under controlled conditions the conditions are designed to minimize undesirable polymerization which would reduce yields using sds or a detergent of formula i wherein n is 8 through 20 inclusive r 1 is methyl or ethyl and r 2 is hydrogen ethyl methyl or n propyl solubilization and oxidation of somatotropins can be achieved at relatively high concentrations the ratio of somatotropin to detergent is dependent on the detergent 39 s acid moiety the weaker the acid moiety of the detergent the greater quantity of detergent required for solubilization for example using sodium dodecyl sulfate which has a relatively strong acid moiety a ration of 1 1 is sufficient however using detergents of formula i ratios of 2 5 are preferred use of a buffer to dilute the detergent is optional once the somatotropin is solubilized the oxidation is optionally promoted by introducing air through the mixture air is introduced by either agitation or passing air directly through the solution the rate and method of introduction of air is dependent on the quantity of the preparation it is necessary to allow oxidation to go to completion to avoid downstream polymerization reagent during concentration oxidation can be monitored by use of ellman 39 s reagent methods of enzymology 25 457 464 1972 the preferred.