Hi all,
I would appreciate if you could guide me about the question below:
1- I have some solutions which contain Ca: 50-300 ppm, Mg: 13-51 ppb!!!, and Na: 2-10ppm.
Can I prepare the Mg and Na standards in those range separately and run the samples for each standard to measure the Mg and Na ?
I mean once I put just Mg standards and increase the flow rate to have better Mg peak and measure the Mg concentration.
Then put Na standards and run those samples again to measure the Na concentration.
And third time measure the Ca.
Or I should mix the standard solutions and dilute them together?
Regards,
Dear Taher,
your Mg concentration is probably far too low to get an accurate IC measurement, think you'd be better off with another method for Mg.
Na will probably not overlap with Mg or Ca (depends on your column), so I wouldn't see the point of using a separate std for that.
Since the peaks in your sample (Ca & Mg) will overlap if you run it undiluted, I don't see any advantage using single ion standards anyhow.
I'd run this sample twice, once 10x diluted, for the Ca, and maybe undiluted for Na, 50 ppm Ca probably won't interfere, 300 ppm might.
regards,
Pieter
To add to what Pieter said, you can use separate standards for calibration, but you run the risk of overlap. Do you have access to ICP? That's probably better to analyse all three together and will easily detect at the ppb level.
Contrary to what Pieter says above, measuring Mg at 13-51 ppb via Ion Chromatography is easily done by direct injection and determinations at 10 ppt are routinely done in analysis of DI water used in semiconductor manufacturing athough in the later case it is necessary to use a concentrator column.
Regarding your question, the best option is to mix your standard solution at concentration ratios that match your sample as this will minimize the number of standards you need to prepare for calibration.
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