How long does it take to analyze Radium-226, Radium-228, and Gross Alpha for a water sample? Is there some dependency on the sample?
We have been experiencing high turnaround times for these tests in other labs and a search online indicates that the tests can take anywhere from 5 days to 8 weeks, which seems very broad for a specific test.
TestAmerica Expert: Terry Romanko
Expert's Response:
Let me first say that 8 weeks is rather long for a turnaround time (TAT) for these methods. A standard TAT would probably be more in the 4-week time period. 5-business days (7 calendar days) is possible for some (see below), but definitely expect surcharges for Rush services.
Radium-226 in groundwater samples can be analyzed by a couple of different methods. The two main methods are based upon EPA 903.0 and EPA 903.1. Both methods require some amount of waiting time in order to provide actual Ra-226 results.
A summary from method 903.0 (Alpha-Emitting Radium Isotopes in Drinking Water):
The radium in the drinking water sample is collected by coprecipitation with barium and lead sulfate, and purified by reprecipitation from EDTA solution. Citric acid is added to the drinking water sample to assure that complete interchange occurs before the first precipitation step. The final BaSO4 precipitate which includes radium-226, radium-224 and radium-223 is alpha counted to determine the total disintegration rate of the radium isotopes.
A summary from method 903.1 (Radon Emanation Technique):
The radium-226 in the drinking water sample is concentrated and separated by coprecipitation on barium sulfate. The precipitate is dissolved in EDTA reagent, placed in a sealed bubbler and stored for ingrowth of radon-222. After ingrowth, the gas is purged into a scintillation cell. When the short-lived radon-222 daughters are in equilibrium with the parent (4h), the scintillation cell is counted for alpha activity.
As you may notice, both methods utilize the barium sulfate co-precipitation. 903.1 speaks of "ingrowth" – this is the process of the parent (Ra-226) decaying to the shorter-lived daughters (Rn-222, etc) where the daughters increase in activity until eventually they reach equilibrium with the parent. The method in step 8.6 calls for 4-8 days of ingrowth – the more ingrowth, the lower the detection limit you can hit for a given sample. This method is somewhat glassware intensive (need specialty glassware), and this can cause a "pinch-point" for analyses, possibly causing longer TAT. However, a 14-day TAT is possible (expect surcharges for Rush services), but a 28-day TAT would be more standard. Longer TAT would be due to lack of capacity (either due to lack of glassware or measurement instrumentation, or due to a spike in sample load).
TestAmerica's Richland, WA laboratory can supply the 903.1 analysis.
903.0 was written as a screening technique for alpha-emitting radium. It could be considered as written as a potential high-biased Ra-226 result. If the Total Alpha-emitting radium result is less than the action level, you know the Ra-226 result has to be. The advantage to this is that no waiting time is needed, thus a 7-day TAT is possible (again, expect surcharges for RUSH). 14-21 days would be more standard for this method.
TestAmerica's St. Louis laboratory utilized a modification to this method to report Ra-226. The method mentions Ra-226, Ra-224, and Ra-223 as alpha-emitting radium isotopes. Ra-223 (a daughter of Th-227) is not normally present, as the parent decay chain is not considered "naturally-occurring." It is possible it might be found at isolated sites (mainly DOE sites). Ra-224 is a short-lived daughter in the Th-232 decay chain. As it is short-lived, after the initial radium separation/co-precipitation, the lab waits for decay of the Ra-224. Waiting 14 days allows for 93% of any Ra-224 present to decay out; 21 days allows for 98% to decay out. The laboratory thus can report Ra-226 using 903.0, with a decay/waiting period of 14 or 21 days (depending upon client need/confidence). An intercomparison of the 903.1 vs 903.0 results was performed between the St. Louis and Richland laboratories with showing comparable results. 21-28 days (depending upon decay period) is typical TAT provided by the St. Louis lab.
Gross alpha is a quick screening test. A 7 day TAT or shorter is possible, but not standard.
Radium-228 has a short ingrowth period built into the method, but a 7-day TAT is possible (but not standard). In St. Louis, these are typically "piggy-backed" with the Ra-226 analysis, so expect a similar TAT.
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