Static Extraction Cycles Research Articles

Development of extraction methodology for identification of extractive-compounds indexing natural durability of selected wood species

ABSTRACT This study is concerned with establishing a uniform experimental protocol for the determination of phenolic extractives, which play an essential role in the durability of the wood of selected species included in the field tests. European larch (Larix decidua), Norway spruce (Picea abies), Scots pine (Pinus sylvestris), European oak (Quercus sp.), sweet chestnut (Castanea sativa), and black locust (Robinia pseudoacacia) were included in the study. Extraction yield data were collected for extraction in a Soxhlet apparatus using common polar extraction solvents (ethanol, acetone, methanol, water) and for single static extraction cycles in accelerated solvent extraction (ASE). The suitability of the solvents and the appropriate extraction conditions were evaluated based on the results of gravimetric analysis of hydrophilic extractives, spectrophotometric analysis of total phenols, and chromatographic analysis using high-performance liquid chromatography. Extraction in the ASE system with methanol proved to be a quick and accurate way to prepare samples for chemical analysis of extractives of selected wood species. With the chemical monitoring of targeted phenolic extractives in wood subjected to leaching, we propose a novel protocol suitable also for for measuring the effects of weathering on the natural durability of wood in future studies.

Simultaneous extraction and purification of fucoxanthin from Tisochrysis lutea microalgae using compressed fluids

The marine microalga Tisochrysis lutea, a Haptophyta with a thin cell wall and currently used mainly in aquaculture is a potential source of several bioactive compounds of interest such as carotenoids. In the present study, the simultaneous extraction and purification of fucoxanthin, the main carotenoid from T. lutea, was optimized using pressurized fluid extraction followed by in-cell purification. An experimental design was employed to maximize carotenoids' extraction; the experimental factors chosen were: (i) percentage of ethanol/ethyl acetate (0-100 %), (ii) temperature (40-150°C), and (iii) number of static extraction cycles (1-3). The maximum carotenoids' recovery, mainly fucoxanthin, was obtained with pure ethyl acetate at 40°C using one extraction cycle, achieving values of 132.8mg of carotenoids per gram of extract. Once the optimum extraction conditions were confirmed, in-cell purification strategies using different adsorbents were developed to obtain fucoxanthin-enriched extracts. Activated charcoal showed potential retention of chlorophylls allowing an effective purification of fucoxanthin in the obtained extracts. Chemical characterization of extracts was carried out by reversed-phase high-performance liquid chromatography with diode array detection. Therefore, a selective fractionation of high value compounds was achieved using the proposed green downstream platform based on the use of compressed fluids.

Simultaneous high‐performance liquid chromatography with diode array detection and time‐of‐flight mass spectrometric confirmation of the ten bioactive compounds in Semen Sojae Preparatum

Semen Sojae Preparatum is one of the most widely used traditional Chinese medicines. A reliable and accurate high-performance liquid chromatography with diode array detection method has been developed and validated for the quantitative determination of the ten bioactive compounds contained in Semen Sojae Preparatum. The samples were first extracted by pressurized liquid extraction using 80% ethanol at 100°C for 15min and three static extraction cycles. Chromatographic separation was conducted on a C18 column using a mobile phase consisting of water and acetonitrile under gradient elution, and the detection wavelength was set at 210nm. The samples were further analyzed on a high-performance liquid chromatography with time-of-flight mass spectrometry system to confirm the determination results. All the ten analytes were well separated, and the calibration curves showed good linearity. The intra- and interday precisions were evaluated in terms of relative standard deviation values within the ranges of 0.20-1.43% and 0.40-4.78%, respectively. The recoveries for the ten analytes were all in the ranges of 96.2-104.3%, with relative standard deviation values <3.85%. The established high-performance liquid chromatography method could serve as a reliable and accurate method for the quality evaluation of Semen Sojae Preparatum from different origins.

Determining the distribution of triclosan and methyl triclosan in estuarine settings

We have developed a method for the analysis of two sewage-derived contaminants: triclosan (TCS), an antibacterial agent, and methyl triclosan (MTCS), a TCS metabolite. For solid samples (4g), extraction and cleanup were integrated into the same step using pressurized liquid extraction (PLE) with in-cell-clean-up (1g of florisil). The extraction was performed using dichloromethane at 100°C, 1500 psi and 3 static extraction cycles of 5min each. For water samples (100mL), stir bar sorptive extraction–liquid desorption (SBSE–LD) was used. Bars were stirred for 10h and analytes were later desorbed using acetonitrile. Finally, MTCS and a silylated derivative of TCS were determined by gas chromatography–mass spectrometry (GC–MS). Recovery experiments in water and sediments were performed and the results ranged from 67% to 78%. Limits of detection (LODs) were 5ngL−1 for TCS and 1ngL−1 for MTCS, in water samples, and 0.1ngg−1 for TCS and MTCS in solid samples. The method was applied then to determine the levels of these compounds in the estuary of Guadalete River (SW Spain). TCS and MTCS concentrations up to 9.6ngg−1 in sediments and 310ngL−1 in water were measured. Their distribution was strongly influenced by the presence of wastewater sources, treated and untreated, along the sampling area, where maximum concentrations were detected. Highest values were reached in the water column during low tides as the water volume in the estuary becomes lower.

Simultaneous Determination of Five Bioactive Components in Radix Glycyrrhizae by Pressurised Liquid Extraction Combined with UPLC–PDA and UPLC/ESI–QTOF–MS Confirmation

Glycyrrhizae species are popular ingredients of herbal medicine in most traditional Chinese medicine prescriptions, and they mainly contain flavonoids and triterpene saponins. The contents of these bioactive compounds may vary in different batches and affect the therapeutic effects. Thus comprehensive quality control and monitoring of their herbal formulation are of paramount concern. To establish a rapid, effective pressurised liquid extraction (PLE) and ultra-performance liquid chromatography coupled with photodiode array (UPLC-PDA) method to evaluate the quality of Glycyrrhizae species. Radix Glycyrrhizae was extracted by PLE using 70% ethanol at 100°C for 15 min during three static extraction cycles. Separation was performed using an UPLC system to quantify five bioactive compounds, namely liquiritin apioside, liquiritin, liquiritigenin, glycyrrhizic acid and glycyrrhetinic acid, in 12 batches of samples of different origins in China. Furthermore, the samples were analysed using an ultra-performance liquid chromatography coupled with electrospray ionisation and time-of-flight mass spectrometry (UPLC/ESI-QTOF-MS) system to confirm the results. The calibration curves of all five analytes showed good linearity (R(2) > 0.9997). Accuracy, precision and repeatability were all within required limits. The mean recoveries measured at the three concentrations were higher than 93.7% with RSDs lower than < 3.33% for the targets. The established PLE and UPLC-PDA method could serve as a rapid and effective method for quality evaluation of Radix Glycyrrhizae. The UPLC technique can be considered as an attractive alternative to HPLC in routine quality control of Chinese medicine, especially in situations where high sample throughput and fast analytical speed are required.

Rapid qualitative and semi-quantitative determination of polymer additives in polymer matrix by electrospray ionization-triple quadrupole mass spectrometry with accelerated solvent extraction (ASE–ESI-MS/MS)

A rapid method for the qualitative and semi-quantitative determination of polymer additives was developed to determine a set of eight polymer additives used in plastic samples by accelerated solvent extraction–electrospray ionization-triple quadrupole mass spectrometry (ASE–ESI-MS/MS). The eight additives were Tinuvin 328, Tinuvin 770, Cyasorb 2908, Cyasorb 3853, Irgafos 168, Antioxidant 405, Irganox 565, Irganox MD 1024. In order to enable the fast identification of additives, an ESI-MS library for 100 additives was built. By using a molecular weight search of the library, and comparing the MS/MS spectra, additives in polymers can be easily identified. Moreover the additives can be quantified by ESI-MS/MS without a column separation step. ASE was used for sample preparation. Three static extraction cycles were carried out for 20 min per cycle at 1500 psi and 100 °C, using trichloromethane/acetone (1/1, v/v) as the extraction solvent, then the samples were washed with a 20% volume of the maximum bottle (66 mL) of extraction solvent. Finally the samples were purged with nitrogen for 100 s and re-dissolved in 1 mL methanol, diluted 100 times and 5 μL directly injected into the instrument for analysis. Limits of detection for the multi-reaction-monitoring mode of the ESI-MS/MS analysis varied from 0.1 to 10 ng mL−1. The calibration curves were linear with R ≥ 0.993. The relative recoveries were between 84.0% and 120% with relative standard deviations (RSD, n = 6) lower than 20%. This quantification method was successfully used in the determination of additives in real samples. The method was confirmed by UPLC–MS/MS and the results were in excellent accordance.

Environmentally friendly analysis of emerging contaminants by pressurized hot water extraction–stir bar sorptive extraction–derivatization and gas chromatography–mass spectrometry

This work describes the development, optimization, and validation of a new method for the simultaneous determination of a wide range of pharmaceuticals (beta-blockers, lipid regulators…) and personal care products (fragrances, UV filters, phthalates…) in both aqueous and solid environmental matrices. Target compounds were extracted from sediments using pressurized hot water extraction followed by stir bar sorptive extraction. The first stage was performed at 1,500 psi during three static extraction cycles of 5 min each after optimizing the extraction temperature (50-150 °C) and addition of organic modifiers (% methanol) to water, the extraction solvent. Next, aqueous extracts and water samples were processed using polydimethylsiloxane bars. Several parameters were optimized for this technique, including extraction and desorption time, ionic strength, presence of organic modifiers, and pH. Finally, analytes were extracted from the bars by ultrasonic irradiation using a reduced amount of solvent (0.2 mL) prior to derivatization and gas chromatography-mass spectrometry analysis. The optimized protocol uses minimal amounts of organic solvents (<10 mL/sample) and time (≈8 h/sample) compared to previous existing methodologies. Low standard deviation (usually below 10%) and limits of detection (sub-ppb) vouch for the applicability of the methodology for the analysis of target compounds at trace levels. Once developed, the method was applied to determine concentrations of these compounds in several types of sample (wastewater, seawater, pore water, and sediment) from Cadiz Bay (SW Spain). To our knowledge, these findings represent the first information available on the presence of some of the target compounds in the marine environment.

Pressurized solvent extraction followed by gas chromatography tandem mass spectrometry for the determination of benzotriazole light stabilizers in indoor dust

A novel and sensitive method for the determination of five benzotriazole compounds (commonly used as light stabilizers) in indoor dust is presented. Pressurized liquid extraction (PLE) and gas chromatography followed by tandem in time mass spectrometry (GC–MS/MS) were used as sample preparation and determination techniques, respectively. Extraction and clean-up were integrated on-line and, after an evaporative concentration step, the extract provided by the PLE instrument was injected directly in the GC–MS/MS system. Parameters affecting the performance of the sample preparation process were evaluated using experimental factorial designs. Under optimized conditions, analytes were recovered from 0.5 g samples in 3 static extraction cycles of 10 min, using a hexane:dichloromethane (7:3) mixture, at 90 °C. Silica (1 g) was placed in the bottom of the extraction cells as clean-up sorbent. The recoveries of the method varied from 82 to 122%, with standard deviations below 13. The inter-day precision ranged from 9 to 12%, and the limits of quantification (LOQs) remained below 10 ng g −1 for all species. For the first time, four of the five investigated species were found in dust from indoor environments. Their mean concentrations ranged from 71 to 780 ng g −1.

Pressurized liquid extraction versus other extraction techniques in micropreparative isolation of pharmacologically active isoflavones from Trifolium L. species

As a new sample preparation technique, pressurized liquid extraction (PLE), in combination with reversed-phase liquid chromatography (RP-LC) and photodiode-array (PDA) detection were used for the isolation and determination of phytoestrogenic isoflavones in hydrolyzed extracts obtained from aerial parts of five Trifolium L. (clover) species. To optimize the effectiveness of PLE procedure, variable extraction parameters: methanol and acetone (or their 75% aqueous solutions), as extraction solvents, temperatures (75, 100 and 125 °C) and the changeable number of static extraction cycles were tested. Additionally, two other micropreparative techniques: ultrasound-assisted extraction (UAE), and conventional solvent extraction (CSE), under optimized conditions, were also used and compared. Optimum extraction efficiency, expressed in the highest yield of biochanin A, formononetin, daidzein and genistein from plant material, with PLE, using methanol–water (75:25, v/v) as an extraction solvent, an oven temperature of 125 °C and three 5-min static extraction cycles, was obtained.

Pressurized liquid extraction with in-cell clean-up followed by gas chromatography–tandem mass spectrometry for the selective determination of parabens and triclosan in indoor dust

A sample preparation method based on the use of pressurized liquid extraction is proposed for the determination of four alkyl parabens and triclosan in indoor dust. Extraction of analytes and removal of interfering species were achieved in the same step, by placing an appropriate sorbent in the extraction cell and by choosing a right combination of washing and elution solvents. Compounds, as silylated derivatives, were determined by gas chromatography in combination with tandem mass spectrometry (GC–MS/MS). Factors affecting the yield and selectivity of the sample preparation procedure were carefully evaluated. Under final conditions, dried samples (0.5 g of dust and 1 g of sodium sulphate) were dispersed with 3 g of Florisil and loaded into an 11 mL stainless-steel extraction cell containing 1 g of the same material as clean-up sorbent. Non-polar species were removed with n-hexane under mild conditions (40 °C, 3.4 MPa) and then analytes were extracted with ethyl acetate. The best compromise extraction conditions were 103 °C, 13.8 MPa and 3 static extraction cycles of 1 min. The proposed method provided recoveries from 76 to 98%, relative standard deviations under 11% (operating under reproducibility conditions) and quantification limits from 1 to 4 ng/g. The analysis of dust samples from private houses and office buildings confirmed the ubiquitous presence of target bactericides in these environments.

Pressurized liquid extraction of isoflavones from soybeans

Isoflavone derivatives from freeze-dried soybeans were extracted by pressurized liquid extraction (PLE) and determined by reverse-phase high performance liquid chromatography (HPLC) with both photo diode array and mass spectrometry (MS) detection. Both real and spiked samples were used in the development of the method. Several extraction solvents (methanol (MeOH) and ethanol (EtOH), 30–80% in water and water), temperatures (60–200 °C), pressures (100–200 atm), as well as the sample size (0.5–0.05 g) and cycle length (5–10 min) were studied for the optimization of the extraction protocol. The optimized extraction conditions for quantitative recoveries were: 0.1 g of sample, 100 °C, three (7 min) static extraction cycles and ethanol 70% as extracting solvent. The stability of the isoflavones during the PLE was also determined. Under PLE conditions, degradation of malonyl glucoside forms of the isoflavones takes place using temperatures higher than 100 °C whereas degradation of glucosides takes place above 150 °C. Using the optimized protocol, isoflavones can be extracted from freeze-dried soybeans without degradation.

Static pressurised liquid extraction of nitrated polycyclic aromatic hydrocarbons from soils with on-line filtration-preconcentration prior to gas chromatography-mass spectrometry detection.

Nitrated polycyclic aromatic hydrocarbons have been extracted from both spiked and natural contaminated soils by using static pressurised liquid extraction. The variables governing the extraction (namely, pressure, extraction time, temperature and number of static extraction cycles) have been optimised using the experimental design methodology. A laboratory-made pressurised liquid extractor has been used allowing its coupling to a filtration-preconcentration system through a flow injection interface, thus providing a partially automated approach. Gas chromatography with MS-MS ion preparation mode has been used for individual separation-identification/quantification providing both high selectivity (no interferences were observed) and sensitivity (detection limits of low pg). The comparison of the proposed approach with the reference EPA Method 3540 has shown that both methods provide similar efficiencies but with dramatic saving of time by the former (30 min vs. 24 h). The use of water as leaching agent avoids the use of organic solvents, thus providing an environmentally friendly method.

Static extraction with modified pressurized liquid and on-line fluorescence monitoring. Independent matrix approach for the removal of polycyclic aromatic hydrocarbons from environmental solid samples.

The coupling of a static pressurized liquid extractor to a flow injection manifold has allowed real-time on-line fluorescence monitoring of the polycyclic aromatic hydrocarbons (PAHs) extracted from environmental solid samples, which can be used for either screening or semiquantitative purposes. Sodium dodecyl sulfate (SDS) was added to the water for favoring the extraction of the low-polar analytes. Different solid samples such as sandy soil, river sediments, trout and sardine spiked with the target PAHs were subjected to several 15-min static extraction cycles with SDS-water, at 200 degrees C. The results obtained demonstrated that fluorometric monitoring of static pressurized liquid extraction constitutes an approach as efficient as conventional Soxhlet for the extraction of PAHs from solid samples but with the following positive features: (a) drastic reduction of the extraction time as the extraction kinetics can be monitored and thus the end of the leaching step determined independently of the sample matrix; (b) use of water as extractant thus given place to an environmentally friendly method; and (c) coupling of static extraction to subsequent dynamic steps. The method has been applied to a certified reference material (CRM 524, BCR, industrial soil/organics) for quality assurance/validation. The total content of each analyte was determined by HPLC-fluorimetric detection.