Calibration Curve Method

Hasegawa et al. [76] measured miconazole serum concentration by a high performance liquid chromatographic method. The authors assessed whether the internal standard method produced an intra-assay error and found that the method gave more precise and more reproducible results compared to the absorption calibration curve method. With 0.5 pg/mL of miconazole, the coefficient of variation produced by that method was 3.41%, whereas that of the absorption calibration curve method was 5.20%. The concentration of absorptions calibration curve method showed higher values than the internal standard method. This indicated that the internal standard method was far more precise in measuring the miconazole serum concentrations than the absorption calibration curve method. 

Yamamoto et al. [6] studied preservation of arsenic- and antimony-bearing samples of seawater. One-half of the sample (201) was acidified to pH 1 with hydrochloric acid immediately after sampling, and the remaining half was kept without acidification. In order to clarify the effect of acidification on storage, measurements were made over a period of a month after sampling. Results are given in Table 1.1. In this study, a standard addition method and calibration curve method were used for comparison and it was proven that the two gave the same results for the analyses of seawater. 

In general, the calibration curve method is suitable for all samples where the test substance is not bound in complexes or when it can be liberated from complexes by suitable sample pretreatment. Otherwise, the compositions of the samples and of the standard solutions must be as similar as possible to obtain results with acceptable accuracy. In view of the ISE potential drift, the calibration must be repeated often (at least twice a day). As mentioned above, the precision of the determination is not particularly high with a common precision of the potential measureihent at a laboratory temperature of 1 mV the relative error is 4% for univalent and 8% for divalent ions [58], However, this often suffices for practical analytical purposes. An advantage is that the same precision... 

The quantitative estimation of copper in the postmodified material was carried out by AAS following complete dissolution using an HF/HNO3 mixture." The amount of copper was determined by a calibration curve method using a copper lamp of wavelength 324.8 nm and air/acetylene fuel (ratio of 3 1). 

Standard Calibration Curve Method. Samples of metal free blank oils of viscosities 20 and 75 (Cat. No. 254 C 20 and 254 C 75), respectively, were spiked ... 

Intercomparison of Methods, The speed of analysis where only one curve of the sample is recorded at the time of the analysis makes the calibration-curve method preferable in serial analysis of a large number of samples of similar composition. When precise results are required, temperature control is necessary, and when the capillary is blocked or broken, additional work for construction of a new calibration curve is necessary. The calibration-curve method is always used when the relation between the measured current and concentration is nonlinear (e.g., when catalytic or adsorption currents are dealt with). 

High-molecular-weight aliphatic amines are used extensively in many industries. The total primary- and secondary-amine content of aliphatic amines can be determined easily and rapidly by functional-group analysis in the near infrared [9], using chloroform solvent and 5-cm fused-silica cells. Primary amines have characteristic absorption maxima at 2.02 /um and 1.55 m, whereas secondary amines absorb only at 1.55 fim. Quantitation is achieved by the calibration-curve method using a series of standard solutions of primary and of secondary amines. Most other methods for the determination of total primary, secondary, or tertiary amine in a mixture are lengthy or inaccurate, or are unsuitable for small samples. 

The proposed method was ap>phed in the determination of total iron in river and seawater samples. Iron(III) and total iron were determined according to the FIA procedure as described in the experimental section. The results obtained by both, standard addition and calibration curve, methods were in good agreement with each other. Atomic absorption measurements taken in water samples 1 and 2 are also given for comparison (Table 5). 

The calibration curve method is to be preferred in serial anal3rses of samples of similar composition, but when precise results are required temperature control is necessary. When the capillary is broken or blocked, the construction of new calibration curves is necessary. 

The method of quotient of two waves can be applied in all instances, as with the calibration curve method. The temperature control is unnecessary, but more calibration curves for different concentrations of the pilot are usually necessary, and when the capillary is broken all curves must be reconstructed. 

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