surfactant surfactant (%) α-Lipoic acid (%) metal (M) M2+/α-Lipoic acid CO32-/M2+ appearance
blank 0 1 Mg 0.5 - s
0 1 Mg 0.25 - s
0 1 Ca 0.5 - s
0 1 Ca 0.25 - s
Polyoxyethylene (20) stearyl eter 1 1 Mg 0.5 0.2 t
2 1 Mg 0.5 0.2 t
5 1 Mg 0.5 0.2 t
5 1 Ca 0.5 0.2 s
8 1 Ca 0.5 0.2 s
8 1 Mg 0.5 0.2 t
10 1 Ca 0.5 0.2 s
10 1 Ca 0.25 0.2 t
10 0.5 Ca 0.5 0.2 s
10 0.5 Ca 0.25 0.2 t
Polyoxyethylene (60) hydrogenated castor oil 10 1 Ca 0.5 0.2 s
10 1 Ca 0.25 0.2 t
10 0.5 Ca 0.5 0.2 s
10 0.5 Ca 0.25 0.2 t
sucrose laurate 5 1 Mg 0.5 0.2 t
10 0.5 Ca 0.5 0.2 s
10 0.5 Ca 0.25 0.2 t
t=transparent; s=separate
Table 2: Influence of nonionic surfactants, divalent cations (Ca2+, Mg2+) and a divalent anion (CO32-) on appearance of the solution containing α-lipoic acid.