Hi

I have received a revercedphase method for basic compounds.The analyst who developed the method uses a 50mM phosphatebuffer in the mobilephase but a five times weaker for the samples and for standards. Are were any known effect of this??

Other things being equal, it is a good idea to match the samples and standards to the mobile phase as closely as possible (the less you upset the equilibration of the system, the better). If you can't match, it is generally better to have the samples and standards dissolved in a weaker eluant than the mobile phase. Assuming the method has been properly validated, I wouldn't worry about it in this case unless you're seeing evidence of problems (variable retention, peak shape, etc.)