Showing papers on "Detection limit published in 2005"
TL;DR: A validated protocol for quantitative high resolution 1H-NMR using single pulse excitation that considers all issues regarding linearity, robustness, specificity, selectivity and accuracy as well as influences of instrument specific parameters and the data processing and evaluation routines is described.
526 citations
TL;DR: In this paper, the spectral position of the whispering gallery mode (WGM) of a sphere shifts in response to the refractive index change in the surrounding medium, resulting in a sensitivity of approximately 30nm∕RIU (refractive index units).
Abstract: We have developed a highly sensitive refractometric sensor based on fused silica microsphere resonators. The spectral position of the whispering gallery mode (WGM) of a sphere shifts in response to the refractive index change in the surrounding medium. The strong light-matter interaction due to the extremely high Q factor associated with the WGM results in a sensitivity of approximately 30nm∕RIU (refractive index units). This, together with the high spectral resolution of our sensor system (∼0.01pm), yields a detection limit of refractive index change on the order of 10−7RIU. Theoretical calculation is also performed and agrees well with the experimental data.
361 citations
TL;DR: A diagnostic test employing monoclonal antibodies for the selective extraction of viral pathogens from a sample in a chip-scale, sandwich immunoassay format has been developed using surface-enhanced Raman scattering (SERS) as a readout method, which has a linear dynamic range and limit of detection of 1.5 x 10(8) viruses/mL.
Abstract: The need for rapid, highly sensitive, and versatile diagnostic tests for viral pathogens spans from human and veterinary medicine to bioterrorism prevention. As an approach to meet these demands, a diagnostic test employing monoclonal antibodies (mAbs) for the selective extraction of viral pathogens from a sample in a chip-scale, sandwich immunoassay format has been developed using surface-enhanced Raman scattering (SERS) as a readout method. The strengths of SERS-based detection include its inherent high sensitivity and facility for multiplexing. The capability of this approach is demonstrated by the capture of feline calicivirus (FCV) from cell culture media that is exposed to a gold substrate modified with a covalently immobilized layer of anti-FCV mAbs. The surface-bound FCVs are subsequently coupled with an extrinsic Raman label (ERL) for identification and quantification. The ERLs consist of 60-nm gold nanoparticles coated first with a layer of Raman reporter molecules and then a layer of mAbs. The ...
303 citations
TL;DR: The photoluminescence study showed that the PL intensity of the OPH/QDs bioconjugate was quenched in the presence of paraoxon, indicating that the quenching of PL intensity was caused by the conformational change in the enzyme.
Abstract: In this paper, we first report a novel biosensor for the detection of paraoxon based on (CdSe)ZnS core-shell quantum dots (QDs) and an organophosphorus hydrolase (OPH) bioconjugate. The OPH was coupled to (CdSe)ZnS core-shell QDs through electrostatic interaction between negatively charged QDs surfaces and the positively charged protein side chain and ending groups (-NH2). Circular dichroism (CD) spectroscopy showed no significant change in the secondary structure of OPH after the bioconjugation, which indicates that the activity of OPH was preserved. Detectable secondary structure changes were observed by CD spectroscopy when the OPH/QDs bioconjugate was exposed to organophosphorus compounds such as paraoxon. Photoluminescence (PL) spectroscopic study showed that the PL intensity of the OPH/QDs bioconjugate was quenched in the presence of paraoxon. The overall quenching percentage as a function of paraoxon concentration matched very well with the Michaelis-Menten equation. This result indicated that the quenching of PL intensity was caused by the conformational change in the enzyme, which is confirmed by CD measurements. The detection limit of paraoxon concentration using OPH/QDs bioconjugate was about 10(-8) M. Although increasing the OPH molar ratio in the bioconjugates will slightly increase the sensitivity of biosensor, no further increase of sensitivity was achieved when the molar ratio of OPH to QDs was greater than 20 because the surface of QDs was saturated by OPH. These properties make the OPH/QDs bioconjugate a promising biosensor for the detection of organophosphorus compounds.
266 citations
TL;DR: The use of labelled glyphosate as internal standard allowed improving the recovery and precision for glyphosate and AMPA, while it was not efficient for glufosinate, that was quantified by external standards calibration.
212 citations
TL;DR: The high sensitivity and high throughput of this analytical method combined with the ease of use and effective automated sample preparation procedure make it suitable for large epidemiological studies to evaluate the prevalence of human exposure to phthalates.
Abstract: We developed an on-line solid-phase extraction (SPE) method, coupled with isotope dilution high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) and with automated sample preparation, to simultaneously quantify 16 phthalate metabolites in human urine. The method requires a silica-based monolithic column for the initial preconcentration of the phthalate metabolites from the urine and a silica-based conventional analytical column for the chromatographic separation of the analytes of interest. It uses small amounts of urine (100 μL), is sensitive (limits of detection range from 0.11 to 0.90 ng/mL), accurate (spiked recoveries are ∼100%), and precise (the inter- and intraday coefficients of variation are <10%). The method is not labor intensive, and, because pretreatment of the urine samples was performed automatically using an HPLC autosampler, involves minimal sample handling, thus minimizing exposure to hazardous chemicals. The method was validated on spiked, pooled urine samples and...
203 citations
TL;DR: It has finally appeared that these biosensors are quite sensitive to Cd2+ and Zn2+ (limits of detection (LOD) = 10 ppb for a 30 min long exposure) while Pb2+ gives no significant inhibition as this ion seems to adsorb on albumin preferably.
196 citations
TL;DR: In this paper, the voltammetric behavior of dihydroxybenzene isomers was studied with glassy carbon electrodes modified with multi-wall carbon nanotubes.
195 citations
TL;DR: The CPE method was successfully applied to the determination of lead in water samples and the chemical variables affecting the separation phase were optimized.
175 citations
TL;DR: In this paper, a method was developed for the sensitive and selective determination of cyromazine and its metabolite melamine in chard samples, which involves an extraction procedure with phosphate buffer and methanol using high-speed blender, the addition of tridecafluoroheptanoic acid (TFHA) as ion-pair reagent and the injection of the fivefold diluted extract on liquid chromatography coupled to electrospray tandem mass spectrometry (LC-ESI-MS/MS).
174 citations
TL;DR: A novel, sensitive electrochemical immunoassay has been developed based on the precipitation of silver on colloidal gold labels which, after silver metal dissolution in an acidic solution, was indirectly determined by anodic stripping voltammetry (ASV) at a glassy-carbon electrode.
TL;DR: In this article, a simultaneous preconcentration method was developed for determination of trace amounts of Cu, Fe and Pb by atomic absorption spectrometry, based on the retention of their methylthymol blue complexes by naphthalene methyltrioctyl ammonium chloride adsorbent in a column.
TL;DR: Results have shown that using screen-printed electrodes aflatoxin M1 can be measured with a detection limit of 25 ppt and with a working range between 30 and 160 ppt.
TL;DR: It was found that the storage of tissue samples at -20 degrees C caused losses of dopamine and serotonin and the total time of analysis was substantially reduced resulting in a sample preparation and assay time of 15-20 min.
TL;DR: The freeze-drying, extraction, and analysis methods should be useful for assessing the distribution of capsaicinoids in the foods and in defining the roles of these biologically active compounds in the plant, the diet, and medicine.
Abstract: Diverse procedures have been reported for the isolation and analysis of secondary metabolites called capsaicinoids, pungent compounds in the fruit of the Capsicum (Solanaceae) plant. To further improve the usefulness of high-performance liquid chromatography (HPLC), studies were carried out on the analysis of extracts containing up to eight of the following capsaicinoids: capsaicin, dihydrocapsaicin, homocapsaicin-I, homocapsaicin-II, homodihydrocapsaicin-I, homodihydrocapsaicin-II, nonivamide, and nordihydrocapsaicin. HPLC was optimized by defining effects on retention times of (a) the composition of the mobile phase (acetonitrile/0.5% formic acid in H2O), (b) the length of the Inertsil column, and (c) the capacity values (k) of the column packing. Identification was based on retention times and mass spectra of individual peaks. Quantification was based on the UV response at 280 nm in HPLC and recoveries from spiked samples. The method (limit of detection of ∼15−30 ng) was successfully used to quantify ...
TL;DR: A simple and reproducible method for qualitative and quantitative analysis of phenolic compounds in virgin olive oils by solid-phase extraction, high performance liquid chromatography with diode array detector (HPLC-DAD), and HPLC-mass spectrometry (MS) in tandem mode was developed.
Abstract: A simple and reproducible method for qualitative and quantitative analysis of phenolic compounds in virgin olive oils by solid-phase extraction (SPE), high performance liquid chromatography with diode array detector (HPLC-DAD), and HPLC-mass spectrometry (MS) in tandem mode was developed. The polar fraction was obtained from samples of three different virgin olive oils. Detection and quantification were performed at 280, 240, and 320 nm. For identification purposes, HPLC-MS/MS was equipped with turbo ion spray source in the negative-ion mode. Twenty compounds of twenty-three detected and quantified were characterized. The method showed satisfactory linearity (r > 0.99), good recovery, satisfactory precision, and appropriate limits of detection (LOD) and quantification (LOQ).
TL;DR: Surface plasmon resonance biosensor formats using gold nanoparticle or protein signal amplification for the sensitive assay of small molecules were developed using progesterone as a model compound and found that secondary antibody labeling gave 8.1-fold signal enhancements and a limit of detection of 20.1 pg/ml.
TL;DR: The proposed methodology proved to be very convenient and effective, and was successfully applied to the analysis of 11 Mate tea samples commercialised in Brazil, showing good agreement.
TL;DR: The presented method can provide insights into the actual internal burden of the general population and certain risk groups and will help to further explore the human metabolism of DEHP-an occupational and environmental toxicant of great concern.
TL;DR: V voltammetric sequential determination of Pt(II), Pd(II, and Rh(III), by square-wave adsorption stripping voltammetry (SWAdSV), and Pb( II), bysquare-wave anodic stripping voltamonmetry ( SWASV), in vegetable environmental matrices is reported.
Abstract: This paper reports voltammetric sequential determination of Pt(II), Pd(II), and Rh(III), by square-wave adsorption stripping voltammetry (SWAdSV), and Pb(II), by square-wave anodic stripping voltammetry (SWASV), in vegetable environmental matrices. Analytical procedures were verified by the analysis of the standard reference materials: Olive Leaves BCR-CRM 062 and Tomato Leaves NIST-SRM 1573a. Precision and accuracy, expressed as relative standard deviation and relative error, respectively, were always less than 6% and the limits of detection (LOD) for each element were below 0.096 μg g−1. Once set up on the standard reference materials, the analytical procedure was transferred and applied to laurel leaves sampled in proximity to a superhighway and in the Po river mouth area. A critical comparison with spectroscopic measurements is discussed.
TL;DR: The results showed that the proposed method is simple, rapid, accurate and precise method for analysis of binary and ternary mixtures.
TL;DR: An array-based optical biosensor for the simultaneous analysis of multiple samples in the presence of unrelated multi-analytes was fabricated and exhibited high specificity in identifying multiple analytes.
TL;DR: The molecularly imprinted polymer (MIP) enabled the selective extraction of four organophosphorus pesticides successfully from water and soil samples, demonstrating the potential of molecularly implanted solid-phase extraction for rapid, selective, and cost-effective sample pretreatment.
TL;DR: The needle trap performed very well as an exhaustive spot sampler, as well as in a time-weighted average (TWA) operation and against the standard NIOSH 1501 method using charcoal tubes for indoor air surveys demonstrated good accuracy for the NT approach.
TL;DR: In this paper, metal ion imprinted polymer (MIIP) was used for copolymerizing mercury chloride (or without it), diazoaminobenzene (DAAB) and vinylpyridine (VP) using ethyleneglycoldimethacrylate (EGDMA) as crosslinker in the presence of 2,2′-azobisisobutryonitrile as initiator.
TL;DR: In this paper, an on-line pre-concentration system for cadmium determination in drinking water using flame atomic absorption spectrometry (FAAS) was proposed.
TL;DR: The new approach for developing a cloud point extraction-electrothermal atomic absorption spectrometry has been described and used for determination of arsenic and was successfully applied to the determination of As(III) and As(V) in tap water and total arsenic in biological samples (hair and nail).
TL;DR: The use of the SPE was demonstrated to be highly effective and led to significant decreases in the interferences, and the method was subsequently applied to the analysis of Intercept samples collected at the roadside by the police, and to determine MDMA and MDA levels in oral fluid samples from a controlled study.
TL;DR: A simple and rapid HPLC method has been developed for simultaneous determination of the four resveratrol forms in a Grenache wine from Châteauneuf du Pape with reliable separations at low pressure with a short analysis time.
TL;DR: A capillary electrophoresis method with ultraviolet (UV) detection was developed and optimized for the enantiomer separation of norepinephrine, epinephrine and isoprenaline using dual cyclodextrins of 2-hydroxypropyl-beta-CD and heptakis as chiral selectors.