Development and Validation of a Stability-Indicating RP-HPLC Method for the Simultaneous Estimation of Guaifenesin and Dextromethorphan Impurities in Pharmaceutical Formulations
Table 10
Results of robustness study.
S. no.
Impurity name
RRT’s of impurities
As such method
At 0.6 mL/min flow rate
At 1.0 mL/min flow rate
At 50°C column temperature
At 60°C column temperature
At pH 2.8 (buffer pH)
At pH 3.2 (buffer pH)
1
GN-Impurity A
0.74
0.76
0.73
0.72
0.71
0.74
0.73
2
GN-Impurity B
1.12
1.11
1.13
1.11
1.10
1.12
1.13
3
GN-Impurity C
2.04
2.06
2.05
2.05
2.02
2.04
2.05
4
GN-Impurity D
2.14
2.12
2.15
2.13
2.11
2.13
2.14
5
DN-Impurity B
0.83
0.82
0.81
0.82
0.82
0.83
0.82
6
DN-Impurity C
0.98
0.97
0.98
0.98
0.97
0.97
0.98
7
DN-N-oxide
1.01
1.02
1.03
1.02
1.03
1.02
1.04
8
DN-Impurity A
1.03
1.04
1.05
1.04
1.05
1.04
1.06
9
DN-NFM Impurity
1.28
1.31
1.30
1.31
1.29
1.28
1.19
10
DN-NFO Impurity
1.38
1.41
1.42
1.39
1.39
1.39
1.41
Note: GN known impurities RRTs were calculated against GN main peak, and DN known impurities RRTs were calculated against DN main peak.
