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PubMed2001

Analysis of aromatic aldehydes in brandy and wine by high-performance capillary electrophoresis.

A new method of analysis of vanillin, syringaldehyde, coniferaldehyde, and sinapaldehyde in brandy and wine by high-performance capillary electrophoresis is described. Electrophoretic mobility of these compounds is achieved by a borate buffer at pH 9.3. At this pH, the sensitivity of UV detection of these phenolic aldehydes also increases. UV absorptions at 348, 362, 404, and 422 nm were selected for monitoring vanillin, syringaldehyde, coniferaldehyde, and sinapaldehyde, respectively. This procedure was performed simultaneously during one run using a diode array detector. Samples of brandy or wine were analyzed directly without concentration, extraction, or any other preliminary treatment of the test sample. The limits of detection were found to be 0.275, 0.1425, 0.1475, and 0.1975 ppm for syringaldehyde, coniferaldehyde, sinapaldehyde, and vanillin, respectively, which is acceptable for analysis of both brandy and wine aged in oak barrels. The method has been shown to be linear in a range from 0.3 to 57 mg/L. Recoveries ranged between 99.9% and 107.7% for all of the compounds tested. Repeatability and reproducibility of the method were high. The relative standard deviation was consequently approximately 3% and also between 4.47% and 6.89% for all tested compounds. The method is useful for the identification of counterfeit brandy, which is easy to recognize by the absence of sinapaldehyde, syringaldehyde, and coniferaldehyde, which are not detectable in false brandy.

Alcoholic Beverages↗

PubMed2005

Latex-coated polymeric monolithic ion-exchange stationary phases. 1. Anion-exchange capillary electrochromatography and in-line sample preconcentration in capillary electrophoresis.

A sulfonated methacrylate monolithic polymer has been synthesized inside fused-silica capillaries of diameters 50-533-microm i.d. and coated with 65-nm-diameter fully functionalized quaternary ammonium latex particles (AS18, Dionex Corp.) to form an anion-exchange stationary phase. This stationary phase was used for ion-exchange capillary electrochromatography of inorganic anions in a 75-microm-i.d. capillary with Tris/perchlorate electrolyte and direct UV detection at 195 nm. Seven inorganic anions (bromide, nitrate, iodide, iodate, bromate, thiocyanate, chromate) could be separated over a period of 90 s, and the elution order indicated that both ion exchange and electrophoresis contributed to the separation mechanism. Separation efficiencies of up to 1.66 x 10(5) plates m(-1) were achieved, and the monoliths were stable under pressures of up to 62 MPa. Another latex-coated monolith in a 250-microm-i.d. capillary was used for in-line preconcentration by coupling it to a separation capillary in which the EOF had been reversed using a coating of either a cationic polymer or cationic latex particles. Several capillary volumes of sample were loaded onto the preconcentration monolith, and the analytes (inorganic anions) were then eluted from the monolith with a transient isotachophoretic gradient before being separated by electrophoresis in the separation capillary. Linear calibration curves were obtained for aqueous mixtures of bromide, nitrite, nitrate, and iodide. Recoveries of all analytes except iodide were reduced significantly when the sample matrix contained high levels of chloride. The preconcentration method was applied to the determination of iodide in open ocean water and provided a limit of detection of 75 pM (9.5 ng/L) calculated at a signal-to-noise ratio of 3. The relative standard deviation for migration time and peak area for iodide were 1.1 and 2.7%, respectively (n = 6). Iodide was eluted as an efficient peak, yielding a separation efficiency of 5.13 x 10(7) plates m(-1). This focusing was reproducible for repeated analyses of seawater.

Journal Article↗

PubMed2005

Equilibrium sampling through membranes of freely dissolved copper concentrations with selective hollow fiber membranes and the spectrophotometric detection of a metal stripping agent.

A sensitive spectrophotometric method for the determination of freely dissolved copper concentrations in aqueous samples after preconcentration with hollow fiber membrane extraction has been developed. The method is based on the equilibrium sampling through a selective membrane into an acceptor solution containing 4-(pyridyl-2-azo)resorcinol (PAR), which serves as stripping agent and metal indicator. Negligible extraction of interferences and equilibrium enrichment of copper allowed for selective spectrophotometric determination of the Cu-PAR complex. Some important extraction parameters such as acceptor composition, shaking, equilibrium time, and sample volume were studied. The optimized methodology showed good linearity in the range of 5-100 microg/L, an enrichment factor of 93, good repeatability and reproducibility (RSDs < 6%, n = 6), and a detection limit of 4 microg/L. The cationic metals Ni2+, C(2+, Cd2+, Fe3+, Pb2+, Zn2+, and Mn2+ were shown not to interfere with the measurement of Cu2+. Measurements on samples containing mixtures of various ligands and cations were in good agreement with theoretically calculated concentrations, and the method was also applied to environmental samples. The developed technique requires less labor and less sophisticated equipment than conventional methods typically based on atomic absorption spectrometry or ICP.

Journal Article↗

PubMed2006

Simultaneous quantitative analysis of metabolites using ion-pair liquid chromatography-electrospray ionization mass spectrometry.

We have developed an analytical method, consisting of ion-pair liquid chromatography coupled to electrospray ionization mass spectrometry (IP-LC-ESI-MS), for the simultaneous quantitative analysis of several key classes of polar metabolites, like nucleotides, coenzyme A esters, sugar nucleotides, and sugar bisphosphates. The use of the ion-pair agent hexylamine and optimization of the pH of the mobile phases were critical parameters in obtaining good retention and peak shapes of many of the above-mentioned polar and acidic metabolites that are impossible to analyze using standard reversed-phase LC/MS. Optimum conditions were found when using a gradient from 5 mM hexylamine in water (pH 6.3) to 90% methanol/10% 10 mM ammonium acetate (pH 8.5). The IP-LC-ESI-MS method was extensively validated by determining the linearity (R2 > 0.995), sensitivity (limit of detection 0.1-1 ng), repeatability, and reproducibility (relative standard deviation <10%). The IP-LC-ESI-MS method was shown to be a useful tool for microbial metabolomics, i.e., the comprehensive quantitative analysis of metabolites in extracts of microorganisms, and for the determination of the energy charge, i.e., the cellular energy status, as an overall quality measure for the sample workup and analytical protocols.

Amines↗

PubMed1997

Peptide separation in normal phase liquid chromatography.

A new method is established for separating peptides in normal phase liquid chromatography using TSK gel Amide-80, carbamoyl groups bonded to a silica gel matrix, and an acetonitrile-water solution containing 0.1% trifluoroacetic acid. Peptide retention time increased with acetonitrile concentration in the initial eluent. Hydrophilic peptides with no retention in a reversed phase column were retained and separated in the present method. Separation selectivities in the present and reversed phase methods differed significantly. Two-dimensional separation of protein digest using reversed and normal phases was conducted, taking advantage of the differences in selectivities. All peptides obtained from the digest could be separated completely. The present method is useful for separating peptide mixtures in conjunction with reversed phase liquid chromatography. Peptide recovery from the Amide-80 column exceeded 80%, as with the reversed phase column, and repeatability and reproducibility were satisfactory.

Amino Acid Sequence↗

PubMed1998

Determination of aspirin and salicylic acid in human plasma by column-switching liquid chromatography using on-line solid-phase extraction.

A column-switching liquid chromatographic method is described for the simultaneous determination of aspirin and salicylic acid in human plasma. Blood samples are taken into chilled tubes containing a fluoride anticoagulant, and the plasma is isolated by centrifugation. Following a simple acidification step, a 200 microL aliquot of the sample is injected directly onto the HPLC system. The C-18 extraction column is washed with acidified water for 2 min, after which time the compounds are removed by back-flushing directly onto the analytical column (C-8 Nucleosil, 5 microns, 250 mm x 4.6 mm). The flow rate through both columns is 1 mL/min, and the analytes are quantified by measurement of their UV absorbance at 225 nm. The mobile phase is a mixture of water-methanol-acetonitrile-orthophosphoric acid (650:200:150:1 v/v/v/v). The method is linear in the concentration ranges 0.10-5.00 micrograms/mL for aspirin and 0.25-15.00 micrograms/mL for salicylic acid. Both compounds have a limit of quantitation of 0.10 microgram/mL and a limit of detection of 0.04 microgram/mL. Extensive stability tests have been carried out, and validation studies reveal the method to be reproducible and repeatable. Excellent recoveries from plasma obviate the need for an internal standard. The procedure is easier to execute and requires less sample handling than methods currently described in the literature. It has been successfully applied to the investigation of the levels of aspirin and salicylic acid in a healthy, nonfasting volunteer following a 600 mg oral dose of aspirin.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2004

Stable room-temperature molecular negative differential resistance based on molecule-electrode interface chemistry.

We show reproducible, stable negative differential resistance (NDR) at room temperature in molecule-controlled, solvent-free devices, based on reversible changes in molecule-electrode interface properties. The active component is the cyclic disulfide end of a series of molecules adsorbed onto mercury. As this active component is reduced, the Hg-molecule contact is broken, and an insulating barrier at the molecule-electrode interface is formed. Therefore, the alignment of the molecular energy levels, relative to the Fermi levels of the electrodes, is changed. This effect results in a decrease in the current with voltage increase as the reduction process progresses, leading to the so-called NDR behavior. The effect is reproducible and repeatable over more than 50 scans without any reduction in the current. The stability of the system, which is in the "solid state" except for the Hg, is due to the molecular design where long alkyl chains keep the molecules aligned with respect to the Hg electrode, even when they are not bound to it any longer.

Journal Article↗

PubMed2000

Evaluation and validation of a commercial ELISA for diazinon in surface waters.

The performance of a commercially available microtiter plate ELISA kit for the determination of diazinon was evaluated for sensitivity, selectivity, intra-assay repeatability, accuracy, and matrix effects in fortified distilled water and filtered and unfiltered environmental surface water samples. Repeatability and reproducibility studies show that the kit satisfies current EPA criteria for the assessment of analytical methods. Mean recoveries from spiked samples averaged 80.3, 95.5, and 103.5% from distilled, unfiltered surface, and filtered surface waters, respectively. The experimentally determined method detection limit (MDL) for the commercial diazinon microtiter plate format (0.0159 microg L(-)(1)) was comparable to the least detectable dose (LDD) established by the manufacturer (0.022 microg L(-)(1)). Specificity studies indicate that the diazinon polyclonal antibody can readily distinguish the target compound from other structurally similar organophosphorus analogues, with the exception of diazoxon. Cross-reactivity with the oxon was approximately 29%, while reactivity with pirimiphos-methyl, pirimiphos-ethyl, and chlorpyrifos-ethyl was negligible. A slight matrix effect was discovered to be present in both filtered and unfiltered environmental water matrixes, but its effect on the immunoassays is insignificant within experimental error. For validation of the microtiter plate ELISA format, environmental surface and storm runoff water samples were collected, split, and analyzed directly by ELISA and by liquid-liquid extraction followed by GC (California State Department of Food and Agriculture method EM 46.0). Results of the two analytical methods were then compared statistically. A close correlation was found between methods for unspiked and untreated river water samples (r = 0.969) while a much less robust correlation was obtained for runoff waters (r = 0.728). Results from runoff waters exhibit a particularly high positive bias for the ELISA method relative to the GC method. Cross-reactivity of diazoxon and probably other unidentified cross-reacting components may be responsible for the exaggerated account of the target analyte in surface and runoff waters. While excellent for screening purposes, further study is required to elucidate and quantify the factors responsible for the consistent overestimation of ELISA results before the kit can be employed routinely for regulatory compliance monitoring.

Diazinon↗

PubMed2002

On-line HPLC detection of tocopherols and other antioxidants through the formation of a phosphomolybdenum complex.

An on-line method to detect and quantify antioxidant species in complex extracts has been developed as a combination of conventional HPLC separation and a postcolumn reaction with phosphomolybdenum reagent at acidic pH. Sample analytes were chromatographed by HPLC, and the postcolumn formation of a phosphate/Mo(V) complex was detected at 598 nm with an on-line absorbance detector. An optimized instrumental system was set up using pure alpha-tocopherol, and it was successfully tested with complex food extracts including lettuce, tomato, red pepper, and soybean seed, where several tocopherols and carotenoids were identified. A potential application of this detection method to quantitatively determine different antioxidants was considered, and a specific application to the determination of tocopherols was developed. The new method was characterized with respect to linearity interval, repeatability, and reproducibility, the quantitative results obtained were validated by comparison with a conventional HPLC method with fluorometric detection, and it was applied to the determination of tocopherols in different foods. The results suggest that the proposed on-line HPLC method can be a powerful instrument for the detection, purification, and characterization of natural antioxidants.

Antioxidants↗

PubMed2003

Application of the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation assay to a flow injection system for the evaluation of antioxidant activity of some pure compounds and beverages.

The 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS(*)(+)) assay was adapted to a flow injection (FI) system to obtain a sensitive and rapid technique for the monitoring of antioxidant activity of pure compounds and complex matrixes, such as beverages and food extracts. The FI system includes a HPLC pump that flows the mobile phase (a solution of ABTS(*)(+) in ethanol) through a 20 microL loop injector, a single bead string reactor filled with acid-washed silanized beads, a delay coil and a photodiode array UV-visible detector. The technique was very sensitive, with limits of detection and of quantification of 4.14 and 9.29 micromol of Trolox/L, respectively, and demonstrated high repeatability and reproducibility. The proposed technique was then applied to the evaluation of the antioxidant activity of some pure compounds, demonstrating good agreement with published data obtained by the original spectrophotometric ABTS(*)(+) assay. Finally, the total antioxidant activity of 10 beverages was determined by both the proposed and the original method. The values ranged from 0.09 mmol L(-)(1) for cola to 49.24 mmol L(-)(1) for espresso coffee and did not result significantly different from those obtained by the original spectrophotometric ABTS(*)(+) assay (Student's paired t-test: t = 1.4074, p = 0.1929). In conclusion, the proposed FI technique seems suitable for the direct, rapid and reliable monitoring of total antioxidant activity of pure compounds and beverages and, due to the ability to operate in continuous, it allows the analysis of about 30 samples h(-)(1) making the assay particularly suitable for large screening of total antioxidant activity in food samples.

Antioxidants↗

PubMed2006

Rapid determination of nonaromatic organic acids in honey by capillary zone electrophoresis with direct ultraviolet detection.

A rapid capillary zone electrophoresis (CZE) method with direct ultraviolet (UV) detection has been set up and developed to determine the most important nonaromatic organic acids in honey with a really simple treatment of the sample. The determination of oxalic, formic, malic, succinic, pyruvic, acetic, lactic, citric, and gluconic acids has been carried out in 4 min. The electrolyte composition was phosphate as the carrier buffer (7.5 mM NaH(2)PO(4) and 2.5 mM Na(2)HPO(4)), 2.5 mM tetradecyltrimethylammonium hydroxide (TTAOH) as electroosmotic flow modifier, and 0.24 mM CaCl(2) as selectivity modifier, with the pH adjusted at 6.40 constant value. The running voltage was -25 kV at a thermostated temperature of 25 degrees C. The injections were performed in hydrodynamic mode (30 s), and the detection mode was UV direct at 185 nm. Validation parameters of the method as detection and quantification limits, linearity, precision (repeatability and reproducibility), and recovery were also studied. The advantages related to the technique such as simplicity, short analysis times, and low consumption of chemicals as well as the good validation parameters obtained for this method permit it to be considered as adequate for routine analysis in honey.

Buffers↗

PubMed2006

Capillary zone electrophoresis method for the determination of inorganic anions and formic acid in honey.

A capillary zone electrophoresis method for the determination of inorganic anions and formic acid in honey samples was developed for the first time. The complete separation of chloride, nitrate, sulfate, phosphate, and formic acid was achieved with a simple electrolyte composed by 2 mM potassium dichromate as the carrier solution and background absorbance provider and 0.05 mM tetraethylenepentamine (TEPA) as electro-osmotic flow suppressor (pH 4.00). Injection was performed hydrostatically by elevating the sample at 10 cm for 10 s. The running voltage was -27 kV at 25 degrees C. Indirect UV absorption detection was achieved at 254 nm. The detection limit was in the range between 0.03 and 20 mg/kg, and the quantification limits ranged from 1.52 to 20.6 mg/kg. The calibration graphs were linear in the concentration range from the quantification limit to at least 2.5 g/kg for chloride, 0.25 g/kg for nitrate, 0.75 g/kg for sulfate, 1.50 g/kg for phosphate, and 0.75 g/kg for formic acid. Precision data in the honey samples analyzed showed repeatability and reproducibility relative standard deviations lower than 1.4 and 2.4% for migration time and lower than 1.8 and 4.3% for anion content, respectively. Recoveries of anions in honey samples analyzed ranged from 94.4 to 99.8%. Ten honey samples were analyzed to test the proposed method. Mean contents of 260.5, 3.93, 60.5, 139.4, and 209.3 mg/kg were found, respectively, for chloride, nitrate, sulfate, phosphate, and formic acid in analyzed honeys. These results agreed with literature data.

Anions↗

PubMed2002

Examination of ethanol responsive liver and brain specific gene expression, in the mouse strains with variable ethanol preferences, using cDNA expression arrays.

Strains of mice that differ in voluntary alcohol consumption (VAC) are valuable models for the identification of genes involved in the complex etiology of alcohol effects and alcoholism. These mice offer a novel approach to the identification of strain-specific ethanol responsive (SSER) genes in tissues directly involved in alcohol metabolism and preference. We assessed mRNA from the liver and brain from male mice representing C57BL/6J, BALB/c, A/J, and DBA/2J strains following ethanol treatment (chronic ethanol fed liquid diet for 14 days or acute i.p. injection at two doses; 4 g/kg or 8 g/kg), using an expression array containing 588 genes (Clontech #7741-1). The results have identified NADPH cytochrome P450 oxidoreductase, insulin-like growth factor binding protein-1, glutathione S-transferase Mu 1, and cathepsin L as ethanol responsive genes in the liver. Further, we have established that IkB-alpha and clusterin genes in the brain are ethanol responsive, but only at the lower dose of the ethanol challenge. Although a number of other genes showing subtle (<2X) differences across strains and treatment combinations were reproducible in repeated blots, they were not confirmed by still evolving independent technologies of gene specific mRNA quantitation. The results demonstrate that comparative expression studies are an efficient approach to discover interacting gene networks that underlie the etiology of complex phenotypes including response to alcohols.

Alcohol Drinking↗

PubMed2003

Hypotensive activity of ultralow doses of antibodies to factors involved in the regulation of vascular tone.

Hypotensive activity of ultralow doses of antibodies to some endogenous substances involved in the regulation of vascular tone was studied on NISAG rats with hereditary stress-induced arterial hypertension. It was found that antibodies to angiotensin II and its receptor in ultralow doses markedly reduced systolic blood pressure, which was reproducible after repeated treatment. The course of peroral treatment with antibodies to endothelin and endothelial NO synthase in ultralow doses did not decrease systolic blood pressure.

Angiotensin II↗

PubMed2003

Hypotensive effect of potentiated antibodies to angiotensin II and AT1 receptors.

Hypotensive activity of ultralow doses of antibodies to angiotensin II and its receptors was studied on adult NISAG rats with hereditary stress-induced arterial hypertension. Antibodies to C-terminal fragment of angiotensin II receptors produced the most pronounced hypotensive effect, which was reproducible after repeated administration. These antibodies decreased systolic blood pressure by 16.40 +/- 0.62 mm Hg. The most rapid hypotensive effect was produced by affinity purified antibodies to angiotensin II: 2 h after administration of these antibodies systolic blood pressure decreased by 12.80 +/- 5.49 mm Hg. Our results indicate that combination treatment with ultralow doses of antibodies to angiotensin II and its receptors hold much promise for the use in clinical practice.

Angiotensin II↗

PubMed2003

A microbial fuel cell with improved cathode reaction as a low biochemical oxygen demand sensor.

Mediator-less microbial fuel cells (MFC) enriched with oligotrophic microbes were optimized through enhancement of cathode reaction and lowering O2 diffusion into the anode compartment as a low BOD sensor. The optimization of the MFC has greatly improved the maximum current and coulomb yield. The oligotroph-type MFC could be used as a low BOD sensor with high operational stability, good repeatability and reproducibility.

Bacterial Physiological Phenomena↗

PubMed2000

Study of three complementary techniques for measuring cutaneous hydration in vivo in human subjects: NMR spectroscopy, transient thermal transfer and corneometry - application to xerotic skin and cosmetics.

BACKGROUND/AIMS: The aim of this study was to determine the capability and the analytical quality of three different in vivo, non-invasive, quantitative methods for measuring skin hydration: two innovative methods that have been used for more than eight years - nuclear magnetic resonance spectroscopy (NMR-S) and transient thermal transfer (TTT) - and the more widely used and conventional corneometry. METHODS: The work presented evaluated the capability and precision, as well as cutaneous exploration depths, of the three methods. Experiments were carried out in vivo following the hydration, in kinetic terms, induced by topic application of reference moisturizing products. Spatio-temporal efficacy of a lipolotion was also studied by the TTT METHOD: Cases of xerotic skin were studied with TTT and corneometry. RESULTS: The results obtained showed better repeatability and reproducibility with the TTT and NMR-S methods than with corneometry. NMR-S is one of the only direct hydration measurement methods. It measures skin hydration down to the outer dermis with high precision. It is indicated for products having an action down to the deep cutaneous layers. By changing thermal power parameters, the TTT method can determine hydration to the outer, middle or deep epidermal layers. It is, therefore, possible to track the penetration of products in various layers of the epidermis. The small size of the probe enables the hydration measurement of skin sites (lips, eyelids) that were not, up to now, measurable with the two other methods. Corneometric investigations are restricted to the surface of the horny layer; measurements are easy and rapid but influenced by the composition of products applied to the skin and their phases: aqueous, oily or ionic. The xerotic skin study highlights the importance of exploration in different layers of the epidermis, as dehydration concerns not only the upper layers of the epidermis but also the medial and deep layers. With the TTT method, it has been possible to highlight the penetration dynamics of a lipolotion with, initially, an increase in the hydration in the outer epidermis, followed 3 h later by a transfer from the outer to the middle epidermis. CONCLUSION: NMR-S, TTT and corneometry represent three possible ways to assess skin hydration. Because they explore different cutaneous depths, they are more complementary than competitive. Transient thermal transfer, although a semi-direct method, is a precise, informative, and innovative solution to evaluate skin hydration at different epidermal depths and sites.

Journal Article↗

PubMedDate not supplied

Growth induced by pulsatile infusion of an amidated fragment of human growth hormone releasing factor in normal and GHRF-deficient rats.

The discovery of human pancreatic growth hormone releasing factors (GHRFs) and subsequent characterization of human hypothalamic GHRF has led to studies on the role of these peptides in stimulating growth hormone (GH) release, and attempts to use GHRF peptides to increase growth rates in short children are already underway. However, there is no experimental evidence in animals that exogenous GHRF promotes growth in vivo. Although anaesthetized rats release GH reproducibly in response to GHRF injections, the responses in conscious male rats are much more variable, perhaps because of their highly episodic endogenous GH secretory pattern. In contrast, female rats secrete GH in a more continuous pattern and respond reproducibly to repeated injections of GHRF. We report here that it is possible to establish a 'male' type of GH secretory pattern in normal female rats by long-term pulsatile intravenous (i.v.) infusions of the active human GHRF fragment GHRF (1-29)NH2. We found that this treatment accelerates growth and increases pituitary GH content, whereas continuous infusions of this GHRF fragment at the same daily dose are ineffective. Pulsatile, but not continuous GHRF also stimulates growth in animals made GHRF-deficient by neonatal monosodium glutamate treatment. Thus exogenous GHRF will stimulate growth in both GHRF-deficient and normal animals provided it is administered in an appropriate pattern.

Animals↗