Showing papers on "Calibration curve published in 1976"
TL;DR: An automated method for the determination of submicrogram amounts of selenium in vegetation is described and a relative standard deviation of better than 10% and a detection limit of 0.025 microg/g were obtained.
58 citations
TL;DR: In this paper, a continuous method for calibration and measurement with ion-selective electrodes is developed, where the electrode is immersed into a solution diluted with respect to one of the components which influence the potential of the electrode.
41 citations
TL;DR: In this paper, a simple chemiluminescence photometer is described, where the sample is injected into a spectrophotometric cell containing the reagents, and the resultant chemilumininescence peak is recorded along with the peak height and peak area.
40 citations
TL;DR: In this article, two samples of cellulose (molecular weight 2.97 × 105 and 1.25 × 105) were transformed into carbanilates (CTC) which were then fractionated by the elution method at a constant composition of the acetone-water elution mixture with the column temperature gradually increasing from −30°C to 30°C, and by the GPC method in acetone and tetrahydrofuran.
Abstract: Two samples of cellulose (molecular weight 2.97 × 105 and 1.25 × 105) were transformed into carbanilates (CTC) which were then fractionated by the elution method at a constant composition of the acetone-water elution mixture with the column temperature gradually increasing from −30°C to 30°C, and by the GPC method in acetone and tetrahydrofuran. Tetrahydrofuran appeared to be a more suitable solvent. The molecular weights of fractions obtained by the elution fractionation were determined by the light-scattering method in tetrahydrofuran. The width of fractions was determined by the GPC method (average Mw/Mn = 1.37); the [η] values and the Mark-Houwink constants (K = 5.3 × 10-3, a = 0.84) for tetrahydrofuran at 25°C were determined. The calibration curve for the GP method was constructed by means of the fractions thus obtained; it was demonstrated that the universal calibration curve according to Benoit can also be used. It was demonstrated that the molecular weight distribution of cellulose can be conveniently determined by conversion into CTC followed either by the elution fractionation (for preparative purposes) or by fractionation by the GPC method (for analytical purposes).
34 citations
TL;DR: In this article, the linearization of the callbratlon curve of the automated methylthymol blue (MTB) procedure for the determination of sulfates is described.
Abstract: The linearization of the callbratlon curve of the automated methylthymol blue (MTB) procedure for the determination of sulfates is described. Thls is accomplished by altering the barium-to-MTB molar ratio of the barium-MTB reagent used. Because of the low purlty of the commerclal dye, bariumto-MTB molar ratios of 0.9:l or lower are usually needed for obtaining linear callbratlon curves. A llnear relatlon between absorbance and sulfate concentration with a correlatlon coefficient of 0.9995 or better is obtained. The relative standard deviation among repllcates, in the range of 0 to 100 pg/ml, is 1.4 to 0.4%. The sensitivity for this range is 4 pg/ml SO4*-.
25 citations
TL;DR: In this article, the chlorophyll content in rapeseed was estimated by reflectance spectroscopy and the accuracy of the procedure was±1.2 ppm when compared to another published procedure.
Abstract: In a new, rapid procedure, the chlorophyll content in rapeseed was estimated by reflectance spectroscopy. The seed was ground in a specially designed grinder. The reflectance of the ground seed was read at 630, 670, and 710 nm. Corrected absorbance at 670 nm was used to determine the chlorophyll content of the seed by using a calibration curve. The accuracy of the procedure was±1.2 ppm when compared to another published procedure.
24 citations
TL;DR: In this paper, the target composition of one homogeneous layer of foreign atoms in bulk material is determined by comparing the yields for proton-induced x rays at two different energies, and an approximate method of solution is given.
Abstract: We attempt to determine the target composition of one homogeneous layer of foreign atoms in bulk material by comparing the yields for proton‐induced x rays at two different energies The problem is formulated mathematically and an approximate method of solution is given The method uses a calibration curve which is given by the ratio of the yields at the two energies for a pure foil of the foreign material of known surface density Both thickness and location in depth of the foreign layer can be determined The method is applied to sandwich targets (Ag‐Cu‐Ag and Ge‐Cu‐Ge) of known layer thickness (determined by Rutherford backscattering) By measuring the same target under various conditions, and by comparison to backscattering, it is shown that a mean depth of Cu atoms of about 1 mg/cm2 can be measured to an accuracy of about 4%
23 citations
01 Jan 1976
TL;DR: This statistical analysis is concerned with the precision and accuracy of the standard calibration curve for estimation of molecular weights in gel filtration and PAGE in the absence of SDS.
Abstract: Gel filtration (GF) and sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) are perhaps the most popular methods for estimation of protein molecular weights. However, the precision and accuracy of these methods have never been rigorously evaluated by formal statistical methods. In contrast, a detailed objective statistical analysis has been applied to PAGE in the absence of SDS (Rodbard and Chrambach, 1970, 1974). This statistical analysis is concerned with the following:
a.
What is the precision of the “raw” measurement, e.g., elution volume (V e ), partition coefficient (K av), mobility (M), or relative mobility (Rf)?
b.
What are the precision and accuracy of the standard calibration curve for estimation of molecular weights? This includes several questions : What is the dependent variable? Is the calibration curve linear? Are there any outliers? What is the appropriate model? Is “ weighting” necessary, and, if so, how is it to be done?
c.
What are the standard error and 95% confidence limits for the molecular radius (or molecular weight) for the “ unknown” protein?
23 citations
TL;DR: Differential pulse and d.c. sampled polarography have been used to investigate the reduction of ferrous and manganous ions from both hypolimnetic lake water and a synthetic solution of comparable alkalinity and ionic strength as discussed by the authors.
22 citations
TL;DR: Simultaneous qualitative analysis of fourteen sulpha drugs and their individual quantitative determinations have been performed by gas-liquid chromatography on solutions of dimethylformamide dialkylacetal derivatives of the drugs in acetone.
21 citations
TL;DR: In this article, the concentration of species at each elution point was obtained from a concentration-peak height calibration curve, and molecular weight at the point was calculated by using the usual method.
Abstract: In the calculation of molecular weight averages by GPC, the traditional method uses the calibration curve obtained at the same concentration as the samples, which results in a large degree of disagreement between molecular weight averages at several concentrations. Because of the concentration dependence of peak elution position in gel permeation chromatography of polymers, correct molecular weight averages cannot be obtained if calibration concentrations are the same as sample concentrations. A computation approach which uses calibration curves at finite and zero concentrations and can correct concentration effects is shown. The concentration used varied from 0.1% up to 0.4%. The elution chromatogram was divided into several parts, and concentration of species at each elution point was obtained from a concentration–peak height calibration curve. Molecular weight at the point was obtained from a molecular weight–elution volume calibration curve corresponding to a concentration of species at the point, and molecular weight averages were calculated by using the usual method. Nearly identical values for molecular weight averages could be obtained at different concentrations, and additional support for this approach is that these values for molecular weight averages were in fair agreement with NBS data.
TL;DR: In this article, an advanced methodology in mask correlation spectrophotometry is presented, by operating the instrument with its oscillating correlation mask placed in two chosen positions, a system to two equations can be solved in terms of the unknown optical depth of the gas.
TL;DR: In this paper, a fine filament of aerosol is continuously passing through a beam of laser light and the scattered light originating from single particles is collected under a mean scattering angle of 40° and is recorded photoelectrically.
TL;DR: In this article, a detailed theoretical analysis of signals in atomic fluorescence, including the effects of preabsorption under saturation conditions, is presented, compared with experimental measurements using a flashlamp-pumped dye laser.
Abstract: A detailed theoretical analysis of signals in atomic fluorescence, including the effects of pre-absorption under saturation conditions, is presented. These predictions are compared with experimental measurements using a flashlamp-pumped dye laser. A detection limit of 7 x 10/sup -15/ g/cm/sup 3/ of sodium is obtained using a simple arrangement. The calibration curves compare well with theory with no adjustable parameters. The wavelength dependence and the time dependence of the signals are also discussed. Peak intensity measurements are suggested to be more reliable than integrated intensity measurements for analytical purposes. (auth)
TL;DR: In this article, the ion-exchange resin-loaded filter papers are automatically and quickly carried out and the prepared and dried filters analyzed by energy dispersive X-ray fluorescence analysis.
Abstract: Analysis of dissolved elements in fresh water at concentrations from parts per billion to the high parts per million range can be carried out using 200–500 ml sampling volumes. Preconcentration using ion-exchange resin-loaded filter papers is automatically and quickly carried out and the prepared and dried filters analyzed by energy dispersive X-ray fluorescence analysis. Excitation by a filtered low power tube, subtraction of a blank filter paper spectrum, automatic computer stripping of peak overlaps and removal of spectrum background gives net elemental counts that can be used with linear calibration curves to directly obtain concentration values. The system and approach readily lend themselves to laboratory use as well as unattended operation.
TL;DR: In this paper, an initial rate method for trace amounts of cyanamide was developed, measured as the rate of increase in absorbance at 530 nm due to the purple SPF-cyanamide complex.
Abstract: The complexation of sodium pentacyanoammlneferrate(ll) (SPF) was studied to develop an initial rate method for trace amounts of cyanamide. The initial rate is measured as the rate of increase in absorbance at 530 nm due to the purple SPF-cyanamide complex. Stopped flow mixing and both multichannel (vidicon) and single channel (photomultiplier) detection were used. The reaction was shown to be first order in SPF and first order in the concentration of the cyanamide monoanion. A calibration curve for cyanamide is linear from 3 X M with a limit of detection of 13 ppb. A precision of 3.5% at the 95% confidence level was calculated for cyanamide determinations using this curve. M to 1 X
TL;DR: An application of the Zeeman effect is described by which calibration curves applicable to high analyte concentrations may be obtained, simply by increasing the magnetic field strength, while leaving the monochromator permanently set on the optimum analytical line for the element considered.
TL;DR: An extensive survey of radioimmunoassay calibration data for prednisolone, prednisone and digoxin indicated that the common practice of preparing calibration curves with individual subject's pre-dose plasma or serum, and using this to estimate unknown concentrations for the same subject, is not supported by statistical considerations.
TL;DR: In this paper, the effects of variables on treatment of the gel permeation chromatogram are reported, which include the molecular weight distribution of polymers for preparing the calibration curve, i.e., the logarithm molecular weight-elution count relationship, nonlinearity of the calibration, and fluctuation of the baseline.
Abstract: The effects of variables on treatment of the gel permeation chromatogram are reported. Variables investigated include (1) the molecular weight distribution of polymers for preparing the calibration curve, i.e., the logarithm molecular weight–elution count relationship, (2) nonlinearity of the calibration curve, and (3) fluctuation of the baseline. The deviation of the calibration curve prepared by the polymer having broad molecular weight distribution was evaluated in detail by assuming log-normal distribution function for the distribution. The polymer having a D value less than 1.3 was recommended for this purpose. Generally, the shape of the chromatogram is fairly different from that of the true molecular weight distribution curve when the calibration curve is not linear over the entire range of interest. By fitting polynomials to the calibration curve, the chromatogram was sufficiently converted to the molecular weight distribution curve. The apparent difference between them was removed. Slight deviation of the baseline from the true one gave rise to obvious error in the calculated molecular weight and its distribution, especially for the sample having a broad distribution.
TL;DR: In this paper, a FORTRAN computer program strategy is given for calculating the transform constant from emulsion calibration data and obtaining a linear equation for the emulsion calibrations, which is used to program a desk calculator to convert transmittance readings to intensity ratios corrected for background.
Abstract: Photographic spectrographic calculations of intensity ratios and the corresponding element concentrations are performed faster and more accurately with programmable desk calculators than by graphical methods. These calculations are facilitated by applying a transform to microphotometer transmittance readings to make them linear with respect to intensity. This transform has the form log [{(100 − T)/T} {(a + T)/T}] where a is the transform constant and T is percent transmittance. A FORTRAN computer program strategy is given for calculating the transform constant from emulsion calibration data and obtaining a linear equation for the emulsion calibration curve. This equation is used to program a desk calculator to convert transmittance readings to intensity ratios corrected for background. A second calculator program computes element concentrations from the intensity ratios.
TL;DR: In this article, a simple method for measuring potassium-ion concentration levels in drilling fluids used to stabilize water-sensitive shales has been developed, which is a centrifuge technique in which a chemical is added to a mud-filtrate sample to precipitate the potassium.
Abstract: A simple, reliable method for measuring potassium-ion concentration levels in drilling fluids used to stabilize water-sensitive shales has been developed. The method is a centrifuge technique in which a chemical is added to a mud-filtrate sample to precipitate the potassium. The sample is centrifuged in a special tube at a constant speed so the precipitate volume can be read accurately. The reading is compared with a calibration curve to obtain the potassium concentration in the filtrate. The procedure takes just over 1 minute and has given excellent results in laboratory and field tests.
TL;DR: In this paper, the thermometric determination of the Landolt effect applied to the hydrogen peroxide-iodide-ascorbic acid reaction is described, and appropriate kinetic equations are used to interpret the thermometer curve and the calibration curve of the indicator reaction catalysed by molybdenum.
TL;DR: Experiments in a wind tunnel showed that this was the case for more than 80% of a test series of the modified anemometers, and the time constant has increased but is still acceptable.
Abstract: An anemometer which was developed for indoor climate research has been modified in order to get the same shape of calibration curve for each anemometer. Experiments in a wind tunnel showed that this was the case for more than 80% of a test series of the modified anemometers. The time constant has increased but is still acceptable. Calibration curves and time constants could be predicted by calculation with reasonable accuracy. Some influence of dust particles on the instrument was noticed.
TL;DR: A Fortran IV computer program is used to calculate absorbance at varying wavelengths in a UV-visible rapid scanning spectrophotometer, because the voltage output of the computer is automatically identical to the actual absorbance of a sample.
Abstract: Sir: A Fortran IV computer program is used to calculate absorbance at varying wavelengths in a UV-visible rapid scanning spectrophotometer Using the program eliminates the necessity of calibrating the absorbance axis in the usual manner using standard solutions or filters and plotting calibration curves, because the voltage output of the computer is automatically identical to the actual absorbance of a sample