This paper describes the development of a method for quantitative measurement of the elemental composition of particulate matter (PM) in seawater. This method is based on use of wavelength dispersive X-ray fluorescence (WDXRF) analysing PM harvested on various filter types. As the amount of material is less than a monolayer of cells on the filters we reduced the need for absorption correction. Given the appropriate combination of filters and elements the detection limits are low: <1 µg/filter for carbon (C), nitrogen (N), and <0.1 µg/filter for silicon (Si), phosphorus (P), calcium (Ca) and iron (Fe). The analytical range used was 90–750 µg C, 23–116 µg N and 7–30 µg P, depending on the filters applied. Calibration constants for the elements included in this study were obtained from analysis of known quantities of chemical compounds on filters or silver plates. For carbon and nitrogen we also used comparative measurements of Synechococcus sp. cultures by CHN analyser and WDXRF. We harvested PM from 150 ml to 2000 ml on each filter in three replicates, obtaining less than 5% analytical variability between the replicates. One of the challenges using WDXRF as proposed here is the absorption of X-ray signals by the filter and variability of cell/particle sizes, and, consequentlyly, the variability of harvested PM on various filters. We find that an anodisc filter is best suited for C and N, while polycarbonate filters are best for heavier elements. Here we present analytical details and some data from field experiments related to C, N, P, Si, Ca and Fe in particles from seawater.

To minimize waste, improve process safety, and reduce costs, modifications were implemented to a method for quantifying gallium in plutonium metal using wavelength dispersive X-ray fluorescence. These changes included reducing sample sizes, reducing ion exchange process volumes, using cheaper reagent grade acids, eliminating the use of HF acid, and using more robust containment films for sample analysis. Relative precision and accuracy achieved from analyzing multiple aliquots from a single parent sample were approximately 0.2 and 0.1%, respectively. The same precision was obtained from analyzing a total of four parent materials, and the average relative accuracy from all the samples was 0.4%, which is within programmatic uncertainty requirements.

A novel method for preparing thin films was investigated for quantifying gallium and iron in plutonium solutions using WDXRF. This technique was developed to eliminate the potential for radioactive liquid to leak into the spectrometer, decrease specimen preparation time, and minimize waste. Samples were cast in μL quantities onto Kapton, and a surfactant was added to disperse the solution uniformly across the Kapton. After drying the specimens, they were sealed in a cell for analysis. Results to date indicate the method can provide a relative precision of ∼0.5% for gallium and ∼2% for iron, which is more than sufficient for routine sample analyses.