Anal. Chem. 1907, 5 9 , 1R-17R
Industrial Hygiene Marsha L. Langhorst* and Linda B. Coyne The Dow Chemical Company, Michigan Applied Science and Technology Laboratories, Analytical Laboratory, 574 Building, Midland, Michigan 48667, and The Dow Chemical Company, Health and Environmental Sciences Research Laboratory, 1803 Building, Midland, Michigan 48667
A. INTRODUCTION This review covers a period including 1985 and 1986, including thaw sections which were initially covered in the initial 1983 Analytical Reviews (AI) and the 1985 Analytical Reviews (A2). The intent of this review was to cover some of the most widely used analytical techniques in monitoring personal exposures in the workplace. To ensure a safe work environment in production plants and research laboratories, it is usually necessary to monitor trace quantities of organic vapors, inorganic vapors, aerosols, and/or particulates. The ability to achieve a safe workplace depends largely upon a cooperative team effort between industrial hygienists, analytical chemists, toxicologists, medical professionals, and possibly others (epidemiologists, engineers, statisticians, etc.). Good communication is required to ensure: (1)proper sampling for representative assessment of workplace exposures and interface to analytical techniques; (2) proper preservation of samples and selection of analytical techniques with the appropriate sensitivity, selectivity, accuracy, and precision; (3) proper interpretation of the results in light of toxicology data, epidemiology data, and regulatory requirements; (4) proper medical surveillance of personal health; (5) proper communication with workers and implementation of engineering controls or protective measures for health and safety in the workplace. It is beyond the scope of this review to discuss the entire subject of industrial hygiene, or even a complete review of the analytical aspects of this field. The main emphasis has been on the basic techniques: (1)sampling-by adsorption on solid sorbent tubes, by absorption in bubbler solutions, both active and passive sampling; (2) compound recovery-by solvent or thermal desomtion from a sorbent. extraction. etc.: (3) analwis by various tehniques, primarily chromatographic techniques (GC and HPLC). Occasionally, airborne compounds can be monitored directly without sampling or sample preparation steps. Beyond the basics, this review covers sections on derivatization chemistry, chemical dosimeters, biomonitoring, gas monitoring sensors and instruments, and particulate analysis. In addition, the monitoring of specific chemicals of widespread interest, formaldehyde and isocyanates, which were included in previous reviews has been extended over this two-year period. Monitoring methods for other chemicals of widespread interest, including PCBs (A3),mercury (A4), NO, (A5), and humidity (A6) have been reviewed elsewhere. While there is significant overlap between the areas of air monitoring for industrial hygiene purposes and air monitoring for environmental studies, the environmental area has been for the most part excluded from this review. As such, remote sensing instruments were largely omitted from the instrument and sensor areas. Some of the other topics which have been consciously left out include quality assurance (An, analytical methods for evaluation of the effectiveness of respirators and protective equipment (At?),standards (A9), and the preparation of test atmospheres, method validation, and sampling techniques (AIO). Sampling is an integral and vital element of industrial hygiene analytical methods. The effects of humidity and coexisting vapors on sampling, the sample preservation before analysis, and the sample interface steps before analysis cannot be overemphasized as critical elements in the process of industrial hygiene analytical chemistry. A review with many *To whom correspondence should be addressed at The Dow Chemical Company, Michigan Applied Science and Technology Laboratories.
references describes the strategy, equipment, procedures, and exposure limits in workplace air sampling (A10). Another paper covers the broad subject of sampling and monitoring indoor environments covering a variety of approaches ( A l l ) . A comprehensive source of information on monitoring methods for numerous compounds is available in volumes 1 and 2 of the NIOSH manual of analytical methods, which was revised in 1984 (A12).
B. SOLID SORBENT/SOLVENT DESORPTION Solid sorbents are used extensively to sample contaminants in air. There have been several reviews on the use of solid sorbents in the workplace (BI-B3). A tube containing a solid sorbent is convenient to use and can concentrate trace contaminants. This tube can be worn by the worker to determine breathing zone concentrations or placed in specific areas to determine workplace concentrations. Solid sorbents are preferred over impingers and whole air samples because they are simple to use, lightweight, and easy to transport. There are two basic techniques for collection of substances in air using solid sorbents. The most popular utilizes a small battery-operated pump to draw the air through a bed of solid sorbent. The second technique which is discussed in section E utilizes diffusion of compounds into a chamber containing a solid sorbent. The compounds are recovered from the sorbents by desorption with a suitable sorbent or by thermal desorption. Solyent desorption of collected compounds from solid sorbents is the most commonly used technique. The procedure is relatively simple; once the compound is desorbed, the extract can be analyzed by gas chromatography, liquid chromatography, or other standard analytical techniques. Parts-permillion concentrations in air are usually determined, although parts-per-billion limits are achievable for many compounds. Sometimes, in order to detect ppb levels of a compound, larger air sample volumes, high sensitivity detectors, or smaller desorption volumes are needed. Charcoal. Charcoal is the most widely used sorbent, while silica gel, alumina, and porous polymers are used for special applications and are becoming increasingly popular. Typically, carbon disulfide is used to desorb the organics from the charcoal. Starek et al. (B4) reported collecting kerosene vapors on charcoal with subsequent desorption with carbon disulfide and analysis by gas chromatography. Because charcoal can collect a wide variety of organics, the industrial hygienist is trying to collect more and more compounds on the same solid sorbent tube. Tyras et al. (B5) describe the collection of acrylonitrile, l,&butadiene, benzene, ethylbenzene, methanol, toluene, and o-xylene on the same charcoal tube followed by desorption with dimethylformamide and analysis by gas chromatography with flame ionization detection. Pentane, hexane, and heptane were determined in workplace air by collection on activated charcoal, desorption with toluene or carbon disulfide, and analysis by gas chromatography (B6). Since many of these compounds differ in volatility and polarity, many different desorption solvents besides carbon disulfide are being explored to help accomplish this task. Methylene chloride was used to extract Freon-12 and Freon-114 from charcoal followed by analysis by gas chromatography (B7). Butyl, isoamyl, and ethyl alcohol were collected on charcoal and desorbed with cyclohexane (B8). GC columns with Carbowax 20M were most suitable for butyl and isoamyl alcohol, whereas a column with Porapak Q was best for ethanol. Miazek-Kula et al. (B9)describe a method to collect nitromethane or nitroethane in air in the presence of
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acetone, methanol, ethanol, isopropyl alcohol, benzene, and toluene but not of xylene or butanol. The procedure involved desorption with chloroform and analysis by gas chromatography. Separation of nitromethane and nitroethane is not achieved by this method. Melcher et al. (B10)described a monitoring method for acrylonitrile using a 600-mg charcoal tube. No breakthrough was observed from 0.05 to 5.0 ppm and at 30-95% relative humidity. A desorption solvent containing 2% acetone in carbon disulfide was found to be the best desorption solvent, with a recovery of 90%. For this compound, the nitrogen-selective detector was more sensitive than the flame ionization detector and enabled one to determine acrylonitrile in the low ppb levels. Stranski (BI1) described the collection of N,N-dimethylformamide on activated carbon, followed by desorption with acetone. Analysis was performed by use of a column containing 10% Carbowax 20M + 3% KOH and an instrument containingan alkali flame ionization detector. Kacpura (B12)described a method for the determination of ethyl formate in air. Ethyl formate was collected on charcoal, desorbed with nitromethane, and separated on a column containing Carbowax 20M on Chromosorb W. Nitromethane was the most suitable solvent, compared to water, ethanol, propanol, and p-xylene. A new monitoring procedure was developed by Bishop et al. (B13)for ammonia in air. Air sampling tubes packed with beaded activated charcoal coated with sulfuric acid were used to collect ammonia from air. The low cationic background of this packing permitted analysis by ion chromatography. A concentration that is 0.05 of the threshold limit value (TLV) is detectable in a 3-L air sample volume;
