イオンクロマトグラフィーによる牛乳中のマグネシウム及びカルシウムの同時定量のための前処理操作

抄録

Pretreatment procedure of sample was investigated in the ion chromatographic determination of total Mg and Ca in milk. Nitric acid was a better solvent than the other solutions, such as trichloroacetic acid, EDTA and hydrochloric acid, for the extraction of total Mg and Ca from milk. The recommended procedure was as follow: milk sample was diluted five times with distilled water. An aliquot (1.5 ml) of the sample solution and 3.5 ml of 1 M nitric acid were pipetted into a glass tube. After mixing, centrifuging, and filtration with membrane filter, a 100 μl aliquot was analyzed with a precolumn (Shodex Y-521P, 10 mm×4.6 mm i.d.) and a separation column (Shodex Y-521, 150 mm×4.6 mm i.d.). A solution containing 2 mM ethylenediamine and 4 mM tartaric acid was used as a mobile phase (1 ml/min). The detection limits (S/N=3) of the proposed method for Mg and Ca were 30 ppb and 70 ppb, respectively. Relative standard deviation (n=7) was less than 1% for the simultaneous determination of Mg and Ca. The values obtained by the proposed method for Mg and Ca in the milk samples (n=6) were 109118 ppm and 11201190 ppm, respectively, which agreed well with those by the AAS method.