3 to about 6 water aztreonam l lysine may also be obtained by spray drying an aqueous solution of aztreonam l lysine the aztreonam l lysine salt obtained by spraying is a white to off white powder the water content of the product obtained by this method is between about 4 to about 7 the preferred spray drying parameters are listed in the following table the parameters apply to a buchi laboratory spray drier b 191 aspirator rate 31 5 m 3 h inlet concentration outlet pump speed temperature spray flow of solution temperature ml h u00b0 c l h m m u00b0 c 240 750 115 195 400 800 7 29 45 127 the outlet temperature depends mainly on the pump speed inlet temperature spray flow and concentration of solution using optimal drying parameters the product exhibited good handling properties i e it was free flowing the particle size can also be influenced by regulating the specific drying parameters the l lysine salt of aztreonam can also be isolated by precipitating aztreonam l lysine from an aqueous solution the aqueous solution of aztreonam l lysine is preferably dropped into an aqueous or anhydrous organic solvent e g ethanol acetone etc the water content of the alcohol used for the precipitation is preferably between about 0 and 9 m m the aztreonam l lysine obtained using these methods was stable in the sense that during 3 months at 2 8 u00b0 c.