Rapid and simultaneous determination of Strontium-89 and Strontium-90 in seawater

A rapid method has been developed for the direct determination of radiostrontium ((89)Sr and (90)Sr) released in seawater in the early phase of an accident. The method employs a fast and effective pre-concentration of radiostrontium by Sr-Ca co-precipitation followed by separation of radiostrontium using extraction chromatography technique. Radiostrontium is effectively separated in the presence of excessive dominant salts of seawater. Čerenkov and liquid scintillation assay (LSA) techniques are used to determine (89)Sr and (90)Sr. Sample preparation time is approximately 4 h for a set of 10 samples. The method was validated using spiked seawater samples at various activity ratios of (89)Sr:(90)Sr ranging from 1:10 to 9:1. The mean chemical recovery of Sr was 85 ± 3%. (90)Sr showed variable relative bias which enhanced with increasing ratio of (89)Sr:(90)Sr and was in the range ± 21%. The highest biases of (90)Sr determination were due to lower activity concentrations of (90)Sr and are regarded as acceptable in emergency situations with elevated levels of radiostrontium in the sample. The minimum detectable concentration (MDC) of (90)Sr and (89)Sr varied at different (89)Sr:(90)Sr ratios. For 0.1 L seawater and 15 min counting time on a low background Hidex liquid scintillation counter (LSC), the MDC of (90)Sr was in the range of 1.7-3.5 Bq L(-1) and MDC of (89)Sr was in the range 0.5-2.4 Bq L(-1).