Year: 2025
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide A method is reported for the measurement of 227 Ac using inductively coupled plasma mass spectrometry (ICP-MS) and isotope ratio analysis. The method has application for the quality testing of 225 Ac produced as an active pharmaceutical ingredient (API). The 225 Ac/ 227 Ac isotope ratio is measured directly from ICP-MS count rate data and converted to an 225 Ac/ 227 Ac activity ratio by using basic nuclear decay equations. The activity ratio, which is itself a measure of radioisotopic purity, is coupled with an orthogonal measurement of 225 Ac activity to obtain an absolute 227 Ac activity. Thus, the method may be used to report the 227 Ac content of an 225 Ac API in absolute or relative terms. The methodology was evaluated against appropriate validation criteria (e.g., linearity, accuracy, precision, specificity) by analyzing a series of solutions containing known quantities of 225 Ac and 227 Ac. Accuracy was evaluated using a spike recovery study. The spike recoveries were 100–108% for samples with 0.100 to 2.00 ng L –1 of 227 Ac and 74–91% for 0.025 ng L –1 of 227 Ac. Intermediate precision was measured as 4.1% using replicate measurements ( n = 12, two instruments) of 227 Ac spiked samples (0.5 ng L –1 ). The instrumental detection limits for 227 Ac were shown to be as low as 23 Bq L –1 (0.0086 ng L –1 ), which is lower than comparable methods for the quantification of 227 Ac in 225 Ac APIs. Actinium-225 samples are analyzed under this method without any need for 225 Ac decay or 227 Ac daughter in-growth. Sample preparation involves simple dilution of the 225 Ac API in 3% HCl/1% HNO 3 . The analysis takes as little as 2 h using equipment common to radioanalytical laboratories. Thus, the measurement of 227 Ac by this method can be performed as part of routine 225 Ac API quality testing and reported on release documents. This is a significant advantage over radiometric methods reported for the quantification of 227 Ac in 225 Ac APIs, which require days to weeks before reportable results can be obtained. The measurement of 227 Ac by ICP-MS and isotope ratio analysis is rapid, accurate, and sensitive. The implementation of this method for 225 Ac API quality testing will help 225 Ac producers and end-users ensure product quality and demonstrate regulatory compliance.
Source: ACS Omega
Language: English
Subfield: Radiation
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,935
Funder: U.S. Department of Energy
OpenAlex ID: W4416674058