Environ. Sci. Technol. 1987,21, 110-1 12
(11) Simoneit, B. R. T.; Mazuruek, M. A. Atmos. Environ. 1982, 16, 2139. (12) Granstein, W. C.; Cromack, K., Jr.; Sollins, P. Science (Washington,D.C.) 1977, 198, 1252. (13) Hatakeyama, S.; Tanonaka, T.; Weng, J.; Bandow, H.; Takagi, H.; Akimoto, H. Enuiron. Sci. Technol. 1985,19, 935.
Received for review January 24,1986. Revised manuscript received September 19, 1986. Accepted September 25, 1986. Although the information in this paper has been funded wholly or in part by the U S . Environmental Protection Agency under Assistance Agreement CR-807864-02to NCITR at UCLA, it does not necessarily reflect the views of the Agency, and no official endorsement should be inferred.
Gas Chromatography/Mass Spectrometry Identification of Cyclohexene Artifacts Formed during Extraction of Brine Samples James A. Campbell,* Mark A. LaPack, Thomas L. Peters, and Tim A. Smock Dow Chemical Company, Midland, Michigan 48640
In the acidic extraction of brine samples, peaks appeared in the total ion chromatogram characteristic of halogenated cyclohexanes. In addition, the halogenated cyclohexanes are sufficiently volatile and nonpolar that they should be readily detected by volatile analysis procedures. Since these compounds were not detected by gas chromatography/mass spectrometry analysis of the volatiles, it was postulated that the halogenated cyclohexanes were actually artifacts formed during the acidic extraction procedure. The results indicate that the halogenated cyclohexanes are formed by the reaction of cyclohexene, present as an inhibitor in the methylene chloride, and the various halogens in the brine.
Introduction The use of methylene chloride for the extraction of organic components, specifically amines, has led to the formation and identification of artifacts. Beckett and Ali (1) reported the interaction of methylene chloride with various antihistaminic drugs and identified the artifacts as their chloromethochlorides. Franklin et al. (2) identified cyanogen chloride as an impurity in methylene chloride, and its presence resulted in the formation of corresponding nitriles. In addition, pethidine and dexomethorphan interaction products have been identified by Vaughn (3) as their chloromethochlorides. The standard Environmental Protection Agency (EPA) method for the analysis of extractable aqueous organic pollutants involves the use of methylene chloride as a solvent and liquid-liquid extractors. This method, EPA Method 625, has been employed in our laboratory for the isolation, concentration, and identification of trace organic chemicals in aqueous matrices ( 4 ) . In our acidic extraction of brine samples, peaks appeared in the total ion chromatograms with characteristic ions indicative of halogenated cyclohexanes. Components identified include cis-1-bromo-2-cyclohexanol and cis-lbromo-2-chlorocyclohexane, cis-2-iodocyc1ohexano1, dibromocyclohexane, and cis-1-chloro-2-iodocyclohexane. These results were very surprising in view of the fact that previous extractions with other solvents such as diethyl ether and hexane showed no evidence of these types of components. In addition, the halogenated cyclohexanes are sufficiently volatile and nonpolar that they should be
* Address correspondence to this author at his present address: Battelle-Northwest, Richland, WA 99352. 110
Environ. Sci. Technol., Vol. 21, No. 1, 1987
readily detected by volatile analysis (EPA Method 624) procedures. Since these compounds were not detected by gas chromatography/mass spectrometry (GC/MS) analysis of the volatiles, it was speculated that these components were not inherent in the sample but actual artifacts formed during the extraction procedure. In other words, these particular types of components had been found only in the methylene chloride extracts from this specific type of matrix, the heavy brines. It was postulated that these components were not originally present in the sample but actually formed by an addition reaction of the cyclohexene inhibitor in the methylene chloride and the halogens present in the brine. The objective of this work was then to determine the source of the artifacts formed during the extraction of the heavy brine samples with methylene chloride and, if found, to suggest methods for reducing the type of reactions taking place and the products being formed.
3
2
time lmin
I
Figure 1. Total ion chromatogram for cyclohexene-Inhibited methylene chloride extract of a brine sample. The GC/MS conditions were as follows: instrument, Hewlett-Packard 5996 GUMS; column, 30 m X 0.25 mm DB-5 fused silica, 0.25 hm film thickness; column temperature, 30 OC for 4 min, 30-300 OC at 10 deg/min, and 300 OC for 10 min; injection mode, l-hL splitless at 280 OC; carrier gas, He at 20 psig; interface, open split at 280 OC; source temperature, 220 OC; Torr; scan analyzer temperature, 220 OC; source pressure, 0.5 X rangelrate, 46-385 at 266 amuls; ionization mode, electron impact; electron multiplier, 1600 V.
0013-936X/87/0921-0110$01.50/0
0 1986 American Chemical Society
81
A
99
\
60
rnle I1
1
WA-ALLL 4
__.
c
8
12
16
20
24
28
time Imin.1
Figure 3. Total ion chromatogram for the cyclohexene-inhibited methylene chloride extract of a brine sample. 117, 106 0
'
119
198
\
11 80
60
100
120
140
160
180
200
rnle 81
/
100 r
C
60
80
100
120
140
160
180
200
220
240
mie
Flgure 2. (A) Mass spectrum for component 1 of Figure 1. The component is identified as cis -2-bromocyclohexanol. (B) Mass spectrum for component 2 of Figure 1. The component is identified as cis-1-bromo-2-chlorocyclohexane. (C) Mass spectrum for component 3 of Figure 1. The component is identified as dibromocyclohexane.
Experimental Section A 1-L portion of the brine sample was acidified with concentrated HC1 to pH 3 and extracted with cyclohexene-inhibited methylene chloride (Burdick and Jackson) overnignt in a liquid-liquid extractor. The extract was then concentrated to 1mL with Kuderna-Danish evapo-
rative-distillation techniques and analyzed by GC/MS. To mimic the natural brine solution, a synthetic brine sample was prepared by making 50 mL of a 1% solution of NaI and NaC1. This solution was then acidified with HC1 to pH 3 and refluxed with 50 mL of cyclohexene-inhibited methylene chloride (Burdick and Jackson) overnight. The methylene chloride layer was separated, concentrated to 1 mL, and analyzed by GC/MS. In addition, 50 mL of the synthetic brine was made acidic with HC1 to a pH of 3 and refluxed overnight with 50 mL of cyclohexene (Aldrich). The cyclohexene layer was separated from the aqueous layer, concentrated to 1 mL, and then analyzed by GC/MS with the same conditions. The synthetic brine was also refluxed with methylene chloride containing no cyclohexene (Fisher Scientific). The organic layer was separated, concentrated, and analyzed by GC/MS. Results and Discussion In Figure 1, a total ion chromatogram of a cyclohexene-inhibited methylene chloride extract of a brine sample is given. The peaks of interest have the mass spectra shown in Figure 2. These components have been identified as (A) cis-2-bromocyc1ohexano1,(B) cis-l-bromo-2chlorocyclohexane, and (C) dibromocyclohexane. No standards of these compounds were available, but the library matchups for identification indicate probabilities of >go%, In extraction and subsequent analysis of another brine sample, other addition reaction products involving cyclohexene were also tentatively identified. The total ion chromatogram for this sample is shown in Figure 3. The mass spectra for the peaks of interest are shown in Figure
Table I. Components Tentatively Identified in Extracts
cyclohexene-inhibited methylene chloride extract of brine
cyclohexene-inhibited methylene chloride extract of synthetic brine
cyclohexene extract of synthetic brine
chloroiodocyclohexane bromocyclohexanol bromochlorocyclohexane dibromocyclohexane iodocyclohexanol
chloroiodocyclohexane
chloroiodocyclohexane
Environ. Sci. Technol., Vol. 21, No. 1 , 1987
111
81 /
A
99
/
117
55
/
0 40
8
120
60
80
100
120
140
d e
160
180
200
220
240
rnle
Figure 4. (A) Mass spectrum for component 1 of Figure 3. The component is identified as 2-iodocyclohexanol. (B) Mass spectrum for component 2 of Figure 3. The component is identified as cis -1-chloro-2-iodocyclohexane.
4. These components have been tentatively identified as (A) 2-iodocyclohexanol and (B)cis-1-chloro-2-iodocyclohexane. Chloroiodocyclohexane was also identified in the cyclohexene-inhibited methylene chloride extract of a synthetic brine as well as the cyclohexene extract of a synthetic brine. Both the retention times and mass spectra were identical with those shown in Figures 3 and 4B,respectively. In other words, this particular compound was common to the cyclohexene-inhibited methylene chloride extract of the natural brine, the cyclohexene synthetic brine extract, and the cyclohexene-inhibited methylene chloride synthetic brine extract. Other components would probably have been found in all three extracts, but NaBr was not included in the synthetic brine, and the concentrations of the various salts vary from brine to brine. It should be noted that the total ion chromatogram of the cyclohexene-free methylene chloride extract of the synthetic brine sample showed no indication of any halogenated cyclohexanes. We have shown the existence of various halogenated cyclohexanes in a cyclohexene extract of a synthetic brine sample, cyclohexene-inhibited methylene chloride extract of an synthetic brine sample, and cyclohexene-inhibited methylene chloride extract of a brine sample. This is summarized in Table I. The cyclohexene is present in the methylene chloride (Burdick and Jackson),
