Measurement of alkaline and earthy ions in fish otolith and sea water using a high performance ion chromatography

Fish growth and the relation between growth and environmental conditions offer a good opportunity for measuring alkaline and earthy ions in fish otoliths. The analytical method must involve high sensitivity when attempting to discriminate between fish growth and environmental conditions. The aim of this paper is to propose a chromatographic method, with low detection limits, as a new approach in determining some important micronutrients present in sea water and fish otoliths. The work samples are: coastal, off-shore and sediment waters and fish otoliths (Engraulis encrasicholus, Mullus barbatus, Umbrina cirrhosa, Sciaena umbra, Pagellus erythrinus) in the Adriatic Sea and the Canal of Sicily. The analytical method includes an IONPAC CS12A chromatographic column and a 18 mM methanesulfonic acid eluent. The detection limit readings obtained with this method, for one E. encrasicholus fish otolith, weighing 2.6 mg are equal or inferior to 0.1 ìg/L for lithium (Li), 59 ìg/L for sodium (Na), 46 ìg/L for ammonium (NH4), 23 ìg/L for potassium (K), 13 ìg/L for magnesium (Mg), 88 ìg/L for manganese (Mn), 2.567 ìg/L for calcium (Ca) and 13 ìg/L for strontium (Sr). The HPIC method minimizes overlaps such as Na on Li, and NH4 in seawater and Ca on Mg and Sr in fish otolith. These elements are an essential constituent present in otoliths when describing the relation between growth and environmental conditions. Good separation among analytes is achieved within 16 min.