Testing toluene contamination

Before injection into the GC system, a clean-up of the sample extract is necessary, since lipophile compounds, which also are extracted into benzene or toluene, contaminate the system. Westoo (1967 and 1968) used a clean-up procedure consisting of an intermediate extraction of MeHg into an aqueous cysteine solution. The applicability of the Westoo methods on fish samples was carefully tested and confirmed by Kamps and McMahon (1972). 

Hui et al. [29] conducted toluene contamination tests at different toluene concentrations. They also studied the effects of different operational conditions on toluene contamination, including the effects of fuel cell relative humidity (RH), of Pt loading in the cathode catalyst layer, of back pressure, and of air stoichiometry [30]. Figure 3.8 shows a set of representative results of contamination tests at 1.0 A cm with various levels of toluene concentration in the air. It can be seen that the cell voltage starts to decline immediately after the introduction of toluene, and then reaches a plateau (steady state). These plateau voltages indicate the saturated nature of the toluene contamination. For example, the cell voltage drops from 0.645 V to 0.522 V at 1.0 A cm-2 within 30 min of the cathode... 

Semiempirical Model for Fuel Cell Performance in the Presence of Toluene In the presence of toluene in the air stream, the fuel cell performance degraded. Figure 3.15 illustrates two sets of representative results of toluene contamination tests, conducted with various levels of toluene concentration at current densities of 0.75 and 1.0 A cm , respectively. The cell voltage experienced a transient period (nonsteady state) immediately after the introduction of toluene, then reached a plateau (steady state). The duration of the transient period and the magnitude of the cell voltage drop to the plateau were strongly dependent on toluene concentration and current density. 

Prediction of the Steady-State Polarization Curves Figure 3.18 shows the predicted and experimentally tested polarization curves for the test cell across the full range of toluene concentrations encompassed by the model. The top curve (solid black) is the baseline polarization curve (i.e., no toluene contamination). Curves below that indicate decreasing performance as the toluene concentration increases. 

A semiempirical model that considered only the effect of toluene on kinetics was constructed to describe cell voltage as a fimction of contamination time and current density. The parameters independent of the contamination process, i.e., open circuit voltage (E°), cell resistance (RJ, and Tafel slope (fc), were first estimated based on experimental data in the absence of toluene (giving a baseline). Then these parameters were used to empirically obtain the expressions of two other parameters, and Kcbc/ which accoimted for the effect of toluene contamination on transient and steady-state cell performance, using experimental data at various levels of toluene concentration imder four current densities. The model was validated by comparing the contamination testing results with model-predicted results. Several other definitions were also presented, based on the model, such as the threshold toluene concentration and the degradation rate. 

FIGURE 8.15 Contribution of individual resistance increases relative to the total resistance increase at different current densities for toluene contamination. Cell temperature = 80°C, Relative humidity = 80%, 30 psi back pressure, stoichiometry 1.5/3.0for Hj/air. (Reprinted from lournal of Power SourceSy 185, Li, H. etal. Polymer electrolyte membrane fuel cell contamination Testing and diagnosis of toluene-induced cathode degradation, 272 279, Copyright (2008), with permission from Elsevier.)... 

Field Tests. Recently we conducted a field test at a site contaminated with fuel oil. Our measurements were 0.0625 0.0212 mA for the well water and 0.0189 0.0119 mA for distilled water (showing errors of one standard deviation). From calibration curves, these numbers can be reported as equivalent to 50 ppb phenol or 34 ppb xylenes. Nine-month-old laboratory results (EPA method 624 and GC/FID) for this site indicated concentrations of 25 ppb for benzene, toluene, and xylenes combined and 100 ppb for fuel oil. The important result is the significant difference between the distilled-water and well-water measurements. We are very encouraged by these results and are planning future field tests. 

Optimal Salinities Phase inversions at optimal salinity were assessed routinely by salt titrations into systems maintained at constant temperature. For the Leonox IOS surfactant system, increasing levels of salinity were necessary to cause the emulsion state to phase invert as the alkane molecular weight increased (Figure 11). Ihe initial conductivity value at the condition where zero salt had been added may in part reflect the salt contamination naturally present within the supplied formulation. Ihe internal olefin sulphonate species again revealed a linear relationship between EACN and optimal salinity as did all ionic formulations under test (see Figures 12 and 13, plus Table III). Ihe estimation of EACN values for both toluene... 

Willardson BM, Wilkins JF, Rand TA, Schupp JM, Hill KK, Keim P, Jackson PJ (1998) Development and testing of a bacterial biosensor for toluene-based environmental contaminants. Appl Environ Microbiol 64 1006-1012... 

To determine the concentrations of benzene, toluene, ethylbenzene, and xylenes, approved methods (e.g., EPA SW-846 8021B, SW-846 8260) are not only recommended but are insisted upon for regulatory issues. Polynuclear aromatic hydrocarbons (PAHs) may be present in condensate, and evaluation of condensate contamination should include the use of other test methods (EPA SW-846 8270, SW-846 8310) provided that the detection limits are adequate to the task of soil and groundwater protection. Generally, at least one analysis may be required for the most contaminated sample location from each source area. Condensate releases in nonsensitive areas require analysis for naphthalene only. The analysts should ensure that the method has detection limits that are appropriate for risk determinations. 

Specific contaminants that are components of total petroleum hydrocarbons, such as BTEX (benzene, toluene, ethylbenzene, and xylene), n-hexane, jet fuels, fuel oils, and mineral-based crankcase oil have been studied and a number of toxicological profiles have been developed on individual constituents and petroleum products. However, the character of the total petroleum hydrocarbons has not been studied extensively and no profiles have been developed. Although several toxicological profiles have been developed for petroleum products and for specific chemicals found in petroleum, the total petroleum hydrocarbon test results have been too nonspecific to be of real value in the assessment of its potential health effects. 

Thomas and Delfino (1991) equilibrated contaminant-free groundwater collected from Gainesville, FL with individual fractions of three individual petroleum products at 24-25 °C for 24 h. The aqueous phase was analyzed for organic compounds via U.S. EPA approved test method 602. Average toluene concentrations reported in water-soluble fractions of unleaded gasoline, kerosene, and diesel fuel were 23.676, 1.065, and 0.552 mg/L, respectively. When the authors analyzed the aqueous-phase via U.S. EPA approved test method 610, average toluene concentrations in water-soluble fractions of unleaded gasoline, kerosene, and diesel fuel were lower, i.e., 12.969, 0.448, and 0.030 mg/L, respectively. 

Anaerobic conditions often develop in hydrocarbon-contaminated subsurface sites due to rapid aerobic biodegradation rates and limited supply of oxygen. In the absence of O, oxidized forms or natural organic materials, such as humic substances, are used by microorganisms as electron acceptors. Because many sites polluted by petroleum hydrocarbons are depleted of oxygen, alternative degradation pathways under anaerobic conditions tend to develop. Cervantes et al. (2001) tested the possibility of microbially mediated mineralization of toluene by quinones and humus as terminal electron acceptors. Anaerobic microbial oxidation of toluene to CO, coupled to humus respiration, was demonstrated by use of enriched anaerobic sediments (e.g., from the Amsterdam petroleum harbor). Natural humic acids and... 

In testing, this technology was effective in treating waste streams contaminated with benzene, toluene, ethylbenzene, and xylenes (BTEX compounds). The technology is not in use at present and is not commercially available. 

HCZyme has been demonstrated in bench-scale tests and at field remediations to be effective on benzene, toluene, ethylene, and xylene (BTEX), Polycyclic aromatic hydrocarbons (PAHs), trichloroethylene (TCE), dichloroethylene (DCE), mineral spirits, fuel oils, motor oils, and hydraulic fluids. The vendor claims that HCZyme has been tested and used on over 2 million tons of petroleum-contaminated soils and is effective in breaking down petroleum hydrocarbons, polychlorinated biphenyls (PCBs), creosote, sludges, waste oils, free product, tank bottoms, and other chlorinated compounds (D18208L, p. 15). 

In case the hexaphenylbenzene is contaminated with insoluble material, crystallization from a filtered solution can be accomplished as follows Place 10 mL of diphenyl ether in a 25 x 150-mm test tube and pack the sample of hexaphenylbenzene into a 10-mm extraction thimble and suspend this in the test tube with two nichrome wires, as shown in Fig. 1. Insert a cold finger condenser supported by a filter adapter and adjust the condenser and the wires so that condensing liquid will drop into the thimble. Let the diphenyl ether reflux until the hexaphenylbenzene in the thimble is dissolved, and then let the product crystallize, add toluene, collect the product, and wash with toluene as described previously. 

Another substrate hydrolyzed by thermal polyanhydroamino acids is p-nitrophenyl phosphate (NPP). Oshima 25) has tested acidic proteinoids, a histidine-rich proteinoid, and proteinoids that contain a relatively high proportion of basic and neutral amino acids (p. 377). These polymers were fractionated in water and aqueous alkali, and by molecular sieve chromatography. Soluble fractions were used in most experiments on catalysis. The possibility of microbial contamination was obviated indirectly by virtue of several circumstances. These included using fractions with molecular weights between 2500 and 4000, and adding toluene to the test reaction mixtures. The reactions were carried out at 30° in 0.03 M tris buffer, pH 7.6, in the presence of 1 pmole/ml of NPP and 0.03-1.5 mg/ml of thermal polymer pM ZnCU and IQfiM MgCl2 were also present in the solutions. Truly catalytic... 

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