Interface Enrichment of Methylene Blue by Fatty Acids with Microanalytic Applications

The colorimetric micro-determination of long-chain fatty acids

“…The methods of Barreto & Mano (1961) and of Iwayama (1959) require about lj5 mg. and 25-6 mg. respectively to produce the same extinction. Coleman & Middlebrook (1957) have developed a method of equal sensitivity based on the enrichment of methylene blue at a waterheptane interface, but since the system is not in equilibrium when colour readings are made it is necessary to run standards concurrently. Further, there was little effect with linolenic acid and with myristic acid and shorter-chain saturated acids, and uniform standardization of the procedure and the maintenance of a constant ambient temperature were very critical factors.…”