Table 4 Robustness assessment of the investigated methods for determination of IBU, PAP, PAR, PNP, CHZ and PCA

Saturation time

60 ± 5 min

Acetonitrile (%)

30 ± 2%

 Rs^b

–

1.6

1.4

1.1

1.5

1.4

    Rs^b

–

1.5

1.5

1.0

1.2

0.9

 R_F

1.6

1.5

1.2

1.8

1.6

1.5

    tR

1.6

1.2

1.6

1.9

1.2

1.4

 K’

1.2

1.9

1.9

1.8

1.4

1.6

    K’

1.4

1.6

1.2

1.7

1.4

1.9

 T

1.2

0.9

1.2

0.9

1.4

1.1

    T

1.9

1.6

1.4

1.6

1.5

1.5

 R%

1.9

1.7

1.8

1.5

1.8

1.7

    R%

1.2

1.3

1.2

1.5

1.2

1.5

Ammonia content

0.2 ± 0.05 mL

Phosphate buffer pH

7.5 ± 0.5

 Rs^b

–

1.7

1.6

1.3

1.5

1.8

    Rs^b

–

1.8

1.0

1.2

1.2

0.9

 R_F

1.7

1.5

1.2

1.8

0.9

1.7

    tR

1.6

1.5

1.7

1.2

1.7

1.5

 K’

1.6

1.6

1.9

1.7

1.5

1.9

    K’

1.5

1.6

1.2

1.7

1.7

1.9

 T

1.2

1.4

1.0

1.1

1.1

0.9

    T

1.7

1.5

1.9

1.8

1.5

1.9

 R%

1.6

1.6

1.4

1.9

1.5

1.7

    R%

1.5

1.8

1.6

1.4

1.5

1.4

Detector wavelength

220.0 ± 5.0 nm

Flow rate

0.7 ± 0.2 mL/min

 Rs^b

–

1.8

1.8

1.7

1.8

1.7

    Rs^b

–

1.7

1.4

1.4

1.2

1.3

 R_F

1.7

1.5

1.2

1.9

1.6

1.5

    tR

1.3

1.5

1.7

1.3

1.3

1.5

 K’

1.4

1.4

1.4

1.7

1.7

1.5

    K’

1.2

1.6

1.2

1.0

1.4

1.2

 T

1.1

1.4

1.2

1.5

1.1

0.9

    T

1.9

1.6

1.4

1.6

1.5

1.7

 R%

1.6

1.7

1.6

1.6

1.5

1.8

    R%

1.4

1.4

1.8

1.7

1.3

1.8