Ion chromatographic determination of phosphorus soluble in different extracting media in fertilizers
Mazzei, R.Antonio.; Scuppa, S.
Journal - Association of Official Analytical Chemists 89(5): 1243-1248
2006
ISSN/ISBN: 0004-5756 PMID: 17042171 Document Number: 598052
A new method based on ion chromatography (IC) was developed for the determination of phosphorus in fertilizers. Fertilizers were extracted with water, mineral acids, and 2% formic acid, 2% citric acid, and neutral ammonium citrate solutions according to European Regulation No. 2003/2003 of the European Parliament and the Council of October 13, 2003, or the Decree of the Italian Agriculture Minister of June 17, 2002; the extracts were analyzed by direct injection, after simple filtration, by IC on an IonPac AS19 (250 x 4 mm id) column, using a KOH (21-50-21 mM) gradient and suppressed conductivity detection. The calibration plot was linear over the range of 5-50 mg/L (r(2) of > 0.999). The method was evaluated by comparison with a gravimetric method according to established norms. Associated uncertainty at the 95% confidence level was established as 0.47% for the determination of 3-46% P2O5 by IC. A good chromatographic separation of phosphorus forms such as phosphates and phosphites, and some other important an ions like nitrates, chlorides, and sulfates present in many commercial fertilizers was also possible, with a linear response over the range of 5-50 mg/L. After a more complete validation, this IC: determination of phosphorus could replace more tedious methods such as those using gravimetric determinations.