Good evening,

I need to prepare a staining solution for lipid bodies in roots following the protocol given by Brundrett et al. (1991). Here is what the article says: "(1) A sufficient amount of dye [in this case Sudan Red 7B] to make a 0.1 % w/v final solution was dissolved in polyethylene glycol (average mw 400 Daltons) by heating at 90 °C for 1 hr. (2) An equal volume of 90% (v/v) glycerol (containing 10% distilled water) was added to the polyethylene glycol plus stain."

When I looked up on the Sigma-Aldrich website for PEG to buy it, I found different PEG 400, but I guess the right one to use in this case is this one:

https://www.sigmaaldrich.com/catalog/product/aldrich/202398?lang=fr®ion=BE&cm_sp=Insite-_-caSrpResults_srpRecs_srpModel_polyethylene%20glycol%20400-_-srpRecs3-3

The point is, does PEG have to be used pure or does it have to be diluted? Was a dilution given by granted by the author because it's what is normally done, or should I use the viscous liquid as I find it in the recipient? Thank you!

Reference: Mark C. Brundrett, Bryce Kendrick & Carol A. Peterson (1991) Efficient Lipid Staining in Plant Material with Sudan Red 7B or Fluoral Yellow 088 in Polyethylene Glycol-Glycerol, Biotechnic & Histochemistry, 66:3, 111-116, DOI: 10.3109/10520299109110562