Aquarium strontium

Gilles de Pelichy, L. D. Adams, C. Smith, E. T. Analysis of the Essential Nutrient Strontium in Marine Aquariums by Atomic Absorption Spectroscopy, /. Chem. Educ. 1997, 74, 1192-1194. 

The concentration of strontium in a sea water aquarium is determined by atomic absorption using the method of... 

The method of standard addition (Section 5-3) compensates for many types of interference by adding known quantities of analyte to the unknown in its complex matrix. For example, Figure 21-27 shows the analysis of strontium in aquarium water by standard addition. 

The method of standard addition, described in Section 5-3, compensates for many types of interference by adding known quantities of analyte to the unknown in its complex matrix. For example. Figure 20-17 shows the analysis of strontium in aquarium water by standard addition. The slope of the standard addition curve is 0.018 8 absorbance units/ppm. If, instead, Sr is added to distilled water, the slope is 0.030 8 absorbance units/ppm. That is, in distilled water, the absorbance increases 0.030 8/0.018 8 = 1.64 times more than it does in aquarium water for each addition of standard Sr. We attribute the lower response in aquarium water to interference by other species that are present. The negative jc-intercept of the standard addition curve, 7.41 ppm, is a reliable measure of Sr in the aquarium. If we had just measured the atomic absorption of Sr in aquarium water and used the calibration curve for distilled water, we would have overestimated the Sr concentration by 64%. 

Strontium is quite common in seawater. Some organisms use strontium sulfate as a skeletal material. Strontium is added to the water in aquariums, as the decorative stony corals need it. Strontium has no function in the human body. (It is the most abundant element in the human body without a known function there.) Nor is barium essential for Hfe indeed it is toxic. The symptoms of barium poisoning are colic, diarrhoea, vomiting and paralysis. The content of barium in food plants is as a rule low (part per million levels) but there is an exception Brazil nuts may contain as much as 1% barium. The metabolism is stimulated by barium, but to such a high degree that the heart begins to beat erratically (ventricular fibrillation). Barium salts are thus toxic to humans, but the use of barium sulfate as an X-ray contrast medium is accepted because of its very low solubility. 

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