HPLC for quantifying -Epicatechin

[kez40]

I am trying to make a calibration curve using a standard -Epicatechin, however I am continually getting 5 peaks instead of 1. This standard has been used before with success (my mobile phase is water, methanol and h3po4(0.1%)), my stationary is a C18 column, flow rate is 1ml/min and the UV is set at 210nm. What am I doing wrong?

[skunked_once]

In such a case the first things to consider are:

1-Have you run a blank to be sure that your system and mobile phase are clean?

2-How old is the standard? Could it have decomposed? Could it have been contaminated? Can a new standard be prepared?

Good luck!