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A surfaceand a ground-water matrix were spiked with 87 volatile organic compounds (VOCs) to achieve a theoretical concentration of 0.5 microgram per liter for most VOCs. Five replicate spike samples from each water matrix were stored and analyzed at selected time intervals up to 216 days. To assess daily analytical variability, three replicate continuing calibration verification standards were analyzed at the same times as the spiked water matrices. The results of this study provide information about the stability of low concentrations of VOCs in water samples preserved with hydrochloric acid, chilled at 4 degrees Celsius, and kept in the dark prior to analysis. This report describes the study design and presents the results of samples analyzed on day 0, 14, 28, 37, 47,56,112, 156, and 216. INTRODUCTION Due to unforeseen technical difficulties with analytical equipment used for volatile organic compound (VOC) analyses at the U.S. Geological Survey (USGS) National Water-Quality Laboratory (NWQL) in Arvada, Colorado, approximately 150 to 200 VOC samples in the summer of 1996 exceeded the maximum U.S. Environmental Protection Agency (USEPA) preanalytical holding-time requirement of 14 days (Munch, 1995). The maximum holding time for the water samples that exceeded 14 days was 41 days, with a median holding time of 27 days. The samples were preserved in the field with hydrochloric acid (HC1), kept chilled at 4°C, and analyzed as soon as the analytical equipment became operational. These data were subsequently released. However, the quality of the data was uncertain because little information exists on the stability of low concentrations of VOCs in water samples preserved with HC1 that are held beyond 14 days. It is unknown how 14 days was chosen by the USEPA for a maximum pre-analytical holding time for VOC analysis. Maskarinec and others (1990) addressed the holding-time issue and suggested that the maximum holding time of VOCs in water could be increased to at least 56 days if the water samples are preserved with HC1 to a pH of 2.0 or less and chilled at 4°C. However, the concentrations of VOCs used in Maskarinec's preservation study, 100 |J.g/L, were much higher than those found in most environmental samples collected by the USGS and submitted for analysis at the NWQL. Water samples submitted to the NWQL during and after the timeframe that the 150 to 200 VOC samples exceeded the USEPA's holding time requirement were analyzed for 87 VOCs (table 1). The 87 VOCs were divided into two groups target analytes (55 compounds) and other analytes (32 compounds). The target analytes were selected because of their known human-health and (or) aquatic-life concern or because of their high frequency of occurrence in surface and ground water (John Zogorski, USGS, written commun., 1994). The other analytes were included because they are on the USEPA's list for analysis using their revised method for drinking-water samples (Eichelberger and Budde, 1989). Introduction Table 1 . Volatile organic compounds analyzed during this study [Compounds are identified by the following: PCODE, U.S. Geological Survey data base parameter code; CAS no., Chemical Abstract Services number; IUPAC, International Union of Pure and Applied Chemistry] PCODE CAS no. IUPAC compound name (chemical formula) (common name(s)) PCODE CAS no. IUPAC compound name (chemical formula) (common name(s)) Target analytes 34030 32101 50002 34413 77342 34301 34311 39175 34418 82625 32105 77651 34536 34566 34571 34668 34496 32103 34501 77093 34546 34423 71-43-2 75-27-4 593-60-2 74-83-9 104-51-8 108-90-7 75-00-3 75-01-4 74-87-3 96-12-8 124-48-1 106-93-4 95-50-1 541-73-1 106-46-7 75-71-8 75-34-3 107-06-2 75-35-4 156-59-2 156-60-5 75-09-2 Benzene (C6H6) Bromodichloromethane (CHBrCl2) (dichlorobromomethane) Bromoethene (C2H3Br) (vinyl bromide) Bromomethane (CH3Br) (methyl bromide) n-Butylbenzene (Ci0Hi4) (1-phenylbutane) Chlorobenzene (C6H5C1) (monochlorobenzene) Chloroethane (C2H5C1) (ethyl chloride) Chloroethene (C2H3C1) (vinyl chloride) Chloromethane (CH3C1) (methyl chloride) 1 ,2-Dibromo-3-chloropropane (C3 H5Br2Cl) (dibromochloropropane, DBCP) Chlorodibromomethane (CHBr2Cl) (chlorodibromomethane) 1,2-Dibromoethane (C2H4Br2) (ethylene dibromide, EDB) 1,2-Dichlorobenzene (C6H4C12) (o-dichlorobenzene) 1 ,3-Dichlorobenzene (C6H4C12) (m-dichlorobenzene) 1 ,4-Dichlorobenzene (C6H4C12) (p-dichlorobenzene) Dichlorodifluoromethane (CC12F2) (CFC 12) 1,1-Dichloroethane (C2H4C12) (ethylidene chloride) 1,2-Dichloroethane (C2H4C12) (ethylene dichloride) 1,1-Dichloroethene (C2H2C12) (vinylidene chloride) cis1 ,2-Dichloroethene (C2H2C12) ((Z)-l ,2-dichloroethene) t rans1 ,2-Dichloroethene (C2H2C12) ((E)1 ,2-dichloroethene) Dichloromethane (CH2C12) 34541 34704 34699 77135 85795 77128 50004 34371 39702 34396 50005 78032 34010 77223 34696 81577 34210 34215 77224 34475 32102 78-87-5 10061-01-5 10061-02-6 95-47-6 108-38-3 106-42-3 100-42-5 637-92-3 100-41-4 87-68-3 67-72-1 994-05-8 1634-04-4 108-88-3 98-82-8 91-20-3 108-20-3 107-02-8 107-13-1 103-65-1 127-18-4 56-23-5 1 ,2-Dichloropropane (C3HgCl2) (propylene dichloride) cis-\ ,3-Dichloropropene (C3H4C12) ((Z)1 ,3-dichloropropene) trans1 ,3-Dichloropropene (C3H4C12) ((E)1 ,3-dichloropropene) 1.2-Dimethylbenzene (C8H 10) (o-xylene) 1 ,3-Dimethylbenzene (C8Hi0) (m-xylene) and 1 ,4-Dimethylbenzene (C8H 10) (p-xylene) Ethenylbenzene (C8H8) (styrene) 2-Ethoxy-2-methylpropane (CgH^O) (ethyl ferf-butyl ether, ETBE) Ethylbenzene (C8 H 10) (phenylethane) 1 , 1 ,2,3,4,4-Hexachloro1 ,3-butadiene (C4C16) (hexachlorobutadiene) 1,1,1 ,2,2,2-Hexachloroethane (C2C16) (carbon hexachloride) 2-Methoxy-2-methylbutane (C6H 14O) (tert-amyl methyl ether, TAME) 2-Methoxy-2-methylpropane(C5 H 12O) (methyl t erf-butyl ether, MTBE) Methylbenzene (C7H8) (toluene) ( 1 -Methylethyl)benzene (C9H 1 2) (isopropylbenzene) Naphthalene (Ci0H8) 2,2'-Oxybis[propane] (C6H 14O) (diisopropyl ether, DIPE) 2-Propenal (C3H4O) (acrolein) 2-Propenenitrile (C3H3N) (acrylonitrile) n-Propylbenzene (C9Hj 2) (1 -phenylpropane) Tetrachloroethene (C2C14) (perchloroethene, PCE) Tetrachloromethane (CCL) (methylene chloride) (carbon tetrachloride) Study Design and Analytical Results Used to Evaluate Stability of VOCs in Water Matrices Table 1 . Volatile organic compounds analyzed during this study Continued [Compounds are identified by the following: PCODE, U.S. Geological Survey data base parameter code; CAS no., Chemical Abstract Services number; IUPAC, International Union of Pure and Applied Chemistry] PCODE CAS no. IUPAC compound name (chemical formula) (common name(s)) PCODE CAS no. IUPAC compound name (chemical formula) (common name(s)) 32104 75-25-2 77652 76-13-1 77613 87-61-6 34551 120-82-1 34506 71-55-6 34511 79-00-5 81555 108-86-1 77297 74-97-5 81595 78-93-3 77041 75-15-0 77275 95-49-8 77277 106-43-4 78109 107-05-1 30217 74-95-3 73547 110-57-6 77173 142-28-9 77170 594-20-7 77168 563-58-6 77353 98-06-6 81607 109-99-9 77220 611-14-3 73570 97-63-2 Tribromomethane (CHBr3) (bromoform) Target analytes Continued 39180 79-01-6 l,l,2-Trichloro-l,2,2-trifluoroethane 34488 75-69-4 (C2C13F3)(CFC113) 1.2.3-Trichlorobenzene(C6H3C!3) 32106 67-66-3 1.2.4-Trichlorobenzene (C6H3C13) 1.1.1-Trichloroethane (C2H3C13) (methyl chloroform) 1.1.2-Trichloroethane (C2H3C13) (vinyl trichloride) Bromobenzene (C6H5Br) (phenyl bromide) Bromochloromethane (CH2BrCl) (methylene chlorobromide) 2-Butanone (C4H8O) (methyl ethyl ketone, MEK) Carbon disulfide (CS2) 77443 96-18-4 77222 95-63-6 Other analytes 77103 591-78-6 77424 74-88-4 77356 99-87-6 81597 80-62-6 78133 108-10-1 126-98-7 96-33-3 1 -Chloro-2-methyIbenzene (C7H7C1) (o-chlorotoluene) 1 -Chloro-4-methylbenzene (C7H7C1) (p-chlorotoluene) 3-Chloro-l-propene (C3H5C1) (allyl chloride) Dibromomethane (CH2Br2) (methylene bromide) trans1,4-Dichloro-2-butene (C4H6C12) ((E)-1,4-dichloro-2-butene) 1,3-Dichloropropane (C3H6C12) (trimethylene dichloride) 2,2-Dichloropropane (C3H6C12) 1,1 -Dichloropropene (C3H4C12) (l,l-Dirnethylethyl)benzene(C 10H 14) 49999 488-23-3 (terf-butylbenzene) l,4-Epoxybutane(C4H8O) 50000 527-53-7 (tetrahydrofuran) l-Ethyl-2-methylbenzene(C9H 12) 77221 526-73-8 (2-ethyltoluene) Ethyl 2-methyl-2-propenoate (C6H 10O2) 77226 108-67-8 (ethyl methacrylate) 81593 49991 77350 135-98-8 81576 60-29-7 81552 67-64-1 77562 630-20-6 34516 79-34-5 Trichloroethene (C2HC13) (trichloroethylene, TCE) Trichlorofluoromethane (CC13F) (CFC11) Trichloromethane (CHC13 ) (chloroform) 1.2.3-Trichloropropane (C3H5C13) (allyl trichloride) 1.2.4-Trimethylbenzene (C9H 12) (pseudocumene) 2-Hexanone (C6H 12O) (butyl methyl ketone, MBK) lodomethane (CH3I) (methyl iodide) 1 -Isopropyl-4-methylbenzene (CirjHi4) (p-i sopropy Itoluene) Methyl 2-methyl-2-propenoate (C5 H8O2) (methyl methacrylate) 4-Methyl-2-pentanone (C6H 12O) (isobutyl methyl ketone, MIK) 2-Methyl-2-propenenitrile(C4H5N) (methyl acrylonitrile) Methyl-2-propenoate (C4H6O2) (methyl acrylate) (l-Methylpropyl)benzene (C 10H 14) (sec-butylbenzene) 1,1'-Oxybisethane (C4H 10O) (diethyl ether) 2-Propanone (C3H6O) (acetone) 1,1,1,2-Tetrachloroethane (C2H2C14) 1,1,2,2-Tetrachloroethane (C2H2C14) 1.2.3.4-Tetramethylbenzene (C 10H 14) (prehitene) 1.2.3.5-Tetramethylbenzene (C 10H 14) (isodurene) 1,2,3-Trimethylbenzene (C9H 12) (hemimellitene) 1,3,5-Trimethylbenzene (C9Hj2) (mesitylene)

Study design and analytical results used to evaluate stability of volatile organic compounds in water matrices