Table 5: Stability (%) of quality control samples after extraction.

Analyte	Nominal Concentration (ng/ml)	Autosampler stability (%)		−80°C (%)		Freeze thaw (%)
PGP		24h	48h	7 days	30 days	3X	6X
	0.01	116.75 ± 25.35	123.77 ± 31.44	88.52 ± 14.10	100.91 ± 24.44	112.13 ± 34.45	111.98 ± 31.37
	0.07	112.01 ± 21.79	117.91 ± 18.50	92.63 ± 10.81	106.90 ± 4.90	99.32 ± 13.19	83.78 ± 18.61
	0.25	106.95 ± 16.52	104.28 ± 12.74	94.37 ± 7.93	96.78 ± 6.80	89.64 ± 7.49	90.11 ± 9.84
	2.5	114.04 ± 10.84	113.20 ± 16.89	104.44 ± 8.13	95.11 ± 6.50	92.29 ± 8.43	91.24 ± 5.07
	25	109.34 ± 10.20	113.31 ± 14.88	100.53 ± 7.85	94.15 ± 5.04	94.97 ± 8.98	91.75 ± 7.77
	50	102.51 ± 12.98	101.75 ± 13.03	91.93 ± 8.52	91.24 ± 8.62	90.12 ± 8.75	90.96 ± 5.42
AcPGP	0.01	103.40 30.95	106.97 ± 21.40	103.02 ± 15.16	133.01 ± 32.37	130.35 ± 55.52	112.23 ± 33.31
	0.07	89.90 ± 8.70	97.18 ± 7.52	106.99 ± 15.16	111.56 ± 7.65	110.77 ± 12.97	94.57 ± 24.05
	0.25	95.87 ± 6.79	99.41 ± 2.06	112.33 ± 10.97	98.10 ± 4.04	102.37 ± 18.05	93.23 ± 12.51
	2.5	94.93 ± 4.59	103.37 ± 3.90	114.21 ± 11.35	98.36 ± 5.81	92.60 ± 3.42	96.80 ± 2.79
	25	97.17 ± 2.49	103.87 ± 2.86	111.92 ± 3.34	93.01 ± 3.87	90.55 ± 4.33	92.05 ± 3.88
	50	94.86 ± 2.47	104.33 ± 5.19	113.78 ± 2.87	93.87 ± 2.42	93.62 ± 2.49	94.95 ± 2.73