Re: [Histonet] Wax removal incomplete

From:John Kiernan

O'Faolain et al did use a wax with added "polymer", 
from a Dutch supplier. The Raman spectrum of this 
sectioned wax (without tissue) had characteristic peaks 
that showed also in the spectra of supposedly
dewaxed sections of tissue. They don't discuss the
"polymer", but your suggestion could well be right.
They should have used pure paraffin as well.
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London,   Canada   N6A 5C1
"LEWIS, MARK A." wrote:
> I often wondered about this due to the "plastic "polymers added to the different types of paraffins. Perhaps it's these "polymers" that are not being removed with the typical solvents.
> Interesting ...
> Thanks John !
> Mark
> Mark A. Lewis B.A., H.T.(ASCP)
> Product Specialist
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> Thermo Electron Corporation
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> -----Original Message-----
> From: [] On Behalf Of John Kiernan
> Sent: Monday, February 14, 2005 1:40 PM
> To: Histonet
> Subject: [Histonet] Wax removal incomplete
> A recent publication from Ireland shows (by laser confocal
> Raman microspectroscopy, no less) that wax removal from
> sections, as usually practised, is always incomplete.
> The authors were able to remove all the paraffin, however,
> with hexane. The other things they tried were xylene,
> "histoclear" followed by hot antigen retrieval, and
> "trilogy" (a product that combines dewaxing and retrieval
> - ? a solvent-detergent mixture). All three failed to
> remove all the wax, even with repeated, prolonged
> treatments.
> For hexane, 18 hours were needed for complete was removal.
> The investigators found that the residual paraffin
> seriously interfered with the Raman spectra of
> rehydrated sections. They are investigating the Raman
> technique (which they explain fairly simply) for early
> diagnosis of tumours. They also claim stronger
> immunostaining after dewaxing in hexane (18h) than after
> xylene (18h). They tested only one antibody (to
> cytokeratin),
> and the pair of photos doesn't make the point very
> impressively.
> They authors also state that hexane is less toxic than
> xylene. I can add that the least expensive n-hexane is
> a little cheaper than xylenes (mixed isomers) in one
> catalogue checked.  Both solvents are flammable, and
> n-hexane (BP 69C) is more volatile than xylene. Both
> solvents are miscible with 100% alcohol.
> The reference is:
> O'Faolain E et 6 al. (2005) Raman spectroscopic evaluation
> of efficacy of current paraffin wax section dewaxing
> agents. J. Histochem. Cytochem. 53(1): 121-129.
> --
> -------------------------------
> John A. Kiernan
> Department of Anatomy and Cell Biology
> The University of Western Ontario
> London,   Canada   N6A 5C1
>    kiernan[AT]
> _______________________________

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