Pressurized hot water extraction of insecticides from process dust--comparison with supercritical fluid extraction

Pressurized hot liquid water and steam were used to investigate the possibilities of extracting insecticides (carbofuran, carbosulfan, and imidacloprid) from contaminated process dust remaining from seed-pellet production. Extraction temperature was the most important parameter in influencing the extraction efficiency and rate of extraction, while varying the pressure had no profound effect. A clean-up procedure of the water extracts using solid phase extraction (SPE) was found to be necessary prior to final analysis by high-performance liquid chromatography (HPLC). Quantitative extraction (compared to a validated organic solvent extraction method) of imidacloprid was obtained at temperatures of 100-150 degrees C within 30 min extraction time. Temperatures above 150 degrees C were required to extract carbofuran efficiently. The most non-polar analyte of the investigated compounds, carbosulfan, gave no detectable concentrations with pressurized hot water extraction (PHWE). One reason might be its low solubility in water, and when attempts are made to increase its solubility by increasing the temperature it may degrade to carbofuran. This can explain recovery values above 100% for carbofuran at higher temperatures. A comparison of the PHWE results and those obtained with supercritical fluid extraction (SFE) revealed that PHWE is advantageous for polar compounds, where the solubility of the analyte in water is high enough that lower temperatures can be used. For non-polar compounds carbon dioxide based extraction is preferred unless the target analyte is highly thermostable.     

Pressurized hot water extraction of berberine, baicalein and glycyrrhizin in medicinal plants

Pressurized hot water extraction (PHWE) using a laboratory made system was applied for the extraction of thermally labile and reasonably polar components such as berberine in coptidis rhizoma, glycyrrhizin in radix glycyrrhizae/liquorice and baicalein in scutellariae radix. PHWE was carried out dynamically at a flow of 1 ml/min, temperature between 95 and 140 °C, an applied pressure of 10-20 bar and extraction time of 40 min. Extraction by PHWE was found to give efficiencies comparable to Soxhlet extraction for baicalein in scutellariae radix and sonication for berberine in coptidis rhizoma, and glycyrrhizin in radix glycyrrhizae. Effects of ethanol added into the water used in PHWE were explored. Pressurized liquid extraction (PLE) with methanol as solvent was used for extraction of baicalein in scutellariae radix. The marker compounds present in the various medicinal plant extracts were determined by gradient elution HPLC.     

Evaluation of the extraction efficiency of thermally labile bioactive compounds in Gastrodia elata Blume by pressurized hot water extraction and microwave-assisted extraction

Our earlier work showed that the stability of the bioactive compounds gastrodin (GA) and vanillyl alcohol (VA) in Gastrodia elata Blume behaved differently with varying compositions of water-ethanol using pressurized liquid extraction (PLE) at room temperature. To have a better understanding of the extraction process of these thermally labile compounds under elevated temperature conditions, pressurized hot water extraction (PHWE) and microwave-assisted extraction (MAE) methods were proposed. PHWE and MAE showed that GA and VA could be extracted using pure water under optimized conditions of temperature and extraction time. The extraction efficiency of GA and VA by the proposed methods was found to be higher or comparable to heating under reflux using water. The marker compounds present in the plant extracts were determined by RP-HPLC. The optimized conditions were found to be different for the two proposed methods on extraction of GA and VA. The method precision (RSD, n=6) was found to vary from 0.92% to 3.36% for the two proposed methods on different days. Hence, PHWE and MAE methods were shown to be feasible alternatives for the extraction of thermally labile marker compounds present in medicinal plants.     

Pressurized hot water extraction (PHWE)

Pressurized hot water extraction (PHWE) has become a popular green extraction method for different classes of compounds present in numerous kinds of matrices such as environmental, food and botanical samples. PHWE is also used in sample preparation to extract organic contaminants from foodstuff for food safety analysis and soils/sediments for environmental monitoring purposes. The main parameters which influence its extraction efficiency are namely the temperature, extraction time, flow rates and addition of modifiers/additives. Among these different parameters studied, temperature is described as the most important one. It is reported that the extraction of certain compounds is rather dependent on pressurized water with different applied temperature. Thus, the stability and reduced solubilities of certain compounds at elevated temperatures are highlighted in this review. With some modifications, a scaled-up PHWE could extract a higher amount of desirable compounds from solid and powdered samples such as plant and food materials. The PHWE extracts from plants are rich in chemical compounds or metabolites which can be a potential lead for drug discovery or development of disease-resistant food crops.     

Ethanol-free extraction of curcumin and antioxidant activity of components from wet Curcuma longa L. by liquefied dimethyl ether

As a solvent, ethanol can extract a wide range of polar substances, but its consumption is sometimes avoided for religious and cultural reasons. In this study, liquefied dimethyl ether (DME) was used to extract curcumin and antioxidants from highly moist, untreated turmeric. Higher amounts of curcumin (7.94 mg/g dry weight (DW)) were extracted using liquified DME compared with ethanol (6.77 mg/g DW). Almost all the water and 5.10 mg/g DW of lipids were extracted from raw turmeric using liquefied DME, corresponding to 56 % the amount extracted using ethanol. In addition, microscopic and spectroscopic analyses revealed that liquefied DME neither destroyed cell walls nor extracted cellulose. However, liquefied DME had a slightly lower extraction capacity for total phenolic compounds than ethanol and slightly lower antioxidant effect. DME extracts an equivalent amount of curcumin as ethanol and only slightly fewer antioxidants while simultaneously avoiding sun-drying degradation and prolonged freeze-drying.     

Evaluation of surfactant‐assisted pressurized hot water extraction for marker compounds in Radix Codonopsis pilosula using liquid chromatography and liquid chromatography/electrospray ionization mass spectrometry

In the move towards the elimination of organic solvents in the extraction process in botanicals, a new method combining surfactant and pressurized hot water extraction (PWHE) with an applied temperature below the boiling point and lower pressure from 10 to 20 bar was developed for the analysis of marker compounds that are reasonably hydrophobic such as tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol and tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol‐O‐β‐D‐glucoside in Radix Codonopsis pilosula (DangShen). Because reference substances for the proposed botanicals were not available, a method was developed to isolate the marker compounds in Radix Codonopsis pilosula. Other than surfactant‐assisted PHWE, the marker compounds present in Radix Codonopsis pilosula were extracted using pressurized liquid extraction (PLE) with methanol and PHWE with a mixture of water/ethanol (80:20). The extracts were analyzed using liquid chromatography and liquid chromatography/electrospray ionization mass spectrometry. With surfactant‐assisted PHWE, the effects of different added surfactants such as sodium dodecyl sulfate and Triton X‐100 was studied. Surfactant assisted PHWE with Triton X‐100 proved to be at least equivalent or better compared to Soxhlet extraction in terms of quantitative analysis of marker compounds in Radix Codonopsis pilosula. The method precision was less than 8% (RSD, n = 6). The presence of surfactants in PHWE was found to enhance the solubility of target compounds naturally occurring in medicinal plants.     

Pressurized hot water extraction of bioactive or marker compounds in botanicals and medicinal plant materials

To reduce the use of organic solvent, pressurized hot water extraction (PHWE) has been shown to be a feasible option for the extraction of bioactive and marker compounds in botanicals and medicinal plants. The parameters that may affect the extraction efficiencies in PHWE include temperature, extraction time and addition of small percentage of organic solvent or surfactants. Currently, applications of PHWE for the extraction of thermally labile compounds in botanicals are still rather limited. PHWE with and without the additional of a small percentage of organic solvent such as ethanol is highly suited for the chemical standardization and quality control of medicinal plants. At the same time, it can be applied at the pilot scale as a manufacturing process for medicinal plants. Surfactant assisted PHWE was found to enhance the extraction of thermally labile and more hydrophobic species in medicinal plants at a lower temperature. The addition of small amount of surfactants in PHWE is highly suited for the determination of bioactive or marker compounds in medicinal plants. With proper optimization, PHWE was observed to have good extraction efficiency and precision when compared to other reference methods of extraction.     

Evaluation of pressurized liquid extraction and pressurized hot water extraction for tanshinone I and IIA in Salvia miltiorrhiza using LC and LC-ESI-MS

Pressurized liquid extraction (PLE) and pressurized hot water extraction (PHWE) using a laboratory-made system are applied for the extraction of thermally labile components such as tanshinone I and IIA in Salvia miltiorrhiza. PLE and PHWE are carried out dynamically at a flow of 1 mL/min, temperature between 95-140 degrees C, applied pressure of 10-20 bars, and extraction times of 20 and 40 min, respectively. Effects of ethanol added into the water used in PHWE are explored. PLE is found to give comparable or higher extraction efficiencies compared with PHWE with reference to Soxhlet extraction for tanshinone I and IIA in Salvia miltiorrhiza. The tanshinone I and IIA present in the various medicinal plant extracts are determined by liquid chromatography and liquid chromatography-mass spectrometry.     

Comparison of gas chromatography-mass spectrometry and capillary electrophoresis in analysis of phenolic compounds extracted from solid matrices with pressurized hot water

Self-constructed pressurized hot water extraction (PHWE) equipment was used in dynamic mode to extract spiked phenolic compounds (phenol, 3-methylphenol, 4-chloro-3-methylphenol and 3,4-dichlorophenol) from sea sand and soil. Phenols were analyzed by both gas chromatography-mass spectrometry (GC-MS) and capillary zone electrophoresis (CZE) to compare the techniques and to find out if CZE is a suitable tool for analysis of phenols extracted from environmental matrix. Good recoveries of phenols spiked in sea sand were achieved at all PHWE temperatures (50, 100, 200, 300 C). GC-MS studies showed that phenols were selectively extracted from soil at 50 C but various other compounds (e.g. polyaromatic hydrocarbons) were extracted along with the phenols at 300 degrees C. In the case of CZE, phenols extracted from the soil, at 300 C were separated with good resolution at pH 9.7, and co-extracted compounds did not interfere with the analysis. The analytical values obtained by GC-MS and CZE were generally of similar magnitude.     

Solid-phase micro-extraction procedure for the determination of 1,3-dichloro-2-propanol in water by on-fibre derivatisation with bis(trimethylsilyl)trifluoroacetamide

The headspace solid-phase micro-extraction technique with on-fibre derivatisation followed by gas chromatography-tandem mass spectrometry has been evaluated for the analysis of 1,3-dichloro-2-propanol in water. An asymmetric factorial design has been performed to study the influence of five experimental factors: extraction time and temperature, derivatisation time and temperature and pH. The best extraction performance is achieved in the headspace mode, with 5 mL stirred water samples (pH 4) containing 1.3 g of NaCl, equilibrated for 30 min at 25 °C, using divinylbenzene-carboxen-polydimethylsiloxane as the fibre coating. On-fibre derivatisation has been used for the first time with 50 μL of bis(trimethylsilyl)trifluoroacetamide at 25 °C during 15 min, leading to effective yields. The proposed method provides high sensitivity, good linearity and repeatability (relative standard deviation of 5.1% for 10 ng mL⁻¹ and n = 5). The limits of detection and quantification were 0.4 and 1.4 ng mL⁻¹, respectively. Analytical recoveries obtained for different water samples were approx. 100%.     

Microemulsion electrokinetic chromatography for separation and analysis of curcuminoids in turmeric samples

Microemulsion EKC (MEEKC) was developed for quantitative analysis of curcuminoids, such as curcumin (C), demethoxycurcumin (D), and bis-demethoxycurcumin (B). MEEKC separation of curcuminoids was optimized, and a change in resolution was explained using a modified equation for resolution in MEEKC without electroosmosis. The suitable MEEKC conditions for separation of curcuminoids were obtained to be the microemulsion buffer containing 50 mM phosphate buffer at pH 2.5, 1.1% v/v n-octane as oil droplets, 180 mM SDS as surfactant, 890 mM 1-butanol as cosurfactant, and 25% v/v 2-propanol as organic cosolvent; applied voltage of -15 kV; and separation temperature 25 degrees C. Achieved baseline resolution of C:D and D:B was obtained with R(s) -2.4 and analysis time within 18 min. In addition, high accuracy and precision of the method were obtained. This MEEKC method was used for quantitative determination of individual curcuminoids in medicinal turmeric capsules and powdered turmeric used as coloring additive in food, with simple sample preparation such as solvent extraction, dilution, and filtration, and without cleaning up by SPE.     

Analysis and occurrence of seven artificial sweeteners in German waste water and surface water and in soil aquifer treatment (SAT)

A method for the simultaneous determination of seven commonly used artificial sweeteners in water is presented. The analytes were extracted by solid phase extraction using Bakerbond SDB 1 cartridges at pH 3 and analyzed by liquid chromatography electrospray ionization tandem mass spectrometry in negative ionization mode. Ionization was enhanced by post-column addition of the alkaline modifier Tris(hydroxymethyl)amino methane. Except for aspartame and neohesperidin dihydrochalcone, recoveries were higher than 75% in potable water with comparable results for surface water. Matrix effects due to reduced extraction yields in undiluted waste water were negligible for aspartame and neotame but considerable for the other compounds. The widespread distribution of acesulfame, saccharin, cyclamate, and sucralose in the aquatic environment could be proven. Concentrations in two influents of German sewage treatment plants (STPs) were up to 190 μg/L for cyclamate, about 40 μg/L for acesulfame and saccharin, and less than 1 μg/L for sucralose. Removal in the STPs was limited for acesulfame and sucralose and >94% for saccharin and cyclamate. The persistence of some artificial sweeteners during soil aquifer treatment was demonstrated and confirmed their environmental relevance. The use of sucralose and acesulfame as tracers for anthropogenic contamination is conceivable. In German surface waters, acesulfame was the predominant artificial sweetener with concentrations exceeding 2 μg/L. Other sweeteners were detected up to several hundred nanograms per liter in the order saccharin ≈ cyclamate > sucralose. Figure Some artificial sweeteners are excreted unchanged and in particular acesulfame is a perfect tracer for municipal waste water Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Antioxidant activity of grape skin aqueous extracts from pressurized hot water extraction combined with electron paramagnetic resonance spectroscopy

Pressurized hot water extraction (PHWE) was employed to prepare extracts from dried grape skin of two wine grape varieties (St. Laurent and Alibernet) at various temperatures (from 40 up to 120 °C) and amounts of sample (0.5, 1.0 and 1.5 g). To assess the antioxidant activity of the extracts, electron paramagnetic resonance (EPR) spectroscopy was applied involving DPPH and ABTS⁺ assays. Other extract characteristics including HPLC profile of anthocyanins and total phenolic compound content were obtained as well. PHWE has also been compared with earlier results of extractions of the same grape skin samples with compressed methanol and compressed ethanol under the conditions of pressurized fluid extraction (PFE). From this comparison, PHWE emerges as the more benign and efficient extraction method to recover valuable phenolic antioxidants from grape skins for the prospective use in functional food supplements.     

Release characteristic and stability of curcumin incorporated in β-chitin non-woven fibrous sheet using Tween 20 as an emulsifier

β-Chitin sheets containing curcumin—a naturally occurring substance that possesses several advantages biological properties including antioxidant, antimicrobial, and anti-inflammatory activities—were fabricated by the paper-making process using a water-based system. Using the chitin matrix consisting of small fibers could give rise to a large surface area that could improve the diffusion of solvent and reagent, so as to make the material suitable for use as support and carrier for drugs. Tween 20 was used as an emulsifier to improve water solubility of the curcumin. The change in surface morphology of the fabricated chitin sheets after curcumin loading was indicated by scanning electron microscope (SEM). A rough surface consisting of fibrous chitin could be seen both on the neat chitin sheets and the curcumin-loaded chitin sheets, while the increase in the curcumin content led the sheets to show an occurrence of spots. Investigation of the release behavior of the curcumin loaded into the chitin sheet was carried out by the total immersion method in an acetate buffer solution, pH 5.5, at 37 °C (simulating human skin). It was found that the amounts of loaded curcumin affected the release characteristics of the curcumin from the chitin sheet as a function of releasing time. In addition, the Tween 20 played an important role in the release ability of the curcumin to an exterior solution and in the stability of the curcumin present in the chitin sheet. It could be postulated that the water solubility, release ability, and stability of the curcumin incorporated into the β-chitin sheets was improved by the inclusion of curcumin into the cores of the Tween 20 micelles and the β-chitin non-woven fibrous sheet containing curcumin could be a promising candidate for would care materials.     

Improvement of the Solubilization and Extraction of Curcumin in an Edible Ternary Solvent Mixture

A water-free, ternary solvent mixture consisting of a natural deep eutectic solvent (NADES), ethanol, and triacetin was investigated concerning its ability to dissolve and extract curcumin from Curcuma longa L. To this purpose, 11 NADES based on choline chloride, acetylcholine, and proline were screened using UV–vis measurements. A ternary phase diagram with a particularly promising NADES, based on choline chloride and levulinic acid was recorded and the solubility domains of the monophasic region were examined and correlated with the system’s structuring via light scattering experiments. At the optimum composition, close to the critical point, the solubility of curcumin could be enhanced by a factor of >1.5 with respect to acetone. In extraction experiments, conducted at the points of highest solubility and evaluated via HPLC, a total yield of ~84% curcuminoids per rhizome could be reached. Through multiple extraction cycles, reusing the extraction solvent, an enrichment of curcuminoids could be achieved while altering the solution. When counteracting the solvent change, even higher concentrated extracts can be obtained.     

Hollow fiber liquid phase microextraction as a preconcentration and clean-up step after pressurized hot water extraction for the determination of non-steroidal anti-inflammatory drugs in sewage sludge

A method for the quantitative determination of non-steroidal anti-inflammatory drugs (NSAIDs) in sewage sludge was developed and validated. The target compounds were extracted using pressurized hot water extraction (PHWE) and then purified and preconcentrated by three-phase hollow fiber liquid phase microextraction (HF-LPME) followed by LC–ESI-MS analysis. The PHWE was optimized with regard to the pH of solvent as well as other operational parameters. The optimum conditions were 0.01 M NaOH as the extraction solvent, temperature of 120 °C, pressure of 100 bar, static time 5 min, 5 cycles, flush volume 90% and purge time 60 s. Spike recoveries for sludge samples spiked at 200 ng g⁻¹ were in the range of 101–109% but for the native drugs in non-spiked sludge samples, recoveries were 38.9%, 59.8%, 90.3% and 47.8% for ketoprofen, naproxen, diclofenac and ibuprofen, respectively. Donor phase pH, ionic strength and extraction time were optimized for HF-LPME after PHWE. The optimum conditions were 2 h extraction at pH 1.5 without salt addition. Enrichment factors in the range of 947–1213 times were achieved (extraction recoveries were 23.6–30.3%) for HF-LPME after PHWE. The matrix effect on the ionization of drugs in LC–ESI-MS was also investigated. The results show that there is a smaller matrix effect (−8.9% to +14.6%) in comparison with other published values obtained using solid phase extraction (SPE) for clean-up after pressurized liquid extraction (PLE). Method detection limits (MDLs) and method quantification limits (MQLs) for different drugs were in the range of 0.4–3.7 ng g⁻¹ and 1.5–12.2 ng g⁻¹ in dried sludge samples, respectively. The characteristics of the proposed method were compared with those of other published works. The considerably lower ion suppression/enhancement and minimum use of organic solvents (a few microliters of di-n-hexyl ether) in the sample preparation step are two highlighted advantages of the proposed method in comparison with previously published works. The method was applied to determine NSAIDs in sewage sludge from Källby wastewater treatment plant (Lund, Sweden) in April, June, August and October 2010. The highest concentration level was recorded for ibuprofen in the April sewage sludge sample (588 ng g⁻¹) and all of the selected NSAIDs were detected in all the samples analyzed.     

Gas chromatography-mass spectrometry following pressurized hot water extraction and solid-phase microextraction for quantification of eucalyptol, camphor, and borneol in Chrysanthemum flowers

Chrysanthemum flower is a common traditional Chinese medicine (TCM). In this work, pressurized hot water extraction (PHWE) followed by headspace solid-phase microextraction (HS-SPME) and GC-MS was developed for the determination of three main active volatile compounds of eucalyptol, camphor, and borneol in Chrysanthemum flowers from four different growing areas in China by internal standard method. The parameters of PHWE and HS-SPME were optimized. The method was also validated. The results showed that PHWE-SPME-GC-MS is a simple, rapid, efficient, and solvent-free technique for the quantitative determination of eucalyptol, camphor, and borneol in TCMs and is potentially useful for the TCM quality assessment.     

The sensitive capillary electrophoretic‐LIF method for simultaneous determination of curcuminoids in turmeric by enhancing fluorescence intensities of molecules upon inclusion into (2‐hydroxypropyl)‐β‐cyclodextrin

Curcuminoids have received great attention in the past decades due to their health benefit properties. The aim of this study is to develop a very simple, rapid, and sensitive capillary zone electrophoresis technique coupled with a laser induced fluorescence detector (LIF) for the simultaneous determination of three major curcuminoids of turmeric, namely, curcumin, demethoxy curcumin (DMC), and bisdemethoxy curcumin (BDMC). Background electrolyte was selected as borate at pH 9.6 and (2‐hydroxypropyl)‐β‐cyclodextrin (2‐HP‐β‐CD) was added to prevent rapid alkali degradation of curcuminoids in buffer and to increase fluorescence intensities of molecules. With the addition of 2‐HP‐β‐CD to the separation electrolyte, the fluorescence signal intensities of curcuminoids were enhanced considerably by 30, 40, and 54 fold for curcumin, DMC, and BDMC, respectively. The three curcuminoids of turmeric were fully separated and quantified in less than 4.5 min. The repeatability of the peak areas of curcuminoids for intra‐day and inter‐day experiments was in the satisfactory range of 2.26 and 2.55%, respectively. The LOD and LOQ values for the developed method were equal to or less than 0.081 and 0.270 μg/mL, respectively, for all curcuminoids. The developed method was successfully applied to find curcuminoids amount in turmeric samples and herbal supplements.     

Isolation of flavonoids from aspen knotwood by pressurized hot water extraction and comparison with other extraction techniques

Pressurized hot water extraction (PHWE) conditions (time, temperature, pressure) were optimized for the extraction of naringenin and other major flavonoids (dihydrokaempferol, naringin) from knotwood of aspen. Extracts were analysed by GC-FID, GC-MS, HPLC-UV and HPLC-MS. The results were compared with those obtained by Soxhlet, ultrasonic extraction and reflux in methanol. Flavonoids were most efficiently extracted with PHWE at 150 °C and 220 bar with 35 min extraction time. Soxhlet with methanol gave slightly higher recoveries, but an extraction time of 48 h was required. Naringenin concentration was highest in knotwood (1.15% dry weight) and much lower in the sapwood. PHWE proved to be cheap, fast and effective for the isolation of biofunctional flavonoids from aspen knotwood, producing higher recoveries than 24 h Soxhlet extraction, sonication or 24 h reflux.     

Solubility and pKa of select pharmaceuticals in water,ethanol, and 1-octanol

Solubilities of six pharmaceuticals, namely nadolol, atenolol, bifonazole, nimesulide, estrone, mefenamic acid at constant pH, were measured over the range of temperature from (240 to 340) K in three important for drug solvents: water, ethanol, and 1-octanol using the dynamic method and spectroscopic UV–Vis method. Dissociation constants and corresponding pK_a values of the drugs were obtained with the Bates–Schwarzenbach method using UV–Vis Perkin–Elmer Lambda 35 Spectrophotometer at temperature 298.15 K in the buffer solutions. Our experimental pK_a values for nadolol, bifonazole, nimesulide, and mefenamic acid are 9.3, 5.85, 7.34, and 3.88, respectively. The basic thermal properties of pure drugs i.e. fusion and glass-transition temperatures, as well as the enthalpy of fusion and the molar heat capacity at the glass-transition (at constant pressure) have been measured using the differential scanning microcalorimetry technique (DSC). Molar volumes have been calculated with the Barton group contribution method. The experimental solubility results have been correlated by means of three commonly known G^E equations: the Wilson, NRTL, and UNIQUAC with the assumption that the systems studied here are simple eutectic mixtures. The activity coefficients of pharmaceuticals in saturated solutions in each correlated binary mixture were calculated from the experimental results. Prediction of solubility in water at T = 298.15 K was made by the group contribution method.