Article written by Phillip Eleyette, Chemist, Analytical Products Group, Inc.
Complete article from Edition 33 APG eNewsletter
In some cases, the analysis for an analyte is straight
forward but in other cases the initial result may have to be converted in order
to get the correct result.
An example of this is
ammonia as N, NH3 as N, if your instrument is calibrated for ammonia
as NH3 standard then the result must be converted to nitrogen or
N. But if the instrument is calibrated using ammonia as N standard then no conversion is necessary. The molecular weight of ammonia is 17 and the
molecular weight of nitrogen is 14. The conversion for ammonia as N is nitrogen divide by ammonia (14/17 or 0.823).
| Here are some common conversion for nutrients : |
| Nitrite as N, NO2 as N | 14/46 or 0.304 | |
Nitrate as N, NO3 as N | 14/62 or 0.226 | |
Orthophosphate as P, PO4 as P | 30.97/94.97 or 0.326 | |
nbsp;
nbsp;
nbsp;
The numbers are from the atomic weights of the elements from the periodic table.
N=14.007, H=1.00794, O=15.9994, P=30.97
Another conversion is the determining total hardness as CaCO3 and calcium hardness as CaCO3.
Total hardness is the results of separate determinations of calcium and magnesium.
The equation for total hardness is CaCO3, mg/L=2.497[Ca, mg/L] + 4.118[Mg, mg/L].
Calcium hardness is the results of the calcium determination.
Remember, it is important to understand what results you are trying to obtain. This
begins by knowing how your instrument is calibrated and by knowing what the
conversion may be for the analyte
| 
