Table 2.

Summary of stability results in cell pellets for metformin.

	QC A 0.15 ng/mL	QC B 18.7 ng/mL	QC C 37.5 ng/mL
Autosampler (24 h at 10–15 °C)
Accuracy (%)	100	102	103
Bench-top (4 h) Accuracy (%)	101	90.4	87.5
Freeze and thaw
Accuracy (%)	92.7	99.7	96.7
Four weeks at −20 °C
Accuracy (%)	97.3	95.8	86.4

QC—quality control; n = 3.