SEARCH · PubMed Health

Results for “Detection”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources

PubMed2006

Trace level detection and quantitation of ethyl diazoacetate by reversed-phase high performance liquid chromatography and UV detection.

A method using reversed-phase high performance liquid chromatography (HPLC) with UV detection has been developed and validated for the trace level (ng/mL) detection and quantitation of ethyl diazoacetate (EDA), a toxic impurity, in sample matrix. Method development included the evaluation of several analytical techniques including LC-MS and GC-MS, which in this case, proved to be unacceptable means of analysis. The chromatographic separation employed in this method utilizes a mobile phase system of acetonitrile and water with analysis carried out using UV detection at 250 nm. The final method showed excellent linearity, accuracy, repeatability, specificity and recovery when evaluated at the quantitation limit (QL) of 6 ng/mL.

Chromatography, High Pressure Liquid↗

PubMed2007

Indirect detection of Bacillus anthracis using real-time PCR to detect amplified gamma phage DNA.

Typical real-time PCR methods used to identify Bacillus anthracis do not distinguish between viable and non-viable spores, which would be critical in any first response and remediation scenarios. This study combined both real-time PCR, using primers specifically designed for gamma phage, with the highly specific gamma phage amplification into one simple assay to indirectly detect Bacillus anthracis. Since the amplification of gamma phage only occurs in the presence of a suitable host, the detection of increasing concentrations of progeny gamma phage DNA using real-time PCR implies the presence of viable Bacillus anthracis cells. This method detected a starting Bacillus anthracis concentration of 207 cfu/mL, equivalent to less than one cell in 20 microL, in less than 5 h.

Bacillus Phages↗

PubMed2006

Use of hybridization melting kinetics for detecting Phytophthora species using three-dimensional microarrays: demonstration of a novel concept for the differentiation of detection targets.

Microarray-based detection is limited by variable and inconsistent hybridization intensities across the diversity of probes used in each array. In this paper, we introduce a novel concept for the differentiation of detection targets using duplex melting kinetics. A microarray assay was developed on a PamChip microarray enabling the differentiation of target Phytophthora species using the melting kinetics of probe-target duplexes. In the majority of cases the hybridization kinetics of target and non-target duplexes differed significantly. Analysis of the melting kinetics of duplexes formed by probes with target and non-target DNA was found to be an effective method for determining specific hybridization and was independent of fluctuations in hybridization signal intensity. This form of analysis was more robust than the traditional approach based on hybridization intensity, and enabled the detection of individual Phytophthora species and mixtures thereof.

DNA, Fungal↗

PubMed1988

Detection and determination of common benzodiazepines and their metabolites in blood samples of forensic science interest. Microcolumn cleanup and high-performance liquid chromatography with reductive electrochemical detection at a pendent mercury drop electrode.

Benzodiazepines in the blood samples typical of forensic science work are recovered from 100-250 microliters amounts of blood (diluted with aqueous sodium octyl sulphate to suppress protein binding) onto microcolumns of Porapak-T, and finally eluted into 60-microliters volumes of aqueous acetonitrile. The eluates may be taken directly for analysis by high-performance liquid chromatography (HPLC) with reductive amperometric detection at a pendent mercury drop electrode held at potentials down to -1.2 V vs. Ag/AgCl. For high sensitivity work the electrode is preceded by a coulometric detector fitted with porous carbon electrodes held at 0 V (proprietary reference electrode). The technique detects all of the commonly encountered benzodiazepines and others except clobazam, which contains no azomethine group. The detection limits generally are in the range 1-5 ng/ml (40-200 pg HPLC-injected) in hemolyzed human blood, with recovery values of 84-95%, depending on the actual benzodiazepine, over the range examined (less than or equal to 2.14 micrograms/ml). The respective values for the metabolites of nitrazepam are 8-12 ng/ml and 75-84%. The technique is very much less susceptible to the interferences afflicting other commonly applied techniques, and facilitates considerably the analysis of degraded samples.

Animals↗

PubMed1988

Direct, sensitive and selective detection of free fatty acids by high-performance liquid chromatography with post-column ion-pair extraction and absorbance detection.

Free fatty acids (C8-C18) are separated by reversed-phase liquid chromatography and detected using a simple post-column dynamic extraction system in which the acids are extracted as ion pairs with chloroform from the aqueous acetonitrile (gradient: 79-99% acetonitrile) mobile phase after the post-column addition of aqueous Methylene Blue solution. The chloroform phase containing the ion pairs is monitored with an absorbance detector at 651 nm. The detection limits ranged from 26 to 83 ng, depending upon the acid, with coefficients of variation of 1.2-14%. Application of the method to butter and margarine samples permitted detection of free fatty acids down to 35 ppm and in orange juice, down to 0.5 ppm using only an organic solvent extraction without further sample clean-up for isolation of the fatty acids.

Acetonitriles↗

PubMed1989

Ester and related derivatives of ring N-pentafluorobenzylated 5-hydroxymethyluracil. Hydrolytic stability, mass spectral properties, and trace detection by gas chromatography-electron-capture detection, gas chromatography-electron-capture negative ion mass spectrometry, and moving-belt liquid chromatography-electron-capture negative ion mass spectrometry.

One consequence of radiation damage to DNA is the conversion of thymine to 5-hydroxymethyluracil (HMU). In order to sensitively detect this DNA adduct by gas chromatography (GC) or high-performance liquid chromatography (HPLC) with electron-capture detection techniques, it is necessary to derivatize it. This study was designed to select an optimum ester derivative of the aliphatic hydroxyl group on HMU. N1, N3-Bis(pentafluorobenzyl)-HMU was formed as a parent derivative, and from this a series of esters. Also O-pentafluorobenzyl and O-tetrafluorobenzyl ether derivatives were prepared. Of the esters the pivalyl derivative was the best choice because it formed easily, was relatively stable to aqueous hydrolysis (t 1/2 = 9.8 days at pH 11.5, 24 degrees C) and gave a response at fmol levels by GC and LC comparable to that of the ethers. Unanticipated was a good response as well for the parent derivative, a free hydroxyl compound, by GC and LC at this level. The work also demonstrates a high performance by LC-electron-capture negative ion mass spectrometry with a belt interface for the trace detection of derivatives of this type.

Chemical Phenomena↗

PubMed1987

Detection of some retinoid radicals using high-performance liquid chromatography with electron spin resonance spectroscopy or electrochemical detection.

Radical species were detected in the incubation mixtures of some retinoids (retinoic acid, retinal, retinol and retinyl acetate) by using the spin-trapping technique. The spin-adducts were resolved by high-performance liquid chromatography on a reversed-phase column with isocratic elution and detected by electron spin resonance spectroscopy and electrochemical detection. The spin-adducts were eluted in the order retinoic acid, retinol, retinyl acetate, in a similar manner to the retinoids themselves. These results suggest that the spin-adducts are products of nitrosobenzene with retinoid radicals in which the retinoid radicals retain their original chemical structures.

Chromatography, High Pressure Liquid↗

PubMed2003

Comprehensive two-dimensional gas chromatography with atomic emission detection and correlation with mass spectrometric detection: principles and application in petrochemical analysis.

Comprehensive gas chromatography (GC x GC) has been combined with atomic emission detection (AED) to enable element-selective detection. Under optimised experimental conditions, the requirement of minimum five data points across a peak can be obtained even for analytes eluting early from the second-dimension column. Simple manipulation of the results allows the combined presentation of up to four sets of elemental data in one two-dimensional plot. GC x GC with AED and mass spectrometric (MS) detection in petrochemical analysis for fingerprinting as well as the identification of N- and S-containing unknowns is presented as an application.

Gas Chromatography-Mass Spectrometry↗

PubMed1999

Immunoenzymatic detection of the new proliferation associated protein p100 by means of a cellular ELISA: specific detection of cells in cell cycle phases S, G2 and M.

In vitro proliferation assays are widely used in biomedical research. We describe the immunoenzymatic (ELISA) detection of a recently described proliferation associated protein (p100) by means of a new monoclonal mouse IgG1 antibody (Ki-S2). P100 is a 100 kDa nuclear protein that is specifically detected during the cell cycle phases S, G2 and M. Comparative studies on lectin-stimulated leukocytes using 3H-thymidine labelling and Ki-67 antibodies revealed a statistically significant positive correlation. Since p100 is absent in GO and G1 cells, its detection permits the precise and specific measurement of actual cell cycle events under culture conditions.

Animals↗

PubMed1979

Carrier detection in Duchenne muscular dystrophy: Assessment of the effect of age on detection-rate with serum-creatine-kinase-activity.

In 40 known carriers of the gene for Duchenne muscular dystrophy (mean age 38 years) the detection-rate with a standard assay of serum-creatine-kinase was 53%. In 52 daughters of known carriers (mean age 16 years) the detection-rate was 45% after correction of age. This implies a much higher detection-rate (about 90%) in young carriers and suggests that discrimination between carriers and noncarriers may best be achieved by testing in childhood.

Adolescent↗

PubMed1988

Detection of oxilofrine in plasma and urine by high-performance liquid chromatography with electrochemical detection and comparison with gas chromatography-mass spectrometry.

A high-performance liquid chromatographic (HPLC) method with electrochemical detection for the determination of oxilofrine [1-(4-hydroxyphenyl)-2-methylaminopropanol] in human plasma and urine (before and after cleavage of the metabolic conjugates) is described. Isolation from biological fluids is performed batchwise by weak acid cation exchange. Separation of plasma and urine components is achieved on a reversed-phase C18 column as an ion pair with heptanesulphonic acid. For amperometric detection the potential of the electrode was set at 0.95 V versus an Ag/AgCl reference electrode. The detection limit for oxilofrine in plasma is 1 ng/ml and in urine 12.5 ng/ml at a signal-to-noise ratio of 2.0 using 1.0 ml of plasma and 0.02 ml of urine. The method was compared with a gas chromatographic-mass spectrometric method and showed a good concordance for plasma (r = 0.996) and urine (r = 0.994). With the HPLC method it is also possible to determine related sympathomimetic drugs, e.g., etilefrine, norefenefrine or octopamine, after a slight modification of the mobile phase.

Chromatography, High Pressure Liquid↗

PubMed2004

First results on label-free detection of DNA and protein molecules using a novel integrated sensor technology based on gravimetric detection principles.

A novel integrated bio-sensor technology based on thin-film bulk acoustic wave resonators on silicon is presented and the feasibility of detecting DNA and protein molecules proofed. The detection principle of these sensors is label-free and relies on a resonance frequency shift caused by mass loading of an acoustic resonator, a principle very well known from quartz crystal micro balances. Integrated ZnO bulk acoustic wave resonators with resonance frequencies around 2 GHz have been fabricated, employing an acoustic mirror for isolation from the silicon substrate. DNA oligos have been thiol-coupled to the gold electrode by on-wafer dispensing. In a further step, samples have either been hybridised or alternatively a protein has been coupled to the receptor. The measurement results show the new bio-sensor being capable of both, detecting proteins as well as the DNA hybridisation without using a label. Due to the substantially higher oscillation frequency, these sensors already show much higher sensitivity and resolution comparable to quartz crystal micro balances. The potential for these sensors and sensors arrays as well as technological challenges will be discussed in detail.

Biosensing Techniques↗

PubMed1999

Spike detection II: automatic, perception-based detection and clustering.

OBJECTIVES: We developed perception-based spike detection and clustering algorithms. METHODS: The detection algorithm employs a novel, multiple monotonic neural network (MMNN). It is tested on two short-duration EEG databases containing 2400 spikes from 50 epilepsy patients and 10 control subjects. Previous studies are compared for database difficulty and reliability and algorithm accuracy. Automatic grouping of spikes via hierarchical clustering (using topology and morphology) is visually compared with hand marked grouping on a single record. RESULTS: The MMNN algorithm is found to operate close to the ability of a human expert while alleviating problems related to overtraining. The hierarchical and hand marked spike groupings are found to be strikingly similar. CONCLUSIONS: An automatic detection algorithm need not be as accurate as a human expert to be clinically useful. A user interface that allows the neurologist to quickly delete artifacts and determine whether there are multiple spike generators is sufficient.

Adolescent↗

PubMed1995

Detection of bioactive oligopeptides after microbore HPLC with electrochemical detection of their Cu(II) complexes: effect of operating parameters on sensitivity and selectivity.

We used a microbore reversed phase column for acetonitrile/0.1% aqueous TFA gradient elution separation of peptides with the detection of their copper complexes by electrochemical detection. The copper complexes are formed in a short (1 or 1.5 min) postcolumn reactor following mixing of the eluent with the postcolumn reaction phase. Detection can be at an upstream anode or a downstream cathode of a dual-electrode electrochemical detector. The following parameters have been investigated for their effect on the sensitivity and the selectivity of the procedure: postcolumn pH, buffer type, temperature, reaction time, and anode potential. Of the 23 bioactive peptides used, there are several that fall into classes according to their chemical and electrochemical behavior with copper(II): those with a blocked terminal amine, those with aspartate in the third position, those that have an electroactive amino acid, and those that have a cyclic structure formed by the amide backbone through a Cys-Cys disulfide bridge. Depending on these attributes, the operating parameters have an influence on the sensitivity of the determination. Among the more well-defined results are the following. Uncomplicated peptides with a free amine terminus react rapidly in the postcolumn reactor and give signals in the range predicted by theory. There is evidence that longer peptides, and those with a blocked amine terminus, have a sensitivity limited by kinetic factors. The oxidations of tyrosine and tryptophan in peptides are dramatically influenced by buffer type at pH 9.8. At pH 8.0, there is no signal from several peptides in phosphate buffer, while in borate there is a signal.

Amino Acid Sequence↗

PubMed2005

Detection of C-reactive protein utilizing magnetic permeability detection based immunoassays.

A new sensing technology platform integrating magnetic permeability detection and a two-site heterogeneous immunoassay in a one-step analysis is described. As a platform model, measurements of C-reactive protein (CRP), a cardiac and inflammation marker, were performed in a rapid (11.5 min) high-sensitivity (hs) procedure with a low detection limit (0.2 mg/L) and accuracy (CV = 11%). The two-site heterogeneous immunoassay was performed in 1.2-mL disposable reagents vials containing solid phase (polyclonal anti-CRP conjugated silica microparticles), labeling agent (monoclonal anti-CRP conjugated superparamagnetic nanoparticles), and reaction buffer. Whole blood (20 muL) was assayed by introducing the sample into a reagent vial using a glass capillary and mixing its contents by hand for 30 s. After a 11-min sedimentation step, the vial was placed into the coil of the magnetic permeability detector, which measured the enrichment of superparamagnetic nanoparticles in the solid-phase sediment. Magnetic permeability detection and quantification is based on the principle that when paramagnetic materials are placed inside a coil, the inductance of the coil is influenced. Screening of CRP on whole blood patient samples showed good correlation with central hospital measurements for hsCRP (y = 1.018x - 0.021, R(2) = 0.980, n = 103) and normal range CRP (y = 1.02x + 2.53, R(2)= 0.991, n = 33) analyses. The mean differences of the two methods according to the Bland and Altman plots were -0.03 +/- 1.12 mg/L for hsCRP analysis and -3.4 +/- 8.64 mg/L for normal range CRP analysis.

C-Reactive Protein↗

PubMed1980

Detection and characterization of complexes of methylmercury (II) with duplex deoxyribonucleic acid and synthetic copolymers by optical detection of magnetic resonance.

Complexes formed between Ch3HgOH and the polynucleotide duplexes poly(dA)-poly(dT) and poly(dG)-poly(dC) and calf thymus DNA have been detected and characterized byu luminescence and optically detected magnetic resonance (ODMR) spectroscopy. CH3HgOH is added by equilibrium dialysis at concentrations well below those previously found to cause denaturation of the duplex. Complexing of CH2HgII with the polynucleotide leads to heavy atom effects which are detected by the appearance of short-lived components in the phosphorescence decay. Heavy atom perturbed bases are identified by slow-passage ODMR frequencies and the lifetimes of phosphorescence transients induced by microwave rapid passage. Comparison of the zero-field splitting (zfs) parameters and signal polarity patterns with those found previously in specific mononucleotide and mononucleoside complexes with CH3HgII leads to the positive identification of complexed bases as well as the CH3HgII binding sites. We find that CH3HgOH at 10-5M complexes with N3 of thymine in poly(dA)-poly(dT) and with N7 of guanine in both poly (dG)-poly(dC) at pH 6, and calf thymus DNA at pH 6.8. When Ch3HgOH is added at 10-6M, we find that complexing occur at N3 of thymine. The thymine triplet state properties are altered, but not necessarily as the result of a heavy-atom, effect. Evidence for the presence of this type of complex in DNA treated with 10-5M CH3HgOH is provided by the presence of thymine triplet states with properties similar to those observed in poly(dA)-poly(dT) treated at 10-6M.

Animals↗

PubMed1983

Sharp targets are detected better against a figure, and blurred targets are detected better against a background.

There is growing evidence that the performance of perceptual tasks is often facilitated by perceived "figureness." Accuracy in detection and discrimination of targets is higher when the targets are presented in figural regions than when they are presented in ground regions of an image. This "figure superiority" might be a result of a functional specialization in the visual analysis of figure; recent theories have also assumed a functional specialization in the visual analysis of ground. If so, we might expect "ground superiority" in situations where task performance requires information available primarily through analysis of ground. We manipulated the spatial frequency of a small line segment and found that when it was sharp (i.e., the high-spatial-frequency components were present), it was detected better in figural regions, but when we blurred it (only the low-to-medium spatial frequencies were present) it was detected better in ground regions. These findings support the view that figure and ground analyses involve different specialized functions.

Adolescent↗

PubMed1993

Syrian hamster embryo cell lines useful for detecting transforming genes in mouse tumours: detection of transforming genes in X-ray-related mouse tumours.

The Syrian hamster embryo cell lines, SHOK and MC-1, were used as recipient cells for DNA transfection assay to detect transforming genes in experimental mouse tumours. A mouse repeat sequence was utilised to check whether each transformed focus included mouse genomic DNA in the Hamster background. We investigated five mouse tumours that are related to X-ray radiation, and detected activated c-K-ras, c-mos, and c-cot oncogenes which induced foci of hamster cells. These results show that SHOK and MC-1 cells have unique properties for detecting transforming genes in experimental mouse tumours.

3T3 Cells↗