Table 2.

The stability results of carvedilol and 4/-hydroxyphenyl carvedilol, n = 3.

Storage conditions	Analytes	QC Level	Mean concentration of freshly prepared samples (ng/mL)	Mean concentration of stability samples (ng/mL)	Deviation (%)
Freeze-thaw stability (3 cycles, -70 °C)	Carvedilol	LQC	0.148	0.147	-1.124
		HQC	37.498	42.722	13.931
	4/-Hydroxy phenyl	LQC	0.134	0.137	1.990
		HQC	7.076	6.849	-3.213
Short-term stability (8 h, room temperature)	Carvedilol	LQC	0.157	0.164	4.246
		HQC	45.022	42.671	-5.220
	4/-Hydroxy phenyl	LQC	0.150	0.157	5.122
		HQC	7.127	6.913	-3.003
Long-term stability (148 day, -70 °C)	Carvedilol	LQC	0.145	0.158	8.716
		HQC	39.135	39.854	1.836
	4/-Hydroxy phenyl	LQC	0.134	0.148	10.448
		HQC	7.076	7.538	6.519
Post-preparative stability in auto-sampler (24 h, 4 °C)	Carvedilol	LQC	0.150	0.160	6.652
		HQC	41.382	40.192	-2.876
	4/-hydroxy phenyl	LQC	0.151	0.149	-1.545
		HQC	8.869	8.290	-6.528
Stability in whole blood (30 min, room temperature)	carvedilol	LQC	0.140	0.155	10.556
		HQC	45.910	45.723	-0.408
	4/-hydroxy phenyl	LQC	0.156	0.160	2.308
		HQC	7.533	7.098	-5.770

QC, Quality control; LLOQ, lower limit of quantification; LQC, low quality control; MQC, medium quality control; HQC, high quality control.