Showing papers on "Calibration curve published in 1989"

Correction of Polychromatic Luminescence Signals for Inner-Filter Effects

Abstract: Fluorescence (FL) and absorbance (ABS) data are acquired simultaneously with a multiple detector spectrometer. The measured ABS is utilized in mathematical equations for automatic correction of fluorescence signals for attenuation (inner-filter effects) caused by significant absorption of the excitation or emission radiation by the fluorophore or other species. Correction equations are presented which apply to situations in which the excitation or emission beam cannot be considered monochromatic, for collection geometries involving optical fibers, and for chemiluminescence measurements. The correction scheme was tested with quinine sulfate (QS) as the analyte in the absence and presence of other chromophores (gentisic acid and methyl red). Even when conditions are such that the FL signal is attenuated by a factor of 5, the correction scheme is accurate to 2% or better. These corrections extend the linear range of the QS calibration curve by a factor of over 100, and they can improve the accuracy up to a factor of ten in cases for which polychromatic effects are important.

Method of calibrating a network analyzer

Abstract: For calibrating a network analyzer, calibration measurements are successively performed in any desired order on three different calibration standards connected between the two test ports; the first calibration standard is a two-port circuit all of whose complex scatter parameters are known and which is, for example, implemented by a direct connection of the two test ports; the second calibration standard is an attenuator of random transmission but known reflection; the third calibration standard preferably is a two-port circuit exhibiting random reflection which, however, is equal on both sides and different from the reflection of the second calibration standard.

Calibration of Radiocarbon Ages by Computer

Abstract: A PC-based computer program for automatic calibration of 14C dates has been developed in Turbo-Pascal (version 4.0). It transforms the Gaussian 14C dating result on the 3σ level into a real calendar age distribution. It uses as a calibration curve a spline function, generated along the calibration data points as published in the Radiocarbon Calibration Issue. Special versions of the code can average several 14C dates into one calibrated result, generate smoothed curves by a moving average procedure and perform wiggle matching.

Calibration of Thermal Conductivity Sensors for Measuring Soil Suction

Abstract: The accuracy of suction measurements using thermal conductivity sensors is dependent upon their calibration. Therefore, a calibration study was undertaken by using a modified, commercially available, pressure plate extractor. The experimental setup along with the calibration procedure are described. Typical calibration results are presented. In general, results showed reasonable agreement between the calibration curve determined in this study compared to those provided by the manufacturer for matric suction ranging from 0 to 175 kPa. However, large deviations in the calibration curves were observed at suctions above 175 kPa. The sensors were found to be quite sensitive to the changes in matric suction in the range of 0 to 175 kPa. For matric suction above 175 kPa, the sensitivity of the sensor is reduced.

Bias and nonlinearity of ultraviolet calibration curves measured using diode-array detectors

Abstract: Models for the dependence of diode-array UV chromatographic detector response on bandpass and on the shape of the absorbing sample's spectrum are presented. The equations derived comprise terms describing two sources of non-ideal response due to the polychromatic nature of the detected radiation. The bias, or deviation at low concentrations of the measured absorbance from the ideal, zero-bandwidth value, increases roughly as the product of the spectrum's local second derivative and the square of the bandwidth. Calibration curve nonlinearity at higher concentrations, present for monochromator-based detectors and transmittance-averaging diode-array detectors, is described quantitatively. These equations confirm that the calibration curves always bend downward when the sample's absorption spectrum varies at all within the bandpass. A distinction is drawn between transmittance-averaging and absorbance-averaging diode-array detectors. Experimental results illustrate the types of bias and nonlinearity seen in each class at the high concentrations of interest to preparative-scale liquid chromatography and quality-control applications.

Determination of Amorphous Phase in Quartz Powder by X-Ray Powder Diffractometry

Abstract: A powder diffraction method was applied to the quantitative analysis of amorphous silica in several quartz powders. Two calibration methods, i.e., direct analysis and the standard addition method were examined. Calibration mixtures were made by mixing a standard silica gel powder ground to under 5 μm particle size with a matrix quartz powder which was ground to 10 to 40 μm particle size and treated with NaOH solution to remove the amorphous phase caused by grinding. Intensity of the amorphous halo was measured at 23.0° 2θ, and the background intensity at 53.0° 2θ was subtracted. Linear calibration curves were obtained over the ranges of 0 to 50 wt% by direct analysis and 0 to 20 wt% by standard addition methods, respectively. The analytical results obtained by the two calibration methods were in good agreement with each other. The relative standard deviations for 4.3 wt% of amorphous silica were 4.6% by the direct analysis and 5.4% by the standard addition method. These methods were successfully applied to a correction of reference intensity ratios (RIR) for several quartz powders containing amorphous silica. After the correction for amorphous content, the relative standard deviations of the RIR values for quartz powders became smaller.

Histograms obtained from computerized radiocarbon age calibration.

Abstract: Two methods of assigning probability values to calendar years are compared by summing distributions for a large number of 14C ages derived from samples initially distributed uniformly in calendar years. The radiocarbon ages are calibrated with both a hypothetical calibration curve and the internationally accepted one. The effect of the calibration curve on an ideal and a random sample population is examined.

Method of determining calibration curve and apparatus using calibaration curve

Abstract: A method of determining a calibration curve used in deciding the components of living organism by means of the least-squares method by using a plurality of measured data at different concentrations obtained by measuring reaction solutions of a plurality of standard substances having different concentrations. At least a single set of measured data Y(i) is weighted in a predetermined manner, the measured data Y(i) being obtained from the standard substance reaction solution at a specific concentration X(i) near a limit value used in deciding the living organism components. With the weighting, a calibration curve having a high precision at a portion near the limit value is realized resulting in a correct and highly reliable decision.

A Simple Iteration Procedure to Correct for the Density Effect in the Aerodynamic Particle Sizer

Abstract: A simple iteration procedure is developed to correct for the density effect in the Aerodynamic Particle Sizer. The correction is appreciable for large particles due to ultra-Stokesian drag. For submicron particles, the correction is less than 4% and is caused by the change of the slip correction factor across the accelerating nozzle. Both corrections were included in the procedure to calculate a new calibration curve at a desired particle density from a standard calibration curve. The iterations converge very fast; a microcomputer program has been developed which can calculate a 20-point calibration curve in less than 5 seconds. The results of the present procedure are in excellent agreement with the supercomputer calculations of Ananth and Wilson (1987).

Method for calibrating a network analyser

Abstract: In order to calibrate a network analyser, calibration measurements are carried out one after another in any desired sequence on three different calibration standards connected between the two measurement ports. In this case, a double port is used as the first calibration standard of which all the complex scatter parameters are known, this being, for example, carried out by direct connection of the two measurement gates. As the second calibration standard, use is made of a damping element having arbitrary transmission but known reflexion. As the third calibration standard, use is preferably made of a double port which has reflexion which is arbitrary but equal on both sides and different from the reflexion of the second calibration standard.

Basic Aspects of X-Ray Absorption in Quantitative Diffraction Analysis of Powder Mixtures

Abstract: The mathematical relationships are developed which are pertinent to the quantitative analysis of powder mixtures for the case of diffraction from the surface of a flat powder specimen. These formulas relate the diffracted intensity to the absorptive properties of the sample. Three important cases are treated: (1) Mixture of n components; absorbing powder of the unknown equal to that of the matrix; concentration proportional to intensity. Direct analysis is permitted. (2) Binary mixture; absorbing powder of the unknown not equal to that of the diluent; concentration not proportional to intensity. Direct analysis is possible by means of calibration curves prepared from synthetic mixtures. (3) Mixture of n components; absorbing power of the unknown not equal to that of the matrix; general case. Analysis is accomplished by the addition of an internal standard. Concentration is proportional to the ratio of the intensity of a selected reflection from the unknown to the intensity of a reflection from the internal standard.

Method and system for transferring calibration data between calibrated measurement instruments

Abstract: The present invention provides a method and system which is useful on instruments requiring experimentally determined calibration curves by which calibration data can be transferred to a plurality of field gauges, thereby avoiding the necessity of individually calibrating each gauge each time calibration is necessary. The field gauges are initially cross related to a master gauge. At a later time when a new calibration is necessary, the master gauge is calibrated using carefully prepared samples of a test material. Using the experimentally derived calibration curves with the cross relation data provides calibration data for the field gauges.

Method for quantitative analysis of analyte in liquid sample using analytical element

Abstract: In a method for quantitatively analyzing an analyte in a liquid sample by applying the liquid sample on one of a set of analytical elements and measuring a color developed in the analytical element through reflection photometory in which said set of analytical elements are the same elements as a standard element except for deviation of sensitivity to the analyte, but said deviation of sensitivity is essentially equivalent to each other among the set of analytical elements, the calibration curve of the standard element with respect to said analyte being predetermined, an improvement involving the preparation of a linear equation for defining a relationship between an optical reflection density value ODx to be measured on an analytical element belonging to said set of the analytical elements and an optical reflection density value ODs being predetermined on the standard analytical element, in which the optical reflection density values ODx and ODs are those to be determined on colors developed on the respective elements upon application of a liquid sample containing the analyte in the same content Cx.

Direct sample introduction of solid material into a pulse-operated MIP

Abstract: To minimize problems caused by sample introduction into a microwave-induced plasma (MIP), we have developed a system consisting of a spark ablation cell and a pulse-operated microwave-induced plasma (pulsed-MIP). An aerosol is generated from solid samples with the use of a spark discharge. The resultant material is swept into a pulsed-MIP. Design and fabrication criteria for the spark source and the spark ablation cell are presented. The combined sources show enhanced precision, stability, signal-to-noise levels, and detection limits relative to direct spark emission. Analytical calibration curves and detection limit data are shown for nickel, manganese, and chromium in steel samples. Time-resolved data are also shown.

Calibration solution and calibration method for sensor

Abstract: A calibration solution, which is used when measuring the ion concentration of solution under examination such as blood or other body fluids using a pH sensor or the like ion sensor with a solid electrode, is prepared by adding NaCl to a standard buffer solution and thus setting the ionic strength of the solution to be substantially identical with the ionic strength of solution under examination. A sensor calibration method is also disclosed, in which at least two reference calibration solutions having different pH values are prepared, the electromotive force of the sensor in these calibration solutions is measured by immersing the sensor in the solutions, and a calibration formula is produced from the electromotive force for the pH values of the reference calibration solutions. A predetermined amount of bicarbonate buffer solution is added to the calibration solution to maintain a substantially constant ionic strength of the solution, thus permitting simultaneous calibration of an ion sensor and a gas sensor.

Method for determining a calibration curve and device using the calibration curve

Abstract: Method for determining a calibration curve, which is used in the determination of the components of a living organism, by means of the least-quadratic method, using a multiplicity of measured data at different concentrations, which are obtained by measuring reaction solutions of a multiplicity of standard substances of different concentrations. At least one individual group of measured data Y(i) is weighted in a prescribed way, the measured data Y(i) being obtained from the standard substance reaction solution at a specific concentration X(i) close to a limiting value which is used in determining the components of the living organism. By means of this weighting, a calibration curve is realised which has a high precision in a portion close to the limiting value, which is accompanied by an accurate and highly reliable decision.

Calibration With Randomly Changing Standard Curves

Abstract: Changes in calibration curves from one time to the next, caused by drift, often require measuring devices to be recalibrated at frequent intervals. In such situations the usual practice is to estimate the unknown values of test samples using only data from the corresponding calibration period. Under a random coefficient regression model for the different calibration curves, however, it can be shown that it is more efficient to combine the data from all calibration periods to estimate the unknowns. We consider a particular class of point estimators obtained by inverting suitable prediction functions and show that the estimator obtained from a best prediction function is optimal in a sense defined by Godambe (1960) and Durbin (1960) in the context of unbiased estimating equations. We also compare the smallsample performance of this estimator with the usual estimator using the Pitman closeness criterion.

Wear measurement at depths of several tens micrometers on the surface of iron using a thin layer activation method by 7 MeV proton beam

Abstract: A method of measuring iron wear using thin layer activation is discussed. The iron surface is activated by a 56Fe(p, n)56Co reaction etc., using a 7.00 MeV proton beam from a tandem Van de Graaff accelerator. Irradiation of 0.5–2 (μA beam currents produces 1–10 μCi of 56Co activities in a layer about 50 (μm thick. To get the basic depth profile of cobalt activities, a 1.5 cm iron cube with a 3 mm diameter activation area is used to produce a wear calibration curve. Wear is produced by a polishing machine and wear thickness is measured by a precise electric micrometer. Monitoring radiation instruments are a 3 in. diameter × 3 in. Nal (Tl) scintillator and a high-purity Ge detector. A detailed iron wear calibration curve using 56Co, 57Co and 58Co activities is obtained in accordance with iron wear thickness. After discussions, a universal iron wear calibration curve using the 56Co/57Co or 56Co/58Co ratio is newly developed. This convenient curve is expressed in an experimental formula with a correction for time attenuation.

Spectrophotometric Determination of Germanium Following Collection on an Organic Solvent-Soluble Membrane Filter as the Complex with Phenylfluorone

Abstract: A spectrophotometric method is described regarding the determination of germanium. A colored complex of germanium with phenylfluorone was collected on an organic solvent-soluble membrane filter made of cellulose nitrate. The complex, together with the filter, was dissolved into N, N-dimethylformamide (3cm3), and the absorbance of the solution was measured. The obtained calibration curve was linear from 0.05 to 1.0μg of germanium and the molar absorption coefficient was 1.9×105dm3 mol-1 cm-1. The relative standard deviation of the absorbance obtained at 1.0μg of germanium was 0.4% (n=11). The interference of molybdenum(VI) could be eliminated by hydrogen peroxide. The time required for one run was about ten minutes and germanium at 1μg dm-3 levels could be easily determined. This method has been applied to the determination of germanium in samples of hot-spring water.

Extended standard curve stability on the CCD magic lite immunoassay system using a two-point adjustment

Abstract: Ciba Corning Diagnostics has developed a two-point adjustment algorithm for use with the Magic Lite System which allows for extended stability of a full 7–10 point calibration curve over the life of a kit. This adjustment is accomplished by using a master calibration curve established during manufacturing along with two calibrators for each assay. Most conventional non-automated immunoassays contain anywhere from 6 to 10 calibrators which are included with each run of an assay. Eliminating the need to run full standard curves and using the two-point adjustment algorithm results in significant savings in both labour and reagent usage.

PIXE trace-element determination and its accuracy in the analysis of bile

Abstract: A setup for trace-element analysis using particle-induced X-ray emission (PIXE) is described briefly. Details of the electronic system used for automated measurements with a constant count rate are given. The main features of the Fortran computer code XRANA used for the analysis of X-ray spectra are also presented. The calibration of observed total K- and L-line intensities versus trace-element concentrations was established for the system for proton bombardment with 2.79 MeV of elements with Z ≥ 16. For elements with Z ≥ 20 this was done by measuring simultaneously the spectra of X-rays and of elastically scattered protons. For elastic scattering the Rutherford formula was assumed to yield the correct value for the cross section. This assumption was tested for the elements Ca, Sc, V and Ti, and deviations were found for Ca and V. An absolute calibration was obtained using a few foils with a known element concentration. From the calibration curves the absolute cross sections for total K- and L-line excitation were derived, using absorption data and a calculated detector efficiency. The cross section for K-line excitation was found to agree within a few percent with values calculated using Paul's [17] empirical formula. The agreement with the cross section for L-line excitation calculated with a formula given by Miyagawa et al. [18] was found to be less satisfactory. The setup was used for trace-element determinations (relatively to an added standard) in bile of experimental Wistar rats. The factors influencing the precision and reproducibility of these determinations were investigated. These factors include sample preparation, contaminations, homogeneity of trace-element concentrations over the sample surface, evaporation, precipitation during sample preparation, spectrum analysis and calibration. It is concluded that for nonvolatile trace elements with Z ≥ 19 and an abundance of > 0.5 μg cm 3 an accuracy of

Ion chromatographic determination of aluminium with ultraviolet spectrophotometric detection

Abstract: A method for the determination of aluminium by high-performance ion-exchange chromatography followed by post-column derivatisation with 4,5-dihydroxy-1,3-benzenedisulphonic acid, disodium salt and ultraviolet detection at 310 nm is described. The calibration graph was linear from 10 to 5000 µg l–1 of Al with a detection limit (3σ) of 7 µg l-1. Typical relative standard deviations in the range 1.3–3.9% were obtained for a 100-µg l–1 Al standard. Freedom from interference from six cations investigated is reported, the exception being titanium. The method was applied successfully to the determination of aluminium in certified reference materials after conventional wet digestion (NBS SRM 1572 and NIES No. 7). The incomplete digestion of biological materials in a microwave oven is reported. The problems of using a non-destructive analytical technique for the determination of aluminium in a natural riverine water reference material are discussed.