Showing papers on "Calibration curve published in 1968"

Gel Permeation Chromatography of Polymers: Use of Unperturbed Dimensions for Calibration

Abstract: Experimental GPC calibration data for polystyrene, poly(methyl methacrylate), and poly(dimethyl siloxane) in chloroform is reported. These polymers have similar hydrodynamic volumes, since their unperturbed dimensions and extensions in chloroform, due to polymersolvent interaction, are very similar. As a result, the same molecular weight calibration curve is obtained for the three polymers. Recently published GPC data is examined on a plot of logarithm of unperturbed end-to-end distance against elution volume. This procedure gives a universal calibration for linear polymer molecules, providing the column combination, solvent, and temperature do not change. For the data of Meyerhoff, use of the unperturbed dimensions is superior to the plot of η suggested by Grubisic, Rempp, and Benoit. A possible explanation, based on a model for the polystyrene gel pores, is proposed for the use of the unperturbed dimensions.

Molecular correlation spectrometry.

Abstract: The method of spectrometric determination of gas concentration by use of a mask is examined and described. Calibration curves for four gases, NH(3), C(6)H(5)CH(3), NO(2), and SO(2), are reported in detail, and results are included for C(6)H(6), NO, and SiF(4). The calibration curves are shown to be linear in a log-log plot over ranges of practical interest. The slopes are reproducible. The technique used in making masks is described. The proposed manner of making measurements involves the use of a small reference cell containing a sample of the gas being measured. When such a method of measurement is used, several gases of practical importance are concluded to be determined as to concentration to a few parts per billion with a precision of 10% or less, if path lengths of the order of several hundred meters are used. The results appear to be independent of the presence of unknown absorbing gases under many circumstances.

GPC data interpretation

Abstract: A rigorous procedure for reducing gel permeation chromatography elution data to differential molecular weight distribution curves is discussed and demonstrated by two sample calculations. The errors introduced by failure to correct the ordinates of the elution curve by means of a differential calibration curve are identified, and a simple graphical conversion procedure is illustrated.

Ultrahigh vacuum gauge calibration.

Abstract: A study was made of the problems associated with the operation and calibration of vacuum gauges at pressures below 10−10 Torr, particularly the hot-cathode magnetron gauge developed by Lafferty. A liquid-He pumped metal vacuum system was used to attain base pressures of 1×10−13 Torr. Calibration pressures were generated by molecular flow through known conductances using a McLeod gauge as the pressure standard. Under proper operating conditions, the output of the hot-cathode magnetron showed no deviation from linearity down to the base pressure of the system. Calibration curves were also obtained for a General Electric cold-cathode gauge and a mass spectrometer.

Calibration of the Nickel Dimethylglyoxime Spectral Shift at Pressures to 20 Kilobars for Use in Spectroscopic Pressure Measurement.

Abstract: A method for incorporating solid nickel dimethylglyoxime in a liquid enclosed by a gasket in the diamond-anvil high pressure cell is described. A calibration curve relating the spectral shift of the nickel dimethylglyoxime visible absorption band to the known freezing pressures of 14 liquids has been obtained. The equation for the calibration line is Δv¯=-158.9 P+1.82 P2 where P is expressed in kilobars. The 90 percent confidence band about the calibration curve has been computed, and the curve has been used to determine the room-temperature freezing pressures of acetone and methylcyclohexane.

The Electron Microprobe X-Ray Analyzer and its Use in Soil Investigations

Abstract: Publisher Summary The electron microprobe analyzer is an exciting new analytical tool. Soil scientists are now able to analyze nondestructively and in situ the chemical composition of microscopic and submicroscopic soil volumes. The microprobe analyzer is capable of detecting, for most elements, concentrations as low as 100 ppm. The detection limits depend on operating conditions. The analysis, although simple in concept, is complicated in practice by the fact that the X-ray intensities measured by the detector systems are not the true intensities generated within the sample or standard. Thus, when the single standard method of analysis is employed, corrections are necessary for mass absorption, secondary fluorescence, and atomic number effects arising from the interaction of incident electrons and generated X-rays with atoms in the sample. Multiple standard methods that obviate the need for corrections represent an alternative to the single standard method. These employ calibration curves generated from the X-ray intensities measured from a series of well-defined, homogeneous multielement compounds. The nature and size of the soil material to be analyzed dictates the method of sample preparation. The examples of electron microprobe analysis of soil concretions, mineral inclusions, and micas are given in the chapter.

Determination of chelated iron in the urine

Abstract: A simplified wet-ashing technique is described for the determination of chelated iron in the urine, with special reference to DTPA-bound iron. The procedure dispenses with the need for quantitative transfer, and gives corresponding economy in time, labour, and glassware without loss of precision. The standard error of the mean estimate of a triplicate determination, using four reference standards, is ± 4 μg/100 ml; precision may be further increased by the use of a calibration curve based on many standards.

The calibration of tool/work thermocouples

Abstract: The limits of accuracy imposed on the tool/work thermocouple technique by the need for an exact calibration curve for the materials used has been investigated. The materials used included various grades of tungsten carbides, calibrations being performed against a 0·20% carbon steel. Results are presented which illustrate how the emf generated is affected by changes in the sintering times, the cobalt content, and the size of the carbide members of the thermocouple. Calibration curves for a tungsten cobalt-carbide in various conditions are compared with those for a steel cutting grade containing titanium and tantalum carbides, and with a sample of 18/4/1 high-speed steel. Two calibration methods are recorded—the usual furnace arrangement, and a method for heating the carbide/steel interface using radio-frequency induction heating.

A Magnetostrictive Load Cell for Use under High Hydrostatic Pressures

Abstract: A load cell utilizing magnetostrictive strain gauges which is suitable for measuring loads up to 300 kg in tensile testing of materials under high hydrostatic pressures up to 15000 kg/cm2 is described. Temperature and pressure variations during tensile testing can be completely compensated by the use of a dummy gauge. The calibration of the load cell under pressure is performed by a coil spring which is calibrated at atmospheric pressure. The calibration curves under pressures up to 13400 kg/cm2 and 200 kg agree with the atmospheric calibration curve within 2%.

The calibration of a high-sensitivity large area whole-body counter.

Abstract: The whole-body counter considered is based on a design which uses total internal reflection as the method of light collection. It is shown that a calibration curve in which the response of the counter is plotted as a function of weight is adequate over a wide range of patient size. The results are compared with those obtained with a whole-body counter based on the cylindrical design, and it is shown that the calibration of the two types of counter is similar.

Two radiometric methods for the fast determination of calcium in cement raw mix

Abstract: Fast determination of calcium in cement raw mix is a very important problem from the economic point of view. In order to solve this task, the following two methods are proposed: (i) Non-dispersive X-ray fluorescence analysis (using109Cd as a source of primary radiation); (ii) back-scattering of β-particles (using90Sr+90Y as a source). The influence of the following factors has been studied in both methods: (i) concentration of iron in the matrix; (ii) water content; (iii) grain size of the sample. The influence of the energy of the primary radiation on the slope of a calibration curve has been analyzed in the fluorescence method. In the concentration range of 42–52% CaO, the absolute standard error is 0.17% CaO in the fluorescence analysis, and 0.5% CaO for the method of back-scattering of β-particles. The average time of a determination is about 2 min.

Analysis of Solders by X-Ray Spectrometry

Abstract: The determination of several percent of Au, Ag, and Cu in various Sn/Pb solder compositions used in the manufacture of microelectronic circuits is described. Details of the preparation of standards and x-ray procedure are given. The Au calibration curve can be prepared from any Sn/Pb composition. The Ag and Cu calibration curves must be prepared for each solder composition.

X-Ray Fluorescence Method for the Quantitative Analysis of Light Elements in Chemically Treated Cottons and Other Agricultural Products

Abstract: X-Ray fluorescence analysis has been used for the quantitative determination of the light elements P, S, and Cl, which are used in the chemical treatment of cotton and cotton fabrics. Determinations of the amounts of resins used in the chemical modification of cotton cellulose and cotton fabrics have become increasingly important with the extensive use of such treatments. Chemical methods for these determinations are frequently time consuming and often lack the required sensitivity. If the resin treatment contains a metallic or nonmetallic element not found in cellulose (as is frequently found in the use of organometallic compounds or of simple inorganic salts and oxides), the amount of resin can be calculated from a determination of the specific element. This approach, in turn, requires a rapid, sensitive, and accurate method for the determination of the selected element. The wet-chemical methods for these elements are difficult and time consuming. X-Ray fluorescence has fulfilled this need and determination of these and other elements is performed on a routine basis. Matrix problems which may arise due to the nature of the cellulose material are circumvented by the use of standard disks, which are prepared by adding known quantities of the element with a cellulose material such as cotton and pressing it into a disk. The x-ray fluorescence measurements yield calibration curves which are linear in the range from 0.03% to 10% concentration of the element in the cotton.

Determination of silicon in rocks by fast-neutron activation analysis using internal standards.

Abstract: A technique for using internal standards in the determination of Si in rocks using fast neutron activation is presented. Different weights of barium acetate were irradiated for 30 seconds then cooled for 10 seconds before counting for one minute. A peak area, at 0.662 MeV due to137mBa, versus weight of barium calibration curve (I) was made. Similarly, barium acetate, which served as the neutron flux monitor, was mixed with known weights of standard rocks, BCR-1 and G-2. Then a peak area (at 1.78 MeV due to28Al) versus weight of silicon (present in the standard rocks) calibration curve (II) was constructed which was corrected for flux variations. Flux corrections were made possible using curve (I). Utilizing curve (I) and curve (II) the percentage Si in granite samples obtained from Llano, Texas, was determined. This technique avoids any external neutron monitor or sample rotation system. The applicability of this approach may be limited to samples in which the internal flux monitor can be dispersed.

Calibration of pole tips suitable for a magnetic balance

Abstract: Calibration curves, derived from absolute susceptibility measurements are given for four-inch Henry profile pole tips at gaps from 5 cm to 2?5 cm, for several magnetizing currents. The region of `constant force' permits accurate measurements on samples of limited size.

Dielectrically Heated Sensor of Water-Vapor Pressure

Abstract: Existing psychrometers of small dimensions cannot provide accurate long-term measurements of water-vapor pressure without frequent maintenance and recalibration. A small, simply constructed instrument employing dielectric heating and avoiding many of the problems of available sensors is described. The calibration curve depends only on the pressure-temperature curve for saturated lithium chloride.

Eriochrome Cyanine R Method for Aluminum Determination

Abstract: Fig. 1. Calibration Curve for Lower Concentration Ranges of Aluminum centration of aluminum to be 0.006 mg/l in a 25-ml sample. This corresponds to an absolute concentration of 0.15 fig of aluminum in the 25-ml sample. The minimum detectable concentration reported by Knight 2 was 0.004 mg/l, that is, 0.1 fig in a 25-ml sample. Studies in the authors' laboratory have shown that, using a light path of 4 cm, a concentration as low as 0.002 mg/l (0.05 fig in a 25-ml sample) could be determined precisely and accurately. Figure 1 shows the calibration curve for lower concentration ranges of aluminum.

Part 2. Pressure Scale and Fixed Point

Abstract: A straightforward measurement of pressure involves measuring a force and an area. Several types of high pressure apparatus are very difficult to calibrate so as to know the pressure at the sample because a relatively unknown fraction of the force is dissipated in friction between moving parts of the pressure apparatus or lost to internal friction within the gasket material surrounding the sample. The area over which the pressure is applied is also a difficult problem at high pressures because of compression of the high pressure apparatus. These types of apparatus are most generally ‘calibrated’ by arriving at a correspondence between the load applied and the sample pressure. This is accomplished by replacing the sample with some material which experiences a phase change at some known pressure and noting the load at this change. This gives a point on the load pressure calibration curve. Several such points are measured and then connected with a smooth curve. Of course, the above presupposes that there has been a measurement of the pressure at which these phase changes take place.

Simultaneous Spectrographic Determination of Nickel, Manganese and Chromium by Plasma Jet Arc Technique

Abstract: A Shimadzu-type plasma jet arc unit equipped with a ceramic nozzle was employed in this study.Various parameters of the plasma jet arc were quantitatively studied, their interrelations were clarified, and criteria for the optimum conditions were establshed.Distance of the analytical gap, position of the cathode, flow rate of helium, plasma flow, arc resistance operating current and voltage, sample size, spatial distribution of the ratio of line intensity to back-ground in the analytical gap, and influence of extraneous elements on the spectral intensity of the aimed elements were investigated.As a result, the simultaneous determination of consituent elements in various metals and alloys has been proved to be possible by the use of a plasma jet arc without any matrix effect.Single, widely applicable calibration curves for nickel, manganese and chromium were obtained by the use of acidic solutions of the standard samples.The plasma jet arc unit described here can be utilitized as a practical device durable for long runs.

Direct Determination of Iron Content in Used Greases by X-ray Fluorescence Method

Abstract: Direct determination of iron content in used greases by X-ray fluorescence method has been investigated. The following conclusions were obtained from the experimental results.(1) Standard samples were prepared by adding Fe-naphthenate or Fe2O3 to Li-grease and Na-grease to give 0.003∼1.5wt% iron content.Colorimetric analysis values of iron content in these standard samples were used as standard values and a linear calibration curve was obtained in the X-ray fluorescence analysis. Standard deviation of X-ray fluorescence analytical method was 2.6% at lower range of iron concentrations and 0.7% at higher range of iron concentrations. And also, standard deviation of the difference of colorimetric and X-ray results was 3.0% at lower iron concentration range and 0.9% at higher iron concentration range.(2) The X-ray fluorescence analytical results of iron content in various grease samples which were used in field test of motor cars checked well with the results of colorimetric analysis.(3) As this procedure is a direct method of determination of iron content in greases without ashing treatment, it is considered that this method is simple, rapid (15∼20 minute/one sample) and very useful for routine analysis.

Management of Routine Works for Photoelectric Emission Spectrochemical Analysis of Iron and Steels

Abstract: In the routine works of photoelectric emission spectrochemical analysis in a research laboratory for Iron and steel industry, where many kinds of steels are treated, standard samples have to be carefully selected to provide calibration curves reliable enough for any specimens.The preparation method of the calibration curves and the controlling method to minimize the errors developed in the author's laboratory are reported.

Suggested nuclear depth-gage calibration procedures

Abstract: AN EXPERIMENTAL PROCEDURE FOR CALIBRATION OF NUCLEAR DEPTH MOISTURE AND DENSITY GAGES IS DESCRIBED. CALIBRATION OF THE GAGES WAS ACCOMPLISHED UTILIZING LABORATORY STANDARDS CONSTRUCTED OF NATIVE OKLAHOMA SOILS. THE SOIL STANDARDS WERE COMPACTED TO A KNOWN DENSITY AND MOISTURE CONTENT. ONE SAND AND TWO COHESIVE SOILS WERE EMPLOYED. THE CALIBRATION CURVES FOR THE GAGES INDICATED THAT SOIL TYPE INFLUENCES INSTRUMENT RESPONSE. EACH SOIL HAD A SEPARATE AND UNIQUE CALIBRATION CURVE FOR MOISTURE CONTENT AND FOR DENSITY. THE USE OF DUAL-PURPOSE STANDARDS, TO CALIBRATE BOTH MOISTURE AND DENSITY GAGES, WAS PROVEN DESIRABLE. SPECIFIC CALIBRATION CURVES ARE RECOMMENDED FOR PROJECT USE. /AUTHOR/