In our project we used Flow Injection combined with Multivariate Analysis to determine the concentration of Calcium and Magnesium in Water. We used the dye Arsenazo III, which complexes with these two metal ions and subsequently changes colour. The colour change was then measured in a spectrophotometer, which gave a spectrum with a peak for calcium at around 600-670 nm and for magnesium from 580-630 nm. Concentrations of calcium and magnesium in naturally occurring waters range from 70 to 530 ppm, whereas the concentrations we were working with were 0.089-4.5 ppm for calcium and 0.054-2.6 ppm for magnesium. We analysed the data in the Unscrambler 8.0 Upgrade. The mathematical method that we used was PLS1 (Partial Least Squares) regression.
In our project we did not get conclusive results. In the Discussion we suggest several reasons for that. Our main concern was the purity of chemical substances we used for preparation of the carrier solution. Other possibilities, among others, include a wrong choice of multivariate calibration method (PLS1 instead of PLS2), imprecise assumptions regarding our dye. If we were to repeat this experiment, we would try to change the aforementioned aspects. However, we believe the combination of flow injection and spectrophotometry is an economical and relatively easy solution for testing water samples on a big scale. We could also try another analytical method (e.g. Ion Chromatography, FAAS).
|Uddannelser||Kemi, (Bachelor/kandidatuddannelse) Bachelor|