Optimization of subcritical fluid extraction of bioactive compounds using Hansen solubility parameters.

Process engineering operations in food and nutraceutical industries pertaining to the design of extraction of value-added products from biomass using pressurized liquids involve a careful selection of the solvent and optimal temperature conditions to achieve maximum yield. Complex molecular structure and limited physical property data in the literature of biological solutes extracted from biomass compounds have necessitated the process modeling of such operations. In this study, we have applied the Hansen 3-dimensional solubility parameter concept to optimize the extraction of molecularly complex solutes using subcritical fluid solvents. Hansen solubility spheres characterized by the relative energy differences (RED) have been used to characterize and quantify the solute-subcritical solvent interactions as a function of temperature. The solvent power of subcritical water and compressed hydroethanolic mixtures above their boiling points has been characterized using the above-mentioned method. The use of group contribution methods in collaboration with computerized algorithms to plot the Hansen spheres provides a quantitative prediction tool for optimizing the design of extraction conditions. The method can be used to estimate conditions for solute-solvent miscibility, an optimum temperature range for conducting extractions under pressurized conditions, and approximate extraction conditions of solutes from natural matrices.

Atlantic forcing of persistent drought in West Africa.

Although persistent drought in West Africa is well documented from the instrumental record and has been primarily attributed to changing Atlantic sea surface temperatures, little is known about the length, severity, and origin of drought before the 20th century. We combined geomorphic, isotopic, and geochemical evidence from the sediments of Lake Bosumtwi, Ghana, to reconstruct natural variability in the African monsoon over the past three millennia. We find that intervals of severe drought lasting for periods ranging from decades to centuries are characteristic of the monsoon and are linked to natural variations in Atlantic temperatures. Thus the severe drought of recent decades is not anomalous in the context of the past three millennia, indicating that the monsoon is capable of longer and more severe future droughts.

Nonlinear time series analysis of food intake in the dab and the rainbow trout.

Evidence suggests that dab and rainbow trout are able to quickly adjust their food intake to an appropriate level when offered novel diets. In addition day-to-day and meal-to-meal food intake varies greatly and meal timing is plastic. Why this is the case is not clear: Food intake in fish is influenced by many factors, however the hierarchy and mechanisms by which these interact is not yet fully understood. A model of food intake may be helpful to understand these phenomena; to determine model type it is necessary to understand the qualitative nature of food intake. Food intake can be regarded as an autoregressive (AR) time series, as the amount of food eaten at time t will be influenced by previous meals, and this allows food intake to be considered using time series analyses. Here, time series data were analysed using nonlinear techniques to obtain qualitative information from which evidence for the hierarchy of mechanisms controlling food intake may be drawn. Time series were obtained for a group of dab and individuals and a group of rainbow trout for analysis. Surrogate data sets were generated to test several null hypotheses describing linear processes and all proved significantly different to the real data, suggesting nonlinear dynamics. Examination of topography and recurrence diagrams suggested that all series were deterministic and non-stationary. The point correlation dimension (PD2i) suggested low-dimensional dynamics. Our findings suggest therefore that any model of appetite should create output that is deterministic, non-stationary, low-dimensional and having nonlinear dynamics.

Hydralazine as antihypertensive therapy in obesity-related hypertension.

OBJECTIVE: The objectives were two-fold: (1) determine whether the use of hydralazine as antihypertensive therapy during obesity development exacerbated obesity-related cardioacceleration and hormonal abnormalities; (2) determine whether the absence of hypertension in obesity attenuated obesity-related abnormalities in hemodynamics, cardiac hypertrophy, and hormonal profile. DESIGN: Female New Zealand White rabbits were divided into lean control (n=12), lean hydralazine-treated (n=9), obese control (n=11), and obese hydralazine-treated (n=8) groups. Pretreatment mean blood pressure (BP) and heart rate (HR) were determined using telemetry. Pretreatment BP was maintained during 12 weeks of obesity development using hydralazine. MEASUREMENTS: Chronically measured BP and HR; plasma/blood volume; wet and dry ventricular weights; body fat/water; and hormonal profile (plasma renin activity, aldosterone, cortisol, atrial natriuretic peptide, adrenaline, and noradrenaline). RESULTS: Hydralazine treatment in obese animals attenuated obesity-related renin-angiotensin system (RAS) activation. In contrast, RAS was activated in lean hydralazine, as indicated by increased plasma aldosterone. The absence of hypertension in obese hydralazine did not result in attenuation of cardioacceleration, cardiac hypertrophy, or intravascular volumes. CONCLUSIONS: Hydralazine treatment in obese rabbits did not exacerbate obesity-related cardiovascular and hormonal alterations. Cardioacceleration and cardiac hypertrophy persisted in obese hydralazine despite BP control, suggesting hypertension-independent effects of obesity on these variables. Hydralazine's effects on RAS activation differed in lean and obese rabbits, suggesting that the systemic effects of hydralazine as a control therapy in evaluation of antihypertensive medications may differ depending on the underlying pathology.

Variability in AC amplifier distortions: estimation and correction.

AC amplifiers can introduce significant distortions into the low frequency and DC components of recorded electrophysiological data such as event-related potentials (ERPs). Methods for correcting such distortions (i.e., estimating the waveform of the original data) after the data have been amplified and recorded rely on an accurate estimate of the amplifier's time constant (TC). We show that the filter characteristics of AC amplifiers in at least some commercially available ERP recording instruments may vary considerably across individual channels, even when each houses an identical AC amplifier circuit. Clearly, distortion correction methods must take this variability into account. We propose an empirical means of estimating the correct TC value. This approach yields more accurate correction than those based on TCs calculated analytically.

Possible clinically significant interaction of itraconazole plus rifampin.

We report two patients treated with the combination of itraconazole plus rifampin for more than 4 months. While on itraconazole plus rifampin, patient 1 lost weight at a rate of 30 g/d. After stopping rifampin, he gained 14 g/d. While on itraconazole plus rifampin, patient 2 lost 41 grams/day. After stopping rifampin, he gained 33 g/d. Weight loss while taking the combination of itraconazole plus rifampin, followed by weight gain after stopping rifampin, suggests the possibility of a clinically significant drug interaction between itraconazole and rifampin.

Supercritical fluid extraction of fat from ground beef: effects of water on gravimetric and GC-FAME fat determinations.

This study investigated the supercritical carbon dioxide (SC-CO(2)) extraction of fat from ground beef and the effects of several factors on the gravimetric determination of fat. The use of ethanol modifier with the SC-CO(2) was not necessary for efficient fat extraction; however, the ethanol did increase the coextraction of water. This coextraction of water caused a significant overestimation of gravimetric fat. Oven-drying ground beef samples prior to extraction inhibited the subsequent extraction of fat, whereas oven-drying the extract after collection decreased the subsequent gas chromatographic fatty acid methyl ester (GC-FAME) fat determination. None of the drying agents tested were able to completely prevent the coextraction of water, and silica gel and molecular sieves inhibited the complete extraction of fat. Measurements of collection vial mass indicated that CO(2) extraction/collection causes an initial increase in mass due to the density of CO(2) (relative to displaced air) followed by a decrease in vial mass due to the removal of adsorbed water from the collection vial. Microwave-drying of the empty collection vials removes approximately 3 mg of adsorbed water, approximately 15-20 min is required for readsorption of the displaced water. For collection vials containing collected fat, microwave-drying effectively removed coextracted water, and the vials reached equilibration after approximately 10-15 min. Silanizing collection vials did not significantly affect weight loss during microwave-drying. SC-CO(2) can be used to accurately determine fat gravimetrically for ground beef, and the presented method can also be followed by GC-FAME analysis to provide specific fatty acid information as well.

Fatty and resin acid analysis in tall oil products via supercritical fluid extraction-supercritical fluid reaction using enzymatic catalysis.

Supercritical fluid extraction (SFE) is combined with supercritical fluid reaction (SFR) in an analytical mode to assess tall oil products for their fatty or resin acid content or both. The SFR consists of an inline enzymatically catalyzed reaction in which a lipase transesterifies specific lipids with methanol. The SFE-SFR sequence is conducted employing commercially available extractors using supported lipases in the extraction cell to form methyl esters. In this study, six different commercially available lipases are screened for activity. The SFE-SFR extracts are analyzed by capillary gas chromatography and supercritical fluid chromatography and then compared with tall oil products derivatized by conventional chemical derivatization techniques.

Comparison of hepatitis C viral loads in patients with or without human immunodeficiency virus.

A better understanding of how human immunodeficiency virus (HIV) coinfection affects the course of hepatitis C virus (HCV) infection is required to select patients with HIV who would benefit from current HCV therapy. Between June 1996 and March 2000, HCV RNA levels were quantified for 1,279 patients at the Louisiana State University Health Sciences Center; 28 of these patients were coinfected with HIV. HCV loads were quantified by the Bayer branched-DNA assay with a lower limit of detection of 0.2 Meq/ml. We compared the median HCV RNA levels of for patients coinfected with HIV and HCV and patients infected only with HCV who were in the same age range (23 to 55 years). The median HCV load for the 28 patients coinfected with HCV and HIV (17.8 Meq/ml) was significantly greater (P < 0.05) than that for similarly aged patients infected only with HCV (6.1 Meq/ml). The HCV load did not correlate with age or sex for either group of patients. A significant (R = -0.4; P < 0.05) negative correlation was observed between HCV load and CD4 count in the coinfected group, for whom the CD4 counts at the time of HCV load analysis ranged from 6 to 1,773/mm(3). The increased HCV load in patients coinfected with HCV and HIV compared to that in patients infected only with HCV and the inverse relationship of the HCV load to the CD4 count indicate that immunosuppression results in decreased control of HCV replication. In addition, we report significantly higher HCV loads among coinfected African Americans than Caucasians.

Ethanol-modified subcritical water extraction combined with solid-phase microextraction for determining atrazine in beef kidney.

The determination of the levels of pesticides in food products has prompted the development of sensitive and rapid methods of analysis that are solvent-free or utilize solvents that are benign to the environment and laboratory worker. In this study we have developed a novel extraction method that utilizes ethanol-modified subcritical water in combination with solid-phase microextraction (SPME) for the removal of atrazine from beef kidney. In situ sample cleanup was achieved using the technique of matrix solid-phase dispersion. A cross-linked polymer, XAD-7 HP, was utilized as a dispersing material for kidney samples. Subcritical water extractions were performed with a pressurized solvent extraction unit at 100 degrees C and 50 atm. Experimental parameters investigated were the volume of solvent and amount of modifier required for the complete extraction of atrazine and optimization of the extraction time. It was determined that 30% ethanol in water (v/v) is adequate for the complete extraction of atrazine. A Carbowax-divinylbenzene SPME fiber was used to sample the aqueous extracts. Analysis of the fiber contents was by ion-trap GC/MS utilizing the single ion mode. The total time of analysis for a single kidney sample is 90 min. The average percent recoveries from samples spiked to the concentrations of 2 and 0.2 microg/g were 104 and 111, respectively. The average relative standard deviations were 10 and 9, respectively. The method limit of detection for beef kidney spiked with atrazine was found to be 20 ng/g of sample.

Determination of crude fat in meat by supercritical fluid extraction: direct method: PVM 3:2000.

Meat samples are prepared by passing meat through a food chopper, bowl cutter, or food processor, subsampling the meat, and mixing the meat with granular diatomaceous earth. No drying step is necessary. Supercritical CO2 is then used to extract crude fat (which is defined as the components of meat that are extractable with petroleum ether, without digestion of the sample). Extracted material is deposited on glass wool contained in collection vials. After removal of any residual moisture from the extracts, percent crude fat is determined by weight gain of the collection vial. This method has been peer-verified by 3 laboratories, for a wide variety of raw and processed meat products containing 6-28% crude fat. Samples were prepared at the submitting laboratory. Ground samples were split into 4 portions, packed in Whirlpack bags, and immediately frozen. Frozen samples were sent by overnight room temperature, and percent fat was determined (in triplicate), without further processing of the samples. Analysis of the samples was completed within 1 week of sample prepara. tion. On the basis of this study, it can be estimated that all repeatability and reproducibility values are <3.0. Mean accuracy of the direct gravimetric supercritical fluid extraction method for meat samples ranged from +0.22 to -1.41 when the method was compared with AOAC Method 960.39. Interferences are unlikely but would include any nonfat substance that is added to (processed) meat, is soluble in nonpolar solvents, and is present in a quantity that would alter results. This method is expected to perform equally well for all meats with fat content within the stated range of applicability.

On-line supercritical fluid extraction/enzymatic hydrolysis of vitamin a esters: a new simplified approach for the determination of vitamins a and e in food.

An on-line supercritical fluid extraction (SFE)/enzymatic hydrolysis procedure using immobilized lipase has been developed for the determination of vitamin A in dairy and meat products. Several lipases were tried, of which Novozyme 435 (Candida antarctica type B) showed the highest activity toward retinyl palmitate. There was no observed activity with alpha-tocopheryl acetate. When pressure, temperature, modifiers, flow rate, extraction time, and water content were varied, high vitamin A recovery was obtained in milk powder. Collected extracts were analyzed by reversed-phase high-performance liquid chromatography with ultraviolet and fluorescence detection without additional sample cleanup. The procedure gave reliable values of vitamin A as well as of vitamin E in other food items such as infant formula, minced pork and beef meat, and low- and high-fat liver paste. The described method is faster and more automated than conventional methods based on liquid-liquid extraction, or SFE using off-line saponification, for vitamin A and E determination. Results obtained with the new method did not differ significantly from those obtained with the other two methods mentioned above.

Solubility of triazine pesticides in pure and modified subcritical water.

Solubility measurements in pure and modified water serve as a basis for optimizing the subcritical water extraction of target analytes such as food contaminants. The solvent strength of the water is affected by both the system's temperature and the amount and type of cosolvent modifier that is added to the water, which causes a reduction in the dielectric constant of water. In the present work, the solubilities of the triazine pesticides atrazine, cyanazine, and simazine were measured in pure and modified water at temperatures ranging from 50 to 125 degrees C and at a pressure of 50 atm. The solubility data were obtained using a static solubility apparatus with on-line liquid chromatographic (LC) detection. By increasing the temperature of the water, the solubilities of the triazine pesticides increased approximately 3-fold in pure water for each 25 degrees C temperature increment. Cyanazine was 5 times more soluble than atrazine and an order of magnitude more soluble than simazine at 100 degrees C. The solubility of atrazine was also measured in ambient and hot water modified with ethanol and urea. At 100 degrees C, the solubility of atrazine is doubled when the water is modified with urea, and is increased over an order of magnitude when ethanol is used as modifier. The data, therefore, indicate that adding a cosolvent to water in addition to increasing the system temperature increases the solubilities of triazine pesticides in subcritical water. It was further determined that the solutes do not thermally degrade or hydrolyze at the temperatures reported in this study.

Supercritical fluid extraction and chromatography for fat-soluble vitamin analysis.

Extraction and chromatographic separation of fat-soluble vitamins is a challenging task, due to the sensitivity of these compounds towards light, oxygen, heat and pH. In light of this, supercritical fluid extraction (SFE) and supercritical fluid chromatography (SFC) are attractive techniques as they function at considerably milder conditions than conventional solvent-based analytical techniques. Moreover, supercritical techniques consume much less amounts of organic solvents than conventional ones. This review gives a brief description of suitable supercritical media as well as basic theory on SFE and SFC processes. Furthermore, guidelines are provided for optimizing the important extraction and separation parameters to facilitate a successful method development. Finally, applications employing SFE and/or SFC for fat-soluble vitamin enrichment and final determination are reviewed.

Optimization of the extraction and fractionation of corn bran oil using analytical supercritical fluid instrumentation.

Supercritical fluid extraction (SFE) is combined with supercritical fluid chromatography (SFC) in an analytical mode to develop a system for fractionating and enriching high value ferulate-phytosterol esters (FPE) contained in corn bran oil. Corn bran is initially extracted with neat supercritical carbon dioxide (SC-CO2) at various pressures (13.8, 34.5, and 69 MPa) and temperatures (40, 60, and 80 degrees C) to see if the FPE can be enriched in the extracts. These initial studies show the greatest percentage of FPE could be extracted under two sets of conditions: 69 MPa at 80 degrees C and 34.5 MPa at 40 degrees C. Both sets of parameters yield an extract containing approximately 1.25% FPE. A stock supply of corn bran oil is then produced by scaled-up SFE at 34.5 MPa and 40 degrees C for subsequent chromatographic fractionation. The SFE-obtained corn bran oil is then applied to the head of a minichromatographic column containing an amino-propyl sorbent. SFC is than commenced using neat SC-CO2 at 69 MPa and 80 degrees C to remove the majority of the triglyceride-based oil. Pressure and temperature are then lowered to 34.5 MPa and 40 degrees C, respectively, and ethanol is added as a modifier. The modifier is added in an increasing stepwise gradient program, and fractions are collected at equal volume intervals. The resultant fractions are analyzed by analytical high-performance liquid chromatography with evaporative light-scattering detection and show that FPE could be enriched to a 14.5% (w) level.

Neural plasticity in the dynamics of human visual word recognition.

Repeated exposure to words leads to plastic changes in the nervous system throughout the lifespan, with the consequence that common words are processed more rapidly and accurately than rare words. Most behavior time measures correlate highly with the logarithm of a stimulus word's experiential frequency. Here, we demonstrate similar but earlier changes in the latency of a brain-generated evoked potential recorded over the left anterior scalp as individuals silently read sentences. We conclude that experience can speed the processing of some words by at least 50 ms within the first 335 ms of visual processing.

Selective extraction of pesticides from lipid-containing matrixes using supercritical binary gas mixtures.

When supercritical carbon dioxide is used for extraction of trace compounds from lipid-rich samples, the resulting extract can contain a substantial amount of lipid coextractive which interferes in the subsequent chromatographic analysis. In this case, a cleanup step, which is time-consuming, is required in order to remove or reduce the lipid content in the extract. In this study, we report on a new approach for the extraction of trace compounds which significantly reduces the quantity of lipid coextractives, thereby eliminating the need for a sample cleanup step. An autoclave high-pressure reactor equipped with a mechanical stirring device was used for mixing gases, such as carbon dioxide and nitrogen, to generate the desired fluid mixtures. The composition of the mixtures could be adjusted by two mass flow controllers prior to the autoclave mixing device. The generated carbon dioxide/nitrogen binary mixtures were then employed to facilitate supercritical fluid extraction (SFE) at high pressures and elevated temperatures. The pressurized CO(2)/nitrogen binary fluid mixture demonstrated sufficient solvation power for quantitative recoveries of trace fortified organophosphorus and incurred organochlorine pesticides from poultry fat while significantly reducing lipid solubility in the fluid. This allowed the development of a method that produced an extract with minimal lipid content that could be used directly for gas chromatographic analysis, thereby eliminating the need to clean-up the extract.

Event-related potentials elicited by spoken relative clauses.

Sentence-length event-related potential (ERP) waveforms were obtained from 23 scalp sites as 24 subjects listened to normally spoken sentences of various syntactic structures. The critical materials consisted of 36 sentences each containing one of two types of relative clauses that differ in processing difficulty, namely Subject Object (SO) and Subject Subject (SS) relative clauses. Sentence-length ERPs showed several differences in the slow scalp potentials elicited by SO and SS sentences that were similar in their temporal dynamics to those elicited by the same stimuli in a word-by-word reading experiment, although the effects in the two modalities have non-identical distributions. Just as for written sentences, there was a large, fronto-central negativity beginning at the linguistically defined "gap" in the SO sentences; this effect was largest for listeners with above-median comprehension rates and is hypothesized to index changes in on-line processing demands during comprehension.

Evaluation of the online immunoassay for propoxyphene: comparison to EMIT II and GC-MS.

A study was conducted to compare the clinical sensitivity of the OnLine and EMIT II assays for propoxyphene (PPX) use in human urine. A total of 5138 random clinical samples were evaluated by both OnLine and EMIT II. Samples that were positive for each immunoassay were confirmed for PPX and norpropoxyphene (NPPX) by gas chromatography-mass spectrometry (GC-MS). There were 14 samples that were identified positive by both immunoassays and confirmed positive by GC-MS. An additional six samples were positive by OnLine, negative by EMIT II, and confirmed positive by GC-MS. There was one unconfirmed positive sample identified by each immunoassay, and 5116 samples were identified as negative by both immunoassays. The increased sensitivity by OnLine can be attributed to the cross reactivity of the OnLine antibody, which is higher than the cross reactivity of the EMIT II antibody for NPPX (77% versus 7%, respectively). The high concentrations of NPPX, relative to those of PPX, found in all of the clinical samples suggest that laboratories that currently confirm for PPX should confirm for NPPX in order to obtain a better correlation between immunoassay results and GC-MS confirmations.