Her er noget som jeg er faldet over og vil smide det i denne lille tråd til information for andre, under mit research.
I er velkommen til at kommentere, linke osv. og kan i ikke læse det. Google translate is your friend
Hello Mr Harms,
There are great differences between the various ICP-OES systems available on the market. We have chosen the Arcos 2 from Spectro. It is the only ICP-OES system I know that can measure chloride. It also has better optics than the cheaper instruments (e.g. Blue) from the same manufacturer.
ICP-OES systems can measure some elements better than others. For some elements relevant to marine aquaristics, we can certainly achieve detection limits of less than 1 µg/l. These include manganese (~0.1 µg/l), lithium (~0.15 µg/l), vanadium (0.3-0.5 µg/l), nickel (0.7 µg/l) and cobalt (0.5 µg/l). Most other trace elements have detection limits between 1 µg/l and 2.5 µg/l. Few, fortunately less relevant, elements show higher detection limits. These include selenium (6 µg/l) and thallium (7 µg/l).
In the evaluation of the water analyses, we have oriented ourselves to the natural seawater. The ideal values are surrounded by a tolerance range. Both are adjusted to the measured salinity.
Please note that if an ideal value is given as 0.1 µg/l at 35 PSU, the value in natural seawater is less than or equal to 0.1 µg/l.
Mit freundlichen Grüßen / With best regards
Dr. Ben Funk
Laborleitung
I wanted to quickly address the lower detection limits of the ATI ICP-OES. I get a lot of questions about this topic, and I wanted to bring some clarity. I was also a little foggy on this.
As you already know, our daily elements should remain undetected. However, as some of you may have noticed ATI does list their “Calculated Reference Values” at very low limits. At first glance this implies to me that they can test down to these levels. They also list their “Lowest Limit of Detection” for each individual element on their website. Most limits are within our target range. So why do we want our elements to come back undetected if ATI’s ICP-OES can detect the dailies at these lower limits? Great question right.?
Andre did tell me a while ago to keep the dailies undetected. I never thought much about it, because I trust his judgement. I’ve told this story before, but when I met this guy 10 years ago he was playing with trace elements even back then. He’s been doing this quite a long time. For this reason I never question too much. Recently, after looking at ATI’s data I sent an email to ATI, and also to a few others about ICP-OES lower limits. Then I reached out to Andre to confirm again about the lower limits for dailies. I wanted to be dang sure that all my undetected elements aren’t really “undetected.”
So here’s my understanding about this topic. The reference values listed on our analysis are merely values of what the NSW level would be along with our measured salinity. These values are basically theoretical calculation’s. ATI’s lower detection limits do not account for “tolerances” near the lower limits. For me this equates to questionable accuracy below a few ug/l to say the least. So basically any values that show up for dailies can’t be fully trusted around 2 ug/l or below.
I know Andre has done several ICP-MS to ATI-OES comparisons. Avoid adjusting to their numbers.
Also, just for the sake of clarity for newer reefers, because this question comes up a lot. Avoid making any corrections based off ATI’s recommendations on your analysis. We dose different products that have different potency. Using ATI’s recommendations (if not using their products) can lead to major issues and quite possibly a nuked system.
