Showing papers on "Calibration curve published in 1995"

Calibration method and apparatus for optical scanner

Abstract: A calibration method and device for a fluorescence spectrometer which uses fluorescence from a homogeneous solid state standard (45) as the source of calibration fluorescence and wherein the solid state standard (45) may be built into the optical scanner (48) and the calibration may be automatically performed as a routine step when using the optical scanner (48). A gold standard (41) establishes fluorescent units, and the fluorescence spectrometer is calibrated by reference to calibration standards (45), such as calibration rubies, which are themselves rated against the gold standard and built into the fluorescence spectrometer to provide an unchanging reference to the gold standard and by which simultaneous calibration of two or more channels of a multi-channel fluorescence spectrometer may be accomplished.

Quantitative bioanalysis using matrix-assisted laser desorption/ionization mass spectrometry

Abstract: The application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for quantitative analysis was investigated with the use of internal standards. Three peptides/proteins in the mass range 1000–12000 were tested and the effect of various internal standards was evaluated. Horse cytochrome c was used as an internal standard for bovine cytochrome c, melittin for renin and an undecapeptide B analogue was employed as an internal standard for the decapeptide A. A linear response was found between the measured peak height ratio and the applied amount of analyte when an appropriate internal stanard was used. The quantitative abilities of MALDI-MS were finally applied to the determination of the drug amperozide in plasma. The biological samples were prepared for analysis using liquid–liquid extraction prior to MALDI-MS. A linear calibration graph was obtained using the 13C4 stable isotopically labelled amperozide as an internal standard.

Capillary Enzyme Immunoassay with Electrochemical Detection for the Determination of Atrazine in Water

Abstract: A capillary enzyme immunoassay with electrochemical detection has been developed for the determination of atrazine in water. The assay is based on competitive binding between atrazine and alkaline phosphatase-labeled atrazine for a limited number of antibody binding sites. The antibody is attached covalently to a modified capillary surface. The enzymatic product (p-aminophenol) is detected by amperometric flow injection analysis. The calibration curve for atrazine has a linear range of 0.10-10.0 μg/L and a detection limit of 0.10 μg/L. An assay including six standards can be done in less than 60 min. Intra- and inter-assay precisions at 0.1 and 5.0 μg/L are 9 and 8% and 6 and 10%, respectively. Recoveries of added atrazine from commercial bottled water, tap water, and Ohio River water at 0.50 and 5.0 μg/L range from 100 to 115%. Simple filtration is the only step needed for sample cleanup

Concentration controlling method and a substate treating apparatus utilizing same

Abstract: Calibration curve data is collected by measuring transmitted light intensities of a treating solvent while solvent temperature is varied. Also measured are a standard transmitted light intensity (transmitted light intensity of a standard treating solution prepared at a predetermined concentration and temperature) and a reference transmitted light intensity (transmitted light intensity of the solvent). Estimated transmitted light intensity of the solvent when its temperature is the same as that of the standard treating solution, is derived from the temperature of the standard treating solution and the calibration curve data stored. A correction factor is computed from a ratio between the reference transmitted light intensity and estimated transmitted light intensity. Then, transmittance of the standard treating solution (standard transmittance) is computed from the standard transmitted light intensity, reference transmitted light intensity and a correction factor. Subsequently, transmitted light intensity of a treating solution for actual use in treating substrates (sample transmitted light intensity) is measured. A sample transmittance of this treating solution is derived from the sample transmitted light intensity, reference transmitted light intensity and a correction factor. Concentration of the treating solution is controlled based on the standard and sample transmittance.

Method for calibrating a network analyzer according to the seven-term principle

Abstract: A method calibrates a network analyzer having two test ports and at least four measuring locations by successive measurement of the transmission and reflection parameters at three calibration standards successively connected in arbitrary sequence between the two test ports according to the seven-term principle. A first calibration measurement is implemented at an electrical line whose characteristic impedance is known and whose electrical propagation constant may be unknown and complex. Second and third calibration measurements are then respectively implemented at a two-port that is connected between the test ports and is constructed of concentrated components. The electrical propagation constant of the line and correction values that are taken into consideration in following object measurements are calculated from these measured values.

Método rápido para la determinación de escualeno en aceites vegetales

Abstract: A simple and rapid analytical method for the quantification of squalene in vegetable oils is described. The method consists of a cold alkaline methylation of the oil sample diluted with hexane followed by quantitation by gas chromatography with internal standard. A calibration curve obtained using different standard solutions, and coefficients of variation for three different samples with high, medium and low content of squalene, are reported.

On‐line conversion monitoring through ultrasound propagation velocity measurements in emulsion polymerization

Abstract: An on-line sensor for estimating conversion from measurements of ultrasound propagation velocity in emulsion polymerizations has been developed. The sensor does not require a sampling circuit, because it can be directly plugged in the reacting mixture. The performance of the sensor has been tested by comparison with off-line gravimetric measurements of conversion under various operating conditions. These include the homopolymerization of methyl methacrylate and vinyl acetate, with different values of the monomer to water ratio and the initial concentrations of emulsifier and initiator. The results obtained using either an empirical calibration curve or a suitable a priori model indicate excellent reliability of the sensor with somewhat lower accuracy at low conversion values, i.e., when monomer droplets are present. © 1995 John Wiley & Sons, Inc.

Analysenmethoden für Alkylpolyglucoside (Teil 1) / Analytical methods for alkylpolyglucosides

Abstract: This paper proposes a method for the colorimetric determination of alkylpolyglucosides (APGs) based on a reaction with the Anthrone reagent. The calibration curve shows a linear relationship between concentration and absorbance from 30 μg to 150 μg APG/mL sample. The relative standard deviation is 1% (48.5 μg APG/mL, n = 6). The calibration curve is stable and can be used for determinations for several months. Cellulose derivatives interfere with the determination. Substances which are usually present in formulations do not interfere. For some APG-containing formulations commercially available the concentration of APGs is determined.

The "Amsterdam Castle": A Case Study of Wiggle Matching and the Proper Calibration Curve

Abstract: We have performed a high-precision C-14 wiggle-matching study on two oak beams from the ''Castle of Amsterdam''. These beams are also dated by dendrochronology. Our two dating methods can only be made consistent using the recommended calibration curve (1986) instead of the revised one (1993).

Determination of Se in human serum by AAS using electrochemical atomization with longitudinal Zeeman-effect background correction or low injection hydride generation

Abstract: Two methods are described for the determination of selenium in human serum by atomic absorption spectrometry (AAS) using either electrothermal atomization (ET) with longitudinal Zeeman-effect background correction or flow injection (FI) hydride generation (HG). ETAAS allowed the direct determination of selenium in an appropriately diluted serum sample (1 :10). Serum selenium was stabilized prior to atomization by a matrix modifier containing 1500 mg/L Pd and 1000 mg/L Mg nitrate. Calibration was performed by the method of standard addition. FI-HGAAS required a nitric/perchloric acid digestion procedure prior to analysis. Calibration was performed using a calibration curve in 1 mol/L hydrochloric acid. Both methods provided analytical data for a reference serum sample which was in close agreement with the certified value. Precision (range 2-5%) and sensitivity (∼50 pg) were comparable for both methods. However, ETAAS demonstrated a lower relative limit of detection, 6.5 μg/L, compared to FI-HGAAS with 11.8 μg/L. Accurate determination of low selenium levels in a small sample volume (100 μL serum sample) was obtained with both methods.

Analysis of precious metal alloys by radio frequency glow discharge atomic emission spectrometry

Abstract: Analytical figures of merit for trace elements in gold, platinum, silver, and sterling silver alloys have been evaluated using radio frequency glow discharge atomic emission spectrometry (rf-GD-AES). Results presented here illustrate rapid plasma stabilization times (less than1 min), short-term precision of less than1% RSD, and long-term stability of less than5% RSD for major element lines, which are characteristic of the rf-GD plasma. Calibration curves linear over 2-3 orders of magnitude are possible with a general improvement in linearity by ratioing the signal to an internal standard. It is found that the novel use of the signal background as an internal standard is an excellent means for improving analytical accuracy. Similarities in sputtering rates allow the use of multimatrix calibration, emphasizing the fact that there are negligible matrix effects within glow discharge plasmas. Limits of detection on the parts per billion level are recorded for many trace species in the precious metals. The figures of merit reported here indicate that rf-GD-AES is well suited for the precise, accurate, and sensitive analysis of precious metals.

Constructing a bootstrap confidence interval for the unknown concentration in radioimmunoassay

Abstract: The statistical problem associated with radioimmunoassay is known as calibration or inverse regression. In the current study, we propose a bootstrap procedure aimed at constructing an inverse confidence interval for the univariate calibration problem. The calibration curve is estimated either parametrically or by non-parametric regression. The methods are illustrated by an example.

High temperature thermal field‐flow fractionation of polyethylene and polystyrene

Abstract: In this paper the high-temperature thermal field flow fractionation method is exploited for the analysis of polyethylene (PE). The experimental apparatus set-up, obtained by simply modifying a commercial instrument, is presented. The numerical procedure for deriving retention calibration plot versus molecular weight is discussed with reference to the specific polymer-solvent pair, PE-o-dichlorobenzene (ODCB), here employed. Different methods for computing the physicochemical data set of the solvent, necessary for calibration, are compared. The selectivity of the checked PE-ODCB system proves comparable with respect to the values currently found in thermal field-flow fractionation (ThFFF) analysis. Differences are found between PE and polystyrene (PS) analysis in the same solvent. The conditions for high temperature ThFFF operation in PE analysis and their advantages are discussed with respect to the standard SEC technique for PE, PS, and PE-PS copolymer analysis. Molecular weight distributions obtained by ThFFF of two PE commercial samples agree with those obtained by SEC

In search of the ultimate experiment for quantitative depth profile analysis in glow discharge optical emission spectrometry. Part I: Calibration curves

Abstract: This is the first part of our search for an experiment that will show definitively which is the best method for quantitative glow discharge optical emission spectrometry (GDOES). Three empirical methods for producing quantitative depth profiles from GDOES data are examined: the SIMR method, the IRSID method and the most recent BHP method. All three methods give worthwhile quantitative depth profiles of thin films and coated materials. The first two methods assume that pressure does not have a significant effect on emission yield, while the third method assumes that pressure is the only significant parameter affecting emission yield. The different approaches therefore imply very different physical processes inside the lamp and it is essential for further development of quantitative GDOES that the best approach be determined. Depth profiling in GDOES is, in principle, simply bulk analysis repeated over and over as a function of depth. The three methods are therefore tested here in their ability to do bulk calibration in a range of steels and zinc–aluminium alloy standards, all at constant current. All methods worked well for steel, while the best calibration curves in zinc–aluminium alloys were obtained with pressure-corrected IRSID and SIMR methods or a voltage-corrected BHP method. The results suggest that emission yields depend on both voltage and pressure (and presumably current, which was not tested here in Part I).

Determination of Oltipraz in serum by high-performance liquid chromatography with optical absorbance and mass spectrometric detection

Abstract: Three methods have been developed for the analysis of Oltipraz in serum. A method suitable for routine use employs spiking with a homologous internal standard, off-line solid-phase extraction, high-performance liquid chromatographic separation, and optical absorbance detection at 450 nm. Method detection limit is about 1 ng/ml. A second method, less susceptible to bias from co-eluting interferences, uses a stable isotope-labeled internal standard, similar extraction and separation, and detection by thermospray mass spectrometry. Method detection limit is about 0.2 ng/ml. A third method was developed which can be used without specially synthesized internal standards. It uses on-line solid-phase extraction, with quantification by comparison with external standards. Method detection limit is about 3 ng/ml. Good agreement was observed between these methods and with similar and different methods run in other laboratories. Calibration curves were linear over the entire range which was investigated, i.e., up to 500 ng/ml. Coefficients of variation were similar for all three methods, being about 5%.

In vivo spectroscopic properties of the fluorescent ph indicator biscarboxyethyl carboxyfluorescein

Abstract: Transcutaneous detection of fluorescence from an injection of the pH-sensitive probe biscarboxyethyl carboxyfluorescein (BCECF) has been used to monitor plasma pH in conscious animals. The fluorescence signal must be calibrated with reference to a standard curve. This standard, calibration curve has been achieved using in vitro methods. Here it is shown that temperature influences the calibration curve determination in vitro and hence influences the pH determined from transcutaneous measurements. Two calibration curves have been obtained, one at room temperature (approximately 25 degrees C) and the other at 37 degrees C. At pH 7.01 the calibration curves intersect, so that, at more alkaline pH values, use of room temperature calibration data will lead to an overestimate of plasma pH. Below pH 7.01, plasma pH will be underestimated. Transcutaneous fluorescence spectra recorded from a mouse injected with BCECF are shown, indicating that baseline plasma pH was estimated about 0.3 pH units too high using room temperature calibration, and that the extent of acidification when the animal was allowed to breathe an atmosphere containing 15% CO2 was overestimated by 0.7 pH units. Additionally, it is shown that in vitro bovine serum albumin at concentrations comparable with albumin concentrations in vivo shifts the absorption, fluorescence excitation and emission spectra of BCECF. However, fluorescence spectra recorded in vivo show no such shift. The results indicate that in vitro calibration for transcutaneous fluorescence measurements in vivo can be misleading, and that in the case of pH measurement inattention to temperature can lead to spurious results.

Ultra-Trace Determination of Phosphate Ion Based on Filtration-Dissolution and Flow-through Spectrophotometric Measurement

Abstract: A sensitive spectrophotometric method for the determination of ultra-trace amounts of phosphate ion is proposed. The colored ion associate formed between molybdophosphate and Malachite Green (MG) was filtered through a tiny membrane filter (cellulose nitrate; poresize, 1.0μm; 9mm diameter), dissolved together with the membrane filter in 1cm(3) or less of Methyl Cellosolve; the absorbance of the solution was then measured at 627nm with a flow-through system equipped with an autosampler. The absorbance, the standard deviation and the relative standard deviation of the reagent blank were 0.0270, 0.0005 and 1.8%, respectively. A calibration graph was linear over the range from 0.018 to 1.0ng cm(-3) (1ppb) of phosphorus using 40cm(3) of sample solutions; the detection limit corresponding to two-times the standard deviation of the reagent blank was 3ppt of phosphorus. By using the proposed method, phosphate ion in pure water samples were determined.

Process for measuring analyte in sample

Abstract: The amount of an analyte in a sample derived from a living sample is measured by reacting the analyte with an excess of a substance having affinity for the analyte, followed by separation of complex by high pressure liquid chromatography and measurement using a linear calibration curve representing the peak area values associated with known concentrations of analyte.