Determination of residues of 4 fluoroquinolone antibiotics in wastewaters from 4 hospitals and from influent and effluent wastewater treatment plant in Coimbra in Portugal and evaluation of eficiency of treament process [14th National meeting of the Spanish Society for Analytical Chemistry / 9th International symposium on analytical methodology in the environmental field; OCT 01-05 2007; La Coruna, Spain]