ACETONE Method no.: 69 Matrix: Air Target concentration: 1000 ppm (2375 mg/m3) (OSHA PEL) Procedure: Air samples are collected by drawing known volumes of air through standard size sampling tubes containing 130 mg of Carbosieve S-III (carbon based molecular sieve) adsorbent in the front section and 65 mg in the back section. The samples are desorbed with 1% dimethylformamide in carbon disulfide, in the presence of magnesium sulfate, and analyzed by GC with FID detection. Recommended air volume and sampling rate: 3 L and 0.05 L/min Reliable quantitation limit: 2.0 ppm (4.7 mg/m3) Standard error of estimate at the target concentration: 8.16% (Section 4.7) Status of method: Evaluated method. This method has been subjected to the established evaluation procedures of the Organic Methods Evaluation Branch. Date: March 1988 Chemist: Kevin Cummins Organic Methods Evaluation Branch OSHA Analytical Laboratory Salt Lake City, Utah 1 of 17 T-69-FV-01-8803-M 1. General Discussion 1.1 Background 1.1.1 History The previous OSHA method for sampling acetone is essentially the NIOSH method for sampling organic vapors (Ref. 5.1). In that method air samples are collected on coconut shell charcoal and analyzed by GC/FID following desorption with carbon disulfide. One of the major limitations of the NIOSH method is the poor stability of acetone and other ketones on charcoal (Refs. 5.2 - 5.6). Catalytic oxidation and irreversible adsorption (chemisorption) of ketones on the surface of charcoal is thought to account for the low recovery (Ref. 5.3). This effect is most pronounced for samples collected at high relative humidity (Ref. 5.2). Alternative sampling methods have been employed to improve the storage stability of ketones collected on an adsorbent surface. Sample tubes packed with either silica gel (Ref. 5.5) or Ambersorb XE-347 (Rohm & Haas, Philadelphia, PA) (Ref. 5.6), a synthetic, carbonaceous molecular sieve adsorbent, have been used to collect 2-butanone with improved sample stability. Collection of air samples on Ambersorb XE-348, a slightly polar type of carbonaceous molecular sieve material, results in improved storage stability of acetone, 2-butanone, methyl isobutyl ketone, cyclohexanone, and isophorone (Ref. 5.2). Pretreatment of coconut shell charcoal with hydroquinone has been shown to slightly improve the stability of cyclohexanone upon storage (Ref. 5.3). Carbosieve S-III (Supelco, Inc., Bellefonte, PA) was used in this evaluation for the collection of acetone. This material is a carbonaceous molecular sieve adsorbent similar to the Ambersorb XE-347 and XE-348. The stability of acetone collected on this adsorbent is superior to that observed with coconut shell charcoal (Section 4.5) and comparable with Ambersorb XE-348 (Ref. 5.2). The sampling capacity of Carbosieve S-III for acetone is greater than both coconut shell or petroleum-based charcoal. It is also greater than that of Ambersorb XE-347, Ambersorb XE-348, and Purasieve, which is a synthetic carbon- based material manufactured by Union Carbide (Section 4.10). Occupational exposures to acetone alone are uncommon. Typically acetone is used with other solvents. It would be advantageous if Carbosieve S-III could be used to collect a variety of other solvents simultaneously with acetone. The sample capacities of Carbosieve S-III for some common solvents have been found to equal or exceed that of coconut shell charcoal (Section 4.10). Common ketones and some esters which are known to be unstable when collected on charcoal are also excellent candidates for evaluation with Carbosieve S-III (Ref. 5.3.). 1.1.2 Toxic effects (This section is for information only and should not be taken as the basis of OSHA policy.) Acetone is a relatively non-toxic solvent. An oral LD50 of 10.7 mL/kg in the rat has been reported. Inhalation of the vapor may produce headaches, fatigue, excitement, and bronchial irritation. (Ref. 5.8) High vapor concentrations will produce anesthesia. There are no confirmed reports of serious effects produced from chronic exposure to low levels of acetone. Prolonged or repeated skin exposure can dry and defat the skin and lead to dermatitis. Direct contact of acetone with the eye may produce temporary corneal injury. (Ref. 5.9) 1.1.3 Workplace exposure Acetone is used as a chemical intermediate and solvent. In 1986, approximately 1.94 billion pounds of acetone were produced in the United States (Ref. 5.10). Approximately one-third of the total amount produced in the United States is used as an intermediate in the production of methacrylates via the acetone cyanohydrin process (Ref. 5.9). Another 15% is used as a solvent for vinyl or acrylic resins, alkyd paints, varnishes and lacquers, oils, waxes, plastics, and rubber cements. Approximately 20% of the total U.S. acetone production is used to produce a variety of common solvents. Methyl isobutyl ketone, methyl isobutyl carbinol, mesityl oxide, hexylene glycol, and isophorone are all derived from reactions in which the initial step involves the self condensation of acetone (Ref. 5.9). Acetone is also used as a chemical intermediate in the production of Bisphenol A, as a 2 of 17 T-69-FV-01-8803-M solvent and chemical intermediate in the pharmaceutical industry, and as a solvent in the processing of cellulose acetate. 1.1.4 Physical properties (Ref. 5.9 unless otherwise noted) CAS no.: 67-64-1 molecular weight: 58.08 appearance: colorless liquid odor: pungent, aromatic-like melting point: -123.5EC boiling point at 1 atm: 56.1EC vapor pressure at 20EC: 24.7 kPa (185 mm Hg) specific gravity: 0.783 (at 20EC relative to water at 4EC) solubility: miscible with water, alcohols, chloroform, ether, and most oils (Ref. 5.8) flash point (closed cup): -18EC autoignition temperature: 538EC flammable (explosive) limits: lower 2.1 (% by volume in air) upper 13 synonyms: 2-propanone, dimethyl-ketone, beta-keto-propane, pyroacetic acid formula: CH3COCH3 The analyte air concentrations throughout this method are based on the recommended sampling and analytical parameters. Air concentrations listed in ppm are referenced to 25EC and 760 mm Hg. 1.2 Limit defining parameters 1.2.1 Detection limit of the analytical procedure The detection limit of the analytical procedure is 0.71 ng per injection. This is the amount of analyte which is readily detectable in the presence of the solvent front. (Section 4.1.) 1.2.2 Detection limit of the overall procedure The detection limit of the overall procedure is 14.1 µg per sample (2.0 ppm or 4.7 mg/m3). This is the amount of acetone spiked on the sampling device which allows recovery of an amount of analyte equivalent to the detection limit of the analytical procedure. (Section 4.2) 1.2.3 Reliable quantitation limit The reliable quantitation limit is 14.1 µg per sample (2.0 ppm or 4.7 mg/m3). This is the smallest amount of analyte which can be quantitated within the requirements of a recovery of at least 75% and a precision (±1.96 SD) of ±25% or better. (Section 4.3) The reliable quantitation limit and detection limits reported in the method are based upon optimization of the instrument for the smallest possible amount of the analyte. When the target concentration of the analyte is exceptionally higher than these limits, they may not be attainable at the routine operating parameters. 1.2.4 Instrument response to the analyte The instrument response over the concentration range of 0.5 to 2 times the target concentration is linear. (Section 4.4) 1.2.5 Recovery The recovery of acetone from samples used in a storage test was equal to or greater than 86.7% when the samples were stored at about 23EC over a 17-day storage period. This value is determined from the equation of the regression line of the graphed storage data, at the 17th day, for ambient storage of samples collected at high relative humidity (Section 4.5). The recovery of the analyte from the collection medium during storage must be 75% or greater. 3 of 17 T-69-FV-01-8803-M 1.2.6 Precision (analytical procedure) The pooled coefficient of variation obtained from replicate determinations of analytical standards at 0.5, 1 and 2 times the target concentration is 0.018. (Section 4.6) 1.2.7 Precision (overall procedure) The precision at the 95% confidence level for the 17-day ambient temperature storage test is ±14.6% (Section 4.7). This includes an additional ±5% for sampling error. The overall procedure must provide results at the target concentration that are ±25% or better at the 95% confidence level. 1.2.8 Reproducibility Six samples collected from a test atmosphere and a draft copy of this procedure were given to a chemist with this evaluation. The samples were analyzed after 59 days of storage at 5EC. No sample deviated from its theoretical value by more than the precision reported in Section 1.2.7. (Section 4.8) 1.3 Advantages This sampling method has a higher sampling capacity and results in improved storage stability for acetone over the existing coconut shell charcoal method. 1.4 Disadvantages 1.4.1 The Carbosieve S-III sampling tubes are slightly more expensive than coconut shell charcoal sampling tubes. 1.4.2 The fine mesh size of Carbosieve S-III (60/80) results in a greater pressure drop across the sample tube than occurs with the conventional coconut shell charcoal sampling tube. At a sampling rate of 0.2 L/min the pressure drop across the tube is 10 in. of water. 2. Sampling Procedure 2.1 Apparatus 2.1.1 Samples are collected with a personal sampling pump that can be calibrated to within ±5% of the recommended flow rate with the sampling device attached.