Cefoxitin Impurity 1 Sodium Salt(Cefoxitin EP Impurity A Sodium Salt);sodium (6R-cis)-3-(hydroxymethyl)-7-methoxy-8-oxo-7-(2-thienylacetamido)-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate;(6R,7S)-3-(Hydroxymethyl)-7β-methoxy-8-oxo-7-[(2-thienylacetyl)amino]-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid sodium salt