00 g water content 12 2 was suspended in 25 ml distilled water at 0 5 u00b0 c a solution of 2 70 g l lysine in 13 5 ml distilled water was added dropwise to the above suspension with cooling ice water bath the solution of aztreonam l lysine salt obtained by this method was filtered on a glass filter and freeze dryed aztreonam 35 0 g water content 12 6 was suspended in 230 ml distilled water at 0 5 u00b0 c a solution of 17 5 g l lysine in 45 ml distilled water was added dropwise to the above suspension with cooling ice water bath the solution of aztreonam l lysine salt obtained by this method was decolorized with charcoal filtered on a glass filter and spray dryed using laboratory spray dryer b u00fcchi b 191 the aztreonam l lysine salt produced according to this example does not contain any impurity exceeding 0 3 area and or maintains at least about 63 weight of the aztreonam after storage for three months at about 2 8 u00b0 c aztreonam 3 50 g water content 11 3 was suspended in 8 ml distilled water at 0 5 u00b0 c a solution of 1 80 g l lysine in 3 5 ml distilled water was added dropwise to the above suspension with cooling ice water bath the solution of aztreonam l lysine salt obtained by this method was diluted with 23 ml ethanol and added dropwise to the stirred mixture of 60 ml ethanol and 4 75 ml water at 0 5 u00b0 c.