DP1   DP2   Vancomycin   DP3 / epimer   Ticarcillin / epimer   DP4 / epimer
  RT (min)   9.6   10.4   11.6   15.8 / 16.3   17.8 / 18.4   19.2 / 19.7
  Resolution
factors		   2.5   1.67   4.65   1.81   1.53  
  (M+nH)n+
m/z		   725.3
(z=2)		   725.3
(z=2)		   724.7
(z=2)		   403.0 / 403.0   385.0 / 385.0   431.0 / 431.0
  Accurate masses (relative errors ppm)   725.2190
(-2.04)		   725.2190
(-2.04)		   724.7208
(-2.17)		   403.0620
(-2.03)		   385.0516
(-1.69)		   431.0569
(-1.92)
  Elemental composition   C66H76Cl2N8O252+   C66H76Cl2N9O252+   C66H77Cl2N9O242+   C15H19N2O7S2+   C15H17N2O6S2+   C16H19N2O8S2+
Table 1: Retention times (RT), resolution factors (Rs) and MS data from ion chromatogram of drugs pH 5.2 antibiotics mixture solution after a 2-month storage period at 5°C. Accurate masses were measured by flow injection analysis and best possible elemental formula are proposed.