Linearity calibration curves

When the internal standard s concentration cannot be held constant the data must be plotted as (SA/Sis)stand versus Ca/Cis, giving a linear calibration curve with a slope of K. 

A calibration curve shows us the relationship between the measured signal and the analyte s concentration in a series of standards. The most useful calibration curve is a straight line since the method s sensitivity is the same for all concentrations of analyte. The equation for a linear calibration curve is... 

In the experiment was determined that for linear calibration curve for CrKa in GSO PG24-PG31 the standai d error was 0.045%. The application of theoretical corrections method enables a decrease of that value to the level of 0.013%. In case when for the analytical parameter is taken the ratio L /L the standai d deviation decreases to 0.002%. 

The intensity of the emitted fluorescence In is, therefore, directly proportional to the amount of substance applied a This relationship is much simpler than the Kubelka-Munk function and always leads to a linear calibration curve passing through the origin If this is not true then interference is occurring [5]... 

Polysaccharides TSK-GEL GMPWxl TSK-GEL GSOOOPWxl -I- TSK-GEL G3000PWxi Large pore size, linear calibration curve, small particles, high resolving power... 

Small TSK-GEL G2500PWxi TSK-GEL Super SW2000, TSK-GEL G2000SWXL or SW Linear calibration curve, high resolving power... 

Synthetic polymers TSK-GEL GMPWxi TSK-GEL GSOOOPWxl G3000PWxl Large pore size, low adsorption, linear calibration curve... 

A linear calibration curve achieved using PLgel mixed gel columns infers several key advantages in SEC analyses. 

D. Comparison of Linear Calibration Curves of Shodex and TSK Columns... 

Due to the limitation of space, only the linear calibration curves for TSK, PSS, APSC, and PL PEO standards in water/methanol for the Shodex SB-806M... 

TABLE 17.7 Coefficient of Determination (R ) for Linear Calibration Curves for Four Linear Columns and Four Sets of PEO Standards... 

For all four sets of PEO standards the coefficient of determination (R ) for the linear calibration curves for the four linear columns in water and in water/methanol are better than 0.99, except for the PL PEO standards and the TSK GM-PWxl column in water/methanol. The coefficient of determination for the TSK GM-PWxl column in general is not as good as the other three linear columns. The coefficient of determination for the TSK PEO standards showed the least dependency on columns and mobile phases. The TSK GM-PWxl column has a lower exclusion limit in the high molecular weight range than TSK GM-PW, Shodex SB-806, and SB-806MHQ columns. 

External standard method (linear calibration curve of peak areas)... 

Cardone, M. J., Palermo, P. J., and Sybrandt, L. B., Potential Error in Single-Point-Ratio Calculations Based on Linear Calibration Curves with Significant Intercept, Ana/. Chem. 52, 1980, 1187-1191. 

The broad-standard linear calibration curves for polystyrene in THF in Figure 1 and 4 are used to illustrate the K and a calculations as follows. The particular calibration curves are found to correspond to the following calibration equations ... 

The log Mn vs. count calibration curve is shown on Figure 5. This is a fairly linear calibration curve, but it covers only a relatively narrow molecular weight range of 145,000 to 317,000 g/mole. Although we have sought to prepare higher MW samples for this purpose, we inadvertently obtained polymers with bimodal MWD s and did not use them for this calibration. 

Figure 2 Example of an apparently linear calibration curve drawn from nonlinear calibration data, calculated E > 0.999...

Instrument calibration is done during the analysis of samples by interspersing standards among the samples. Following completion of the samples and standards, a linear calibration curve is estimated from the response of the standards using standard linear regression techniques. The calibration constants obtained from each run are used only for the samples quantitated in that run. Drastic changes or lack of linearity may indicate a problem with the detector. 

A new nonweighted linear calibration curve is to be generated with every set of samples analyzed. The calibration standards are interspersed among the analytical samples, preferably with a standard between every two analytical samples, and injected into the HPLC/OECD system. The calibration curve is generated by plotting peak height of the detector response against the concentration for each calibration standard of EMA and methylated HEMA. 

The concentration of the analyte in the injected sample is determined based on the height or area of the analyte peak and interpolation of the internal or external standard linear calibration curve according to the following equation ... 

Once the concentration of the analyte in micrograms per liter has been determined in the injected sample, the remainder of the calculations is the same as for the linear calibration curve. 

Because of the possibility that the herbicide alachlor could adulterate food if either poultry or livestock consumed contaminated materials, Lehotay and Miller evaluated three commercial immunoassays in milk and urine samples from a cow dosed with alachlor. They found that milk samples needed to be diluted with appropriate solvents (1 2, v/v) to eliminate the matrix effect. One assay kit (selected based on cost) was also evaluated for use with eggs and liver samples from chickens. Egg and liver samples were blended with acetonitrile, filtered, and diluted with water. Linear calibration curves prepared from fortified egg and liver samples were identical... 

Pd removal was determined as follows. An aliquot of a representative liquid or solid sample was accurately weighed and subsequently digested by refluxing in nitric and/or hydrochloric acid using a closed vessel microwave procedure (CEM MARS5 Xpress or Milestone Ethos EZ). Cooled, digested samples were diluted, matrix matched to standards, and referenced to a linear calibration curve for quantitation an internal standard was employed to improve quantitation. All samples were analyzed by an Inductively Coupled Plasma Mass Spectrometer or ICP/MS (Perkin Elmer SCIEX Elan DRCII) operated in the standard mode. 

For complicated samples where matrix or interelement effects are present, a linear calibration curve may not be valid, and one should consider using an empirical model for concentration correction. This usually requires a large set of standards of similar composition to the unknown, which generally makes analysis rather impractical. Inter-element effects can be calculated from a basic knowledge of physical parameters in combination with the appropriate use of samples of known composition, pure elemental standards or composite standards. 

Cyclic voltammetry, square-wave voltammetry, and controlled potential electrolysis were used to study the electrochemical oxidation behavior of niclosamide at a glassy carbon electrode. The number of electrons transferred, the wave characteristics, the diffusion coefficient and reversibility of the reactions were investigated. Following optimization of voltammetric parameters, pH, and reproducibility, a linear calibration curve over the range 1 x 10 6 to 1 x 10 4 mol/dm3 niclosamide was achieved. The detection limit was found to be 8 x 10 7 mol/dm3. This voltammetric method was applied for the determination of niclosamide in tablets [33]. 

Alemu et al. [35] developed a very sensitive and selective procedure for the determination of niclosamide based on square-wave voltammetry at a glassy carbon electrode. Cyclic voltammetry was used to investigate the electrochemical reduction of niclosamide at a glassy carbon electrode. Niclosamide was first irreversibly reduced from N02 to NHOH at —0.659 V in aqueous buffer solution of pH 8.5. Following optimization of the voltammetric parameters, pH and reproducibility, a linear calibration curve over the range 5 x 10 x to 1 x 10-6 mol/dm3 was achieved, with a detection limit of 2.05 x 10-8 mol/dm3 niclosamide. The results of the analysis suggested that the proposed method has promise for the routine determination of niclosamide in the products examined [35]. 

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