Ion chromatography of alkaline earth and heavy metal ions by on-column derivatization with bisazochromotropic acid

• Published in: Journal of Chromatography A 1993-12, Vol.657 (1), p.87-93
• Main Authors: Wada, Hiroko, Matsushita, Muneyoshi, Yasui, Takashi, Yuchi, Akio, Yamada, Hiromichi, Nakagawa, Genkichi, Ohtsuka, Chizuko
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Other chromatographic methods
• ISSN: 0021-9673
• DOI: 10.1016/0021-9673(93)83038-T

Two columns (50 mm × 4.6 mm I.D.) packed with sulphonated styrene-divinylbenzene (PS-DVB) gel (particle size 10 μm) and sulphonated silica gel (particle size 5 μm) were used for the separation of alkaline earth metal and several transition metal ions. The mobile phase contained 3-morpholinopropanesulphonic acid (MOPS)-NaOH buffer and a colour-forming chelating agent, and on-column derivatization and spectrophotometric detection were employed. Arsenazo III, Chlorophosphonazo III, Carboxyarsenazo, Sulphonazo III and Dimethylsulphonazo were examined as mobile phase components for good separation and highly sensitive detection. The PS—DVB gel column and Chlorophosphonazo III gave the highest sensitivity. Ca 2+, Sr 2+ and Ba 2+ were separated in 5 min with a mobile phase containing 2 · 10 −4 M Chlorophosphonazo III and 2.5 · 10 −2 M MOPS—NaOH buffer (pH 7.0), whereas Mg 2+ was eluted after 30 min. An irregular retention sequence was observed, i. e., Ca 2+ < Sr 2+ < Ba 2+ ⪡ Mg 2+; the capacity factors ( k′) were 1.3, 3.3, 5.3 and 42.8, respectively. The separation of alkaline earth and several transition metal ions was also examined. Application to the determination of Ca 2+ and Mg 2+ in tap water is described.