Showing papers on "Calibration curve published in 1970"

Universal calibration in GPC: A study of polystyrene, poly‐α‐methylstyrene, and polypropylene

Abstract: The theoretical justification for using M[η], or a similar quantity, as a universal calibration parameter in GPC is reviewed. The equation based on this parameter is applied to transform the primary calibration curve, obtained by means of polystyrene samples, into calibration curves for poly-α-methylstyrene, polypropylene, and linear polyethylene. The Mark–Houwink equations for these polymers, as they are used in the transformation, are discussed. The resulting GPC calibration curves are compared with molecular weights and peak elution volumes of fractionated poly-α-methylstyrene and polypropylene. The same comparison is made with samples of polypropylene and polyethylene having very broad molecular weight distributions. The agreement lies within experimental error.

The Instrument Spreading Correction in GPC. I. The General Shape Function Using a Linear Calibration Curve

Abstract: A general shape function is proposed for describing the instrumental spreading behavior in gel permeation chromatography (GPC) columns due to axial dispersion and skewing effects. The general shape function contains statistical coefficients which describe the axial dispersion, skewing, and flattening of ideal monodisperse standards. A method denoted as the “method of molecular weight averages” is used to derive equations to correct GPC number- and weight-average molecular weights and intrinsic viscosities calculated from linear molecular weight calibration curves. The validity of these equations is experimentally verified with data for polystyrene, polybutadiene, and polyvinyl chloride polymers in tetrahydrofuran. The physical significance of the correction equations and their statistical coefficients is discussed in relation to the observed GPC chromatograms. Application of this shape function to the numerical Fourier analysis method for correcting differential molecular weight distribution (DMW...

Calculation of Blood 02 Content from Optically Determined Hb and HbO2

Abstract: The Co–Oximeter is an instrument of considerable utility in measuring Hb and HbO2. For O2,contents calculated from these measurements to be compatible with those determined by the Van Slyke procedure, it is necessary to use 1.30 as the O2–binding capacity for Hb and to correct HbO2, other than at unity, by reference to a calibration curve. The scales must be set with blood of the species to be studied, and special precautions are necessary if actual Hb differs greatly from that used for adjusting the scales and constructing the calibration curve.

Determination of parts per billion of oxygen in silicon

Abstract: A new calibration curve for determination of the oxygen content in single crystal silicon by infrared spectroscopic techniques is presented. This calibration curve gives results approximately a factor of two different for oxygen concentration when compared with the presently used factor. Gas fusion analysis results on 99 samples were correlated with the infrared spectral measurements for the corresponding sample to calculate the new calibration curve. Use of the differential technique of double beam spectroscopy permits the determination of low levels (25–50 ppb atomic) of oxygen in silicon at 300 K. Lower temperatures give correspondingly lower limits of detection.

Apparatus for the calibration of shear sensitive liquid crystals

Abstract: An experiment was designed in which shearing forces acting on a film of shear sensitive liquid crystals could be measured directly while additional instrumentation was used to measure the peak spectral intensity of the light scattered by the substance. A liquid crystals sample of low temperature sensitivity was tested and a calibration curve was obtained with a linear slope of 0.208 (g/cm2)/nm from 0 to 3 g/cm2.

Basis weight gauge standardizing system

Abstract: A method for standardizing a basis weight gauge which includes the calibration steps of obtaining two calibration curves, one of which is displaced from the other by a dirt simulation technique. The displacement between the two curves is expressed as a third curve. A standard sample of a predetermined basis weight is inserted in the radiation path to provide a standard shift in conjunction with the dirt simulation to provide a reference value for the displacement function curve. During actual use of the basis weight gauge standardization is provided by relating a current standard shift to the initial standard shift to correct the displacement function curve which is then related back to the original calibration curve to provide the actual basis weight of the sheet material being measured.

The evaluation of a simplified form of presentation for five-hole spherical and hemispherical pitometer calibration data

Abstract: A theoretical and practical evaluation of a new method of calibration data presentation for five-hole spherical and hemispherical pitometers has shown that it is reliable and an advance over the traditional method in that it has: (i) simplified calibration curves; (ii) reduced the probability of misinterpretation of the data; (iii) become suitable for automatic computation. Comparisons between the theoretical and practical calibration curves for several pitometer designs and hole configurations have shown that a hemispherical probe is superior to a spherical probe not only because of its simplified construction, but because improved flow conditions around the probe lead to superior calibration characteristics.

Method and apparatus for evaluating the degree of quenching in scintillation spectrometry

Abstract: For evaluating the degree of quenching in a liquid scintillation sample, the pulse height corresponding to the centroid of part at least of the net count rate - pulse height spectrum due to a radioisotope in the sample or to an external standard is determined and compared with a calibration curve. Provision is made for subtraction of the contribution of the background noise. Determination of the counting efficiency is made by interpolation on a calibration curve.

The Instrument Spreading Correction in GPC. II. The General Shape Function Using the Fourier Transform Method with a Nonlinear Calibration Curve

Abstract: The instrument spreading function suggested in Part I of this series is investigated for use with the Fourier transform method for generating corrected elution volume chromatograms. The instrument spreading parameters are obtained using linear theory on narrow molecular weight distribution standards, as indicated in Part I. The corrected chromatogram is then combined with a nonlinear molecular weight calibration curve which was fit with a function suggested by Yau and Malone to generate true values of the number- and weight-average molecular weights. The instrument spreading function is shown to qualitatively and quantitatively describe the dispersion, skewing, and flattening effects ordinarily found in GPC chromatograms due to imperfect resolution by the GPC columns. The Yau-Malone function is shown to be a very useful function for fitting nonlinear molecular weight vs elution volume calibration data. Although the Fourier transform method is shown to work well with analytically generated data, i...

Determination of the width of a narrow molecular weight distribution by gel‐permeation chromatography

Abstract: A recycle gel-permeation chromatography (GPC) method for extrapolating to infinite resolution is proposed. From the GPC calibration curve, the extrapolated elution peak width volume can be converted into peak width in decades of molecular weight. For an essentially Gaussian distribution, the weight-average/number-average molecular weight ratio can be determined from a calculated conversion table.

The application of stripping processes in voltammetry

Abstract: The use of the hanging mercury drop electrode in conjunction with preelectrolysis and chronovoltammetric stripping has found wide application for the determination of trace amounts of certain ions which form amalgams or insoluble salts with mercury. When the concentrations of the trace elements to be determined are of the order of 10-6 M, the influence of the double-layer capacity on the stripping curve is negligible. However, the double-layer capacity is important when the concentrations are of the order 10-8 to 10 M, and at such concentrations, the presence of impurities or surface-active substances in the base electrolyte can be of vital importance. Some years ago, a two-electrode subtractive method of overcoming these effects was described6. An improved chronovoltammetric procedure will be discussed; this involves a variable time of pre-eleotrolysis and the addition of variable amounts of standard solutions. The new method gives more precise and reproducible results without the preparation of a complete calibration curve. Numerous examples are given to illustrate the proposed method. INTRODUCTION A predominant feature of modern analytical chemistry is the great importance of the determination of trace amounts of inorganic and organic substances. Electrochemical techniques of various types have been widely applied for such analysis but the polarographic method, proposed nearly fifty years ago by J. Heyrovsky, is undoubtedly the most important and has found extensive applications in trace analysis for inorganic and organic species present in solutions. Polarography in its conventional form has allowed many very important achievements, yet it has a considerable limitation in that concentrations below about lOmol/l cannot be determined. The diffusion current, d' thatflows in a polarographic circuit when a sufficient concentration of background electrolyte is present in the test solution, is composed of two components: the electrolysis current, i, and the capacity (condenser) current, i. Thus = + The concentration of the test substance is determined by measuring the height of the polarographic wave which depends on both these currents, bi only the electrolysis current component is proportional to the concentration of the 449

Evaporation Measurements by an Eddy Correlation Method

Abstract: Eddy correlation measurements of water vapor flux density have been made by using a barium fluoride film humidity sensor and a three-dimensional anemometer. During morning and evening periods, good agreement was obtained between eddy correlation data and two independent methods. Serious disagreement between measurements occurred only when the humidity sensor was operating within a poorly defined portion of the calibration curve that was not suited to on-line calculations. The results indicate that the humidity sensor could be modified to allow operation at all times within linear segments of the calibration curve, thereby permiting successful on-line computer calculations of eddy correlation vapor flux within one meter of the surface.

Indirect atomic absorption spectrometric method for the determination of silicon

Abstract: An indirect atomic absorption Spectrometric method for the determination of silicon is proposed which is based on the precipitation of an equivalent amount of lead molybdate from solutions treated with a known excess of lead ion and subsequent measurement of the lead ion remaining in solution A typical calibration graph is linear for samples containing 05–7μg silicon

Radioisotope analytical instrument for cement analysis of concrete

Abstract: A portable radioisotope instrument has been developed for field cement analysis yielding an accuracy of 1 to 2 percent cement in wet concrete. The instrument consists essentially of a cylindrical depth probe unit in which a pair of gamma -ray sources of different energy and a detector are arranged in coaxial alignment and the output of the detector is coupled to a portable scaler. The detector is shielded from the source so that only the gamma -backscattered radiation is detected and through proper calibration of the device as to the aggregate type the operator can radially analyze a wet mix by inserting the probe into the mix and measure the two radiation intensities with reference to the proper calibration curve to determine the cement content.

Determination of quartz. Evaluation of the differential thermal analysis method.

Abstract: Differential thermal analysis (DTA) was evaluated for the determination of quartz after comparing it with other methods now in use. The effect of particle size on peak height was studied by preparing calibration curves for sized quartz in silicon carbide (SiC). It was found that thermal response decreases with decreasing particle size, indicating the necessity for size analysis of unknown samples. Commercial talc and granite samples were analyzed for quartz after size determination and dilution with 30% SiC. Results were found to compare favorably to those obtained by phosphoric acid digestion. Foundry samples were similarly analyzed after preheating to combust carbonaceous material. These settled dusts were also analyzed using standard addition and internal standard techniques. X-ray diffraction analysis was used for comparison with the thermal procedures and agreement was found between the x-ray and DTA results.

Method for determining the purity of recovered sylvite

Abstract: A method for determining the purity of recovered sylvite by taking an infrared spectrum of the sylvite and making up a calibration curve from known standards of a known impurity on the sylvite. The impurity peaks appearing in the infrared spectrum are then compared with the calibration curve and the impurity concentration of the sylvite is determined.

Nuclear measurement of soil properties.

Abstract: THE STUDY WAS CONCERNED WITH THE DEVELOPMENT OF IMPROVED MOISTURE CALIBRATION METHODS FOR USE WITH NUCLEAR MOISTURE GAGES. THE THREE OBJECTIVES OF THE STUDY WERE TO DETERMINE THE SHAPE OF THE CALIBRATION CURVES FOR DIFFERENT SOILS, DETERMINE THE ACCURACY OF A SINGLE CALIBRATION CURVE, AND DEVELOP PRIMARY OR SECONDARY MOISTURE STANDARDS. TEN SOILS WERE STUDIED. THE FOLLOWING CONCLUSIONS WERE REACHED: (1) THE SINGLE CALIBRATION CURVE SEEMS TO BE A LINEAR RESPONSE BETWEEN COUNT RATIO AND MOISTURE CONTENT; (2) THE VARIATION FOR A SINGLE CALIBRATION CURVE WAS FOUND TO BE 3 PCF; (3) THE VARIABILITY APPEARS NOT TO BE A DIRECT FUNCTION OF SOME OF THE CHEMICAL COMPONENTS STUDIED; AND (4) THERE IS AN INDICATION THAT THE DATA CAN BE SEPARATED INTO TWO GROUPS AND THAT TWO CALIBRATION CURVES WILL IMPROVE THE ACCURACY OF NUCLEAR MOISTURE TESTS. A SIGNIFICANT CORRELATION WAS FOUND BETWEEN SOME PHYSICAL PROPERTIES AND DISTRIBUTION OF THE DATA. WORK ON THE THIRD OBJECTIVE--DEVELOPMENT OF PRIMARY OR SECONDARY MOISTURE STANDARDS, WAS DEFERRED PENDING FURTHER INVESTIGATION INTO THE CAUSES OF THE VARIABILITY. /FHWA/

Elimination of the influence of the enhancement effect on calcium determination in a cement raw mix by non-dispersive X-ray radioisotope fluorescence analysis

Abstract: Measurement of the intensities of the characteristicsK-series radiation of calcium and iron has been used for the elimination of the influence of iron on the calcium determination in cement raw mix. Two methods of interpretation of the experimental results are given, using nomograph or so-called ‘generalized’ calibration curve. The results are explained theoretically. The results of chemical analyses of industrial samples have been compared with non-dispersive fluorescence analysis.

Anwendungsmöglichkeiten des Radioaktiven Kryptonats von Silber in der Chemischen Analyse

Abstract: The radioactive kryptonate of silver has been prepared by ion bombardment. Some possibilities of its uses in analytical chemistry are reported. The influence of different solutions on Ag(85Kr) has been studied with respect to the use of kryptonate in the role of an end-point indicator in volumetric determination (determination of Ba2+ with the titrant K2Cr2O7) and in the technique of calibration curves [determination of HCl, Cr2O 7 2− and V(OH) 4 + ].

A Method of Reading Photographic Dosimeters and Apparatus for Carrying Out this Method

Abstract: 1,191,731. Photo-electric dosimeter readout. COMMISSARIAT A L'ENERGIE ATOMIQUE. May.10, 1967 [May. 11, 1966], No.21732/67. Heading G1A. A method of reading a dosimeter of the kind comprising a film, which is coated with a number of photographic emulsions of different sensitivities and which, during exposure to ionizing radiation to be evaluated, is located behind a number of filters of different known absorption coefficients, said filters defining different fields or areas on the emulsions, the method comprising, for each emulsion, measuring the illumination values of a photometer by light from each area of the film (i.e. due to the optical density of the developed film) and, for each area, multiplying the inverses of the illumination value by a factor dependent on the absorption coefficients of a reference filter which covered a reference area of the film during exposure and of the filter which covered the area under consideration; to obtain a modified value which is used to read the radiation dose from a stored calibration curve for the reference area. In the arrangement shown in Fig. 4 for examining a film having three emulsions exposed through seven filters, a photometer head 1 picks up light affected by the optical density of a developed exposed film and the signal is, in circuit 2, inverted and passed through a first integrator, a threshold circuit and a second integrator, all detailed in Fig. 6 (not shown). Initially, light from a reference area of the film is considered and the calibration curves of inverse illumination valves (photometer signals) against dose, stored in comparator devices 6 for each of the three emulsions. Then reading of the doses received by one emulsion commences, the appropriate channel 4, 5, 6 being switched into circuit. In device 4, the effect of background fogging is removed from the signal. In device 5, the signal is multiplied by the above-mentioned factor so that the modified photometer signal may be compared with the stored reference calibration curve to read out the dose. There may be facility in the device 6 for compensating for non-linearity of the calibration curve.