Showing papers on "Calibration curve published in 1975"

The quantitative analysis of thin specimens

Abstract: SUMMARY Results are reported concerning the use of an energy dispersive X-ray detector to carry out the analysis of thin foils in the electron microscope. The combination of a thin specimen and the extreme stability of the energy dispersive X-ray detector enables the experimental determination of a calibration curve of X-ray production—detection efficiency vs characteristic X-ray energy. Quantitative analysis can be carried out using the calibration curve without reference to standards at the time of analysis.

A calibration curve for radiocarbon dates

Abstract: DY Malcolm Clark was a research student in the Department of Statistics in the University of Shefleld and when there worked in collaboration with Professor Renfrew. His Ph.D was on the statisticalproblems of C I ~ calibration, and he here presents us with an objectively derived calibration curve for radiocarbon dates which will be of great value to all archaeologists. He is now Lecturer in Statistics in the Department of Mathematics, Monash University, Clayton, Victoria, Australia.

Chemical analyzer with automatic calibration

Abstract: Improved apparatus for automatically calibrating and verifying the calibration of a chemical analyzer of the type which determines the concentration of a component in chemical or biological samples, e.g. concentration of glucose in blood or urine, wherein a sample changer sequentially advances samples into position for analysis. Calibration of the analyzer is performed by measuring a calibration standard of known concentration and generating a conversion factor therefor which converts the measured value of the standard to the known value thereof. Means is provided for storing conversion factors and proper calibration of the analyzer is verified by comparing successive conversion factors. If the compared conversion factors differ by more than a predetermined amount, the sample changer is halted and the calibration standard is remeasured. Measurement of the calibration standard is repeated until either two successive calibration factors are generated which differ by less than the predetermined amount, or until a predetermined number of unsuccessful measurements are made at which time the analyzer is stopped.

Simple calibration procedures for platinum resistance thermometers from 2.5 to 14 K

Abstract: Calibration procedures are developed for platinum resistance thermometers in the temperature range 2.5–14 K. Two recommended methods require calibration points at the boiling point of liquid helium (4.215 K) and the triple point of hydrogen (13.81 K); in addition, the first method requires a point at 7.201 K while the second method requires the slope of the calibration curve at 13.81 K. For temperatures from 3.5 to 14 K, the calibrations are accurate to within 0.01 K for the first method and 0.025 K for the second method. For temperatures from 2.5 to 3.5 K, the calibrations are somewhat less accurate. Therefore, if a thermometer has been calibrated for temperatures of 13.81 K and above, its calibration may be easily extended to lower temperatures with sufficient accuracy for many applications. These calibration procedures were developed from two‐way structural analysis of the accurate calibrations of 12 platinum resistance thermometers.

Gel-permeation chromatography calibration curve for asphaltenes and bituminous resins

Abstract: For the determination of molecular-weight distributions by means of gel-permeation chromatography, one needs a calibration curve which relates molecular weight to elution volume Such a curve has been constructed for high molecular bituminous components by combining the chromaiograms partly with molecular-weight distributions derived from velocity ultracentrifugation, partly with measured average molecular weights It proved possible to calculate the calibration curve for asphaltenes when that for polymers is known Benoit's universal calibration curve, in which the product of molecular weight and limiting viscosity number is used as a measure of the hydrodynamic volume, does not apply for asphaltenes

Exclusion chromatography using porous glass. II. Application to hydrophilic polymers

Abstract: A chromatograph employing five columns packed with porous glass of pore size 1250 A to 75 A provided peak retention volumes (VR) that were reproducible and essentially independent of sample size and flow rate when aqueous eluents were used. Calibration was carried out with a series of dextran fractions and polystyrene sulfonate samples, both of moderately narrow molecular weight distribution. The universal calibration method, based on hydrodynamic volume, was tested for four different polymer types. All four types produced a common curve within experimental error, which indicates that absolute molecular weight distributions may be derived from aqueous exclusion chromatography data for at least these polymer types. Additional study using a higher salt concentration produced hydrodynamic-volume plots that superposed with those above. The use of the same set of porous glass columns with polystyrene standards in three different organic solvents produced calibration curves that agreed well with the aqueous curves after corrections were made for differences in available pore volumes.

Determination of aluminium in dental enamel by the carbon cup atomic-absorption method.

Abstract: The possibility of using the carbon cup atomisation technique for the atomic-absorption determination of aluminium in dental enamel has been investigated. Various parameters that influence the sensitivity and accuracy of the measurements were studied by use of a standard electronic detection system (Varian AA-5; chart recorder f.s.d., 1 s) and oscilloscopic (Tektronix) recording of the absorption signal. The latter system enabled the atomic-and non-specific absorption signals to be studied as a function of the time of atomisation. Thus, increasing the rate of heating of the carbon cup in the atomisation step resulted in a substantial enhancement of the aluminium peak absorption signal. The presence of calcium in the solution (7·2 mg ml–1, in the form of the phosphate) produced a two-fold increase in sensitivity for aluminium.For routine determinations of aluminium in tooth material (in vitro) 10 mg of finely ground and homogenised sample are dissolved in 6 N nitric acid and the solution is diluted to 0·5 ml; 5-µl aliquots are sampled for a single determination. A single calibration graph obtained by the standard addition method is adequate for one set of samples. No correction due to non-specific absorption is necessary, but the blank value (nitric acid) should be checked from time to time.The absolute sensitivity of the method (3·5 × 10–11 g of aluminium) permits the determination of aluminium in tooth material both in vitro and in vivo at microgram per gram concentration levels with a general precision of 8 per cent. In vivo analysis can be carried out on 300–600 µg of sample obtained by a chemical biopsy method. The main problem encountered in in vivo analysis lies in obtaining an aluminium-free support material for etching purposes. In addition, “clean room” facilities are recommended for improving the accuracy.

Practical Applications of Radioimmunoassay Theory. A Simple Procedure Yielding Linear Calibration Curves

Abstract: The fundamental equation describing radioimmunoassays under equilibrium conditions has been recast into a "working equation" in a form more directly applicable to the requirements of the analytical laboratory. Plotting total counts over counts bound vs. ligand concentration, which is conveniently linear over most of its course, is shown readily to yield quantitative data relative to binding site concentration and the equilibrium constant and to provide a means for deriving apparent labeled ligand concentration. Such data are helpful in establishing optimum assay conditions and can serve a continuing quality-control function. The working equation also characterizes the binder and tracer reagents used in the assay. The determination of working-equation parameters has been illustrated for the vitamin B-12 assay. Data are presented for seven different assay procedures, involving more than 600 calibration curves and 100 different lots of binding agent and tracer reagent, showing a consistently high correlation coefficient (r greater than 0.990), between ligand concentration and the response variable.

Calibration Designs for Machines with Carry-Over and Drift

Abstract: Continuous-flow analysers (like the Auto Analyser and its current version SMAC) require individual calibration to verify the shape of their calibration curves, of the amount of sample-to-sample carryover, and of the extent of linear and quadratic time-d..

Photometric method for the quantitative determination of a material or substance in an analysis substance and photoelectric photometer for the performance of the aforesaid method

Abstract: A photometric method and photoelectric photometer for the quantitative determination of a substance or material in an analysis substance, wherein the course of the calibration curve representing the functional dependency of an optical measurement magnitude upon the concentration of the substance can be at least approximately determined by at most a number of few parameters. For a calibration curve parameter there is provided a reference sample which contains the substance to be analyzed in a known or unknown concentration. A partial quantity is removed from the analysis substance to serve as the analysis sample and there are formed from further partial quantities of the analysis substance corresponding to the number of further calibration curve parameters calibration samples by the addition of predetermined graduated quantities of the substance to be analyzed to the partial quantities of the analysis substance, so that each calibration sample contains the material to be analyzed in a concentration which is composed of the unknown proportion and a known proportion. The analysis sample, the reference sample and the calibration sample(s) are illuminated and for all samples there are at least approximately simultaneously determined the values of the optical measurement magnitudes, and by means of the measurement magnitude values there is mathematically determined from the course of the calibration curve determined by such measurement magnitude values and the known concentration of the material to be analyzed in the reference sample the concentration of the material or substance in the analysis sample.

Semi-Solid Surface Fluorometric Analysis of Glucose

Abstract: We describe an enzymatic fluorometric method for determining glucose concentrations in blood samples by analysis on a semi-solid surface (silicone-rubber pads). The method is an adaptation of existing spectrophotometric procedures based on the sequential coupling reactions with glucose-6-phosphate dehydrogenase and NADP+. The rate of appearance of NADPH fluorescence at 460 nm (excitation wavelength, 340 nm) is monitored and related to the glucose concentration in plasma or serum. The calibration curve is linear to 2.50 g/liter. The chief advantages of this method over the spectrophotometric procedure are low cost and rapid response. The results obtained correlate well with those of the o-toluidine method (correlation coefficient, 0.986).

Advances in Chlorine‐Residual Analysis

Abstract: / = log -i/2.78242 x 6.56 2.548 x 3.51988 ' ' 4 X 2.78242 -(2.548)2 J The mathematically formulated equation, log T= 0.56829C + log 100, considered to be the best fit of the analytical calibration curve, was then used for calculating the standard deviation, relative standard deviation, range, absolute error, and relative error for the modified methylene blue method (see Table 5) and the experimental LAS concentrations (see Table 6).

Fluorescence detection of nitric oxide in nitrogen.

Abstract: An accurate, rapid, and simple technique is described for the measurement of nitric oxide (NO) in standard reference mixtures of NO in N/sub 2/. It is based on the fluorescence intensity emitted by NO when it absorbs 213.8 nm radiation from a Zn discharge lamp. This intensity increases linearly with NO concentration in the 0.015-7 ppM range to within 1 percent error. The application of this method to detect NO and sulfur dioxide (SO/sub 2/) in automotive exhausts is discussed. By the method described, fluorescence signals from several NO-in-air mixtures were measured. The responses were almost linear with concentration. Small amounts of SO/sub 2/ interfere with the detection, but this may be minimized by using a filter transmitting in the region of 230-300 nm, corresponding to the NO fluorescence spectrum. Because of large concentrations of quenching gases, mainly H/sub 2/O and carbon dioxide, in automobile exhausts, the fluorescence signal of NO would be considerably less than the signal from the same concentration of NO present in pure N/sub 2/. An equation is given to calculate this effect when the composition changes within a stated range. Diluting the exhaust gas 1:100 with N/sub 2/ provides an almost linear calibration curve formore » measuring NO in the range of 30-3,000 ppM. If the exhaust gas is diluted by air or O/sub 2/, and a filter transmitting light of wave lengths 300-420 nm is used, it is possible to measure SO/sub 2/.« less

Linear instrument calibration with statistical application

Abstract: Quantitative determinations involving instrumentation are often accomplished by establishing a calibration curve Readings from the particular instrument are plotted against known concentrations of standards and the concentration of the analyte in the sample evaluated by the underlying relationship of the calibration line If the calibration is linear, or nearly linear such that a straight line provides a reasonable approximation, the concentration of the sample can be readily determined if it falls within the range of the standards

Fluoridbestimmung in Knochenproben vom menschlichen Beckenkamm mit einer ionenselektiven Elektrode

Abstract: A simple potentiometric method for the determination of fluoirde ion in human bones is described. The bone samples were taken from a definite position in the iliac crest. The samples are prepared for analysis by ashing at 550 degrees C, dissolving in HNO3 (4 mol/1) and adjusting the pH with NaOH (4 mol/1) and Total Ion Strength Adjustment Buffer, Absolute values are derived from a calibration curve based on aqueous NaF-buffer solutions. The calibration curve is linear in the range 5.2-10(-3)-1.0-10(-5) mol/1F-. The minimum limit of measurement is 5.2 X 10(-6) mol/1F-. The method has an accuracy of 96.1 % or 92.3% with a series precision based on the Pearson variability coefficient of 1.68%. The normal mass fraction of fluoride in human bones was found to be between 69 and 1740 - 10(-6) F-/ash.

Radiometric analyzer with plural radiation sources and detectors

Abstract: A radiometric analyzer for measuring characteristics of a material by radiation comprises a plurality of systems in which each consists of a radiation source and a radiation detector which are the same in number as the number of elements of the molecule of the material and a linear calibration circuit having inverse response characteristics (calibration curve) of the respective systems of detectors, whereby the measurement is carried out by a four fundamental rules operation of the mutual outputs of said detector system obtained through said linear calibration circuit. One typical embodiment is a radiometric analyzer for hydrocarbons which measures the density of heavy oil, the sulfur content and the calorific value by three detector systems which include a γ-ray source (E.sub.γ > 50 KeV), a soft X-ray source (Ex ≈ 20 Kev), and a neutron ray source.

The use of broadband signals for underwater acoustic transducer calibration

Abstract: : A preliminary study of the potential use of broadband signals for underwater acoustic transducer calibration has been made. Emphasis was placed on pulses of a single cycle of a sinusoidal wave as the calibration signal. The experiments involved digital sampling of the current and voltage response waveforms, generating the Fourier transforms of these responses, and combining the transforms to provide the desired calibration curves. The results were considered comparable to those obtained with conventional operational systems, even though smoothing was not applied to the data and even though compromises were required in performing the experiments. Preliminary noise analyses included the development of certain useful probability density functions and cumulative probability distribution functions. Curves to illustrate these probability functions are plotted. Some interpretation of noise effects is given. Future research plans are described briefly.

Determination of a binary calibration curve with one or two standard specimens in X‐ray flourescence analysis

Abstract: Two simple approximate formulae have been derived for binary calibration curves. These formulae contain one or two constants, which can be determined experimentally with one or two standard specimens, respectively. These formulae can be applied within a wide range around the composition of the standard specimen. These approximations can be used both in X-ray and in isotope excited fluorescence analysis.

[A simple photometric test for the routine determination of delta-aminolaevulinic acid in urine for the control of lead exposure].

Abstract: A simple and accurate method for determining urinary concentration of delta-aminolaevulinic acid (delta-ALA) is described. It is based on an improved application of the principle, first introduced by Tomokuni and Ogata, that a colourless pyrrole derivative is produced by the action of acetic acid ethyl ester on delta-ALA, which develops a violet colour on addition of Ehrlich's reagent. The influence of interfering substances was found to account for 20 plus or minus 3% in all examined urines samples. It is, therefore, recommended that an aqueous delta-ALA standard be prepared which contains only 80% of the concentration used in the calculation. Exact values are obtained in this way and the need for setting up a calibration curve by adding delta-ALA is avoided.

Radiodünnschichtchromatographische Spurenbestimmung von Dithionsäure

Abstract: A modified method of isotope dilution analysis is described for the determination of small amounts of dithionic acid (1–10 μg). The conditions for the setting up of the calibration curve are reported. The inactive dithionic acid is labelled with35S compound. After separation by thin layer chromatography on extremely thin layers the activity profiles of the spots are measured. The reduced maximal intensities are plotted against the amount of dithionic acid. The calibration curve is also valid for solutions containing up to 1M of sulphuric acid.

Einige Aspekte der Quantitativen Röntgenemissionsanalyse Leichter Elemente bei Anregung Mit Schweren Teilchen

Abstract: The aim of the paper is the simplification of calibration procedures in the investigation of multi-element-systems by calculating calibration curves. This requires, as well as taking into account the measuring geometry and the detector properties, above all the calculation of the number of the characteristic X-rays emitted by the sample per incident particle. For the calculation of the thick target yield a computer programme has been developed which makes possible a simple exchange of subroutines describing the stopping power of the sample, the cross-section of K-shell ionization, the fluorescence yield and the matrix absorption for the resulting K-X-rays of the elements contained in the sample. The agreement between experiment and calculation is discussed, when various approximations for the functions mentioned are used, as well as the possible influence of the grain size and surface roughness of the samples on the measurements, on which the calculations are based.

Evaluation of the anthracene-benzene chemical light meter for ecological research.

Abstract: The anthracene-benzene chemical light meter is used in ecological studies to measure solar radiation. The meter absorbs only in the ultraviolet (UV) and, in principle, relies on the conversion, by solar UV, of anthracene to dianthracene. In practice, the investigator uses a calibration curve to convert decrease of anthracene in solution to solar radiation received. Our results show that significant errors occur when a calibration curve is used under different atmospheric conditions than those under which it is prepared. The reason is that the ratio of solar UV to other portions of the solar spectrum reaching the earth's surface is modified by atmospheric conditions. Furthermore, percentage of UV in the solar spectrum is modified by latitude, season, time of day, atmospheric pollutants and layers of water and vegetation. Thus, successful use of light meters that utilize chemical conversions by solar UV to measure other portions of the solar spectrum are dependent on the preparation of a calibration curve for each condition under which the meter is used.

Rapid Method for Background Corrections Analysis by X-Ray Fluorescence: An Extension

Abstract: A method is described whereby a sample's background intensity at the Ka wavelength of an element can be obtained by reference to a calibration curve once its mass absorption coefficient has been determined by the Reynolds' method. Data presented indicate that, in standards with po ,i ranging from 7 to 20 (most rocks and minerals), the reciprocal of the background intensity at the desired Ka line is linearly related to rr so long as the standards are free of the analyzed element. The relationship remains linear even though the analyzed element occurs in the target or other parts of the spectrometer. For routine analysis involving many samples, an accurate estimation of background can be obtained from the analyses of as few as four standards, foregoing the time spent measuring the background of each sample.