Showing papers on "Calibration curve published in 1992"

A method for providing general calibration for near infrared instruments for measurement of blood glucose

Abstract: A method is disclosed for accurately providing general calibration of near-infrared quantitative analysis instruments for almost any individual user. The general calibration method comprises comparing an individual's near-infrared spectrum to a plurality of near-infrared spectral clusters. Each near-infrared spectral cluster has a set of calibration constants associated therewith. The calibration constants of the spectral cluster most closely associated with the individual spectra are used to custom calibrate the near-infrared analysis measurement instrument.

Calibration Transfer and Measurement Stability of Near-Infrared Spectrometers

Abstract: Near-infrared (NIR) spectroscopy has been widely accepted as a quantitative technique in which multivariate calibration plays an important role. The application of NIR to process analysis, however, has been largely limited by a problem identified as calibration transfer, the attempt to transfer a well-established calibration model from one instrument (e.g., located in the central laboratory) to another instrument of the same type (e.g., located on an industrial process). A calibration transfer method called piecewise direct standardization (PDS) is applied to a set of gasoline samples measured on two different NIR spectrometers. On the basis of the measurement of a small set of transfer samples on both instruments, a structured transformation matrix can be determined and applied to transform spectra between two instruments, enabling the transfer of calibration models. The effect of spectrum preprocessing on standardization is studied with the use of a set of gasoline samples. In a separate study, the day-to-day instrument variation as observed from the change in the polystyrene spectrum is related to the prediction of moisture, oil, protein, and starch content in corn samples, and then the possibility of using such generic standards to replace real samples in a transfer set is explored. In all cases, a standard error for prediction comparable to full set cross-validation is obtained through standardization.

Simulation of the mass response of the evaporative light-scattering detector

Abstract: A computer simulation model was developed to predict the response of the evaporative light scattering detector. Hereby, not only the nebulization, the evaporation, and the light scattering phenomenon were modeled, but moreover, the decreased efficiency of the detection process due to photomultiplier saturation was quantified and included in the model. The program allows one to calculate calibration curves corresponding to a given set of experimental conditions. Hereby, a single-point calibration is sufficient to obtain absolute peak areas. Besides the detector settings and the mobile-phase flow rate, the peak width was most decisive. The usefulness of the model was shown by comparing both experimental and simulated calibration curves obtained at various values of the gas pressure, mobile-phase flow rate, and peak width: very good fits were obtained under all experimental conditions. The simulation program elaborated enables one to investigate quantitatively the influence of all detector variables so that they can be optimized easily. Moreover, calibration curves corresponding to each peak within a chromatogram may be calculated, even for unknown compounds, thus allowing a reproducible and accurate quantitative estimation of all the compounds separated.

Measurement of protein

Abstract: PURPOSE:To rapidly measure protein with high accuracy without receiving the effect of the chelatable component in a specimen, in measuring protein by using a complex consisting of a metal and a dye and the shift of the absorption wavelength of the complex in the presence of protein, by measuring protein in the presence of polyhydric alcohol. CONSTITUTION:A dye and a metal are added to a solvent by predetermined amounts to form a complex and the pH of the complex solution is adjusted to prepare a reagent solution. This reagent solution and a specimen containing protein are mixed to prepare a sample solution to be measured. A specific amount of polyhydric alcohol is added to either one of the reagent solution, the specimen and the sample solution to be measured. After standing, the absorbancy after the shift of the absorption wavelength of the complex due protein is measured. The same operation is performed using a standard sample solution known in the conc. of protein and the absorbancy of a wavelength after shift is measured to form a calibration curve. The calibration curve and the absorbancy obtained using the specimen are compared each other to calculate the concn. of protein.

Quadrupole trap improved technique for ion isolation

Abstract: A method for isolating an ion in a QIT (1) employing values from a mass axis calibration chart to establish the maximum DAC value to scan to in order to scan out m(p)-1 and less during ramp up of RF trapping field while applying a specifically selected fixed supplemental frequency applied during said calibration; and employing values from the calibration curve to establish the DAC value to scan out m(p)+1 and greater during ramping down of RF trapping field, while applying a previously determined fixed broadband spectrum to the QIT end caps.

Bar coding calibration

Abstract: There is described a method of barcoding data needed to determine a calibration curve for a test element in an analyzer The process follows the steps of: a) ascertaining by statistical analysis the ranges of values for R that are possible for three given concentration values C1, C2 and C3, for a given assay, and assigning a high value H and a low value L for these ranges; b) calculating for a given lot of the given assay, a calibration curve that correlates the analyzer response to the concentration, c) determining the analyzer response R1, R2 and R3 from said calibration curve, that corresponds to the C1, C2 and C3 values; d) calculating the bar code value B1 for Ri of each of these R1, R2 and R3 from the equation: (2) Bi = (10n - 1)(Ri - Li)/ (Hi-Li) where Ri is R1, R2 or R3, and Li and Hi are the corresponding L and H values for that Xi; e) rounding Bi to the nearest integer;and f) supplying this value of Bi for each of Ri = R1, R2 or R3 in bar code form, using n-digit decimal numbers, so that only three sets of (10n) possibilities are needed to accurately pass along data corresponding to the calibration coefficients even though each of the three coefficients can vary by more than that which can be specified using 10n digits

Simultaneous Measurement of Velocity and Temperature of Water Using LDV and Fluorescence Technique

Abstract: A method of simultaneous measurement of velocity and temperature of water has been developed using a modified laser induced fluorescence of Rhodamine B The intensity of fluorescence decreased with temperature and its temperature with a coefficient of 32%/K The dimensionless calibration curve was not affected by laser intensity, concentration of Rhodamine B, laser wavelength and optical configuration Simultaneous measurement of velocity and temperature was made in a natural convection field

Fluid density and concentration measurement using noninvasive in situ ultrasonic resonance interferometry

Abstract: A method of noninvasively measuring the density of fluids contained within pipes, cans, tanks, and bottles has been developed. The container-fluid system is interrogated using an ultrasonic transducer. A second transducer is used to observe transmitted energy as the input frequency is swept through an appropriate range determined by the geometry. Resonance peaks are observed in the transmitted energy. The periodicity of the resonant peaks is determined by analyzing the response data using a fast Fourier transform. The technique is tested using known NaCl concentration standards within a stainless steel pipe. The concentration of unknown NaCl solutions is measured in situ with an accuracy of +or-0.15 M over a range of 0.4 to 3.4 M corresponding to an accuracy of +or-0.02 specific gravity (SG) units over a range of 1.000 to 1.134 SG units. >

Analysis of systematic errors in calibrating glass electrodes with H+ as a concentration probe

Abstract: Two different experimental methods for the calibration of glass electrodes for H+ concentration are analysed: strong acid—strong base titration and addition of the strong base or acid to the solvent. Possible systematic errors in acid or base concentrations used for calibration affect in a different way the linear relationship between the cell potential and the logarithm of the hydrogen ion concentration in each case. We have examined how such errors influence the slope of the calibration curve by using a programme that simulates the calibration procedure and we have compared this analysis with some experimental results previously obtained.

Quantitative Analysis of Surface Contaminations on Si Wafers by Total Reflection X-Ray Fluorescence

Abstract: A total reflection X-ray fluorescence (TRXRF) technique has been recently used to analyze metal contaminations on Si wafers. In this work, microdrop-contaminated Si wafers are used to make the calibration curves. Metal impurities in these wafers are shown to be condensed in a very small area near the center of the dropped area. To make the calibration curve, a relationship is derived between the intensity of the characteristic X-ray from metal impurities in the condensed area and that from the impurities uniformly distributed over the wafer surface. On the basis of this relationship, calibration curves for Fe, Ni, Cu and Zn are obtained.

Intensity Calibration Curves for Bragg-Brentano X-Ray Diffractometers

Abstract: An algorithm has been derived, forming the basis of a computer program called BBCCURV, which calculates a Bragg-Brentano X-ray diffractometer intensity correction curve (intensity correction factor K i vs . 2 θ i ) given the diffractometer and sample dimensions, and the effective (not theoretical) linear absorption coefficient of the sample. Use of this calibration curve gives a set of intensity data free from aberrations, which are caused mainly by sample transparency, curvature of the diffraction cones passing through the receiving slit and possible beam overflow past the specimen at low angles. The algorithm was confirmed with a full-profile Rietveld refinement of Bragg-Brentano X-ray diffraction data from a H + -ZSM5 zeolite sample. On introducing a BBCCURV correction curve, the profile R-factor over the pattern points dropped from 30.8% to 16.5%, a significantly better fit when the data were corrected with a BBCCURV curve. BBCCURV intensity calibration curves from LiF ( μ = 1.5 mm −1 ) through zeolites, clays, ZnO, rutile, Pb(NO 3 ) 2 and finally solid metal ( μ = 1000 mm −1 ) (CoK α ) indicate upward revision of the measured diffractometer intensities by factors of between 2 and 10 at 2 θ = 5° for these sample types, normalised to a correction factor of 1.0 at 2 θ = 44°. Corrections of this magnitude to Bragg-Brentano data are thus significant in full-profile structure refinement and quantitative analysis with Bragg-Brentano data. Use of a variable divergence slit (VDS) is not appropriate in full-profile refinements as the intensity aberrations are magnified, and conversion from VDS data to aberration-free data is sample- and transparency-dependent, and not the simple area (sinθ) −1 function generally assumed. Use of a fixed divergence slit with a BBCCURV-type calibration is recommended.

X-ray diffraction measurement of the quartz content of clay and silt fractions in soils

Abstract: An XRD method for measurement of quartz content using ZnO as the internal standard was tested on different particle sizes between 0 and 20 µm. Calibration curves showed a good correlation coefficient for particle-size fractions up to 20 µm; the slope increased for the fractions from 0·7 to 5 µm and was relatively constant for coarser particle sizes. Fine quartz fractions were etched with hydrofluoric acid to remove the surface layer damaged during dry grinding. The use of such etched quartz increased the slopes of the calibration curves for small particle-size fractions and approximated the natural fine quartz fraction much better than the original dry-ground material. The mean of six measurements gave good accuracy provided that the slope of the calibration curve was adjusted for the particular particle-size fraction. This method was used on 0–2 µm, 0–0·2µm and 0·2–2 µm fractions of French silty soils and the results are in agreement with the data from chemical analysis and with the mineralogical interpretation.

Graphite furnace atomic absorption spectrometry and phase diagrams of alloys

Abstract: The reading of phase diaprams is effective when considering high-temperature reactions during ashing and the beginning of atomisation in graphite furnace atomic absorption spectrometry. The origin of double-peak signals in the direct atomization of metal samples could be explained; the calibration curve for Pb in Fe could be utilized for Pb in Cu because of their similar phase diaprams. The role of a metal matrix modifier could be considered using phase diaprams between the matrix modifiers and analyte elements. The combinations of the modifier metals and analyte elements have been classified in three cases: effective, moderately effective and ineffective

Enthalpimetric analyzer and method of use

Abstract: An automated thermal analysis system and method for the detection and quantitative measurement of analytes having thermally-induced, energy events and associated enthalpy changes is described. The system and method are automated to simplify data acquisition and analysis and to enhance sensitivity. The temperature of at least one sample containing at least one analyte having a thermally-induced, energy event is measured upon heating or cooling through the temperature range of the energy event of the analyte to derive a time-temperature curve corresponding to the enthalpy change of the analyte. From the time-temperature curve and a preselected reference parameter derived therefrom in the vicinity of the energy event region of the analyte, analyte concentration in the sample may be derived from a calibration curve correlating the preselected reference parameter to a normalized sample weight or volume. Alternatively, analyte concentration may be derived by a residual analysis of the time-temperature data or by fitting an nth order polynomial to data obtained in the energy event region and subtracting therefrom a reference curve obtained by interpolation of pre- and post-event data or by running an inert or analyte-free sample in a separate run.

Direct Introduction of Steel Samples into a Capacitively Coupled Microwave Plasma for Atomic Emission Spectrometry

Abstract: The feasibility of analyzing steel samples by direct introduction into a helium/hydrogen mixed-gas capacitively coupled microwave plasma was assessed with steel standard reference materials (NIST 442-450). Linear calibration curves were obtained for various concentration ranges. Limits of detection for Sn and Pb were 5 μg/g and 0.08 μg/g, respectively.

Quantitative Elemental Analysis of Solid Samples by Arf-Excimer Laser-Ablated atomic Emission Spectrometry

Abstract: Quantitative analysis of chromium in standard low alloy steel samples by excimer laser ablated plasma atomic emission spectrometry was obtained. A calibration curve was developed which related the chromium concentration in a solid steel matrix to the intensity ratio of Cr(I) 520.84 nm to Fe(I) 516.75 nm. The chromium concentration determined ranged from 0.062 to 1.31 %. A detection limit of 20 μg/g (approximately 0.002 %) was estimated.

Calibration system and method for calibrating a blood gas sensor

Abstract: A calibration system and method for calibrating a medical sensor (16) that monitors chemical blood gases. A calibrator (12) is used in connection with a tray (14) in which the medical sensor is stored in a sterile environment, both before and during the calibration process. The medical sensor is immersed in a liquid (30) in a tonometry chamber (28) defined in the tray and covered by a membrane (120/122) that is permeable to gas, but impermeable to bacteria. During the calibration process, the tray is inserted into the calibrator, bringing a heated platen (26) into contact with the tonometry chamber, so that the liquid can be heated to a calibration temperature substantially equal to the temperature at which the medical sensor will subsequently be used. A first calibration gas is then bubbled through the liquid until a saturated condition is achieved. Once the temperature of the liquid is increased to the desired calibration temperature, as determined by a temperature sensor on the medical sensor, data for a first calibration point is taken. A second calibration gas is then bubbled through the liquid until saturation is achieved, yielding data for a second calibration point, for each of the chemical blood gas parameters. The calibration data is processed to determine calibration coefficients that will be applied to the medical sensor.

Accuracy of calibration procedure for energy-dispersive x-ray fluorescence spectrometry

Abstract: The quality of a calibration procedure was studies in terms of the accuracy of the calibration factors. In particular, the influence of the uncertainties of the incident and emerging angles and of the mass absorption coefficients on the calibration factors was described theoretically for a calibration procedure based on standard samples of any thickness. The calculations were carried out for an x-ray tube and a radioisotope excitation set-up. Practical consequences of the inaccuracies of the calibration factors were also demostrated for a few test samples of intermediate thickness analysed by the emission–transmission method.