Table 3 Assay parameters and validation results obtained by applying the zero crossing derivative, ratio difference and ratio derivative spectrophotometric methods

Wavelength (nm)

255.5

346

277.5–242.5

315–310.5

286

321.5

Linearity range (µg/mL) (n = 3)

2.5–35

3–22

4–20

3–25

4–25

3–25

Intercept

0.0006

 − 0.0004

0.0272

 − 3.0589

0.0068

 − 5.5719

Slope

0.0011

0.0028

0.1397

6.7181

0.0156

9.7111

Correlation coefficient (r)

0.9993

0.9990

0.9994

0.9997

0.9990

0.9995

Accuracy (Mean ± SD)

99.32 ± 0.92

99.84 ± 1.16

100.65 ± 0.68

99.63 ± 1.26

99.27 ± 1.23

99.48 ± 0.82

Precision (± %RSD)

Repeatability

99.77 ± 0.79

100.39 ± 1.29

100.19 ± 0.87

100.66 ± 0.62

100.39 ± 1.11

100.05 ± 1.12

Intermediate precision

99.86 ± 0.77

99.04 ± 1.00

100.13 ± 0.82

99.3 ± 1.34

100.80 ± 0.64

99.93 ± 1.45

Specificity (Mean ± SD)

100.33 ± 0.95

100.94 ± 0.81

100.88 ± 0.62

100.54 ± 0.74

99.50 ± 1.20

100.82 ± 0.90