I need to analyse trace levels of 6-methyl-thiouracil in a plating bath (highly alkaline solution of zinc). I tried Nova-Pak C18 but the retenntion is very small and not much influenced by mobile phase composition (e.g. PH and ion-pair reagent). I also tried ion-exchange columns (cation and anion) but retention was still very small. I tried and ald XTerra RP18 at pH about 11.5 and the retention seemed to be quite reasonable, so i ordered a new one (but not received it yet). I also tried GC after derivatisation but the boil point is propably still too high. Does anybody have any experience with this compound? Any help would be great.