Application of Nanoconfinement Technology for Highly Effective Monitoring of Chemical Exposure During Military Service.

INTRODUCTION: There is myriad of volatile compounds to which military personnel are exposed that can potentially have negative effects on their health. Military service occurs in a broad array of environments so it is difficult to predict the hazardous compounds to which the personnel might be exposed. XploSafe is developing passive diffusive samplers to facilitate the sampling and quantification of a wide range of chemical vapor exposures that personnel may be exposed to in the workplace. MATERIALS AND METHODS: Passive diffusive samplers were constructed by filling porous Teflon tubes with OSU-6, a nanoporous silica sorbent, to produce sampler tokens.  Three of these tokens were placed within a badge to fabricate passive samplers. Absorption experiments were performed to determine linear exposure regimes, sampling rates, and limits of quantification for 11 compounds, representing 8 chemical classes. RESULTS: The sampling rates were determined for 11 compounds representing 8 chemical classes. The measured linear ranges for the studied compounds are sufficiently large to allow effective sampling for 8 hours or longer. Accurate dosimetry is possible even with exposure times of days or weeks. The samplers were able to detect the presence of five airborne compounds in a paint booth of a military contractor located in Bristow, Oklahoma, and determine their average exposure concentrations. CONCLUSIONS: OSU-6 based sampler badges were able to detect the presence and quantify the average exposures of five airborne compounds in a paint booth of a military contractor located in Bristow, Oklahoma. Experiments show that these samplers can adsorb and quantify a broad array of different volatile organic compounds whose high sampling rates coupled with high capacity provide both sensitivity and the ability to quantify over a large range of exposures. This technology can meet the requirements for personal samplers to create Individual Longitudinal Exposure Record for each military person.

Superior Monitoring of Chemical Exposure Using Nanoconfinement Technology.

INTRODUCTION: Military personnel are exposed to a broad range of potentially toxic compounds that can affect their health. These hazards are unpredictable because military service occurs in a wide array of uncontrolled environments. Therefore, a novel sorbent was developed that allows the fabrication of lightweight personal samplers that are both capable of sorbing an extremely wide range of organic chemical types and able to stabilize reactive compounds. MATERIALS AND METHODS: OSU-6, a nanoporous silica, was provided by XploSafe LLC. The sorption capacity for several volatile organic compounds, the temperatures required for thermal desorption of adsorbed compounds, and the sampling rates for targeted analytes were determined. RESULTS: The uptake capacity was found to be on average 1.5 g/g of sorbent. Analytes were not only held tightly but also could be desorbed upon heating the sorbate to temperatures below 150°C. Sampling rates for volatile organic compound by an OSU-6 sampler badge were on average, 5.7 times higher than those for a commercially available activated carbon badge. Theoretical calculations showed that sorption of volatile organic compounds on the surface of the tightly curved pore walls in OSU-6 is because of exceptionally strong cumulative addition of Van der Waals forces. Analytes could readily be analyzed by either solvent extraction or thermal desorption gas chromatography/mass spectrometry techniques. Excellent sampling rates, high concentrations of analytes in the OSU-6 sorbent matrix, and high desorption efficiencies (recoveries) were obtained using the thermal desorption method. CONCLUSIONS: The performance of the OSU-6 sorbent makes it highly capable of meeting the need for personal samplers that enable Individual Longitudinal Exposure Records development. It can adsorb an extremely wide array of different volatile organic compounds, it can stabilize reactive compounds, it has high sampling rates coupled with high capacity that provide both sensitivity and resistance to saturation, and it is unique in being very amenable to thermal desorption in combination with having strong sorbate binding and high capacity and surface area.

Unexpected bond activation of small organic molecules on a metal oxide-butane/CaO(100).

We present the first example of bond activation of small alkanes (n-/iso-butane) on a metal oxide surface--CaO(100)--at ultra-high vacuum (UHV) conditions and at low surface temperatures studied by molecular beam scattering and thermal desorption spectroscopy.

Effect of surrounding point charges on the density functional calculations of NixOx clusters (x = 4-12).

Embedded Ni(x)O(x) clusters (x = 4-12) have been studied by the density-functional method using compensating point charges of variable magnitude to calculate the ionic charge, bulk modulus, and lattice binding energy. The computations were found to be strongly dependent on the value of the surrounding point charge array and an optimum value could be found by choosing the point charge to reproduce the experimentally observed Ni--O lattice parameter. This simple, empirical method yields a good match between computed and experimental data, and even small variation from the optimum point charge value produces significant deviation between computed and measured bulk physical parameters. The optimum point charge value depends on the cluster size, but in all cases is significantly less than +/-2.0, the formal oxidation state typically employed in cluster modeling of NiO bulk and surface properties. The electronic structure calculated with the optimized point charge magnitude is in general agreement with literature photoemission and XPS data and agrees with the presently accepted picture of the valence band as containing charge-transfer insulator characteristics. The orbital population near the Fermi level does not depend on the cluster size and is characterized by hybridized Ni 3d and O 2p orbitals with relative oxygen contribution of about 70%.