Gel electromembrane microextraction followed by ion chromatography for direct determination of iodine in supplements and fortified food samples: Green chemistry for food analysis.

In this study, a sensitive, selective, and environmentally friendly analytical method for direct extraction and preconcentration of iodine was developed. Iodine, as an iodate ion or iodide ion, was simultaneously extracted and preconcentrated by gel electromembrane microextraction (G-EME) and analyzed for total iodine by ion chromatography. The total iodine was determined by combining the peak areas of both iodate and iodide ions. Under the optimized conditions, linear calibration for iodine using a mixture of iodate and iodide ions was obtained from 10 to 100 µg L-1 (r2 > 0.996). The detection limit was 7.0 µg L-1. Recoveries of spiked iodine (as iodate) in the samples were greater than 90%. The method was applied for the determination of iodine in dietary supplements and fortified food samples, i.e., iodine-enriched eggs. Our developed method could be directly applied for the determination of iodine in different matrix samples including eggs without a pretreatment step.

Rapid screening and characterization of natural antioxidants in Polygonum viviparum by an on-line system integrating the pressurised liquid micro-extraction, HPLC-DAD-QTOF-MS/MS analysis and antioxidant assay.

Rapid discovery of active ingredients from complex matrices is one of great challenges for modern drug development. Traditional methods often require many sample treatment steps, including an extraction step with exclusively dedicated solvents followed by repeated separation and activities assessment. This present work described an integrated analytical setup for natural antioxidants discovery in which the online extraction (OLE) of a solid sample is directly coupled to its analysis by high performance liquid chromatography-diode array detector-quadrupole time-of-flight tandem mass spectrometry and 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) antioxidant assay (OLE-HPLC-DAD-QTOF-MS/MS-ABTS). This developed approach makes sample extraction, chromatographic separation and chemical detection, and antioxidant assay integrated into a single HPLC injection and was successfully applied for the rapid discovery of natural antioxidant bioactives from Polygonum viviparum. A total of 21 secondary metabolites were characterized according to their retention times, ultraviolet (UV) spectra, exact mass and fragmentation ions in MS/MS spectra, and 18 of them displayed antioxidant activity (response as negative peaks in antioxidant assay). This work describes a simple, green and efficient approach to minimize the sample consumption (only 0.4 mg was required) and eliminate complex sample treatment procedures. The developed OLE-HPLC-DAD-QTOF-MS/MS-ABTS system offers new perspectives for rapid chemical profiling of natural products and their antioxidants discovery.

Comparison and application of two microextractions based on syringe membrane filter.

Two proposed syringe membrane filter solid phase microextraction and syringe membrane filter liquid/solid phase microextraction, coupled separately with high performance liquid chromatography, were developed for simultaneous enrichment and determination of the trace level of flavonoids in traditional Chinese medicine. In syringe membrane filter solid phase microextraction, the membrane of syringe membrane filter was served as a solid adsorption film to adsorb target analytes. And in syringe membrane filter liquid/solid phase microextraction, the membrane of syringe membrane filter was used as not only an adsorption phase, but also as a holder of extraction solvent to realize liquid-solid synergistic extraction. The simple operation, rapid extraction, and little or no organic solvent consumption make the two approaches very interesting. To evaluate the two proposed approaches, the crucial parameters affecting the enrichment factors of target analytes were investigated and optimized, and the two microextractions were intercompared. Moreover, their microextraction mechanisms were analyzed and described. Under the optimized conditions, both the new approaches achieved good linearities, accuracies, precisions, and low limits of detection, and the two methods were successfully applied for concentration of the flavonoids in traditional Chinese medicines.

Preparation of a new three-component deep eutectic solvent and its use as an extraction solvent in dispersive liquid-liquid microextraction of pesticides in green tea and herbal distillates.

BACKGROUND: A new solvent, deep eutectic solvent, in which there is growing interest, has been prepared and used as an extraction solvent in the dispersive liquid-liquid method of microextraction. To prepare the solvent, dichloroacetic acid, l-menthol, and n-butanol are mixed at a molar ratio of 4:1:1 and the deep eutectic solvent is formed after heating. Then a dispersive liquid-liquid microextraction method using the prepared solvent is used for the extraction and preconcentration of some pesticides from an aqueous sample. To carry out the procedure, the deep eutectic solvent is mixed with methanol and rapidly injected by a syringe into the aqueous sample containing the analytes. After centrifuging, an aliquot of the sedimented phase is injected into the gas chromatograph. The influence of several variables on the extraction efficiency was investigated and optimized. RESULTS: Extraction recoveries and enrichment factors were obtained in the ranges of 53-86% and 1760-2853, respectively. The intra- (n = 6) and inter-day (n = 5) precision of the method was satisfactory, with relative standard deviations ≤ 7% obtained at two concentrations of 10 and 50 µg L-1 of each analyte. Moreover, detection and quantification limits for the target analytes were obtained in the ranges of 0.11-0.23 and 0.38-0.74 µg L-1 , respectively. CONCLUSION: Different samples, including green tea, rose water, lemon balm, mint, and pussy willow distillates were analyzed successfully using the method that was developed, and chlorpyrifos was found in rose water at a concentration of 17 ± 1 µg L-1 (n = 3). © 2019 Society of Chemical Industry.

Deep eutectic solvent based homogeneous liquid-liquid extraction coupled with in-syringe dispersive liquid-liquid microextraction performed in narrow tube; application in extraction and preconcentration of some herbicides from tea.

A homogeneous liquid-liquid extraction performed in narrow tube coupled to in-syringe-dispersive liquid-liquid microextraction based on deep eutectic solvent has been developed for the extraction of six herbicides from tea samples. In this method, sodium chloride as a separation agent is filled into the narrow tube and the tea sample is placed on top of the salt. Then a mixture of deionized water and deep eutectic solvent (water miscible) is passed through the tube. In this procedure, the deep eutectic solvent is realized as tiny droplets in contact with salt. By passing the droplets from the tea layer placed on the salt layer, the analytes are extracted into them. After collecting the solvent as separated layer, it is mixed with another deep eutectic solvent (choline chloride/butyric acid) and the mixture is dispersed into deionized water placed in a syringe. After adding acetonitrile to break up the cloudy state, the collected organic phase is injected into gas chromatography-mass spectrometry. Under optimal conditions, limits of detection and quantification in the ranges of 2.6-8.4 and 9.7-29 ng/kg, respectively, were obtained. The extraction recoveries and enrichment factors in the ranges of 70-89% and 350-445 were obtained, respectively.

Rapid determination of hydrophilic phenols in olive oil by vortex-assisted reversed-phase dispersive liquid-liquid microextraction and screen-printed carbon electrodes.

A novel approach is presented to determine hydrophilic phenols in olive oil samples, employing vortex-assisted reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) for sample preparation and screen-printed carbon electrodes for voltammetric analysis. The oxidation of oleuropein, hydroxytyrosol, caffeic acid, ferulic acid and tyrosol was investigated, being caffeic acid and tyrosol selected for quantification. A matrix-matching calibration using sunflower oil as analyte-free sample diluted with hexane was employed to compensate matrix effects. Samples were analyzed under optimized RP-DLLME conditions, i.e., extractant phase, 1M HCl; extractant volume, 100µL; extraction time, 2min; centrifugation time, 10min; centrifugation speed, 4000rpm. The working range showed a good linearity between 0.075 and 2.5mgL-1 (r = 0.998, N = 7) for caffeic acid, and between 0.075 and 3mgL-1 (r = 0.999, N = 8) for tyrosol. The methodological limit of detection was empirically established at 0.022mgL-1 for both analytes, which is significantly lower than average contents found in olive oil samples. The repeatability was evaluated at two different spiking levels (i.e., 0.5mgL-1 and 2mgL-1) and coefficients of variation ranged from 8% to 11% (n = 5). The applicability of the proposed method was tested in olive oil samples of different quality (i.e., refined olive oil, virgin olive oil and extra virgin olive oil). Relative recoveries varied between 83% and 108% showing negligible matrix effects. Finally, fifteen samples were analyzed by the proposed method and a high correlation with the traditional Folin-Ciocalteu spectrophotometric method was obtained. Thereafter, the concentrations of the fifteen oil samples were employed as input variables in linear discriminant analysis in order to distinguish between olive oils of different quality.

Simultaneous dispersive liquid-liquid microextraction derivatisation and gas chromatography mass spectrometry analysis of subcritical water extracts of sweet and sour cherry stems.

Cherry stems have been used in traditional medicine mostly for the treatment of urinary tract infections. Extraction with subcritical water, according to its selectivity, efficiency and other aspects, differs substantially from conventional extraction techniques. The complexity of plant subcritical water extracts is due to the ability of subcritical water to extract different chemical classes of different physico-chemical properties and polarities in a single run. In this paper, dispersive liquid-liquid microextraction (DLLME) with simultaneous derivatisation was optimised for the analysis of complex subcritical water extracts of cherry stems to allow simple and rapid preparation prior to gas chromatography-mass spectrometry (GC-MS). After defining optimal extracting and dispersive solvents, the optimised method was used for the identification of compounds belonging to different chemical classes in a single analytical run. The developed sample preparation protocol enabled simultaneous extraction and derivatisation, as well as convenient coupling with GC-MS analysis, reducing the analysis time and number of steps. The applied analytical protocol allowed simple and rapid chemical screening of subcritical water extracts and was used for the comparison of subcritical water extracts of sweet and sour cherry stems. Graphical abstract DLLME GC MS analysis of cherry stem extracts obtained by subcritical water.

Simple and Rapid Dual-Dispersive Liquid-Liquid Microextraction as an Innovative Extraction Method for Uranium in Real Water Samples Prior to the Determination of Uranium by a Spectrophotometric Technique.

An innovative, rapid, and simple dual-dispersive liquid-liquid microextraction (DDLL-ME) approach was used to extract uranium from real samples for the first time. The main objective of this study was to disperse extraction solvent by using an air-agitated syringe system to overcome matrix effects and avoid dispersion of hazardous dispersive organic solvents by using heat. The DDLL-ME method consisted of two dispersive liquid-liquid extraction steps with chloroform as the extracting solvent. Uranium formed complexes with 4-(2-thiazolylazo) resorcinol in the aqueous phase and was extracted in extracting solvent (chloroform) after the first dispersive liquid-liquid process. Uranium was then back-extracted in the acidic aqueous phase in a second dispersive liquid-liquid process. Finally, uranium was determined by a spectrophotometric detection technique. The variables that played a key role in the proposed method were studied and optimized. The LOD and sensitivity enhancement factor for uranium were found to be 0.60 µg/L and 45, respectively, under optimized conditions. Calibration graphs were found to be linear in the range of 5.0-600 µg/L. The RSD was 2.5%. Reliability of the proposed method was verified by analyzing certified reference material TM-28.3.

In-syringe dispersive liquid-liquid microextraction based on the solidification of ionic liquids for the determination of benzoylurea insecticides in water and tea beverage samples.

A novel in-syringe dispersive liquid-liquid microextraction based on the solidification of ionic liquids (in-syringe SIL-DLLME) was coupled with high-performance liquid chromatography-ultraviolet detector (HPLC-UVD) to detect five benzoylurea insecticides (BUs) in water and tea beverage samples. In this method, the hydrophobic ionic liquid [N8881][PF6] was formed in situ by the metathesis reaction between [N8881]Cl and the anion-exchange reagent KPF6 to extract the target analytes. The whole extraction procedure was performed in a syringe. The solidified extractant could be separated from the aqueous phase by exposing the emulsified extraction solution to an ice bath and then easily collected by squeezing out the aqueous phase through the prepared NWPP-based needle. Various parameters affecting the extraction efficiency, such as the amount of [N8881]Cl, the molar ratio of [N8881]Cl to KPF6, salt addition, cooling time, solution temperature, sample pH and sample volume, were evaluated. Under the optimized conditions, the proposed method was validated with satisfactory results: good linearities with coefficients of determination greater than 0.99 were obtained in the range of 2-500µgL-1; the limits of detection varied between 0.29 and 0.59µgL-1; the recoveries of the five benzoylurea insecticides ranged from 85.93% to 90.52%; and the intra-day (n=3) and inter-day (n=3) relative standard deviations were less than 5.36%. Finally, the proposed method was successfully used for the determination of BUs in real water and tea beverage samples.

Ultrasound-assisted dispersive liquid-liquid microextraction of tetracycline drugs from egg supplements before flow injection analysis coupled to a liquid waveguide capillary cell.

A simple, rapid, and efficient ultrasound-assisted dispersive liquid-liquid microextraction (US-DLLME) method was developed for extraction of tetracycline residues from egg supplement samples, with subsequent determination by flow injection analysis (FIA) coupled to a liquid waveguide capillary cell (LWCC) and a controlled temperature heating bath. Tetracyclines react with diazotized p-sulfanilic acid, in a slightly alkaline medium, to form azo compounds that can be measured at 435 nm. The reaction sensitivity improved substantially (5.12-fold) using an in-line heating temperature of 45 °C. Multivariate methodology was used to optimize the factors affecting the extraction efficiency, considering the volumes of extraction and disperser solvents, sonication time, extraction time, and centrifugation time. Good linearity in the range 30-600 µg L(-1) was obtained for all the tetracyclines, with regression coefficients (r) higher than 0.9974. The limits of detection ranged from 6.4 to 11.1 µg L(-1), and the recoveries were in the range 85.7-96.4 %, with relative standard deviation lower than 9.8 %. Analyte recovery was improved by approximately 6 % when the microextraction was assisted by ultrasound. The results obtained with the proposed US-DLLME-FIA method were confirmed by a reference HPLC method and showed that the egg supplement samples analyzed were suitable for human consumption.

Dispersive liquid-liquid microextraction based on amine-functionalized Fe3O4 nanoparticles for the determination of phenolic acids in vegetable oils by high-performance liquid chromatography with UV detection.

A novel dispersive liquid-liquid microextraction method based on amine-functionalized Fe3O4 magnetic nanoparticles was developed for the determination of six phenolic acids in vegetable oils by high-performance liquid chromatography. Amine-functionalized Fe3O4 was synthesized by a one-pot solvothermal reaction between Fe3O4 and 1,6-hexanediamine and characterized by transmission electron microscopy and Fourier transform infrared spectrophotometry. A trace amount of phosphate buffer solution (extractant) was adsorbed on bare Fe3O4-NH2 nanoparticles by hydrophilic interaction to form the "magnetic extractant". Rapid extraction could be achieved while the "magnetic extractant" on amine-functionalized Fe3O4 nanoparticles was dispersed in the sample solution by vortexing. After extraction, the "magnetic extractant" was collected by application of an external magnet. Some important parameters, such as pH and volume of extraction and desorption solvents, the extraction and desorption time needed were carefully investigated and optimized to achieve the best extraction efficiency. Under the optimal conditions, satisfactory extraction recoveries were obtained for the six phenolic acids in the range of 84.2-106.3%. Relative standard deviations for intra- and inter-day precisions were less than 6.3 and 10.0%, respectively. Finally, the established method was successfully applied for the determination of six phenolic acids in eight kinds of vegetable oils.

Sensitive quantitation of polyamines in plant foods by ultrasound-assisted benzoylation and dispersive liquid-liquid microextraction with the aid of experimental designs.

A new method involving ultrasound-assisted benzoylation and dispersive liquid-liquid microextraction was optimized with the aid of chemometrics for the extraction, cleanup, and determination of polyamines in plant foods. Putrescine, cadaverine, spermidine, and spermine were derivatized with 3,5-dinitrobenzoyl chloride and extracted by dispersive liquid-liquid microextraction using acetonitrile and carbon tetrachloride as dispersive and extraction solvents, respectively. Two-level full factorial design and central composite design were applied to select the most appropriate derivatization and extraction conditions. The developed method was linear in the 0.5-10.0 mg/L range, with a R(2) ≥ 0.9989. Intra- and interday precisions ranged from 0.8 to 6.9% and from 3.0 to 10.3%, respectively, and the limit of detection ranged between 0.018 and 0.042 µg/g of fresh weight. This method was applied to the analyses of six different types of plant foods, presenting recoveries between 81.7 and 114.2%. The method is inexpensive, versatile, simple, and sensitive.

Three-phase hollow fiber liquid-phase microextraction based on a magnetofluid for the analysis of aristolochic acids in plasma by high-performance liquid chromatography.

A new and fast sample preparation technique based on three-phase hollow fiber liquid-phase microextraction with a magnetofluid was developed and successfully used to quantify the aristolochic acid I (AA-I) and AA-II in plasma after oral administration of Caulis akebiae extract. Analysis was accomplished by reversed-phase high-performance liquid chromatography with fluorescence detection. Parameters that affect the hollow fiber liquid-phase microextraction processes, such as the solvent type, pH of donor and acceptor phases, content of magnetofluid, salt content, stirring speed, hollow fiber length, extraction temperature, and extraction time, were investigated and optimized. Under the optimized conditions, the preconcentration factors for AA-I and AA-II were >627. The calibration curve for two AAs was linear in the range of 0.1-10 ng/mL with the correlation coefficients >0.9997. The intraday and interday precision was <5.71% and the LODs were 11 pg/mL for AA-I and 13 pg/mL for AA-II (S/N = 3). The separation and determination of the two AAs in plasma after oral administration of C. akebiae extract were completed by the validated method.

Design and implementation of an automated liquid-phase microextraction-chip system coupled on-line with high performance liquid chromatography.

An automated liquid-phase microextraction (LPME) device in a chip format has been developed and coupled directly to high performance liquid chromatography (HPLC). A 10-port 2-position switching valve was used to hyphenate the LPME-chip with the HPLC autosampler, and to collect the extracted analytes, which then were delivered to the HPLC column. The LPME-chip-HPLC system was completely automated and controlled by the software of the HPLC instrument. The performance of this system was demonstrated with five alkaloids i.e. morphine, codeine, thebaine, papaverine, and noscapine as model analytes. The composition of the supported liquid membrane (SLM) and carrier was optimized in order to achieve reasonable extraction performance of all the five alkaloids. With 1-octanol as SLM solvent and with 25 mM sodium octanoate as anionic carrier, extraction recoveries for the different opium alkaloids ranged between 17% and 45%. The extraction provided high selectivity, and no interfering peaks in the chromatograms were observed when applied to human urine samples spiked with alkaloids. The detection limits using UV-detection were in the range of 1-21 ng/mL for the five opium alkaloids presented in water samples. The repeatability was within 5.0-10.8% (RSD). The membrane liquid in the LPME-chip was regenerated automatically between every third injection. With this procedure the liquid membrane in the LPME-chip was stable in 3-7 days depending on the complexity of sample solutions with continuous operation. With this LPME-chip-HPLC system, series of samples were automatically injected, extracted, separated, and detected without any operator interaction.

A multiple hollow fibre liquid-phase microextraction method for the determination of halogenated solvent residues in olive oil.

The present paper describes a method based on the extraction of analytes by multiple hollow fibre liquid-phase microextraction and detection by ion-trap mass spectrometry and electron capture detectors after gas chromatographic separation. The limits of detection are in the range of 0.13-0.67 µg kg(-1), five orders of magnitude lower than those reached with the European Commission Official method of analysis, with three orders of magnitude of linear range (from the quantification limits to 400 µg kg(-1) for all the analytes) and recoveries in fortified olive oils in the range of 78-104 %. The main advantages of the analytical method are the absence of sample carryover (due to the disposable nature of the membranes), high enrichment factors in the range of 79-488, high throughput and low cost. The repeatability of the analytical method ranged from 8 to 15 % for all the analytes, showing a good performance.

Development of a simple combining apparatus to perform a magnetic stirring-assisted dispersive liquid-liquid microextraction and its application for the analysis of carbamate and organophosphorus pesticides in tea drinks.

This study introduced a simple combining apparatus for performing a magnetic stirring-assisted dispersive liquid-liquid microextraction (MSA-DLLME) for the detection of trace carbamate and organophosphorus pesticides in tea drinks coupled with high performance liquid chromatography. The simple combining apparatus was made up of a sample vial and a cut plastic dropper. The bulb end of the cut plastic dropper was inserted into the neck of the sample vial and the open tip end of the plastic dropper was then cut to an appropriate length. The combining apparatus made was then used to perform the MSA-DLLME. In this experiment, 1-octanol was injected into the tea drink sample solution and the extraction process accelerated by magnetic agitation. The sample solution turned clear and separated into two layers after leaving it alone for several minutes. The cut plastic dropper was gently put down into the sample vial, and then the liquid level of the sample solution elevated up to the tip of the plastic dropper for the collection of low-density extractant. Finally, the collected extractant was drawn out by a microsyringe and injected into the high performance liquid chromatography-diode-array detector for analysis. A series of extraction parameters were investigated and optimized. Under the most favorable conditions, high enrichment factors were obtained for carbofuran, carbaryl and isocarbophos (between 130 and 185). The limits of detection (S/N=3) were in the range of 0.13-0.61 µg L(-1), and the relative standard deviation varied below 7.8% (n=5). Additionally, good recoveries were obtained between 79.4% and 114.4% in the three tea drinks. The simple combining apparatus utilized in this MSA-DLLME method was shown to be economical, fast, and convenient for the collection of low density extractant.

Hollow fibre-based liquid phase microextraction combined with high-performance liquid chromatography for the analysis of flavonoids in Echinophora platyloba DC. and Mentha piperita.

A simple, inexpensive and efficient three phase hollow fibre liquid phase microextraction (HF-LPME) technique combined with HPLC was used for the simultaneous determination of flavonoids in Echinophora platyloba DC. and Mentha piperita. Different factors affecting the HF-LPME procedure were investigated and optimised. The optimised extraction conditions were as follows: 1-octanol as an organic solvent, pHdonor=2, pHacceptor=9.75, stirring rate of 1000rpm, extraction time of 80min, without addition of salt. Under these conditions, the enrichment factors ranged between 146 and 311. The values of intra and inter-day relative standard deviations (RSD) were in the range of 3.18-6.00% and 7.25-11.00%, respectively. The limits of detection (LODs) ranged between 0.5 and 7.0ngmL(-1). Among the investigated flavonoids quercetin was found in E. platyloba DC. and luteolin was found in M. piperita. Concentration of quercetin and luteolin was 0.015 and 0.025mgg(-1) respectively.

Comparison of dispersive liquid-liquid microextraction based on organic solvent and ionic liquid combined with high-performance liquid chromatography for the analysis of emodin and its metabolites in urine samples.

In this paper, two methods based on organic solvent dispersive liquid-liquid microextraction (OS-DLLME) and ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) coupled with high-performance liquid chromatography have been critically compared for analyzing emodin and its metabolites (aloe-emodin, anthraquinone-2-carboxylic acid, rhein, danthron, chrysophanol and physcion) in urine samples. Several important parameters influencing the extraction recoveries of DLLME were carefully optimized. Under optimal conditions, the enrichment factors (EFs) for emodin and its metabolites by OS-DLLME and IL-DLLME were within the range of 90-295 and 63-192 respectively; the relative standard deviations (RSDs, n=3) for intra-day and inter-day precision were lower than 7.2 and 8.7% by OS-DLLME, and lower than 5.7 and 6.4% by IL-DLLME; the recoveries of emodin and its metabolites were from 87.1 to 105% for OS-DLLME and from 94.8 to 103% for IL-DLLME, respectively. There were no significant deviations between the two methods for the determination of emodin and its metabolites. From the results of HPLC/UV of urine sample after DLLME, the metabolites aloe-emodin, rhein, chrysophanol and physcion were identified by comparing the retention times with the standards. From the results of HPLC/MS, anthraquinone-2-carboxylic acid and danthron as unreported metabolites of emodin were found.