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Table 2 Assay parameters and validation sheet for the determination of PHL, GUA, and three GUA impurities by the proposed method

From: Exploiting the power of UPLC in separation and simultaneous determination of pholcodine, guaiacol along with three specified guaiacol impurities

Parameter

PHL

GUA impurity A

GUA

GUA impurity B

GUA impurity E

Acceptance criteria

Range

50–1000 µg mL−1

5–100 µg mL−1

NA

Slope

0.43

3.05

6.83

1.39

1.67

Intercept

− 1.22

− 1.71

5.27

− 0.67

− 2.40

Standard error of the slope

0.002

0.022

0.044

0.012

0.011

Standard error of the intercept

1.374

1.334

2.454

0.639

0.667

Correlation coefficient (r)

0.9998

0.9997

0.9997

0.9997

0.9997

≈ 1

Limit of detection

NA

1.64 µg mL‒1

NA

1.42 µg mL‒1

1.61 µg mL‒1

NA

Limit of quantification

NA

4.96 µg mL‒1

NA

4.31 µg mL‒1

4.87 µg mL‒1

Accuracy (mean % ± SD)

100.90 ± 0.95

99.76 ± 0.69

100.57 ± 0.58

99.39 ± 0.51

99.79 ± 0.84

98–102%

Repeatability (RSD %)

0.93

1.00

1.04

1.31

0.89

 ≤ 2%

Intermediate precision (RSD %)

1.08

1.11

1.11

1.40

0.95

 ≤ 2%

Specificity (mean % ± SD)

100.91 ± 0.65

99.82 ± 0.60

100.68 ± 0.88

99.52 ± 0.53

99.89 ± 0.74

98–102%

Robustness:

      

 Peak area RSD%

1.97

1.78

1.88

1.98

1.74

≤ 2%

 Retention time RSD%

0.47

0.34

0.57

0.47

0.85

 ≤ 2%