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PubMed2006

Abdominal magnetic resonance imaging at 3.0 T what is the ultimate gain in signal-to-noise ratio?

RATIONALE AND OBJECTIVES: The purpose of this study was to calculate the gain in signal-to-noise ratio (SNR) of four human abdominal tissues at 3.0 Tesla (T) compared with standard 1.5 T and to validate this calculation in vivo. MATERIALS AND METHODS: The expected gain in SNR at 3.0 T in the liver, pancreas, spleen, and kidney compared with standard 1.5 T was approximated theoretically for a T2-weighted HASTE (half-Fourier acquisition single-shot turbo spin-echo) and a T1-weighted gradient-echo in- and opposed-phase sequence. Fifteen healthy male subjects underwent abdominal MR imaging using a 1.5 T and 3.0 T scanner. Coronal T2-weighted HASTE images and axial T1-weighted gradient-echo in- and opposed-phase images were acquired using the sequence parameters optimized by the vendor. RESULTS: Except for opposed-phased imaging of pancreatic tissue, in vivo adjusted SNR values of all abdominal tissues were significantly higher at 3.0 T for all sequences (P < .05). The highest overall gain in SNR was achieved with the HASTE sequence ranging from 3.8-fold for renal imaging to 7.4-fold for hepatic imaging. The theoretical calculation of SNR gain was in good agreement with the experimentally measured gain in SNR for the HASTE and the in-phase sequence. CONCLUSION: High-field abdominal MR imaging at 3.0 T offers significantly higher SNR compared with standard 1.5 T MR imaging.

Abdomen↗

PubMed2005

Detection of dopamine in the pharmacy with a carbon nanotube paste electrode using voltammetry.

A simply prepared DNA immobilized on a carbon nanotube paste electrode (CNTPE) was utilized to monitor dopamine ion concentration using the cyclic voltammetry (CV) and square-wave (SW) stripping voltammetry methods. The optimum analytical conditions were sought. The result obtained was a very low detection limit compared to other common voltammetry methods. The optimal parameters were found to be as follows: 3.5 pH, 0.48 V SW amplitude, 71 Hz frequency, 5 s accumulation time, 0.01 V increment potential, and -1.3 V (anodic-*-) and 1.2 V (cathodic-o-) accumulation potentials. Given these conditions, the linear working range was observed to be within 0.01-0.11 microg L(-1) (SW anodic and CV). The analytical detection limit was determined to be SW anodic and CV: 4.0 microg L(-1) (2.1 x 10(-11) mol L(-1)) dopamin, and the relative standard deviation at the dopamine concentration of SW anodic 0.05 microg L(-1) was 0.02% (n=15) at the optimum conditions.

Absorption↗

PubMed2006

Effect of extraction parameters on the chemical structure and gel properties of kappa/iota-hybrid carrageenans obtained from Mastocarpus stellatus.

Extraction parameters (temperature, pH, duration) and alkaline pre-treatment duration have been systematically varied in the aim of exploring their impact on both chemical structure and gelling properties of carrageenan biopolymers obtained from Mastocarpus stellatus seaweeds, collected on the Northern coast of Portugal. Increasing the alkaline pre-treatment duration PT leads to kappa/iota-hybrid carrageenans containing less sulphate groups and biological precursor monomers. As a result, gel properties in the presence of KCl are improved as demonstrated by the increase in the Young's modulus with parameter PT. Increasing the extraction duration t ameliorates the biopolymer yield with no significant change in the complex kappa/iota-hybrid carrageenan chemical structure. However, smaller molecular weights are obtained and gel properties are seen to be negatively affected. Extraction temperature and pH have dramatic effects on the biopolymer gel strength, and a set of extraction parameters optimized with respect to extraction yield and gel properties is reported. In addition, kappa/iota-hybrid carrageenans obtained throughout this study exhibit a wide range of gel strengths in KCl, and allow us to present correlations between gel thermal properties and the kappa/iota-hybrid carrageenans chemical structure.

Carbohydrate Conformation↗

PubMed2005

Production of cellulase by Trichoderma reesei from dairy manure.

Cellulase production by the fungi Trichoderma reesei was studied using dairy manure as a substrate. Data showed that T. reesei RUT-C30 had higher cellulase production than T. reesei QM 9414 and that a homogenized manure, treated by a blender to reduce fiber size, led to higher cellulase production. The cellulase production was further optimized by growing T. reesei RUT-C30 on homogenized manure. The effects of manure concentration, pH, and temperature on cellulase production were investigated with optimal parameter values determined to be 10 g/l manure (dry basis), 25.5 degrees C, and pH 5.7, respectively. Elimination of CaCl2, MgSO4, nitrogen sources (NH4+ and urea) and trace elements (Fe2+, Zn2+, Co2+ and Mn2+) from the original salt solution had no negative influence on the cellulase production, while phosphate elimination did reduce cellulase production. Based on above results, the final medium composition was simplified with manure additives being KH2PO4, tween-80 and CoCl2 only. Using this medium composition and a reaction time of 6-8 days, a maximum cellulase production activity of 1.74 IU/ml of filter paper activity, 12.22 IU/ml of CMCase activity, and 0.0978 IU/ml of beta-glucosidase was obtained. This filter paper activity is the highest ever reported in cellulase production from agricultural wastes.

Animals↗

PubMed2005

Optimization of anaerobically digested distillery molasses spent wash decolorization using soil as inoculum in the absence of additional carbon and nitrogen source.

The aim of this study was to achieve maximum decolorization of molasses spent wash (MSW) in absence of any additional carbon or nitrogen source using soil as inoculum. Soil samples were collected from the MSW disposal site. Colored soil samples exhibited higher pH, sugar and protein as compare to less colored samples. A decolorization of 69% was obtained using 10% (w/v) soil and 12.5% (v/v) MSW after 7 days incubation. Optimized parameters including days--6 days, pH--6, MSW--12.5% and soil concentration--40%, were obtained for maximum decolorization. A decolorization of 81% was achieved using 10% soil and 12.5% MSW after 18 days incubation in absence of any media supplement. Nearly 12% reduction in decolorization activity of the soil sample was observed over a period of 12 months when stored at 6 degrees C. It could be concluded that the decolorization of MSW might be achieved using soil as inoculum without addition of chemical amendments.

Bacteria, Anaerobic↗

PubMed2006

Electrochemical genosensors for biomedical applications based on gold nanoparticles.

Two gold nanoparticles-based genomagnetic sensors designs for detection of DNA hybridization are described. Both assays are based on a magnetically induced direct electrochemical detection of gold tags on magnetic graphite-epoxy composite electrodes. The first design is a two strands assay format that consists of the hybridization between a capture DNA strand which is linked with paramagnetic beads and another DNA strand related to BRCA1 breast cancer gene used as a target which is coupled with streptavidin-gold nanoparticles. The second genomagnetic sensor design is a sandwich assay format with more application possibilities. A cystic fibrosis related DNA strand is used as a target and sandwiched between two complementary DNA probes: the first one linked with paramagnetic beads and a second one modified with gold nanoparticles via biotin-streptavidin complexation reactions. The electrochemical detection of gold nanoparticles by differential pulse voltammetry was performed in both cases. The developed genomagnetic sensors provide a reliable discrimination against noncomplementary DNA as well against one and three-base mismatches. Optimization parameters affecting the hybridization and analytical performance of the developed genosensors are shown for genomagnetic assays of DNA sequences related with the breast cancer and cystic fibrosis genes.

Biosensing Techniques↗

PubMed2006

Amperometric and impedimetric characterization of a glutamate biosensor based on Nafion and a methyl viologen modified glassy carbon electrode.

An electrochemical biosensor based on a glassy carbon (GC) electrode chemically modified with the perfluorinated cation-exchange polymer Nafion and methyl viologen (MV) is described. The enzyme was immobilized by cross-linking with glutaraldehyde in the presence of bovine serum albumin (BSA), methyl viologen and Nafion. Operating variables such as the enzyme/BSA ratio, cross-linking time in glutaraldehyde vapor, methyl viologen and Nafion percentages were investigated with regard to their influence on the biosensor sensitivity by using glucose oxidase as the enzyme model due to its high stability and low cost. The glutamate biosensor was elaborated by using optimized parameters and its electrochemical properties were investigated by cyclic voltammetry, amperometry and by electrochemical impedance spectroscopy. The glutamate biosensor shows a detection limit of 20 microM and a linear range extended to 0.75 mM. Its selectivity was tested with 15 different amino acids, each with a concentration of 20 microM, 25 microM acetaminophen, 20 microM uric acid and 200 microM ascorbic acid. No amperometric response was observed for the interfering species. This good selectivity allows glutamate detection in biological media without previous separation of the analyte.

Biosensing Techniques↗

PubMed2004

The role of ferrous ion in Fenton and photo-Fenton processes for the degradation of phenol.

The efficiency of different Fenton-related oxidative processes such as Fenton, solar-Fenton and UV-Fenton were examined using phenol as a model compound in simulated and industrial wastewater. A batch study was conducted to optimize parameters like pH, hydrogen peroxide concentration and ferrous ion concentration governing the Fenton process. At optimum conditions, different Fenton-related processes were compared for the degradation of phenol. Increased degradation and mineralisation efficiency were observed in photo-Fenton processes as compared to conventional Fenton process. The maximum mineralising efficiency for phenol with Fenton, solar and UV-Fenton processes were 41%, 96% and 97% respectively. In Fenton process, carboxylic acids like acetic acid and oxalic acid were formed as end products during the degradation of phenol while in photo-Fenton processes, both these ions were identified during the early stages of phenol degradation and were oxidized almost completely at 120 min of the reaction time. In photo-Fenton processes (solar and UV light) complete degradation were observed with 0.4 mM of Fe2+ catalyst as compared to 0.8 mM of Fe2+ in conventional Fenton process. In Fenton and solar-Fenton processes, an iron reusability study was performed to minimize the amount of iron used in treatment process. The efficacy of Fenton and solar-Fenton processes was applied to effluent from phenol resin-manufacturing unit for the removal and mineralisation of phenol.

Catalysis↗

PubMed2004

Rapid analysis of nucleotide-activated sugars by high-performance liquid chromatography coupled with diode-array detection, electrospray ionization mass spectrometry and nuclear magnetic resonance.

A generally applicable method for HPLC analysis of sugar nucleotides was established. Separation was achieved using ion-pair chromatography on a reversed-phase column. Ion-pair reagents were selected and various parameters optimized with respect to separation of 11 of the most important sugar nucleotides and compatibility with on-line detection by electrospray ionization MS and NMR. The method was applied to the on-line analysis of the GDP-D-mannose-4,6-dehydratase (Gmd) and GDP-4-keto-6-deoxy-D-mannose reductase (Rmd) catalyzed conversion of GDP-D-mannose to GDP-D-rhamnose. By LC-NMR, the intermediate product of the reaction was shown to be a mixture of GDP-4-keto-6-deoxy-D-mannose and GDP-3-keto-6-deoxy-D-mannose. Nucleotide co-factors of enzymatic reactions such as ATP and NADH did not interfere with the analysis of nucleotide-activated sugars.

Carbohydrates↗

PubMed2004

Development of an accelerated low-pH reversed-phase liquid chromatography column stability test.

The important experimental design criteria for an accelerated low-pH RPLC column stability test are discussed. The influence of method variables on the amount and rate of retention-loss and the final optimized parameters for the accelerated low-pH RPLC stability test are presented. The retention-loss curves for selected C8 and C18 stationary phases are compared. These studies indicate that ligand chain length, functionality and bonding density play an important role in determining the low-pH stability of a stationary phase. Additionally, elemental analysis data are used to infer the mechanism responsible for the observed retention-loss under low-pH conditions.

Chromatography, High Pressure Liquid↗

PubMed2005

Development of headspace solid-phase microextraction-gas chromatography method for the determination of solvent residues in edible oils and pharmaceuticals.

The application of headspace solid-phase microextraction for isolation and enrichment of solvent residues from oils and pharmaceuticals is discussed. The optimal parameters for isolation and preconcentration of common process solvents (hexane, benzene, toluene and selected chloroderivatives of hydrocarbons) were established. Four fiber types (100 microm polydimethylsiloxane (PDMS), 75 microm Carboxen-PDMS, 65 microm PDMS-divinylbenzene and 85 microm polyacrylate) were evaluated to choose the most efficient coating, able to absorb the greatest amount of analytes. GC-flame ionization detection (FID) and GC-electron-capture detection systems were used for quantitative and qualitative analysis, adequately to the appropriate group of the analytes. For all compounds the limit of detection (LOD), linearity, dynamic range, repeatability and intermediate precision were estimated.

Chromatography, Gas↗

PubMed2005

Comprehensive two-dimensional gas chromatography coupled to a rapid-scanning quadrupole mass spectrometer: principles and applications.

The principles, practicability and potential of comprehensive two-dimensional (2D) gas chromatography coupled to a rapid-scanning quadrupole mass spectrometer (GC x GC-qMS) for the analysis of complex flavour mixtures in food, allergens in fragrances and polychlorinated biphenyls (PCBs) were studied. With a scan speed of 10,000 amu/s, monitoring over a mass range of up to 200 atomic mass unit (amu) can be achieved at an acquisition frequency of 33 Hz. Extending this mass range and/or increasing the data acquisition frequency results in a loss of spectral quality. Optimal parameter settings allow, next to unambiguous identification/confirmation of target compounds on the basis of high-quality mass spectra, fully satisfactory quantification (three to four modulations per peak) with linear calibration plots and detection limits in the low-pg level. The potential of time-scheduled data acquisition to increase the effective mass range within one GC x GC run was also explored. The analyses, with baseline separation of the flavours, allergens and PCB target compounds, took less than 30 min.

Allergens↗

PubMed2005

Investigation of the extraction behavior of the main monoglutamate folates from spinach by liquid chromatography-electrospray ionization tandem mass spectrometry.

An LC-MS/MS method has been developed for the determination of main monoglutamate folates in spinach with folic acid as an internal standard. A sample preparation with ultrafiltration (molecular weight cut-off membrane, 5 kDa) was followed by a chromatographic run of 14.2 min, rendering the method very simple and fast. The LODs in diluted spinach matrix were 0.02, 0.09, 0.05 and 0.03 ng/mL (0.037, 0.17, 0.092 and 0.055 microg/100 g calculated according to the fresh weight of spinach) for 5-methyltetrahydrofolate, tetrahydrofolate, 5-formyltetrahydrofolate, and 10-formylfolic acid, respectively. Using this method, the extraction behaviour of the main naturally occurring monoglutamate folates has been investigated in detail. It is found that 10 min of heating at 100 degrees C, incubation with rat serum at 37 degrees C (0.05 M phosphate buffer, pH = 6.5) for 4 h and the ratio of 10 (volume of extraction buffer versus the weight of sample, mL/g) are the optimal parameters for folate extraction from spinach. The final quantitative result of the individual folates in spinach is highly influenced by the pH (from 2.9 to 8.6) of the extraction buffer.

Antioxidants↗

PubMed2005

Identification of Africanized honeybees.

Gas chromatography and pattern recognition methods were used to develop a potential method for differentiating European honeybees from Africanized honeybees. The test data consisted of 237 gas chromatograms of hydrocarbon extracts obtained from the wax glands, cuticle, and exocrine glands of European and Africanized honeybees. Each gas chromatogram contained 65 peaks corresponding to a set of standardized retention time windows. A genetic algorithm (GA) for pattern recognition was used to identify features in the gas chromatograms characteristic of the genotype. The pattern recognition GA searched for features in the chromatograms that optimized the separation of the European and Africanized honeybees in a plot of the two or three largest principal components of the data. Because the largest principal components capture the bulk of the variance in the data, the peaks identified by the pattern recognition GA primarily contained information about differences between gas chromatograms of European and Africanized honeybees. The principal component analysis routine embedded in the fitness function of the pattern recognition GA acted as an information filter, significantly reducing the size of the search space since it restricted the search to feature sets whose principal component plots showed clustering on the basis of the bees' genotype. In addition, the algorithm focused on those classes and/or samples that were difficult to classify as it trained using a form of boosting. Samples that consistently classify correctly are not as heavily weighted as samples that are difficult to classify. Over time, the algorithm learns its optimal parameters in a manner similar to a neural network. The pattern recognition GA integrates aspects of artificial intelligence and evolutionary computations to yield a "smart" one-pass procedure for feature selection and classification.

Animals↗

PubMed2005

The application of macroporous resins in the separation of licorice flavonoids and glycyrrhizic acid.

Glycyrrhizic acid (GA) and licorice flavonoids (LF) are the two classes of bioactive components in licorice with known pharmacological effects. But long-term excessive intake of GA may cause sodium retention and hypertension. In this study, the performance and adsorption characteristics of four widely used macroporous resins for the separation of deglycyrrhizinated, flavonoids enriched licorice has been critically evaluated. The sorption and desorption properties of LF and GA on macroporous resins including XDA-1, LSA-10, D101 and LSA-20 have been compared. The adsorption capacity was found to depend strongly on the pH of the feed solution. XDA-1 offers much higher adsorption capacity for GA and LF than other resins, and its adsorption data fit the best to the Freundlich isotherm. XDA-1 also shows much higher adsorption affinity towards LF than that of GA based on calculated results from the measured adsorption isotherms. Dynamic adsorption and desorption experiments have been carried out on a XDA-1 resin packed column to obtain optimal parameters for separating GA and LF. An enriched LF extract (about 21.9% purity) free of GA, and an enriched GA extract with 66% purity can be separated from crude licorice extract in one run.

Adsorption↗

PubMed2005

Sample preconcentration with chemical derivatization in capillary electrophoresis. Capillary as preconcentrator, microreactor and chiral selector for high-throughput metabolite screening.

New strategies for integrating sample pretreatment with chemical analyses under a single format is required for rapid, sensitive and enantioselective analyses of low abundance metabolites in complex biological samples. Capillary electrophoresis (CE) offers a unique environment for controlling analyte/reagent band dispersion and electromigration properties using discontinuous electrolyte systems. Recent work in our laboratory towards developing a high-throughput CE platform for low abundance metabolites via on-line sample preconcentration with chemical derivatization (SPCD) is primarily examined in this review, as there have been surprisingly only a few strategies reported in the literature to date. In-capillary sample preconcentration serves to enhance concentration sensitivity via electrokinetic focusing of long sample injection volumes for lower detection limits, whereas chemical derivatization by zone passing is used to expand detectability and selectivity, notably for enantiomeric resolution of metabolites lacking intrinsic chromophores using nanolitre volumes of reagent. Together, on-line SPCD-CE can provide over a 100-fold improvement in concentration sensitivity, shorter total analysis times, reduced sample handling and improved reliability for a variety of amino acid and amino sugar metabolites, which is also amenable to automated high-throughput screening. This review will highlight basic method development and optimization parameters relevant to SPCD-CE, including applications to bacterial metabolite flux and biomarker analyses. Insight into the mechanism of analyte focusing and labeling by SPCD-CE is also discussed, as well as future directions for continued research.

Amino Acids↗

PubMed2006

Atmospheric pressure photoionization mass spectrometry for analysis of fatty acid and acylglycerol lipids.

In this work, we optimize parameters and conditions for analysis of fatty acid ester and acylglycerol lipids by atmospheric pressure photoionization-mass spectrometry (APPI-MS). The investigated parameters include atmospheric pressure chemical ionization (APCI) nebulizer/vaporizer physical orientation and APPI lamp face position, solvent selections, mobile phase compositions and flow rates, cone voltages and probe temperatures. APPI sensitivity is found to be highly dependent on mobile phase compositions. Normal phase solvents offer much higher sensitivity and better peak shape than reversed phase for nonpolar lipids. Hexane and isooctane are found to be two solvents generating highest S/N for eicosapentaenoic acid (EPA) methyl ester. The effects of mobile phase flow rates on sensitivity are found to be target analytes and target ions specific. However, the flow rate changes do not significantly affect the sensitivity of three out of four tested analytes under normal phase conditions over tested flow rates of 50-500muL/min. Cone voltage is found to be one of key parameters affecting sensitivity. Optimum probe temperature is found to be more dependent on mobile phase compositions than on the specific target analytes. Aqueous reversed-phase mobile phase requires higher probe temperature than normal phase for better sensitivity. More volatile mobile phase solvents require lower probe temperature for analyte desolvation. APPI offers four to five decades of linear ranges under normal phase condition. Full scan mass spectra of individual lipid standards, custom lipid mixtures and natural fish oil show that APPI spectra are clean and very easy to interpret. APPI also gives stable, reproducible peak responses with good peak shape. Limits of detection (LODs) by FIA (S/N=3) are estimated to be 12pg for EPA methyl ester and monoarachidin, 19pg for diarachidin and 7pg for trielaidin. LODs on-column are estimated to be 94pg for EPA methyl ester, 90pg for monoarachidin and diarachidin and 24pg for trielaidin.

Atmospheric Pressure↗

PubMed2007

Rapid purification and scale-up of honokiol and magnolol using high-capacity high-speed counter-current chromatography.

In this paper, a rapid separation approach has been developed using high-capacity high-speed counter-current chromatography (high-capacity HSCCC) to isolate and purify honokiol and magnolol, which are the main bioactive constituents from Houpu. The optimization of the solvent selection process, sample loading volume and flow rate is systematically studied using analytical high-capacity HSCCC. The optimized parameters obtained rapidly at analytical scale were used for a 1000 x scale-up preparative run using pilot scale high-capacity HSCCC in a MAXI-DE centrifuge. A crude sample of 43 g was successfully separated and the fractions were analysed by high-performance liquid chromatography (HPLC). This large scale preparative single step run yielded 16.9 and 19.4 g of honokiol and magnolol with purities of 98.6 and 99.9%, in only 20 min. This is the first time that high-performance counter-current chromatography has been used to purify multiple gram grade bioactive compounds in less than 1h and at such high concentrations of final products (10.8 g/l for magnolol and 7.0 g/l for honokiol).

Biphenyl Compounds↗