Redox-Reaction Based Spectrophotometric Assay of Isoniazid in Pharmaceuticals

Table 1

Sensitivity and regression parameters.

Parameter	Method A	Method B
𝜆max, nm	760	760
Color stability, min	60	90
Linear range, 𝜇g mL^−1	0.5–10.0	0.2–3.0
Molar absorptivity (𝜀), L mol^−1 cm^−1	1.12 × 10^4	4.55 × 10^4
Sandell sensitivity*, 𝜇g cm^−2	0.0123	0.003
Limit of detection (LOD), 𝜇g mL^−1	0.03	0.14
Limit of quantification (LOQ), 𝜇g mL^−1	0.09	0.42
Regression equation, 𝑌^∗∗
Intercept (𝑎)	0.0131	0.0198
Slope (𝑏)	0.0905	0.3176
Standard deviation of 𝑎 (𝑆𝑎)	9.98 × 10^−2	9.98 × 10^−2
Standard deviation of 𝑏 (𝑆𝑏)	1.24 × 10^−2	3.98 × 10^−2
Regression coefficient (𝑟)	0.9971	0.9979

∗Limit of determination as the weight in 𝜇g mL⁻¹ 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.
^∗∗𝑌=𝑎+𝑏𝑋, where 𝑌 is the absorbance, 𝑋 is concentration in µg mL⁻¹, 𝑎 is intercept, and 𝑏 is slope.