Showing papers on "Detection limit published in 2011"
TL;DR: The presented review provides information relating to the calculation of the limit of detection and limit of quantitation.
Abstract: The quality of an analytical method developed is always appraised in terms of suitability for its intended purpose, recovery, requirement for standardization, sensitivity, analyte stability, ease of analysis, skill subset required, time and cost in that order. It is highly imperative to establish through a systematic process that the analytical method under question is acceptable for its intended purpose. Limit of detection (LOD) and limit of quantification (LOQ) are two important performance characteristics in method validation. LOD and LOQ are terms used to describe the smallest concentration of an analyte that can be reliably measured by an analytical procedure. There has often been a lack of agreement within the clinical laboratory field as to the terminology best suited to describe this parameter. Likewise, there have been various methods for estimating it. The presented review provides information relating to the calculation of the limit of detection and limit of quantitation. Brief information about differences in various regulatory agencies about these parameters is also presented here.
2,264 citations
TL;DR: In this paper, the authors constructed a new chemical ionization time-of-flight mass spectrometer (CI-TOFMS) that measured atmospheric trace gases in real time with high sensitivity.
Abstract: . We constructed a new chemical ionization time-of-flight mass spectrometer (CI-TOFMS) that measures atmospheric trace gases in real time with high sensitivity. We apply the technique to the measurement of formic acid via negative-ion proton transfer, using acetate as the reagent ion. A novel high pressure interface, incorporating two RF-only quadrupoles is used to efficiently focus ions through four stages of differential pumping before analysis with a compact TOFMS. The high ion-duty cycle (>20 %) of the TOFMS combined with the efficient production and transmission of ions in the high pressure interface results in a highly sensitive (>300 ions s−1 pptv−1 formic acid) instrument capable of measuring and saving complete mass spectra at rates faster than 10 Hz. We demonstrate the efficient transfer and detection of both bare ions and ion-molecule clusters, and characterize the instrument during field measurements aboard the R/V Atlantis as part of the CalNex campaign during the spring of 2010. The in-field short-term precision is better than 5 % at 1 pptv (pL/L), for 1-s averages. The detection limit (3 σ, 1-s averages) of the current version of the CI-TOFMS, as applied to the in situ detection of formic acid, is limited by the magnitude and variability in the background determination and was determined to be 4 pptv. Application of the CI-TOFMS to the detection of other inorganic and organic acids, as well as the use of different reagent ion molecules (e.g. I−, CF3O−, CO3−) is promising, as we have demonstrated efficient transmission and detection of both bare ions and their associated ion-molecule clusters.
194 citations
TL;DR: In this article, a surface-enhanced Raman scattering (SERS) platform for the selective trace analysis of As(3+) ions was reported based on glutathione (GSH)/4-mercaptopyridine (4-MPY)-modified silver nanoparticles (AgNPs).
Abstract: A highly sensitive surface-enhanced Raman scattering (SERS) platform for the selective trace analysis of As(3+) ions was reported based on glutathione (GSH)/4-mercaptopyridine (4-MPY)-modified silver nanoparticles (AgNPs). Here, GSH conjugated on the surface of AgNPs for specifical binding with As(3+) ions in aqueous solution through As-O linkage and 4-MPY was used as a Raman reporter. When As(3+) ions were added to the system, the binding of As(3+) with GSH resulted in the aggregation of AgNPs, and excellent Raman signal of 4-MPY reporters was obtained which can reflect the concentration of As(3+) indirectly. Under optimal assay conditions, the limit of detection (LOD) was estimated to be as low as 0.76 ppb, which is lower than the WHO defined limit (10 ppb), and an excellent linear range of 4-300 ppb was obtained. The practical application had been carried out for determination of As(3+) in real water samples.
194 citations
TL;DR: A new solid phase extraction method is described for sensitive and selective determination of trace levels of rhodamine B in soft drink, food and industrial waste water samples and the presented procedure was successfully applied to real samples.
175 citations
TL;DR: The proposed method was applied to the analysis of water samples of different origin (tap, river and sea) and recovery values showed that the matrices under consideration do not significantly affect the extraction process.
165 citations
TL;DR: The detection of the proteins lysozyme and cytochrome c as well as the live bacterial cells of Shewanella oneidensis MR-1 in aqueous solutions with sensitivities order(s) of magnitude higher than those previously reported are reported.
Abstract: We report the detection of the proteins lysozyme and cytochrome c as well as the live bacterial cells of Shewanella oneidensis MR-1 in aqueous solutions with sensitivities order(s) of magnitude higher than those previously reported. Two highly sensitive surface-enhanced Raman scattering (SERS)-based biosensors using optical fibers have been employed for such label-free macromolecule detections. The first sensor is based on a tip-coated multimode fiber (TCMMF) with a double-substrate “sandwich” structure, and a detection limit of 0.2 μg/mL is achieved in protein detections. The second sensor is based on a liquid core photonic crystal fiber (LCPCF) with a better confinement of light inside the fiber core, and a detection limit of 106 cells/mL is achieved for the bacteria detection. Both SERS biosensors show great potential for highly sensitive and molecule-specific detection and identification of biomolecules.
162 citations
TL;DR: In this article, a method was developed to quantify polyphenols or phenolic compounds through direct interactions of polyphenol with Fast Blue BB in an alkaline medium and the absorbance was measured at 420 nm.
161 citations
TL;DR: An enzyme-free amperometric method was established for glucose detection using a nanoporous gold film (NPGF) electrode prepared by a rapid one-step anodic potential step method within 5 min, which showed that the oxidation of ascorbic acid and uric acid can be completely eliminated at such a low applied potential.
156 citations
TL;DR: Qualitative and quantitative detection of most of substituted aromatic pollutants was found to be readily accomplished using the developed TLC-SERS technique, which compared well with GC-MS in terms of identification ability and detection accuracy, and a limit of detection less than 0.2 ppm could be achieved under optimal conditions.
Abstract: A novel facile method for on-site detection of substituted aromatic pollutants in water using thin layer chromatography (TLC) combined with surface-enhanced Raman spectroscopy (SERS) was explored. Various substituted aromatics in polluted water were separated by a convenient TLC protocol and then detected using a portable Raman spectrometer with the prepared silver colloids serving as SERS-active substrates. The effects of operating conditions on detection efficacy were evaluated, and the application of TLC−SERS to on-site detection of artificial and real-life samples of aromatics/polluted water was systematically investigated. It was shown that commercially available Si 60-F254 TLC plates were suitable for separation and displayed low SERS background and good separation efficiency, 2 mM silver colloids, 20 mM NaCl (working as aggregating agent), 40 mW laser power, and 50 s intergration time were appropriate for the detection regime. Furthermore, qualitative and quantitative detection of most of substitut...
153 citations
TL;DR: Results demonstrate the potential usefulness and ruggedness of LTP-MS for the detection of explosives of different classes and the use of ion/molecule reactions to form adducts with particular explosives such as RDX and HMX was shown to enhance the selectivity and specificity.
Abstract: Detection of explosives is important for public safety. A recently developed low-temperature plasma (LTP) probe for desorption and ionization of samples in the ambient environment ( Anal. Chem. 2008 , 80 , 9097 ) is applied in a comprehensive evaluation of analytical performance for rapid detection of 13 explosives and explosives-related compounds. The selected chemicals [pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), cyclo-1,3,5-trimethylenetrinitramine (RDX), tetryl, cyclo-1,3,5,7-tetramethylenetetranitrate (HMX), hexamethylene triperoxide diamine (HMTD), 2,4-dinitrotoluene, 1,3-dinitrobenzene, 1,3,5-trinitrobenzene, 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, 2,6-dinitrotoluene, and 4-nitrotoluene) were tested at levels in the range 1 pg-10 ng. Most showed remarkable sensitivity in the negative-ion mode, yielding limits of detection in the low picogram range, particularly when analyzed from a glass substrate heated to 120 °C. Ions typically formed from these molecules (M) by LTP include [M + NO(2)](-), [M](-), and [M - NO(2)](-). The LTP-mass spectrometry methodology displayed a linear signal response over three orders of magnitude of analyte amount for the studied explosives. In addition, the effects of synthetic matrices and different types of surfaces were evaluated. The data obtained demonstrate that LTP-MS allows detection of ultratrace amounts of explosives and confirmation of their identity. Tandem mass spectrometry (MS/MS) was used to confirm the presence of selected explosives at low levels; for example, TNT was confirmed at absolute levels as low as 0.6 pg. Linearity and intra- and interday precision were also evaluated, yielding results that demonstrate the potential usefulness and ruggedness of LTP-MS for the detection of explosives of different classes. The use of ion/molecule reactions to form adducts with particular explosives such as RDX and HMX was shown to enhance the selectivity and specificity. This was accomplished by merging the discharge gas with an appropriate reagent headspace vapor (e.g., from a 0.2% trifluoracetic acid solution).
150 citations
TL;DR: In this article, a commercial micro-droplet generator was used to generate 30-40 µm droplets with nearly 100% efficiency and high uniformity to the inductively coupled plasma optical emission spectrometer (ICP-OES).
Abstract: Recently, first analyses of single sub-micrometre particles, embedded in liquid droplets, by inductively coupled plasma optical emission spectrometry (ICP-OES) with a size-equivalent detection limit of several hundred nanometres were reported. To achieve lower detection limits which might allow for the analysis of particles in the nanometre size range a more sensitive technique such as mass spectrometry (MS) is required. Various modifications of particle delivery and data acquisition systems commonly used were carried out to install a setup adequate for ICP-MS detection. These modifications enabled us to supply droplets generated by a commercial microdroplet generator (droplet size: 30–40 µm) with nearly 100% efficiency and high uniformity to the ICP. Analyses were performed using both standard solutions of dissolved metals at concentrations of 1 (Ag), 2 (Au), 5 (Au), or 10 (Cu) mg L−1 and highly diluted suspensions of gold and silver nanoparticles with sizes below 110 nm. In doing so, detection efficiencies of 10−6 counts per atom could be achieved while size-related limits of quantification were found to be 21 nm and 33 nm for gold and silver, respectively. Furthermore, the advantages of utilizing microdroplet generators vs. conventional nebulizers for nanoparticle analyses by ICP-MS are discussed.
TL;DR: A highly sensitive inductively coupled plasma mass spectrometric (ICPMS) method for the determination of human carcinoembryonic antigen (CEA) was demonstrated, which combined the inherent high sensitivity of elemental mass Spectrometric measurement with the signal amplification of catalytic silver deposition on immunogold tags.
Abstract: In this work, we demonstrated a highly sensitive inductively coupled plasma mass spectrometric (ICPMS) method for the determination of human carcinoembryonic antigen (CEA), which combined the inherent high sensitivity of elemental mass spectrometric measurement with the signal amplification of catalytic silver deposition on immunogold tags. The silver amplification procedure was easy to handle and required cheap reagents, and the sensitivity was greatly enhanced to 60-fold after a 15 min silver amplification procedure. The experimental conditions, including detection of gold and silver by ICPMS, immunoassay parameters, silver amplification parameters, analytical performance, and clinical serum samples analysis, were investigated. The ICPMS Ag signal intensity depends linearly on the logarithm of the concentration of human CEA over the range of 0.07−1000 ng mL−1 with a limit of detection (LOD, 3σ) of 0.03 ng mL−1 (i.e., 0.15 pM). The LOD of the proposed method is around 2 orders of magnitude lower than tha...
TL;DR: A new, simple, rapid and sensitive solid phase extraction procedure based on separation and preconcentration of trace levels of allura red in water samples on MCI GEL CHP20P column system has been established.
TL;DR: In this paper, a label-free immunosensor for the detection of ochratoxin A (OTA) based on use of magnetic nanoparticles (MNPs) was developed, where a gold electrode was modified using bovine serum albumin conjugate with a glutaraldehyde-thiolamine linker, creating a layer that prevents non-specific binding of OTA on gold.
Abstract: A label-free immunosensor for the detection of ochratoxin A (OTA) based on use of magnetic nanoparticles (MNPs) was developed. A gold electrode was modified using bovine serum albumin conjugate with a glutaraldehyde–thiolamine linker, creating a layer that prevents non-specific binding of OTA on gold. The OTA antibodies were attached to MNPs using the carbodiimide chemistry and afterwards were immobilized on the modified gold electrode using a strong magnetic field. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and surface plasmon resonance (SPR) were used to characterize each step in immunosensor development. The impedance variation due to the specific antibody–OTA interaction was correlated with the OTA concentration in the samples. The increase in electron-transfer resistance values was proportional to the concentration of OTA on a linear range between 0.01 and 5 ng/mL, with a detection limit of 0.01 ng/mL. SPR measurements showed a larger response range (1–50 ng/mL) with a detection limit of 0.94 ng/mL. Analytical results were in accordance with standard ELISA test kit.
TL;DR: Results had proved that the proposed method was with good accuracy and could be applied to the analysis of trace metal ions in biological samples and were proved to be applicable to the Langmuir model and pseudo-second order equation.
TL;DR: A novel liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC-Q-TOFMS) method was developed and successfully applied to the analysis of amino acids and biogenic amines in beer, cheese and sausage samples.
TL;DR: A strategy for the ultra-sensitive detection of Pb(2+) in aqueous media has been developed, and the combination of oxidative exfoliation of graphite and subsequent chemical amination resulted in an amine functionalized graphene oxide, which showed ultra-high sensitivity.
Abstract: A strategy for the ultra-sensitive detection of Pb2+ in aqueous media has been developed. The combination of oxidative exfoliation of graphite and subsequent chemical amination resulted in an amine functionalized graphene oxide, which showed ultra-high sensitivity in detecting Pb2+, as it is an active material in modified anodic stripping voltammetry. A detection limit of as low as 10−13 M (0.1 pM) has been reached, which is comparable to the result obtained from atomic absorption spectrometry, but is dramatically lower than that from other reported electrochemical analysis methods. This simple and economic approach opens up a new window for the portable, quick, and ultra-sensitive detection of lead ions.
TL;DR: High-affinity anti-abrin-a monoclonal and polyclonal antibodies were used to develop a sandwich immunochromatographic assay and silver enhancement technology was used to further increase the sensitivity.
TL;DR: A DNA aptamer with high affinity and specificity to ochratoxin A was conjugated to a coupling gel and used as sorbent for the preparation of solid phase extraction (SPE) columns that could be re-used up to five times without any loss of performance.
TL;DR: The whole procedure showed to be conveniently fast, efficient and economical for extraction of fluoxetine from environmental and biological samples.
TL;DR: In this article, a functionalized carbon nanotubes paste electrode modified with cross-linked chitosan was used for the determination of trace amounts of cadmium(II) and mercury (II) by linear anodic stripping voltammetry.
TL;DR: Using ZnO quantum dots as electrochemical and fluorescent labels, a sandwich-type sensitive immunoassay was developed to detect carbohydrate antigen 19-9 which is a preferred label for pancreatic cancer.
TL;DR: Application of the developed method to the analysis of spiked Milli-Q, mineral, tap, and wastewater samples resulted in good recoveries values, with relative standard deviation values lower than 7.7% in all cases.
TL;DR: The optimized and validated HPLC-ECD method was successfully applied for the determination of the abovementioned compounds in human plasma and erythrocytes and will be quite suitable for the determined profile of ascorbic acid and aminothiols in oxidative stress and other basic research studies.
TL;DR: In this article, a high-performance liquid chromatographic method with diode-array detection (HPLC-DAD) was optimized and validated for determination of tetracyclines (TCs) residue in chicken meat and liver through evaluating each step of various methods.
TL;DR: The LC/MS method and associated isotope tracer techniques should be broadly applicable to investigating fatty acid metabolism, with the observed pattern consistent with Ras leading to enhanced activity of ELOVL4 or an enzyme with similar catalytic activity.
Abstract: We present a liquid chromatography/mass spectrometry (LC/MS) method for long-chain and very-long-chain fatty acid analysis and its application to 13C-tracer studies of fatty acid metabolism. Fatty acids containing 14 to 36 carbon atoms are separated by C8 reversed-phase chromatography using a water–methanol gradient with tributylamine as ion pairing agent, ionized by electrospray and analyzed by a stand-alone orbitrap mass spectrometer. The median limit of detection is 5 ng/mL with a linear dynamic range of 100-fold. Ratios of unlabeled to 13C-labeled species are quantitated precisely and accurately (average relative standard deviation 3.2% and deviation from expectation 2.3%). In samples consisting of fatty acids saponified from cultured mammalian cells, 45 species are quantified, with average intraday relative standard deviations for independent biological replicates of 11%. The method enables quantitation of molecular ion peaks for all labeled forms of each fatty acid. Different degrees of 13C-labeling...
TL;DR: The present work describes the development of a sensitive and highly selective innovative method for the simultaneous detection of six fluoroquinolone antimicrobials in water samples using for the first time tailor-made molecularly imprinted microspherical polymer particles prepared via precipitation polymerization.
Abstract: The present work describes the development of a sensitive and highly selective innovative method for the simultaneous detection of six fluoroquinolone (FQ) antimicrobials (enrofloxacin, ciprofloxacin, norfloxacin, levofloxacin, danofloxacin, and sarafloxacin) in water samples. This detection is based on online solid phase extraction, coupled to liquid chromatography (LC), using for the first time tailor-made molecularly imprinted microspherical polymer particles prepared via precipitation polymerization. Various parameters affecting the extraction efficiency of the polymer have been optimized to reduce nonspecific interactions and to achieve selective uptake of the antibiotics from real samples. The method shows good recoveries ranging between 62% and 102% (V = 25 mL) for the different FQs tested and excellent interday and intraday precision with relative standard deviation (RSD) values between 2−5% and 2−6%, respectively. The detection limits were between 1−11 ng L−1 (drinking water) and 1−12 ng L−1 (fis...
TL;DR: The presented method, solid-phase extraction combined with dispersive liquid-liquid microextration (SPE-DLLME), had higher selectivity than SPE method and was successfully applied to the determination of CLB in tissue samples.
TL;DR: In this paper, a highly sensitive and selective method is proposed for colorimetric detection of copper ions using 4-mercaptobenzoic acid (4-MBA) modified silver nanoparticles (AgNPs).
TL;DR: The assay results of heavy metals in wastewater with the proposed method were in acceptable agreement with the atomic absorption spectroscopy method.