On page 193 of his book Origins: A Skeptics Guide to the Creation of Life on Earth, Robert Shapiro states:
"Amino acids do not readily unite to form peptides (short protein chains) and proteins when water is present. The details of the energy budget in fact dictate that the opposite should take place. In the presence of water, peptides and proteins slowly break down into amino acids. The situation suggest its own remedy. To unite amino acids, heat them together in a dry state, so that the water released by their union is expelled.
This remedy, when tried, had been found wanting, however. "Biochemists knew that when a mixture of amino acids in the ratio found in proteins was heated, the result was pryolysis to a dark brown tar with a disagreeable odor," commented chemist William Day."
This alone blows away the idea of any primordial soup. Besides that, the nitrogen content of "PreCambrian organic matter" is less than 0.15% and amino acids contain significant quantities of nitrogen.
("Origins of Life by Jim Brooks Lion: Tring, Hertfordshire UK, p. 118)
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