Field-based supercritical fluid extraction of hydrocarbons at industrially contaminated sites. (1/62)

Examination of organic pollutants in groundwaters should also consider the source of the pollution, which is often a solid matrix such as soil, landfill waste, or sediment. This premise should be viewed alongside the growing trend towards field-based characterisation of contaminated sites for reasons of speed and cost. Field-based methods for the extraction of organic compounds from solid samples are generally cumbersome, time consuming, or inefficient. This paper describes the development of a field-based supercritical fluid extraction (SFE) system for the recovery of organic contaminants (benzene, toluene, ethylbenzene, and xylene and polynuclear aromatic hydrocarbons) from soils. A simple, compact, and robust SFE system has been constructed and was found to offer the same extraction efficiency as a well-established laboratory SFE system. Extraction optimisation was statistically evaluated using a factorial analysis procedure. Under optimised conditions, the device yielded recovery efficiencies of >70% with RSD values of 4% against the standard EPA Soxhlet method, compared with a mean recovery efficiency of 48% for a commercially available field-extraction kit. The device will next be evaluated with real samples prior to field deployment.  (+info)

Simultaneous measurement of fluoroquinolones in eggs by a combination of supercritical fluid extraction and high pressure liquid chromatography. (2/62)

Simultaneous detection of the fluoroquinolone antibiotics ciprofloxacin, enrofloxacin, ofloxacin, and norfloxacin in eggs by a combination of supercritical fluid extraction (SFE) and high pressure liquid chromatography (HPLC) was studied. Lipid matrices that have been considered to result in poor extraction and isolation of fluoroquinolones in eggs were removed first by SFE with supercritical CO(2) alone, and then the fluoroquinolones were extracted by SFE with supercritical CO(2) containing 20% (v/v) methanol for HPLC analysis. A time-course study of the extraction of lipid matrices of eggs suggested that the SFE method successfully removed the matrices within 20 min. When the fluoroquinolones added to control eggs were extracted by SFE, the extraction efficiency was similar to that by the solvent extraction method, giving the recovery percentages from 83 to 96% in a 40 min-extraction time. The fluoroquinolones extracted from eggs by SFE were analyzed simultaneously by HPLC equipped with a fluorescence detector with detection sensitivity at about 10 ppb for the detection limit. The standard calibration profiles of fluoroquinolones showed linear responses to HPLC, showing more than 0.995 for the mean r(2) value. This is the first report of the simultaneous measurement of fluoroquinolones in eggs by a combination of SFE and HPLC. Using the SFE method allowed us to avoid extensive sample preparation such as solvent extraction and chromatographic cleanup that are basically required in extraction of fluoroquinolones.  (+info)

Pesticide residues in canned foods, fruits, and vegetables: the application of Supercritical Fluid Extraction and chromatographic techniques in the analysis. (3/62)

Multiple pesticide residues have been observed in some samples of canned foods, frozen vegetables, and fruit jam, which put the health of the consumers at risk of adverse effects. It is quite apparent that such a state of affairs calls for the need of more accurate, cost-effective, and rapid analytical techniques capable of detecting the minimum concentrations of the multiple pesticide residues. The aims of this paper were first, to determine the effectiveness of the use of Supercritical Fluid Extraction (SFE) and Supercritical Fluid Chromatography (SFC) techniques in the analysis of the levels of pesticide residues in canned foods, vegetables, and fruits; and second, to contribute to the promotion of consumer safety by excluding pesticide residue contamination from markets. Fifteen different types of imported canned and frozen fruits and vegetables samples obtained from the Houston local food markets were investigated. The major types of pesticides tested were pyrethroids, herbicides, fungicides, and carbamates. By using these techniques, the overall data showed 60.82% of the food samples had no detection of any pesticide residues under this investigation. On the other hand, 39.15% different food samples were contaminated by four different pyrethroid residues +/- RSD% ranging from 0.03 +/- 0.005 to 0.05 +/- 0.03 ppm, of which most of the pyrethroid residues were detected in frozen vegetables and strawberry jam. Herbicide residues in test samples ranged from 0.03 +/- 0.005 to 0.8 +/- 0.01 ppm. Five different fungicides, ranging from 0.05 +/- 0.02 to 0.8 +/- 0.1 ppm, were found in five different frozen vegetable samples. Carbamate residues were not detected in 60% of investigated food samples. It was concluded that SFE and SFC techniques were accurate, reliable, less time consuming, and cost effective in the analysis of imported canned foods, fruits, and vegetables and are recommended for the monitoring of pesticide contaminations.  (+info)

Supercritical fluid clean-up of environmental samples for the analysis of polycyclic aromatic hydrocarbons using time-of-flight secondary ion mass spectrometry. (4/62)

A novel sample-pretreatment method for time-of-flight secondary ion mass spectrometry (TOF-SIMS) was developed using supercritical fluid extraction (SFE). In SFE, the extraction efficiency of a certain organic matter is controlled by the pressure and temperature of supercritical CO2. Two-step SFE (1st step at 10 Mpa, 40 degrees C; 2nd step at 30 MPa, 120 degrees C) was applied to diesel exhaust particles containing many kinds of n-alkanes and aromatic species. n-Alkanes and polycyclic aromatic hydrocarbons (PAHs) were extracted in the 1st and 2nd steps, respectively. This selectivity was utilized for the sample preparation of TOF-SIMS analysis. Diesel exhaust particles after the 1st step of extraction were analyzed with TOF-SIMS, aiming at PAHs as analytical targets. The obtained spectrum was simplified, and mass peaks of individual PAHs were easily assigned, because unwanted compounds, like n-alkanes, were selectively removed by SFE. Furthermore, a simple calculation elucidated the outline of the spectrum.  (+info)

Impacts of extraction methods in the rapid determination of atrazine residues in foods using supercritical fluid chromatography and enzyme-linked immunosorbent assay: microwave solvent vs. supercritical fluid extractions. (5/62)

It is an accepted fact that many food products that we eat today have the possibility of being contaminated by various chemicals used from planting to processing. These chemicals have been shown to cause illnesses for which some concerned government agencies have instituted regulatory mechanisms to minimize the risks and the effects on humans. It is for these concerns that reliable and accurate rapid determination techniques are needed to effect proper regulatory standards for the protection of people's nutritional health. This paper, therefore, reports the comparative evaluation of the extraction methods in the determination of atrazine (commonly used in agricultural as a herbicide) residues in foods using supercritical fluid chromatography (SFC) and enzyme-linked immunosorbent assay (ELISA) techniques. Supercritical fluid extraction (SFE) and microwave solvent extraction (MSE) methods were used to test samples of frozen vegetables, fruit juice, and jam from local food markets in Houston. Results showed a high recovery percentage of atrazine residues using supercritical fluid coupled with ELISA and SFC than with MSE. Comparatively, however, atrazine was detected 90.9 and 54.5% using SFC and ELISA techniques, respectively. ELISA technique was, however, less time consuming, lower in cost, and more sensitive with low detection limit of atrazine residues than SFC technique.  (+info)

Stabilized nanoparticles of phytosterol by rapid expansion from supercritical solution into aqueous solution. (6/62)

The basic objective of this work was to form stable suspensions of submicron particles of phytosterol, a water-insoluble drug, by rapid expansion of supercritical solution into aqueous solution (RESSAS). A supercritical phytosterol/CO2 mixture was expanded into an aqueous surfactant solution. In these experiments 4 different surfactants were used to impede growth and agglomeration of the submicron particles resulting from collisions in the free jet. The concentration of the drug in the aqueous surfactant solution was determined by high-performance liquid chromatography, while the size of the stabilized particles was measured by dynamic light scattering. Submicron phytosterol particles (<500 nm) were stabilized and in most cases a bimodal particle size distribution was obtained. Depending on surfactant and concentration of the surfactant solution, suspensions with drug concentrations up to 17 g/dm3 could be achieved, which is 2 orders of magnitude higher than the equilibrium solubility of phytosterol. Long-term stability studies indicate modest particle growth over 12 months. Thus, the results demonstrate that RESSAS can be a promising process for stabilizing submicron particles in aqueous solutions.  (+info)

Isolation of palm tocols using supercritical fluid chromatography. (7/62)

Crude palm oil contains 600 to 1000 ppm of tocols in the form of tocopherols and tocotrienols. These palm tocols have been isolated and analyzed in the past by various chromatographic techniques such as open column chromatography, high-performance liquid chromatography, as well as thin-layer chromatography. Supercritical fluid chromatography (SFC) has emerged as a more advanced chromatographic technique in recent years. The tocols present in palm oil are successfully isolated using SFC. Identification of these tocols is supported by various spectroscopic techniques such as 1H NMR, 13C NMR, and mass spectrometry.  (+info)

Feasibility study of online supercritical fluid extraction-liquid chromatography-UV absorbance-mass spectrometry for the determination of proanthocyanidins in grape seeds. (8/62)

Online coupling of supercritical fluid extraction (SFE) with liquid chromatography (LC)-UV absorbance-electrospray ionization (ESI)-mass spectrometry (MS) is evaluated for the determination of proanthocyanidins in grape seeds. The solid-phase intermediate trap is optimized in order to enhance the collection efficiency for the extracted polar components. Pure supercritical CO2 is used first to remove the oil in the seeds. Then methanol-modified CO2 is used to remove the polar components (e.g., phenolic compounds). Catechin and epicatechin (90%) are extracted out of the de-oiled after 240 min with 40% methanol as a modifier. Both singly-linked (B-type) and doubly-linked (A-type) procyanidins are identified by LC-ESI-MS, as well as their galloylated derivatives. The hyphenated system combines the extraction, separation, and detection in series. The experimental design minimizes the chance of analyte oxidation, degradation, and contamination. The traditional off-line SFE-LC method is also studied for comparison with the online method. Both advantages and disadvantages are observed for the online mode.  (+info)