The effect of an alternate environment as a collection medium on the permeation characteristics of solid organics through protective glove materials.

With a method developed for the determination of permeation characteristics of glove materials by organic solids, a study of the effect of a saline environment on permeation characteristics such as breakthrough and steady state permeation was performed at ambient temperature. The study uses saline as a collection medium and a stainless steel permeation cell designed exclusively for solids. The system allows for materials of five commercially available gloves to be exposed to nine organic solids. Natural rubber latex yielded the shortest and nitrile the longest breakthrough times. Overall, breakthrough times were comparable to a method using a helium collection medium, but in many exposures the saline-based collection medium yielded longer breakthrough times, 2% to 894%. In the testing involving the saline collection medium, results showed that the polarity of the glove material may be a factor that reduces measured permeation rate.

Protective glove material permeation by organic solids.

A method has been developed for the determination of permeation characteristics of glove materials by organic solids. The system employs a stainless steel exposure cell and allows rapid and uniform contact of either solid disks or powders with minimal membrane bowing. A gas chromatograph equipped with a flame ionization detector was used for monitoring the permeation process, which provided detection limits of 0.9-1.2 ng for the organic solids evaluated. By using an automated system for instrument control and data collection, breakthrough times, steady-state times, and steady-state permeation rates have been determined for five common glove materials when exposed to nine organic solids.

The representation and integration in memory of spatial and nonspatial information.

A series of experiments investigated whether people could integrate nonspatial information about an object with their knowledge of the object's location in space. In Experiments 1 and 3, subjects learned the locations of cities on a fictitious road map; in Experiments 2, 4, and 5, subjects were already familiar with the locations of buildings on a campus. The subjects then learned facts about the cities on the maps or the buildings on the campus. The question of interest was whether or not these nonspatial facts would be integrated in memory with the spatial knowledge. After learning the facts, subjects were given a location-judgment test in which they had to decide whether an object was in one region of the space or another. Knowledge integration was assessed by comparing levels of performance in two conditions: (a) when a city or a building name was primed by a fact about a neighboring city or building, and (b) when a city or a building name was primed by a fact about a distant city or building. Results showed that responses in Condition a were faster or more accurate, or both faster and more accurate, than responses in Condition b. These results indicate that the spatial and nonspatial information were encoded in a common memory representation.

Spatial and temporal contributions to the structure of spatial memory.

Three experiments investigated the effects of spatial and temporal contiguity in item recognition, location judgment, and distance estimation tasks. Ss learned the locations of object names in spatial arrays, which were divided into 2 regions. The names of locations were presented during map learning so that critical pairs appeared close in space and close in time, close in space but far in time, far in space but close in time, and far in space and far in time. Names primed each other in recognition only when they were neighbors in both space and time. In contrast, the effects of spatial and temporal contiguity in priming in location judgments were additive. Finally, temporal contiguity affected estimates of Euclidean distance when locations were close together, but not when they were far apart.

Permeation-solid adsorbent sampling and GC analysis of formaldehyde.

A passive method with membrane permeation sampling for the determination of time-weighted-average (TWA) concentration of formaldehyde in air is described. The sampling device was constructed by affixing an unbacked dimethyl silicone membrane to the base of a glass tube and by sealing the top with a rubber stopper. Formaldehyde permeates the membrane and reacts with 2-(hydroxymethyl)piperidine (2-HMP) coated on the surface of XAD-2. Sampling times from 15 min to 8 hr have been used. The formaldehyde-oxazolidine produced is thermally desorbed and determined by a packed column gas chromatograph equipped with a flame ionization detector (FID). The response of the monitor is directly proportional to the external concentration of formaldehyde over the concentration range 0.050-100 ppm. The permeation constant (the slope of the permeation curve) of the membrane is 0.333 mug ppm(-1). hr, and the detection limit of the method is 0.03 ppm for an 8-hr sampling period. Relative humidity (RH) (35-94%), temperature (0-82 degrees ) and storage period (0-25 days) do not affect the permeation process for sample collection. Moreover, potential chemical interferences, 10 ppm acetone or acrolein, respectively, have no detectable effect on the process. The method gives TWA concentration directly from the measurements, and the equipment is economical and convenient for personal or multi-location sample collections.

A multiple mass spectral line method for determining positional specific activities in stable isotope-labeled amino acids.

A method for determining the position and enrichment of isotope labels in amino acids using gas chromatography/mass spectrometry is described. [alpha-15N]- and [epsilon-15N]lysine, [1-13C]- and [15N]alanine and -leucine, and [1-13C]-, [2-13C]-, [3-13C]-, and [4-13C]aspartic acid were investigated. Standards for each isotope label were prepared and analyzed under scan conditions, and line pairs characteristic for the label were identified. The standards were reanalyzed under selective ion monitoring conditions to verify the behavior of the line pairs. Mixtures of amino acids containing different isotope labels or the same label in different positions were prepared and analyzed under selective ion monitoring conditions. Enrichments were determined with high precision and relative errors ranging from 0.14 to 36%.

Method for the determination of the priority pollutant metals by HPLC.

The United States Environmental Protection Agency (EPA) currently specifies atomic absorption spectrophotometry as the method of analysis for the priority pollutant metals. While the method is very sensitive, it does suffer from limitations. As an alternative, the use of dibenzyldithiocarbamate (DBDC) to complex the priority pollutant metals from the sample, with subsequent separation of the complexes by liquid chromatography and quantification by ultraviolet-visible spectrophotometry, is reported. Of the thirteen priority pollutant metals, ten can be determined with the method (Cd, Cu, Cr, Hg, Ni, Pb, Sb, Se, Tl, and Zn). Of the remaining priority pollutant metals, beryllium was not investigated, while silver and arsenic did not form complexes with DBDC. In addition, one potential interference, manganese, can be determined. Cobalt is added as an internal standard. Separation of the complexes on a C18 column is achieved with a quaternary solvent system consisting of 64% methanol, 12% acetonitrile, 5% tetrahydrofuran, and 19% pH 5 acetate buffer. Detection limits range from a low of 0.1 ppb (ng/mL) for selenium to a high of 1.8 ppb for thallium.

The use of multiple mass spectral line pairs for enhanced precision in isotope enrichment studies of 15N-labeled amino acids.

A method for enhancing the precision in the calculation of isotope enrichment for 15N-labeled amino acids is presented. The method utilizes multiple line pairs for the calculation of isotope enrichment. Using multiple line pairs allows the evaluation of calibration curves for nonlinear behavior and permits differentiation among sites containing more than one labeled nitrogen. The increase in precision is related to the number of isotopically shifted line pairs used in calculating the isotopic enrichment and varies with the amino acid of interest.

Subjective hierarchies in spatial memory.

Two experiments investigated the structure of spatial memories. Subjects learned locations of objects in spatial layouts (Experiment 1) or locations of object names on maps (Experiment 2). Physical and perceptual boundaries were absent in these spatial arrays. Subjects then participated in three tasks: item recognition, in which the variable of interest was spatial priming; free and cued recall; and Euclidean distance estimation. Ordered-tree analysis of individual subjects' recall protocols produced hierarchical trees consistent with regularities in output order. Spatial priming and distance estimations depended on whether pairs of objects appeared in the same subtree or in different subtrees. These findings indicate that spatial memories have a hierarchical component, even when physical and perceptual boundaries are nonexistent. Priming also increased with depth of clustering in ordered trees. This result supports spreading-activation theories of retrieval but provides evidence against several "non-spreading-activation" theories.

Method for the evaluation of the permeation characteristics of protective glove materials.

A method is described to evaluate the permeation characteristics of glove materials by chemical solvents. The collecting medium (helium) is continuously monitored by a flame ionization detector (FID) of a gas chromatograph (GC). Immediately following a steady-state condition, quantitative data are acquired on-line by a computer. A two-position GC sampling valve and computer-controlled data acquisition and analysis require minimal operator attention. For the 8 materials and 6 solvents investigated, thickness-normalized breakthrough times and steady-state permeation rates ranged from 9.10 min/mil to greater than 4 hr/mil and from 0.2048 to 9112 micrograms/min/cm2/mil, respectively. A modification of the procedure which allowed the determination of the effect of temperature on permeation for 4 glove/solvent pairs was evaluated also.