Linearity, calibration graphs

Following this procedure urea can be determined with a linear calibration graph from 0.143 p.g-ml To 1.43 p.g-ml and a detection limit of 0.04 p.g-ml based on 3o criterion. Results show precision, as well as a satisfactory analytical recovery. The selectivity of the kinetic method itself is improved due to the great specificity that urease has for urea. There were no significant interferences in urea determination among the various substances tested. Method was applied for the determination of urea in semm. 

Perez Ruiz et al. [26] determined penicillamine and tiopronin in pharmaceutical preparations by flow injection fluorimetry. The procedure is based on the oxidation of these drugs by thallium(III), whereupon the fluorescence of T1(T) produced in the oxidation of penicillamine is monitored using excitation at 227 nm and emission at 419 nm. A linear calibration graph for penicillamine was obtained between 3 x 10-7 and 8 x 10 5 6 M. 

Shaw et al. [64] described a (D)-penicillamine detection method in blood samples that had been treated with EDTA, deproteinized with trichloroacetic acid, and analyzed within 1 h. Penicillamine was detected at a vitreous-carbon electrode operated at +800 mV after HPLC separation. A linear calibration graph was obtained, and the method had a limit of detection equal to 5-20 ng. The method was useful in clinical and in pharmacokinetic studies. 

The absorption spectra of the ion pair shows a maximum at 632 nm. linear calibration graphs are obtained even when the aqueous phase volume is increased to 100 ml (and 7 ml of extracting solvent are used). When 50 ml of sample are used, 0.1 xg/l of phosphorus can be detected. 

KURTZ ET AL. Linear Calibration Graph and Its Confidence Bands... 

Therefore, Zp depends on the concentration of analyte atoms in the atomiser and on Zq (in fact, much of the research on AFS as an analytical technique has involved the development of stable and intense suitable light sources). Using a constant light excitation output, linear calibration graphs can be achieved for low analyte concentrations ... 

Might the method of linear calibration graph be used with these results and, if so, over which range of concentrations ... 

The system is not selective and is applicable to a wide variety of polar compounds [163, 164]. The limits of detection are often 10-100 ng per spot of compound. Linear calibration graphs are obtained for 0.1-2.0 ng of compound per spot. 

NH4+ optodes were developed using an ammonium ionophore and indicators which were made by our group, and the linear calibration graphs were produced by DCA, which converts the color information of the sensors into numerical values (QxQy and L a b values) and optimizes the color of the sensors to be suitable for human visual perception based on the Ii+ sensor described before. 

Micellar electrokinetic chromatography was used as a fast screening method for the determination of 1,4-dihydropyridines, and was used for the separation of six drugs of this group including nimodipine [38]. A fused silica tube (58.5 cm x 75 pm i.d., 50 cm to detector) was operated at 25 kV with detection at 200-236 nm. The optimized buffer (pH 8.2) contained 20 mM SDS in 50 mM borate buffer modified with acetonitrile. Linear calibration graphs extended upto 70 pg/mL from lower limits of 6.7 pg/mL. 

Fig. 3.5 Systematic errors in the standard addition method Cx analyte concentration expected when the calibration dependence is nonlinear in the extrapolation region, c i concentration found when the calibration dependence is reconstructed by a linear calibration graph, c 2 concentration found when analyte in a sample is of different chemical form to that of analyte added to the sample...

In the spectrophotometric procedure the sample is decomposed by boiling with concentrated sulphuric acid and hydrogen peroxide in a micro-Kjeldahl flask. To the solution is added sulphuric acid, ascorbic acid and potassium iodide. The absorbance is measured at 425 nm against water. A linear calibration graph was obtained for the range 4-20 /zg mP of antimony. 

Although laser ablation usually dispenses with the need for sample preparation in the analysis of rocks, the use of a major element of the sample as internal standard requires the prior knowledge of its concentration also, the addition of an internal standard element to a rock sample is difficult. Fusion of the sample with Li,B407 allows the use of Li and B as internal standards. Linear calibration graphs (constructed from standard reference geological materials) have thus been obtained for Al, Ca, Fe, K, Mg, Na, Si and Ti, and relative standard deviations of 1-2% n = 12) achieved. 

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