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L A Jonas

Publications and source records attributed to L A Jonas.

6 recordsLinked to original sources
PubMed1988

Effects of adsorbed water vapor on the adsorption rate constant and the kinetic adsorption capacity of the Wheeler kinetic model.

A recent trend in occupational safety and health has focused on the use of respiratory protective equipment to supplant engineering controls as the primary means of protecting workers from toxic substances. Respirator adsorbent cartridges have been demonstrated to have a finite capacity to adsorb toxic vapors. The knowledge of when this limit is approached or has been exceeded is crucial to the user. The Wheeler kinetic breakthrough model has been shown to describe accurately organic vapor penetration through beds of activated carbon. The model, however, does not account for competitive adsorption of water vapor or other organic vapors. The investigations reported here demonstrate the effect of adsorbed water vapor on the kinetic adsorption parameters (kinetic rate constant and kinetic saturation capacity) of the Wheeler equation. Adsorbent beds were equilibrated at varying concentrations of water vapor and then challenged with carbon tetrachloride vapor-laden air. Dry carbon had an initial rate constant of 62.5 s-1 and a kinetic adsorption capacity of 0.36 g of adsorbed CCl4/gram (g/g) of adsorbent. These parameters decreased in proportion to the amount of water vapor adsorbed, with the minimum predicted values occurring at 100% relative humidity. The minimum experimental value for the kinetic rate constant was 17.6 s-1, a decrease of 73% from the dry carbon values. The minimum predicted value for the kinetic adsorption capacity was 0.16 g/g, a decrease of 45%.

Adsorption↗
PubMed1986

Prediction of activated carbon performance for sequential adsorbates.

A packed bed of carbon granules was exposed to benzene and carbon tetrachloride sequentially to determine the adsorption characteristics of the bed under dynamic flow conditions. We found that the total adsorption space of the carbon was invariant at a fixed relative pressure and temperature. This finding allowed us to predict carbon performance for adsorbates introduced concurrently and/or sequentially.

Adsorption↗
PubMed1985

The effect of moisture on the adsorption of chloroform by activated carbon.

The effect of moisture on the ability of a granular activated carbon to adsorb chloroform vapor from a flowing airstream was studied under three test conditions: (1) chloroform and water vapor were introduced concurrently into a dry carbon bed; (2) dry chloroform was introduced into a humidified carbon bed; (3) humidified chloroform was introduced into a carbon bed at the same relative humidity. The criterion for bed performance was the time when the downstream chloroform concentration was 1% of that in the inlet stream. Chloroform concentration was essentially constant at 108 +/- 2 micrograms/cm3; relative humidities (RH) varied from 0 to 97%. No RH effect on the adsorption of chloroform by the carbon was observed in test (1); tests (2) and (3) showed monotonic decreases in chloroform adsorption for RH greater than 40%. These results indicated that, for a dry carbon bed, the 1% breakthrough time for chloroform adsorbed from atmospheres of RH from 13% to 95% was essentially the same as that when RH = 0%. For humidified carbon beds, no change in 1% breakthrough time for chloroform was observed until RH was greater than 40%.

Adsorption↗
PubMedDate not supplied

Brain uptake of flurazepam and of N1-desalkyl flurazepam after administration of flurazepam to the cat.

A gas chromatographic-mass spectrometric procedure was employed to identify flurazepam and several of its metabolites in the plasma, cerebrospinal fluid (CSF), and brain of cats after an iv injection of flurazepam. Following tissue redistribution, flurazepam was lost from plasma with a mean half-time of 1.4 hr; although usually not detectable in plasma by 24 hr, significant quantities were found in the brain at this time, particularly in the corpus callosum. N1-Hydroxyethyl flurazepam appeared rapidly in plasma following iv flurazepam, peaked at about 40 min, and then declined with a mean half-time of 2.1 hr. N1-Desalkyl flurazepam accumulated in plasma in the first 6 hr after flurazepam was injected, and then declined slowly with a mean half-time of about 50 hr. At 24 hr, corpus callosum concentrations of the N1-desalkyl flurazepam exceeded those of flurazepam by 16- to 63-fold and produced brain/plasma ratios of 6 to 62 in three cats. CSF concentrations of flurazepam and N1-desalkyl flurazepam did not reflect brain concentrations but only the estimated plasma fractions of the unbound drugs. The results suggest that long term central effects of iv flurazepam are mediated to a large extent by the N1-desalkyl flurazepam, in species in which that metabolite accumulates.

Animals↗