Measurement and Results

We analyze for Silicon via ICP-OES in aqueous matrices and perform a calculation to convert the Silicon result determined from the instrument into a Silica result. I want to confirm that the calculation we are using for the conversion is accurate. Can you provide me with the calculation your experts would recommend?

We are working on EPA 6020 B method development for analyzing just Ca, K, Mg, Na in the precipitation water samples. How do we modify the spectral interference check solution (SIC) given in the 6020B method to verify any isobaric interferences? Thank you.

I have a question about the concentration of internal standard. We are using EPA 200.8 to analyze environmental water. I heard that "the concentration of Sc should be 100ppb and Y, In, and Tb is 20-30ppb.". Because we are using multi-element internal standard in ICP-MS, the concentrations of Sc, Y, In, and Tb are the same and I can't make like 100ppb Sc nad 20-30ppb others as what I heard. (1) Can you let me know why the concentration of IS should be different? (2) Please let me know why the concentration of Sc should be higher than others. Also, I heard that I have to use individual internal standard to make internal standard like below. "Sc can start at 50ppb: add 25ul to 500ml bottle or 50ul to 1L bottle. Spike in additional amounts until counts are 2.5-3.5M (guess total of 100ppb) All the other IS (Y, In, and Tb) start at 10ppb: add 5ul to 500ml bottle or 10ul to same 1L bottle. Spike in additional amounts until counts are around 500k (guessing 20-30ppb).". "This is for the optimization of internal standard." (3) Can you explain what is the optimization of internal standard, if you know? (4) Who can use the multi-element internal standard? Thanks and I am looking forward to hearing from you.

I've been told that Lithium analysis by ICP-OES poses problems in high brine solutions? Currently accepting requests for Li analysis in brine. Are there issues and interferences I should be concerned about?

How to validate nonlinear calibrations?

Test of elemental impurities in sodium hydroxide pellets according to ICH Q3D.

We have recently purchased QCP-DMD have some questions regarding the certified values and the acceptance limits stated on the Certificate of Analysis. The certified value for the BOD is 154 ±3 and the acceptance limits are 109-199, Can you please explain why the acceptance limits so wide (30%)? We have checked the standard via the COD value and are getting figures at nearly the nominal value so the standard seems ok.. we would just would like to have an explanation of the acceptance limits.

Do you know why Hg results by ICP-OES are not reliable? The same sample will generate different concentration values on different days....?

I need to make a solution with following ion concentration without using hydroxides. Please advise about the suitable compounds and amounts: Na 150 mmol/L, K 5.0 mmol/L, Cl 115 mmol/L, Ca 0.9 mmol/L.