Research Article

Use of Alizarin Red S as an Ion-Pair Reagent for the Spectrophotometric Assay of Fexofenadine in Pharmaceuticals and in Spiked Human Urine

Table 3

Regression and Analytical Parameters.

ParameterMethod AMethod B

, nm440590
Beer’s law limits (μg mL−1) 0.4–12.00.2–3.5
Molar absorptivity (l mol−1 cm−1)3.8 × 1041.6 × 105
Sandell sensitivity* (μg cm−2)0.01420.0033
Limit of detection (μg mL−1)0.230.04
Limit of quantification (μg mL−1)0.680.12
Regression equation,
 Intercept, (a)0.00520.0236
 Slope, (b)0.07260.2714
 Correlation coefficient (r)0.99950.9995
 Standard deviation of intercept ( )0.10950.0358
 Standard deviation of slope ( )0.01510.0184

*Limit of determination as the weight in μg per mL of solution, which corresponds to an absorbance of A = 0.001 measured in a cuvette of cross-sectional area 1 cm2 and l = 1 cm. , where Y is the absorbance, a is the intercept, b is the slope and X is the concentration in μg mL−1.