Chamber concentrations

HR-ICP-MS EEEMENT-2 (Pinnigan MAT, Germany) equipped with a standard introduction system (quartz water-cooled spray chamber, concentric nebulizer, torch with 1.5 mm i.d. injector and nickel cones) was used for measurements. The following operating conditions were used RP power 1150 W, coolant gas flow rate 16 1 min k auxiliary gas flow rate 0.85 1 min nebulizer gas flow rate 1.2 1 min k Sample uptake rate was 0.8-1 ml min k Measurements were performed with low and middle resolutions. Rh was used as an internal standard. Por calibration working standard solutions were prepared by diluting the multielemental stock solutions CPMS (SPEX, USA) with water to concentration range from 5 ng to 5 p.g I k... 

Figure 1. Dependence of relative ion concentrations upon the ionization chamber concentration of CH OH...

CHzOD2 + /CHzOHD + for CHaOD and R = CD,OH2 +/-CDzOHD + for CD OH, upon the ionization chamber concentration of methanol... 

Figure 3. Variation of the relative primary, secondary, and tertiary ion currents with ionization chamber concentration as predicted by the kinematic theory for the three models of complex formation, hydrogen ion, and hydrogen atom stripping. For conditions, see text...

Figure 5. Comparison between the experimental variations of R, the ratio CH3OD2 V CHjOHD +, with ionization chamber concentration of CHsOD and theoretical predictions of the kinematic theory for assumed velocity-independent rate constants of the reaction CtUOH2 + + CH5OH - CH3OH + CH3OH2+ for both the complex-formation and proton-stripping mechanisms...

Frosolono and Currie (1985) investigated the effect of phosgene on the pulmonary surfactant-system (PSS) in groups of six to 14 rats exposed to phosgene at 1 ppm for 4 h. The exposure system and parameters were similar to those described in Section 3.2.1 (Hatch et al. 1986). The actual chamber concentration was 1.0 0.06 ppm. Animals were sacrificed immediately after exposure, or on postexposure days 1, 2, or 3. Pulmonary edema was present immediately after exposure and persisted through day 3. Phosphatidylinositol levels were significantly (p<0.05) decreased compared with controls immediately after exposure only. Phosphatidylserine and phosphatidylethanolamine levels were significantly increased compared with controls on days 1, 2, and 3 postexposure. Phosphatidylcholine levels were increased at all time points compared with controls. 

In a 90-d study with a 4-wk interim sacrifice, groups of 15 male and 15 female Fischer 344 rats were exposed at 0, 2,000, 8,000, or 20,000 ppm for 6 h/d, 5 d/wk in a 4 m3 stainless steel and glass chamber (Brock et al. 1995). Chamber concentrations were measured by infrared spectrometry. The animals were examined daily, and body weights and food consumption were measured weekly. Prior to sacrifice, blood and urine samples were collected. At the end of 4 wk, five rats per gender per group were sacrificed, and organs... 

In an undated study, HCFC-141b was administered to male SpragueDawley rats at concentrations of 5,000, 10,000, or 20,000 ppm for 30 min (Eger, unpublished data). As exposure continued, bolus intravenous epinephrine, characterized as three times the dose that produced arrhythmias in the same rats anesthetized with halothane, was administered. The dose of epinephrine was defined as a maximum of 12 fig/kg. For this study, three or more premature ventricular contractions was considered an arrhythmic response (Table 4—5). Marked arrhythmias occurred at all concentrations. The author further compared the concentrations of halothane and HCFC-141b that produced arrhythmias with administration of various doses of exogenous epinephrine. The nominal chamber concentration for HCFC-141b did not differ from that of halothane. Furthermore, the arrhythmias were characterized as relatively mild and within acceptable limits for surgical anesthesia in humans. 

The development of efficient combustion systems with reduced emissions can be brought about by having a clear understanding of the fuel air mixing ratios in the combustion chamber. Concentration distributions of the liquid and vapour phases of the fuel can be imaged by... 

HilF reported pollutant uptake values for a number of gaseous pollutants, including ozone and PAN, with alfalfa as his test organism (Table 11-26). These values were obtained with a dynamic, but closed, exposure facility. Uptake was determined by the amount of pollutant needed to maintain a constant chamber concentration over an alfalfa bed. Uptake values, expressed on the basis of leaf area, reflect the effect of the plant canopy on the exchange of gases within the canopy and do not... 

Takada, et. al. (7), compared the 3M Organic Vapor Monitor to charcoal tubes by studying the weight of contaminant collected as a function of (1) exposure time at various concentrations and (2) chamber concentration at various exposure times. Their data is summarized in Figures 1,2,3,4. Their study led to the following major conclusions ... 

Figure 3. Relationship between weight of toluene collected by the 3M Organic Vapor Monitor and the chamber concentration...

Figure 4.10 Chamber concentration/time profiles for four kinds of dry building materials At the beginning of the test, a dose of formaldehyde was injected into the chamber air, the measurement stopped when the chamber formaldehyde concentration hardly changed (Zhang et al., 2007a).

Table 15.3 VOC emissions from a school book with PVC cover. Chamber concentrations in a 23.51 chamber 24h after loading (T = 23°C, r.h. = 45%, N = 1.0lr ).

These results demonstrated that books and journals may release significant amounts of VOCs and must be regarded as typical point sources that are located close to occupants (Salthammer, 1999). Consequently, chamber concentrations are presented instead of unit specific emission rates. 

The duration of exposure to the chemical should be at least 4 hours after the attainment of equilibrium of the chamber concentration. Other durations may be needed to meet specific requirements. If during a test at an exposure concentration of 5 mg/L (actual concentration of respirable chemical) for 4 hours (or where this is not possible due to physical or chemical properties of the test chemical), the maximum attainable concentration using the procedures described for this study produces no compound-related mortality, a full study using three dose levels may not be necessary. 

The subchronic inhalation toxicity should be studied with at least three concentrations of the test chemical with a control (and where appropriate, a vehicle control corresponding to the concentration of the vehicle at the highest exposure level). The remaining details of exposure are similar to those described for acute oral and acute inhalation toxicity. The duration of daily exposure should be 6 hours after equilibrium of the chamber concentrations. Other durations may be used to meet specific requirements. 

Long-term respiratory exposures are usually patterned to projected industrial experience, giving the animal a daily exposure 6 hours after equilibrium of chamber concentrations, for 5 days a week (intermittent exposure) or 22 to 24 hours of environmental exposure per day, 7 days a week (continuous exposure), with 1 hour for feeding and maintaining the chambers. In both the cases, the animals are usually exposed to a fixed concentration of test materials. A major difference to consider between intermittent and continuous exposure is that in the former there is a period of 17 to 18 hours in which animals may recover from the effects of daily exposure, and an even longer recovery period during weekends. 

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