Samples of water exposed to surfaces coated with a commercial coal tar have been analyzed for polycyclic aromatic hydrocarbons by gas chromatography-mass spectrometry. Concentrations of representative compounds total several hundred micrograms per liter in leachate from test panels freshly coated with coal tar and tenths of a microgram per liter in leachate from a 5-year-old storage tank coated with the same material.Coal tar is a complex mixture of polycyclic aromatic hydrocarbons (PAH), which includes a number of toxic substances listed as priority pollutants by the Environmental Protection Agency (1 1. These compounds are ubiquitous at low levels in the human environment. Concern for their presence in waste effluents is partially motivated by the desire to limit contamination of drinking water. However, such reasoning is in conflict with the accepted use of coal tar to prevent corrosion in water distribution systems. In New York State, coal tar is commonly applied to steel storage tanks and to cement-lined ductile iron,pipes used in water distribution (2). T o determine the potential for contamination of water by commercial coal tar materials, samples of water exposed to coal tar coated surfaces have been analyzed by gas chromatography-mass spectrometry (GC-MS). Thus, this paper focuses on a specific aspect of water contamination during the process of supply and distribution, which is currently under scrutiny ( 3 ) . ExperimentalSamples. Two types of samples were taken for analysis. Forty-liter field samples were collected in duplicate at the inlet and outlet of a 12 000-gal (45 400 L) storage tank. The tank interior had a commercial coal tar coating which was 5 years old but which still appeared in good condition.Similarly, 40-L laboratory samples were prepared from tap water exposed to test panels coated with the same coal tar as used on the storage tank. Blank tap water samples were run as a control. The test panels were prepared according to the manufacturer's specifications: cold rolled steel was sand blasted to remove mill scale, cleaned in distilled water followed by acetone to remove dirt and grease, given one coat of the manufacturer's surface primer, dip coated in coal tar a t 240 "C, and cured by drying in open air for 1 week. The test panels were then immersed in tap water a t room temperature. The ratio of volume to panel surface area was 4 gal/ft2 (160 L/m2), a value representative of storage tanks in New York State. After immersion for 1 week, the test panels were removed.Procedures. Neutral organic compounds were extracted from the water samples by adsorption on a lipophilic resin, XAD-2, which has been shown to adsorb neutral organic compounds from water with high efficiency ( 4 ) . The XAD resin was precleaned by extraction in a Soxhlet apparatus with acetone, methanol, and dichloromethane for several days each.T h e water sample was pumped through a 1-pm glass fiber filter to remove particulates and then through a column of XAD-2 resin (1.2 cm X 10 cm long). Masterflex peristaltic pumps were...
DoE methods use probability and statistics to define the minimum number of experiments needed to identify significant cause-and-effect relationships between a given number of factors and one or more responses. Mathematically, DoE methods are well developed to identify efficient experimental designs. The three major components of DoE are design, analysis, and optimization. The strength of Design-Expert is the ease with which these tasks can be carried out and the usefulness of infor-
uid-liquid extraction of THMs from water samples. The feasibility of quantitative solvent extraction of THMs from treatment plant GAC samples is suggested by favorable recoveries of volatile organics eluted by carbon disulfide from GAC traps (15)(16)(17). Selection of methanol as the solvent permits use of the electron capture detector for gas chroma-0003-2700/86/0358-1817S01.50/0 tographic analysis, without concentration of the sample extract to enhance analytical sensitivity. Methanol also has the advantage that it is miscible with residual water trapped in the pores of GAC samples from a pilot column or treatment plant. However, the relatively high boiling point of methanol compared to the THMs precludes use of the Soxhlet apparatus.Ultrasonic solvent extraction was chosen as an alternative, since numerous reports have been made that it results in higher recoveries of organics in niuch less time than required for Soxhlet extraction (18)(19)(20)(21)(22)(23).EXPERIMENTAL SECTION Chromatographic Analysis. Samples are analyzed for THMs on a Perkin-Elmer Sigma 1 gas chromatograph ¿quipped with a Model 4990 autosampler and 63Ni electron capture detector. THMs are separated on a 2-mm-i.d. x 1.8-m-long column packed with 80/100 mesh Chromosorb 101, operated isothermally at 165 °C, with the injector and detector blocks maintained at 225 °C and 300 °C, respectively. The carrier gas (argon-5% methane, 99.999% purity) is supplied at 11 mL/min to the column and at 34 mL/min as makeup to the detector. Although our instrument
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