substance it is generally desirable to lyse red blood cells to release hemoglobins common cationic e g cetyl tri methyl ammonium bromide anionic e g sodium dodecylsulfate and sodium deoxycholate and neutral e g saponin and octyl phenoxypolyethoxyethanol detergents are useful in lysing red blood cells neutral detergents in the concentration range of about 0 025 to 0 5 volume percent are preferred mechanical rupture for example ultrasonication and hypotonic lysis are also effective ways of releasing hemoglobin from red blood cells binding of heme binding ligands to heme iron generally shifts the equilibrium of allosteric hemoglobin isomers to the relaxed r form thus when the heme binding moiety of the hemoglobins in the test sample is coordinated with a heme binding ligand larger shifts in the equilibrium populations of allosteric forms of hemoglobin are observed this magnification in shift in equilibrium enhances accuracy and precision of glycosylated hemoglobin determination this coordination of heme binding ligand to shift equilibrium of allosteric isomers is applicable when the iron is in the fe 2 or the fe 3 methemoglobin states those skilled in the hemoglobin arts will recognize a wide variety of heme binding ligands which bind to the iron of hemoglobin or methemoglobin for example isocyanides such as alkyl isocyanides having 1 6 carbon atoms or phenyl isocyanides are particularly desirable heme binding ligands for hemoglobin in the fe 2 state other suitable ligands are o 2 and no it is generally preferred to have a single ligand bound to iron since this results in simpler measurements of the shift in allosteric forms for example oxyhemoglobin glycosylated and non glycosylated is preferably.