Hi Graeme… here goes the answer to your query…
From: Donato Romanazzi
Sent: 07 June 2016 15:25
To: Cristina Armstrong <Cristina.Armstrong@cawthron.org.nz>
Subject: RE: seaweed extracts
Really….as I’ve never extracted alginates. However, our friend/colleague Raimond Kaas from Ifremer in Nantes does it, and that’s how:
Cut the entire frond into small pieces (5cm2), rinse them with distilled water and then immerse in 0.5M H2SO4 solution for at least one night (stored at 4oC).
Rinse the algae again with distilled water to eliminate acid excess. For the extraction, soak 200g of acidified algae in 1L of 4% Na2CO3 solution with continuous stirring. Algae residue are separated from sodium alginate solution by centrifugation (10000g for 10min).
Add sulphuric acid to the sodium alginate solution to pH 2 so as to form alginic acid, which precipitates forming foam. The product is then pressed through a filter cloth, heat-dryed and milled by pestle and mortar and stored at 4oC.
Hopefully it works!