ANALYTICAL SCIENCES VOL. 7 SUPPLEMENT 1991 1029 SPECIES ANALYSIS OF INORGANIC COMPOUNDS IN WORKROOM AIR BY ATOMIC SPECTROSCOPY SIRI HETLAND', IVAR MARTINSEN', BERNARD RADZIUK2 and YNGVAR THOMASSEN' 1 National Institute of Occupational Health , P.O.Box 8149 DEP, N-0033 Oslo 1, Norway 2 Department of Applied Research , Bodenseewerk Perkin-Elmer GmbH, P.O.Box 10 11 64, D-7770 Uberlingen, Germany Abstract - Sampling methods for the determination of volatile inorganic compounds in workroom air are described. The main factor affecting the adsorption capacity of activated charcoal for iron pentacarbonyl is air flow rate. Nickel tetracarbonyl is collected quantitatively at flow rates of up to 11/min if the volume of air sampled does not exceed 1001. Arsine, phosphine and stibine are collected quantitatively from air by use of a double filter air cassette Silver nitrate impregnated backing pads are shown to trap the hydrides with better than 99.9% efficiency. Several atomic spectroscopic methods have been applied to the determination of these volatile species, with electrothermal atomic absorption and inductively coupled plasma atomic emission spectroscopy being preferred. Concentrations of the hydrides in various workroom atmospheres were found to be well below the Threshold Limit Values. Key words arsine, stibine, phosphine, iron pentacarbonyl, nickel tetracarbonyl, species analysis The term chemical species refers to a specific form (monatomic or molecular) or configuration in which an element can occur, or to a distinct groups of atoms consistently present in different compounds or matrices . The individual species may be gaseous, solid, crystalline or in solution depending upon the nature of the sample. A parent species is an unchanging component (e.g. CH3Hg+), a matrix species is a combined form (e.g. CH3HgL, with L-OH, protein etc.) while an analyte species is the form (e.g. CH3HgC1) detected by the analytical method used. Species analysis( sPeciation) is the identification and quantification of these three types of species. Species distribution describes the abundance or fractional occurrence, species reactivity is related to characteristic reactions, responses or effects while species transformation is the conversion of one species to another. The above definitions have recently been suggested for use in "speciation'' studies {1J. Exposure of workers in occupational settings is most frequently to inorganic compounds present mainly in particulate or volatile forms (gases). The recently increasing interest in the occurrence of organometallie compounds in the work environment has also led to a demand for new sampling and analytical methods with adequate selectivity and sensitivity. An excellent review of this topic has been published in Arbete och Halsa [2]. The Threshold Limit Values( TLV's) which have been established in most countries refer to airborne concentrations of substances and represent conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse health effects. These limits are neither fine lines between safe and dangerous concentrations nor a relative index of toxicity. In spite of the fact that serious injury is not believed likely as a result of exposure to the threshold limit concentrations, the best preventive practice is to maintain concentrations of all atmospheric contaminants as low as possible. Moreover, the potential health hazard posed by chemical substances in inhaled air depends mainly on the parent species. While most guidelines are set for the total amounts of elements, some threshold limit values for parent species have been recommended as well. The most important inorganic substances for which speciation is needed are listed in Table 1. Of the species listed in Table 1, hydrogen fluoride occurs the most frequently in workroom air. This compound is emitted during production of primary aluminium metal and is one of the important components in the evaluation and monitoring of the exposure of workers in the aluminium industry. The preferred method for determination of HF in air is trapping on sodium hydroxide soaked filters followed by analysis using an ion selective electrode. The carbonyls of iron and nickel are highly toxic compared with other compounds of these metals which are found in workroom air. These volatile compounds are, however, only generated under particular conditions, e.g. during 1030 production of nickel metal using the carbonyl process. There has arisen some concern that these compounds may also be produced in environments with elevated temperatures and high concentrations of c arbon monoxide in the presence of iron and nickel metal particles. TABLE 1. TLV's for some volatile inorganic species Volatile hydrides of arsenic, antimony and phosphorus are formed during certain industrial processes. During charging processes in the manufacture of lead batteries nascent hydrogen is generated which reacts with traces of antimony and arsenic in the sulphuric acid solutions to form stibine and arsine. The reaction of phosphides , arsenides and antimonides with atmospheric humidity forming the elemental hydrides may occur both in the metallurgical and metal working industries. Sampling of workroom air in which these parent species are present in combination with particulate forms of the same elements requires methods for the separation and quantitative collection of the different species. The air sampling is accordingly performed by means of various types of filters for particulates or involatile aerosols, while the volatile compounds are collected on adsorbents [3]. Various analytical techniques may be used to detect the analyte species collected on the adsorbent or filter media. After sample preparation with inorganic acids these species will be present in aqueous solutions which are well suited for quantitative measurements by, for example, inductively coupled plasma atomic emission spectrometry or atomic absorption spectrometry either with flame or graphite tube atomization. The presently available sampling procedures do not make possible the separate measurement of the above mentioned carbonyls and hydrides in general occupational settings. In the present study, sampling procedures based on the combination of a membrane filter with a tube containing activated charcoal adsorbent and on a two-filter air sampling cassette have been investigated. Both atomic absorption and atomic emission spectroscopic procedures have been developed for quantification of these species in a variety of occupational environments. EXPERIMENTAL Apparatus A Perkin-Elmer Zeeman 5100 atomic absorption spectrometer equipped with an HGA 600 graphite atomizer, an AS-40 automatic sampler and hollow cathode and electrodeless discharge lamps was used . Pyrolytical graphite coated tubes were applied throughout the study. Atomic emission measurements were performed using a Perkin-Elmer 5500 Inductively Coupled Plasma Atomic emission spectrometer. A peristaltic pump (0.75 mIJmin) introduced the sample solution into a cross-flow nebulizer operated at an argon flow of 1.0 llmin which was controlled by a mass-flow meter . Additional argon was supplied to the quartz torch (131/min). The plasma was maintained at 1.2 kW applied with a frequency of 27.2 MHz. For the determination of the adsorption capacity and breakthrough time for air sampling , a manifold was used in which up to 10 units could be exposed simultaneously to gas mixtures or real workroom atmospheres . Air was sampled using Personal Sampling Pumps with fixed flow-rates of 0.1-2.0 1/mm. Reea ents Commercial adsorbent tubes (SKC , Pittsburg, PA) packed with activated carbon were used. The tubes were composed of two sections , the first containing 100 mg and the second 50 mg. Measurement on adsorption capacity could be made by analysing the material in the two sections separately . Activated Carbon (Fluka) was ground and the 0.6-1.2 mm fraction was boiled with 65% nitric acid for 1 h, five times in succession . Th e carbon was then washed with demineralized water , air-dried and reactivated in air at 450 °C for 30 min. This procedure reduced the concentrations of iron and nickel (see Table 3). Cellulose acetate membrane filters with 0.8-pm pore-size and 37mm diameter were used for the collection of particulate matter from air. The cellulose backing pad which supports the membrane filter in the standard air sampling cassette (Nucleopore) was dipped in a solution containing 2.5% AgN03 by weight and oven dried at 75 C overnight. This double filter system was used to collect particulates and hydrides simultaneously. Procedures for dissolution extraction The cellulose membrane filters were dissolved and the charcoal fractions extracted with nitric acid [4J. The silver nitrate impregnated backing pads were extracted with 2.5 ml 65% HNp3 ANALYTICAL SCIENCES VOL. 7 SUPPLEMENT 1991 1031 at 100° C for 1 h, and the final solution was diluted to 25 ml with demineralized water . The results were corrected for the volume of undissolved material (activated charcoal and cellulose fibers) by preparing standard solutions containing the same amount of charcoal and a backing pad, respectively. RESULTS AND DISCUSSION Collection efficiencies-carbonyls Charcoal-filled collection tubes were exposed to various volumes of gas mixture containing the two metal carbonyls at TLV's concentrations at various flow rates in order to assess adsorption efficiency. Table 2 gives a summary of the adsorption capacity data. TABLE 2. Adsorption capacity