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PubMedDate not supplied

Determination of ochratoxin A in green coffee by immunoaffinity column cleanup and liquid chomatography: collaborative study.

A collaborative study was conducted to evaluate a method using immunoaffinity column cleanup with liquid chromatography (LC) for the determination of ochratoxin A (OTA) in green coffee at levels that could be included in possible future regulations of the European Union. The test portion was extracted with methanol-3% aqueous sodium hydrogen carbonate solution (50 + 50, v/v). The extract was filtered, and the filtrate was diluted with phosphate-buffered saline and applied to an immunoaffinity column containing antibodies specific for OTA. After washing, the toxin was eluted from the column with methanol and quantified by LC with fluorescence detection. Pairs of 4 homogeneous noncontaminated and naturally contaminated materials (mean levels of < 0.12, 2.44, 5.15, and 13.46 ng/g) and blank samples (< 0.12 ng/g) for spiking were sent to 20 participant laboratories from 8 countries. The materials were analyzed according to the method description and all difficulties encountered in the analysis were reported. Statistical analysis was carried out according to the Harmonized Protocol of the International Union of Pure and Applied Chemistry. The relative standard deviation for repeatability (RSDr) ranged from 7.42 to 20.94%, and the relative standard deviation for reproducibility (RSDR) ranged from 16.34 to 29.17%. The method showed acceptable within-laboratory and between-laboratories precision for green coffee materials, as evidenced by HorRat values of < or = 0.85, at the studied range, for spiked and naturally contaminated materials. The mean recovery was 92.8% for green coffee material spiked with OTA at a level of 4.82 ng/g.

Buffers↗
PubMedDate not supplied

Evolution of an open-access quantitative bioanalytical mass spectrometry service in a drug discovery environment.

Increased demand for assays for compounds at the early stages of drug discovery within the pharmaceutical industry has led to the need for open-access mass spectrometry systems for performing quantitative analysis in a variety of biological matrices. The open-access mass spectrometers described here are LC/MS/MS systems operated in 'multiple reaction monitoring' (MRM) mode to obtain the sensitivity and specificity required to quantitate low levels of pharmaceutical compounds in an excess of biological matrix. Instigation of these open-access systems has resulted in mass spectrometers becoming the detectors of choice for non-expert users, drastically reducing analytical method development time and allowing drug discovery scientists to concentrate on their core expertise of pharmacokinetics and drug metabolism. Setting up an open-access facility that effectively allows a user with minimal mass spectral knowledge to exploit the MS/MS capability of triple quadrupole mass spectrometers presents a significantly different challenge from setting up qualitative single stage mass spectrometry systems. Evolution of quantitative open access mass spectrometry within a pharmaceutical drug metabolism and pharmacokinetics group, from its beginnings as a single generic system to a series of specialist fully integrated walk-up facilities, is described.

Automation↗
PubMedDate not supplied

Determination of Mirex in human blood serum containing polychlorinated biphenyls by using packed column gas chromatography.

An analytical method has been developed that uses electron capture/gas-liquid chromatography to determine Mirex in serum containing polychlorinated biphenyls (PCBs) (Aroclor 1260). With this method, 0.2 ppb Mirex can be determined in 4 mL serum that also contains 10 ppb PCBs. The method provides approximately 70% recovery of Mirex at 1.0 and 3.5 ppb. The coefficients of variation are 4.5 and 4.6% at 1.0 and 3.5 ppb, respectively. In a cooperative study with the Ohio Department of Health, the Centers for Disease Control used this method to determine the extent of exposure of Salem, OH, residents to Mirex. Confirmation of Mirex was obtained by using high resolution gas chromatography and high resolution mass spectrometry.

Chromatography, Gas↗
PubMed2005

Prospective budgeting for home care: making titration work.

OBJECTIVE: To provide a model for prospective budgeting for home care that is plausible, coherent, flexible, and sufficiently tractable that it can serve as a template for practical decision making and to clarify what would be the data requirements and statistical framework to calibrate the model. METHODS: Methods used are standard risk-neutral expected value theory, cost benefit analysis, and the conditional logistic probability model. RESULTS: A simple but effective prospective budgeting model that provides analytic scaffolding for a practical decision support system for home care case managers, consultants, and program evaluators that can improve program equity, efficiency, and effectiveness. DISCUSSION: The author criticizes the well-known Titration Budgeting Model of Weissert, Chernew, and Hirth in terms of its logical and operational problems but then goes on to develop a framework within which the goals of the titration model can be met and home care resources can be more efficiently allocated.

Aged↗
PubMed1982

Brain endo-oligopeptidase B: inactivation of LH-RH by hydrolysis of the Pro9-Gly-NH2(10) peptide bond.

1. The site of hydrolysis of rabbit brain endo-oligopeptidase B acting on luteinizing hormone-releasing hormone (LH-RH) was determined by isolating the products by chromatography on Aminex A-5 resin developed with pyridine-acetic acid buffer. The products [des-Gly-NH2(10)]-LH-RH, glycinamide and unhydrolyzed LH-RH were identified and shown to be homogeneous by amino acid analysis and high-voltage paper electrophoresis at pH 2.1 and 3.5 and recovered in yields of 58, 65 and 23%, respectively. 2. A sensitive analytical method for the measurement of 4-40 nmoles of glycinamide with an automatic amino acid analyzer was described. Aminex A-5 resin (0.90 x 15 cm) was eluted with sodium citrate buffer, pH 3.25 (0.2 N Na+) at 32 degrees C and ninhydrin was used for detection. 3. The data show that endo-oligopeptidase B acts as a post-proline cleaving enzyme that inactivates LH-RH by hydrolysis of the Pro9-Gly-NH2(10) peptide bond. The enzyme may participate in the metabolism of LH-RH in the central nervous system.

Animals↗
PubMed1986

Simultaneous analysis of antipyrine and lorazepam by high-performance liquid chromatography.

A novel analytical methodology was developed for simultaneous high-performance liquid chromatographic quantitation of antipyrine and lorazepam in biological fluids using phenacetin and flunitrazepam as internal standards, respectively. A gradient solvent system was used to achieve specificity and sensitivity for each of the compounds in biological fluids. The between-run coefficients of variation for replicate analysis of antipyrine and lorazepam in identical plasma samples were 9.4 and 6.4% at 60 micrograms/ml and 5.5 micrograms/ml, respectively, for antipyrine, and 9.1 and 9.9% at 110 ng/ml and 10.5 ng/ml, respectively, for lorazepam. Accuracy ranged from 99.7 to 101.4% at concentrations of 8, 45 and 105 micrograms/ml for antipyrine and from 94.8 to 95.8% at concentrations of 12, 55 and 125 ng/ml for lorazepam. This method requires only one organic extraction procedure for all four compounds, allows quantitation of these two drugs in samples also containing indocyanine green, and sample throughput following extraction is totally automated.

Antipyrine↗
PubMed2000

Multiplexed particle-based flow cytometric assays.

Several methods have been developed to quantify soluble analytes in biological fluids and tissue culture samples, including bioassays, ELISA, RPA and PCR. However, each of these techniques possesses one or more significant limitations; ELISA will only measure one analyte as a time; PCR does not detect native protein. The recent development of particle-based flow cytometric assays has raised hopes that many of these limitations can be overcome. The technology utilizes microspheres as the solid support for a conventional immunoassay, affinity assay or DNA hybridization assay which are subsequently analyzed on a flow cytometer. Several multiplexed bead systems are currently marketed by different vendors. We have used the Luminex FlowMetrix system which consists of 64 different bead sets manufactured with uniform, distinct proportions of red and orange fluorescent dyes (detected by FL2/FL3 on a FACScan). Each bead set forms the basis of an individual assay using a green fluorescent reporter dye (FL1). This system facilitates the development of multiplexed assays that simultaneously measure many different analytes in a small sample volume. They can also be developed into rapid, 'no wash' assays that can be completed in <2 h. This review traces the historical association between microspheres and flow cytometry, the development and use of particle-based flow cytometric assays, how they compare with current assays and potential future developments of this very exciting technology.

Cytokines↗
PubMed2005

Hilbert space inverse wave imaging in a planar multilayer environment.

Most diffraction tomography (DT) algorithms use a homogeneous Green function (GF) regardless of the medium being imaged. This choice is usually motivated by practical considerations: analytic inversions in standard geometries (Cartesian, spherical, etc.) are significantly simplified by the use of a homogeneous GF, estimating a nonhomogeneous GF can be very difficult, as can incorporating a nonhomogeneous GF into standard DT algorithms. Devaney has circumvented these issues by developing a purely numerical DT inversion algorithm [A. J. Devaney and M. Dennison, Inverse Probl. 19, 855-870 (2003)] that is independent of measurement system geometry, number of frequencies used in the reconstruction, and GF. A planar multilayer GF has been developed for use in Devaney's "Hilbert space" algorithm and used in a proof-of-principle nondestructive evaluation (NDE) experiment to image noninvasively a flaw in an aluminum/copper planar multilayer medium using data collected from an ultrasonic measurement system. The data were collected in a multistatic method with no beamforming: all focusing through the multilayer was performed mathematically "after-the-fact," that is, after the data were collected.

Acoustics↗
PubMed1981

A semi-automated technique for assessing the microdistribution of 239 Pu deposited in bone.

A semi-automated analytical procedure is described for the localisation of 239 Pu in bone. The method is based on the use of a Quantimet 720B Image Analyser for the analysis of neutron-induced autoradiographs, and may be applied to most tissues with fissionable radionuclides. Compared with former methods the present technique offers improvements in accuracy and a considerable saving on time and manpower. These savings arise mainly from the ability of the Quantimet to be used for the automatic detection of the fission-fragment tracks and to operate directly on the neutron-induced autoradiograph without recourse to photography. Results are presented for the distribution of 239 Pu in the ilia of CBA mice at 24 h post-injection.

Animals↗
PubMed1993

Staphylococcus intermedius: current knowledge on a pathogen of veterinary importance.

It has been 16 years since the identification of S. intermedius as a new species. Numerous investigations using cell wall and DNA analytic methods have now clearly demonstrated significant differences to warrant the creation of this new species. However, studies investigating virulence factors associated with S. intermedius have not uncovered evidence that differentiates virulent from non-virulent isolates. Therefore, at the present time, it is difficult for veterinary clinicians and microbiologists to determine the clinical significance of many S. intermedius isolates. Host-bacterial interactions and the hosts' immune status appear to be the factors most crucial in determining the outcome of infections, not the virulence of the organism. Continued research in the virulence factor field will hopefully lead to a better understanding on how we can differentiate virulent from nonvirulent isolates of S. intermedius.

Animals↗
PubMed2000

Separation and identification of twelve catechins in tea using liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry.

A method has been developed for the direct microscale determination of 12 catechins in green and black tea infusions. The method is based on liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (LC/APCI-MS). Standard catechin mixtures and tea infusions were analyzed by LC/APCI-MS with detection of protonated molecular ions and characteristic fragment ions for each compound. The identities of eight major catechins and caffeine in tea were established based on LC retention times and simultaneously recorded mass spectra. In addition, monitoring of the catechin-specific retro Diels-Alder fragment ion at m/z 139 throughout the chromatogram provided a unique fingerprint for catechin content in the samples that led to the identification of four minor chemically modified catechin derivatives in the infusions. This report is the first to describe the comprehensive determination of all 12 reported catechins in a single analysis. The utility of LC/APCI-MS for providing routine separation and identification of catechins at femtomole to low-picomole levels without extraction or sample pretreatment, and its potential as a standard analytical tool for the determination of polyphenols in natural products and biological fluids, are discussed.

Atmospheric Pressure↗
PubMed2003

Passive sampling screening method using thin-layer chromatography plates.

An in situ solid-phase extraction method, thin-layer chromatography (TLC) passive sampling, was investigated as a screening method for determining the presence of organic compounds in water using laboratory experiments and field applications. The TLC passive sampler developed in this research enables the spatial and temporal distributions of organic compounds to be determined qualitatively with little expense. The materials for the sampler developed here cost dollar 1.60 each. By first identifying the areas where a pollutant is present using the TLC passive sampling screening method, total analytical costs for monitoring programs may be reduced by eliminating unnecessary conventional analyses for locations where the pollutant is not present. Two organophosphorus pesticides, diazinon and chlorpyrifos, were used as a model for the development and as a potential application of the TLC passive sampling method. Passive sampler adsorption kinetics, enrichment factors, and extraction efficiencies were determined from batch experiments with exposure times ranging from 1 h to 4 weeks. In field applications, TLC passive sampling was conducted in natural and engineered systems with two silica gel extraction media, C2 and C18. Diazinon and chlorpyrifos were detected by analyzing the adsorbed compounds by high-performance liquid chromatography with ultraviolet detection.

Chromatography, High Pressure Liquid↗
PubMed1994

Fluorescence lifetime imaging microscopy: homodyne technique using high-speed gated image intensifier.

In the previous sections we demonstrated imaging of intracellular Ca2+ using our approach to FLIM. What other analytes can be imaged using FLIM? We have now characterized the lifetime of a good number of ion indicators. Based on these studies we know that Cl- can be imaged using FLIM with probes such as SPQ or MQAE, pH can be imaged using resorufin and probes of the SNAFL and SNARF (Molecular Probes) series, and Mg2+ can be imaged using Magnesium Green, Mag-quin-2, or Mag-quin-1 (Molecular Probes). At present, the probe for K+, as PBFI, are just adequate as a lifetime probe, but it seems likely that newer probes for Na+ (Sodium Green) and K+ will be practical for effective imaging. Of course, imaging of oxygen is possible using a wide variety of fluorophores. It should be noted that a wide variety of substances and/or phenomena are known to alter decay times, acting as quenchers. These include the phenomena of resonance energy transfer, collisional quenching, temperature effects, and viscosity effects. Also, the FLIM method is not limited to microscopic objects but can be possibly used in remote imaging of any object. Hence, FLIM will allow the imaging of the chemical and physical properties of objects based on the effects of the local environment on the decay kinetics of fluorophores. The instrumentation for FLIM is presently complex and requires a moderately complex laser source, a gain-modulated image intensifier, and a slow-scan CCD camera. However, one can readily imagine the instrumentation becoming rather compact, and even all solid-state, owing to advances in laser and CCD technologies and, more importantly, advances in probe chemistry. To be specific, the dye laser shown in Fig. 1 may be replaced by a simpler UV laser, such as the 354 nm HeCd laser which has become available (Fig. 11). Intensity modulation of a continuous wave sources can be accomplished with acoustooptic modulators. The scientific slow-scan CCD cameras are presently rather expensive, but they are used in the present instrumentation because of their linearity and high dynamic range. However, the increasing use of CCD detectors suggest that even the scientific-grade CCD cameras will soon become less costly. Additionally, the frame rates of these detectors continue to increase in response to the need for faster imaging. Furthermore, the performance of the video CCD cameras is increasing, as seen by the introduction of 10-bit video analog-to-digital (A/D) converters.(ABSTRACT TRUNCATED AT 400 WORDS)

Aminoquinolines↗
PubMed1990

Method in bioethics: a troubled assessment.

This discussion is a critical assessment of the methods employed by some leading writers in the field of bioethics. The author agrees with those in the field who regard its primary or essential method as moral philosophy, but he nevertheless finds a prevalent tendency among bioethical writers merely to apply received moral principles to issues and to avoid penetrating theoretical analysis, even when such analysis is unavoidably required. He explains these deficiencies in terms of the exigencies of interdisciplinary work and the affinity of much early bioethics with policy- or legislatively-oriented "public ethics". The discussion ends with a call for increased theoretical sophistication in this field.

Bioethics↗
PubMed2002

Effectiveness and reliability of arsenic field testing kits: are the million dollar screening projects effective or not?

The exposure of millions to arsenic contaminated water from hand tube wells is a major concern in many Asiatic countries. Field kits are currently used to classify tube wells as delivering arsenic below 50 microg/L (the recommended limit in developing countries) as safe, painted green or above 50 microg/L, unsafe and painted red. More than 1.3 million tube wells in Bangladesh alone have been tested by field kits. A few million U.S. dollars have already been spent and millions are waiting for the ongoing projects. However, the reliability of the data generated through field kits is now being questioned. Samples from 290 wells were tested by field kits and by a reliable laboratory technique to ascertain the reliability of field kits. False negatives were as high as 68% and false positives up to 35%. A statistical analysis of data from 240 and 394 other wells yielded similar rates. We then analyzed 2866 samples from previously labeled wells and found 44.9% mislabeling in the lower range (<50 microg/L) although mislabeling was considerably reduced in the higher range. Variation of analytical results due to analysts and replicates were pointed out adopting analysis of variance (ANOVA) technique. Millions of dollars are being spent without scientific validation of the field kit method. Facts and figures demand improved, environmentally friendly laboratory techniques to produce reliable data.

Algorithms↗
PubMed1993

Propagation of photon-density waves in strongly scattering media containing an absorbing semi-infinite plane bounded by a straight edge.

Light propagation in strongly scattering media can be described by the diffusion approximation to the Boltzmann transport equation. We have derived analytical expressions based on the diffusion approximation that describe the photon density in a uniform, infinite, strongly scattering medium that contains a sinusoidally intensity-modulated point source of light. These expressions predict that the photon density will propagate outward from the light source as a spherical wave of constant phase velocity with an amplitude that attenuates with distance r from the source as exp(-alpha r)/r. The properties of the photon-density wave are given in terms of the spectral properties of the scattering medium. We have used the Green's function obtained from the diffusion approximation to the Boltzmann transport equation with a sinusoidally modulated point source to derive analytic expressions describing the diffraction and the reflection of photon-density waves from an absorbing and/or reflecting semi-infinite plane bounded by a straight edge immersed in a strongly scattering medium. The analytic expressions given are in agreement with the results of frequency-domain experiments performed in skim-milk media and with Monte Carlo simulations. These studies provide a basis for the understanding of photon diffusion in strongly scattering media in the presence of absorbing and reflecting objects and allow for a determination of the conditions for obtaining maximum resolution and penetration for applications to optical tomography.

Animals↗
PubMed1999

Experimental observation of light-induced solitary waves of analyte bands in capillary electrophoresis.

The phenomenon of electrophoresis in free solution has been studied theoretically down to the molecular level for decades. In addition, intermolecular photo-induced proton transfer reactions, which occur in a wide class of molecules (phenols and aminoarenes) as well as proteins (green fluorescent protein), were also studied extensively. However, the study of the effect of light-induced electrophoretic mobility changes of the analytes in electrophoresis was begun only recently. In the present work, capillary zone electrophoresis was chosen as the environment to measure the magnitude of these electrophoretic mobility shifts induced by light. Background electrolytes (running electrolytes) with high refractive indices were developed, allowing the capillary to work like an optical fiber. The experimental conditions for obtaining stable coupling and guided laser light along the liquid core are discussed. Experimental evidence of band compression is observed, leading to a solitary wave behavior of the analyte band (2-naphthol). These solitary waves result from competition between thermal diffusion (dispersion mechanism) and a nonlinear (band compression) effect due to the combined electrophoresis phenomenon and absorption of guided light by the molecules of the band (which are subjected to a "reversible intermolecular proton transfer reaction" as one of their decay routes). The possibilities of applying this effect to different methods and techniques are also discussed.

Buffers↗
PubMed1999

Transient infrared spectroscopy for detection of toxigenic fungi in corn: potential for on-line evaluation.

An urgent need for rapid sensors to detect contamination of food grains by toxigenic fungi such as Aspergillus flavus prompted research and development of Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) as a highly sensitive probe for fungi growing on the surfaces of individual corn kernels. However, the photoacoustic technique has limited potential for screening bulk corn because currently available photoacoustic detectors can accommodate only a single intact kernel at a time. Transient infrared spectroscopy (TIRS), on the other hand, is a promising new technique that can acquire analytically useful infrared spectra from a moving mass of solid materials. Therefore, the potential of TIRS for on-line, noncontact detection of A. flavus contamination in a moving bed of corn kernels was explored. Early test results based on visual inspection of TIRS spectral differences predict an 85% or 95% success rate in distinguishing healthy corn from grain infected with A. flavus. Four unique infrared spectral features which identified infected corn in FTIR-PAS were also found to be diagnostic in TIRS. Although the technology is still in its infancy, the preliminary results indicate that TIRS is a potentially effective screening method for bulk quantities of corn grain.

Aflatoxins↗