This is published in

Evaluation of antioxidant activity using peroxynitrite as a source of radicals.

Geletii YV, Balavoine GG

Methods in Enzymology, 31 Dec 2001, 359:366-379 DOI: 10.1016/s0076-6879(02)59199-0

ABTS is available from Sigma and can be used without additional purification.

ABTS + is synthesized easily by oxidation of ABTS with solid PbO2. Dissolve

50 mg of ABTS in 50 ml of phosphate buffer solution (75 mM, pH 7.0) and then

under agitation add 150-220 mg of PbO2 (7- to 10-fold excess over ABTS). The

solution immediately becomes blue-green. After 2-3 min of agitation, thoroughly

remove all powder from the solution using a fine filter. Reaction time may vary

depending on the surface area of PbO2. ABTS conversion to ABTS + should be

~20-30%. If it is higher, ABTS + slowly decays and in several hours its concentration

reaches the value corresponding to 20-30% conversion. ABTS + can be quantified

by measuring its absorbency at 660 nm, e = 1.2 x 104 mo1-1 liter cm -1.

Its concentration should be checked before and after use. ABTS + stock solutio

ns (-0.5 mM) are rather stable at ambient temperature. The ABTS+/ABTS mixture irreversibly precipitates at < 10 °C.

Thank you

Regardless of what previous publication recommend, you should always test it by yourself by measuring the absorbance of the ABTS+PSA solution at 734 nm and/or making a scan reading of the solutions. By doing so, you have experimental evidence that the solutions are OK or not.

Daniel Carneiro Moreira What is PSA, Prostate-specific antigen ? Why do you need to record the absorbance of the ABTS+PSA solution? Why not to check the absorbance of ABTS alone solution?

Good question mr Yurii