We have used with very succesful results following method:

HPLC- DAD: Column RP- C18, Phenomenex, Luna 150*3mm-, 5μm

Method: Phase A: H2O miliQ+ 0,1% formic acid

Phase B: ACN+ 5% H2O miliQ+ 0,1% formic acid

initial mobile phase: 10% B during 2 min

Lineal gradient to 100% B in 40 min

Mantain 100%B during 10 min

Equilibration time de 15 min

flow rate: 0,35 ml/ min

Separation of a mixture of acetaminophen,antipyrin, coffein, ciprofloxacin, diclofenac, diuron, phenol, ketorolac, and ofloxacin were perfectly achieved with LOD down to 0,02 mg/L.

Excellent!!! Did you use HLB-SPE cartridges for sample extraction?

The problem is that typical concentrations found in surface waters for such contaminants are in the tens, hundreds at most ng/L. You will need a method at least 1,000 times more sensitive than the one described above. As far as I know, you neeed an LC-MS/MS for a successful analysis of pharmaceuticals from natural surface waters.