Validation of methods for analysis of Cu, Fe and Na in process water with an atomic absorption spectrometer - graphite furnace

Södra Cell Mörrum is one of the five paper pulp plants that are included in Södra Cell, and the paper pulp that is produced here is not only sold to Swedish paper mills. Most of the paper pulp is exported to different countries in Europe. In the manufacturing process the plant needs different kind of process water and there are guideline values for how much copper, iron and sodium this water is allowed to contain. Analyzes of this water is in the current situation done with an atomic absorption spectrometric instrument (AAS-instrument) with a flame. Measurements done with flame-AAS of samples that have concentrations near the guideline values for copper, iron and sodium, are not reliable. The reason for not being reliable is that the quantitation limits of these metals are higher than the limit values. An alternative method that should give more reliable values is to analyze with an AAS- instrument with a graphite furnace. The purpose of this project was to perform a method validation of the graphite furnace of the AAS-instrument in the analysis of Cu, Fe and Na. The focus of the project was to find the detection limits for each metal, study the variation and to see if it is possible to analyze these water samples with this technique. The concentrations of the calibration solutions is between 1-10 µg/l for Na, 5-25 µg/l for Cu and 2-20 µg/l for Fe.The detection limits for all metals were slightly below 1 µg/l and during the present circumstances in the laboratory; it would be difficult to get even lower detection limits. There are improvements that can be done to get to the even lower detection limits. The results from this work show that the variation in each sampling cup is very small but if you look at different sampling cups the variation could be large if the cups are not treated in the right way. Further validation analyzes like variation in between days needs to be done. It is possible to analyze these low concentrations of copper, iron and sodium in the water samples with the AAS- graphite furnace, but it is difficult because there are many factors that affect the results. Examples of such factors are the environment where the instrument is placed in the laboratory and the human factor. Further analyzes needs to be done to get a better view of how these factors affect the result