Pressurized Fluid Extraction Research Articles

Pressurized fluid extraction of pistachio oil using a modified supercritical fluid extractor and factorial design for optimization

A pressurized fluid extraction (PFE) method for the extraction of pistachio oil was developed mainly as an analytical tool to determine oil content and/or its quality. The supercritical fluid extractor was modified to be able to pump liquid solvent and CO 2 into the extraction vessel alternatively. The extraction yield was found independent of the pressure in the range 10–150 bar tested. The addition of crushed glass increased the extraction yield by more than 15 g/100 g, while the extraction reproducibility expressed by percentage RSD was improved from 4 to 1. Furthermore, the use of crushed glass reduced the solvent consumption from 35 to 20 mL. The effective variables of temperature (40–80 °C), solvent volume (5–25 mL), and crushed glass percentage (30–60 g/100 g) were optimized by a factorial design method. The model allows the prediction of the extraction yield at different conditions. The PFE yield (i.e. 52.6 g/100 g) and fatty acid composition of pistachio oil were found similar to Soxhlet extraction and their variations were within the experimental uncertainty verified by statistical t-test analysis. Two different solvents of n-hexane and ethanol were used for PFE of pistachio oil. The extraction yield was about one-third (i.e. 18 g/100 g) when ethanol was used as solvent.

Determination of acrylamide in coffee and chocolate by pressurised fluid extraction and liquid chromatography–tandem mass spectrometry

A selective and sensitive procedure has been developed and validated for the determination of acrylamide in difficult matrices, such as coffee and chocolate. The proposed method includes pressurised fluid extraction (PFE) with acetonitrile, florisil® clean-up purification inside the PFE extraction cell and detection by liquid chromatography (LC) coupled to atmospheric pressure ionisation in positive mode tandem mass spectrometry (APCI–MS–MS). Comparison of ionisation sources (atmospheric pressure chemical ionisation (APCI), atmospheric pressure photoionization (APPI) and the combined APCI/APPI) and clean-up procedures were carried out to improve the analytical signal. The main parameters affecting the performance of the different ionisation sources were previously optimised using statistical design of experiments (DOE). PFE parameters were also optimised by DOE. For quantitation, an isotope dilution approach was used. The limit of quantification (LOQ) of the method was 1 µg kg−1 for coffee and 0.6 µg kg−1 for chocolate. Recoveries ranged between 81–105% in coffee and 87–102% in chocolate. The accuracy was evaluated using a coffee reference test material FAPAS T3008. Using the optimised method, 20 coffee and 15 chocolate samples collected from Valencian (Spain) supermarkets, were investigated for acrylamide, yielding median levels of 146 µg kg−1 in coffee and 102 µg kg−1 in chocolate.

Comparison of two different solvents employed for pressurised fluid extraction of stevioside from Stevia rebaudiana: methanol versus water

Pressurised fluid extraction using water or methanol was employed for the extraction of stevioside from Stevia rebaudiana Bertoni. The extraction method was optimised in terms of temperature and duration of the static or the dynamic step. Extracts were analysed by liquid chromatography followed by UV and mass-spectrometric (MS) detections. Thermal degradation of stevioside was the same in both solvents within the range 70-160 degrees C. Methanol showed better extraction ability for isolation of stevioside from Stevia rebaudiana leaves than water within the range 110-160 degrees C. However, water represents the green alternative to methanol. The limit of detection of stevioside in the extract analysed was 30 ng for UV detection and 2 ng for MS detection.

Determination of bitter orange alkaloids in dietary supplement Standard Reference Materials by liquid chromatography with atmospheric-pressure ionization mass spectrometry

A liquid chromatographic atmospheric-pressure ionization electrospray mass spectrometry (LC-API-ES-MS) method has been developed for the determination of five bitter orange alkaloids (synephrine, octopamine, n-methyltyramine, tyramine, and hordenine) in bitter orange-containing dietary supplement standard reference materials (SRMs). The materials represent a variety of natural, extracted, and processed sample matrices. Two extraction techniques were evaluated: pressurized-fluid extraction (PFE) and sonication extraction. The influence of different solvents, extraction temperatures, and pH were investigated for a plant material and a processed sample. The LC method uses a new approach for the separation of highly polar alkaloids. A fluorinated, silica-based stationary phase separated the five alkaloids and the internal standard terbutaline in less than 20 min. This method enabled the determination of the dominant alkaloid synephrine and other minor alkaloids in a variety of dietary supplement SRMs.

Application of pressurized fluid extraction technique in the gas chromatography–mass spectrometry determination of sterols from marine sediment samples

In order to determine steroid compounds in GC/MS an analytical method using pressurized fluid extraction (PFE) was developed. While extracting in-house reference material (coastal sediment) typical recovery in PFE ranged from 80 to 120% (±2.5–14.5) and the average extraction yield in PFE in comparison to conventional soxhlet extraction was 115%. In particular, the PFE showed higher extraction efficiency for C 29 and dien sterols. Optimizing parameters such as temperature and pressure is critical in achieving this efficiency. Sterols in the sediment were derivatized with silyl reagent BSTFA in acetone for the final determination. A short column florisil cleanup offered the best separation of the GC/MS sensitive derivatives from co-contaminants. Thirty-three coastal sediment samples were analyzed using PFE and Soxhlet extraction methods. The results on extraction efficiency, silyl derivatization kinetics and purification efficiency demonstrated that PFE is far superior in extracting sterols from sediment samples. It is simple, fast, efficient and amenable for automation.

Comparison of various extraction techniques for isolation and determination of isoflavonoids in plants

In the present paper, the following extraction techniques have been used for extracting isoflavonoids from the species Matricaria recutita, Rosmarinus officinalis, Foeniculum vulgare, and Agrimonia eupatoria L.: supercritical fluid extraction (SFE), pressurized fluid extraction, matrix solid phase dispersion, ultrasonic extraction in an ultrasonic bath (USE) and by means of an ultrasonic homogeniser (HOM), extraction by means of Soxhlet apparatus (SOX), and solid phase extraction. Experimental optimization of all techniques has been carried out using a soybean flour. Subsequent analyses of the extracts were carried out by liquid chromatography with UV detection. The maximum yields of daidzein and genistein were obtained by extraction with the SOX, USE, and HOM techniques. The maximum yields of apigenin and biochanin A from herb samples were obtained by SFE.

Analysis of Degradation Products of Non-Persistent Pesticides in Soil Using Liquid Chromatography-Tandem Mass Spectrometry

P-561 Abstract: Non-persistent pesticides were developed to counteract the persistence and bioaccumulation concerns associated with persistent pesticides. By their nature, they degrade in the environment quickly releasing multiple degradation products. The currently applied model for assessing organophosphorus (OP) pesticide exposure is through measuring non-specific dialkylphosphates and OP-specific metabolites in urine as biomarkers of exposure. This model assumes that measuring the metabolites in the body are good markers of exposure to parent pesticides in the environment. In this assumption, there exists a direct correlation between concentrations of parent pesticide in the environment to concentration of metabolite formed in urine. However, the model is obscured by the fact that OP pesticide breakdown products in the environment are usually the same chemical as the metabolite measured in the body. The potential contribution of degradation products found in the environment to the metabolite concentration found in people needs to be assessed. In order to determine this correlation, analytical methods need to be developed to extract, quantitate and evaluate breakdown products in environmental matrices. A single method for analyzing two classes of non-persistent pesticide (OP and pyrethroids) breakdown products in soil was developed. Pesticide degradation products were extracted from soil using pressurized fluid extraction (Dionex ASE®) followed by analysis using liquid-chromatography with atmospheric pressure chemical (APCI) and electrospray ionization (ESI) and tandem mass spectrometry. Additional clean-up steps post ASE® extraction were evaluated to determine any enhanced sensitivity and selectivity of target analytes. Nonspecific, specific OP and pyrethroid degradation products were isolated using ion exchange (for non-specific) and reversed phase (specific and pyrethroids) solid phase extraction post ASE extraction and analyzed with ESI and APCI with detection limits in the sub parts per billion to low parts per billion range with recoveries ranging from 70–110%. The results of these investigations lead to a single robust method capable of analyzing degradation products from two classes of pesticides with excellent recovery, sensitivity, and precision. As a consequence of the development of this method, initiation of studies determining how much, if any, degradation product formed in the environment contributes to the concentration of biomarkers in urine.

Application of pressurized fluid extraction to determine cadmium and zinc in plants

A procedure for the determination of Cd and Zn in plants is proposed. The metals are extracted by pressurized fluid extraction (PFE). Operational conditions are: pressure 1500 psi, temperature 75 °C, static time 5 min, flush volume 35%, purge time 60 s, cycles 1 and 1,2-diaminocyclohexane- N, N, N′, N′-tetraacetic acid (CDTA) 0.01 M at pH 4.5 as extracting solution. Determination of Zn is carried out by flame atomic absorption spectroscopy and depending on the concentration level, Cd content is determined by flame or electrothermal atomic absorption spectroscopy. Certified samples of Virginia tobacco leaves, tea leaves, spinach leaves, poplar leaves, a commercial spinach sample ( Spinacea oleracea) and genetically modified Arabidopsis thaliana were analysed by the proposed procedure and also by microwave acid digestion and extraction with HCl–Triton X-100. Confidence intervals for Cd and Zn content obtained by the proposed procedure overlap with the certified values. The other procedures, however, provide inaccurate results for Cd. Recoveries obtained for a confidence level of 95% are 96 ± 6% and 95 ± 5% for Zn and Cd, respectively. Reproducibility of Zn by the proposed procedure is 7% ( n = 8), similar to the other tests and the detection limit is 2.6 μg. For Cd reproducibility is 8.5% ( n = 8), better than with HCl–Triton X-100 and similar to acid digestion, the detection limit is 3.5 ng of Cd.

Specific detection of prion antigenic determinants retained in bovine meat and bone meal by flow microbead immunoassay

The purpose of this study was to develop an effective method for detecting prion (PrP) antigenic determinants remaining in bovine meat and bone meal (MBM) using pressurized fluid extraction (PSE) equipment and flow microbead immunoassay (FMI). Using the FMI, bovine recombinant PrP could be determined quantitatively in the 7 pmol-7 nmol range using anti-PrP peptide polyclonal antibody-coupled microbeads and anti-PrP monoclonal antibody (SAF61) as a detection antibody. PSE extraction at 120 degrees C for 5 min under high pressure was most effective for eluting PrP determinants from bovine MBMs. The FMI was capable of detecting PrP determinants in bovine MBM extracts with high specificity and indicated that the MBMs contained high levels of PrP determinants. This assay was also applied to the detection of PrP(Sc) determinants in bovine MBM spiked with a scrapie-infected brain at a weight ratio of 50 : 1. These data indicate that this assay was effective for the specific detection of PrP determinants contained in bovine MBM extracts. To our knowledge, this is the first report detailing the detection of PrP determinants in bovine MBM. The assay could be applied to securing the safety of bovine MBM.

Determination of oleamide and erucamide in polyethylene films by pressurised fluid extraction and gas chromatography

A pressurized fluid extraction (PFE) and gas chromatography-flame ionization detection (GC-FID) method is proposed to determine the slip agents in polyethylene (PE) films. The study of PFE variables was performed using a fractional factorial design (FFD) for screening and a central composite design (CCD) for optimizing the main variables obtained from the Pareto charts. The variables that were studied include temperature, static time, percentage of cyclohexane and the number of extraction cycles. The final condition selected was pure isopropanol (two times) at 105 °C for 16 min. The recovery of spiked oleamide and erucamide was around 100%. The repeatability of the method was between 9.6% for oleamide and 8% for erucamide, expressed as relative standard deviation. Finally, the method was applied to determine oleamide and erucamide in several polyethylene films and the results were statistically equal to those obtained by pyrolysis and gas-phase chemiluminescence (CL).

Development and evaluation of methods for determination of naphthodianthrones and flavonoids in St. John's wort

Several major constituents in St. John's wort were determined for a homogenized plant sample. Three extraction techniques were evaluated: Soxhlet extraction, pressurized-fluid extraction (PFE), and sonication extraction. Levels of nine constituents (chlorogenic acid, rutin, hyperoside, isoquercitrin, quercitrin, quercetin, amentoflavone, pseudohypericin, and hypericin) were measured using liquid chromatography with ultraviolet/visible absorbance, mass spectrometric, and fluorescence detection. Levels of total naphthodianthrones determined by liquid chromatography (LC) with absorbance detection at 590 nm were compared with levels determined by direct spectrophotometry at the same wavelength. Additionally, the methods described in this paper were applied to several brands of St. John's wort finished products.

Investigation of extraction procedures and HPLC-DAD/MS for the determination of the brominated flame retardant tetrabromobisphenol A bis(2,3-dibromopropylether) in environmental samples

A method for the determination of the novel brominated flame retardant tetrabromobisphenol A bis(2,3-dibromopropylether), 1,1'-(isopropylidene)bis[3,5-dibromo-4-(2,3-dibromo-propoxy)-benzene] (TBBPA-dbpe), was developed. Technical TBBPA-dbpe was purified and the results of a thorough physical characterisation are reported. The application of APCI-MS is discussed and the fragmentation patterns are described. Quantification of TBBPA-dbpe was done by HPLC-DAD using external calibration. The validation of the method was accomplished using sediment and sewage sludge samples spiked with defined amounts of authentic TBBPA-dbpe. The average recovery rates of TBBPA-dbpe from spiked samples ranged from 35 to 91% (sediment) and from 57 to 98% (sewage sludge) depending on the respective extraction method. Pressurised fluid extraction (PFE) and fluidised bed extraction were superior to classical Soxhlet and sonication procedures and yielded recovery rates between 90 and 98% with relative standard deviations of 2%. The limits of detection (DTC), identification (ID) and determination (DTM) using HPLC-DAD were 10, 21 and 30 ng g(-1) in sediment and 22, 44 and 72 ng g(-1) in sewage sludge, respectively.

Determination of acrylamide in foods by pressurized fluid extraction and liquid chromatography-tandem mass spectrometry used for a survey of Spanish cereal-based foods

An automated and rapid method for the determination of acrylamide in different food products is presented. The method involves pressurized fluid extraction (PFE) of foods with acetonitrile and precipitation with Carrez reagents. The final extract is analysed by liquid chromatography coupled to electrospray ionization tandem mass spectrometry (ESI-MS-MS). The main parameters affecting the performance of ESI-MS-MS and PFE were optimized using a design of experiments approach. The limit of quantification of the method was 5 µg kg−1, and recoveries from incurred samples ranged between 93 and 101%. The accuracy was evaluated using the reference test materials FAPAS T3002, T3005 and T3011. Using the optimized method, 62 food samples of potato chips, snacks, biscuits, breakfast cereals and crisp bread sampled from Valencia, Spain, supermarkets were surveyed for acrylamide levels. The levels were similar to those reported in the European Union and USA.

Comparison of pressurized fluid extraction, Soxhlet extraction and sonication for the determination of polycyclic aromatic hydrocarbons in urban air and diesel exhaust particulate matter

In order to characterize and compare the chemical composition of diesel particulate matter and ambient air samples collected on filters, different extraction procedures were tested and their extraction efficiencies and recoveries determined. This study is an evaluation of extraction methods using the standard 16 EPA PAHs with HPLC fluorescence analysis. Including LC analysis also GC and MS methods for the determination of PAHs can be used. Soxhlet extraction was compared with ultrasonic agitation and pressurized fluid extraction (PFE) using three solvents to extract PAHs from diesel exhaust and urban air particulates. The selected PAH compounds of soluble organic fractions were analyzed by HPLC with a multiple wavelength shift fluorescence detector. The EPA standard mixture of 16 PAH compounds was used as a standard to identify and quantify diesel exhaust-derived PAHs. The most effective extraction method of those tested was pressurized fluid extraction using dichloromethane as a solvent.

Determination of 2,4,6-trichloroanisole and guaiacol in cork stoppers by pressurised fluid extraction and gas chromatography–mass spectrometry

This paper describes the development of an analytical method consisting of pressurised fluid extraction (PFE) and gas chromatography–mass spectrometry (GC–MS) using experimental designs to determine two volatile compounds in naturally-tainted cork stoppers. The target analytes, 2,4,6-trichloroanisole (2,4,6-TCA) and guaiacol, are involved in the cork taint of wine. First, a Plackett–Burman experimental design was carried out in order to determine the significant experimental parameters affecting the PFE process, and then a central composite design was used to optimise these significant parameters. Once the method had been optimised, the influence of the number of extraction cycles was studied. The method was applied to determine the concentration of 2,4,6-TCA and guaiacol in three cork samples, and the results were compared with the ones obtained by multiple headspace-solid-phase microextraction (MHS-SPME) and by Soxhlet extraction.

Experimental design approach for the optimisation of pressurised fluid extraction of additives from polyethylene films

A pressurised fluid extraction (PFE) and normal-phase-high performance liquid chromatography (NP-HPLC) method is proposed for the determination of additives in polyethylene films. The study of PFE variables was performed using a Plackett–Burman (PB) experimental design for screening and a central composite design (CCD) for optimising the main variables obtained from the Pareto charts. The studied variables were: temperature, time, cyclohexane (CHx) and tetrahydrofuran (THF) as modifiers, flush volume and extraction cycles, and an isopropanol:CHx (92.5:7.5) mixture twice at 105 °C for 15 min were the final conditions selected. The additives in the PFE extracts were separated by NP-HPLC using a silica column and a gradient n-hexane:dichloromethane:acetonitrile mobile phase. Additive solubility is higher in normal-phase solvents; thus, their separation can be carried out at room temperature. Finally, the method was applied to determine additives in several polyethylene films.

Application of Photoassisted Electrochemical Detection to Explosive-Containing Environmental Samples

High-performance liquid chromatography (HPLC) with ultraviolet (UV) absorbance and photoassisted electrochemical detection (PAED) is applied to the determination of explosives in groundwater and soil samples. On-line, solid-phase extraction minimizes sample pretreatment, enabling direct analysis of groundwater samples and soil extracts. Soils are extracted using pressurized fluid extraction, which is compared to the Environmental Protection Agency (EPA) sonication method. Limits of detection for explosives in the matrixes of interest are equivalent or superior (i.e., <10 parts-per-trillion for HMX) to those achieved using the EPA method 8330. HPLC-UV-PAED is also shown here to be more broadly applicable, as it is capable of determining nitro compounds of interest (e.g., nitroglycerin) that have poor UV chromophores. Additional selectivity of amine-substituted nitroaromatic explosives is achieved by using a photochemical reactor with a 366-nm wavelength lamp. By coupling reversed-phase columns of different selectivities together, baseline resolution of all 14 standard explosives is demonstrated.

Comparison of Three Extraction Methods for 17 β-Estradiol in Sand, Bentonite, and Organic-Rich Silt Loam

Extraction is an important procedure for samples that contain soil because other compounds in soil may affect analysis of estrogens. This study was conducted to evaluate three different extraction methods for 17β-estradiol in soil. Sand, bentonite, and organic-rich silt loam were spiked with 1 mg kg− 1 of 17β-estradiol as a model compound of estrogens. 17β-estradiol and its metabolites, estrone and estriol, were extracted using (i) a modified Bligh and Dyer extraction, (ii) a pressurized fluid extraction, and (iii) a diethyl ether extraction, and measured by liquid chromatography tandem mass spectrometry. There were significant differences in the extraction efficiency for 17β-estradiol among the extraction methods and the soils: the efficiencies ranged from 10% to 97%. Overall, the diethyl ether extraction method had the largest efficiency of 17β-estradiol with 45% and 57% for bentonite and silt loam, respectively. Transformation of 17β-estradiol to estrone and estriol in the different extraction methods was less than 3.6% during the extraction procedures. This study underlined the importance of sample preparation for estrogen analysis in soil samples.

Analysis of polycyclic aromatic hydrocarbons adsorbed on particles of atmospheric interest using pressurised fluid extraction

Pressurised fluid extraction (PFE) was used for the measurement of 13 polycyclic aromatic hydrocarbons (PAHs) adsorbed on different types of particles: two model particles (PAH-coated silica, PAH-coated graphite) and two natural atmospheric particles (urban dust and diesel exhaust, from NIST reference materials). Samples were analysed by gas chromatography coupled to mass spectrometry. Extraction efficiency was evaluated with internal standard recovery yields and was shown to depend on the nature of the particle, on the structure of the analytes and on the PAH concentration. Extraction conditions (toluene, 130 degrees C, 130 bar, 2 x 8-min static cycles) were optimised to extract PAHs when strongly interacting with solid matrices and were validated by the analysis of two PAH-certified materials.

Development of a procedure for the determination of perfluorocarboxylic acids in sediments by pressurised fluid extraction, headspace solid-phase microextraction followed by gas chromatographic–mass spectrometric determination

A procedure for the determination of perfluorocarboxylic acids (i.e. PFC 7–10A) in sediment by pressurized fluid extraction (PFE), derivatization, headspace solid-phase microextraction and GC–MS determination in the negative ion chemical ionisation mode was developed. The PFE extraction variables such as solvent composition, number and time per extraction cycle, and extraction temperature were optimised. In the optimum extraction conditions, recoveries exceeding 95% with a limit of detection and RSDs of 0.5–0.8 ng g −1 and 15.5–16.8%, respectively, were obtained. The developed analytical procedure was applied to harbour sediments where PFC 8A and PFC 10A were detected for the first time at low ppb concentrations (i.e. 8–11 ng g −1).