 vi. Sample preparation and assay methods The urine, plasma, and dialysate concentrations of ertapenem will be determined by a high pressure liquid chromatography HPLC or a liquid chromatography mass spectrometry LCMS device. Blood samples will be collected in standard blood collection tubes containing sodium heparin having a maximum volume of 4 mL. Samples will be stored on ice until the plasma is harvested within 2 hours. Plasma will be obtained by placing the blood samples in a centrifuge at room temperature at approximately 3000 - 4000 rpm for 15 minutes. The plasma will then be withdrawn, split into 2 aliquots of equal volume, and transferred into separate polypropylene tubes Tube 1, Tube 2.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 plasma, dose number after which the sample was collected i.e., dose 3, protocol number, subject number, date and time of sampling. 