Showing papers on "Calibration curve published in 1974"

Problems of the radiocarbon calendar and its calibration

Abstract: Both the growing body of literature on the tree-ring calibration of radiocarbon dates, and the variety of statistical approaches used, make it appropriate to review the basic principles involved in the construction of a calibration curve. While its ultimate validity is in part a geophysical problem, the appropriate form for the calibration function, given a specific body of data, is a statistical question centering upon the analysis of the measurement errors involved. The relationship between the calibration function and the inverse calibration function is examined, and the shortcomings of the available published calibration curves considered in the light of this examination. It is concluded that there is no reason to doubt the general principles on which the calibration is based, but a need exists for a more critical handling of the measurement data with a statistical treatment of the errors involved. The quality of the data could itself be improved by the use of replicate samples for inter-laboratory projects specifically designed to investigate the magnitude of measurement error.

High precision atmospheric hygrometry using the solar infrared spectrum

Abstract: An infrared hygrometer of high precision is described. The procedure for calibrating the hygrometric ratio in terms of atmospheric water vapour content is based on comparisons and extrapolations from data resulting from high accuracy measurements of vertical water vapour content in a relatively narrow range of values. The resulting calibration curve extends from 0.3 to 40 cm STP of water vapour content. The applications of the instrument are discussed. A comparison of our calibration curve with others presented in previous papers shows that a great improvement has been achieved in this field.

Improved calibration procedure for gel permeation chromatography of lignins

Abstract: In studying macromolecular properties of lignins, gel permeation chromatography (GPC) is a convenient method for the determination of lignin molecular weights and their distribution. A GPC analytical column was calibrated by preparing narrow molecular weight lignin fractions, then applying the method of Goring and co-workers to obtain molecular weights from the ultracentrifuge at zero concentration and zero field force. Diffusion and other curve-broadening effects in the GPC analytical column were taken into account by applying the correction method of Hamielec and co-workers to derive the coefficients of the calibration curve. The molecular weight of a lignosulfonate sample determined on the GPC was found to coincide closely with that obtained by ultracentrifugation.

A versatile thin film method for quantitative X-ray emission analysis

Abstract: Liebhafsky and Zemany proposed two terms in X-ray emission analysis: one is the linear thickness of a specimen below which the absorption effect vanishes; the other is the critical thickness of a specimen above which the specimen becomes infinitely thick. The criteria for these two terms are defined here in quantitative terms. A procedure for making thin films of closely controlled thickness is described. The sample is dispersed into a film-forming polymer solution which contains an internal standard element. A thin film is made of this suspensoid by a film applicator. The internal standard element is used to correct for variation in actual film thickness. A single calibration curve can be used for samples of different matrices. Experimental data are presented to demonstrate the effectiveness of this thin-film method in eliminating matrix effects.

Swept frequency measurement system

Abstract: A calibration curve for a test circuit alone is first memorized by the system and is then automatically subtracted from subsequent response measurements of a test device placed in the test circuit to give just the response characteristics caused by the test device. In one preferred embodiment, the scale factor of a sensitivity control is also memorized along with the calibration data and is used to control an attenuation circuit between the calibration memory and the circuit which subtracts the stored calibration signal from the test device measurement signal to thereby allow the display sensitivity to be changed after the calibration signal has been recorded without introduction of measurement error.

Quantitative determination of elements in alloys

Abstract: A method of quantitative spark emission analysis of a select element in an alloy comprising establishing a basic calibration curve which relates a spectrometer count during a given integration time period to an actual content of the select element in a standard sample of the alloy, determining an influencing factor on the spectrometer count of the select element by the presence of an influencing element in the alloy being analyzed, spectroscopically analyzing the alloy for the select element during the given integration time period and deriving an indicated content of the select element from the basic calibration curve, and adjusting the indicated content of the select element in the alloy being analyzed by the influencing factor so as to derive an actual content of the select element in the alloy.

Nondestructive determination of tritium content of erbium tritide thin films

Abstract: The x-ray spectrum resulting from beta decay of an erbium tritide film is used to measure tritium content of the film. The areal density of the film is measured using differential emission techniques and is used to correct the measured x-ray intensity for self-absorption. The corrected intensity is linearly related to tritium content through an empirically derived calibration curve. The technique will measure tritium contents from less than one to several hundred micron liters. Repeatability is generally determined by counting errors and is typically 0.3% for a 5-min count while accuracy depends upon the empirical calibration technique. In principle, the technique is not limited to erbium tritide but can be extended to many uniformly radiating thin films.

Fourier Transform Infrared Determination of Parts per Billion of Oxygen in Silicon

Abstract: Previous work on oxygen in silicon resulted in producing an infrared calibration curve based on gas fusion analysis. This calibration curve was also compared with an activation analysis method. The normal spectrometric technique employs a double beam grating spectrophotometer and a 1-cm polished silicon sample and reference slices. The silicon lattice band at 1100 cm−1 overlaps the silicon-oxygen vibration band at 1107 cm−1. Thus, to measure the baseline accurately it is necessary to have an oxygen-free silicon in the reference beam. The lattice band is ratioed out of the spectra, and only the oxygen-silicon vibration band appears. Using 1-cm thick sample and reference slices a limit of detection of 50 ppb atomic is obtained. The 1-cm thickness used is the maximum possible; the lattice absorption band absorbs sufficient energy for greater thickness to degrade the signal-to-noise ratio. The poor signal-to-noise ratio for thicker samples results in meaningless results when a spectral scan is run.

Determination of Nickel, Cobalt and Molybdenum Content in Hydrorefining Catalyst by X-Ray Fluorescence Analysis

Abstract: By X-ray fluorescence analysis, a method for determining the nickel, cobalt and molybdenum content in the hydrorefining catalyst was studied.Results are summarized as follows.1) Cobalt was able to be determined by the simple calibration curve method.2) Molybdenum was able to be determined by the internal standard of zirconium and dilution of alumina.3) The observed values of cobalt and molybdenum by this method were of the same accuracy as those observed by the atomic absorption spectrometry, and the repeatability of the results was excellent.4) The required time was about 1.5 hours per one sample for determining the foregoing three elements.5) The observed values of nickel, however, were 20-30% higher than those obtained by the atomic absorption method. We wish to examine this problem in near future.

Fiber Content of Blends of Cotton and Optically Brightened Polyester Determined by UV Fluorescence

Abstract: A new method is described for measuring fiber content of blends of cotton and optically brightened polyester using uv fluorescence as measured by a special uv meter. The intensity of the fluorescence is proportional to polyester content of the blend. A calibration curve is prepared using known blends, and unknown blends are determined by measuring fluorescence and referring to the calibration curve. Stock can be tested in the form of raw stock, sliver, roving, or yarn. The method is accurate and is simpler and faster than existing wet chemical methods. Fiber contents of 18 blends from a full-scale spinning project were tested by the fluorescence method and by the method recommended by the American Association of Textile Chemists and Colorists(AATCC). The coefficient of simple correlation of the results from the two methods was 0.997. Level difference between the methods was insignificant.

The use of standards in the quantitative electron probe micro analysis of binary metal systems

Abstract: For the binary metal systems investigated, the Ziebold-Ogilvie relation has been found to be valid. It has been shown that polyphase alloys may be used as calibration standards if some specific conditions are fulfilled. In connection with a long-term instability of the microprobe apparatus, the Ziebold-Ogilvie constant of the calibration curve may vary with time. There is no reason for assuming that this instability is restricted to the particular instrument used. Therefore it is recommended that one or two standard alloys be used together with the pure reference metal to determine that constant every time concentration measurements have to be performed. The effect of the long-term instability can hardly be taken into account in the usual theoretically-based correction procedures.

Temperature determination of thin sapphire substrates

Abstract: A technique is presented which allows for a noncontact temperature determination of thin sapphire substrates with ordinary laboratory instrumentation. The technique utilizes the property of expansion with temperature. A calibration curve of sapphire substrate temperature vs heater temperature is deduced. This calibration scheme can be used for other substrate materials which are transparent in the visible region such as fused silica, glass, and many crystals for which thermal expansion data are known.

A Flexible Computer Program for Evaluation of Data Obtained via the Walsh Atomic Absorption Method

Abstract: A single computer program, for use in especially highly precise and accurate applications of the Walsh atomic absorption method, is designed to allow an analyst the freedoms (1) to determine the concentrations of up to 11 elements in an unrestricted number of samples; (2) to use up to 40 differently named standards and/or series of standards simultaneously, with or without a dilution option; (3) to fit any standard curve and associate it with either one equation or two; (4) to make the equation of all or part of any standard curve a polynomial of either first or second degree; and (5) to have standard curve equation coefficients and/or coordinates of certain points on the standard curve printed out in easily readable form. The concentration of a given element of interest, in any sample, is treated as a variable with random properties. Up to 26 estimates of this concentration can be made, and, from them, the program computes the mean, standard deviation, coefficient of variation, and both 95 and 99% confidence limits about the mean.

Linearization of the calibration curves in the thin layer densitometry based on the dual-wavelength and zigzag scanning method

Abstract: すでに報告した二波長・ジグザグスキャニング方式のデンシトメーターの特長を生かして,従来薄層デンシトメトリーにおけるネックであった検量線の非直線性を解消する検量線補正装置を試作した.これは薄層スポットを微小光束でジグザグスキャニングしたときの吸光度を濃度に比例した値に補正したあとで積分器で積分する方式で,吸光度-濃度の関係はKubelka-Munkの理論曲線に基づいて補正した.同一種類のプレートを用いれば,サンプルの種類や測定波長に無関係に同一の理論曲線で直線化できるなどはん用性のある良好な結果を得た.

Measurement of Moisture Content in Granular Ammonium Phosphate by a Microwave Method

Abstract: The attenuation of granular ammonium phosphate in a matched, X-band circular waveguide sensor was used to measure its moisture content. In a waveguide length of 250 mm the slope of the calibration curve (attenuation vs. moisture content) of above 12 dB/% H2O has been obtained. With high meter stability and the density of granular material nearly constant, this slope gives a measurement accuracy of about ±0.10 % H2O in the range of 0.2 to 1.5 % H20. The measuring sensor, the properties of the material and sources of measurement error are discussed.

Hardenability of steel with thermomechanical treatment

Abstract: 1. Plastic deformation of austenite during HTTMT shifts the isothermal transformation curves to the left and reduces the hardenability of steel. 2. A method was proposed for plotting a calibration curve in order to determine the relationship between the hardenability of steel after HTTMT and after standard quenching. 3. A calibration curve was plotted and an empirical equation was obtained making it possible to determine the standard end-quench hardenability of alloy structural steels with a high carbon content (0.50–0.70% C) after HTTMT under the following conditions: TAust.=900–1000°, TDeform.=850–950°, e=20–30%.

Determination of sodium and potassium concentrations in nanolitre samples. Evaluation of a commercially available helium glow photometer.

Abstract: The analysis of error was carried out for sodium in concentrations from 40 to 400 meq/l, and for potassium in the range from 05 to 40 meq/1 The sample volume was about 1 nl For each calibration curve five calibration points were measured eight times each Each repetition was carried out by three partial measurements in order to find the interference effects between sodium and potassium The parameters of the best straight line calculated by the method of weighted least-squares were estimated Linearity was tested By the low of propagation of error, the error in the calculated concentrations was estimated At optimal settings of the instrument the relative error ranged from 25 to 4% for sodium and from 25 to 6% for potassium

The study of linearity for calibration curve and intensity in ATR method

Abstract: ATR法においてKRS-5および塩化ナトリウムを高屈折率媒質とした場合のピーク強度および検量線の形の差異について入射角を変えた場合の影響,光学定数の変化による影響など実験および計算の両面にわたり検討を行ない以下の結果が明らかとなった.(1)塩化ナトリウムを高屈折率媒質とすると一般にKRS-5より強度の大きいスペクトルが得られた.すなわちベンゼン,安息香酸イソアミルエステルの四塩化炭素溶液を塩化ナトリウム,KRS-5を媒質とし,また二硫化炭素溶液についてはKRS-5を用いて検量線の測定を行なったところ,おのおのほぼ良好な直線性を有する検量線が得られ,塩化ナトリウムを用いた場合には,KRS-5に比べ,3～5倍に強度が増加した.(2)ベンゼンの光学定数に関する文献値を用いてベンゼン1035cm-1の検量線を計算により求めたところ,両媒質とも良好な直線関係が成立することが明らかとなり,強度比も実験値と大略一致した.また光学定数,入射角などが変化した場合の反射率に及ぼす影響を考察するため,相対実効厚みde/λ1に関して計算を行なったところ,塩化ナトリウムの場合には特にこれらが反射率に敏感に影響を及ぼすが,試料に対し適当な屈折率をもつ溶媒を選択し,濃度,入射角などの測定条件について注意をすれば直線性のよい検量線が得られることがわかり,実験結果とも符合した.

Calculation of certain physicochemical characteristics of solid paraffinic hydrocarbons from gas-chromatographic data

Abstract: Boiling point distribution may be determined from gas-chromatographic data on petroleum products. Such a method has been termed "simulated distillation" [1]. It consists of a chromatographic separation of the petroleum product in a column with a nonpolar liquid phase and programmed temperature. Under these conditions, all hydrocarbons are eluted from the column in strictly increasing order of boiling point, regardless of class. A calibration curve is plotted relating the boiling point of the component to its exit temperature. This is done by analyzing a model mixture of hydrocarbons with known boiling points. Then, with exactly the same conditions of experiment, an unknown mixture is analyzed, recording the exit temperatures of the components. The boiling points of the components are determined from the calibration curve, and the quantities from the chromatogram. These data are used to plot a TBP curve. The temperature programming makes it feasible to analyze in a comparatively short time either crude oils or wide-cut petroleum products. For example, in [2], a TBP distillation curve was plotted from the data of a gas-chromatographic analysis for a :kerosine-gas oil fraction. In other papers [3, 4], data are presented on the analysis of petroleum cuts with 550"C end point.

Hydromat. a continuous cod-measuring instrument

Abstract: A new COD analyser based on the principles of the standard methods is described. Experimental data are given as the linear calibration graph, the repeatability and the influence of chloride, ammonium and nitrate. The correlation to the standard method is tested for test substances and industrial sewages.