Table 2. Stability of TQD in plasma over time at different concentrations and different storage temperatures.

Concentration	Storage	24 h	1 month	3 months
0.1 μg/ml	RT	0.10±0.004 (100)	0.008±0.000 (8.6)	0.003±0.000 (3.0)
	4°C	0.099±0.003 (99)	0.007±0.001 (7.2)	0.003±0.000 (3.1)
	−20°C	0.10±0.002 (100)	0.073±0.005 (73.9)	0.041±0.004 (40.8)
	−80°C	0.098±0.003 (98)	0.078±0.006 (78.1)	0.069±0.005 (69.1)
0.5 μg/ml	RT	0.49±0.033 (98)	0.037±0.002 (9.8)	0.008±0.001 (1.7)
	4°C	0.51±0.023 (102)	0.056±0.003 (11.2)	0.017±0.001 (3.4)
	−20°C	0.49±0.014 (99)	0.38±0.021 (77.6)	0.18±0.014 (36.4)
	−80°C	0.50±0.025 (100)	0.41±0.030 (82.3)	0.27±0.023 (53.9)
2.0 μg/ml	RT	2.02±0.081 (101)	0.18±0.003 (9.1)	0.054±0.004 (2.8)
	4°C	1.97±0.050 (98.5)	0.19±0.004 (9.5)	0.11±0.006 (5.6)
	−20°C	1.98±0.075 (99)	1.51±0.065 (75.8)	0.97±0.084 (48.3)
	−80°C	2.01 ±0.064 (100.5)	1.62±0.068 (80.6)	1.23±0.056 (61.5)

Data are expressed as mean (±SD) concentration (μg/ml) of four separate determinations. Values in parentheses represent percent of baseline values. RT: room temperature.