I am trying to quantify Dicyandiamide in a fertilizer, but am having trouble with getting everything to elute from the column in a reasonable amount of time. I am using a reverse phase C-18 column (2.7 micron, 4.6x150mm) and ACN/water as solvent. I've tried all kinds of ACN/water ratios and also 100 ACN, but can't seem to get everything to leave the column quick enough. The DCD elutes right away (1-2 minutes) but it seems no matter what I try with this set up I still end up getting peaks eluding 40+ minutes in and have to wash out the column for much too long as a result.
Any recommendations on how to get those peaks at 30, 40 minutes to elute faster? My only other solvent option at the moment is Methanol, but can buy more if needed.
Otherwise I am thinking I will need to get a new column. I have found a few studies on quantifying DCD online and all seem to use normal phase columns or a couple specifically used HILIC (Hydrophilic Interaction Chromatography) amide columns. Are there any recommendations for what else I could do/ columns I could buy?