[lohjxMARCUS]

I understand that the cation and anion balance in water should be of equal proportions (about 50/50), however after a couple of experiments yielded very unfavorable proportions, i calculated my anion and cation concentrations from my results(mg/L) to (meq/L) and found the difference to be >30%.
(Where in analytical laboratories we take <15% to be acceptable)



Type of sample: Water (Slightly Turbid)


Sample Preparation (ICP-OES): Acid digestion for the with Concentration Nitric Acid & 1+1 hydrochloric acid; Both of which will oxidize any metals or any insoluble metals into its soluble form (e.g. Ca2+). Thereafter i will run it in the ICP-OES for analytical determination of my cations and get my results in mg/L.

Sample Preparation (HPIC - Cation exchanger): Filtering the neat sample through a filter paper into a vial, which is directly sent for IC analysis for determination of anions.

My question is, could the difference in the proportion be due to the sample preparation methods employed? I'm digesting my sample with an acid (Which leeches out even more metals into its soluble form) and i'm running a filtered sample before i put it through ion chromatography.

I was thinking that the difference of anion and cation ratio be due to me not having digested my sample for analysis.

 If i ran an undigested in ICP, would i obtain an approximate 50/50 proportion when i compare it to my IC results? what do you guys think, or anyone who has any experience out there would like to share?

Thank you

Marcus