Validation of Analytical Method for Determination of Thallium in Rodent Plasma and Tissues by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).

Thallium (Tl) can be released as a byproduct of smelting, mining, and other industries, causing human exposure. There are knowledge gaps on the toxicity of thallium compounds, so the National Toxicology Program is investigating the toxicity of thallium (I) sulfate in rodents. We developed and validated a method to quantitate Tl in rodent plasma and secondary matrices. Primary matrix standards and validation samples were digested with nitric acid and analyzed for Tl by inductively-coupled plasma - mass spectrometry (ICP-MS). Method performance was validated for linearity, accuracy, precision, and other criteria. Calibration was linear from 1.25 to 500 ng Tl/mL plasma; accuracy (RE) was -5.9 to 2.6% for all calibration standards. The lower limit of quantitation (LLOQ) was 1.25 ng Tl/mL plasma, and the limit of detection was 0.0370 ng Tl/mL plasma. Intra- and interday RE and precision (RSD) were -5.6 to -1.7% and ≤0.8% (intraday) and -4.8 to -1.3% and ≤4.3% (interday), respectively, at three sample concentration levels. Standards up to 10.0 × 103 ng/mL could be analyzed by dilution with digested blank matrix, with -6.4% RE and 5.4% RSD. Method was also evaluated in post-natal day 4 (PND4) Hsd:Sprague Dawley SD (HSD) dam and pup plasma, gestation day 18 (GD 18) HSD rat fetal homogenate, HSD rat urine, female HSD rat brain homogenate, female B6C3F1 mouse plasma. Background Tl was detected in control fetal and brain homogenates and urine at < 30% of LLOQ response. Results demonstrate that the method is suitable for determination of Tl in rodent matrices for toxicology studies.

Mechanisms of orthophosphate removal from water by lanthanum carbonate and other lanthanum-containing materials.

Removing phosphorus (P) from water and wastewater is essential for preventing eutrophication and protecting environmental quality. Lanthanum [La(III)]-containing materials can effectively and selectively remove orthophosphate (PO4) from aqueous systems, but there remains a need to better understand the underlying mechanism of PO4 removal. Our objectives were to 1) identify the mechanism of PO4 removal by La-containing materials and 2) evaluate the ability of a new material, La2(CO3)3(s), to remove PO4 from different aqueous matrices, including municipal wastewater. We determined the dominant mechanism of PO4 removal by comparing geochemical simulations with equilibrium data from batch experiments and analyzing reaction products by X-ray diffraction and scanning transmission electron microscopy with energy dispersive spectroscopy. Geochemical simulations of aqueous systems containing PO4 and La-containing materials predicted that PO4 removal occurs via precipitation of poorly soluble LaPO4(s). Results from batch experiments agreed with those obtained from geochemical simulations, and mineralogical characterization of the reaction products were consistent with PO4 removal occurring primarily by precipitation of LaPO4(s). Between pH 1.5 and 12.9, La2(CO3)3(s) selectively removed PO4 over other anions from different aqueous matrices, including treated wastewater. However, the rate of PO4 removal decreased with increasing solution pH. In comparison to other solids, such as La(OH)3(s), La2(CO3)3(s) exhibits a relatively low solubility, particularly under slightly acidic conditions. Consequently, release of La3+ into the environment can be minimized when La2(CO3)3(s) is deployed for PO4 sequestration.

Development of an analytical method for assessment of silver nanoparticle content in biological matrices by inductively coupled plasma mass spectrometry.

Silver nanoparticles (AgNPs) are a broad class of synthetic nanoparticles that are utilized in a wide variety of consumer products as antimicrobial agents. Despite their widespread use, a detailed understanding of their toxicological characteristics and biological and environmental hazards is not available. To support research into the biodistribution and toxicology of AgNPs, it is necessary to develop a suitable method for the assessment of AgNP content in biological samples. Two methods were developed and validated to analyze citrate-coated AgNP content that utilize acid digestion of rodent feces and liver tissue samples, and a third method was developed for the dilution and direct analysis of rodent urine samples. Following sample preparation, the silver content of each sample was determined by inductively coupled plasma mass spectrometry (ICP-MS) to quantify the silver and AgNP levels present. Analysis of rat feces matrix yielded analytical recoveries ranging from 82 to 93 %. Liver tissue spiked with a formulation of AgNPs over a range of concentrations yielded analytical recoveries between 88 and 90 %, providing acceptable accuracy results. The analysis of silver in urine samples exhibited recovery values ranging from 80 to 85 % for AgNP formulations and 62-84 % for standard silver ion solutions. All determinations exhibited a high degree of analytical precision. The results obtained here suggest that matrix interference plays a minimal role in AgNP recovery in feces and liver tissue, while the urine matrix can exhibit a significant effect on the determination of silver content.