Direct Determination of Iron in Malt Beverages

The Early Years of 2,2′-Bipyridine—A Ligand in Its Own Lifetime

“…McFarlane noted the similarity of the absorption spectra of aqueous cobalt(II) nitrate solutions and [Fe(bpy) 3 ] 2+ and proposed the former as a colorimetric standard for calibration [279]. This colorimetric method rapidly became the method of choice for the analysis of iron in a wide range of materials and the technique was applied, inter alia, to the determination of the iron content of hematin and cytochrome c [286], water [287,288,289,290], milk [291], beer [292,293], other foodstuffs [294,295,296,297,298,299,300,301], soil and minerals [302,303,304,305,306], teeth [307,308], blood [285,309,310,311,312,313,314] and other biological materials [315,316,317,318,319] and homeopathic formulations [320]. It was recognized that the methods using bpy for the determination of iron gave a measure of the "available" iron, and any Fe that was strongly bound in heme proteins or ferritin would not necessarily be included in the total iron [321,322].…”

Semi-quantitative analysis for selecting Fe- and Zn-dense genotypes of staple food crops

“…The extraction would not recover Fe and Zn in organic materials, as full extraction requires a wet digestion method, however, it is a simple, inexpensive and safe analysis. Methods available to determine iron by colorimetry include the use of 1,10-phenanthroline (orthophenanthroline) (Bandemer and Schaible, 1944;Pepi, 1946;Loeppert and Inskeep, 1996), ferrozine (Stookey, 1970;King et al, 1991), 2,2 0 -dipyridyl (Gray and Stone, 1938), and thiocyanate (Schlesinger and Valkenburgh, 1931). Of these, 2,2 0 -dipyridyl is of particular interest for Fe analysis because it minimizes phosphate interference and the colour remains stable for several hours (Snell and Snell, 1959, and references therein).…”

Progress in Brewing Science and Technology

“…This is especially true for the method involving colorimetric determination of iron directly in the beer without prior ashing, through use of a, a'-dipyridyl (61). Most commonly these metals are copper and iron, whose presence in more than normal traces is ascribable to pickup from brewing equipment surfaces Simplified rapid methods for determination of traces of these metals, giving results reproducible in the order of less than 0.1 p,p.m., have replaced the more lengthy and involved procedures available in 1935 and have done much to make feasible the detection and the limitation of metal entry.…”

“…Simplified rapid methods for determination of traces of these metals, giving results reproducible in the order of less than 0.1 p.p.m., have replaced the more lengthy and involved procedures available in 1935 and have done much to make feasible the detection and the limitation of metal entry. This is especially true for the method involving colorimetric determination of iron directly in the beer without prior ashing, through use of a, '-dipyridyl (61). Copper is determined colorimetricallj7 after ashing by reaction with sodium diethyldithiocarbamate and extraction of the colored complex with amyl acetate, after eliminating iron by complexing with a, a'-dipyridyl (173).…”