Thanks for that link. As you will know R-ALA is the purer, natural version which is said to have better absorption properties.
Virtually all the cheaper ALA you buy is a 50/50 mix of R-ALA (the better one) and S-ALA ( the not so good one). So if you buy, say, 600mg capsules then you are getting 300mg of R-ALA and 300mg of S-ALA. It is cheaper to buy this way than buying pure R-ALA which is only available in lower doses and is a lot more expensive. I have checked with several manufacturers and the purity of the R-ALA they use in the mixed variety is the same as they use in the R-ALA only variety