Table 3 Stability and adsorption characteristics of NATOG. Concentrations were obtained after spiking. Samples were analyzed in duplicate. Accuracy of 80–120 % on the theoretical spiked concentration was considered acceptable

Stability^a

Ref.

24 h 4 °C

24 h RT

24 h 50 °C

Urine pH 4

11.0 ± 0.3

10.7 ± 0.0

11.0 ± 0.4

10.9 ± 0.0

Urine pH 6

10.9 ± 0.3

11.2 ± 0.1

11.4 ± 0.0

11.7 ± 0.1

Urine pH 8

11.6 ± 0.3

11.6 ± 0.1

11.6 ± 0.2

11.8 ± 0.1

Sun stability^b

Ref.

0.5 h Suntest

3 h Suntest

Clear vials

2.65 ± 0.01

2.61 ± 0.03

2.57 ± 0.01

Amber vials

2.64 ± 0.01

2.65 ± 0.01

2.61 ± 0.03

Adsorption test^a

Ref. glass

6 cycles glass

Ref. PP

6 cycles PP

Urine pH 4

10.5 ± 0.3

11.0 ± 0.1

10.7 ± 0.1

10.8 ± 0.1

Urine pH 6

11.2 ± 0.1

11.1 ± 0.1

10.7 ± 0.8

11.1 ± 0.1

Urine pH 8

11.3 ± 0.1

11.4 ± 0.1

11.5 ± 0.1

11.3 ± 0.0