Stability of Solid Uranyl Peroxides under Irradiation.

The effects of radiation on a variety of uranyl peroxide compounds were examined using γ-rays and 5 MeV He ions, the latter to simulate α-particles. The studied materials were studtite, [(UO2)(O2)(H2O)2](H2O)2, the salt of the U60 uranyl peroxide cage cluster, Li44K16[(UO2)(O2)(OH)]60·255H2O, the salt of U60Ox30 uranyl peroxide oxalate cage cluster, Li12K48[{(UO2)(O2)}60(C2O4)30]·nH2O, and the salt of the U24Pp12 (Pp = pyrophosphate) uranyl peroxide pyrophosphate cage cluster, Li24Na24[(UO2)24(O2)24(P2O7)12]·120H2O. Irradiated powders were characterized using powder X-ray diffraction, Raman spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, and UV-vis spectroscopy. A weakening of the uranyl bonds of U60 was found while studtite, U60Ox30, and U24Pp12 were relatively stable to γ-irradiation. Studtite and U60 are the most affected by α-irradiation forming an amorphous uranyl peroxide as characterized by Raman spectroscopy and powder X-ray diffraction while U60Ox30 and U24Pp12 show minor signs of the formation of an amorphous uranyl peroxide.

Lab on paper: iodometric titration on a printed card.

A paper test card has been engineered to perform an iodometric titration, an application that requires storage and mixing on demand of several mutually incompatible reagents. The titration is activated when a user applies a test solution to the test card: the dried reagents are reconstituted and combined through a surface-tension-enabled mixing (STEM) mechanism. The device quantifies 0.8-15 ppm of iodine atoms from iodate in aqueous solutions. This is useful, for example, to quantify iodine levels in fortified salt. A blinded internal laboratory validation established the accuracy as 1.4 ppm I and the precision as 0.9 ppm I when the test card was read by newly trained users. Using computer software to process images, the accuracy and precision both improved to 0.9 ppm I. The paper card can also detect substandard ß lactam antibiotics using an iodometric back-titration. When used to quantify amoxicillin, good distinction is achieved between solutions that differ by 0.15 mg/mL over a working range of 0-0.9 mg/mL. The test card was designed to meet the World Health Organization ASSURED criteria for use in low resource settings, where laboratory-based analytical procedures are often not available.

Green design of a paper test card for urinary iodine analysis.

When young children do not receive adequate amounts of the micronutrient iodine in their diet, their growth and cognitive development can be impaired. Nearly every country in the world has programs in place to track iodine intake and provide supplemental iodine if needed, usually in the form of fortified salt. The iodine nutrition status of a population can be tracked by monitoring iodine levels in urine samples to see if the median value falls in the range of 100-300 micrograms of iodine per liter of urine (µg I/L), which indicates adequate or more than adequate iodine nutrition. Many low and middle-income countries (LMIC) do not have a laboratory capable of carrying out this challenging assay, so samples must be sent out for assay in external labs, which is expensive and time-consuming. In most LMIC, population iodine surveys are carried out every 5-10 years, which limits the utility of the data for program monitoring and evaluation. To solve this problem, we developed a field-friendly paper test card that uses the Sandell-Kolthoff reaction to measure urinary iodine levels. A blind internal validation study showed that 93% of samples (n = 60) of iodide in an artificial urine matrix were categorized correctly by visual analysis as deficient, adequate, or excessive for levels set forth by the World Health Organization. Quantitative measurements based on computer image analysis had an error of 40 ± 20 µg I/L (n = 35 for samples in the calibration range) and these results categorized 88% of the samples (n = 60) correctly. We employed lifecycle analysis principles to address the known toxicity of arsenic, which is an obligatory reagent in the Sandell-Kolthoff reaction. Disposal of the cards in a landfill (their most likely destination after use) could let arsenic leach into groundwater; toxicity characteristic leaching procedure (TCLP) tests showed that the level of arsenic leached from the cards was 28.78 ppm, which is above the United States Environmental Protection Agency's limit of 5 parts per million for solid waste. We integrated a remediation module into the card. This module contains oxone, to oxidize As(III) to As(V) oxyacids, and the iron oxide goethite. TCLP testing showed that the leachable amount of arsenic was reduced by at least 97.6%-from 28.8 ppm to lower than 0.7 ± 0.7 ppm (n = 20). This upstream intervention rendered the test card suitable for landfilling while retaining its functionality to perform a critical public health evaluation.

saltPAD: A New Analytical Tool for Monitoring Salt Iodization in Low Resource Settings.

We created a paper test card that measures a common iodizing agent, iodate, in salt. To test the analytical metrics, usability, and robustness of the paper test card when it is used in low resource settings, the South African Medical Research Council and GroundWork performed independent validation studies of the device. The accuracy and precision metrics from both studies were comparable. In the SAMRC study, more than 90% of the test results (n=1704) were correctly classified as corresponding to adequately or inadequately iodized salt. The cards are suitable for market and household surveys to determine whether salt is adequately iodized. Further development of the cards will improve their utility for monitoring salt iodization during production.