Table 5 Summary of colistin stability study in rat plasma samples by LC-MS/MS method.

From: Quantification of Colistin in Plasma by Liquid Chromatography-Tandem Mass Spectrometry: Application to a Pharmacokinetic Study

Freeze-thaw (−70 °C to 25 °C after 24 hours)

Colistin A

Nominal Concentration (ng/ml)

234

546

1170

2730

Found (Mean ± S.D)(ng/ml) (n = 4)

265.4 ± 35.10

615.27 ± 30.29

1208.93 ± 77.51

2551.83 ± 177.97

R.S.D%

13.23

4.91

6.41

6.97

Bias%*

13.42

12.69

3.33

−6.53

Colistin B

Nominal Concentration (ng/ml)

1059

2471

5295

12355

Found (Mean ± S.D)(ng/ml)(n = 4)

1188.48 ± 129.25

2715.48 ± 154.87

5136.5 ± 231.26

11293.18 ± 556.44

R.S.D%

10.88

5.70

4.50

4.93

Bias%*

12.23

9.89

−2.99

−8.60

Long-term stability at −70 °C (20 days)

Colistin A

Nominal Concentration (ng/ml)

234

546

1170

2730

Found (Mean ± S.D)(ng/ml) (n = 5)

237.24 ± 5.64

520.76 ± 19.46

1134.44 ± 26.11

2719 ± 50.20

R.S.D%

2.38

3.74

2.30

1.85

Bias%*

1.39

−4.62

−3.04

−0.40

Colistin B

Nominal Concentration (ng/ml)

1059

2471

5295

12355

Found (Mean ± S.D)(ng/ml)(n = 5)

1073 ± 60.43

2457.56 ± 75.91

5280.04 ± 83.05

12524 ± 346.18

R.S.D%

5.63

3.19

1.57

2.76

Bias%*

1.32

−0.54

−0.28

1.37

Benchtop Stability Study (25 °C for 6 hours)

Colistin A

Nominal concentration (ng/ml)

234

546

1170

2730

Found (Mean ± S.D)(ng/ml) (n = 4)

120.275 ± 50.32

592.47 ± 488.56

1047.6 ± 202.94

5045 ± 3076.10

R.S.D%

41.84

82.46

19.37

60.97

Bias%*

−48.6

8.51

−10.46

84.8

Colistin B

Nominal concentration (ng/ml)

1059

2471

5295

12355

Found (Mean ± S.D)(ng/ml)(n = 4)

518.72 ± 367.93

929 ± 1012.78

1684.55 ± 2793.21

7736.23 ± 4775.30

R.S.D%

70.93

109.02

165.81

61.73

Bias%*

−51.02

−62.40

−68.19

−37.38

Autosampler stability study (4 °C for 24 hours)

Colistin A

Nominal concentration (ng/ml)

234

546

1170

2730

Found

(Mean ± S.D)(ng/ml) (n = 4)

231.18 ± 6.22

516.95 ± 53.28

1034.9 ± 38.64

2917.93 ± 341.07

R.S.D%

2.69

10.31

3.73

11.69

Bias%*

−1.21

−5.32

−11.55

6.88

Colistin B

Nominal concentration (ng/ml)

1059

2471

5295

12355

Found (Mean ± S.D)(ng/ml)(n = 4)

1060.60 ± 108.61

2460.85 ± 115.75

4749.75 ± 386.29

12863.28 ± 1546.10

R.S.D%

10.24

4.7

8.13

12.02

Bias%*

0.15

−0.41

−10.30

4.11

  1. SD: standard deviation.
  2. RSD: relative standard deviation.
  3. RSD (%) = (SD/Mean) *100.
  4. Bias (%) = (mean of measured conc - nominal conc/nominal conc) *100.
Back to article page