Table 2.

Stability of Kratom Alkaloids under Different Storage Conditions (n = 5, each concentration)

		% deviation
alkaloids	nominal concentration (ng/mL)	benchtop (2 h)	autosampler (24 h)	freeze– thaw (3 cycles)	long- term (4 weeks)
MTG	2.5	4.0	−0.8	−8.0	4.0
	160	9.8	14.8	9.0	−0.3
7-HMG	2.5	6.0	1.6	6.4	−9.6
	160	13.3	6.6	9.1	−6.8
COR	2.5	3.3	6.4	−0.8	5.6
	160	11.4	14.2	9.5	−4.6
SPG	2.5	4.0	6.4	−5.6	0.8
	160	14.4	14.2	10.3	−1.4
SPC	2.5	1.3	3.2	−2.4	0.0
	160	14.7	13.6	11.5	−1.5
PAY	2.5	6.7	12.0	−2.4	2.4
	160	13.8	14.0	10.6	−2.3
COX	2.5	2.7	2.4	3.2	9.6
	160	14.6	8.1	9.2	−2.2
COX-B	2.5	4.0	2.4	1.6	0.8
	160	12.7	11.3	10.2	−1.1
AJM	2.5	2.0	1.6	−4.8	−5.6
	160	13.9	12.2	12.2	−3.2
MTP	2.5	0.7	0.8	3.2	0.0
	160	14.7	7.1	11.0	−4.6
i-SPF	2.5	0.7	12.0	12.8	1.6
	160	14.6	10.1	13.2	−4.2