WEF Discussion Forums
Laboratory Management and Technical Issues
Flame AA analysis
i realize this is a wastewater forum, but does anyone own a flame AA? I am having problems consistently quantifying Ca and can't seem to get an answer from the manufacturer. Can anyone help?
City of Lubbock, TX
Johnny, it doesn't look like anybody is taking this one on. It's not because "this is a wastewater forum"...it isn't...it's a lab forum that is oriented toward water because it is hosted by the Water Environment Federation. Hundreds of water labs, both drinking and waste, have flame AAs, and I would imagine many of the folks following this forum have one or more in their lab.
My advice would be to be a little more specific. Just what kind of a problem are you having with Ca? Do other metals give you any problems? Is your sample matrix something other than water (I suspect it is or you wouldn't have made the remark about this being a water forum), and have you tried doing matrix spikes? Results? Have you tried doing matrix spikes on an aqueous sample? Results?
The more information you can give, the more likely you are to get some input.
I work in the Odessa laboratory and we have been using flame AA until about a month ago. We just got our ICP in and our Perkin Elmer 3110 AA spectrometer mercifully died from an electrical fire last month.
We were able to get NELAC accretidation for Cd,Cr,Cu,Pb,Ni,Zn and Ag and we can recover them with little trouble, but calcium and magnesium have been crapshoots.
We had our best luck when we kept the Ca curve within the linear range of 5 mg/L. You have to make sure you don't have any contamination (which can be tricky with something so ubiquitous as calcium) and don't add the Lanthanum Oxide if you can help it. When I would run a nonlinear curve up to 25 mg/L I would consistently get about 80 % recovery on a 10 mg/L LCS. You will have to dilute your samples to fit the curve. I had a few liters of digested water I used for dilution rather than DI or distilled water. Keeping the matrix matched up to the blank and cal curves made a significant difference for the better.
Hope this helps at least a little. Calcium and I had a hate-hate relationship for the last 7 years.
Lance Ward (Stressed Organism from the old forum...)
City of Odessa, TX laboratory