The determination of iron in blood plasma or serum.

Some time ago it became necessary in this department to have a rapid and reliable method for the determination of iron in blood serum or plasma. The method was required for teaching purposes on human subjects and for investigations on iron metabolism in various species. Since none of the published techniques seemed quite suitable, a new one was based on the experience of the author (Ramsay, 1951,1952) in determining non-haem iron in the chick embryo and its liver. The new method is described here, with illustrative examples of its use and comparisons with the results of others. The separation of iron from the proteins of blood plasma has long been known to be a matter of difficulty. Barkan (1927) observed the serum iron to be neither dialysable nor ultrafiltrable, but claimed that it could be made so by incubation of the serum with dilute hydrochloric acid. Fowweather (1934) demonstrated the retention of a substantial proportion of the plasma iron by a trichloroacetic acid protein precipitate, and determined iron in the serum after wet ashing with sulphuric acid and hydrogen peroxide. This procedure is tedious, involves the use of relatively large quantities of reagents liable to be contaminated with iron, and may under certain conditions lead to loss of iron. A similar technique was employed by Moore, Arrowsmith, Quilligan & Read (1937). Tompsett (1934) believed that Fes', but not Fe2+, is adsorbed to the precipitated protein, and added