 Similarly the dialysate and urine samples will be split into two batches and stored at -20oC until assayed. The dialysate will be mixed thoroughly. The total sample volume will be recorded. Two milliliters of dialysate will be transferred into each of the polypropylene tubes Tube 1 and Tube 2. The tubes are pre-labeled as either Set A Tube 1 or Set B Tube 2. The labels will be in indelible ink. The following information will be included on the labels: sample type dialysate, dose number after which the sample was collected i.e., dose 3, protocol number, subject number, date and time of sampling. Samples will be stored frozen at -20 degrees Centigrade until they are shipped for concentration determination. Blank dialysate without ertapenem in it will also be sent for assay to assess for potential interfering substances in the assay and to serve as analytical controls for the assay. The blank dialysate samples will be 10-20 mL stored in individual polypropylene tubes, clearly marked, dialysis blank. On a separate piece of paper, the specific concentration of each component of the dialysate fluid i.e., electrolytes, dextrose, saline, etc. will be included in the shipment. 