly enhanced adsorption of phenylurea herbicides (PUHs). The complex interactions between ILs@CNTs and PUHs were comprehensively analyzed using a combination of experimental results and theoretical calculations. Furthermore, a magnetic solid phase extraction-high performance liquid chromatography (MSPE-HPLC) method was developed for the determination of multiple trace PUHs in real samples. The method exhibited lower detection limits (0.02–0.03 μg L−1) and higher enrichment factors (131 < EFs < 185). Interestingly, a portable lab-in-a-syringe device was developed to facilitate rapid on-site extraction and enrichment of PUHs. Additionally, the developed methods successfully applied in river water, tea drinks, and cucumber samples, highlighting its substantial potential for rapid PUH detection.

Determination of 15 carbonyl compounds in soil using improved solid phase extraction-high performance liquid chromatography

An improved solid phase extraction (SPE)-high performance liquid chromatography method was established to determine 15 carbonyl compounds, namely, formaldehyde (FOR), acetaldehyde (ACETA), acrolein (ACR), acetone (ACETO), propionaldehyde (PRO), crotonaldehyde (CRO), butyraldehyde (BUT), benzaldehyde (BEN), isovaleraldehyde (ISO), n-valeraldehyde (VAL), o-methylbenzaldehyde (o-TOL), m-methylbenzaldehyde (m-TOL), p-methylbenzaldehyde (p-TOL), n-hexanal (HEX), and 2,5-dimethylbenzaldehyde (DIM), in soil. The soil was ultrasonically extracted with acetonitrile, and the extracted samples were derivatized with 2,4-dinitrophenylhydrazine (2,4-DNPH) to generate stable hydrazone compounds. The derivatized solutions were cleaned using an SPE cartridge (Welchrom® BRP) packed with N-vinylpyrrolidone/divinylbenzene copolymer. Separation was performed on an Ultimate® XB-C18 column (250 mm×4.6 mm, 5 μm), isocratic elution was performed with acetonitrile-water (65∶35, v/v) as the mobile phase, and detection was performed at a wavelength of 360 nm. The 15 carbonyl compounds in the soil were then quantified using an external standard method. The proposed method improves the sample processing method described in the environmental standard HJ 997-2018: Soil and sediment-Determination of carbonyl compounds-High performance liquid chromatography. A series of experiments revealed the following optimal conditions for soil extraction: acetonitrile as the extraction solvent, extraction temperature of 30 ℃, and extraction time of 10 min. The results showed that the purification effect of the BRP cartridge was significantly better than that of the conventional silica-based C18 cartridge. The 15 carbonyl compounds showed good linearities, and all correlation coefficients were above 0.996. The recoveries ranged from 84.6% to 115.9%, the relative standard deviations (RSDs) ranged from 0.2% to 5.1%, and the detection limits were 0.02-0.06 mg/L. The method is simple, sensitive, and suitable for the accurate quantitative analysis of the 15 carbonyl compounds in soil specified in HJ 997-2018. Thus, the improved method provides reliable technical support for studying the residual status and environmental behavior of carbonyl compounds in soil.

Determination of trans-4-hydroxy-2-alkenals in thermally treated soybean oil by SPE-HPLC

Trans-4-hydroxy-2-hexenal (4-HHE) and trans-4-hydroxy-2-nonenal (4-HNE) are secondary lipid peroxidation products in edible oils, which are cytotoxic and genotoxic. They could covalently bind with protein, phospholipids and DNA, further disrupting the normal function of liver, lung and brain. Derivation process was generally conducted during pretreatment before detection and quantification of 4-HHE and 4-HNE. However, the derivation procedures were time consuming and chemical degradation may occur during the process. Hence, this paper aims to establish a simple solid phase extraction-high performance liquid chromatography (SPE-HPLC) method to determine the 4-HHE and 4-HNE contents in thermally treated soybean oil. C18 solid phase extraction was applied in the pretreatment process. Firstly, the reliability of the method was evaluated. Good linearity was observed in the range of 0.1–0.5 μg/mL and 0.5–10 μg/mL for 4-HHE and 4-HNE. The limit of detection (LOD) of 4-HHE and 4-HNE were 0.0486 and 0.0129 μg/mL, respectively. And the limit of quantitation (LOQ) of 4-HHE and 4-HNE were 0.1458 and 0.0431 μg/mL, respectively. Recovery rate were in the range of 89.11%–91.58% and 71.83%–79.40% for 4-HHE and 4-HNE, respectively. The method achieved the extraction, purification and detection of 4-HHE and 4-HNE simultaneously and had the advantages of simple operation, effectiveness, high precision, good repeatability. Then, the method was applied to monitor the concentrations of 4-HHE and 4-HNE in soybean oil heated at 180 °C for 40 h. The contents of 4-HHE and 4-HNE were 0–0.32 μg/g and 0–6.97 μg/g, respectively, which provided guidance for evaluating health risks of thermally treated soybean oil during heating.

Hierarchical porous phenolic polymer for efficient adsorption of triazine herbicides: Novel preparation strategies and potential applications

Efficient removal of pollutants based on porous adsorbents is a research hotspot now. Triazine herbicides (TRZHs), a class of broad-spectrum, low-cost pesticides, have become an environmental concern owing to the widespread use and abuse these chemicals. In this study, an ionic liquid (IL)-functionalized porous m-aminophenol formaldehyde polymer (IL-PMAPFP) used to adsorb four TRZHs (simazine, cyanazine, atrazine, and terbuthylazine) in environmental water was synthesized. The role of the ethylene oxide/propylene oxide block copolymer (F127) and IL in pore formation was confirmed by microscopic morphology and specific surface area analysis of IL-PMAPFP. The specific surface area of IL-PMAPFP increased 13-fold after adding F127 and the IL. The adsorption of TRZHs on IL-PMAPFP conformed to the pseudo-second-order kinetic and Freundlich isotherm models. The adsorption process is spontaneous, endothermic, and has a strong anti-interference ability. The adsorption equilibrium of IL-PMAPFP could be reached within 1 h, and the adsorption capacities of the four TRZHs are 4.26, 4.82, 5.21, and 8.53 mg/g, respectively, which were higher than many reported adsorbents. Theoretically, the ability of the adsorbent to treat TRZH-contaminated water is 450–900 L/g. IL-PMAPFP is a powerful adsorbent owing to its large surface area, high adsorption amount, fast mass transfer, and good regeneration capability (>eight cycles). IL-PMAPFP combined with dispersive solid phase extraction/miniaturized pipette tip solid phase extraction-high performance liquid chromatography is expected to accurately quantify TRZHs. In addition, the synergistic pore formation strategy of F127 and IL present a new method for preparing of porous polymer. This study provides a new perspective for developing efficient purification techniques to monitor and remove pollutants.

Adsorption characteristics of polythiophene for tetracyclines and determination of tetracyclines in fish and chicken manure by solid phase extraction-HPLC method

Porous polythiophene materials were successfully synthesized by external-crosslinker method and applied as sorbents in solid-phase extraction. A method for the determination of tetracycline antibiotics (tetracycline/ oxytetracycline/doxycycline) in fish and chicken manure was proposed by combining solid phase extraction-ultraviolet visible spectrophotometer (SPE-UV) and solid phase extraction-high performance liquid chromatography (SPE-HPLC). The effects of material dosage, extraction time, washing time, eluent type and dosage, and the reusability of polythiophene sorbent on extraction rate were investigated. With the use of SPE-HPLC method, satisfied linearity for three tetracyclines antibiotics was obtained in the range of 0.004–1 mg/L. The detection limits (LODs) were ranged from 0.0012 to 0.0027 mg/L and the relative standard deviations (RSDs) were 3.5–7.3% (n = 5). The recoveries in actual fish samples and chicken manure samples were 91.1–114.1% and 69.5–93.2%, respectively. No tetracycline antibiotics were detected in fish samples and no doxycycline was detected in chicken manure samples. However, oxytetracycline and tetracycline were detected in two chicken manure samples with the contents of 5.12, 6.58 mg/kg and 6.08, 7.72 mg/kg, respectively. This method was simple, sensitive and suitable for the determination of tetracyclines in practical samples.

Spatiotemporal Distributions and Ecological Risk Assessments of Typical Antibiotics in Surface Water of Taihu Lake

Using solid phase extraction-high performance liquid chromatography tandem mass spectrometry, antibiotics belonging to four classes (i.e. sulfonamides, quinolones, tetracycline, and macrolides) in the surface water of Taihu Lake were monitored monthly for a year. Moreover, the potential ecological risks of antibiotics in Taihu Lake were assessed. During the one-year monitoring, all the eighteen target antibiotics were detected to some extent in the surface water. The detection rates of five sulfonamides (sulfamethoxazole, sulfathiazole, sulfadiazine, sulfadimethazine, and trimethoprim) were higher than 50%. The concentrations of quinolones in the surface water were relatively higher. The average and medium concentrations of ciprofloxacin were 13.0 ng·L-1 and 13.5 ng·L-1, respectively. There were significant differences in the antibiotic pollution during the different months, with the average concentrations of the target antibiotics ranging from 7.3 to 33.5 ng·L-1. The concentration levels were lower from June to October, while higher concentrations were observed from February to May and in November. In the surface water of Taihu Lake, the spatial variations of antibiotics among the 20 sampling sites were not significant, with the average concentrations ranging from 13.0 to 14.3 ng·L-1. During the one-year monitoring, the rates of medium and high risks that the antibiotics posed to algae reached 57.5%. The ecological risks of antibiotics were more severe in April and November, and the quinolones may be the dominant risk factor. This issue should be carefully considered by management authorities.

Poly amidoamine functionalized poly (styrene-divinylbenzene-glycidylmethacrylate) composites for the rapid enrichment and determination of N-phosphoryl peptides

In this work, poly amidoamine grafted composites were proposed as enrichment adsorption materials. The composites were synthesized by grafting poly amidoamine dendrimers onto the surface of poly (styrene–divinylbenzene-glycidylmethacrylate) beads. The number of surface functional groups and adsorption capacities of the composites were controllable by varying the generations of poly amidoamine dendrimers. Afterward, adsorption parameters and desorption eluents were optimized by using N-phosphoryl dipeptide as a target molecular. Under the optimized condition, N-phosphoryl dipeptides in aqueous could be rapidly adsorbed within 30 s, and comparatively high selectivity, enrichment efficiency and recovery efficiency were obtained at pH 3 to 7. The used adsorbents show good reproducibility after being washed by methanol solvent. Reliability of the adsorbents was demonstrated by the determination of N-phosphoryl dipeptide in drinking water samples with the efficient dispersive solid phase extraction-high performance liquid chromatography method. According to the obtained result, the adsorbent showed satisfactory repeatability (RSD ≤ 5.51) and good recoveries (90.52–102.84%).

Heterocyclic frameworks as efficient sorbents for solid phase extraction-high performance liquid chromatography analysis of nitroimidazoles in chicken meat

In this work, three aromatic heterocycle-based porous organic frameworks (heterocyclic POFs) were prepared through a simple Friedel-Crafts alkylation of furan, thiophene and pyrrole with p-dimethoxybenzene as crosslinker. The prepared heterocyclic POFs, featuring abundant heteroatoms and extended conjugated system, displayed high adsorption affinity for nitroimidazoles (NDZs) antibiotics. So, they were applied as adsorbents for solid phase extraction of NDZs (metronidazole, ronidazole, dimetridazole, ornidazole) from chicken meat before their determination by high performance liquid chromatography-ultraviolet detection. Good linearity range (2.0–100.0 ng g−1), low limits of detection (0.6–1.2 ng g−1), high recovery (84.0–114.5%) and satisfactory precision (relative standard deviations < 10%) for the NDZs were obtained under the optimized conditions. The developed method was successfully applied to determine NDZs s in chicken meat. This work provided a good alternative for the rapid and effective detection of trace NDZs residues in chicken meat samples.

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.

Distribution of Four Artificial Sweeteners in Water Treatment and Water Supply System in City H of Zhejiang Province

Taking the sewage and drinking water treatment system of two cities in Zhejiang Province as the main research target, a systematic investigation on the common artificial sweeteners was carried out by solid phase extraction-high performance liquid chromatography (SPE-HPLC). The results showed that SPE-HPLC can accurately determine micro acesulfame (ACE), saccharin (SAC), aspartame (ASP), and neotame (NEO) in water. The detection limits were 57, 120, 170, and 47 μg·L-1, and the quantification limits were 190, 400, 567, and 157 μg·L-1, respectively. After optimization of the solid phase extraction procedure when using PWAX columns, the recoveries of ACE and SAC were enhanced to 86.5% and 97.7%; however, it slightly decreased to 66.5% for NEO. The occurrence rates of ACE, SAC, and NEO in domestic sewage were 100.0%, and it was only 33.3% for ASP. The highest concentrations of four aforementioned artificial sweeteners in domestic sewage were 0.83, 4.52, 1.22, and 7.57 μg·L-1, respectively. The highest concentrations of acesulfame, saccharin, aspartame, and neotame in source water were 22.94, 39.17, 0.73, and 8.92 μg·L-1, respectively, and detection rates were 72.7%, 90.9%, 18.2%, and 90.9%, respectively. Most artificial sweeteners were removed by the prozone process; the removal efficiencies of ACE, SAC, and NEO ranged from 67.7% to 100.0%, and the removal efficiencies of ACE, SAC, and NEO by the advanced treatment process ranged from 73.7% to 100.0%, which effectively reduced the risk of drinking water quality. The four artificial sweeteners were not detected in the water supply network.

ANALYSIS OF FERULIC ACID IN ARABICA COFFEE BEAN (COFFEA ARABICA L.) USING SOLID PHASE EXTRACTION–HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

Objective: The purpose of this research is quantitatively analyzing of ferulic acid in the Arabica coffee bean extract from three samples with different regions (Garut, Pangalengan, Tasikmalaya, West Java Indonesia) using Solid Phase Extraction-High Performance Liquid Chromatography (SPE-HPLC) method which is validated.&#x0D; Methods: The analysis method used reversed phase HPLC with an Enduro C 18 G (250 mm × 4.6 mm) column and detector UV 312 nm, with a mobile phase of methanol and water containing 1% (v/v) of acetic acid (42:58) at a flow rate of 1.0 ml/min and validation method was examined in linearity, Limit of Detection (LOD), Limit of Quantification (LOQ), precision, and accuracy.&#x0D; Results: The results showed that the precision of retention was 8.853 min, correlation coefficient (R) was 0.9996, and the recovery was 96.909%. The quantitative analysis of ferulic acid content in the extract of coffee from thus samples of three different regions were 0.0385%, 0.0169% and 0.0076%, respectively.&#x0D; Conclusion: The analytical method was meet the validation criteria. Ferulic acid levels results from the extraction of the digestion process and pretreatment methods of Solid Phase Extraction (SPE) is 0.0385% from Garut area, 0.0169% from Pangalengan area and 0.0076% from Tasikmalaya area.

Analysis of antibiotic resistance of Escherichia coli isolated from the Yitong River in North-east China

The Yitong River is one of the largest secondary tributaries of the Songhua River. The area where the Yitong River flows is densely populated and contains the livestock and poultry breeding areas of northeast China. These areas introduce a high risk of antibiotic contamination. In this study, the concentrations of four types of typical antibiotics including quinolones, tetracyclines, sulfonamides, and trimethoprim were determined by solid phase extraction-high performance liquid chromatography. The antibiotic resistance of Escherichia coli caused by antibiotic pollution was investigated. The concentration of total coliforms in the Yitong River was detected by the plate counting method. The antibiotic resistance of E. coli to quinolones, tetracyclines, sulfonamides, and trimethoprim was analyzed by the Kirby-Bauer method. The results showed that the concentration of total coliforms in the summer was higher than that in the spring. There was a seasonal difference in the resistance rate of E. coli to antibiotics except trimethoprim. The antibiotic resistance to fluoroquinolones was relatively low. The resistance rate to tetracyclines was higher during the summer. Moreover, resistance to several antibiotics was observed in all sections. This study provides basic data for research on pollution characteristics and prevention of antibiotic exposure in rivers.

Determination of neohesperidin dihydrochalcone and naringin dihydrochalcone in feeds by solid phase extraction-high performance liquid chromatography

A new method was established for the determination of neohesperidin dihydrochalcone (NHDC) and naringin dihydrochalcone (Naringin DC) in feeds by solid phase extraction-high performance liquid chromatography (SPE-HPLC). The samples were extracted by methanol and were purified on an HLB solid-phase extraction column. Chromatographic separation was achieved on an XB-C18 column (150 mm×4.6 mm, 5 μm) by linear gradient elution using methanol/water as the mobile phase. The analytes were detected by the diode array detector (DAD). The results revealed a good linear correlation (r>0.999) between the peak areas and mass concentrations of dihydrochalcone sweeteners in the range of 0.2-49.0 mg/L. The limits of quantification (LOQs) of NHDC and Naringin DC were 0.02 and 0.01 mg/kg, respectively. Intra- and inter-day reproducibilities were 0.7%-4.1% and 0.9%-6.0%, respectively. The spiked recoveries for the samples and relative standard deviations (RSDs) were 86.2%-105.0% and 1.0%-6.3% (n=3), respectively. It is both sensitive and repeatable for the quantitative determination of neohesperidin dihydrochalcone and naringin dihydrochalcone in feeds, and thus, can be used to effectively reduce interference in feeds.

Determination of organic ultraviolet filters in environmental waters by magnetic solid phase extraction-high performance liquid chromatography

A method for the determination of organic ultravioletfilters (OUFs) in water samples was developed by the combination of polymeric ionic liquid-based magnetic solid-phase extraction (PIL-MSPE) and high performance liquid chromatography-diode array detection (HPLC-DAD). To achieve the optimum extraction performance for the target analytes, several key variables, including desorption solvent, adsorption and desorption time, sample pH value and ionic strength in the sample matrix, were investigated in detail. Under the most favorable extraction conditions, linear behaviors were observed in the ranges of 0.5-200.0 μg/L for octyl salicylate and 0.2-200.0 μg/L for the other analytes. The limits of detection (LODs, S/N=3) and limits of quantification (LOQs, S/N=10) for the target OUFs were in the ranges of 0.009-0.13 μg/L and 0.031-0.43 μg/L, respectively. The developed PIL/MSPE-HPLC-DAD method was successfully applied to detect trace OUFs in real water samples. The spiked recoveries at different spiked levels were 71.4%-120%, and the RSDs were below 10% for all the compounds in all the samples. The proposed method has some unique merits including simple operation, fast extraction procedure, high sensitivity and environmental friendliness. It can become a useful method for the monitoring of trace OUFs in water samples.

Development of an SPE Method Using Ionic Liquid-Based Monolithic Column for On-Line Cleanup of Human Plasma and Simultaneous Determination of Five Steroid Drugs

An 1-vinyl-3-hexyl imidazolium bromide ionic liquid-based monolithic column was prepared via in situ free radical polymerization, which was used as the sorbent of on-line solid phase extraction. The prepared material was characterized by scanning electron microscopy, nitrogen adsorption–desorption instrument and mercury intrusion porosimetry, respectively, and the results showed that the homemade monolith occupied relatively uniform porous structure and high-specific surface area of 212.53 m2 g−1. On-line solid phase extraction–high-performance liquid chromatography was performed to quantitatively analyze five steroid drugs, including betamethasone, norgestrel, halcinonide, beclomethasone dipropionate and testosterone propionate in human plasma. The determination procedure was carried out following the optimization of the mobile phase composition. Methodological validation showed that correlation coefficients of the linear regressions were in the range of 0.9989–0.9992; the values of relative standard deviation for precision were in the range of 1.39–6.15% for intra-day and 0.32–6.34% for inter-day, respectively; the values of accuracy expressed by recovery were in the range of 99.02–101.98, 93.27–102.89, 102.79–104.01, 100.04–102.61 and 100.77–102.44% for the five drugs in order, respectively; the values of relative standard deviation for repeatability calculated according to retention times and peak areas of the five drugs were in the ranges of 0.28–0.76% (n = 5) and 0.84–2.63% (n = 5), respectively. The results showed that the polymer monolithic column was feasible for an on-line solid phase extraction column, exhibiting good selectivity and high permeability.

Determination of sulfonylurea herbicide residues in tobacco leaves by molecularly imprinted-solid phase extraction-high performance liquid chromatography

Molecularly imprinted polymer (MIP) micro-particles were prepared in dichloromethane (DCM) by precipitation polymerization using chlorsulfuron (CS) as a template molecule, α -methacrylic acid (MAA) as a functional monomer, and trimethylolpropane trimethacrylate (TRIM) as a cross-linker. The pretreatment process of the tobacco sample spiked with chlorsulfuron, metsulfuron-methyl, bensulfuron-methyl, tribenuron-methyl, ethametsulfuron, and nicosulfuron, was performed using a chlorsulfuron molecularly imprinted polymer solid phase extraction (CS-MIP-SPE) column prepared with CS-MIP as the sorbent. High performance liquid chromatography (HPLC) was subsequently used for quantitative analysis. In this way, a detection technique for sulfonylurea herbicide residues in tobacco leaves was developed using CS-MIP-SPE as a pretreatment method and HPLC as an analytical tool. The results showed that the methods can be applied to the determination of the six sulfonylurea herbicides in tobacco samples. At spiking contents ranging from 0.50 to 50 μg/g, the recoveries for the six sulfonylurea herbicides in tobacco samples were 77.60%-102.05%, with relative standard deviations of 0.16% to 7.07%, and detection limits of 0.08-0.46 μg/g. With its unique advantages, the MIP-SPE-HPLC method provides a multi-residue analytical platform that can meet the requirements of simultaneous determination of sulfonylurea herbicides in tobacco samples.

Geochemical interactions between iron and phenolics originated from peatland in Hani, China: implications for effective transport of iron from terrestrial systems to marine

Iron is a restrictive element for primary productivity in the oceans. The influence of dissolved organic matters as metal chelators on the bio-available iron input to the ocean has been widely reported. However, natural dissolved organic matters, especially the phenolics originated from peatlands and geochemical interactions with iron remains poorly understood. In this study, solid phase extraction-high performance liquid chromatography experiments were conducted to determine the vertical distributions of phenolic acids in different peat layers in Hani Peatland, China. Ten phenolic acids, including protocatechuic acid, p-hydroxybenzoic acid, gentisic acid, caffeic acid, etc. were detected. Simulation experiments of phenolics-Fe interactions under alkaline conditions (pH = 8.0 ± 0.1) indicated phenolic acids bearing either catechol or galloyl groups (such as protocatechuic acid, caffeic acid and gallic acid) could chelate iron to produce relatively stable phenolics-Fe complexes and therefore help to weaken its precipitation in the oxidative condition. In addition, the simulation experiments with artificial coastal waters demonstrated that this complexation could ensure that at least 25 % of the initial Fe load dissolve in coastal water, implying large part of dissolved iron in rivers draining from peatlands could be transported through the estuarine zones. Considering the wide distribution of peatlands globally, the higher concentration of Fe in peatlands, and the enhancement of marine organisms by Fe, the geochemical interactions between iron and phenolics originated from peatlands are of important significance to transport bio-available iron from terrestrial system to oceans.