Showing papers on "Calibration curve published in 2008"
TL;DR: In this paper, the authors evaluated the ECH 2 O sensors for measurement of soil moisture content, bulk electrical conductivity (EC b ), and temperature across a range of soils, across a measurement frequency between 5 and 150MHz.
309 citations
TL;DR: In this article, a systematic approach based on the application of Fourier transform infrared spectrophotometry (FTIR) was taken, in order to quantitatively analyze the corrosion products formed in the secondary cycle of pressurized water reactors (PWR).
275 citations
Abstract: This article provides a critical overview of current methods to quantify essential oil components. The fields of application and limits of the most popular approaches, in particular relative percentage abundance, normalized percentage abundance, concentration and true amount determination via calibration curves, are discussed in detail. A specific paragraph is dedicated to the correct use of the most widely used detectors and to analyte response factors. A set of applications for each approach is also included to illustrate the considerations.
165 citations
TL;DR: LIB spectra of different water samples having varying concentration of Cr have been recorded by using liquid jet configuration and it is found that calibration curve for Cr II (283.5 nm) atomic line is the best in terms of the Limit of detection (LOD) which is found to be 30 ppm.
135 citations
TL;DR: In this article, a wood slice was used as a liquid absorber to transform liquid sample analysis to solid sample analysis using LIBS, and the results showed that high detection sensitivity and good reproducibility can be achieved with this approach.
124 citations
TL;DR: The absolute calibration of photostimulable image plates (IPs) used as proton detectors is presented and a calibration curve is presented that enables retrieving the proton number from the IP signal.
Abstract: In this paper, the absolute calibration of photostimulable image plates (IPs) used as proton detectors is presented. The calibration is performed in a wide range of proton energies (0.5-20 MeV) by exposing simultaneously the IP and calibrated detectors (radiochromic films and solid state detector CR39) to a source of broadband laser-accelerated protons, which are spectrally resolved. The final result is a calibration curve that enables retrieving the proton number from the IP signal.
103 citations
TL;DR: In this paper, a simple and robust calibration method for ECH2O EC-5 sensors is proposed, where the effect of sensor characteristics is lumped into the empirical parameter α in the two-point α-mixing model.
Abstract: [1] Recently improved ECH2O soil moisture sensors have received significant attention in many field and laboratory applications. Focusing on the EC-5 sensor, a simple and robust calibration method is proposed. The sensor-to-sensor variability in the readings (analog-to-digital converter (ADC) counts) among 30 EC-5 sensors was relatively small but not negligible. A large number of ADC counts were taken under various volumetric water contents (θ) using four test sands. The proposed two-point α-mixing model, as well as linear and quadratic models, was fitted to the ADC – θ data. Unlike for conventional TDR measurements, the effect of sensor characteristics is lumped into the empirical parameter α in the two-point α-mixing model. The value of α was fitted to be 2.5, yielding a nearly identical calibration curve to the quadratic model. Errors in θ associated with the sensor-to-sensor variability for the two-point α-mixing model were ±0.005 cm3 cm−3 for dry sand and ±0.028 cm3 cm−3 for saturated sand. In the validation experiments, the highest accuracy in water content estimation was achieved when sensor-specific ADCdry and ADCsat were used in the two-point α-mixing model. Assuming that α = 2.5 is valid for most mineral soils, the two-point α-mixing model only requires the measurement of two extreme ADC counts in dry and saturated soils. Sensor-specific ADCdry and ADCsat counts are readily measured in most cases. Therefore, the two-point α-mixing model (with α = 2.5) can be considered as a quick, easy, and robust method for calibrating the ECH2O EC-5 sensor. Although further investigation is needed, the two-point α-mixing model may also be applied to calibrating other sensors.
99 citations
TL;DR: The Bayesian approach defined in this study allowed for the estimation of DNA concentrations from environmental samples using absolute standard curves generated by real-time qPCR.
Abstract: In real-time quantitative PCR studies using absolute plasmid DNA standards, a calibration curve is developed to estimate an unknown DNA concentration. However, potential differences in the amplification performance of plasmid DNA compared to genomic DNA standards are often ignored in calibration calculations and in some cases impossible to characterize. A flexible statistical method that can account for uncertainty between plasmid and genomic DNA targets, replicate testing, and experiment-to-experiment variability is needed to estimate calibration curve parameters such as intercept and slope. Here we report the use of a Bayesian approach to generate calibration curves for the enumeration of target DNA from genomic DNA samples using absolute plasmid DNA standards. Instead of the two traditional methods (classical and inverse), a Monte Carlo Markov Chain (MCMC) estimation was used to generate single, master, and modified calibration curves. The mean and the percentiles of the posterior distribution were used as point and interval estimates of unknown parameters such as intercepts, slopes and DNA concentrations. The software WinBUGS was used to perform all simulations and to generate the posterior distributions of all the unknown parameters of interest. The Bayesian approach defined in this study allowed for the estimation of DNA concentrations from environmental samples using absolute standard curves generated by real-time qPCR. The approach accounted for uncertainty from multiple sources such as experiment-to-experiment variation, variability between replicate measurements, as well as uncertainty introduced when employing calibration curves generated from absolute plasmid DNA standards.
83 citations
TL;DR: According to presented results APs can be advantegously used for "easy" pesticides determination and TPP normalization provided slightly better results than the use of absolute peak areas measurements on the contrary to HEPT.
75 citations
TL;DR: Compared to the time-consuming conventional microscopic approach, the application of FALS for sizing bacterial biovolume could be a very promising tool being completed in few minutes, simultaneously to the enumeration of bacteria during the flow cytometric analysis.
66 citations
TL;DR: In this article, a sensitive preconcentration methodology for Cd determination at trace levels in water samples was developed, which was successfully applied to the determination of Cd in river and tap water samples.
TL;DR: In this paper, a simple and fast method for the determination of cyclophosphamide in human plasma samples was developed, which reduced the sample handling and the analysis time by several folds compared to liquid chromatography and UV detection.
Abstract: The aim of the present investigation was to develop a simple and fast method for the determination of cyclophosphamide in human plasma samples. Microextraction in packed syringe (MEPS) was used as an online rapid sample preparation method, followed by liquid chromatography with tandem mass spectrometry (LC‐MS‐MS) for the quantification of cyclophosphamide. The new method reduced the sample handling and the analysis time by several folds compared to liquid chromatography and UV detection. The limit of detection (LOD) was 0.005 µg/mL and the lower limit of quantification was 0.5 µg/mL. The accuracy of the quality control (QC) samples ranged from 95 to 106%. The inter‐day variation was within the range 5–9% while the intra day variation was between 1–5%. The calibration curve in plasma was constructed within the concentration range 0.5–150 µg/mL. The regression correlation coefficient (r) was ≥0.99 for all runs. The limit of detection improved by 100 time using MEPS‐LC‐MS/MS (0.005 µg/mL) compared t...
TL;DR: In this article, a novel method, dispersive liquid-liquid microextraction coupled with liquid chromatography-variable wavelength detector (LC-VWD), has been developed for the determination of chloramphenicol (CAP) in honey.
Abstract: A novel method, dispersive liquid–liquid microextraction coupled with liquid chromatography-variable wavelength detector (LC-VWD), has been developed for the determination of chloramphenicol (CAP) in honey. A mixture of extraction solvent (30 μL 1,1,2,2-tetrachloroethane) and dispersive solvent (1.00 mL acetonitrile) were rapidly injected by syringe into a 5.0 mL real sample for the formation of cloudy solution, the analyte in the sample was extracted into the fine droplets of C2H2Cl4. After extraction, phase separation was performed by centrifugation and the enriched analyte in the sedimented phase was determined by LC-VWD. Some important parameters, such as the kind and volume of extraction solvent and dispersive solvent, extraction time, sample solution pH, sample volume and salt effect were investigated and optimized. Under the optimum extraction condition, the method yields a linear calibration curve in the concentration range from 3 to 2,000 μg kg−1 for target analyte. The enrichment factor for CAP was 68.2, and the limit of detection (S/N = 3) were 0.6 μg kg−1. The relative standard deviation (RSD) for the extraction of 10 μg kg−1 of CAP was 4.3% (n = 6). The main advantages of method are high speed, high enrichment factor, high recovery, good repeatability and extraction solvent volume at μL level. Honey samples were successfully analyzed using the proposed method.
TL;DR: In this paper, a flow injection system was developed for on-line sorbent extraction preconcentration and flame atomic absorption spectrometric determination of cadmium in natural water samples.
Abstract: A flow injection system was developed for on-line sorbent extraction preconcentration and flame atomic absorption spectrometric determination of cadmium in natural water samples. The non-charged cadmium complex with diethyl-dithiophosphate (DDPA) was formed on-line in 0.1 mol L−1 HNO3 and retained on the hydrophobic poly-chlorotrifluoroethylene (PCTFE) sorbent material. The adsorbed complex was eluted with isobutyl methylketone (IBMK) and injected directly into the nebulizer via a flow compensation unit. All major chemical and flow parameters affecting the complex formation adsorption and elution as well as interference were studied and optimized. By processing 2.4 mL of sample, the enhancement factor was 39 and the sampling frequency was 50 h−1. For 30 s preconcentration time the detection limit was 0.3 µg L−1 and the relative standard deviation at 5.0 µg L−1 Cd concentration level was 2.9%. The calibration curve was linear in the range 0.8–40.0 µg L−1. The accuracy of the method was estimated by analyzing a certified reference material NIST-CRM 1643d (Trace elements in water). Good recoveries were obtained for spiked natural-water and waste-water samples.
TL;DR: Three separate calibration curves were developed to describe the solid phase distribution found on drug-polymer coated stents using Raman spectroscopy to differentiate each component found in the CYPHER Sirolimus-eluting Coronary Stent.
Abstract: Raman spectroscopy was used to differentiate each component found in the CYPHER Sirolimus-eluting Coronary Stent The unique spectral features identified for each component were then used to develop three separate calibration curves to describe the solid phase distribution found on drug-polymer coated stents The calibration curves were obtained by analyzing confocal Raman spectral depth profiles from a set of 16 unique formulations of drug-polymer coatings sprayed onto stents and planar substrates The sirolimus model was linear from 0 to 100 wt % of drug The individual polymer calibration curves for poly(ethylene-co-vinyl acetate) [PEVA] and poly(n-butyl methacrylate) [PBMA] were also linear from 0 to 100 wt % The calibration curves were tested on three independent drug-polymer coated stents The sirolimus calibration predicted the drug content within 1 wt % of the laboratory assay value The polymer calibrations predicted the content within 7 wt % of the formulation solution content Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra from five formulations confirmed a linear response to changes in sirolimus and polymer content
TL;DR: In this article, an optical sensor was designed for the determination of zinc by spectrophotometry, which was made by immobilizing Zincon as an ion pair with methyltrioctylammonium ion on triacetylcellulose membrane.
Abstract: An optical sensor has been designed for the determination of zinc by spectrophotometry. The sensing membrane is made by immobilizing Zincon as an ion pair with methyltrioctylammonium ion on triacetylcellulose membrane. In the present of Zn2+ ions in ammonia/ammonium chloride buffer at pH 9 the color of the membrane changes from purple to blue. The calibration curve was linear in the range of 0.76–30.60 μM of Zn2+ ion with a limit of detection 0.16 μM (10.5 ng ml−1). The response time of the optode was about 10–12 min, depending on the concentration of Zn2+. The sensor can readily be regenerated with hydrochloric acid solution. This optode is stable and could be stored under water for three weeks without reagent leaching. The relative standard deviation for seven replicate measurements of 7.65 and 15.30 μM Zn2+ was 3.09 and 2.82%, respectively. The sensor was successfully applied to the determination of zinc in powdered milk and hair samples.
TL;DR: The proposed analytical method has been applied to the analysis of commercial physiological saline solutions in order to check the presence of phthalates and to determine their concentration.
Patent•
25 Feb 2008TL;DR: In this article, an initial calibration matrix of sampled analyte concentrations is modified using mean-centering techniques and selection of low and high analyte concentration spectra to produce a two-point calibration.
Abstract: The present subject matter is direct to methodologies for calibrating data obtained from an optical analysis system. An initial calibration matrix of sampled analyte concentrations is modified using mean-centering techniques and selection of low and high analyte concentration spectra to produce a two-point calibration. A modified calibration matrix is produced by generating a non-linear calibration matrix by multiplying the initial calibration matrix by the two-point calibration. In an alternate embodiment, an initial multivariate optical element design is modified by iteratively adjusting the design based on standard error of calibration determination based on non-linerly fitted functions.
TL;DR: To assess the performance of this VOC GC/MS system, a gas mixture containing numerous VOCs at sub-ppb (v/v) level served as the ambient air sample to assess the improvement in analytical precision and accuracy.
TL;DR: In this article, a method for tracking the three-dimensional position and computing the three velocity components of a micro-particle using information encoded in the ring structure of the particle image is introduced.
Abstract: A method for tracking the three-dimensional position and computing the three velocity components of a micro-particle using information encoded in the ring structure of the particle image is introduced. The proposed technique can be employed in most existing micro-particle image velocimetry systems without any additional hardware and details of the optical train are not required. The technique utilizes a set of calibration images of a particle at various known distances from the focal plane (in the out-of-plane direction) in order to create a calibration curve. The calibration curve, which relates the radius of the outermost ring to the distance of the particle from focus is used to deduce the out-of-plane location of particles in experimental images. From successive images the particle's velocity is computed. The in-plane particle velocity is deduced from traditional particle tracking methods.
TL;DR: Although the controlled growth of a CNT is difficult, it is shown that an NTFET biosensor can be easy calibrated using the proposed calibration method, regardless of the CNT channel structures.
Abstract: An easy calibration method based on the Langmuir adsorption theory is proposed for a carbon nanotube field-effect transistor (NTFET) biosensor. This method was applied to three NTFET biosensors that had approximately the same structure but exhibited different characteristics. After calibration, their experimentally determined characteristics exhibited a good agreement with the calibration curve. The reason why the observed characteristics of these NTFET biosensors differed among the devices was that the carbon nanotube (CNT) that formed the channel was not uniform. Although the controlled growth of a CNT is difficult, it is shown that an NTFET biosensor can be easy calibrated using the proposed calibration method, regardless of the CNT channel structures.
TL;DR: A new rapid and sensitive FI method is reported for spectrophotometric determination of trace chromium(VI) in electroplating waste water, based on the reaction of Cr( VI) with sodium diphenylamine sulfonate in acidic medium to form a purple complex.
TL;DR: In this paper, the particle acidity of secondary organic aerosol (SOA) created from ozonolysis of α-pinene in the presence of acidic inorganic seed aerosols was investigated using an indoor Teflon film chamber.
Abstract: The particle acidity of secondary organic aerosol (SOA) created from ozonolysis of α-pinene in the presence of acidic inorganic seed aerosols was investigated using an indoor Teflon film chamber. Colorimetry integrated with a reflectance UV-Visible spectrometer was used for the first time to dynamically measure the aerosol acidity over time. An external calibration curve was produced based on the correlation between the proton mass (ng) collected on the filter, which was impregnated with metanil yellow, and the absorbance of the reflectance UV-Visible spectra for the protonated and the unprotonated metanil yellow on the filter. Using this calibration curve, the particle acidity of the submicron acidic sulfate aerosol coated with SOA was measured from the reflectance UV-Visible spectra of filter samples. The colorimetric analysis requires a short sampling time (less than 2 m) for SOA studies using the laboratory Teflon film chamber and eliminates extraction of the filter sample with water. Results show tha...
TL;DR: The proposed reversed flow injection colourimetric procedure, based on the reaction between iron(III) with chlortetracycline, resulting in an intense yellow complex with a suitable absorption at 435nm, has been satisfactorily applied to the determination of iron( III) in natural waters.
TL;DR: In this article, a solvent extraction spectrophotometric method for the determination of cationic surfactants (CS) in industrial wastewaters was proposed, which is based on the introduction of Patent Blue V as an anionic dye, and the formation of an ion pair association with CS in chloroform under the studied extraction conditions.
Abstract: Patent Blue V has been applied in a solvent extraction spectrophotometric method for the determination of cationic surfactants (CS) in industrial wastewaters. The method is based on the introduction of Patent Blue V as an anionic dye, and the formation of an ion pair association with CS in chloroform under the studied extraction conditions. The maximum wavelength of absorption for the ion pair is located at 627 nm, and a molar absorption coefficient of higher than 3.6 × 105 l mol−1 cm−1 was obtained. The calibration curve was linear between 0 and 5.48 × 10−6 M, and exhibited a significant coefficient of correlation. Based on the calculated values for the relative standard deviation (%) over the studied concentration range, the method was found to be highly sensitive, and the deduced limit of detection for the method was found to be very low (8.6 × 10−8 M of CTAB). It was also found that a washing step was necessary for the organic extract in order to remove interferences caused by foreign ions and species present in unknown samples. To validate this method, the procedure was used to determine the CS contents of samples collected from textile industry wastewaters in the Algiers region. The results obtained showed good agreement for the proposed method.
TL;DR: Compared the fit of a quadratic, cubic and 4-parameter logistic model for highly-replicated calibration curves across seven assays used for quantifying transgenic proteins in commercial crops indicates that it is typically undesirable to include zero-concentration data when modeling these curves over the quantitative range.
TL;DR: In this paper, the SEC analysis of polyamide11 and polyamide-12 can be conducted free of association and aggregation phenomena when hexafluoroisopropanol + 0.05 mol/L potassium trifluoroacetate is used as the mobile phase.
TL;DR: The study of the influence of the bone matrix showed that the addition of 25% ground bone to graphite powder with introduced impurities did not affect the analytical signal of elements in the spectral excitation in a two-jet plasma.
Abstract: This paper describes an analytical method for trace element determination in bone tissues. The study of the influence of the bone matrix showed that the addition of 25% ground bone to graphite powder with introduced impurities did not affect the analytical signal of elements in the spectral excitation in a two-jet plasma. On basis of these investigations a method for direct multielement analysis of bone tissues was suggested. The sample preparation procedure consisted in mixing powdered bone (particle size 30 μm or less) with a spectroscopic buffer (graphite powder plus NaCl) in ratio 1:3 or to a greater extent depending on the analyte concentration. Reference samples based on graphite powder were used for construction of calibration curves. The NaCl concentration in analyzed and calibration samples was 15 wt%. The effect of particle size was revealed from the determination of Ba, Sr, and Mg. To eliminate this effect, treatment of the samples with nitric acid was proposed. The validation of the technique was confirmed by comparison of the analysis results of a bone sample with those obtained by inductively coupled plasma atomic emission spectrometry after wet acid digestion. The limits of detection estimated for 20 elements were the following (μg g-1): 0.1 (Ag), 1.0 (Al), 1.0 (Ba), 0.1 (Be), 1.2 (Bi), 0.4 (Cd), 1.0 (Co), 0.2 (Cu), 0.6 (Cr), 1.9 (In), 2 (Fe), 0.3 (Ga), 0.4 (Mn), 0.4 (Mo), 0.7 (Ni), 1.0 (Pb), 0.7 (Sn), 0.8 (Tl), 5 (Sr), 1.0 (Zn).
TL;DR: FFDM systems provide a quantitative output, and the calibration quantities presented here may be used for data acquired on similar FFDM systems and are in agreement with those predicted numerically.
Abstract: Breast density is a significant breast cancer risk factor. Currently, there is no standard method for measuring this important factor. Work presented here represents an essential component of an ongoing project that seeks to determine the appropriate method for calibrating (standardizing) mammography image data to account for the x-ray image acquisition influences. Longer term goals of this project are to make accurate breast density measurements in support of risk studies. Logarithmic response calibration curves and effective x-ray attenuation coefficients were measured from two full field digital mammography (FFDM) systems with breast tissue equivalent phantom imaging and compared. Normalization methods were studied to assess the possibility of reducing the amount of calibration data collection. The percent glandular calibration map functional form was investigated. Spatial variations in the calibration data were used to assess the uncertainty in the calibration application by applying error propagation analyses. Logarithmic response curves are well approximated as linear. Measured effective x-ray attenuation coefficients are characteristic quantities independent of the imaging system and are in agreement with those predicted numerically. Calibration data collection can be reduced by applying a simple normalization technique. The calibration map is well approximated as linear. Intrasystem calibration variation was on the order of four percent, which was approximately half of the intersystem variation. FFDM systems provide a quantitative output, and the calibration quantities presented here may be used for data acquired on similar FFDM systems.
TL;DR: A simple flow injection system using three 3-way solenoid valves as an electric control injection valve and with a simple home-made chloride ion selective electrode based on Ag/AgCl wire as a sensor for determination of water soluble chloride in admixtures and aggregates for cement has been developed.