Continuous Ultrasound-assisted Extraction Research Articles

Experimentation and configuring continuous ultrasound assisted extraction pilot plant operation

Experimentation and configuring continuous ultrasound assisted extraction pilot plant operation

Continuous ultrasound and pulsed ultrasound: Selective extraction tools to obtain enriched antioxidants extracts from cocoa beans (Theobroma cacao L.)

In this study, the effect of continuous assisted extraction (CUAE) and pulsed ultrasound assisted extraction (PUAE) of phenolic compounds from cocoa beans was evaluated. Frequency (25/45 kHz) and extraction time (15/30 min) were varied. Phenolic acids were identified as catechin-(+), epicatechin-(+), procyanidin B1 and procyanidin B2 were quantified on each extract by HPLC-DAD. Then, total phenolic content (TPC), total flavonoids content (TFC), flavan-3-ols, non-flavonoids content (NF) and proanthocyanidins (PAC) were determined. The experimental findings indicated the highest extraction yields of TPC and flavonoids subclasses when prolonged PUAE was used. Additionally, an increase of 282% in epicatechin yield was obtained compared with CUAE. However, the prolonged use of continuous sonication increased the non-flavonoids extraction yield in 23% compared with pulsed sonication. The scavenging and iron chelating activity depended on the chemical composition of each extract and was not correlated directly to TPC.

Aqueous extracts characteristics obtained by ultrasound-assisted extraction from Ascophyllum nodosum seaweeds: effect of operation conditions

Aqueous extracts from Ascophyllum nodosum brown edible seaweeds were obtained after continuous ultrasound-assisted extraction. The effect of sonication time (from 2 to 6 min), sonication amplitude (from 80 to 100%) and solvent-solid ratio (from 20 to 40 g water g−1 dried seaweed) on the extracts features was studied employing a Box-Behnken experimental design. Extracts were characterised by polyphenols, carbohydrate and uronic acid content. Response surface method (by means of a quadratic model) was successfully employed to relate chemical composition of extracts and operation conditions. Optimal experimental conditions were established to obtain maximal polyphenols content and several polyphenols-carbohydrates ratios together with the conditions that minimise energy consumption per extracted polyphenols amount relationship. Antioxidant capacities of extracts were measured employing different methods (DPPH, FRAP and ABTS). Positive linear correlations between antioxidant activity and total polyphenols content were established.

A short time bioactive compounds extraction from Cucurbita pepo seed using continuous ultrasound‐assisted extraction

This study aimed to investigate the effect of acoustic cavitation on phenolic compounds recovery from Cucurbita pepo seed using continuous ultrasound-assisted extraction (CUAE) as a green extraction process. A Box–Behnken response surface design was carried out to investigate and optimize the CUAE independent variables, including concentration of hydroethanolic solvent, biomass to solvent ratio, and sonication time on the total extractable phenols (TEP). The optimized conditions were 70.98% v/v concentration of hydroethanolic solvent, 1:26.49 g/mL ratio of biomass to solvent, and 55.38 min sonication time, under which the predicted TEP was 14.01 mg GAE/g. The determination of DPPH and HO free radical scavenging abilities revealed that the extract had a good ability to scavenge these free radicals and polyphenol concentration was positively correlated with antiradical capacity (AC). The gas chromatography–mass spectrophotometer (GC/MS) analysis revealed that C. pepo seed extract is a potential source of essential fatty acids (39% of total fatty acids). From the results, the phenolic compounds and essential fatty acids from C. pepo seeds could be obtained using the cavitation phenomenon during short time extraction. The AC of product was considerably influenced by the CUAE process mode, while the fatty acid composition was almost constant. The microstructure of cells was investigated using scanning electron microscope (SEM), which confirmed the cell disruption by acoustic cavitation technology.

A short extraction time of vegetable oil from Carica papaya L. seeds using continuous ultrasound acoustic cavitation: Analysis of fatty acid profile and thermal behavior

AbstractThe objective of the present study is to extract the vegetable oil from papaya seeds (Carica papaya L) using Continuous Ultrasound Assisted Extraction (CUAE) method. A face centered–central composite response surface design was applied to explore and optimize the process variables on the oil recovery (%) from papaya seeds. The maximum oil recovery (27.87%) was obtained when CUAE was carried out at 1:13(g/ml) solid–liquid ratio, 80% amplitude level, 48°C temperature and short extraction time of 7 min. Analysis of fatty acid composition revealed that the predominant fatty acid in papaya seed oil was oleic acid (18:1) (74.8%). The cavitation effect on the sample surface for oil extraction was identified using SEM analysis. Thermal stability of oil was analyzed using TGA and results showed that 71% (weight basis) of oil have been stable up to 319°C. FTIR analysis was confirmed that fatty acid functional groups were present in the oil.Practical applicationsThe continuous ultrasound acoustic cavitation technique improves the oil recovery (%) with a shorter extraction time and low solvent consumption. Moreover, the high intensity sonicator did not affect the fatty acid composition of the papaya seed oil. The oil sample contains 75% oleic acid (18:1) out of the total fatty acid composition, similar to the oleic acid composition of commercial vegetable oils such as Canola (75%), safflower (77%), olive (>75%), and sunflower (>80%). It can be used for frying purposes in food industry as it has high thermal stability, 71% by weight of oil stable till 319°C. Thus, the results show that this technique is a promising extraction technique for vegetable oil extraction from waste papaya seeds with high quality of fatty acid composition.

Continuous and pulsed ultrasound-assisted extractions of antioxidants from pomegranate peel

There is a great demand for developing efficient extraction methods in order to reduce extraction time and increase the yield and activity of functional antioxidants. The yields, activities, and extraction kinetics of antioxidants from the dry peel of pomegranate marc were studied using ultrasound-assisted extraction in continuous and pulsed modes and the results were compared with conventional extraction (CE) at a temperature of 25 ± 2 °C and water/peel ratio of 50/1, w/w. The studied factors were intensity level and treatment time for continuous ultrasound-assisted extraction (CUAE), and intensity level, number of pulse repetition, and pulse duration and interval for pulsed ultrasound-assisted extraction (PUAE). The results showed that all factors significantly affected the antioxidant yield, but only treatment time had a significant effect on the antioxidant activity. Compared to CE, PUAE at an intensity level of 59.2 W/cm 2, and a pulse duration of 5 s and a resting interval of 5 s increased the antioxidant yield by 22% and reduced the extraction time by 87%. Similarly, CUAE at the same intensity level increased the antioxidant yield by 24% and reduced the extraction time by 90%. Since PUAE had 50% energy saving compared to CUAE, we recommend using PUAE for the extraction with antioxidant yield of 14.5% and DPPH scavenging activity of 5.8 g/g. A second-order kinetic model was successfully developed for describing the mechanism of ultrasound-assisted extractions under PUAE and CUAE. This research clearly demonstrated the superiority of PUAE for producing antioxidants from peel of pomegranate marc.

Continuous and pulsed ultrasound-assisted extractions of antioxidants from pomegranate peel

There is a great demand for developing efficient extraction methods in order to reduce extraction time and increase the yield and activity of functional antioxidants. The yields, activities, and extraction kinetics of antioxidants from dry peel of pomegranate marc were studied using ultrasound-assisted extraction in continuous and pulsed modes and the results were compared with conventional extraction (CE) at a temperature of 25 ± 2 °C and water/peel ratio of 50/1, w/w. The studied factors were intensity level and treatment time for continuous ultrasound-assisted extraction (CUAE), and intensity level, number of pulse repetition, and pulse duration and interval for pulsed ultrasound-assisted extraction (PUAE). The results showed that all factors significantly affected the antioxidant yield, but only treatment time had a significant effect on the antioxidant activity. Compared to CE, PUAE at intensity level of 59.2 W/cm 2, and the 5 and 5 s of pulse duration and interval increased the antioxidant yield by 22% and reduced the extraction time by 87%. Similarly, CUAE at the same intensity level increased the antioxidant yield by 24% and reduced the extraction time by 90%. Since PUAE had 50% energy saving compared to CUAE, we recommend using PUAE for the extraction with antioxidant yield of 14.5% and DPPH scavenging activity of 5.8 g/g. A second-order kinetic model was successfully developed for describing the mechanism of ultrasound-assisted extractions under PUAE and CUAE. This research clearly demonstrated the superiority of PUAE for producing antioxidants from peel of pomegranate marc.

Automatic determination of nickel in foods by flame atomic absorption spectrometry

A new sensitive and low cost flow injection method that combines acid extraction, preconcentration and flame atomic absorption spectrometric determination of nickel in food samples at μg/g levels is described. The dynamic acid extraction step was carried out by using a continuous ultrasound-assisted extraction system. The acid extract was preconcentrated on-line on a minicolumn packed with a chelating resin (Serdolit Che, with iminodiacetic groups) and nickel was eluted with diluted hydrochloric acid, being continuously monitored by flame atomic absorption spectrometry. An experimental design (Plackett-Burman 26×3/16) is used to optimise the methodology proposed. The method allowed a total sampling frequency of 13–28 samples per hour. Good precision of the whole procedure (1.9–3.6% expressed as relative standard deviation) and a detection limit of 0.12μg/g, for 60mg of sample were achieved. The method was successfully applied to the determination of trace amounts of nickel in food samples.

Coupling continuous ultrasound-assisted extraction with ultrasonic probe, solid-phase extraction and high-performance liquid chromatography for the determination of sodium Danshensu and four tanshinones in Salvia miltiorrhiza bunge

A dynamic continuous ultrasound-assisted extraction with high intensity ultrasonic probe (CUAE-HIUP) combined with solid-phase extraction (SPE) for preconcentration and clean-up of the extract prior to high-performance liquid chromatography (HPLC) determination of the main biological active ingredients, sodium Danshensu and four tanshinones (dihydrotanshione I, tanshinone I, cryptotanshinone and tanshinone IIA) from root of Salvia miltiorrhiza bunge has been developed. An experimental design (Plackett–Burman design, 2 6 × 3/16) was used to optimize the CUAE-HIUP procedure and the SPE step. Detection limits of 1.2–4.2 × 10 −6 mg mL −1 were achieved with the preconcentration efficiency of more than 10-folds by the SPE procedure. The repeatability and within-laboratory reproducibility of the whole process, expressed as relative standard deviations (RSDs), were 1.5–3.6%, 1.6–3.1%, respectively. As compared with the conventional extraction techniques such as room temperature extraction (24 h), Soxhlet (4 h) and even microwave-assisted extraction (2 min), CUAE-HIUP achieved the highest extraction yield (98.9%) and the least amount (10 mL) of solvent compared with the other techniques (16 mL) in only 3 min. The method was successfully applied to the determination of the five biological active ingredients in root of S. miltiorrhiza bunge and Danshen-containing pharmaceutical formulations.

Continuous Ultrasound-Assisted Extraction Coupled to Flow Injection−Pervaporation, Derivatization, and Spectrophotometric Detection for the Determination of Ammonia in Cigarettes

A dynamic system for the continuous removal of ammonia from cigarettes with ultrasound assistance and iterative change of the flow direction of the extractant through the sample cell has been developed. A 0.1-g sample of cigarette was subjected to 7 min of ultrasound-assisted extraction (application and duration of pulse 0.7 s, output amplitude 85% of the converter nominal amplitude), and 1 M NaOH solution was used both as extractant and as carrier in the dynamic system. The ultrasound-assisted extractor was coupled to a pervaporation unit through a flow injection interface in order to develop a fully automated method. In arriving at the pervaporator, the ammonia is transferred from the donor-carrier stream to an acceptor stream, where the classical Berthelot reaction takes place--thus favoring pervaporation. The blue complex formed is spectrophotometrically monitored at 655 nm. The method was applied to the determination of ammonia in a selection of 10 European cigarette brands and Kentucky Reference 2R4F cigarettes.

Flow-Injection Flame Atomic Absorption Spectrometric Determination of Trace Amounts of Cadmium in Solid and Semisolid Milk Products Coupling a Continuous Ultrasound-Assisted Extraction System with the Online Preconcentration on a Chelating Aminomethylphosphoric Acid Resin

A new sensitive and low-cost method that combines continuous acid extraction, online preconcentration, and flame atomic absorption spectrometry for cadmium determination at microg levels in solid and semisolid milk products is described. A continuous ultrasound-assisted extraction system is used to carry out the dynamic acid extraction step. The acid extract is preconcentrated online on a minicolumn packed with a chelating resin (Chelite P, with aminomethylphosphoric acid groups), and the retained cadmium is eluted with hydrochloric acid and continuously monitored by flame atomic absorption spectrometry. An experimental design (Plackett-Burman 2-6*3/16) is used to optimize the continuous extraction and the preconcentration step. The method allowed a total sampling frequency of 28 samples/h. A good precision of the whole procedure (3.0% relative standard deviation) for a cheese sample containing 0.103 +/- 0.004 microg/g Cd (dry mass), a high enrichment factor (20.5), and detection and quantification limits of 0.014 and 0.067 microg/g, respectively, for a 60 mg of sample were obtained with this methodology. The method was successfully applied to the determination of trace amounts of cadmium in solid and semisolid milk products, such as cheese and yogurt samples.

Continuous ultrasound-assisted extraction of cadmium from legumes and dried fruit samples coupled with on-line preconcentration-flame atomic absorption spectrometry

Cadmium was continuously extracted with diluted nitric acid from legumes and dried fruit samples using a simple, rapid and continuous ultrasound-assisted extraction system. A minicolumn packed with a chelating resin (Chelite P, with aminomethylphosphoric acid groups) was placed between the extraction unit and the detector for cadmium preconcentration. The cadmium content in the acid extract was retained into the minicolumn, and elution was carried out with hydrochloric acid, with this trace metal continuously monitored by flame atomic absorption spectrometry. An experimental design (Plackett-Burman 2(6) x 3/16) was used to optimize the continuous leaching procedure and the preconcentration step. The method allowed a total sampling frequency of 10 and 14 samples per hour for legumes and dried fruit, respectively. The procedure displayed good precision (2.0 and 2.5%, respectively, expressed as relative standard deviations) for samples containing 0.202+/-0.005 microg g(-1) Cd (broad bean) and 0.239+/-0.004 microg g(-1) Cd (peanut). Detection limits of 0.014 microg g(-1) Cd for 60 mg of legume samples and 0.011 microg g(-1) Cd for 80 mg of dried fruit samples were obtained. The method was successfully applied to the determination of trace amounts of cadmium in legumes and dried fruit samples.

Continuous ultrasound-assisted extraction of cadmium from vegetable samples with on-line preconcentration coupled to a flow injection-flame atomic spectrometric system

A fully on-line flow injection method is described for the quantitative acid extraction of cadmium, preconcentration of this trace metal using a minicolumn containing a chelating resin and its determination by flame atomic absorption spectrometry (FAAS). The on-line acid extraction step was carried out using a continuous ultrasound-assisted extraction system (CUES). The acid extract was preconcentrated on a minicolumn packed with a chelating resin (CHELITE P, with aminomethylphosphoric acid groups), cadmium elution was carried out with hydrochloric acid, and this trace metal was continuously monitored by FAAS. A Plackett–Burman experimental design was used for optimization of the analytical procedure. The method allowed a total sampling frequency of 16 samples per hour, with a relative standard deviation for the complete procedure of 2.1; the detection and quantification limits were 0.014 µg/g and 0.067 µg/g for 60 mg of sample, respectively. The accuracy was verified using a standard reference material (NCS DC 73351 tea leaves). The analytical procedure was applied to the determination of trace amounts of cadmium in real vegetable and fruit samples.

Flow injection determination of copper and iron in seafoods by a continuous ultrasound-assisted extraction system coupled to FAAS

Copper and iron were extracted on-line from solid seafood samples by a robust, fast and simple continuous ultrasound-assisted extraction system (CUES). CUES is connected to a flow-injection manifold, which allows on-line flame atomic absorption spectrometric determination of copper and iron. Experimental designs were used to optimize the continuous leaching procedures. These methods allowed a total sampling frequency of 46 and 18 samples per hour, with relative standard deviations of 1.6% and 0.3%, for copper and iron, respectively (for a sample containing 13.6 µg/g of copper and 217.3 µg/g of iron (dry mass)). The limits of detection for 30 mg of sample were 0.3 µg/g for copper and 0.6 µg/g for iron (dry mass). Analytical procedures were verified by the analysis of a standard reference material (lobster hepatopancreas marine, TORT-1) and were applied to several real seafood samples from the estuaries of Galicia (Spain) with satisfactory results.

Fast on-line ultrasound-assisted extraction coupled to a flow injection-atomic absorption spectrometric system for zinc determination in meat samples

A continuous ultrasound-assisted extraction system connected to a flow injection manifold has been used for the on-line determination of zinc in meat samples by flame atomic absorption spectrometry. An experimental design was used for the optimisation of the continuous manifold. This flow injection methodology allowed a sampling frequency of ca. 80 samples per hour with a relative standard deviation for the whole procedure of 0.3% (for a sample containing 163.6 μg g −1 Zn). The detection limit was 0.6 μg g −1 for a sample amount of 5 mg. Accurate results were obtained by measuring certified reference materials (BCR-186 (pig kidney) and BCR-184 (bovine muscle)). The analytical procedure was applied to different real meat samples with satisfactory results.

Coupling continuous ultrasound-assisted extraction, preconcentration and flame atomic absorption spectrometric detection for the determination of cadmium and lead in mussel samples

Continuous ultrasound-assisted extraction has been coupled with preconcentration and flame atomic absorption spectrometry for the determination of cadmium and lead in mussel samples. Experimental designs were used for the optimisation of the leaching and preconcentration steps. The use of diluted nitric acid as extractant in the continuous mode at a flow rate of 3.5 ml min −1 and room temperature was sufficient for quantitative extraction of these trace metals. A minicolumn containing a chelating resin (Chelite P, with aminomethylphosphoric acid groups) was proved as an excellent material for the quantitative preconcentration of cadmium and lead prior to their flame atomic absorption detection. A flow injection manifold was used as interface for coupling the three analytical steps, which allowed the automation of the whole analytical process. A good precision of the whole procedure (2.0 and 2.3%), high enrichment factors (20.5 and 11.8) and a detection limit of 0.011 and 0.25 μg g −1 for cadmium and lead, respectively, were obtained for 80 mg of sample. The sample throughputs were ca. 16 and 14 samples h −1 for cadmium and lead, respectively. The accuracy of the analytical procedures was verified by using a standard reference material (BCR 278-R, mussel tissue) and the results were in good agreement with the certified values. The method was successfully applied to the determination of trace amounts of cadmium and lead in mussel samples from the coast of Galicia (NW, Spain).

Continuous ultrasound-assisted extraction coupled to a flow injection-flame atomic absorption spectrometric system for calcium determination in seafood samples.

Calcium was extracted on-line from solid seafood samples by a simple and rapid continuous ultrasound-assisted extraction system. This system is connected to a flow injection manifold, which allows the on-line flame atomic absorption spectrometric determination of calcium. This method enables the analysis of solid samples avoiding time-consuming traditional sample preparation methods and their inherent errors. The on-line manifold for calcium determination is the simplest possible, because a volume of 250 microL of acid extract is injected into an ultrapure water carrier stream. The acid extract was diluted on-line with lanthanum, which also acts as masking agent in order to avoid chemical interferences. The continuous monitoring of the calcium signal was accomplished by flame atomic absorption spectrometry. A Plackett-Burman experimental design was used for the optimisation of the continuous leaching procedure. The method allowed a total sampling frequency of 40 samples per hour, with a relative standard deviation for the complete procedure of 0.9% (for a sample containing 3414.35 mg/kg calcium (dry mass)). The limit of detection was found to be 44.4 mg/kg (dry mass) for 5 mg of sample. The analytical procedure was applied to real seafood samples.

Ultrasound-assisted extraction of nitropolycyclic aromatic hydrocarbons from soil prior to gas chromatography-mass detection

Continuous ultrasound-assisted extraction of nitropolycyclic aromatic hydrocarbons from soil prior to their individual separation and determination by gas chromatography (GC) with MS–MS detection is presented here. A multivariate optimisation of the variables affecting the continuous extraction step (namely, probe position, ultrasound radiation amplitude, percentage of duty cycle of ultrasonic exposure, sonication time, total extractant volume, extractant flow rate and temperature of the water-bath in which the extraction cell was placed) was performed. The method was compared with the reference EPA method 3540 using natural contaminated soils. Similar efficiencies were obtained but with a drastic reduction of both the extraction time (10 min versus 24 h) and the extractant volume (less than 10 ml versus 100 ml) by the proposed method. Detection limits of low picogram were obtained, with repeatability and reproducibility between 4.21–5.70 and 5.20–7.23%, respectively.

Flow injection on-line ultrasound-assisted extraction of iron in meat samples coupled to a flame atomic absorption spectrometric system.

Iron was extracted on-line from solid meat samples by a simple and rapid continuous ultrasound-assisted extraction system (CUES). The CUES is connected to a flow injection manifold, which allows the on-line flame atomic absorption spectrometric determination of iron. A Plakett-Burman design was used for the optimisation of the CUES. The method achieved a total sampling frequency of 11 samples per hour with a relative standard deviation for the complete procedure of 0.4%. The detection limit was 0.6 microg g(-1) (dry mass) for a sample amount of 30 mg. Accurate results were obtained by measuring the certified reference materials BCR-186 (pig kidney) and BCR-184 (bovine muscle). The analytical procedure was applied to different real meat samples with satisfactory results.

Continuous ultrasound-assisted extraction coupled to on line filtration–solid-phase extraction–column liquid chromatography–post column derivatisation–fluorescence detection for the determination of N-methylcarbamates in soil and food

A dynamic ultrasound-assisted method for the extraction of N-methylcarbamates (oxamyl, dioxacarb, metolcarb, carbofuran, carbaryl and isoprocarb) from soils and foods is proposed. The main factors affecting the extraction efficiency have been optimised by means of a central composite design. Pure water can be used as leaching agent. A flow injection manifold coupled to the extractor allows automation of the several steps involved in the analytical process. The method allows extraction of the carbamates from soil and food at 1 μg/g spiked level, with recoveries similar to those provided by the EPA 8318 method, without degradation of the target compounds during the extraction and with drastic shortening of the time required for this step (2 min vs. 4 h). Recoveries of the target analytes were 77–95% for spiked soil and 85–101% for spiked food. The detection and quantification limits were 12 and 40 ng/g, respectively, for all analytes, except carbaryl (detection and quantification limits 3 and 10 ng/ng, respectively). The relative standard deviations for repeatability and within-laboratory reproducibility were 3.1 and 7.5%, respectively.