Anal. Chem. 1984, 6 1 , 128R-142R (M5) van Staden, J. F. Analyst 1987, 772, 595-599. (M6) Petrukhin, 0. M.; Avdeeva, E. N.; Shavnya, Yu. V.;Yankauskas, V. P.; Kazlauskas. R. M.; Bychkov, A . S.; Zolotov, Yu. A. Taianta 1987, 34, 111-121. (M7) Dan, D.; Xu, P.; Liu, L. Fenxi Huaxue 1987, 75(8), 706-709; CA 708: 142261h. (Me) Dan, D.; Dong, Y. Tabnra 1988, 35, 589-590. (M9) Wang, J. I n Electroanalytical Chemistry, Volume 76; Bard, A. J.. Ed.; Marcel Decker: New York, 1988; pp 1-88. (M10) Wang, J.; Tuzhi, Peng; Martinez, T. Anal. Chim. Acta 1987, 207, 43-50. (M11) Donat, J. R.; Bruland, K. W. Anal. Chem. 1988, 60, 240-244. (M12) Willie, S. N.; Berman, S. S.; Page, J. A,; vanloon, G. W. Can. J . Chem. 1987, 65, 957-960. ( M U ) Van Den Berg, C. M. G.; Jacinto, G. S. Anal. Chim. Acta 1988, 277, 129-139. (M14) Breyer, Ph.; Gilbert, E. P. Anal. Chlm. Acta 1987, 207, 33-41. (M15) Elwerfalli, J.; Page, J. A.; vanloon, G. W. Can. J . Chem. 1987, 65, 1139-1143. (M16) Lintern, M.; Mann, A.; Longrnan, D. Anal. Chim. Acta 1988, 209, 193-203.
(M17) Hatle, M. Talanta 1987, 34, 1001-1007. Prabhu, S. V.;Baldwin, R. P.; Kryger. L. Anal. Chem. 1987, 59, 1074- 1078. (M19) Thornsen. K. N.; Kryger, L.; Baldwin, R. P. Anal. Chem. 1988, 60, 151-155. (M20) Wang, J.; Martinez, T. Anal. Chim. Acta 1988, 207, 95-102. MISCELLANEOUS METHODS
(NI) Tuttle, M. L.; Goldhaber, M. 8.: Williamson, D. L. Talanta 1986, 33, 953-961. (N2) Hall, G. E. M.; Pelchat, J.; Loop, J. Chem. e o / . 1988, 6 7 , 35-45. (N3) Ueda. A.; Krouse, H. R. Geochem. J . 1968. 20, 209-212. (N4) Krouse, H. R.; Ueda, A. Applied Geochem. 1987, 2 , 127-131. (N5) Pickering, W. F. Ore Geology Rev. 1988, 7 , 83-146. (N6) Slavek. J.; Plckering, W. F. Can. J . Chem. 1987, 65, 984-989. (N7) Grondin, D.; Barbeau, C. Appl. Geochem. 1986, 1 , 697-704. (N8) Kersten, M.; Forstner, U. Mar. Chem. 1987, 22, 299-312. (N9) Martin. J. M.; Nirel, P.; Thomas, A. J. M a r . Chem. 1987, 22, 313-341. (N10) Kheboian, C.; Bauer, C. F. Anal. Chem. 1987, 59, 1417-1423. (N11) Tessier, A.; Campbell, P. G. C. Anal. Chem. 1988, 60, 1475-1476. (N12) Bauer, C. F.; Kheboian. C. Anal. Chem. 1988, 60, 1477.
Industrial Hygiene M a r s h a L. Langhorst* a n d Linda B. Coyne T h e Dow Chemical Company, Michigan Applied Science and Technology Laboratories, Analytical Sciences Laboratory, 1602 Building, Midland, Michigan 48667, and T h e Dow Chemical Company, Health and Environmental Sciences Research Laboratory, Analytical and Environmental Chemistry, 1803 Building, Midland, Michigan 48667
A. INTRODUCTION
containing volatile compounds, has been included or extended over this two-year period. Monitoring methods for other chemicals of widespread interest, including inorganic compounds (A4),aldehydes (A5),solvents ( A 6 ) ,and benzene (A7) 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 spectroscopy-based monitoring systems were largely omitted from the sensor and instrument area of this review. Some other topics that have been consciously omitted due to limitations of space and time include quality assurance, analytical procedures for evaluation of the effectiveness of respirators and protective equipment, laboratory and field validation of solid sorbent samplers (A@, and sampling strategy ( A 9 ) . Sampling and analysis of indoor air, rather than personnel, have been largely omitted, but a few excellent, comprehensive reviews are worth mentioning (AIO-AI2). 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 science of industrial hygiene analytical chemistry. Several comprehensive sources of information on monitoring methods for numerous compounds are available including: Volumes I and I1 of the NIOSH manual of analytical methods, which was revised in 1984 (A13),the U.S. Army’s new Industrial Hygiene Sampling Guide (A14),a compendium of methods for the determination of toxic organic compounds in ambient air (A15),and a review of manual and automated methods for the determination of organic and inorganic compounds, including labile compounds (A16). A new book entitled Advances i n Air Sampling is also an excellent reference on particle, gas, vapor, and aerosol sampling including sampling strategy ( A I 7).
This review covers the period including 1987 and 1988, including those sections that were covered in the initial 1983 Analytical Reviews ( A l )and the subsequent 1985 and 1987 Analytical Reviews ( A 2 , A3). The intent of this paper is to review some of the most widely used analytical techniques in monitoring personal exposures in the workplace for assessing human health risk. T o 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 in air. The ability to achieve a safe workplace epends 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 (a) proper sampling for representative assessment of workplace exposures and interface to analytical techniques, (b) proper preservation of samples and selection of analytical techniques with the appropriate sensitivity, selectivity, accuracy, and precision, (c) proper interpretation of results in light of toxicology data, epidemiology data, and regulatory requirements, (d) proper medical surveillance of personal health, and (e) proper communication with workers and implementation of engineering controls and 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 placed on the basic techniques: (a) sampling, by adsorption on solid sorbent tubes, by absorption in bubbler solutions, both active and passive sampling; (b) compound recovery, by solvent or thermal desorption from a sorbent, extraction, etc.; and (c) analysis by various techniques, 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 sensors and instruments, and particulate analysis. A new section has been added covering briefly some of the recent papers on the preparation of standards and test atmospheres. In addition, the monitoring of specific chemicals of widespread interest, including formaldehyde, isocyanates, and sulfur-
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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. 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
* Author t o w h o m correspondence should be addressed a t Analytical Sciences Laboratory, 1602 Building. 128 R
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1989 American Chemical Society
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Manha L. Lanphont is Research Leader in Of the the Analytical Sciences LaboratMichigan Applied Sciences and TechnOlDgy Laboratories (MAST8L). She joined Dow's Analytical Laboratory in 1975 upon graduation from the University of Illinois. She has primarily been involved in problem salving and development of chrOmstOgraphic methods and instrumentation lor the trace analysis 01 compounds in DOWproduns and environmental matrices (sir. water. biologicals). Her current research deals With high-speed gas chromatography and high-performance \ thin-layer chromatography. Other activities include caordinating the analytical aspects \ i of air monnoring as it applies to process waste reduction projects. Caw's Air EmislOn Inventory program. and regulatory permining. Mr. Langhorst has authored or Coauthored 22 papers in the area Of anaiyical Chemistry and is a member 01 the American Chemical Society. Analytical Chemistry Division and Chromatography Section. 1 Linda 8. cop. is a F m ~ C Leader t in Me Analytical and Environmental Chemistry Group of the Dow Chemical Company. Midland. MI. She received her B.S. degrees in Chemistry and biology from Saginaw Valley State College. She joined DOWin 1978 and has spent the majority of her career involved in research and development in the industrial hygiene analytical group. She has been primarily involved in me devebpment of Chromatographic methods for trace analysis of organics in air. evaluation 01 direct-reading instrumentation. Sample analysis. and protective equipment evalUatiOnS. MS. Came has authored or coauthored 8 publications in the field 01 Industrial hygiene and has presented 14 papers at various American Industrial Hygiene Conferences. She is a member of the American Chemical Society and the American Industrial Hygiene Association.
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 solid sorbent. The compounds are recovered from the sorbents by desorption with a suitable solvent or by thermal desorption. Solvent 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. Part-per-million concentrations in air are usually determined, although part-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. Activated charcoal is the most widely used sorbent, while silica gel, alumina, and porous polymers are used for special applications. Typically, carbon disulfide is used to desorb organics from the charcoal. Posniak (81) reported collecting diethyl ether and isopropyl ether on charcoal with subsequent desorption with carbon disulfide and analysis by gas chromatography (GC). Methyl ethyl ketone, n-butyl alcohol, xylene, ethylene glycol, ethylene glycol acetate, cyclohexanol, cyclohexanone, and butylene glycol were collected on charcoal, desorbed in carbon disulfide, and analyzed by GC (82). Puskar et al(83) reported using Columbia JXC charcoal to collect ethylene oxide (EO). These tubes were desorbed with carbon disulfide and analyzed by GC with flame ionization detection (FID). Recoveries were 84% for 15-min TWA concentrations of 2.5, 5.0, and 10.0 ppm EO. While carbon disulfide may be an excellent solvent for desorption of organics from activated charcoal, other desorption solvents are continuously being explored. This is due to the fact that the industrial hygienist is faced with the task of monitoring for a wide variety of organics in the workplace. Many times these compounds differ in volatility and polarity, making alternate solvents a necessity to recover and quantitate successfully. Octane, cyclohexene, methyl bromide, and
methyl iodide were determined in air by using collection on activated charcoal, desorption in toluene, and analysis by gas chromatography (84-R7). Acetone was used to extract carhofuran from activated charcoal (88).Gaweda e t al. used xylene or chloroform to extract 2-butoxyethyl alcohol from activated charcoal followed by analysis by GC (89).Raulinaitis found that multicomponent solvent mixtures were more effectively eluted from charcoal when a 5% formic acid in carbon disulfide was used compared to just carbon disulfide alone (R10). Ashida e t al. found that 19 organics, including butanol and butyl cellosolve, were effectively desorbed by using a two-phase desorption solvent of carbon disulfide and water (R11). Depending on the partitioning of the compound between the two phases, either one or both layers were analyzed by gas chromatography. Langvardt e t al. also found this technique quite successful for determining concentrations of solvents in the workplace (812). While most of the methods used in solvent extraction of charcoal are based on GC, other techniques are used. Nickel carbonyl was collected in charcoal, desorbed in 3% nitric acid, and analyzed by atomic absorption spectrophotometry, A recovery of 93% WBS obtained with this technique (R13). Paryjczak e t al. describe a method to collect dibromoethane on charcoal. The charcoal is extracted in ethanol and analyzed spectrophotometrically, with sensitivities ranging from 20 to 30 mg/m3 (814). While activated charcoal is the most popular carbon used to collect organics from the air, occasionally graphitized carbon is used. Kissa describes a method to collect organofluorine compounds on either activated charcoal or graphitized carbon, followed by combustion to HF, and determination with a fluoride ionselective electrode (815). Graphitized carbon was used to collect airborne 2,3-dihromopropanol with analysis by GC/ FID. Recoveries ranged from 90 to 100% and samples spiked with 2,3-dibromopropanol could he stored for 3-4 weeks a t room or refrigerator temperatures with minimal loss in recovery (816).While selection of desorption solvent is a critical factor in the recovery of a compound from charcoal, other factors such as relative humidity, storage stability, and interferences can also have an effect on the recovery of a compound. Underhill demonstrated how relative humidity can affect the adsorptive capacity of c h a r d for compounds (817). Rudling e t a%found that cyclic and aliphatic ketones adsorbed on activated charcoal did not store well. Esters decomposed 5520% on activated charcoal while toluene, butyl alcohol, styrene, and ethyl acrylate were stable (818). These data emphasize the importance of evaluating these parameters prior to sampling for contaminants in the field. Silica Gel. Silica gel is widely used to collect moderately polar compounds usually of low vapor pressure and hlgh molecular weight. Liang e t al. utilized silica gel to collect organophosphorus agrochemicals in the air. Acetone and benzene were used to extract these compounds with analysis by gas chromatography with flame photometric detection (819). A modified silica gel sorbent is described for the determination of pesticides in air, The silica gel is extracted in diethyl ether, reconcentrated in hexane, and analyzed by GC (820). Williams et al. utilized Florid to selectively collect several organics automatically at remote sampling locations (821). Diazinon levels in indoor air were determined by collect on Supelco-20P and analysis by capillmy GC and NP detection (822). Polyphenylmethylsiloxaue-coateddiatomite was used in workplace air (B23). to collect 1,2,3-trichloro-1,3-butadiene Other Sorbents. Although charcoal and silica gel are extensively used in the field of industrial hygiene, porous polymers and chromatographic packings are becoming increasingly popular. These sorbents have a wide range of surface areas and are not as susceptible to humidity effects that are seen with silica gel. Bombi e t al. described a study where alumina was used t c collect atmospheric hydrogen chloride. The analyte was then extracted by washing with 0.5 M K N 0 3 and analyzed potentiometrically with a chloride-selective electrode (824). Tenax-TA was found to he effective in collecting several amines in the workplace. The amines were extracted from the Tenax with sodium hydroxide solution and analyzed by GC using a Triton X-100 + KOH column packing (R25). Kashihira et al. described a study where acetaldehyde is collected on alkalized Porasil A and separated by GC using a Porapak Q column (826). Aliphatic amine ethers and alicyclic amines were sampled in air by using Thermosorh A tubes (827). Caesar described a study where ANALYTICAL CHEMISTRY, VOL. 61. NO.
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bis(chloromethy1) ether (BCME) was collected on Porapak Q and analyzed by GC with a halogen-specific detector. The limit of detection was 1 ppb BCME in air (B28). Zhang reported using TDX-01 carbon molecular sieve as an adsorbent for sample collection of C6-C8 benzene series hydrocarbons in air (B29).Saito et al. described a study were dichlorvos and finitrothion are collected on octadecylsilane cartridges, eluted with methanol, and analyzed by GC (B30). Impingers. Impinger can be very cumbersome for monitoring compounds in the field, but sometimes, there are few alternatives. Tanaka et al. collected formic acid, acetic acid, formaldehye, and acetaldehyde in two bubblers arranged in series (B31).The resulting solution was then analyzed by ion chromatography with conductivity detection. In another study, 1,3-propanesulfone was collected in a impinger containing methyl isobutyl ketone (B32). This compound is analyzed by GC with sulfur-selective detection. Recovery Considerations. In the determination of the recovery of a compound from a solid sorbent or in an impinger solution, there are several factors such as relative humidity, storage, sample flow rates, and interferences which can influence the collection of the compound as well as the recovery from the sample medium. Verkoelen et al. found substantial losses of l,l,l-trichloroethane, trichloroethylene, benzene, tetrachloroethane, and toluene collected on Tenax adsorption tubes and stored a t ambient temperatures for 70 h (B33). Charcoal tubes containing 2,3-dibromopropanol showed minimal losses after 3-4 weeks of storage at ambient or refrigerator temperatures (B16).It is important to identify potential interferences in the work environment so they can be tested as part of the method validation. Rudling et al. found that esters decomposed on activated charcoal due to the presence of alcohols (B18).In another study, Posniak (B6) found that dibromoethane, benzene, hexane, and bromoform did not affect the determination of methyl bromide in air (B6). The determination of methyl iodide in air is affected by presence of methanol, ethanol, and diethylamine but is not affected by the presence of benzene (B7). Thermal Desorption. In the thermal desorption technique, samples are collected by pulling air through a tube containing a thermally stable sorbent bed. Instead of removing the sorbent and extracting/desorbing compounds from the sorbent with a solvent before analysis, the tube is heated and the adsorbed compounds are purged directly into a gas chromatograph or into a holding chamber or trap for later analysis. Thermal desorption eliminates use of solvents and other handling operations and is more sensitive than solvent desorption techniques, and the collection tubes are reusable. High sensitivity is achievable since the whole sample can be injected at one time or concentrated in a low-volume chamber. Polymeric adsorbents such as Tenax GC, Porapak, Q, and Chromosorbs continue to be popular collection materials for use with thermal desorption. In a study by Lawrence et al., trace amines were collected on a two-stage tube, the first stage containing Tenax GC and the second stage containing soda lime (B34).In another study, Raymer (B35)describes using Tenax GC and supercritical carbon dioxide to desorb compounds such as hexachlorobiphenyl, anthracene, and parathion. All compounds were recovered in excess of 90%. A cryogenic collection technique was developed for routine analysis of atmospheric peroxyacetyl nitrate (PAN) (2336). The Teflon collection tube was packed with 0.3 g of Teflon beads and gave good recoveries over a temperature range of 0-70 "C. Acetone and benzene were collected and thermally desorbed successfully on Porapak Q and Chromosorb 101,102, and 103 (B37). In a study by Hanika (B38),toluene and benzene were collected on Porapak Q and thermally desorbed into the GC. Activated charcoal, although most commonly used in solvent desorption, is also used in thermal desorption. 34 solvents were tested individIn a study by Cocheo (B39), ually and in mixtures on activated charcoal. The analytes were thermally desorbed into a gas chromatograph and yielded recoveries for all analytes of 90% or greater.
C. CALIBRATION STANDARDS AND DYNAMIC VAPOR ATMOSPHERES Preparation of gas and vapor standards or the generation of dynamic atmospheres with known concentrations is an important aspect of air analysis and monitoring. A review on calibration in air analysis, including sources of error, evaluation 130R
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and minimization of uncertainty, linear relationships and intercalibration was recently published by ASTM (CI). New devices and procedures were described for the dynamic generation of test atmospheres as a means of preparing standards for the evaluation of adsorption tubes and diffusive samplers (C2,C3). One device utilizes the saturation vapor pressure principle to generate low-level calibration atmosphere from liquid or solid substances with finite vapor pressures (C2). Another device uses a unique configuration of solvent evaporators and diffusion regulators to prepare atmospheres of known concentration (C3).Preparing parts-per-billion levels (10-150 ppb (v/v)) of volatile organics is a challenge due to background levels, ghost peaks in GC, adsorption on container walls, preparation of primary standards, and contamination of cylinders. These problems were discussed in a recent publication and approaches for minimizing these problems have been proposed (C4). Defining the performance of dynamic atmosphere generation equipment (whether a permeation tube system, a gas saturator, diffusion vessel system, dynamic gas blender) is important. Performance accuracy for a few systems has been described (C5, C6). The accuracy of reference gas standards is also very important, particularly for the calibration of automated monitoring instruments. During 1980 and 1981, a round-robin test was conducted for the international comparison of reference gases, including CO, COz, C3H8,NO and SO2in nitrogen with concentrations from 3 to 3000 ppm (v v). Standards from the National Bureau of Standards (N S), Environmental Protection Agency (EPA), British 0 Co. Ltd., Van Swinden Laboratorium, L'Air Liquide, and Chem. Inspection and Testing Institute of Japan took part in the comparison which showed that these reference gases agreed in concentration for the most part with most concentration differences within 1% (C7). Stability of vapor standards is also a concern and important. Stability studies of HCl and H F calibration gases in nitrogen in pressure cylinders were shown to be stable for 2-year and 1-year periods, respectively, with concentrations of 510 and 9.2 mg/m3, respectively (C8). A study of the stability of odorous sulfur-containing compounds enclosed in containers of various materials indicated significant wall losses in many materials particularly for volatile mercaptans (C9). For reactive gases and other difficult measurements, ASTM makes some recommendations for special calibration systems, including problem recognition tests, dilution systems, use of internal standards, and chemical conversion approaches (CIO). Some excellent papers deal with the generation of standards or dynamic atmospheres for a number of specific compounds or classes of compounds: halogenated hydrocarbons at ambient concentrations (Cll), formaldehyde vapors (CI2, CI3), gaseous sulfur compounds including H2S, CH,SH, CSz, and SO2 at ppb/ppt levels (C14,CI5),and nitrogen oxides ( C I S , (217).
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D. DERIVATIZATIONS Chemical derivatization techniques are often used in industrial hygiene applications to stabilize reactive chemicals during collection, increase detection sensitivity or selectivity, and change chemical properties to improve chromatographic behavior. Analytical derivatization reactions are a form of synthetic organic chemistry in which the goal is 100% yield of a single pure product. Although this goal is rarely achieved in macroscale organic reactions, the use of high-purity, highly reactive reagents, often in large excess, makes microscale reactions essentially quantitative. Compounds that are reactive or unstable are derivatized during collection, either in a reagent-containing bubbler solution or on a reagent-coated solid sorbent or support. Fast response, chemically impregnated paper tapes and detector tubes have been prepared for a variety of chemicals. Two recent papers review the applicability of detector tubes for the determination of compounds such as CO, SO2, NO, NOz, 03,C12, HC1, H2S, PH3, and AsH3 (01, 02). Further discussions on the specificity, accuracy, and practical limitations of colorimetric detector tubes have also been published (03, 0 4 ) . There is on-going development in the area of detector tubes, for example the addition of manganese chloride to a KI indicator to determine C12 in air (D5). Other compounds, which are stable during collection, may be derivatized after collection if they are difficult to analyze
INDUSTRIAL HYGIENE
or to provide enhanced sensitivity. Organic Compounds. There were numerous references to the use of 2,4-dinitrophenylhydrazinefor simultaneous collection and derivatization of aldehydes and ketones (carbonyl compounds) in air, including HCHO (06-081, acetaldehyde, EtCHO ( 0 7 , 0 8 ) ,acrolein (091,propionaldehyde (D8),acetone, 3-chloroacetylindole (DIO),and glyoxal (011). The resulting hydrazone is determined by HPLC with UV detection. In addition, hexamethylenetetramine (aerosol and vapor) is converted to HCHO and quantitatively collected/ derivatized when sampled on glass-fiber filters impregnated with H3P04 and 2,4-dinitrophenylhydrazine ( 0 1 2 ) . The reagent has been coated on Carbopack B ( 0 8 )and acidified silica gel (D9)for active sampling or on glass fiber filters for pasive (diiffusional) sampling ( 0 6 ) . Other papers dealing with the determination of specific compounds following derivatization included the determination of toluene diisocyanate following derivatization with 1-(2-methoxypheny1)piperazineto form urea derivatives (013), the spectrophotometric determination of CSz by formation of a nickel(I1) ethylxanthate complex (0141,the determination the of hydroquinone after conversion to benzo uinone (D15), determination of dimethylsulfate in air by 8 C with N-specific detection after conversion to MeCN with KCN (Dl6),and the determination of azodicarbonamide in air of plastics processing operations following conversion to hydrazine and then to aldazine (017). A patented device was described for the detection of organophosphorus pesticides and carbamates using the reagent 2,6-dichlorobenzeneone indolphenyl acetate (018). Inorganic Compounds. A variety of procedures and devices were reported for the determination of nitrogen oxides, particularly NOz, in air (019-022). 1-Methylperimidine, on a solid support, serves as a stable, sensitive, and selective rea ent for monitoring NOz, in the presence of 03,Clz, Brz, HP8,SOz, CO, or C 0 2 ( 0 1 9 ) . An azo compound was formed with NOz in air and nitrite in water for polarographic determination ( 0 2 0 ) . For CO monitoring, a palladium(I1)-acetamide complex was proposed as a solid-phase warning device for the presence of CO ( 0 2 3 ) . Alternatively air can be analyzed for CO by adsorption in an aqueous solution of sulfanilic acid and Ag+ for photometric detection of the reduced silver ( 0 2 4 ) . A couple of devices and procedures were published for the determination of ozone, including one that used the reagent phenoxazine on a solid support ( 0 2 5 , 0 2 1 ) . Hydrogen peroxide levels in air can be spectrophotometrically or fluorometrically detected following collection/derivatization (026, 027). Other derivatization procedures were published for the COz (029),HF (030),Hg (031), determination of HCN (OB), Cr(V1) (032),and tungsten (033),using some interesting and unique chemistries. E. CHEMICAL DOSIMETERS Chemical dosimeters (passive/diffusional dosimeters) measure time-weighted-average concentrations (or doses) by collection of an airborne vapor according to the principles of mass transport across a diffusion layer or permeation through a membrane as the rate-limiting step. In a diffusional dosimeter, the steady-state mass transport of vapors follows Fick’s law from the defined aperture(s) on the front of the bad e, through a length of diffusion space to the collection me c fium. A choice of Sam ling rates, dose ranges, and sensitivities can be obtained &pending upon the dosimeter geometry or design parameters. The permeation dosimeter operated based on the fact that the rate at which a given gas permeates a given membrane is a simple function of concentration in the air and the time of exposure (or sampling). There are a variety of commercial dosimeters available and noncommercial prototypes discussed in the literature. Generally, they are based on the following principles listed: sampling by diffusion or permeation; collection by adsorption, absorption, or derivatization; desorption by solvent, thermal, or no desorption; and determination by chromatographic (gas, liquid, thin layer, or ion chromatography), colorimetric, spectrophotometric, selective electrodes, or other methods. During the past two years, a few excellent review papers have been written on chemical dosimetry (EI-E3). One paper provides an assessment of the advances in chemical dosimetry
made since 1970, including an overview of reagent-type monitors with direct and indirect readout and solvent or thermally desorbed diffusion samplers ( E l ) . Another review deals with the geometry and sorbents of diffusive samplers and the choices for various sampling applications (E2). A third general paper reviews the theoretical aspects of diffusive sampling, including a mathematical treatment of the mechanisms affecting the uptake rate and sorbent effects and the design of samplers to meet particular needs (E3). Several authors tried to make a judgement as to the applicability of passive samplers and their contributions in appropriate use circumstances (E4-E7). Chemical dosimeters eliminate the need for calibrating and maintaining sampling pumps, and they can be worn in the breathing z6ne with little interference to the worker. These advantages have resulted in a continued interest in chemical dosimeters. In the past two years, additional studies have been completed on the fundamentals of passive dosimetry and the parameters that affect performance, including temperature, pressure, humidity, storage, face velocity (E8),fluctuating concentrations (E9),and air currents (ElO)/air turbulence ( E l l ) . Five dosimeters designed to detect NH3,Clz, HzS, NOz, and SOzwere used to evaluate the effects of temperature and humidity on the performance of length-of-stain dosimeters ( E l 2 ) . A study of the theoretical and experimental effects of wind on NOz passive samplers showed that the sensitivity of the Palmes tube design to changes in wind velocity is higher than that of filter badges ( E l 3 ) . Protocols for evaluation of passive monitors, for example those published by the National Institute for Occupational Safety and Health (NIOSH) (E14)and the Health and Safety Executive (HSE)(El5),have become quite common with data interpretation based on statistical treatment. By use of HCHO, SOz, and NH:, as test compounds, a performance verification protocol was described and applied (E16). A comprehensive European interlaboratory study of passive organic vapor monitors (3M OVM-3500) was conducted for determining a broad range of organic compounds ( E l 7). A widely used approach to chemical dosimeter evaluations is the generation of comparison data for active and passive sampling methods with a statistical evaluation of the equivalency of the methods (El8-E21). These studies often involve comparisons of charcoal tubes with organic vapor monitors exposed to specific vapors under laboratory or field conditions. Commonly mentioned dosimeters included the 3M organic vapor monitor, the SKC Solid Sorbent Badge, and the MSA Vaporgard. One validation study for passive organic vapor dosimeters evaluated its application in solvent exposure monitoring by using biomonitoring (breath and urine) parameters for comparison (E22). During the past two years, there has been a large increase in the development, evaluation, and use of thermally desorbable diffusional sampling devices-particularly with the Perkin-Elmer ATD (Automatic Thermal Desorption) system (E23) and the Simtec Absorba monitors (E24). The procedures for vapor-phase spiking and method evaluation have also been reported (E25-E27). With the proper selection of adsorbents, tube-type diffusive samplers can provide constant and predictable uptake rate (E28). A personal sampling method for the determination of styrene exposure was described and evaluated (E29). A simple, versatile, low-cost, unique method of personal monitoring was reported that used the combination of collection of the analyte on a diffusive sampler followed by thermal desorption onto a short-term stain-length tube (E30, E31). Novel Designs and Systems. Novel designs and novel use of sorbents have also been reported. A passive cone sampler (E32),a membrane-covered dosimeter with arched substrate carrier (E33),and a new sampler for use with both liquid and solid substrates (E34) have been reported to have advantages over previous designs. Because current designs often have sampling rates considerably lower than those used for tube/pump sampling, the sensitivity of diffusional dosimeters has often been inadequate for determining short-term excursion doses or low ppb level concentrations. As a result, a new passive sampler was developed for monitoring ambient levels (2-600ppb (v/v)) of organic vapors (E35). The use of Orsa tubes, diffusive samplers filled with activated carbon, inside face masks has made it possible to check the effecANALYTICAL CHEMISTRY, VOL. 61, NO. 12, JUNE 15, 1989
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tiveness of protective filter masks (E36). For the determination of organic vapors in air, a novel adsorbent was made by insertion of organic molecules in a clay mineral lattice structure (E37).Experiments showed that the adsorption isotherms resembled that of strong adsorbents, that the surface area exceeded that of charcoal, and that the capacity exceeds that of porous polymers. In addition, the adsorbent is pale in color for use with colored indicator compounds and can be used with thermal desorption. Diffusive personal samplers with molecular sieves are reported useful for the determination of water (E38)and N 2 0 (and anesthetic gases) in air (E39442).A new passive monitor using sorption on a heavy atom chemical was developed for the direct determination of polycyclic aromatic hydrocarbons (PAH) vapors (E43). The quantitation is by room-temperature phosphorescence without prior extraction or desorption. A diffusive sampler for formaldehyde in air used chemisorption glass fiber filters and on 2,4-dinitrophenylhydrazine-coated showed good comparisons with active sampling procedures (E44).Another dosimeter utilizing chemisorption was developed for monitoring phosgene in air by using 4'-nitro-4benzylpyridine as the reactive sorbent (E45). Organic Compounds. To monitor occupational exposure to tetrachloroethylene and xylene, active and passive monitoring procedures along with biological monitoring were compared (E46).Use of passive dosimeters for monitoring occupational exposure to styrene, xylene, and hexane also showed excellent correlation with biomonitoring parameters (urinary metabolite levels) (E47). A laboratory validation study was conducted for the 3M organic vapor monitor exposed to mixtures of benzene, toluene, xylene, and diethylbenzene (E48).Other papers reported to the use of chemical C7-Cl2 aromatics dosimeters for sampling benzene (E49), (E50),methyl acrylate, butyl acrylate, and n-butyl alcohol (E51). In addition, diffusive sampling/thermal desorption procedures were published for the determination of ethylene oxide (E52)and 2-propanol (E53).An interesting paper described a simple diffusive monitor to measure exposure to passive smoking by collection of nicotine on a filfer coated with NaHSO" (E54). Inorganic compounds. Recent publications have reported the development of new diffusive sampling devices for NO2 (E55, E%), ammonia (E57-E59), and mercury (E60-E62).
F. BIOMONITORING Biological monitoring involves the analysis of human tissues and excreta for the evidence of exposure to chemical substances. Biomonitoring may involve the direct measurement of a chemical or metabolite in a biological matrix or an indirect measurement of a biochemical or physiological change that occurs in response to the exposure. The "ideal" biomonitor detects changes before significant damage occurs, is specific, correlates with exposure and effect, and occurs shortly after exposure. Important factors in biomonitoring include the choice of biological specimen, the analytical methods, a knowledge of metabolism and pharmacokinetics, and the patttern of exposure. A biological monitoring study, when properly designed, provides a better indication of internal dose and better estimate of risk than air monitoring. The relative complexity of biomonitoring relative to direct exposure monitoring makes widespread use of biomonitoring impractical at this time. Some biological matrices which have served as monitors of occupational exposure include breath, urine, blood, saliva, hair, skin, fingernails, and clinical parameters. Breath is an easily obtained specimen, but its use is limited to those substances with sufficient volatility to appear in the breath in measurable amounts. A few new procedures for breath sampling and subsequent analysis have been recently reported (FI-F3).One sampling device uses a modified half-face air purifying respirator with a two-part sorbent cartridge attached to the exhaust port ( F I ) . Urine is one of the most frequently analyzed biological specimens, due to its ease of collection and the presence of nearly all exogenous chemicals and their metabolites in amounts proportional to the absorbed dose. Blood is the body fluid that usually shows the best correlation with the atmospheric concentration, the amount absorbed (regardless of exposure route), the degree of retention, and the severity of effect. Blood is often the best method when exposures are 132R
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intermittent, when skin absorption is a primary route of exposure, when there are added nonoccupational exposures, or when exposure to complex mixtures is monitored. T o use blood or urine as a biomonitoring indicator, a good knowledge of metabolism and pharmacokinetics is usually essential. Saliva, which is 99% water, and a fairly good indicator of blood levels, is an underutilized, noninvasive biomonitor. Hair and fingernails are useful for monitoring exposure to minerals and inorganic species. Instrumental neutron activation analysis may be used for analysis. Skin has been used to determine pesticide accumulations. Analytical techniques for biomonitoring usually involve sample hydrolysis or extractions, cleanups or preliminary separations, concentration steps, and, finally, analysis by a variety of techniques, primarily GC/MS, GC, HPLC, and radioimmunoassay. Organic Compounds. Benzene exposure of chemical workers was studied by workplace environmental monitoring and biomonitoring using breath, blood, and urinary (phenol) measurements (F4).An extensive 4-year study using three biomonitoring methods (breath, blood, and urinary hippuric acid) was completed as the basis for development of a monitoring strategy for assessing uptake/exposure for toluene (FS). Another toluene biomonitoring study using urinary hippuric acid concluded that levels 25 mmol/L are indicative of exposure below or above the threshold limit value (TLV) (F6). Breath samples from human subjects are analyzed by two procedures showing good correlation. Samples were initially analyzed directly by IR spectroscopy, then collected on silica gel sorbent tubes, and subsequently analyzed by headspace gas chromatography (F7). An enzymatic reagent using an alcohol oxidase was developed for the determination of primary C 1 4 4 alcohols in biological fluids, expired air, and other matrices (F8). The urinary metabolite of 2-ethoxyethanol, 2-ethoxyacetic acid, was extracted as an ion pair, derivatized with pentafluorobenzyl bromide, and analyzed by GC-FID for a study of occupational exposure to 2-ethoxyethanol (F9). By use of human subjects exposed to tetrachloroethylene (perc), alveolar air was sampled a t selected residence times in the lungs (t*). The data showed that the concentration of perc in alveolar air at t* = 5 s provided a reasonable estimate of the time-weighted-average concentration in arterial blood (FIO). A survey for the detection of trichloroacetic acid in the urine of workers occupationally exposed to trichloroethylene, indicated a correlation with clinical cases of pneumatosis cystoides coli (PCC) following chronic exposure (F11). Plasma chloroform levels were determined by headspace GC in a study of users of indoor swimming pools (F12). Some other biomonitoring studies involved the determilow molecular weight nation of isoparaffins in blood (F13), hydrocarbons in exhaled breath (F14),CS2 in breath (by GC-FPD-S) (F15), p-dichlorobenzene in urine (F16), and chlordimeform pesticide in urine (FI 7). Polycyclic aromatic hydrocarbons (PAHs) were determined in ambient air, occupational air, and urine of smoking and nonsmoking workers and compared to ascertain whether these particulate-adsorbed PAHs were bioavailable based on urinary excretion. It was concluded that air monitoring for PAHs may not provide adequate information for assessment of occupational health hazards from airborne PAHs (F18). A spectrophotometric method was reported for the determination of hydrogen cyanide in air and biological fluids (F19). Alternatively, blood cyanide levels may be determined by GC with NP detection (F20). Inorganic Compounds. Symptoms suggestive of occupational asthma in workers in a mineral analysis lab were correlated with exposures to vapors of HC1, HF, HN03, HClO,, and H2S04(F21).Cold vapor atomic absorption spectrometry and GC were used for the determination and speciation of Hg. Total Hg, methylmercury, ethylmercury, and phenylmercury concentrations in urine samples from a dental workplace were investigated (F33).Mercury and arsenic concentrations in the urine of chlor-alkali plants were also studied by use of cold vapor and hydride atomic absorption (F23). Lead in hair of exposed gas station workers and unexposed adults was determined by microwave-aided dissolution of samples and flow injection atomic absorption spectrometry (F24).Blood lead and erythrocyte-free protoporphyrin have been used as indexes for screening and detection of occupa-
INDUSTRIAL HYGIENE
tional lead exposure (F25).Other references involved the determination of heavy metals (Ni and Co) in human hair specimens (F26) and the determination of ammonium thiocyanate in air, blood, and urine (F27).
G. GAS MONITORING SENSORS While the detection of compounds in gas-monitoring instruments often involves sensors of some sort, the section on sensors has been separated from the section on instruments in its review. While the distinction may be unclear in some cases, the gas monitoring instruments usually involve some sort of sample treatment (chemically or chromatographically) rather than direct sensing of the compound of interest. The function of a sensor is to identify a specific chemical or molecule in air and produce a signal in response related to the concentration of that chemical. Sensors are important in industrial hygiene applications for both personal and area monitoring. Important considerations with gas monitoring sensors include specificity, sensitivity, applicable concentration range, effects of humidity, temperature and coexisting species, stability, and response and recovery with exposure. Rapid response to both upward and downward concentration changes assures that sensors can be timely and representative monitors. Sensors have been greatly reduced in size, and there is such an abundance of information processing capability, that sensors are being built into arrays for broad application (GI-G3). Recent papers describe the use of coated piezoelectric crystals as a multisensor array for mixture resolution of chemical vapors (GI-G2). Sensors can be classified as electrochemical, thermochemical, biochemical, optochemical, and solid-state semiconductors. A review of sensors for analytical purposes, including vapors monitoring has been published (G3). A paper on nonaqueous electrolyte electrochemical sensors was of recent interest for detecting a variety of gases, including Oz, CO, COz, NO,, and HCHO (G4). Porous glass optical fibers and other designs of optochemical sensors contain reagents capable of producing optical spectra changes in the presence of particular chemicals ( G 5 4 9 ) . Fiber optic based optochemical sensors are described for the detection of polar solvent vapors (G5),methane (G6), flammable gases (G7), and ammonia (G8). Several investigators are studying the feasibility and applicability of piezoelectric crystals with various coatings for the detection of chemical vapors ( G 9 4 1 3 ) . In particular, liquid crystal coatings were evaluated as coatings for the detection of benzene, toluene, chlorobenzene, and other aromatic compounds (G9). Modified cyclodextrins were coated on quartz crystals for detection of benzene vapors ((210). Coatings were developed for detecting chemical warfare agents (G11). Also, protein coatings, such as acetylcholine esterase and parathion antibodies, were sensitive detectors (36-680 ppb) for gaseous parathion, malathion, methyl parathion, disulfoton, and ethion (G12, (213). Inorganic Sensors. A review has been published on the development of oxygen sensors. Three types of oxygen sensors-Zr02 sensors, TiOz sensors, and electrochemical sensors-were reviewed. Looking toward the future, the introduction of thin-film and micromachining technology to the fabrication of O2 sensors will aid development of a new generation of sensors ( G I 4 ) . Semiconductor sensors are reported for the direct detection of Hz, NH3 (G15),CO (G16-G18), and H2S (G19, G20). A portable electrochemical gas analyzer was evaluated for monitoring CO and HzS short-term exposures (G21). Several papers describe designs for new types of chemical sensors. A chemisorption-type ceramic sensor was developed for detecting both water vapor content in mixed air samples and air velocity (0.4-4m/s) (G22). Another humidity sensor uses electrically conducting particles dispersed in a porous quartz glass support (G23). A new design for chlorine gas sensors was described that uses lead(I1) chloride solid electrolyte (G24). An evaluation study was reported dealing with the evaluation of a diffusion-type electrochemical sensor, the Sensidyne toxic gas sensor for hydrogen fluoride vapor (G25). A review of methods for NO, determinations includes a discussion of electrochemical and semiconductor NO, sensors as well as chemiluminescence and IR and UV-vis spectroscopy procedures (G26).
H. GAS-MONITORING INSTRUMENTS While the measurement of chemical vapor mixtures can be quite complex, the practical requirements for useful monitoring instruments include simplicity, low cost, rapid response and unattended operation. Some instruments are directreading, while others utilize microprocessor-based data loggers to record data for subsequent data retrieval and manipulation. The principle of measurement for industrial hygiene vapor monitoring instruments is quite diverse and usually reflects upon the requirements for sensitivity, specificity, portability, or speed of analysis. Gas-monitoring intruments may be used for fixed area monitoring, portable area monitoring or leak detection, and occasionally for personal monitoring. A recent reveiw references a number of analytical techniques and portable instruments for sampling and analysis of common pollutants, including NO,, SO,, and organic compounds ( H I ) . Interest in chemiluminescence analysis of gaseous compounds has grown in the past few years. Chemiluminescence instruments are described for detection of airborne SO2 (H2, H3), NOz and peroxyacetyl nitrate (PAN), ( H 4 ) , NO,, ethylene, and N-nitrosoamine (H5),and ozone (H6). A number of automated continuous monitoring instruments have been developed that use diffusion scrubbers with a thin anion exchanger membrane or a microporous hydrophobic membrane for sampling and a scrubbing liquid flowing in a narrow annular gap outside the membrane. A constant fraction of the analyte gas is collected in the liquid and a number of reagents can be added to the effluent liquid for specific determination of the compounds of interest. Instruments of this type have been tailored for the detection of nitric acid in air ( H 7 ) ,formaldehyde, SOz, and hydrogen in air. peroxide (H8) Sensitive portable gas chromatographs continue to be useful for a variety of applications. The Photovac 10S50 portable photoionization GC was evaluated for monitoring organic vapors, including benzene, toluene, bromo- and chlorobenzene, o-xylene, nine halomethanes, ethanes, and ethylenes at low (ambient) levels in air (H9). A sensitive portable GC with data retrieval capabilities and communication capabilities was described for remote surveillance on gases and vapors in plants (HIO). A dual capillary GC system was described for automated identification and analysis of workplace contaminants with thermal desorption and dual FID detectors ( H I I ) . For the determination of hydrocyanic acid in the work area, an automated GC was developed equipped with a flame ionization detector and two Chromosil310 columns with back-flushing capabilities (HI2). Another rapid automated GC method was published for the measurement of HCN and cyanogen (CN)z in air (H13). Eighteen instruments for measuring concentration of HN03 were compared, including FTIR, filter packs, transition flow reactors, annular denuders, and tunable diode laser absorption spectrometers ( H 1 4 ) . A newly designed semiautomatic portable gas analyzer, the Ftoring-1, was developed for the potentiometric determination of HF in workplace air (H15).
I. PARTICULATES The three main types of particulates of concern in the air are dust, mist, and fume. Several papers on sampling strategy and several specific reviews have been published (11-18). Sampling of particulates may be directed at determining the size, size distribution, total mass, and/or specific chemical identification. The sampling trains consist of a proble or inlet, particulate collector, and a pump. The particulate collector may consist of one or a combination of devices such as a filter, sorbent tube, impinger, cyclone, or impactor. Dust particles and particulates, in general, are classified as respirable and nonrespirable. Those that are deposited in the lung are said to be respirable while those that are so large they cannot enter the lung are removed in the upper respiratory passage and considered nonrespirable. If a sample is taken to determine the level of concentration of a substance, the procedure is usually to pass the air through a suitable filter; if more detailed information is desired about the particle size of the chemical, then usually a cyclone, impactor, or various combinations are used to collect the contaminant of interest. Prodi et al. describe a personal sampler for the separation of aerosol particles into the size ranges >lo, 3.5-10, and
