Dear all:

Regarding the thiocyanate method to quantify hydroperoxides, different
authors use different times to take readings. It seems clear that in some
cases the reaction has not finisheh yet, whereas a few of them indicate
that the measurement is taken once the asymptote of the reaction is
reached.
The latter does not seems to be possible in the case of fish lipids, with a
high content of PUFA. We are using the method of Ueda (1986) with a number
of changes, but we have found that deoxigenation of reactants followed by
a great care to prevent the presence of oxygen and the lack of light are
not enough for the reaction reached the plateau. That is, it seems that
hydroperoxides are countinuously formed during the course of the reaction.
Does anyone know how this can be sorted out in the case of lipids with a
high content in PUFA? Or which criterion can be used to establish the time
at which the absorbance should be read out? At present we are using what
seems a change in the order of the reaction.

Thanks in advance and also for previous replies that I have received:

Juan

Juan José Rodríguez Herrera
Dpto. Química y Tecnología de Productos Pesqueros
(Dpt. of Chemistry and Technology of Fish Products)
Instituto de Investigaciones Marinas
(Institute of Marine Research)
Consejo Superior de Investigaciones Científicas (C.S.I.C)
36208 VIGO
ESPAÑA (SPAIN)