Sorry CharonY, I was so desperate last night that I didnt explain my position in full. You see, Ive been digging a couple of hours on pubmed, highwire, hinari and I actually SAW ALLTHOSE BEAUTIFULL ARTICLES WITH direct approach to the more than helpful protocols. But .... there is one little problem. None of them is full text free of payment.And being a molecular biologist in a country that doesnt have money for science nor scientists it really means a lot.Yeah, I know theres dozens...sigh. If I had been able to take up any of them or better even, several of them,full text online without paying 15, 20 or even 35 dollars per article, I wouldnt trouble people on the forum. Truth be said I stumbled over two or three recipees and I downloaded them.See what I can do. But I had a workbook with the slightly modified Beutler method for measuring catalase activity spectrophotometrically on 230 nm wavelength based on the degradation of hydrogene peroxide and it was such an elegantly simple method. The problem is my workbook has vanished from my room so as you see Im on the beginning. And the main stumblesotne is that I cant remember the buffer used in that protocol. Was it potassium phosphate or Tris chloride and what was the molarity and PH... Ill try and see the optimum Ph for rat catalase activity and then Ill know which buffer to use according to the optimal Pk for each of these solutions. Anyway thank you and I hope we will hear again!!