Ampicillin Trihydrate – IMPURITY M – 6-{2-[2-(2-Amino-2-phenyl-acetylamino)-2-(4-carboxy-5,5-dimethyl-thiazolidin-2-yl)-acetylamino]-2-phenyl-acetylamino}-3,3-dimethyl-7-oxo-4-thia-1-aza-bicyclo[3.2.0]heptane-2-carboxylic Acid