Ultrasound assisted extraction of phenolic compounds from grapes

A new ultrasound-assisted extraction method was developed for the determination of phenolic compounds present in grapes. Several extraction variables including extraction temperature (0–75 °C), output amplitude (20, 50 and 100%), duty cycle (0.2 s, 0.6 s and 1 s), the quantity of sample (0.5–2 g), and the total extraction time (3–15 min) were evaluated. One of the most widely used extraction methods of polyphenol extraction has been used as reference method. Three parameters were compared: total amount of phenolic compounds, total amount of anthocyanins and total amount of tannic components. The resulting method produced similar or higher recoveries for these three parameters; however a much shorter extraction time was needed: 6 min (ultrasound assisted extraction method) instead of 60 min (reference method).     

Ultrasound-assisted solvent extraction of total polycyclic aromatic hydrocarbons from mussels followed by spectrofluorimetric determination

An ultrasound-assisted solvent extraction procedure has been optimised to speed up total polycyclic aromatic hydrocarbons (T-PAHs) extraction from mussel soft tissue. The T-PAHs releases have been evaluated by spectrofluorimetry (excitation and fluorescence emission wavelengths of 300 and 382 nm, respectively, and using chrysene as calibrant). Variables such as sonication time, ultrasound frequency, n-hexane volume, dichloromethane volume, number of repeated extractions with n-hexane and number of repeated extraction with dichloromethane were simultaneously studied by applying a Plackett-Burman design (PBD) approach. Results showed that ultrasound frequency and n-hexane and dichloromethane volumes were statistically significant variables (confidence interval of 95%). These last two variables were finally optimised by using central composite designs (CCD), yielding optimum n-hexane and dichloromethane volumes of 2.5 and 6.5 ml, respectively. The lowest T-PAHs releasing at high ultrasound frequency (35 kHz) led to choice the lowest ultrasound frequency (17 kHz) to perform the extraction. Variables such as sonication time and number of repeated extraction with n-hexane or dichloromethane were statistically non-significant and they were fixed at 10 min and the extraction with n-hexane and dichloromethane were performed once. The limit of detection was 0.021 μg g⁻¹ (referred to dried mass), the repeatability of the overall method was 4.7% (n = 9) and the analytical recoveries were between 98 and 105%. The proposed method was finally applied to 16 mussel samples (Mytilus galloprovincialis) from Ría de Arousa estuary (Galicia, northwest Spain).     

Arsenic extraction in marine biological materials using pressurised liquid extraction

A pressurised liquid extraction (PLE) procedure, by using methanol/water mixture, was developed for extracting arsenical species from marine biological material (mussel and fish) and standard reference materials (CRMs). A Plackett-Burman 2⁸ × 3/64 designs (PBD) was used as a multivariate strategy for the evaluation of the effects of several variables (MeOH/H₂O solvent mixture, temperature, static time, extraction steps, pressure, mean particle size and diatomaceous earth (DE) mass/sample mass ratio) on the extracting procedure. Electrothermal atomic absorption spectrometry (ETAAS) was used to determine the total As concentration on the methanolic extracts. The accuracy of the optimised extraction procedure was verified by analysing several CRMs (GBW-08751, BCR-278R and DORM-2). The precision obtained (between 4.5 and 6.2%) was adequate. The extracted arsenic species (mainly arsenobetaine (AsB)) were analysed by high performance liquid chromatography coupled to ultraviolet cracking and hydride generation-atomic fluorescence spectrometry (HPLC-UV-HG-AFS). The analytical performances obtained were adequate for the arsenic speciation in marine biological samples; LOD between 10 and 35 ng g⁻¹. The accuracy was verified for AsB using DORM-2. Finally, the proposed method (PLE followed by HPLC-UV-HG-AFS) was applied to mussel and fish samples.     

Pressurized liquid extraction-assisted mussel cytosol preparation for the determination of metals bound to metallothionein-like proteins

The possibilities of pressurized liquid extraction (PLE) have been novelty tested to assist the cytosol preparation from wet mussel soft tissue before the determination of metals bound to metallothionein-like proteins (MLPs). Results obtained after PLE were compared with those obtained after a classical blending procedure for mussel cytosolic preparation. Isoforms MLP-1 (retention time of 4.1 min) and MLP-2 (retention time of 7.4 min) were separated by anion exchange high-performance liquid chromatography (HPLC) and the concentrations of Ba, Cu, Mn, Sr and Zn bound to MLP isoforms were directly measured by inductively coupled plasma-atomic emission spectrometry (ICP-OES) as a multi-element detector. The optimized PLE-assisted mussel cytosol preparation has consisted of one extraction cycle at room temperature and 1500 psi for 2 min. Since separation between the solid mussel residue and the extract (cytosol) is performed by the PLE system, the cytosol preparation method is faster than conventional cytosol preparation methods by cutting/blending using Ultraturrax or Stomacher devices.     

Pressurized liquid extraction as a novel sample pre-treatment for trace element leaching from biological material

Pressurized liquid extraction (PLE), commonly used for organic compounds extraction, has been applied for trace element leaching from marine biological material in order to determine major and trace elements (Al, As, Cd, Co, Cu, Fe, Hg, Li, Mn, Pb, Se, Sr, V and Zn). The released elements by formic acid PLE have been evaluated by inductively coupled plasma-optical emission spectrometry (ICP-OES). Different variables, such as formic acid concentration, extraction temperature, static time, extraction steps, pressure, mean particle size and diatomaceous earth (DE) mass/sample mass ratio were simultaneously studied by applying an experimental design approach (Plackett-Burman design (PBD) and central composite design (CCD)). Results showed that the extraction temperature was statistically significant (confidence interval of 95%) for most of the elements (high metal releasing was achieved at high temperatures). In addition, formic acid concentration was also statistically significant (confidence interval of 95%) for metals such as Cd and Cu. Most of the metals can be extracted using the same PLE operating conditions (formic acid concentration of 1.0 M, extraction temperature at 125 °C, static time of 5 min, one extraction step, extraction pressure at 500 psi and DE mass/sample mass ratio of 2). Taking in mind PLE requirements at the optimised operating conditions (125 °C), a time of 6 min is needed to pre-heat the cell. Therefore, the PLE assisted multi-element leaching is completed after 12 min. Analytical performances, such as limits of detection and quantification, repeatability of the over-all procedure and accuracy, by analysing GBW-08571, DORM-2, DOLT-3 and TORT-2 certified reference materials, were finally assessed.     

Development of an ultrasound-assisted extraction method for biomonitoring of vanadium and nickel in the coastal environment under the influence of the Prestige fuel spill (North east Atlantic Ocean)

As a consequence of the Prestige shipwreck occurred in the Northeast Atlantic Ocean in November 2002, the need for establishing the environmental impact caused by metals has been of primary concern. Among the different metals contained in the fuel spill, V and Ni are particularly of interest since they appear at relatively high concentration in the original fuel. Biomonitoring of V and Ni using wild mussels (Mytilus edulis) collected along the Galician Coast (NW Iberian Peninsula) has been performed. Ultrasound-assisted extraction of V and Ni from dried mussel tissues using probe sonication allowed a fast solid-liquid extraction thus facilitating sample preparation from large sample batches used for biomonitoring. V and Ni were determined in shellfish caught in the Galician littoral and tar balls from the Prestige spill by electrothermal-atomic absorption spectrometry and inductively coupled plasma-optical emission spectrometry, respectively. A Plackett-Burman saturated design was applied for screening optimization of variables influencing the ultrasound-assisted extraction of V and Ni from shellfish. Efficient extraction of both metals was obtained from slurries prepared in 2 mL capacity sample vials (10 mg sample with a particle size less than 100 μm) using a 3% (v/v) HNO₃ diluent and subjected to probe sonication (3 min; 30% vibrational amplitude of the probe). The method was successfully validated by means of three certified reference materials: NRCC-TORT-2 Lobster hepatopancreas, NIST-SRM 1566b Oyster tissue and NIST-SRM 2977 Mussel tissue. The detection limit (LOD) of V and Ni in the marine biological tissues, calculated according to the 3σ criterion, were 0.24 μg g⁻¹ and 0.15 μg g⁻¹ for V and Ni, respectively. V and Ni concentrations in M. edulis were in the range 1.7-4.8 and 0.8-2.8 μg g⁻¹, respectively. Whilst no significant variations in Ni contents were observed in regard to reference values, an important increase in V concentration is observed at some sampling points, thereby indicating bioaccumulation.     

Chromium available fractions in arousa sediments using a modified microwave BCR protocol based on microwave assisted extraction

In a research of chromium availability, the three-stage sequential extraction procedure, proposed by European Community Bureau of Reference (BCR), has been applied for the metal fractionation in marine sediment samples. The procedure has been modified, evaluating the effect of microwave energy to perform the sequential method. Results achieved a substantial reduction in time in comparison to the traditional shaking technique. The time of the first and the second extractions were reduced to 30 s in both steps using microwave heating and working at 66 W of power. To the third extraction, higher power was necessary so it was chosen to work at 198 W. In the last step investigated, time was reduced to 1 min, being a great improvement respect to the conventional BCR sequential extraction protocol.Chromium determinations in these extracts were carried out by Electrothermal Atomic Absorption Spectrometry (ETAAS). The developed method was applied for chromium determination in marine sediment samples from Ria de Arousa (Galicia, NW of Spain). The values obtained by our laboratory ranged from 0.10 to 1.02 μg g⁻¹ for soluble and reducible fractions, and from 5.5 to 60.0 μg g⁻¹ for the oxidisable fraction. The higher concentrations obtained were the chromium associated with the organic fraction of the marine sediments.     

Microwave assisted extraction of soy isoflavones

A fast and reliable analytical method using microwave assisted extraction has been developed. Several extraction solvents (methanol (MeOH) and ethanol (EtOH), 30-70% in water and water), temperatures (50-150 °C), extraction solvent volume, as well as the sample size (1.0-0.1 g) and extraction time (5-30 min) were studied for the optimization of the extraction protocol. The optimized extraction conditions for quantitative recoveries were: 0.5 g of sample, 50 °C, 20 min and 50% ethanol as extracting solvent. No degradation of the isoflavones was observed using the developed extraction protocol and a high reproducibility was achieved (>95%).     

Assessment of ultrasound-assisted extraction as sample pre-treatment for the measurement of lead isotope ratios in marine biological tissues by multicollector inductively coupled plasma-mass spectrometry

In this work, ultrasound-assisted extraction (UAE) was evaluated as a sample preparation procedure for lead isotope ratio measurements in marine biological tissues by multicollector inductively coupled plasma-mass spectrometry. 20 mg of marine biological tissue and 1 mL of acid extractant were sonicated for 3 min at 60% ultrasound amplitude. Matrix separation was performed in the supernatant using a chromatographic exchange resin (Sr-Spec™). Total elimination of organic matter was achieved during the separation step. Microwave-assisted digestion and dry-ashing were used for comparative purposes. No significant differences were found in lead isotope ratios at 95% of confidence level. UAE emerges as an advantageous alternative to classical methods for sample preparation owing to its simplicity and rapidity (i.e. operation steps were reduced), low reagent consumption and low contamination risks.     

Determination of Cd and Pb in biological reference materials by electrothermal atomic absorption spectrometry: A comparison of three ultrasonic-based sample treatment procedures

Three different ultrasonic-based sample treatment approaches, the automated ultrasonic slurry sampling, the ultrasonic assisted acid solid-liquid extraction (ASLE) and the enzymatic probe sonication (EPS) were compared and discussed for the determination of Cd and Pb by ET-AAS in biological reference materials. The sample mass chosen to perform the analysis was 10 mg and the liquid volume was 1 ml of nitric acid 1 M. The best results were obtained with the slurry procedure with which it was possible accurate and precise determination of the Cd and Pb content in four of the five reference materials studied. Optimum performance (total metal extraction) of ASLE assisted by ultrasound for Cd was only achieved in two of the four materials assessed whereas total Pb recovery was only possible in three of the five samples. Total extraction with the enzymatic probe sonication was only obtained for Cd in oyster tissue. Neither ASLE nor EPS were able to extract Cd or Pb from spruce needles. Pb concentration obtained after EPS was found to be highly dependent from sample centrifugation speed and time.     

Optimisation of focused ultrasound extraction (FUSE) and microwave-assisted extraction (MAE) of hydrocarbons in geological chert samples

The analysis of hydrocarbons in chert rocks provides a worthwhile source of information regarding the geochemical features of a depositional setting. Since the typical analytical procedure requires long Soxhlet extractions and the use of large quantities of sample (30-50 g), in this work we have optimised the focused ultrasound extraction (FUSE) and the microwave-assisted extraction (MAE) to make available a less severe procedure. In both cases a full experimental design including solvent mixture composition (Dichloromethane/Hexane/Acetone) and process variables (sonication time and cycles, and extraction temperature and time) by means of D-optimal designs. In the extracted fractions hydrocarbons (C₁₆-C₄₀) were analysed by gas-chromatography-mass spectrometry. In the case of FUSE the process variables were the most sensitive variables and the optimum conditions were defined at 60:40 DCM/Hex mixture and a sonication time of 30 min and 9 cycles. In the case of MAE all the variables shown a significant effect on the extraction yield and the most adequate conditions (60:30:10 DCM/Hex/Ace mixture and an irradiation time of 15 min at 110 °C) were established from the analysis of the response surface. Both methods were systematically applied with different chert samples collected in Cucho (Trebiño County, Burgos, Spain) and we were able to assure quantitative extractions (>85%) in the first extraction. Additionally, from the distribution patterns of n-alkanes obtained in the different chert samples (nodular chert, laminar chert and massive-brechoid chert) collected in Cucho, we were able to distinguish different origins and diagenetic history.     

Development of stir-bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry for the analysis of musks in vegetables and amended soils

The aim of this study was to develop a sensitive and environment-friendly method based on stir-bar sorptive extraction (SBSE) followed by thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS) to determine 8 synthetic musks (musk ambrette, musk ketone, celestolide, tonalide, galaxolide, phantolide, traseolide, and cashmeran) in vegetables (lettuce, carrot, and pepper) and amended soil samples. In a first step sorptive extraction was studied both in the headspace (HSSE) and in the immerse mode (SBSE). The best results were obtained in the immersion mode which was further studied. The influence of the main factors: methanol (20%) and NaCl addition (0%), extraction temperature (40 °C) and time (180 min), extraction solvent volume (9 mL) and stirring rate (600 rpm) on the efficiency of SBSE was evaluated by means of experimental designs. In the case of TD, desorption time (10 min), desorption temperature (300 °C), cryo-focusing temperature (−30 °C), vent flow (75 mL/min) and vent pressure (7.2 psi) were studied using both a fractioned factorial design and a central composite design (CCD). The method was validated in terms of apparent recoveries (AR%), method detection limits (MDLs) and precision at two different concentration levels. Although quantification using instrumental calibration rendered odd results in most of the cases, satisfactory recoveries (74–126%) were obtained in the case of matrix-matched calibration approach for all of the analytes and matrices studied at the two concentration levels evaluated. MDLs in the range of 0.01–0.8 ng/g and 0.01–1.1 ng/g were obtained for vegetables and amended soil samples, respectively. RSD values within 1–23% were obtained for all the analytes and matrices. Finally, the method was applied to the determination of musks in vegetable and amended soil samples.     

Tin determination in marine sediment, soil, coal fly ash and coal slurried samples by hydride generation-electrothermal atomic absorption spectrometry

Different procedures of tin hydride generation from aqueous and acidified slurries of marine sediment, soil, coal fly ash and coal samples, coupled to electrothermal atomic absorption spectrometry were optimised by using factorial designs. A batch mode generation system and Ir-treated graphite tubes were used for the hydride generation and atomisation, respectively. Eight variables, affecting the hydride generation and hydride transport efficiency (hydrochloric acid and sodium tetrahydroborate concentrations, particle size, acid volume and argon flow rate), the hydride trapping efficiency (trapping temperature and trapping time) and the atomisation efficiency (atomisation temperature) were studied and optimised. In addition, acid pre-treatment procedures assisted by ultrasonic energy were used for soil and coal matrices, to obtain acidified slurries and acid leachates. The involved variables were hydrochloric and nitric acid concentrations, exposure time to ultrasound, particle size and leaching solution volume. Adequate accuracy (41.5±0.8 and 1.4±0.2 mg kg⁻¹, for PACS-1 (sediment marine) and NIST-1633b (coal fly ash), respectively) were obtained by using aqueous slurry reference materials. In addition, values of 6.2±0.6 and 1.2±0.1 mg kg⁻¹ were assessed by analysing GBW-07401 (soil) and NIST-1632c (coal) certified reference materials.     

Analysis of sediment-associated insecticides using ultrasound assisted microwave extraction and gas chromatography-mass spectrometry

An ultrasound assisted microwave extraction (UAME) method was developed to simultaneously extract five organophosphate (OP) and eight pyrethroid insecticides from sediment. The optimized UAME conditions were to use 100 ml of a mixture of hexane and acetone (1:1, v/v) solution as the extraction solvents, and extraction time, microwave and ultrasonic power settings of 6 min, 100 W and 50 W, respectively. Extracts were cleaned using solid phase extraction and analyzed by gas chromatography-mass spectrometry in negative chemical ionization mode and quantification was based on matrix-matched standard solutions along with internal standard calibration. At the spiked concentrations of 1, 5 and 20 ng/g dry weight (dw), recoveries of OPs were 77.6-122%, 65.2-128% and 75.6-141% with relative standard deviations (RSDs) of 10.6-18.1%, 3.1-12.5% and 8.0-35.3%, respectively, while recoveries of pyrethroids were 78.0-101%, 76.4-104% and 71.0-99.5% with RSDs of 10.3-23.5%, 4.7-17.6% and 8.8-18.7%, respectively. Method detection limits ranged from 0.31 to 0.45 ng/g dw for the OP insecticides and from 0.27 to 0.70 ng/g dw for the pyrethroid insecticides. The newly developed UAME method was validated by comparing it to Soxhlet and sonication extraction methods. Better recoveries were achieved for most OPs by the novel UAME method, whereas there was no significant difference in recoveries for most of the pyrethroids. Finally, the UAME method was used to quantify the target insecticides in field-contaminated sediment samples which were collected in Guangzhou, China.     

Molecularly imprinted polymer for selective extraction of domoic acid from seafood coupled with high-performance liquid chromatographic determination

In this work, a highly selective sample cleanup procedure that combining molecular imprinting technique (MIT) and solid phase extraction (SPE) was developed for the isolation of domoic acid (a fascinating marine toxin) from seafood samples. The molecular imprinting polymer (MIP) for domoic acid was prepared using 1,3,5-pentanetricarboxylic acid as the template molecule instead of domoic acid. 4-Vinyl pyridine was used as the functional monomer and ethylene glycol dimethacrylate was used as the cross-linking monomer. The obtained imprinted polymer showed high affinity to domoic acid and was used as selective sorbent for the SPE of domoic acid from seafood samples. An off-line molecularly imprinted solid phase extraction (MISPE) method followed by high-performance liquid chromatography (HPLC) with diode-array detection for the detection of domoic acid was also established. Good linearity was obtained from 0.5 mg L⁻¹ to 25 mg L⁻¹ (R² > 0.99) with a quantitation limit of 0.1 mg L⁻¹, which was sufficient to determine domoic acid at the maximum level permitted by several authorities. The mean recoveries of domoic acid from mussel extracts were 93.4-96.7%. It was demonstrated that the proposed MISPE-HPLC method could be applied to direct determination of domoic acid from seafood samples.     

Optimisation of microwave-assisted extraction for the determination of nonylphenols and phthalate esters in sediment samples and comparison with pressurised solvent extraction

Microwave-assisted extraction (MAE) of nonylphenols (NP), nonylphenol mono- and diethoxylates (NP1EO and NP2EO, respectively) and phthalate esters was optimised using an experimental design approach. A D-optimal mixture design was used to optimise the pressure inside the extraction vessel (110-207 kPa), the extraction time (5-25 min) and the extraction solvent (methanol, acetone or n-hexane) or the solvent mixture for the microwave-assisted extraction. Percentage of microwave power (80%) and solvent volume (15 ml) were fixed in all the experiments. As a consequence, the optimum extraction of these compounds was carried out at an intermediate pressure (159 kPa) with pure methanol and during 15 min. Moreover, solid phase extraction was also optimised for the clean-up of the extracts and C-18, LiChrolut^® and Oasis^® cartridges were studied in order to obtain the best recoveries of the compounds of interest. The highest recoveries were obtained with LiChrolut^® cartridges after the elution with ethyl acetate. The cleaned extracts were analysed in a gas chromatograph with mass spectrometric detection and in a liquid chromatograph with diode array and fluorescence detection (HPLC-DAD-UV-FLD). The same sediment was also extracted twice in order to check that an exhaustive extraction of the analytes had occurred. Finally, the optimised extraction method was compared with pressurised solvent extraction (PSE), using an estuarine sediment sample.     

Optimization of ultrasound assisted-emulsification-dispersive liquid-liquid microextraction by experimental design methodologies for the determination of sulfur compounds in wines by gas chromatography-mass spectrometry

A new method was developed for analyzing sulfur compounds in the aroma of white wines using ultrasound assisted-emulsification-dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry detection. In the present work, the analytical method for simultaneous determination of seven sulfur compounds (methylmercaptoacetate, methyl(methylthio)acetate, 2-methylthioethanol, 3-methylthiopropanol, 3-methylthiohexanol, 4-methylthio-4-methyl-2-pentanone and hexanethiol) is reported. Parameters that affect the efficiency of the methodology such as extracting and dispersing solvents, sample volume, ion strength, cavitation time and centrifugation time were investigated using a fractionated factorial 2^6-1 (R = V) screening design. Then, the factors presenting significant positive effects on the analytical response (extracting volume, ion strength, cavitation time and centrifugation time) were considered in a further central composite design to optimize the operational conditions for the ultrasound assisted-emulsification-dispersive liquid-liquid microextraction procedure. Additionally, multiple response simultaneous optimization by using the desirability function was used to find the optimum experimental conditions. The best results were obtained using pH sample 4.25, extractant volume 150 μL, ionic strength 8.75% NaCl, cavitation time 20 s and centrifugation time 50 s. The use of the optimized ultrasound assisted-emulsification-dispersive liquid-liquid microextraction technique allowed to obtain the best extraction results with the minimum interference from other substances from the matrix, and it allowed to quantify the analytes in white wine samples by calibration graphs. Recoveries ranging from 91.99% to 125.87% for all sulfur compounds proved the accuracy of the proposed method in white wine samples. Method detection limits were in the range of 0.36-1.67 ng mL⁻¹ and limits of quantitation were between 0.63 and 3.02 ng mL⁻¹ for sulfur compounds in white wine samples. The proposed methodology was successfully applied for the determination concentrations of sulfur compounds in different commercial Chardonnay wine samples from Mendoza, Argentine.     

Speciation of antimony in airborne particulate matter using ultrasound probe fast extraction and analysis by HPLC-HG-AFS

A fast extraction procedure has been developed for Sb(III) and Sb(V) oxoanions speciation in airborne particulate matter samples. Different extraction media (diammonium tartrate, hidroxilammonium clorhidrate, citric acid + ascorbic acid, phosphoric acid and citrate solutions) were tried, with assistance of an ultrasonic probe. The operation power and time of extraction were also optimized. The higher extraction recoveries were obtained with a 100 mmol L⁻¹ hidroxilammonium clorhidrate aqueous solution assisted by the ultrasound probe operated at 50 W during 3 min. The extracts were analyzed by HPLC-HG-AFS. The chromatographic separation of Sb(III) and Sb(V) was also optimized using diammonium tartrate and phthalic acid as mobile phases. The separation of both Sb species was performed in less than 3 min under isocratic conditions, using a 200 mmol L⁻¹ diammonium tartrate solution. The proposed extraction procedure and the HPLC-HG-AFS instrumental coupling have been successfully applied to airborne particulate matter samples, with high Sb content, collected in heavy traffic streets from Buenos Aires (Argentina). The results showed the presence of both Sb species at similar concentrations in the ng m⁻³ level. The extraction yield was higher than 90% for all the analyzed samples.     

On-line determination of manganese in solid seafood samples by flame atomic absorption spectrometry

Manganese is extracted on-line from solid seafood samples by a simple continuous ultrasound-assisted extraction system (CUES). This system is connected to an on-line manifold, which permits the flow-injection flame atomic absorption spectrometric determination of manganese. Optimisation of the continuous leaching procedure is performed by an experimental design. The proposed method allows the determination of manganese with a relative standard deviation of 0.9% for a sample containing 23.4 μg g⁻¹ manganese (dry mass). The detection limit is 0.4 μg g⁻¹ (dry mass) for 30 mg of sample and the sample throughput is ca. 60 samples per hour. Accurate results are obtained by measuring TORT-1 certified reference material. The procedure is finally applied to mussel, tuna, sardine and clams samples.     

Efficient approach for the extraction of proanthocyanidins from Cinnamomum longepaniculatum leaves using ultrasonic irradiation and an evaluation of their inhibition activity on digestive enzymes and antioxidant activity in vitro

Proanthocyanidins were separated for the first time from Cinnamomum longepaniculatum leaves. An experiment‐based extraction strategy was used to research the efficiency of an ultrasound‐assisted method for proanthocyanidins extraction. The Plackett–Burman design results revealed that the ultrasonication time, ultrasonic power and liquid/solid ratio were the most significant parameters among the six variables in the extraction process. Upon further optimization of the Box–Behnken design, the optimal conditions were obtained as follows: extraction temperature, 100°C; ethanol concentration, 70%; pH 5; ultrasonication power, 660 W; ultrasonication time, 44 min; liquid/solid ratio, 20 mL/g. Under the obtained conditions, the extraction yield of the proanthocyanidins using the ultrasonic‐assisted method was 7.88 ± 0.21 mg/g, which is higher than that obtained using traditional methods. The phloroglucinolysis products of the proanthocyanidins, including the terminal units and derivatives from the extension units, were tentatively identified using a liquid chromatography with tandem mass spectrometry analysis. Cinnamomum longepaniculatum proanthocyanidins have promising antioxidant and anti‐nutritional properties. In summary, an ultrasound‐assisted method in combination with a response surface experimental design is an efficient methodology for the sufficient isolation of proanthocyanidins from Cinnamomum longepaniculatum leaves, and this method could be used for the separation of other bioactive compounds.