I want to use carboxymethyl cellulose for an EDC/NHS reaction to attach amine-functionalized small molecules. Initially, I used an EDC:NHS ratio of 1:1, but the grafting efficiency was low. Later, I referred to a paper that suggested an EDC:NHS ratio of 2:0.1, but unusual results occurred. Could you provide insights into potential by-products or reactions between EDC and CMC or the amine groups?