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Combined compounds
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On a number of occasions samples which had non detects for the individual carbon band groups (10-14,15-28, 29-36) did not have a value in the “Result field” for and could not import. I assigned a value of <100 and imported. Furthermore, as the lab reports TPH C10-C36 and I have realaised, after inputting the data from our first groundwater monitoring round, ESdat auto combines these values with the ESdat Combined Compounds function there is now two entry’s per well location for C10-C36 (Sum of Total).For non-detects one of these reports ,50 µg/L and the other(ESdat combined) , 200µg/L.
I have a couple of questions regarding this issues. 1. What is the benefit of having an ESdat Combined Compound function for TPH’s if the lab already reports it. Or is this function just in here for when the labs don’t provide a total or the user wants a different convention for dealing with non detects in a summation scenario. 2. How can it be disabled. 3. How can the entry’s that are already in ESdat, for ESdat combined C10-C36 (Sum of Total), be deleted. Edited by moderator Tuesday, November 17, 2009 5:48:49 AM(UTC)
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Rank: Administration
Groups: Registered, Administrators Posts: 498  Location: Byron Bay Was thanked: 19 time(s) in 19 post(s)
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If you don't know the detection limit, and you are wanting to sum non-detects it is going to involve some caveats. I would probably recommend a value of 0 rather than 100 if you can’t find the detection limit, however, so long as you are aware what you have done. You can modify the way ESdat treats non-detects in this calculation under Setup – Chemistry. The only benefit in using the calculation in ESdat, if the lab already reports the sum is if you don’t like the way the lab calculates it with regards to non-detects etc.. To prevent ESdat doing the calculations: The compounds used in Combined Compounds are stored in the zRef_Combined_Compounds table. You can remove the contents of this table if you don’t wan’t specific calculations. To Delete: You can filter the “Chemistry” table for a Method Name of “ESdat Combined” and delete. Alternatively, you can re-run the combined compound calculation (Setup – Chemistry) with all the combined compounds deleted.
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Rank: Administration
Groups: Registered, Administrators Posts: 498 Location: Byron Bay Was thanked: 19 time(s) in 19 post(s)
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In Version 5 lots of improvements have been made, the guidelines can be run against a specific matrix, and in the SQL Server version the Combined Compounds Settings (including multiplier) can be associated with a Site or a Project. In the SQL Server version the option to show a < and the sum of the non-detects isn't shown (we may put back), however the same is achieved by entering a non-detect multiplier of 1 - if 1 is used and all the results are non detects it will show a < prefix for the result.
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