The determination of calcium-45 in sea water, corals and calcareous algae by liquid scintillation counting

Calcium isolated from various fractions of corals and algae is converted into nitrate and dissolved in a water-ethyleneglycolmonoethylether-dioxane cocktail in the ratio of 1:2:20 using PPO and 1-dimethyl-POPOP as scintillators. 45Ca in sea water is counted directly after dilution of 1:10 with water. The carrier capacity of the system is 3 mmole Ca (NO3)2/23ml (120 mg Ca). The counting efficiencies at minimum and maximum carrier concentration are 88, 7% and 78, 5% respectively. The scintillator solvent system is chemically stable and counts are highly reproducible. Instagel in the ratio of 10 ml to 1 ml aqueous solution gives counting efficiencies in the region of 80%. Sea water can be incorporated directly. Algal calcium is counted as the nitrate or the chloride. The carrier capacity of Instagel is higher and the counting efficiency is less affected by large concentrations of carrier and excess acid. © 1974 Taylor & Francis Ltd.