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@AlbertT,
@TomTheSeagull recently shared a link to an ICP study on Serious Reefs comparing seven vendor results for the same water sample
https://www.patreon.com/SeriousReefs/posts/reef-icp-test-ep-168983578?collection=2301031
Luckily, there was a link to their data (2-MS, 5-OES) which I reanalyzed. Note that I am not including nitrate, phosphate, alkalinity, or salinity in the analysis.
I first compared ATS to Oceamo MS results. The Log-Log plot shows a near perfect match of the results with a bit more variation at the lowest concentration. This was fortuitous because it gave me a benchmark to compare the OES results.
For the OES data analysis, I plotted the relative percent difference between the OES and averaged MS results ((OES - average MS) / average MS). The plot with elements ordered by increasing averaged MS concentration shows the OES results gradually deviating from MS results with decreasing concentration until silicon where variability explodes. Up to this point, the OES results are generally within 5-10% of the MS results. The negative 100% points are instances where the element was not detected.
The next relative percent difference plot has a change in X-axis from elements to concentration (μM), showing that the rapid increase in variability after lithium corresponds to concentrations below 10 μM. Note that Oceamo but not ATI OES maintains low variability to about 0.1 μM, corresponding to F in the previous plot.
What this analysis suggests is that an MS analysis is required for accurate trace element concentration below 10 μΜ (previously I proposed a 10 ppb limit) with the possible exception that Oceamo OES may provide useful information down to 0.1 μM.[/USER]
@TomTheSeagull recently shared a link to an ICP study on Serious Reefs comparing seven vendor results for the same water sample
https://www.patreon.com/SeriousReefs/posts/reef-icp-test-ep-168983578?collection=2301031
Luckily, there was a link to their data (2-MS, 5-OES) which I reanalyzed. Note that I am not including nitrate, phosphate, alkalinity, or salinity in the analysis.
I first compared ATS to Oceamo MS results. The Log-Log plot shows a near perfect match of the results with a bit more variation at the lowest concentration. This was fortuitous because it gave me a benchmark to compare the OES results.
For the OES data analysis, I plotted the relative percent difference between the OES and averaged MS results ((OES - average MS) / average MS). The plot with elements ordered by increasing averaged MS concentration shows the OES results gradually deviating from MS results with decreasing concentration until silicon where variability explodes. Up to this point, the OES results are generally within 5-10% of the MS results. The negative 100% points are instances where the element was not detected.
The next relative percent difference plot has a change in X-axis from elements to concentration (μM), showing that the rapid increase in variability after lithium corresponds to concentrations below 10 μM. Note that Oceamo but not ATI OES maintains low variability to about 0.1 μM, corresponding to F in the previous plot.
What this analysis suggests is that an MS analysis is required for accurate trace element concentration below 10 μΜ (previously I proposed a 10 ppb limit) with the possible exception that Oceamo OES may provide useful information down to 0.1 μM.[/USER]
