title: Coprecipitation with calcium hydroxide for determination of iron in fish otoliths by collision cell ICP-MS.
abstract: A method has been described for the determination of iron from fish otoliths containing high levels of calcium by collision cell technology (CCT) ICP-MS. Iron (Fe) in otolith solutions was quantitatively coprecipitated with small amounts of calcium hydroxide by adding 1.0 M sodium hydroxide solution. The performance of CCT-ICP-MS pressurized with He/H(2) cell gas was investigated on the elimination of Ca-based spectral interferences at m/z 54, 56 and 57. Molecular ion interferences at m/z 54 and 56 were reduced by 2 orders of magnitude. However, the interferences at m/z 57 increased by the same amount in the presence of Ca in solutions owing to the formation of (40)Ca(16) OH(+) through reactions with H(2) in collision cell, indicating that (57)Fe was not suitable for the determination of Fe from otoliths. Results for (56)Fe suffered significantly from interferences of Ca-based molecular ions when the Ca concentration in solution exceeded 100 microg ml(-1), for which matrix-matched calibration was required for accurate determination. CCT with the aid of He/H(2) cell gas proved to be very effective in eliminating the interferences ((40)Ar(14)N(+) and (40)Ca(14)N(+)) at m/z 54. Presence of Ca up to 300 microg ml(-1) had virtually no effect on the ion signals of (54)Fe, which with low background signals, afforded accurate determination of Fe from otoliths by using aqueous external standards.
authors.affiliation: Jackson State University, Department of Chemistry, PO Box 17910 Jackson, MS 39217, USA.
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Daniels
authors.forename: Zikri
authors.initials: Z
authors.lastname: Arslan
mesh_terms: D000818:Animals; D002126:Calcium Hydroxide / Q000737:chemistry*; D007501:Iron / Q000032:analysis*; D013058:Mass Spectrometry; D010037:Otolithic Membrane / Q000737:chemistry*; D010473:Perciformes / Q000378:metabolism*
chemical_list: D007501:Iron; D002126:Calcium Hydroxide