Air sample analysis

Busch, K. A., "Statistical Properties of the SRI Contract Protocol (CDC 99-74-45) for Estimation of Total Errors of Air Sampling/Analysis Procedures", memorandum to Deputy Director, Division of Laboratories and Criteria Development, Jan. 6, 1975. 

Packed column technology has been used in airborne gas chromatographs for the separation and quantitation of sulfur species (46, 47) and peroxyacetic nitric anhydride (48). The combination of sample preconcentration and sensitive detectors has yielded detection limits that are superior to corresponding continuous sensors. For S02, a detection limit of 25 pptrv was claimed, and for peroxyacetic nitric anhydride the detection limit was roughly 60 pptrv for an 50-cm3 air sample. Analysis times for samples were on the order of 10 min. 

Particles are defined as aerosols (dust) when they are smaller than about 200 pm and larger than 0.01 pm. Smaller particles have the characteristics of a gas, and larger particles are too heavy to stay suspended and will not be inhaled. Inhalable particles which can reach the pharynx have a maximum size of 200 pm, particulate matter which is smaller than 10 pm can reach the larynx and the thorax, and respirable particles can go as far as the alveoh in the lungs (e.g. asbestos fibres) [47]. Particles with a diameter between 2 and 5 pm can precipitate in the alveoh even smaller particles are exhaled again. Air sample analysis indicates that up to 99% (by count) of particles present in the atmosphere are 1 pm or less in size [48]. 

Air sample analysis Glass impingers are used to obtain air samples. A separate bubbler is carried through all the steps except the actual air sampling in order to act as a blank. To each bubbler, 0-5 ml of 3% sodium nitrite solution is added and allowed to stand for about 90s. 1 ml of 10% sulphamic acid solution is added, mixed and allowed to stand for about 2 min to destroy all the excess nitrous acid present. 1ml of 0-1% N-naphthylethylene diamine is added, mixed and the colour allowed to develop for about 5 min. A reddish blue colour indicates the presence of TDI. The final volume is adjusted to 20 ml with water. The transmittance is read at 550 nm using a 1-cm or 5-cm cuvet. The sample absorbance, after allowing for the absorbance of the blank, is compared with the calibration curve, and the concentration of TDI in ppm is calculated as above. 

J. P. Lodge, ed.. Methods of Air Sampling and Analysis, Lewis PubUshers, Chelsea, Mich., 1989, 763 pp. 

Health and Safety. Remover formulas that are nonflammable may be used in any area that provides adequate ventilation. Most manufacturers recommend a use environment of 50—100 parts per million (ppm) time weighted average (TWA). The environment can be monitored with passive detection badges or by active air sampling and charcoal absorption tube analysis. The vapor of methylene chloride produces hydrogen chloride and phosgene gas when burned. Methylene chloride-type removers should not be used in the presence of an open flame or other heat sources such as kerosene heaters (8). 

Health and Safety. Petroleum and oxygenate formulas are either flammable or combustible. Flammables must be used in facUities that meet requirements for ha2ardous locations. Soak tanks and other equipment used in the removing process must meet Occupational Safety and Health Administration (OSHA) standards for use with flammable Hquids. Adequate ventilation that meets the exposure level for the major ingredient must be attained. The work environment can be monitored by active air sampling and analysis of charcoal tubes. 

A method suitable for analysis of sulfur dioxide in ambient air and sensitive to 0.003—5 ppm involves aspirating a measured air sample through a solution of potassium or sodium tetrachloromercurate, with the resultant formation of a dichlorosulfitomercurate. Ethylenediaminetetraacetic acid (EDTA) disodium salt is added to this solution to complex heavy metals which can interfere by oxidation of the sulfur dioxide. The sample is also treated with 0.6 wt % sulfamic acid to destroy any nitrite anions. Then the sample is treated with formaldehyde and specially purified acid-bleached rosaniline containing phosphoric acid to control pH. This reacts with the dichlorosulfitomercurate to form an intensely colored rosaniline—methanesulfonic acid. The pH of the solution is adjusted to 1.6 0.1 with phosphoric acid, and the absorbance is read spectrophotometricaHy at 548 nm (273). 

Determination of benzene in air samples has been achieved by bubbling contaminated air through various solvents, followed by uv or in analysis of the solution (90). Methods for identifying benzene in soil, water, and biological media are further described in references 84 and 85. 

The methods that have been discussed require specially designed instruments. Laboratories without such instruments can measure these gases using general-purpose chemical analytical equipment. A compendium of methods for these laboratories is the "Manual on Methods of Air Sampling and Analysis"published by the American Public Health Association. (10). 

Analytical methods available to labbratories with only general-purpose analytical equipment may be found in the "Methods of Air Sampling and Analysis" cited at the end of the previous section. 

Samples of particulate matter can be subjected to many of the above analytical techniques in chemical characterization. The following methods are, however, particularly applicable to analysis of physical characteristics of particulate matter isolated from air sampling. 

The minimum air sample (litres) that will provide enough of the substance for the most accurate analysis at the TLV concentrations using the analytical procedures listed. 

A bulk sample is the last choice and the least desirable. It should be submitted "for laboratory use only" if there is a possibility of contamination by other matter. The type of bulk sample submitted to the laboratory should be cross-referenced to the appropriate air samples. A reported bulk sample analysis for quartz (or cristobalite) will be semi-quantitative in nature because (1) The XRD analysis procedure requires a thin layer deposition for an accurate analysis. (2) The error for bulk samples analyzed by XRD is unknown because the particle size of nonrespirable bulk samples varies from sample to sample. 

Integrated Sampling Device an air sampling device that allows estimation of air quality components over a period of time (e.g., two weeks) through laboratory analysis of the sampler s medium. 

The contractor at Site H had established area and personnel sampling consistent with HAZWOPER requirements. A photo ionization detector (PID) and a real-time aerosol monitor (RAM) were used on a daily basis to screen for potentially hazardous levels of contaminants. On a weekly basis, personal air samples were collected and submitted for laboratory analysis. PPE requirements, however, were often not based on this data because the oversight agency had established inflexible minimum PPE requirements. The audit team found many of the PPE requirements on Site H to be excessive in light of site monitoring data and hazard determinations. 

High-volume sampler A device used for extracting particulates from the air for analysis that requires a shorter. sampling period than a low-volume sampler. 

Figure 13,12 Illusti ation of the clean-up method, showing the analysis of an air sample (a) with and (b) without column switching. Details of the analytical conditions are given in the text. Reprinted from Journal of Chromatography, A 697, R R. Kootsti a and H. A. Herbold, Automated solid-phase exti action and coupled-column reversed-phase liquid cltromatogra-phy for the trace-level determination of low-molecular-mass carbonyl compounds in ak , pp. 203-211, copyright 1995, with permission from Elsevier Science.

This is one source of acid rain, a serious environmental problem. The sulfur dioxide content of an air sample can be determined. A sample of air is bubbled through an aqueous solution of hydrogen peroxide to convert all of the SO2 to H2 SO4. H2 O2 + SO2 H2 SO4 Titration of the resulting solution completes the analysis (both H atoms of H2 SO4 are titrated). In one such case, the analysis of 1.55 X 10 Lof Los Angeles air gave a solution that required 5.70 mL of 5.96 X 10 M NaOH to complete the titration. Determine the number of grams of SO2 present in the air sample. 

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