Dear Dr Herrera

The thiocyanate method is very sensitive to oxygen
thus you must deoxygenate the lipid extract and the
reagent before the reaction. I advise you to read the
paper of Mihaljevic B et al (Free Rad Biol Med 1996,
21/1, 53-63) which examines considerations of the
mechanistic aspects of the response.
Personally, I have used the xylenol orange method
which seems more accurate and stable to obtain similar
results to those of the thiocyanate method (Deiana L
et al. Free Rad Res 1999, 31, 237-244).

Best regards
Claude Leray


--- Juan José_Rodríguez Herrera <juan@...> a
écrit : > 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)
>
>
>
>
> Lipid Links page:
> http://groups.yahoo.com/group/lipids/links
> Unsubscribing ?
> mailto:lipids-unsubscribe@...
> Questions ? Please contact Jo at
> mailto:spbcjsb@...
>
>
>
> Your use of Yahoo! Groups is subject to
> http://uk.docs.yahoo.com/info/terms.html
>
>

___________________________________________________________
Do You Yahoo!? -- Une adresse @yahoo.fr gratuite et en français !
Yahoo! Mail : http://fr.mail.yahoo.com