Determination of elements in algae by different atomic spectroscopic methods

The chemistry of substances derived from plants has received a great deal of attention in the last several decades. Today, natural products and their synthetic analogs also play an important role in the pharmaceutical and food industry. Several interesting reviews on algae were published in the last 10 years. Algae, especially the red algae, are very helpful in every day practice in many fields, e.g. algal polysaccharides, agar, carrageenan and some algae extracts are used in agricultural, medicines and in food products, respectively (The Constituents of Red Algae, 1999; Gelling Hydrocolloids in Food Products Applications, 1979, p. 186; Marine Natural Products Chemistry, 1997, p. 337; Algae Polysaccharides, 1983, p. 195). The biological and pharmaceutical properties promote interest among chemists to focus their attention on algae, as yet, a wide open field (Synthesis and Proceedings of the Second EUMAC Workshop, Marine Eutrophication and Bentic Macrophytes, p. 2). The most extensively studied algal phyla are Chlorophyceae (green algae) (J. Phycol. 26 (1990) 670), Rhodophyceae (red algae) (J. Phycol. 25 (1989) 522) and Phaeophyceae (brown algae) (J. Phycol. 31 (1995) 325; J. Phycol. 32 (1996) 614). Concentrations of four elements (Ca, Mg, K, Na) were determined in the above-mentioned algal phyla by different atomic spectroscopic methods (F-AES, ICP-AES) after the digestion of algal samples with cc. HNO₃ in a microwave apparatus. Not only the Ca and Mg contents, but the ratio of the calcium to magnesium was calculated in every case. This ratio was lower (0.5–0.8) in green algae than in the red and brown algae (1.3–14.4). Therefore, the green algae are better magnesium sources than the red and brown. The elemental composition is of great importance in the ion system of human organism. It is usually characterized by the ion quotient ([Ca²⁺]+[Na⁺]:[Mg²⁺]+[K⁺]), which is approximately 1.0 under ideal conditions. However, in the human body this mole ratio generally varies between 2.5 and 4.0. The ion quotient was calculated by averaging between 1 and 2 in different algal phyla. This means that the 2.5–4.0 mole ratio can be decreased by different algal foods in the human organism.