A pre-concentration technique for determination of 32 P in natural waters
Artificial 32P (T 1/2 = 14.28 days) can be used to tracethe behavior of a major nutrient, phosphate, in aquatic systems. Althoughliquid scintillation or Cerenkov counting of high energy betas of 32P is very sensitive, its usefulness for low level activities is limitedby inefficient pre-concentration techniques. We found that precipitation ofZrPO4 is an excellent method for pre-concentration of 32Pfrom natural waters. After acidification (pH ~2) of a 1-liter sample, about1 ml 20 mM phosphate carrier is added and equilibrated with natural phosphates.Excess Zr carrier (about 40 mg) is then added to fully precipitate both thenatural and added phosphates in the sample. The ZrPO4 precipitatesare collected onto a Whatman GF/B type filter which becomes translucent inUltima Gold A/B cocktail. We obtained constantly high 32P recoveries(about 97%) through the entire procedure for hundreds of samples during ahydrologic tracer test. Furthermore, we could process about one dozen samplesper hour, and when counting with a portable liquid scintillation counter theresults are about 500-fold more sensitive than direct Cerenkov counting.
KeywordsNatural Water Liquid Scintillation Counter Scintillation Counter Major Nutrient Tracer Test
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